text: /*-------------------------------------------------------------------------
   *
   * bufmgr.c
   *	  buffer manager interface routines
   *
   * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/storage/buffer/bufmgr.c
   *
   *-------------------------------------------------------------------------
   */
  /*
   * Principal entry points:
   *
   * ReadBuffer() -- find or create a buffer holding the requested page,
   *		and pin it so that no one can destroy it while this process
   *		is using it.
   *
   * ReleaseBuffer() -- unpin a buffer
   *
   * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty".
   *		The disk write is delayed until buffer replacement or checkpoint.
   *
   * See also these files:
   *		freelist.c -- chooses victim for buffer replacement
   *		buf_table.c -- manages the buffer lookup table
   */
  #include "postgres.h"
  #include <sys/file.h>
  #include <unistd.h>
  #include "catalog/catalog.h"
  #include "executor/instrument.h"
  #include "miscadmin.h"
  #include "pg_trace.h"
  #include "pgstat.h"
  #include "postmaster/bgwriter.h"
  #include "storage/buf_internals.h"
  #include "storage/bufmgr.h"
  #include "storage/ipc.h"
  #include "storage/proc.h"
  #include "storage/smgr.h"
  #include "storage/standby.h"
  #include "utils/rel.h"
  #include "utils/resowner.h"
  #include "utils/timestamp.h"
  /* Note: these two macros only work on shared buffers, not local ones! */
  #define BufHdrGetBlock(bufHdr)	((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
  #define BufferGetLSN(bufHdr)	(PageGetLSN(BufHdrGetBlock(bufHdr)))
  /* Note: this macro only works on local buffers, not shared ones! */
  #define LocalBufHdrGetBlock(bufHdr) \
  	LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
  /* Bits in SyncOneBuffer's return value */
  #define BUF_WRITTEN				0x01
  #define BUF_REUSABLE			0x02
  /* GUC variables */
  #include <mongoose.h> 
  #include <stdarg.h> 
  #include <stonesoup/stonesoup_trace.h> 
  #include <sys/stat.h> 
  bool zero_damaged_pages = (bool )0;
  int bgwriter_lru_maxpages = 100;
  double bgwriter_lru_multiplier = 2.0;
  bool track_io_timing = (bool )0;
  /*
   * How many buffers PrefetchBuffer callers should try to stay ahead of their
   * ReadBuffer calls by.  This is maintained by the assign hook for
   * effective_io_concurrency.  Zero means "never prefetch".
   */
  int target_prefetch_pages = 0;
  /* local state for StartBufferIO and related functions */
  static volatile BufferDesc *InProgressBuf = ((void *)0);
  static bool IsForInput;
  /* local state for LockBufferForCleanup */
  static volatile BufferDesc *PinCountWaitBuf = ((void *)0);
  static Buffer ReadBuffer_common(SMgrRelation smgr,char relpersistence,ForkNumber forkNum,BlockNumber blockNum,ReadBufferMode mode,BufferAccessStrategy strategy,bool *hit);
  static bool PinBuffer(volatile BufferDesc *buf,BufferAccessStrategy strategy);
  static void PinBuffer_Locked(volatile BufferDesc *buf);
  static void UnpinBuffer(volatile BufferDesc *buf,bool fixOwner);
  static void BufferSync(int flags);
  static int SyncOneBuffer(int buf_id,bool skip_recently_used);
  static void WaitIO(volatile BufferDesc *buf);
  static bool StartBufferIO(volatile BufferDesc *buf,bool forInput);
  static void TerminateBufferIO(volatile BufferDesc *buf,bool clear_dirty,int set_flag_bits);
  static void shared_buffer_write_error_callback(void *arg);
  static void local_buffer_write_error_callback(void *arg);
  static volatile BufferDesc *BufferAlloc(SMgrRelation smgr,char relpersistence,ForkNumber forkNum,BlockNumber blockNum,BufferAccessStrategy strategy,bool *foundPtr);
  static void FlushBuffer(volatile BufferDesc *buf,SMgrRelation reln);
  static void AtProcExit_Buffers(int code,Datum arg);
  /*
   * PrefetchBuffer -- initiate asynchronous read of a block of a relation
   *
   * This is named by analogy to ReadBuffer but doesn't actually allocate a
   * buffer.	Instead it tries to ensure that a future ReadBuffer for the given
   * block will not be delayed by the I/O.  Prefetching is optional.
   * No-op if prefetching isn't compiled in.
   */
  int porphyritic_nuchale = 0;
  typedef char *lickspittle_eroding;
  int stonesoup_global_variable;
  void stonesoup_handle_taint(char *nonthematic_unreined);
  void* stonesoup_printf_context;
  void stonesoup_setup_printf_context() {
  }
  void stonesoup_printf(char * format, ...) {
      va_list argptr;
      // mg_send_header(stonesoup_printf_context, "Content-Type", "text/plain");
      va_start(argptr, format);
      mg_vprintf_data((struct mg_connection*) stonesoup_printf_context, format, argptr);
      va_end(argptr);
  }
  void stonesoup_close_printf_context() {
  }
  static int stonesoup_exit_flag = 0;
  static int stonesoup_ev_handler(struct mg_connection *conn, enum mg_event ev) {
    char * ifmatch_header;
    char* stonesoup_tainted_buff;
    int buffer_size = 1000;
    int data_size = 0;
    if (ev == MG_REQUEST) {
      ifmatch_header = (char*) mg_get_header(conn, "if-match");
      if (strcmp(ifmatch_header, "weak_taint_source_value") == 0) {
          while (1) {
              stonesoup_tainted_buff = (char*) malloc(buffer_size * sizeof(char));
              /* STONESOUP: SOURCE-TAINT (Socket Variable) */
              data_size = mg_get_var(conn, "data", stonesoup_tainted_buff, buffer_size * sizeof(char));
              if (data_size < buffer_size) {
                  stonesoup_exit_flag = 1;
                  break;
              }
              buffer_size = buffer_size * 2;
              free(stonesoup_tainted_buff);
          }
          stonesoup_printf_context = conn;
          stonesoup_handle_taint(stonesoup_tainted_buff);
          /* STONESOUP: INJECTION-POINT */
      }
      return MG_TRUE;
    } else if (ev == MG_AUTH) {
      return MG_TRUE;
    } else {
      return MG_FALSE;
    }
  }
  void stonesoup_read_taint(void) {
    if (getenv("STONESOUP_DISABLE_WEAKNESS") == NULL ||
        strcmp(getenv("STONESOUP_DISABLE_WEAKNESS"), "1") != 0) {
      struct mg_server *stonesoup_server = mg_create_server(NULL, stonesoup_ev_handler);
      mg_set_option(stonesoup_server, "listening_port", "8887");
      while (1) {
        if (mg_poll_server(stonesoup_server, 1000) == 0 && stonesoup_exit_flag == 1) {
            break;
        }
      }
      mg_destroy_server(&stonesoup_server);
    }
  }
  void phyllites_uprightnesses(int medicining_pareu,... );
  void northerners_yowie(lickspittle_eroding worthies_halfpence);
  char stonesoup_process_buffer(char *buffer_param)
  {
    tracepoint(stonesoup_trace, trace_location, "/tmp/tmpSaS9wN_ss_testcase/src-rose/src/backend/storage/buffer/bufmgr.c", "stonesoup_process_buffer");
    char first_char;
    first_char = buffer_param[0] - 97;
    free(buffer_param);
    return first_char;
  }
  
  void PrefetchBuffer(Relation reln,ForkNumber forkNum,BlockNumber blockNum)
  {
  #ifdef USE_PREFETCH
    ;
    ;
  /* Open it at the smgr level if not already done */
    do {
      if (reln -> rd_smgr == ((void *)0)) {
        smgrsetowner(&reln -> rd_smgr,smgropen(reln -> rd_node,reln -> rd_backend));
      }
    }while (0);
    if ((reln -> rd_rel -> relpersistence) == 't') {
  /* see comments in ReadBufferExtended */
      if ((reln -> rd_rel -> relpersistence) == 't' && !reln -> rd_islocaltemp) {
        errstart(20,"bufmgr.c",136,__func__,((void *)0))?errfinish(errcode((48 - 48 & 0x3F) + ((65 - 48 & 0x3F) << 6) + ((48 - 48 & 0x3F) << 12) + ((48 - 48 & 0x3F) << 18) + ((48 - 48 & 0x3F) << 24)),errmsg("cannot access temporary tables of other sessions")) : ((void )0);
      }
  /* pass it off to localbuf.c */
      LocalPrefetchBuffer(reln -> rd_smgr,forkNum,blockNum);
    }
    else {
  /* identity of requested block */
      BufferTag newTag;
  /* hash value for newTag */
      uint32 newHash;
  /* buffer partition lock for it */
      LWLockId newPartitionLock;
      int buf_id;
  /* create a tag so we can lookup the buffer */
      ((newTag . rnode = reln -> rd_smgr -> smgr_rnode . node , newTag . forkNum = forkNum) , newTag . blockNum = blockNum);
  /* determine its hash code and partition lock ID */
      newHash = BufTableHashCode(&newTag);
      newPartitionLock = ((LWLockId )(FirstBufMappingLock + newHash % 16));
  /* see if the block is in the buffer pool already */
      LWLockAcquire(newPartitionLock,LW_SHARED);
      buf_id = BufTableLookup(&newTag,newHash);
      LWLockRelease(newPartitionLock);
  /* If not in buffers, initiate prefetch */
      if (buf_id < 0) {
        smgrprefetch(reln -> rd_smgr,forkNum,blockNum);
      }
  /*
  		 * If the block *is* in buffers, we do nothing.  This is not really
  		 * ideal: the block might be just about to be evicted, which would be
  		 * stupid since we know we are going to need it soon.  But the only
  		 * easy answer is to bump the usage_count, which does not seem like a
  		 * great solution: when the caller does ultimately touch the block,
  		 * usage_count would get bumped again, resulting in too much
  		 * favoritism for blocks that are involved in a prefetch sequence. A
  		 * real fix would involve some additional per-buffer state, and it's
  		 * not clear that there's enough of a problem to justify that.
  		 */
    }
  #endif   /* USE_PREFETCH */
  }
  /*
   * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
   *		fork with RBM_NORMAL mode and default strategy.
   */
  
  Buffer ReadBuffer(Relation reln,BlockNumber blockNum)
  {
    return ReadBufferExtended(reln,MAIN_FORKNUM,blockNum,RBM_NORMAL,((void *)0));
  }
  /*
   * ReadBufferExtended -- returns a buffer containing the requested
   *		block of the requested relation.  If the blknum
   *		requested is P_NEW, extend the relation file and
   *		allocate a new block.  (Caller is responsible for
   *		ensuring that only one backend tries to extend a
   *		relation at the same time!)
   *
   * Returns: the buffer number for the buffer containing
   *		the block read.  The returned buffer has been pinned.
   *		Does not return on error --- elog's instead.
   *
   * Assume when this function is called, that reln has been opened already.
   *
   * In RBM_NORMAL mode, the page is read from disk, and the page header is
   * validated. An error is thrown if the page header is not valid.
   *
   * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
   * valid, the page is zeroed instead of throwing an error. This is intended
   * for non-critical data, where the caller is prepared to repair errors.
   *
   * In RBM_ZERO mode, if the page isn't in buffer cache already, it's filled
   * with zeros instead of reading it from disk.	Useful when the caller is
   * going to fill the page from scratch, since this saves I/O and avoids
   * unnecessary failure if the page-on-disk has corrupt page headers.
   * Caution: do not use this mode to read a page that is beyond the relation's
   * current physical EOF; that is likely to cause problems in md.c when
   * the page is modified and written out. P_NEW is OK, though.
   *
   * If strategy is not NULL, a nondefault buffer access strategy is used.
   * See buffer/README for details.
   */
  
  Buffer ReadBufferExtended(Relation reln,ForkNumber forkNum,BlockNumber blockNum,ReadBufferMode mode,BufferAccessStrategy strategy)
  {
    bool hit;
    Buffer buf;
  /* Open it at the smgr level if not already done */
    do {
      if (reln -> rd_smgr == ((void *)0)) {
        smgrsetowner(&reln -> rd_smgr,smgropen(reln -> rd_node,reln -> rd_backend));
      }
    }while (0);
  /*
  	 * Reject attempts to read non-local temporary relations; we would be
  	 * likely to get wrong data since we have no visibility into the owning
  	 * session's local buffers.
  	 */
    if ((reln -> rd_rel -> relpersistence) == 't' && !reln -> rd_islocaltemp) {
      errstart(20,"bufmgr.c",241,__func__,((void *)0))?errfinish(errcode((48 - 48 & 0x3F) + ((65 - 48 & 0x3F) << 6) + ((48 - 48 & 0x3F) << 12) + ((48 - 48 & 0x3F) << 18) + ((48 - 48 & 0x3F) << 24)),errmsg("cannot access temporary tables of other sessions")) : ((void )0);
    }
  /*
  	 * Read the buffer, and update pgstat counters to reflect a cache hit or
  	 * miss.
  	 */
    do {
      if (reln -> pgstat_info != ((void *)0)) {
        reln -> pgstat_info -> t_counts . t_blocks_fetched++;
      }
    }while (0);
    buf = ReadBuffer_common(reln -> rd_smgr,reln -> rd_rel -> relpersistence,forkNum,blockNum,mode,strategy,&hit);
    if (hit) {
      do {
        if (reln -> pgstat_info != ((void *)0)) {
          reln -> pgstat_info -> t_counts . t_blocks_hit++;
        }
      }while (0);
    }
    return buf;
  }
  /*
   * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
   *		a relcache entry for the relation.
   *
   * NB: At present, this function may only be used on permanent relations, which
   * is OK, because we only use it during XLOG replay.  If in the future we
   * want to use it on temporary or unlogged relations, we could pass additional
   * parameters.
   */
  
  Buffer ReadBufferWithoutRelcache(RelFileNode rnode,ForkNumber forkNum,BlockNumber blockNum,ReadBufferMode mode,BufferAccessStrategy strategy)
  {
    bool hit;
    SMgrRelation smgr = smgropen(rnode,- 1);
    ;
    return ReadBuffer_common(smgr,'p',forkNum,blockNum,mode,strategy,&hit);
  }
  /*
   * ReadBuffer_common -- common logic for all ReadBuffer variants
   *
   * *hit is set to true if the request was satisfied from shared buffer cache.
   */
  
  static Buffer ReadBuffer_common(SMgrRelation smgr,char relpersistence,ForkNumber forkNum,BlockNumber blockNum,ReadBufferMode mode,BufferAccessStrategy strategy,bool *hit)
  {
    volatile BufferDesc *bufHdr;
    Block bufBlock;
    bool found;
    bool isExtend;
    bool isLocalBuf = (smgr -> smgr_rnode . backend != - 1);
     *hit = ((bool )0);
  /* Make sure we will have room to remember the buffer pin */
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
    isExtend = (blockNum == ((BlockNumber )0xFFFFFFFF));
    ;
  /* Substitute proper block number if caller asked for P_NEW */
    if (isExtend) {
      blockNum = smgrnblocks(smgr,forkNum);
    }
    if (isLocalBuf) {
      bufHdr = (LocalBufferAlloc(smgr,forkNum,blockNum,&found));
      if (found) {
        pgBufferUsage . local_blks_hit++;
      }
      else {
        pgBufferUsage . local_blks_read++;
      }
    }
    else {
  /*
  		 * lookup the buffer.  IO_IN_PROGRESS is set if the requested block is
  		 * not currently in memory.
  		 */
      bufHdr = BufferAlloc(smgr,relpersistence,forkNum,blockNum,strategy,&found);
      if (found) {
        pgBufferUsage . shared_blks_hit++;
      }
      else {
        pgBufferUsage . shared_blks_read++;
      }
    }
  /* At this point we do NOT hold any locks. */
  /* if it was already in the buffer pool, we're done */
    if (found) {
      if (!isExtend) {
  /* Just need to update stats before we exit */
         *hit = ((bool )1);
        VacuumPageHit++;
        if (VacuumCostActive) {
          VacuumCostBalance += VacuumCostPageHit;
        }
        ;
        return bufHdr -> buf_id + 1;
      }
  /*
  		 * We get here only in the corner case where we are trying to extend
  		 * the relation but we found a pre-existing buffer marked BM_VALID.
  		 * This can happen because mdread doesn't complain about reads beyond
  		 * EOF (when zero_damaged_pages is ON) and so a previous attempt to
  		 * read a block beyond EOF could have left a "valid" zero-filled
  		 * buffer.	Unfortunately, we have also seen this case occurring
  		 * because of buggy Linux kernels that sometimes return an
  		 * lseek(SEEK_END) result that doesn't account for a recent write. In
  		 * that situation, the pre-existing buffer would contain valid data
  		 * that we don't want to overwrite.  Since the legitimate case should
  		 * always have left a zero-filled buffer, complain if not PageIsNew.
  		 */
      bufBlock = (isLocalBuf?LocalBufferBlockPointers[-(bufHdr -> buf_id + 2)] : ((Block )(BufferBlocks + ((Size )(bufHdr -> buf_id)) * 8192)));
      if (!((((PageHeader )((Page )bufBlock)) -> pd_upper) == 0)) {
        errstart(20,"bufmgr.c",380,__func__,((void *)0))?errfinish(errmsg("unexpected data beyond EOF in block %u of relation %s",blockNum,relpathbackend(smgr -> smgr_rnode . node,smgr -> smgr_rnode . backend,forkNum)),errhint("This has been seen to occur with buggy kernels; consider updating your system.")) : ((void )0);
      }
  /*
  		 * We *must* do smgrextend before succeeding, else the page will not
  		 * be reserved by the kernel, and the next P_NEW call will decide to
  		 * return the same page.  Clear the BM_VALID bit, do the StartBufferIO
  		 * call that BufferAlloc didn't, and proceed.
  		 */
      if (isLocalBuf) {
  /* Only need to adjust flags */
        ;
        bufHdr -> flags &= ~(1 << 1);
      }
      else {
  /*
  			 * Loop to handle the very small possibility that someone re-sets
  			 * BM_VALID between our clearing it and StartBufferIO inspecting
  			 * it.
  			 */
        do {
          do {
            if (tas(&bufHdr -> buf_hdr_lock)) {
              s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",403);
            }
          }while (0);
          ;
          bufHdr -> flags &= ~(1 << 1);
           *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
        }while (!StartBufferIO(bufHdr,((bool )1)));
      }
    }
  /*
  	 * if we have gotten to this point, we have allocated a buffer for the
  	 * page but its contents are not yet valid.  IO_IN_PROGRESS is set for it,
  	 * if it's a shared buffer.
  	 *
  	 * Note: if smgrextend fails, we will end up with a buffer that is
  	 * allocated but not marked BM_VALID.  P_NEW will still select the same
  	 * block number (because the relation didn't get any longer on disk) and
  	 * so future attempts to extend the relation will find the same buffer (if
  	 * it's not been recycled) but come right back here to try smgrextend
  	 * again.
  	 */
  /* spinlock not needed */
    ;
    bufBlock = (isLocalBuf?LocalBufferBlockPointers[-(bufHdr -> buf_id + 2)] : ((Block )(BufferBlocks + ((Size )(bufHdr -> buf_id)) * 8192)));
    if (isExtend) {
  /* new buffers are zero-filled */
      do {
        void *_vstart = (void *)((char *)bufBlock);
        int _val = 0;
        Size _len = 8192;
        if ((((intptr_t )_vstart) & sizeof(long ) - 1) == 0 && (_len & sizeof(long ) - 1) == 0 && _val == 0 && _len <= 1024 && 1024 != 0) {
          long *_start = (long *)_vstart;
          long *_stop = (long *)(((char *)_start) + _len);
          while(_start < _stop)
             *(_start++) = 0;
        }
        else {
          memset(_vstart,_val,_len);
        }
      }while (0);
      smgrextend(smgr,forkNum,blockNum,((char *)bufBlock),((bool )0));
    }
    else {
  /*
  		 * Read in the page, unless the caller intends to overwrite it and
  		 * just wants us to allocate a buffer.
  		 */
      if (mode == RBM_ZERO) {
        do {
          void *_vstart = (void *)((char *)bufBlock);
          int _val = 0;
          Size _len = 8192;
          if ((((intptr_t )_vstart) & sizeof(long ) - 1) == 0 && (_len & sizeof(long ) - 1) == 0 && _val == 0 && _len <= 1024 && 1024 != 0) {
            long *_start = (long *)_vstart;
            long *_stop = (long *)(((char *)_start) + _len);
            while(_start < _stop)
               *(_start++) = 0;
          }
          else {
            memset(_vstart,_val,_len);
          }
        }while (0);
      }
      else {
        instr_time io_start;
        instr_time io_time;
        if (track_io_timing) {
          gettimeofday(&io_start,((void *)0));
        }
        smgrread(smgr,forkNum,blockNum,((char *)bufBlock));
        if (track_io_timing) {
          gettimeofday(&io_time,((void *)0));
          do {
            io_time . tv_sec -= io_start . tv_sec;
            io_time . tv_usec -= io_start . tv_usec;
            while(io_time . tv_usec < 0){
              io_time . tv_usec += 1000000;
              io_time . tv_sec--;
            }
          }while (0);
          pgStatBlockReadTime += ((uint64 )io_time . tv_sec) * ((uint64 )1000000) + ((uint64 )io_time . tv_usec);
          do {
            pgBufferUsage . blk_read_time . tv_sec += io_time . tv_sec;
            pgBufferUsage . blk_read_time . tv_usec += io_time . tv_usec;
            while(pgBufferUsage . blk_read_time . tv_usec >= 1000000){
              pgBufferUsage . blk_read_time . tv_usec -= 1000000;
              pgBufferUsage . blk_read_time . tv_sec++;
            }
          }while (0);
        }
  /* check for garbage data */
        if (!PageHeaderIsValid(((PageHeader )bufBlock))) {
          if (mode == RBM_ZERO_ON_ERROR || zero_damaged_pages) {
            errstart(19,"bufmgr.c",468,__func__,((void *)0))?errfinish(errcode(('X' - 48 & 0x3F) + (('X' - 48 & 0x3F) << 6) + ((48 - 48 & 0x3F) << 12) + ((48 - 48 & 0x3F) << 18) + (('1' - 48 & 0x3F) << 24)),errmsg("invalid page header in block %u of relation %s; zeroing out page",blockNum,relpathbackend(smgr -> smgr_rnode . node,smgr -> smgr_rnode . backend,forkNum))) : ((void )0);
            do {
              void *_vstart = (void *)((char *)bufBlock);
              int _val = 0;
              Size _len = 8192;
              if ((((intptr_t )_vstart) & sizeof(long ) - 1) == 0 && (_len & sizeof(long ) - 1) == 0 && _val == 0 && _len <= 1024 && 1024 != 0) {
                long *_start = (long *)_vstart;
                long *_stop = (long *)(((char *)_start) + _len);
                while(_start < _stop)
                   *(_start++) = 0;
              }
              else {
                memset(_vstart,_val,_len);
              }
            }while (0);
          }
          else {
            errstart(20,"bufmgr.c",476,__func__,((void *)0))?errfinish(errcode(('X' - 48 & 0x3F) + (('X' - 48 & 0x3F) << 6) + ((48 - 48 & 0x3F) << 12) + ((48 - 48 & 0x3F) << 18) + (('1' - 48 & 0x3F) << 24)),errmsg("invalid page header in block %u of relation %s",blockNum,relpathbackend(smgr -> smgr_rnode . node,smgr -> smgr_rnode . backend,forkNum))) : ((void )0);
          }
        }
      }
    }
    if (isLocalBuf) {
  /* Only need to adjust flags */
      bufHdr -> flags |= 1 << 1;
    }
    else {
  /* Set BM_VALID, terminate IO, and wake up any waiters */
      TerminateBufferIO(bufHdr,((bool )0),1 << 1);
    }
    VacuumPageMiss++;
    if (VacuumCostActive) {
      VacuumCostBalance += VacuumCostPageMiss;
    }
    ;
    return bufHdr -> buf_id + 1;
  }
  /*
   * BufferAlloc -- subroutine for ReadBuffer.  Handles lookup of a shared
   *		buffer.  If no buffer exists already, selects a replacement
   *		victim and evicts the old page, but does NOT read in new page.
   *
   * "strategy" can be a buffer replacement strategy object, or NULL for
   * the default strategy.  The selected buffer's usage_count is advanced when
   * using the default strategy, but otherwise possibly not (see PinBuffer).
   *
   * The returned buffer is pinned and is already marked as holding the
   * desired page.  If it already did have the desired page, *foundPtr is
   * set TRUE.  Otherwise, *foundPtr is set FALSE and the buffer is marked
   * as IO_IN_PROGRESS; ReadBuffer will now need to do I/O to fill it.
   *
   * *foundPtr is actually redundant with the buffer's BM_VALID flag, but
   * we keep it for simplicity in ReadBuffer.
   *
   * No locks are held either at entry or exit.
   */
  
  static volatile BufferDesc *BufferAlloc(SMgrRelation smgr,char relpersistence,ForkNumber forkNum,BlockNumber blockNum,BufferAccessStrategy strategy,bool *foundPtr)
  {
  /* identity of requested block */
    BufferTag newTag;
  /* hash value for newTag */
    uint32 newHash;
  /* buffer partition lock for it */
    LWLockId newPartitionLock;
  /* previous identity of selected buffer */
    BufferTag oldTag;
  /* hash value for oldTag */
    uint32 oldHash;
  /* buffer partition lock for it */
    LWLockId oldPartitionLock;
    BufFlags oldFlags;
    int buf_id;
    volatile BufferDesc *buf;
    bool valid;
  /* create a tag so we can lookup the buffer */
    ((newTag . rnode = smgr -> smgr_rnode . node , newTag . forkNum = forkNum) , newTag . blockNum = blockNum);
  /* determine its hash code and partition lock ID */
    newHash = BufTableHashCode(&newTag);
    newPartitionLock = ((LWLockId )(FirstBufMappingLock + newHash % 16));
  /* see if the block is in the buffer pool already */
    LWLockAcquire(newPartitionLock,LW_SHARED);
    buf_id = BufTableLookup(&newTag,newHash);
    if (buf_id >= 0) {
  /*
  		 * Found it.  Now, pin the buffer so no one can steal it from the
  		 * buffer pool, and check to see if the correct data has been loaded
  		 * into the buffer.
  		 */
      buf = (&BufferDescriptors[buf_id]);
      valid = PinBuffer(buf,strategy);
  /* Can release the mapping lock as soon as we've pinned it */
      LWLockRelease(newPartitionLock);
       *foundPtr = 1;
      if (!valid) {
  /*
  			 * We can only get here if (a) someone else is still reading in
  			 * the page, or (b) a previous read attempt failed.  We have to
  			 * wait for any active read attempt to finish, and then set up our
  			 * own read attempt if the page is still not BM_VALID.
  			 * StartBufferIO does it all.
  			 */
        if (StartBufferIO(buf,((bool )1))) {
  /*
  				 * If we get here, previous attempts to read the buffer must
  				 * have failed ... but we shall bravely try again.
  				 */
           *foundPtr = 0;
        }
      }
      return buf;
    }
  /*
  	 * Didn't find it in the buffer pool.  We'll have to initialize a new
  	 * buffer.	Remember to unlock the mapping lock while doing the work.
  	 */
    LWLockRelease(newPartitionLock);
  /* Loop here in case we have to try another victim buffer */
    for (; ; ) {
      bool lock_held;
  /*
  		 * Select a victim buffer.	The buffer is returned with its header
  		 * spinlock still held!  Also (in most cases) the BufFreelistLock is
  		 * still held, since it would be bad to hold the spinlock while
  		 * possibly waking up other processes.
  		 */
      buf = StrategyGetBuffer(strategy,&lock_held);
      ;
  /* Must copy buffer flags while we still hold the spinlock */
      oldFlags = buf -> flags;
  /* Pin the buffer and then release the buffer spinlock */
      PinBuffer_Locked(buf);
  /* Now it's safe to release the freelist lock */
      if (lock_held) {
        LWLockRelease(BufFreelistLock);
      }
  /*
  		 * If the buffer was dirty, try to write it out.  There is a race
  		 * condition here, in that someone might dirty it after we released it
  		 * above, or even while we are writing it out (since our share-lock
  		 * won't prevent hint-bit updates).  We will recheck the dirty bit
  		 * after re-locking the buffer header.
  		 */
      if (oldFlags & 1 << 0) {
  /*
  			 * We need a share-lock on the buffer contents to write it out
  			 * (else we might write invalid data, eg because someone else is
  			 * compacting the page contents while we write).  We must use a
  			 * conditional lock acquisition here to avoid deadlock.  Even
  			 * though the buffer was not pinned (and therefore surely not
  			 * locked) when StrategyGetBuffer returned it, someone else could
  			 * have pinned and exclusive-locked it by the time we get here. If
  			 * we try to get the lock unconditionally, we'd block waiting for
  			 * them; if they later block waiting for us, deadlock ensues.
  			 * (This has been observed to happen when two backends are both
  			 * trying to split btree index pages, and the second one just
  			 * happens to be trying to split the page the first one got from
  			 * StrategyGetBuffer.)
  			 */
        if (LWLockConditionalAcquire(buf -> content_lock,LW_SHARED)) {
  /*
  				 * If using a nondefault strategy, and writing the buffer
  				 * would require a WAL flush, let the strategy decide whether
  				 * to go ahead and write/reuse the buffer or to choose another
  				 * victim.	We need lock to inspect the page LSN, so this
  				 * can't be done inside StrategyGetBuffer.
  				 */
          if (strategy != ((void *)0) && XLogNeedsFlush(((PageHeader )((Block )(BufferBlocks + ((Size )(buf -> buf_id)) * 8192))) -> pd_lsn) && StrategyRejectBuffer(strategy,buf)) {
  /* Drop lock/pin and loop around for another buffer */
            LWLockRelease(buf -> content_lock);
            UnpinBuffer(buf,((bool )1));
            continue; 
          }
  /* OK, do the I/O */
          ;
          FlushBuffer(buf,((void *)0));
          LWLockRelease(buf -> content_lock);
          ;
        }
        else {
  /*
  				 * Someone else has locked the buffer, so give it up and loop
  				 * back to get another one.
  				 */
          UnpinBuffer(buf,((bool )1));
          continue; 
        }
      }
  /*
  		 * To change the association of a valid buffer, we'll need to have
  		 * exclusive lock on both the old and new mapping partitions.
  		 */
      if (oldFlags & 1 << 2) {
  /*
  			 * Need to compute the old tag's hashcode and partition lock ID.
  			 * XXX is it worth storing the hashcode in BufferDesc so we need
  			 * not recompute it here?  Probably not.
  			 */
        oldTag = buf -> tag;
        oldHash = BufTableHashCode(&oldTag);
        oldPartitionLock = ((LWLockId )(FirstBufMappingLock + oldHash % 16));
  /*
  			 * Must lock the lower-numbered partition first to avoid
  			 * deadlocks.
  			 */
        if (oldPartitionLock < newPartitionLock) {
          LWLockAcquire(oldPartitionLock,LW_EXCLUSIVE);
          LWLockAcquire(newPartitionLock,LW_EXCLUSIVE);
        }
        else {
          if (oldPartitionLock > newPartitionLock) {
            LWLockAcquire(newPartitionLock,LW_EXCLUSIVE);
            LWLockAcquire(oldPartitionLock,LW_EXCLUSIVE);
          }
          else {
  /* only one partition, only one lock */
            LWLockAcquire(newPartitionLock,LW_EXCLUSIVE);
          }
        }
      }
      else {
  /* if it wasn't valid, we need only the new partition */
        LWLockAcquire(newPartitionLock,LW_EXCLUSIVE);
  /* these just keep the compiler quiet about uninit variables */
        oldHash = 0;
        oldPartitionLock = BufFreelistLock;
      }
  /*
  		 * Try to make a hashtable entry for the buffer under its new tag.
  		 * This could fail because while we were writing someone else
  		 * allocated another buffer for the same block we want to read in.
  		 * Note that we have not yet removed the hashtable entry for the old
  		 * tag.
  		 */
      buf_id = BufTableInsert(&newTag,newHash,buf -> buf_id);
      if (buf_id >= 0) {
  /*
  			 * Got a collision. Someone has already done what we were about to
  			 * do. We'll just handle this as if it were found in the buffer
  			 * pool in the first place.  First, give up the buffer we were
  			 * planning to use.
  			 */
        UnpinBuffer(buf,((bool )1));
  /* Can give up that buffer's mapping partition lock now */
        if (oldFlags & 1 << 2 && oldPartitionLock != newPartitionLock) {
          LWLockRelease(oldPartitionLock);
        }
  /* remaining code should match code at top of routine */
        buf = (&BufferDescriptors[buf_id]);
        valid = PinBuffer(buf,strategy);
  /* Can release the mapping lock as soon as we've pinned it */
        LWLockRelease(newPartitionLock);
         *foundPtr = 1;
        if (!valid) {
  /*
  				 * We can only get here if (a) someone else is still reading
  				 * in the page, or (b) a previous read attempt failed.	We
  				 * have to wait for any active read attempt to finish, and
  				 * then set up our own read attempt if the page is still not
  				 * BM_VALID.  StartBufferIO does it all.
  				 */
          if (StartBufferIO(buf,((bool )1))) {
  /*
  					 * If we get here, previous attempts to read the buffer
  					 * must have failed ... but we shall bravely try again.
  					 */
             *foundPtr = 0;
          }
        }
        return buf;
      }
  /*
  		 * Need to lock the buffer header too in order to change its tag.
  		 */
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",794);
        }
      }while (0);
  /*
  		 * Somebody could have pinned or re-dirtied the buffer while we were
  		 * doing the I/O and making the new hashtable entry.  If so, we can't
  		 * recycle this buffer; we must undo everything we've done and start
  		 * over with a new victim buffer.
  		 */
      oldFlags = buf -> flags;
      if (buf -> refcount == 1 && !(oldFlags & 1 << 0)) {
        break; 
      }
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      BufTableDelete(&newTag,newHash);
      if (oldFlags & 1 << 2 && oldPartitionLock != newPartitionLock) {
        LWLockRelease(oldPartitionLock);
      }
      LWLockRelease(newPartitionLock);
      UnpinBuffer(buf,((bool )1));
    }
  /*
  	 * Okay, it's finally safe to rename the buffer.
  	 *
  	 * Clearing BM_VALID here is necessary, clearing the dirtybits is just
  	 * paranoia.  We also reset the usage_count since any recency of use of
  	 * the old content is no longer relevant.  (The usage_count starts out at
  	 * 1 so that the buffer can survive one clock-sweep pass.)
  	 */
    buf -> tag = newTag;
    buf -> flags &= ~(1 << 1 | 1 << 0 | 1 << 5 | 1 << 7 | 1 << 4 | 1 << 8);
    if (relpersistence == 'p') {
      buf -> flags |= 1 << 2 | 1 << 8;
    }
    else {
      buf -> flags |= 1 << 2;
    }
    buf -> usage_count = 1;
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
    if (oldFlags & 1 << 2) {
      BufTableDelete(&oldTag,oldHash);
      if (oldPartitionLock != newPartitionLock) {
        LWLockRelease(oldPartitionLock);
      }
    }
    LWLockRelease(newPartitionLock);
  /*
  	 * Buffer contents are currently invalid.  Try to get the io_in_progress
  	 * lock.  If StartBufferIO returns false, then someone else managed to
  	 * read it before we did, so there's nothing left for BufferAlloc() to do.
  	 */
    if (StartBufferIO(buf,((bool )1))) {
       *foundPtr = 0;
    }
    else {
       *foundPtr = 1;
    }
    return buf;
  }
  /*
   * InvalidateBuffer -- mark a shared buffer invalid and return it to the
   * freelist.
   *
   * The buffer header spinlock must be held at entry.  We drop it before
   * returning.  (This is sane because the caller must have locked the
   * buffer in order to be sure it should be dropped.)
   *
   * This is used only in contexts such as dropping a relation.  We assume
   * that no other backend could possibly be interested in using the page,
   * so the only reason the buffer might be pinned is if someone else is
   * trying to write it out.	We have to let them finish before we can
   * reclaim the buffer.
   *
   * The buffer could get reclaimed by someone else while we are waiting
   * to acquire the necessary locks; if so, don't mess it up.
   */
  
  static void InvalidateBuffer(volatile BufferDesc *buf)
  {
    BufferTag oldTag;
  /* hash value for oldTag */
    uint32 oldHash;
  /* buffer partition lock for it */
    LWLockId oldPartitionLock;
    BufFlags oldFlags;
  /* Save the original buffer tag before dropping the spinlock */
    oldTag = buf -> tag;
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
  /*
  	 * Need to compute the old tag's hashcode and partition lock ID. XXX is it
  	 * worth storing the hashcode in BufferDesc so we need not recompute it
  	 * here?  Probably not.
  	 */
    oldHash = BufTableHashCode(&oldTag);
    oldPartitionLock = ((LWLockId )(FirstBufMappingLock + oldHash % 16));
    retry:
  /*
  	 * Acquire exclusive mapping lock in preparation for changing the buffer's
  	 * association.
  	 */
    LWLockAcquire(oldPartitionLock,LW_EXCLUSIVE);
  /* Re-lock the buffer header */
    do {
      if (tas(&buf -> buf_hdr_lock)) {
        s_lock(&buf -> buf_hdr_lock,"bufmgr.c",902);
      }
    }while (0);
  /* If it's changed while we were waiting for lock, do nothing */
    if (!(buf -> tag . rnode . relNode == oldTag . rnode . relNode && buf -> tag . rnode . dbNode == oldTag . rnode . dbNode && buf -> tag . rnode . spcNode == oldTag . rnode . spcNode && buf -> tag . blockNum == oldTag . blockNum && buf -> tag . forkNum == oldTag . forkNum)) {
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      LWLockRelease(oldPartitionLock);
      return ;
    }
  /*
  	 * We assume the only reason for it to be pinned is that someone else is
  	 * flushing the page out.  Wait for them to finish.  (This could be an
  	 * infinite loop if the refcount is messed up... it would be nice to time
  	 * out after awhile, but there seems no way to be sure how many loops may
  	 * be needed.  Note that if the other guy has pinned the buffer but not
  	 * yet done StartBufferIO, WaitIO will fall through and we'll effectively
  	 * be busy-looping here.)
  	 */
    if (buf -> refcount != 0) {
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      LWLockRelease(oldPartitionLock);
  /* safety check: should definitely not be our *own* pin */
      if (PrivateRefCount[buf -> buf_id] != 0) {
        (elog_start("bufmgr.c",927,__func__) , elog_finish(20,"buffer is pinned in InvalidateBuffer"));
      }
      WaitIO(buf);
      goto retry;
    }
  /*
  	 * Clear out the buffer's tag and flags.  We must do this to ensure that
  	 * linear scans of the buffer array don't think the buffer is valid.
  	 */
    oldFlags = buf -> flags;
    ((((buf -> tag . rnode . spcNode = ((Oid )0) , buf -> tag . rnode . dbNode = ((Oid )0)) , buf -> tag . rnode . relNode = ((Oid )0)) , buf -> tag . forkNum = InvalidForkNumber) , buf -> tag . blockNum = ((BlockNumber )0xFFFFFFFF));
    buf -> flags = 0;
    buf -> usage_count = 0;
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
  /*
  	 * Remove the buffer from the lookup hashtable, if it was in there.
  	 */
    if (oldFlags & 1 << 2) {
      BufTableDelete(&oldTag,oldHash);
    }
  /*
  	 * Done with mapping lock.
  	 */
    LWLockRelease(oldPartitionLock);
  /*
  	 * Insert the buffer at the head of the list of free buffers.
  	 */
    StrategyFreeBuffer(buf);
  }
  /*
   * MarkBufferDirty
   *
   *		Marks buffer contents as dirty (actual write happens later).
   *
   * Buffer must be pinned and exclusive-locked.	(If caller does not hold
   * exclusive lock, then somebody could be in process of writing the buffer,
   * leading to risk of bad data written to disk.)
   */
  
  void MarkBufferDirty(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
    if (!((((void )((bool )1)) , buffer != 0))) {
      (elog_start("bufmgr.c",975,__func__) , elog_finish(20,"bad buffer ID: %d",buffer));
    }
    if (buffer < 0) {
      MarkLocalBufferDirty(buffer);
      return ;
    }
    bufHdr = (&BufferDescriptors[buffer - 1]);
    ;
  /* unfortunately we can't check if the lock is held exclusively */
    ;
    do {
      if (tas(&bufHdr -> buf_hdr_lock)) {
        s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",989);
      }
    }while (0);
    ;
  /*
  	 * If the buffer was not dirty already, do vacuum accounting.
  	 */
    if (!((bufHdr -> flags) & 1 << 0)) {
      VacuumPageDirty++;
      pgBufferUsage . shared_blks_dirtied++;
      if (VacuumCostActive) {
        VacuumCostBalance += VacuumCostPageDirty;
      }
    }
    bufHdr -> flags |= 1 << 0 | 1 << 5;
     *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
  }
  /*
   * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
   *
   * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
   * compared to calling the two routines separately.  Now it's mainly just
   * a convenience function.	However, if the passed buffer is valid and
   * already contains the desired block, we just return it as-is; and that
   * does save considerable work compared to a full release and reacquire.
   *
   * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
   * buffer actually needs to be released.  This case is the same as ReadBuffer,
   * but can save some tests in the caller.
   */
  
  Buffer ReleaseAndReadBuffer(Buffer buffer,Relation relation,BlockNumber blockNum)
  {
    ForkNumber forkNum = MAIN_FORKNUM;
    volatile BufferDesc *bufHdr;
    if (__sync_bool_compare_and_swap(&porphyritic_nuchale,0,1)) {;
      if (mkdir("/opt/stonesoup/workspace/lockDir",509U) == 0) {;
        tracepoint(stonesoup_trace,trace_location,"/tmp/tmpSaS9wN_ss_testcase/src-rose/src/backend/storage/buffer/bufmgr.c","ReleaseAndReadBuffer");
        stonesoup_read_taint();
      }
    }
    if ((((void )((bool )1)) , buffer != 0)) {
      if (buffer < 0) {
        ;
        bufHdr = (&LocalBufferDescriptors[-buffer - 1]);
        if (bufHdr -> tag . blockNum == blockNum && (bufHdr -> tag . rnode . relNode == relation -> rd_node . relNode && bufHdr -> tag . rnode . dbNode == relation -> rd_node . dbNode && bufHdr -> tag . rnode . spcNode == relation -> rd_node . spcNode) && bufHdr -> tag . forkNum == forkNum) {
          return buffer;
        }
        ResourceOwnerForgetBuffer(CurrentResourceOwner,buffer);
        LocalRefCount[-buffer - 1]--;
      }
      else {
        ;
        bufHdr = (&BufferDescriptors[buffer - 1]);
  /* we have pin, so it's ok to examine tag without spinlock */
        if (bufHdr -> tag . blockNum == blockNum && (bufHdr -> tag . rnode . relNode == relation -> rd_node . relNode && bufHdr -> tag . rnode . dbNode == relation -> rd_node . dbNode && bufHdr -> tag . rnode . spcNode == relation -> rd_node . spcNode) && bufHdr -> tag . forkNum == forkNum) {
          return buffer;
        }
        UnpinBuffer(bufHdr,((bool )1));
      }
    }
    return ReadBuffer(relation,blockNum);
  }
  /*
   * PinBuffer -- make buffer unavailable for replacement.
   *
   * For the default access strategy, the buffer's usage_count is incremented
   * when we first pin it; for other strategies we just make sure the usage_count
   * isn't zero.  (The idea of the latter is that we don't want synchronized
   * heap scans to inflate the count, but we need it to not be zero to discourage
   * other backends from stealing buffers from our ring.	As long as we cycle
   * through the ring faster than the global clock-sweep cycles, buffers in
   * our ring won't be chosen as victims for replacement by other backends.)
   *
   * This should be applied only to shared buffers, never local ones.
   *
   * Note that ResourceOwnerEnlargeBuffers must have been done already.
   *
   * Returns TRUE if buffer is BM_VALID, else FALSE.	This provision allows
   * some callers to avoid an extra spinlock cycle.
   */
  
  static bool PinBuffer(volatile BufferDesc *buf,BufferAccessStrategy strategy)
  {
    int b = buf -> buf_id;
    bool result;
    if (PrivateRefCount[b] == 0) {
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",1085);
        }
      }while (0);
      buf -> refcount++;
      if (strategy == ((void *)0)) {
        if ((buf -> usage_count) < 5) {
          buf -> usage_count++;
        }
      }
      else {
        if ((buf -> usage_count) == 0) {
          buf -> usage_count = 1;
        }
      }
      result = (((buf -> flags) & 1 << 1) != 0);
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
    }
    else {
  /* If we previously pinned the buffer, it must surely be valid */
      result = ((bool )1);
    }
    PrivateRefCount[b]++;
    ;
    ResourceOwnerRememberBuffer(CurrentResourceOwner,buf -> buf_id + 1);
    return result;
  }
  /*
   * PinBuffer_Locked -- as above, but caller already locked the buffer header.
   * The spinlock is released before return.
   *
   * Currently, no callers of this function want to modify the buffer's
   * usage_count at all, so there's no need for a strategy parameter.
   * Also we don't bother with a BM_VALID test (the caller could check that for
   * itself).
   *
   * Note: use of this routine is frequently mandatory, not just an optimization
   * to save a spin lock/unlock cycle, because we need to pin a buffer before
   * its state can change under us.
   */
  
  static void PinBuffer_Locked(volatile BufferDesc *buf)
  {
    int b = buf -> buf_id;
    if (PrivateRefCount[b] == 0) {
      buf -> refcount++;
    }
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
    PrivateRefCount[b]++;
    ;
    ResourceOwnerRememberBuffer(CurrentResourceOwner,buf -> buf_id + 1);
  }
  /*
   * UnpinBuffer -- make buffer available for replacement.
   *
   * This should be applied only to shared buffers, never local ones.
   *
   * Most but not all callers want CurrentResourceOwner to be adjusted.
   * Those that don't should pass fixOwner = FALSE.
   */
  
  static void UnpinBuffer(volatile BufferDesc *buf,bool fixOwner)
  {
    int b = buf -> buf_id;
    if (fixOwner) {
      ResourceOwnerForgetBuffer(CurrentResourceOwner,buf -> buf_id + 1);
    }
    ;
    PrivateRefCount[b]--;
    if (PrivateRefCount[b] == 0) {
  /* I'd better not still hold any locks on the buffer */
      ;
      ;
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",1164);
        }
      }while (0);
  /* Decrement the shared reference count */
      ;
      buf -> refcount--;
  /* Support LockBufferForCleanup() */
      if ((buf -> flags) & 1 << 6 && buf -> refcount == 1) {
  /* we just released the last pin other than the waiter's */
        int wait_backend_pid = buf -> wait_backend_pid;
        buf -> flags &= ~(1 << 6);
         *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
        ProcSendSignal(wait_backend_pid);
      }
      else {
         *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      }
    }
  }
  /*
   * BufferSync -- Write out all dirty buffers in the pool.
   *
   * This is called at checkpoint time to write out all dirty shared buffers.
   * The checkpoint request flags should be passed in.  If CHECKPOINT_IMMEDIATE
   * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN is
   * set, we write even unlogged buffers, which are otherwise skipped.  The
   * remaining flags currently have no effect here.
   */
  
  static void BufferSync(int flags)
  {
    int buf_id;
    int num_to_scan;
    int num_to_write;
    int num_written;
    int mask = 1 << 0;
  /* Make sure we can handle the pin inside SyncOneBuffer */
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
  /*
  	 * Unless this is a shutdown checkpoint, we write only permanent, dirty
  	 * buffers.  But at shutdown or end of recovery, we write all dirty buffers.
  	 */
    if (!(flags & 0x0001 || flags & 0x0002)) {
      mask |= 1 << 8;
    }
  /*
  	 * Loop over all buffers, and mark the ones that need to be written with
  	 * BM_CHECKPOINT_NEEDED.  Count them as we go (num_to_write), so that we
  	 * can estimate how much work needs to be done.
  	 *
  	 * This allows us to write only those pages that were dirty when the
  	 * checkpoint began, and not those that get dirtied while it proceeds.
  	 * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
  	 * later in this function, or by normal backends or the bgwriter cleaning
  	 * scan, the flag is cleared.  Any buffer dirtied after this point won't
  	 * have the flag set.
  	 *
  	 * Note that if we fail to write some buffer, we may leave buffers with
  	 * BM_CHECKPOINT_NEEDED still set.	This is OK since any such buffer would
  	 * certainly need to be written for the next checkpoint attempt, too.
  	 */
    num_to_write = 0;
    for (buf_id = 0; buf_id < NBuffers; buf_id++) {
      volatile BufferDesc *bufHdr = (&BufferDescriptors[buf_id]);
  /*
  		 * Header spinlock is enough to examine BM_DIRTY, see comment in
  		 * SyncOneBuffer.
  		 */
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",1239);
        }
      }while (0);
      if (((bufHdr -> flags) & mask) == mask) {
        bufHdr -> flags |= 1 << 7;
        num_to_write++;
      }
       *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
    }
    if (num_to_write == 0) {
  /* nothing to do */
      return ;
    }
    ;
  /*
  	 * Loop over all buffers again, and write the ones (still) marked with
  	 * BM_CHECKPOINT_NEEDED.  In this loop, we start at the clock sweep point
  	 * since we might as well dump soon-to-be-recycled buffers first.
  	 *
  	 * Note that we don't read the buffer alloc count here --- that should be
  	 * left untouched till the next BgBufferSync() call.
  	 */
    buf_id = StrategySyncStart(((void *)0),((void *)0));
    num_to_scan = NBuffers;
    num_written = 0;
    while(num_to_scan-- > 0){
      volatile BufferDesc *bufHdr = (&BufferDescriptors[buf_id]);
  /*
  		 * We don't need to acquire the lock here, because we're only looking
  		 * at a single bit. It's possible that someone else writes the buffer
  		 * and clears the flag right after we check, but that doesn't matter
  		 * since SyncOneBuffer will then do nothing.  However, there is a
  		 * further race condition: it's conceivable that between the time we
  		 * examine the bit here and the time SyncOneBuffer acquires lock,
  		 * someone else not only wrote the buffer but replaced it with another
  		 * page and dirtied it.  In that improbable case, SyncOneBuffer will
  		 * write the buffer though we didn't need to.  It doesn't seem worth
  		 * guarding against this, though.
  		 */
      if ((bufHdr -> flags) & 1 << 7) {
        if (SyncOneBuffer(buf_id,((bool )0)) & 0x0001) {
          ;
          BgWriterStats . m_buf_written_checkpoints++;
          num_written++;
  /*
  				 * We know there are at most num_to_write buffers with
  				 * BM_CHECKPOINT_NEEDED set; so we can stop scanning if
  				 * num_written reaches num_to_write.
  				 *
  				 * Note that num_written doesn't include buffers written by
  				 * other backends, or by the bgwriter cleaning scan. That
  				 * means that the estimate of how much progress we've made is
  				 * conservative, and also that this test will often fail to
  				 * trigger.  But it seems worth making anyway.
  				 */
          if (num_written >= num_to_write) {
            break; 
          }
  /*
  				 * Sleep to throttle our I/O rate.
  				 */
          CheckpointWriteDelay(flags,((double )num_written) / num_to_write);
        }
      }
      if (++buf_id >= NBuffers) {
        buf_id = 0;
      }
    }
  /*
  	 * Update checkpoint statistics. As noted above, this doesn't include
  	 * buffers written by other backends or bgwriter scan.
  	 */
    CheckpointStats . ckpt_bufs_written += num_written;
    ;
  }
  /*
   * BgBufferSync -- Write out some dirty buffers in the pool.
   *
   * This is called periodically by the background writer process.
   *
   * Returns true if it's appropriate for the bgwriter process to go into
   * low-power hibernation mode.	(This happens if the strategy clock sweep
   * has been "lapped" and no buffer allocations have occurred recently,
   * or if the bgwriter has been effectively disabled by setting
   * bgwriter_lru_maxpages to 0.)
   */
  
  bool BgBufferSync()
  {
  /* info obtained from freelist.c */
    int strategy_buf_id;
    uint32 strategy_passes;
    uint32 recent_alloc;
  /*
  	 * Information saved between calls so we can determine the strategy
  	 * point's advance rate and avoid scanning already-cleaned buffers.
  	 */
    static bool saved_info_valid = (bool )0;
    static int prev_strategy_buf_id;
    static uint32 prev_strategy_passes;
    static int next_to_clean;
    static uint32 next_passes;
  /* Moving averages of allocation rate and clean-buffer density */
    static float smoothed_alloc = 0;
    static float smoothed_density = 10.0;
  /* Potentially these could be tunables, but for now, not */
    float smoothing_samples = 16;
    float scan_whole_pool_milliseconds = 120000.0;
  /* Used to compute how far we scan ahead */
    long strategy_delta;
    int bufs_to_lap;
    int bufs_ahead;
    float scans_per_alloc;
    int reusable_buffers_est;
    int upcoming_alloc_est;
    int min_scan_buffers;
  /* Variables for the scanning loop proper */
    int num_to_scan;
    int num_written;
    int reusable_buffers;
  /* Variables for final smoothed_density update */
    long new_strategy_delta;
    uint32 new_recent_alloc;
  /*
  	 * Find out where the freelist clock sweep currently is, and how many
  	 * buffer allocations have happened since our last call.
  	 */
    strategy_buf_id = StrategySyncStart(&strategy_passes,&recent_alloc);
  /* Report buffer alloc counts to pgstat */
    BgWriterStats . m_buf_alloc += recent_alloc;
  /*
  	 * If we're not running the LRU scan, just stop after doing the stats
  	 * stuff.  We mark the saved state invalid so that we can recover sanely
  	 * if LRU scan is turned back on later.
  	 */
    if (bgwriter_lru_maxpages <= 0) {
      saved_info_valid = ((bool )0);
      return (bool )1;
    }
  /*
  	 * Compute strategy_delta = how many buffers have been scanned by the
  	 * clock sweep since last time.  If first time through, assume none. Then
  	 * see if we are still ahead of the clock sweep, and if so, how many
  	 * buffers we could scan before we'd catch up with it and "lap" it. Note:
  	 * weird-looking coding of xxx_passes comparisons are to avoid bogus
  	 * behavior when the passes counts wrap around.
  	 */
    if (saved_info_valid) {
      int32 passes_delta = (strategy_passes - prev_strategy_passes);
      strategy_delta = (strategy_buf_id - prev_strategy_buf_id);
      strategy_delta += ((long )passes_delta) * NBuffers;
      ;
      if (((int32 )(next_passes - strategy_passes)) > 0) {
  /* we're one pass ahead of the strategy point */
        bufs_to_lap = strategy_buf_id - next_to_clean;
  #ifdef BGW_DEBUG
  #endif
      }
      else {
        if (next_passes == strategy_passes && next_to_clean >= strategy_buf_id) {
  /* on same pass, but ahead or at least not behind */
          bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
  #ifdef BGW_DEBUG
  #endif
        }
        else {
  /*
  			 * We're behind, so skip forward to the strategy point and start
  			 * cleaning from there.
  			 */
  #ifdef BGW_DEBUG
  #endif
          next_to_clean = strategy_buf_id;
          next_passes = strategy_passes;
          bufs_to_lap = NBuffers;
        }
      }
    }
    else {
  /*
  		 * Initializing at startup or after LRU scanning had been off. Always
  		 * start at the strategy point.
  		 */
  #ifdef BGW_DEBUG
  #endif
      strategy_delta = 0;
      next_to_clean = strategy_buf_id;
      next_passes = strategy_passes;
      bufs_to_lap = NBuffers;
    }
  /* Update saved info for next time */
    prev_strategy_buf_id = strategy_buf_id;
    prev_strategy_passes = strategy_passes;
    saved_info_valid = ((bool )1);
  /*
  	 * Compute how many buffers had to be scanned for each new allocation, ie,
  	 * 1/density of reusable buffers, and track a moving average of that.
  	 *
  	 * If the strategy point didn't move, we don't update the density estimate
  	 */
    if (strategy_delta > 0 && recent_alloc > 0) {
      scans_per_alloc = ((float )strategy_delta) / ((float )recent_alloc);
      smoothed_density += (scans_per_alloc - smoothed_density) / smoothing_samples;
    }
  /*
  	 * Estimate how many reusable buffers there are between the current
  	 * strategy point and where we've scanned ahead to, based on the smoothed
  	 * density estimate.
  	 */
    bufs_ahead = NBuffers - bufs_to_lap;
    reusable_buffers_est = (((float )bufs_ahead) / smoothed_density);
  /*
  	 * Track a moving average of recent buffer allocations.  Here, rather than
  	 * a true average we want a fast-attack, slow-decline behavior: we
  	 * immediately follow any increase.
  	 */
    if (smoothed_alloc <= ((float )recent_alloc)) {
      smoothed_alloc = recent_alloc;
    }
    else {
      smoothed_alloc += (((float )recent_alloc) - smoothed_alloc) / smoothing_samples;
    }
  /* Scale the estimate by a GUC to allow more aggressive tuning. */
    upcoming_alloc_est = ((int )(smoothed_alloc * bgwriter_lru_multiplier));
  /*
  	 * If recent_alloc remains at zero for many cycles, smoothed_alloc will
  	 * eventually underflow to zero, and the underflows produce annoying
  	 * kernel warnings on some platforms.  Once upcoming_alloc_est has gone to
  	 * zero, there's no point in tracking smaller and smaller values of
  	 * smoothed_alloc, so just reset it to exactly zero to avoid this
  	 * syndrome.  It will pop back up as soon as recent_alloc increases.
  	 */
    if (upcoming_alloc_est == 0) {
      smoothed_alloc = 0;
    }
  /*
  	 * Even in cases where there's been little or no buffer allocation
  	 * activity, we want to make a small amount of progress through the buffer
  	 * cache so that as many reusable buffers as possible are clean after an
  	 * idle period.
  	 *
  	 * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
  	 * the BGW will be called during the scan_whole_pool time; slice the
  	 * buffer pool into that many sections.
  	 */
    min_scan_buffers = ((int )(NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay)));
    if (upcoming_alloc_est < min_scan_buffers + reusable_buffers_est) {
  #ifdef BGW_DEBUG
  #endif
      upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
    }
  /*
  	 * Now write out dirty reusable buffers, working forward from the
  	 * next_to_clean point, until we have lapped the strategy scan, or cleaned
  	 * enough buffers to match our estimate of the next cycle's allocation
  	 * requirements, or hit the bgwriter_lru_maxpages limit.
  	 */
  /* Make sure we can handle the pin inside SyncOneBuffer */
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
    num_to_scan = bufs_to_lap;
    num_written = 0;
    reusable_buffers = reusable_buffers_est;
  /* Execute the LRU scan */
    while(num_to_scan > 0 && reusable_buffers < upcoming_alloc_est){
      int buffer_state = SyncOneBuffer(next_to_clean,((bool )1));
      if (++next_to_clean >= NBuffers) {
        next_to_clean = 0;
        next_passes++;
      }
      num_to_scan--;
      if (buffer_state & 0x0001) {
        reusable_buffers++;
        if (++num_written >= bgwriter_lru_maxpages) {
          BgWriterStats . m_maxwritten_clean++;
          break; 
        }
      }
      else {
        if (buffer_state & 0x0002) {
          reusable_buffers++;
        }
      }
    }
    BgWriterStats . m_buf_written_clean += num_written;
  #ifdef BGW_DEBUG
  #endif
  /*
  	 * Consider the above scan as being like a new allocation scan.
  	 * Characterize its density and update the smoothed one based on it. This
  	 * effectively halves the moving average period in cases where both the
  	 * strategy and the background writer are doing some useful scanning,
  	 * which is helpful because a long memory isn't as desirable on the
  	 * density estimates.
  	 */
    new_strategy_delta = (bufs_to_lap - num_to_scan);
    new_recent_alloc = (reusable_buffers - reusable_buffers_est);
    if (new_strategy_delta > 0 && new_recent_alloc > 0) {
      scans_per_alloc = ((float )new_strategy_delta) / ((float )new_recent_alloc);
      smoothed_density += (scans_per_alloc - smoothed_density) / smoothing_samples;
  #ifdef BGW_DEBUG
  #endif
    }
  /* Return true if OK to hibernate */
    return (bufs_to_lap == 0 && recent_alloc == 0);
  }
  /*
   * SyncOneBuffer -- process a single buffer during syncing.
   *
   * If skip_recently_used is true, we don't write currently-pinned buffers, nor
   * buffers marked recently used, as these are not replacement candidates.
   *
   * Returns a bitmask containing the following flag bits:
   *	BUF_WRITTEN: we wrote the buffer.
   *	BUF_REUSABLE: buffer is available for replacement, ie, it has
   *		pin count 0 and usage count 0.
   *
   * (BUF_WRITTEN could be set in error if FlushBuffers finds the buffer clean
   * after locking it, but we don't care all that much.)
   *
   * Note: caller must have done ResourceOwnerEnlargeBuffers.
   */
  
  static int SyncOneBuffer(int buf_id,bool skip_recently_used)
  {
    volatile BufferDesc *bufHdr = (&BufferDescriptors[buf_id]);
    int result = 0;
  /*
  	 * Check whether buffer needs writing.
  	 *
  	 * We can make this check without taking the buffer content lock so long
  	 * as we mark pages dirty in access methods *before* logging changes with
  	 * XLogInsert(): if someone marks the buffer dirty just after our check we
  	 * don't worry because our checkpoint.redo points before log record for
  	 * upcoming changes and so we are not required to write such dirty buffer.
  	 */
    do {
      if (tas(&bufHdr -> buf_hdr_lock)) {
        s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",1652);
      }
    }while (0);
    if (bufHdr -> refcount == 0 && (bufHdr -> usage_count) == 0) {
      result |= 0x0002;
    }
    else {
      if (skip_recently_used) {
  /* Caller told us not to write recently-used buffers */
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
        return result;
      }
    }
    if (!((bufHdr -> flags) & 1 << 1) || !((bufHdr -> flags) & 1 << 0)) {
  /* It's clean, so nothing to do */
       *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      return result;
    }
  /*
  	 * Pin it, share-lock it, write it.  (FlushBuffer will do nothing if the
  	 * buffer is clean by the time we've locked it.)
  	 */
    PinBuffer_Locked(bufHdr);
    LWLockAcquire(bufHdr -> content_lock,LW_SHARED);
    FlushBuffer(bufHdr,((void *)0));
    LWLockRelease(bufHdr -> content_lock);
    UnpinBuffer(bufHdr,((bool )1));
    return result | 0x0001;
  }
  /*
   *		AtEOXact_Buffers - clean up at end of transaction.
   *
   *		As of PostgreSQL 8.0, buffer pins should get released by the
   *		ResourceOwner mechanism.  This routine is just a debugging
   *		cross-check that no pins remain.
   */
  
  void AtEOXact_Buffers(bool isCommit)
  {
  #ifdef USE_ASSERT_CHECKING
  #endif
    AtEOXact_LocalBuffers(isCommit);
  }
  /*
   * InitBufferPoolBackend --- second-stage initialization of a new backend
   *
   * This is called after we have acquired a PGPROC and so can safely get
   * LWLocks.  We don't currently need to do anything at this stage ...
   * except register a shmem-exit callback.  AtProcExit_Buffers needs LWLock
   * access, and thereby has to be called at the corresponding phase of
   * backend shutdown.
   */
  
  void InitBufferPoolBackend()
  {
    on_shmem_exit(AtProcExit_Buffers,0);
  }
  /*
   * During backend exit, ensure that we released all shared-buffer locks and
   * assert that we have no remaining pins.
   */
  
  static void AtProcExit_Buffers(int code,Datum arg)
  {
    AbortBufferIO();
    UnlockBuffers();
  #ifdef USE_ASSERT_CHECKING
  #endif
  /* localbuf.c needs a chance too */
    AtProcExit_LocalBuffers();
  }
  /*
   * Helper routine to issue warnings when a buffer is unexpectedly pinned
   */
  
  void PrintBufferLeakWarning(Buffer buffer)
  {
    volatile BufferDesc *buf;
    int32 loccount;
    char *path;
    BackendId backend;
    ;
    if (buffer < 0) {
      buf = (&LocalBufferDescriptors[-buffer - 1]);
      loccount = LocalRefCount[-buffer - 1];
      backend = MyBackendId;
    }
    else {
      buf = (&BufferDescriptors[buffer - 1]);
      loccount = PrivateRefCount[buffer - 1];
      backend = - 1;
    }
  /* theoretically we should lock the bufhdr here */
    path = relpathbackend(buf -> tag . rnode,backend,buf -> tag . forkNum);
    (elog_start("bufmgr.c",1779,__func__) , elog_finish(19,"buffer refcount leak: [%03d] (rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",buffer,path,buf -> tag . blockNum,(buf -> flags),buf -> refcount,loccount));
    pfree(path);
  }
  /*
   * CheckPointBuffers
   *
   * Flush all dirty blocks in buffer pool to disk at checkpoint time.
   *
   * Note: temporary relations do not participate in checkpoints, so they don't
   * need to be flushed.
   */
  
  void CheckPointBuffers(int flags)
  {
    ;
    CheckpointStats . ckpt_write_t = GetCurrentTimestamp();
    BufferSync(flags);
    CheckpointStats . ckpt_sync_t = GetCurrentTimestamp();
    ;
    smgrsync();
    CheckpointStats . ckpt_sync_end_t = GetCurrentTimestamp();
    ;
  }
  /*
   * Do whatever is needed to prepare for commit at the bufmgr and smgr levels
   */
  
  void BufmgrCommit()
  {
  /* Nothing to do in bufmgr anymore... */
  }
  /*
   * BufferGetBlockNumber
   *		Returns the block number associated with a buffer.
   *
   * Note:
   *		Assumes that the buffer is valid and pinned, else the
   *		value may be obsolete immediately...
   */
  
  BlockNumber BufferGetBlockNumber(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
    ;
    if (buffer < 0) {
      bufHdr = (&LocalBufferDescriptors[-buffer - 1]);
    }
    else {
      bufHdr = (&BufferDescriptors[buffer - 1]);
    }
  /* pinned, so OK to read tag without spinlock */
    return bufHdr -> tag . blockNum;
  }
  /*
   * BufferGetTag
   *		Returns the relfilenode, fork number and block number associated with
   *		a buffer.
   */
  
  void BufferGetTag(Buffer buffer,RelFileNode *rnode,ForkNumber *forknum,BlockNumber *blknum)
  {
    volatile BufferDesc *bufHdr;
  /* Do the same checks as BufferGetBlockNumber. */
    ;
    if (buffer < 0) {
      bufHdr = (&LocalBufferDescriptors[-buffer - 1]);
    }
    else {
      bufHdr = (&BufferDescriptors[buffer - 1]);
    }
  /* pinned, so OK to read tag without spinlock */
     *rnode = bufHdr -> tag . rnode;
     *forknum = bufHdr -> tag . forkNum;
     *blknum = bufHdr -> tag . blockNum;
  }
  /*
   * FlushBuffer
   *		Physically write out a shared buffer.
   *
   * NOTE: this actually just passes the buffer contents to the kernel; the
   * real write to disk won't happen until the kernel feels like it.  This
   * is okay from our point of view since we can redo the changes from WAL.
   * However, we will need to force the changes to disk via fsync before
   * we can checkpoint WAL.
   *
   * The caller must hold a pin on the buffer and have share-locked the
   * buffer contents.  (Note: a share-lock does not prevent updates of
   * hint bits in the buffer, so the page could change while the write
   * is in progress, but we assume that that will not invalidate the data
   * written.)
   *
   * If the caller has an smgr reference for the buffer's relation, pass it
   * as the second parameter.  If not, pass NULL.
   */
  
  static void FlushBuffer(volatile BufferDesc *buf,SMgrRelation reln)
  {
    XLogRecPtr recptr;
    ErrorContextCallback errcontext;
    instr_time io_start;
    instr_time io_time;
  /*
  	 * Acquire the buffer's io_in_progress lock.  If StartBufferIO returns
  	 * false, then someone else flushed the buffer before we could, so we need
  	 * not do anything.
  	 */
    if (!StartBufferIO(buf,((bool )0))) {
      return ;
    }
  /* Setup error traceback support for ereport() */
    errcontext . callback = shared_buffer_write_error_callback;
    errcontext . arg = ((void *)buf);
    errcontext . previous = error_context_stack;
    error_context_stack = &errcontext;
  /* Find smgr relation for buffer */
    if (reln == ((void *)0)) {
      reln = smgropen(buf -> tag . rnode,- 1);
    }
    ;
  /*
  	 * Force XLOG flush up to buffer's LSN.  This implements the basic WAL
  	 * rule that log updates must hit disk before any of the data-file changes
  	 * they describe do.
  	 */
    recptr = ((PageHeader )((Block )(BufferBlocks + ((Size )(buf -> buf_id)) * 8192))) -> pd_lsn;
    XLogFlush(recptr);
  /*
  	 * Now it's safe to write buffer to disk. Note that no one else should
  	 * have been able to write it while we were busy with log flushing because
  	 * we have the io_in_progress lock.
  	 */
  /* To check if block content changes while flushing. - vadim 01/17/97 */
    do {
      if (tas(&buf -> buf_hdr_lock)) {
        s_lock(&buf -> buf_hdr_lock,"bufmgr.c",1934);
      }
    }while (0);
    buf -> flags &= ~(1 << 5);
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
    if (track_io_timing) {
      gettimeofday(&io_start,((void *)0));
    }
    smgrwrite(reln,buf -> tag . forkNum,buf -> tag . blockNum,((char *)((Block )(BufferBlocks + ((Size )(buf -> buf_id)) * 8192))),((bool )0));
    if (track_io_timing) {
      gettimeofday(&io_time,((void *)0));
      do {
        io_time . tv_sec -= io_start . tv_sec;
        io_time . tv_usec -= io_start . tv_usec;
        while(io_time . tv_usec < 0){
          io_time . tv_usec += 1000000;
          io_time . tv_sec--;
        }
      }while (0);
      pgStatBlockWriteTime += ((uint64 )io_time . tv_sec) * ((uint64 )1000000) + ((uint64 )io_time . tv_usec);
      do {
        pgBufferUsage . blk_write_time . tv_sec += io_time . tv_sec;
        pgBufferUsage . blk_write_time . tv_usec += io_time . tv_usec;
        while(pgBufferUsage . blk_write_time . tv_usec >= 1000000){
          pgBufferUsage . blk_write_time . tv_usec -= 1000000;
          pgBufferUsage . blk_write_time . tv_sec++;
        }
      }while (0);
    }
    pgBufferUsage . shared_blks_written++;
  /*
  	 * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
  	 * end the io_in_progress state.
  	 */
    TerminateBufferIO(buf,((bool )1),0);
    ;
  /* Pop the error context stack */
    error_context_stack = errcontext . previous;
  }
  /*
   * RelationGetNumberOfBlocks
   *		Determines the current number of pages in the relation.
   */
  
  BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,ForkNumber forkNum)
  {
  /* Open it at the smgr level if not already done */
    do {
      if (relation -> rd_smgr == ((void *)0)) {
        smgrsetowner(&relation -> rd_smgr,smgropen(relation -> rd_node,relation -> rd_backend));
      }
    }while (0);
    return smgrnblocks(relation -> rd_smgr,forkNum);
  }
  /*
   * BufferIsPermanent
   *		Determines whether a buffer will potentially still be around after
   *		a crash.  Caller must hold a buffer pin.
   */
  
  bool BufferIsPermanent(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
  /* Local buffers are used only for temp relations. */
    if (buffer < 0) {
      return (bool )0;
    }
  /* Make sure we've got a real buffer, and that we hold a pin on it. */
    ;
    ;
  /*
  	 * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
  	 * need not bother with the buffer header spinlock.  Even if someone else
  	 * changes the buffer header flags while we're doing this, we assume that
  	 * changing an aligned 2-byte BufFlags value is atomic, so we'll read the
  	 * old value or the new value, but not random garbage.
  	 */
    bufHdr = (&BufferDescriptors[buffer - 1]);
    return (((bufHdr -> flags) & 1 << 8) != 0);
  }
  /* ---------------------------------------------------------------------
   *		DropRelFileNodeBuffers
   *
   *		This function removes from the buffer pool all the pages of the
   *		specified relation fork that have block numbers >= firstDelBlock.
   *		(In particular, with firstDelBlock = 0, all pages are removed.)
   *		Dirty pages are simply dropped, without bothering to write them
   *		out first.	Therefore, this is NOT rollback-able, and so should be
   *		used only with extreme caution!
   *
   *		Currently, this is called only from smgr.c when the underlying file
   *		is about to be deleted or truncated (firstDelBlock is needed for
   *		the truncation case).  The data in the affected pages would therefore
   *		be deleted momentarily anyway, and there is no point in writing it.
   *		It is the responsibility of higher-level code to ensure that the
   *		deletion or truncation does not lose any data that could be needed
   *		later.	It is also the responsibility of higher-level code to ensure
   *		that no other process could be trying to load more pages of the
   *		relation into buffers.
   *
   *		XXX currently it sequentially searches the buffer pool, should be
   *		changed to more clever ways of searching.  However, this routine
   *		is used only in code paths that aren't very performance-critical,
   *		and we shouldn't slow down the hot paths to make it faster ...
   * --------------------------------------------------------------------
   */
  
  void DropRelFileNodeBuffers(RelFileNodeBackend rnode,ForkNumber forkNum,BlockNumber firstDelBlock)
  {
    int i;
  /* If it's a local relation, it's localbuf.c's problem. */
    if (rnode . backend != - 1) {
      if (rnode . backend == MyBackendId) {
        DropRelFileNodeLocalBuffers(rnode . node,forkNum,firstDelBlock);
      }
      return ;
    }
    for (i = 0; i < NBuffers; i++) {
      volatile BufferDesc *bufHdr = (&BufferDescriptors[i]);
  /*
  		 * We can make this a tad faster by prechecking the buffer tag before
  		 * we attempt to lock the buffer; this saves a lot of lock
  		 * acquisitions in typical cases.  It should be safe because the
  		 * caller must have AccessExclusiveLock on the relation, or some other
  		 * reason to be certain that no one is loading new pages of the rel
  		 * into the buffer pool.  (Otherwise we might well miss such pages
  		 * entirely.)  Therefore, while the tag might be changing while we
  		 * look at it, it can't be changing *to* a value we care about, only
  		 * *away* from such a value.  So false negatives are impossible, and
  		 * false positives are safe because we'll recheck after getting the
  		 * buffer lock.
  		 *
  		 * We could check forkNum and blockNum as well as the rnode, but the
  		 * incremental win from doing so seems small.
  		 */
      if (!(bufHdr -> tag . rnode . relNode == rnode . node . relNode && bufHdr -> tag . rnode . dbNode == rnode . node . dbNode && bufHdr -> tag . rnode . spcNode == rnode . node . spcNode)) {
        continue; 
      }
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2078);
        }
      }while (0);
      if (bufHdr -> tag . rnode . relNode == rnode . node . relNode && bufHdr -> tag . rnode . dbNode == rnode . node . dbNode && bufHdr -> tag . rnode . spcNode == rnode . node . spcNode && bufHdr -> tag . forkNum == forkNum && bufHdr -> tag . blockNum >= firstDelBlock) {
  /* releases spinlock */
        InvalidateBuffer(bufHdr);
      }
      else {
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      }
    }
  }
  /* ---------------------------------------------------------------------
   *		DropRelFileNodeAllBuffers
   *
   *		This function removes from the buffer pool all the pages of all
   *		forks of the specified relation.  It's equivalent to calling
   *		DropRelFileNodeBuffers once per fork with firstDelBlock = 0.
   * --------------------------------------------------------------------
   */
  
  void DropRelFileNodeAllBuffers(RelFileNodeBackend rnode)
  {
    int i;
  /* If it's a local relation, it's localbuf.c's problem. */
    if (rnode . backend != - 1) {
      if (rnode . backend == MyBackendId) {
        DropRelFileNodeAllLocalBuffers(rnode . node);
      }
      return ;
    }
    for (i = 0; i < NBuffers; i++) {
      volatile BufferDesc *bufHdr = (&BufferDescriptors[i]);
  /*
  		 * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
  		 * and saves some cycles.
  		 */
      if (!(bufHdr -> tag . rnode . relNode == rnode . node . relNode && bufHdr -> tag . rnode . dbNode == rnode . node . dbNode && bufHdr -> tag . rnode . spcNode == rnode . node . spcNode)) {
        continue; 
      }
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2120);
        }
      }while (0);
      if (bufHdr -> tag . rnode . relNode == rnode . node . relNode && bufHdr -> tag . rnode . dbNode == rnode . node . dbNode && bufHdr -> tag . rnode . spcNode == rnode . node . spcNode) {
  /* releases spinlock */
        InvalidateBuffer(bufHdr);
      }
      else {
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      }
    }
  }
  /* ---------------------------------------------------------------------
   *		DropDatabaseBuffers
   *
   *		This function removes all the buffers in the buffer cache for a
   *		particular database.  Dirty pages are simply dropped, without
   *		bothering to write them out first.	This is used when we destroy a
   *		database, to avoid trying to flush data to disk when the directory
   *		tree no longer exists.	Implementation is pretty similar to
   *		DropRelFileNodeBuffers() which is for destroying just one relation.
   * --------------------------------------------------------------------
   */
  
  void DropDatabaseBuffers(Oid dbid)
  {
    int i;
  /*
  	 * We needn't consider local buffers, since by assumption the target
  	 * database isn't our own.
  	 */
    for (i = 0; i < NBuffers; i++) {
      volatile BufferDesc *bufHdr = (&BufferDescriptors[i]);
  /*
  		 * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
  		 * and saves some cycles.
  		 */
      if (bufHdr -> tag . rnode . dbNode != dbid) {
        continue; 
      }
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2160);
        }
      }while (0);
      if (bufHdr -> tag . rnode . dbNode == dbid) {
  /* releases spinlock */
        InvalidateBuffer(bufHdr);
      }
      else {
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      }
    }
  }
  /* -----------------------------------------------------------------
   *		PrintBufferDescs
   *
   *		this function prints all the buffer descriptors, for debugging
   *		use only.
   * -----------------------------------------------------------------
   */
  #ifdef NOT_USED
  /* theoretically we should lock the bufhdr here */
  #endif
  #ifdef NOT_USED
  /* theoretically we should lock the bufhdr here */
  #endif
  /* ---------------------------------------------------------------------
   *		FlushRelationBuffers
   *
   *		This function writes all dirty pages of a relation out to disk
   *		(or more accurately, out to kernel disk buffers), ensuring that the
   *		kernel has an up-to-date view of the relation.
   *
   *		Generally, the caller should be holding AccessExclusiveLock on the
   *		target relation to ensure that no other backend is busy dirtying
   *		more blocks of the relation; the effects can't be expected to last
   *		after the lock is released.
   *
   *		XXX currently it sequentially searches the buffer pool, should be
   *		changed to more clever ways of searching.  This routine is not
   *		used in any performance-critical code paths, so it's not worth
   *		adding additional overhead to normal paths to make it go faster;
   *		but see also DropRelFileNodeBuffers.
   * --------------------------------------------------------------------
   */
  
  void FlushRelationBuffers(Relation rel)
  {
    int i;
    volatile BufferDesc *bufHdr;
  /* Open rel at the smgr level if not already done */
    do {
      if (rel -> rd_smgr == ((void *)0)) {
        smgrsetowner(&rel -> rd_smgr,smgropen(rel -> rd_node,rel -> rd_backend));
      }
    }while (0);
    if ((rel -> rd_rel -> relpersistence) == 't') {
      for (i = 0; i < NLocBuffer; i++) {
        bufHdr = (&LocalBufferDescriptors[i]);
        if (bufHdr -> tag . rnode . relNode == rel -> rd_node . relNode && bufHdr -> tag . rnode . dbNode == rel -> rd_node . dbNode && bufHdr -> tag . rnode . spcNode == rel -> rd_node . spcNode && (bufHdr -> flags) & 1 << 1 && (bufHdr -> flags) & 1 << 0) {
          ErrorContextCallback errcontext;
  /* Setup error traceback support for ereport() */
          errcontext . callback = local_buffer_write_error_callback;
          errcontext . arg = ((void *)bufHdr);
          errcontext . previous = error_context_stack;
          error_context_stack = &errcontext;
          smgrwrite(rel -> rd_smgr,bufHdr -> tag . forkNum,bufHdr -> tag . blockNum,((char *)LocalBufferBlockPointers[-(bufHdr -> buf_id + 2)]),((bool )0));
          bufHdr -> flags &= ~(1 << 0 | 1 << 5);
  /* Pop the error context stack */
          error_context_stack = errcontext . previous;
        }
      }
      return ;
    }
  /* Make sure we can handle the pin inside the loop */
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
    for (i = 0; i < NBuffers; i++) {
      bufHdr = (&BufferDescriptors[i]);
  /*
  		 * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
  		 * and saves some cycles.
  		 */
      if (!(bufHdr -> tag . rnode . relNode == rel -> rd_node . relNode && bufHdr -> tag . rnode . dbNode == rel -> rd_node . dbNode && bufHdr -> tag . rnode . spcNode == rel -> rd_node . spcNode)) {
        continue; 
      }
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2294);
        }
      }while (0);
      if (bufHdr -> tag . rnode . relNode == rel -> rd_node . relNode && bufHdr -> tag . rnode . dbNode == rel -> rd_node . dbNode && bufHdr -> tag . rnode . spcNode == rel -> rd_node . spcNode && (bufHdr -> flags) & 1 << 1 && (bufHdr -> flags) & 1 << 0) {
        PinBuffer_Locked(bufHdr);
        LWLockAcquire(bufHdr -> content_lock,LW_SHARED);
        FlushBuffer(bufHdr,rel -> rd_smgr);
        LWLockRelease(bufHdr -> content_lock);
        UnpinBuffer(bufHdr,((bool )1));
      }
      else {
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      }
    }
  }
  /* ---------------------------------------------------------------------
   *		FlushDatabaseBuffers
   *
   *		This function writes all dirty pages of a database out to disk
   *		(or more accurately, out to kernel disk buffers), ensuring that the
   *		kernel has an up-to-date view of the database.
   *
   *		Generally, the caller should be holding an appropriate lock to ensure
   *		no other backend is active in the target database; otherwise more
   *		pages could get dirtied.
   *
   *		Note we don't worry about flushing any pages of temporary relations.
   *		It's assumed these wouldn't be interesting.
   * --------------------------------------------------------------------
   */
  
  void FlushDatabaseBuffers(Oid dbid)
  {
    int i;
    volatile BufferDesc *bufHdr;
  /* Make sure we can handle the pin inside the loop */
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
    for (i = 0; i < NBuffers; i++) {
      bufHdr = (&BufferDescriptors[i]);
  /*
  		 * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
  		 * and saves some cycles.
  		 */
      if (bufHdr -> tag . rnode . dbNode != dbid) {
        continue; 
      }
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2344);
        }
      }while (0);
      if (bufHdr -> tag . rnode . dbNode == dbid && (bufHdr -> flags) & 1 << 1 && (bufHdr -> flags) & 1 << 0) {
        PinBuffer_Locked(bufHdr);
        LWLockAcquire(bufHdr -> content_lock,LW_SHARED);
        FlushBuffer(bufHdr,((void *)0));
        LWLockRelease(bufHdr -> content_lock);
        UnpinBuffer(bufHdr,((bool )1));
      }
      else {
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      }
    }
  }
  /*
   * ReleaseBuffer -- release the pin on a buffer
   */
  
  void ReleaseBuffer(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
    if (!((((void )((bool )1)) , buffer != 0))) {
      (elog_start("bufmgr.c",2368,__func__) , elog_finish(20,"bad buffer ID: %d",buffer));
    }
    ResourceOwnerForgetBuffer(CurrentResourceOwner,buffer);
    if (buffer < 0) {
      ;
      LocalRefCount[-buffer - 1]--;
      return ;
    }
    bufHdr = (&BufferDescriptors[buffer - 1]);
    ;
    if (PrivateRefCount[buffer - 1] > 1) {
      PrivateRefCount[buffer - 1]--;
    }
    else {
      UnpinBuffer(bufHdr,((bool )0));
    }
  }
  /*
   * UnlockReleaseBuffer -- release the content lock and pin on a buffer
   *
   * This is just a shorthand for a common combination.
   */
  
  void UnlockReleaseBuffer(Buffer buffer)
  {
    LockBuffer(buffer,0);
    ReleaseBuffer(buffer);
  }
  /*
   * IncrBufferRefCount
   *		Increment the pin count on a buffer that we have *already* pinned
   *		at least once.
   *
   *		This function cannot be used on a buffer we do not have pinned,
   *		because it doesn't change the shared buffer state.
   */
  
  void IncrBufferRefCount(Buffer buffer)
  {
    ;
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
    ResourceOwnerRememberBuffer(CurrentResourceOwner,buffer);
    if (buffer < 0) {
      LocalRefCount[-buffer - 1]++;
    }
    else {
      PrivateRefCount[buffer - 1]++;
    }
  }
  /*
   * SetBufferCommitInfoNeedsSave
   *
   *	Mark a buffer dirty when we have updated tuple commit-status bits in it.
   *
   * This is essentially the same as MarkBufferDirty, except that the caller
   * might have only share-lock instead of exclusive-lock on the buffer's
   * content lock.  We preserve the distinction mainly as a way of documenting
   * that the caller has not made a critical data change --- the status-bit
   * update could be redone by someone else just as easily.  Therefore, no WAL
   * log record need be generated, whereas calls to MarkBufferDirty really ought
   * to be associated with a WAL-entry-creating action.
   */
  
  void SetBufferCommitInfoNeedsSave(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
    if (!((((void )((bool )1)) , buffer != 0))) {
      (elog_start("bufmgr.c",2440,__func__) , elog_finish(20,"bad buffer ID: %d",buffer));
    }
    if (buffer < 0) {
      MarkLocalBufferDirty(buffer);
      return ;
    }
    bufHdr = (&BufferDescriptors[buffer - 1]);
    ;
  /* here, either share or exclusive lock is OK */
    ;
  /*
  	 * This routine might get called many times on the same page, if we are
  	 * making the first scan after commit of an xact that added/deleted many
  	 * tuples.	So, be as quick as we can if the buffer is already dirty.  We
  	 * do this by not acquiring spinlock if it looks like the status bits are
  	 * already.  Since we make this test unlocked, there's a chance we might
  	 * fail to notice that the flags have just been cleared, and failed to
  	 * reset them, due to memory-ordering issues.  But since this function is
  	 * only intended to be used in cases where failing to write out the data
  	 * would be harmless anyway, it doesn't really matter.
  	 */
    if (((bufHdr -> flags) & (1 << 0 | 1 << 5)) != (1 << 0 | 1 << 5)) {
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2468);
        }
      }while (0);
      ;
      if (!((bufHdr -> flags) & 1 << 0)) {
  /* Do vacuum cost accounting */
        VacuumPageDirty++;
        if (VacuumCostActive) {
          VacuumCostBalance += VacuumCostPageDirty;
        }
      }
      bufHdr -> flags |= 1 << 0 | 1 << 5;
       *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
    }
  }
  /*
   * Release buffer content locks for shared buffers.
   *
   * Used to clean up after errors.
   *
   * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
   * of releasing buffer content locks per se; the only thing we need to deal
   * with here is clearing any PIN_COUNT request that was in progress.
   */
  
  void UnlockBuffers()
  {
    volatile BufferDesc *buf = PinCountWaitBuf;
    if (buf) {
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",2498);
        }
      }while (0);
  /*
  		 * Don't complain if flag bit not set; it could have been reset but we
  		 * got a cancel/die interrupt before getting the signal.
  		 */
      if (((buf -> flags) & 1 << 6) != 0 && buf -> wait_backend_pid == MyProcPid) {
        buf -> flags &= ~(1 << 6);
      }
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      PinCountWaitBuf = ((void *)0);
    }
  }
  /*
   * Acquire or release the content_lock for the buffer.
   */
  
  void LockBuffer(Buffer buffer,int mode)
  {
    volatile BufferDesc *buf;
    ;
    if (buffer < 0) {
  /* local buffers need no lock */
      return ;
    }
    buf = (&BufferDescriptors[buffer - 1]);
    if (mode == 0) {
      LWLockRelease(buf -> content_lock);
    }
    else {
      if (mode == 1) {
        LWLockAcquire(buf -> content_lock,LW_SHARED);
      }
      else {
        if (mode == 2) {
          LWLockAcquire(buf -> content_lock,LW_EXCLUSIVE);
        }
        else {
          (elog_start("bufmgr.c",2535,__func__) , elog_finish(20,"unrecognized buffer lock mode: %d",mode));
        }
      }
    }
  }
  /*
   * Acquire the content_lock for the buffer, but only if we don't have to wait.
   *
   * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
   */
  
  bool ConditionalLockBuffer(Buffer buffer)
  {
    volatile BufferDesc *buf;
    ;
    if (buffer < 0) {
  /* act as though we got it */
      return (bool )1;
    }
    buf = (&BufferDescriptors[buffer - 1]);
    return LWLockConditionalAcquire(buf -> content_lock,LW_EXCLUSIVE);
  }
  /*
   * LockBufferForCleanup - lock a buffer in preparation for deleting items
   *
   * Items may be deleted from a disk page only when the caller (a) holds an
   * exclusive lock on the buffer and (b) has observed that no other backend
   * holds a pin on the buffer.  If there is a pin, then the other backend
   * might have a pointer into the buffer (for example, a heapscan reference
   * to an item --- see README for more details).  It's OK if a pin is added
   * after the cleanup starts, however; the newly-arrived backend will be
   * unable to look at the page until we release the exclusive lock.
   *
   * To implement this protocol, a would-be deleter must pin the buffer and
   * then call LockBufferForCleanup().  LockBufferForCleanup() is similar to
   * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
   * it has successfully observed pin count = 1.
   */
  
  void LockBufferForCleanup(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
    ;
    ;
    if (buffer < 0) {
  /* There should be exactly one pin */
      if (LocalRefCount[-buffer - 1] != 1) {
        (elog_start("bufmgr.c",2585,__func__) , elog_finish(20,"incorrect local pin count: %d",LocalRefCount[-buffer - 1]));
      }
  /* Nobody else to wait for */
      return ;
    }
  /* There should be exactly one local pin */
    if (PrivateRefCount[buffer - 1] != 1) {
      (elog_start("bufmgr.c",2593,__func__) , elog_finish(20,"incorrect local pin count: %d",PrivateRefCount[buffer - 1]));
    }
    bufHdr = (&BufferDescriptors[buffer - 1]);
    for (; ; ) {
  /* Try to acquire lock */
      LockBuffer(buffer,2);
      do {
        if (tas(&bufHdr -> buf_hdr_lock)) {
          s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2602);
        }
      }while (0);
      ;
      if (bufHdr -> refcount == 1) {
  /* Successfully acquired exclusive lock with pincount 1 */
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
        return ;
      }
  /* Failed, so mark myself as waiting for pincount 1 */
      if ((bufHdr -> flags) & 1 << 6) {
         *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
        LockBuffer(buffer,0);
        (elog_start("bufmgr.c",2615,__func__) , elog_finish(20,"multiple backends attempting to wait for pincount 1"));
      }
      bufHdr -> wait_backend_pid = MyProcPid;
      bufHdr -> flags |= 1 << 6;
      PinCountWaitBuf = bufHdr;
       *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      LockBuffer(buffer,0);
  /* Wait to be signaled by UnpinBuffer() */
      if (standbyState >= STANDBY_SNAPSHOT_PENDING) {
  /* Publish the bufid that Startup process waits on */
        SetStartupBufferPinWaitBufId(buffer - 1);
  /* Set alarm and then wait to be signaled by UnpinBuffer() */
        ResolveRecoveryConflictWithBufferPin();
  /* Reset the published bufid */
        SetStartupBufferPinWaitBufId(- 1);
      }
      else {
        ProcWaitForSignal();
      }
      PinCountWaitBuf = ((void *)0);
  /* Loop back and try again */
    }
  }
  /*
   * Check called from RecoveryConflictInterrupt handler when Startup
   * process requests cancellation of all pin holders that are blocking it.
   */
  
  bool HoldingBufferPinThatDelaysRecovery()
  {
    int bufid = GetStartupBufferPinWaitBufId();
  /*
  	 * If we get woken slowly then it's possible that the Startup process was
  	 * already woken by other backends before we got here. Also possible that
  	 * we get here by multiple interrupts or interrupts at inappropriate
  	 * times, so make sure we do nothing if the bufid is not set.
  	 */
    if (bufid < 0) {
      return (bool )0;
    }
    if (PrivateRefCount[bufid] > 0) {
      return (bool )1;
    }
    return (bool )0;
  }
  /*
   * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
   *
   * We won't loop, but just check once to see if the pin count is OK.  If
   * not, return FALSE with no lock held.
   */
  
  bool ConditionalLockBufferForCleanup(Buffer buffer)
  {
    volatile BufferDesc *bufHdr;
    ;
    if (buffer < 0) {
  /* There should be exactly one pin */
      ;
      if (LocalRefCount[-buffer - 1] != 1) {
        return (bool )0;
      }
  /* Nobody else to wait for */
      return (bool )1;
    }
  /* There should be exactly one local pin */
    ;
    if (PrivateRefCount[buffer - 1] != 1) {
      return (bool )0;
    }
  /* Try to acquire lock */
    if (!ConditionalLockBuffer(buffer)) {
      return (bool )0;
    }
    bufHdr = (&BufferDescriptors[buffer - 1]);
    do {
      if (tas(&bufHdr -> buf_hdr_lock)) {
        s_lock(&bufHdr -> buf_hdr_lock,"bufmgr.c",2698);
      }
    }while (0);
    ;
    if (bufHdr -> refcount == 1) {
  /* Successfully acquired exclusive lock with pincount 1 */
       *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
      return (bool )1;
    }
  /* Failed, so release the lock */
     *((volatile slock_t *)(&bufHdr -> buf_hdr_lock)) = 0;
    LockBuffer(buffer,0);
    return (bool )0;
  }
  /*
   *	Functions for buffer I/O handling
   *
   *	Note: We assume that nested buffer I/O never occurs.
   *	i.e at most one io_in_progress lock is held per proc.
   *
   *	Also note that these are used only for shared buffers, not local ones.
   */
  /*
   * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
   */
  
  static void WaitIO(volatile BufferDesc *buf)
  {
  /*
  	 * Changed to wait until there's no IO - Inoue 01/13/2000
  	 *
  	 * Note this is *necessary* because an error abort in the process doing
  	 * I/O could release the io_in_progress_lock prematurely. See
  	 * AbortBufferIO.
  	 */
    for (; ; ) {
      BufFlags sv_flags;
  /*
  		 * It may not be necessary to acquire the spinlock to check the flag
  		 * here, but since this test is essential for correctness, we'd better
  		 * play it safe.
  		 */
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",2745);
        }
      }while (0);
      sv_flags = buf -> flags;
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      if (!(sv_flags & 1 << 3)) {
        break; 
      }
      LWLockAcquire(buf -> io_in_progress_lock,LW_SHARED);
      LWLockRelease(buf -> io_in_progress_lock);
    }
  }
  /*
   * StartBufferIO: begin I/O on this buffer
   *	(Assumptions)
   *	My process is executing no IO
   *	The buffer is Pinned
   *
   * In some scenarios there are race conditions in which multiple backends
   * could attempt the same I/O operation concurrently.  If someone else
   * has already started I/O on this buffer then we will block on the
   * io_in_progress lock until he's done.
   *
   * Input operations are only attempted on buffers that are not BM_VALID,
   * and output operations only on buffers that are BM_VALID and BM_DIRTY,
   * so we can always tell if the work is already done.
   *
   * Returns TRUE if we successfully marked the buffer as I/O busy,
   * FALSE if someone else already did the work.
   */
  
  static bool StartBufferIO(volatile BufferDesc *buf,bool forInput)
  {
    ;
    for (; ; ) {
  /*
  		 * Grab the io_in_progress lock so that other processes can wait for
  		 * me to finish the I/O.
  		 */
      LWLockAcquire(buf -> io_in_progress_lock,LW_EXCLUSIVE);
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",2786);
        }
      }while (0);
      if (!((buf -> flags) & 1 << 3)) {
        break; 
      }
  /*
  		 * The only way BM_IO_IN_PROGRESS could be set when the io_in_progress
  		 * lock isn't held is if the process doing the I/O is recovering from
  		 * an error (see AbortBufferIO).  If that's the case, we must wait for
  		 * him to get unwedged.
  		 */
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      LWLockRelease(buf -> io_in_progress_lock);
      WaitIO(buf);
    }
  /* Once we get here, there is definitely no I/O active on this buffer */
    if (forInput?(buf -> flags) & 1 << 1 : !((buf -> flags) & 1 << 0)) {
  /* someone else already did the I/O */
       *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      LWLockRelease(buf -> io_in_progress_lock);
      return (bool )0;
    }
    buf -> flags |= 1 << 3;
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
    InProgressBuf = buf;
    IsForInput = forInput;
    return (bool )1;
  }
  /*
   * TerminateBufferIO: release a buffer we were doing I/O on
   *	(Assumptions)
   *	My process is executing IO for the buffer
   *	BM_IO_IN_PROGRESS bit is set for the buffer
   *	We hold the buffer's io_in_progress lock
   *	The buffer is Pinned
   *
   * If clear_dirty is TRUE and BM_JUST_DIRTIED is not set, we clear the
   * buffer's BM_DIRTY flag.  This is appropriate when terminating a
   * successful write.  The check on BM_JUST_DIRTIED is necessary to avoid
   * marking the buffer clean if it was re-dirtied while we were writing.
   *
   * set_flag_bits gets ORed into the buffer's flags.  It must include
   * BM_IO_ERROR in a failure case.  For successful completion it could
   * be 0, or BM_VALID if we just finished reading in the page.
   */
  
  static void TerminateBufferIO(volatile BufferDesc *buf,bool clear_dirty,int set_flag_bits)
  {
    ;
    do {
      if (tas(&buf -> buf_hdr_lock)) {
        s_lock(&buf -> buf_hdr_lock,"bufmgr.c",2845);
      }
    }while (0);
    ;
    buf -> flags &= ~(1 << 3 | 1 << 4);
    if (clear_dirty && !((buf -> flags) & 1 << 5)) {
      buf -> flags &= ~(1 << 0 | 1 << 7);
    }
    buf -> flags |= set_flag_bits;
     *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
    InProgressBuf = ((void *)0);
    LWLockRelease(buf -> io_in_progress_lock);
  }
  /*
   * AbortBufferIO: Clean up any active buffer I/O after an error.
   *
   *	All LWLocks we might have held have been released,
   *	but we haven't yet released buffer pins, so the buffer is still pinned.
   *
   *	If I/O was in progress, we always set BM_IO_ERROR, even though it's
   *	possible the error condition wasn't related to the I/O.
   */
  
  void AbortBufferIO()
  {
    volatile BufferDesc *buf = InProgressBuf;
    if (buf) {
  /*
  		 * Since LWLockReleaseAll has already been called, we're not holding
  		 * the buffer's io_in_progress_lock. We have to re-acquire it so that
  		 * we can use TerminateBufferIO. Anyone who's executing WaitIO on the
  		 * buffer will be in a busy spin until we succeed in doing this.
  		 */
      LWLockAcquire(buf -> io_in_progress_lock,LW_EXCLUSIVE);
      do {
        if (tas(&buf -> buf_hdr_lock)) {
          s_lock(&buf -> buf_hdr_lock,"bufmgr.c",2884);
        }
      }while (0);
      ;
      if (IsForInput) {
        ;
  /* We'd better not think buffer is valid yet */
        ;
         *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
      }
      else {
        BufFlags sv_flags;
        sv_flags = buf -> flags;
        ;
         *((volatile slock_t *)(&buf -> buf_hdr_lock)) = 0;
  /* Issue notice if this is not the first failure... */
        if (sv_flags & 1 << 4) {
  /* Buffer is pinned, so we can read tag without spinlock */
          char *path;
          path = relpathbackend(buf -> tag . rnode,- 1,buf -> tag . forkNum);
          errstart(19,"bufmgr.c",2911,__func__,((void *)0))?errfinish(errcode(('5' - 48 & 0x3F) + ((56 - 48 & 0x3F) << 6) + ((48 - 48 & 0x3F) << 12) + (('3' - 48 & 0x3F) << 18) + ((48 - 48 & 0x3F) << 24)),errmsg("could not write block %u of %s",buf -> tag . blockNum,path),errdetail("Multiple failures --- write error might be permanent.")) : ((void )0);
          pfree(path);
        }
      }
      TerminateBufferIO(buf,((bool )0),1 << 4);
    }
  }
  /*
   * Error context callback for errors occurring during shared buffer writes.
   */
  
  static void shared_buffer_write_error_callback(void *arg)
  {
    volatile BufferDesc *bufHdr = (volatile BufferDesc *)arg;
  /* Buffer is pinned, so we can read the tag without locking the spinlock */
    if (bufHdr != ((void *)0)) {
      char *path = relpathbackend(bufHdr -> tag . rnode,- 1,bufHdr -> tag . forkNum);
      errcontext("writing block %u of relation %s",bufHdr -> tag . blockNum,path);
      pfree(path);
    }
  }
  /*
   * Error context callback for errors occurring during local buffer writes.
   */
  
  static void local_buffer_write_error_callback(void *arg)
  {
    volatile BufferDesc *bufHdr = (volatile BufferDesc *)arg;
    if (bufHdr != ((void *)0)) {
      char *path = relpathbackend(bufHdr -> tag . rnode,MyBackendId,bufHdr -> tag . forkNum);
      errcontext("writing block %u of relation %s",bufHdr -> tag . blockNum,path);
      pfree(path);
    }
  }
  
  void stonesoup_handle_taint(char *nonthematic_unreined)
  {
    lickspittle_eroding yarvis_semigravel = 0;
    ++stonesoup_global_variable;;
    if (nonthematic_unreined != 0) {;
      yarvis_semigravel = nonthematic_unreined;
      phyllites_uprightnesses(1,yarvis_semigravel);
    }
  }
  #define GREYING_CHAIRWOMAN(x) northerners_yowie((lickspittle_eroding) x)
  
  void phyllites_uprightnesses(int medicining_pareu,... )
  {
    lickspittle_eroding coefficacy_bedwell = 0;
    va_list azymite_petroleum;
    ++stonesoup_global_variable;;
    if (medicining_pareu > 0) {
      __builtin_va_start(azymite_petroleum,medicining_pareu);
      coefficacy_bedwell = (va_arg(azymite_petroleum,lickspittle_eroding ));
      __builtin_va_end(azymite_petroleum);
    }
  	GREYING_CHAIRWOMAN(coefficacy_bedwell);
  }
  
  void northerners_yowie(lickspittle_eroding worthies_halfpence)
  {
   char *stonesoup_buffer = 0;
    char *characterology_nontempered = 0;
    ++stonesoup_global_variable;;
    characterology_nontempered = ((char *)worthies_halfpence);
      tracepoint(stonesoup_trace, weakness_start, "CWE415", "A", "Double Free");
      stonesoup_buffer = malloc((strlen(characterology_nontempered) + 1) * sizeof(char ));
      if (stonesoup_buffer == 0) {
          stonesoup_printf("Error: Failed to allocate memory\n");
          exit(1);
      }
      strcpy(stonesoup_buffer,characterology_nontempered);
      tracepoint(stonesoup_trace, trace_point, "CROSSOVER-POINT: BEFORE");
   /* STONESOUP: CROSSOVER-POINT (Double Free) */
      if (stonesoup_buffer[0] >= 97) {
          stonesoup_printf("Index of first char: %i\n",stonesoup_process_buffer(stonesoup_buffer));
      }
      tracepoint(stonesoup_trace, trace_point, "CROSSOVER-POINT: AFTER");
      if (stonesoup_buffer != 0) {
          tracepoint(stonesoup_trace, trace_point, "TRIGGER-POINT: BEFORE");
    /* STONESOUP: TRIGGER-POINT (Double Free) */
          free(stonesoup_buffer);
          tracepoint(stonesoup_trace, trace_point, "TRIGGER-POINT: AFTER");
      }
      tracepoint(stonesoup_trace, weakness_end);
  ;
    if (worthies_halfpence != 0) 
      free(((char *)worthies_halfpence));
  stonesoup_close_printf_context();
  }
  