text: /*-------------------------------------------------------------------------
   *
   * proc.h
   *	  per-process shared memory data structures
   *
   *
   * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * src/include/storage/proc.h
   *
   *-------------------------------------------------------------------------
   */
  #ifndef _PROC_H_
  #define _PROC_H_
  
  #include "access/xlogdefs.h"
  #include "lib/ilist.h"
  #include "storage/latch.h"
  #include "storage/lock.h"
  #include "storage/pg_sema.h"
  
  /*
   * Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds
   * for non-aborted subtransactions of its current top transaction.  These
   * have to be treated as running XIDs by other backends.
   *
   * We also keep track of whether the cache overflowed (ie, the transaction has
   * generated at least one subtransaction that didn't fit in the cache).
   * If none of the caches have overflowed, we can assume that an XID that's not
   * listed anywhere in the PGPROC array is not a running transaction.  Else we
   * have to look at pg_subtrans.
   */
  #define PGPROC_MAX_CACHED_SUBXIDS 64	/* XXX guessed-at value */
  
  struct XidCache
  {
  	TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS];
  };
  
  /* Flags for PGXACT->vacuumFlags */
  #define		PROC_IS_AUTOVACUUM	0x01	/* is it an autovac worker? */
  #define		PROC_IN_VACUUM		0x02	/* currently running lazy vacuum */
  #define		PROC_IN_ANALYZE		0x04	/* currently running analyze */
  #define		PROC_VACUUM_FOR_WRAPAROUND	0x08	/* set by autovac only */
  #define		PROC_IN_LOGICAL_DECODING	0x10	/* currently doing logical
  												 * decoding outside xact */
  
  /* flags reset at EOXact */
  #define		PROC_VACUUM_STATE_MASK \
  	(PROC_IN_VACUUM | PROC_IN_ANALYZE | PROC_VACUUM_FOR_WRAPAROUND)
  
  /*
   * We allow a small number of "weak" relation locks (AccesShareLock,
   * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure
   * rather than the main lock table.  This eases contention on the lock
   * manager LWLocks.  See storage/lmgr/README for additional details.
   */
  #define		FP_LOCK_SLOTS_PER_BACKEND 16
  
  /*
   * Each backend has a PGPROC struct in shared memory.  There is also a list of
   * currently-unused PGPROC structs that will be reallocated to new backends.
   *
   * links: list link for any list the PGPROC is in.  When waiting for a lock,
   * the PGPROC is linked into that lock's waitProcs queue.  A recycled PGPROC
   * is linked into ProcGlobal's freeProcs list.
   *
   * Note: twophase.c also sets up a dummy PGPROC struct for each currently
   * prepared transaction.  These PGPROCs appear in the ProcArray data structure
   * so that the prepared transactions appear to be still running and are
   * correctly shown as holding locks.  A prepared transaction PGPROC can be
   * distinguished from a real one at need by the fact that it has pid == 0.
   * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused,
   * but its myProcLocks[] lists are valid.
   */
  struct PGPROC
  {
  	/* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */
  	SHM_QUEUE	links;			/* list link if process is in a list */
  
  	PGSemaphoreData sem;		/* ONE semaphore to sleep on */
  	int			waitStatus;		/* STATUS_WAITING, STATUS_OK or STATUS_ERROR */
  
  	Latch		procLatch;		/* generic latch for process */
  
  	LocalTransactionId lxid;	/* local id of top-level transaction currently
  								 * being executed by this proc, if running;
  								 * else InvalidLocalTransactionId */
  	int			pid;			/* Backend's process ID; 0 if prepared xact */
  	int			pgprocno;
  
  	/* These fields are zero while a backend is still starting up: */
  	BackendId	backendId;		/* This backend's backend ID (if assigned) */
  	Oid			databaseId;		/* OID of database this backend is using */
  	Oid			roleId;			/* OID of role using this backend */
  
  	/*
  	 * While in hot standby mode, shows that a conflict signal has been sent
  	 * for the current transaction. Set/cleared while holding ProcArrayLock,
  	 * though not required. Accessed without lock, if needed.
  	 */
  	bool		recoveryConflictPending;
  
  	/* Info about LWLock the process is currently waiting for, if any. */
  	bool		lwWaiting;		/* true if waiting for an LW lock */
  	uint8		lwWaitMode;		/* lwlock mode being waited for */
  	dlist_node	lwWaitLink;		/* position in LW lock wait list */
  
  	/* Info about lock the process is currently waiting for, if any. */
  	/* waitLock and waitProcLock are NULL if not currently waiting. */
  	LOCK	   *waitLock;		/* Lock object we're sleeping on ... */
  	PROCLOCK   *waitProcLock;	/* Per-holder info for awaited lock */
  	LOCKMODE	waitLockMode;	/* type of lock we're waiting for */
  	LOCKMASK	heldLocks;		/* bitmask for lock types already held on this
  								 * lock object by this backend */
  
  	/*
  	 * Info to allow us to wait for synchronous replication, if needed.
  	 * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend.
  	 * syncRepState must not be touched except by owning process or WALSender.
  	 * syncRepLinks used only while holding SyncRepLock.
  	 */
  	XLogRecPtr	waitLSN;		/* waiting for this LSN or higher */
  	int			syncRepState;	/* wait state for sync rep */
  	SHM_QUEUE	syncRepLinks;	/* list link if process is in syncrep queue */
  
  	/*
  	 * All PROCLOCK objects for locks held or awaited by this backend are
  	 * linked into one of these lists, according to the partition number of
  	 * their lock.
  	 */
  	SHM_QUEUE	myProcLocks[NUM_LOCK_PARTITIONS];
  
  	struct XidCache subxids;	/* cache for subtransaction XIDs */
  
  	/* Per-backend LWLock.  Protects fields below. */
  	LWLock	   *backendLock;	/* protects the fields below */
  
  	/* Lock manager data, recording fast-path locks taken by this backend. */
  	uint64		fpLockBits;		/* lock modes held for each fast-path slot */
  	Oid			fpRelId[FP_LOCK_SLOTS_PER_BACKEND];		/* slots for rel oids */
  	bool		fpVXIDLock;		/* are we holding a fast-path VXID lock? */
  	LocalTransactionId fpLocalTransactionId;	/* lxid for fast-path VXID
  												 * lock */
  };
  
  /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */
  
  
  extern PGDLLIMPORT PGPROC *MyProc;
  extern PGDLLIMPORT struct PGXACT *MyPgXact;
  
  /*
   * Prior to PostgreSQL 9.2, the fields below were stored as part of the
   * PGPROC.  However, benchmarking revealed that packing these particular
   * members into a separate array as tightly as possible sped up GetSnapshotData
   * considerably on systems with many CPU cores, by reducing the number of
   * cache lines needing to be fetched.  Thus, think very carefully before adding
   * anything else here.
   */
  typedef struct PGXACT
  {
  	TransactionId xid;			/* id of top-level transaction currently being
  								 * executed by this proc, if running and XID
  								 * is assigned; else InvalidTransactionId */
  
  	TransactionId xmin;			/* minimal running XID as it was when we were
  								 * starting our xact, excluding LAZY VACUUM:
  								 * vacuum must not remove tuples deleted by
  								 * xid >= xmin ! */
  
  	uint8		vacuumFlags;	/* vacuum-related flags, see above */
  	bool		overflowed;
  	bool		delayChkpt;		/* true if this proc delays checkpoint start;
  								 * previously called InCommit */
  
  	uint8		nxids;
  } PGXACT;
  
  /*
   * There is one ProcGlobal struct for the whole database cluster.
   */
  typedef struct PROC_HDR
  {
  	/* Array of PGPROC structures (not including dummies for prepared txns) */
  	PGPROC	   *allProcs;
  	/* Array of PGXACT structures (not including dummies for prepared txns) */
  	PGXACT	   *allPgXact;
  	/* Length of allProcs array */
  	uint32		allProcCount;
  	/* Head of list of free PGPROC structures */
  	PGPROC	   *freeProcs;
  	/* Head of list of autovacuum's free PGPROC structures */
  	PGPROC	   *autovacFreeProcs;
  	/* Head of list of bgworker free PGPROC structures */
  	PGPROC	   *bgworkerFreeProcs;
  	/* WALWriter process's latch */
  	Latch	   *walwriterLatch;
  	/* Checkpointer process's latch */
  	Latch	   *checkpointerLatch;
  	/* Current shared estimate of appropriate spins_per_delay value */
  	int			spins_per_delay;
  	/* The proc of the Startup process, since not in ProcArray */
  	PGPROC	   *startupProc;
  	int			startupProcPid;
  	/* Buffer id of the buffer that Startup process waits for pin on, or -1 */
  	int			startupBufferPinWaitBufId;
  } PROC_HDR;
  
  extern PROC_HDR *ProcGlobal;
  
  extern PGPROC *PreparedXactProcs;
  
  /*
   * We set aside some extra PGPROC structures for auxiliary processes,
   * ie things that aren't full-fledged backends but need shmem access.
   *
   * Background writer, checkpointer and WAL writer run during normal operation.
   * Startup process and WAL receiver also consume 2 slots, but WAL writer is
   * launched only after startup has exited, so we only need 4 slots.
   */
  #define NUM_AUXILIARY_PROCS		4
  
  
  /* configurable options */
  extern int	DeadlockTimeout;
  extern int	StatementTimeout;
  extern int	LockTimeout;
  extern bool log_lock_waits;
  
  
  /*
   * Function Prototypes
   */
  extern int	ProcGlobalSemas(void);
  extern Size ProcGlobalShmemSize(void);
  extern void InitProcGlobal(void);
  extern void InitProcess(void);
  extern void InitProcessPhase2(void);
  extern void InitAuxiliaryProcess(void);
  
  extern void PublishStartupProcessInformation(void);
  extern void SetStartupBufferPinWaitBufId(int bufid);
  extern int	GetStartupBufferPinWaitBufId(void);
  
  extern bool HaveNFreeProcs(int n);
  extern void ProcReleaseLocks(bool isCommit);
  
  extern void ProcQueueInit(PROC_QUEUE *queue);
  extern int	ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable);
  extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus);
  extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock);
  extern void CheckDeadLock(void);
  extern bool IsWaitingForLock(void);
  extern void LockErrorCleanup(void);
  
  extern void ProcWaitForSignal(void);
  extern void ProcSendSignal(int pid);
  
  #endif   /* PROC_H */
  