text: /*-------------------------------------------------------------------------
   *
   * ipc.c
   *	  POSTGRES inter-process communication definitions.
   *
   * This file is misnamed, as it no longer has much of anything directly
   * to do with IPC.  The functionality here is concerned with managing
   * exit-time cleanup for either a postmaster or a backend.
   *
   *
   * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/storage/ipc/ipc.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  #include <mcheck.h>
  #include <signal.h>
  #include <unistd.h>
  #include <sys/stat.h>
  
  #include "cdb/cdbdisp.h"
  #include "cdb/ml_ipc.h"
  #include "libpq/pqsignal.h"
  #include "miscadmin.h"
  #ifdef PROFILE_PID_DIR
  #include "postmaster/autovacuum.h"
  #endif
  #include "storage/dsm.h"
  #include "storage/ipc.h"
  #include "tcop/tcopprot.h"
  
  /* [williamcliu] */
  #include "tdb/session_processor.h"
  #include "tdb/storage_param.h"
  #include "tdb/timestamp_transaction/http.h"
  
  /*
   * This flag is set during proc_exit() to change ereport()'s behavior,
   * so that an ereport() from an on_proc_exit routine cannot get us out
   * of the exit procedure.  We do NOT want to go back to the idle loop...
   */
  bool		proc_exit_inprogress = false;
  
  /*
   * This flag tracks whether we've called atexit() in the current process
   * (or in the parent postmaster).
   */
  static bool atexit_callback_setup = false;
  
  
  /* ----------------------------------------------------------------
   *						exit() handling stuff
   *
   * These functions are in generally the same spirit as atexit(),
   * but provide some additional features we need --- in particular,
   * we want to register callbacks to invoke when we are disconnecting
   * from a broken shared-memory context but not exiting the postmaster.
   *
   * Callback functions can take zero, one, or two args: the first passed
   * arg is the integer exitcode, the second is the Datum supplied when
   * the callback was registered.
   * ----------------------------------------------------------------
   */
  
  #define MAX_ON_EXITS 20
  
  struct ONEXIT
  {
  	pg_on_exit_callback function;
  	Datum		arg;
  };
  
  static struct ONEXIT on_proc_exit_list[MAX_ON_EXITS];
  static struct ONEXIT on_shmem_exit_list[MAX_ON_EXITS];
  static struct ONEXIT before_shmem_exit_list[MAX_ON_EXITS];
  
  static int	on_proc_exit_index,
  			on_shmem_exit_index,
  			before_shmem_exit_index;
  
  
  /* ----------------------------------------------------------------
   *		proc_exit
   *
   *		this function calls all the callbacks registered
   *		for it (to free resources) and then calls exit.
   *
   *		This should be the only function to call exit().
   *		-cim 2/6/90
   *
   *		Unfortunately, we can't really guarantee that add-on code
   *		obeys the rule of not calling exit() directly.  So, while
   *		this is the preferred way out of the system, we also register
   *		an atexit callback that will make sure cleanup happens.
   * ----------------------------------------------------------------
   */
  void
  proc_exit(int code)
  {
  	/* [williamcliu] Destroy storage mq if has built. */
  	SessionDestroyMQ();
      CloseToLts();
  	pqsignal(SIGALRM, SIG_IGN);
  
  	/* Clean up everything that must be cleaned up */
  	proc_exit_prepare(code);
  
  #ifdef PROFILE_PID_DIR
  	{
  		/*
  		 * If we are profiling ourself then gprof's mcleanup() is about to
  		 * write out a profile to ./gmon.out.  Since mcleanup() always uses a
  		 * fixed file name, each backend will overwrite earlier profiles. To
  		 * fix that, we create a separate subdirectory for each backend
  		 * (./gprof/pid) and 'cd' to that subdirectory before we exit() - that
  		 * forces mcleanup() to write each profile into its own directory.  We
  		 * end up with something like: $PGDATA/gprof/8829/gmon.out
  		 * $PGDATA/gprof/8845/gmon.out ...
  		 *
  		 * To avoid undesirable disk space bloat, autovacuum workers are
  		 * discriminated against: all their gmon.out files go into the same
  		 * subdirectory.  Without this, an installation that is "just sitting
  		 * there" nonetheless eats megabytes of disk space every few seconds.
  		 *
  		 * Note that we do this here instead of in an on_proc_exit() callback
  		 * because we want to ensure that this code executes last - we don't
  		 * want to interfere with any other on_proc_exit() callback.  For the
  		 * same reason, we do not include it in proc_exit_prepare ... so if
  		 * you are exiting in the "wrong way" you won't drop your profile in a
  		 * nice place.
  		 */
  		char		gprofDirName[32];
  
  		if (IsAutoVacuumWorkerProcess())
  			snprintf(gprofDirName, 32, "gprof/avworker");
  		else
  			snprintf(gprofDirName, 32, "gprof/%d", (int) getpid());
  
  		mkdir("gprof", S_IRWXU | S_IRWXG | S_IRWXO);
  		mkdir(gprofDirName, S_IRWXU | S_IRWXG | S_IRWXO);
  		chdir(gprofDirName);
  	}
  #endif
  
  	elog(DEBUG3, "exit(%d)", code);
  	if (am_kv_storage)
  		muntrace();
  	exit(code);
  }
  
  /*
   * Code shared between proc_exit and the atexit handler.  Note that in
   * normal exit through proc_exit, this will actually be called twice ...
   * but the second call will have nothing to do.
   */
  void
  proc_exit_prepare(int code)
  {
  	/*
  	 * If we came here from any critical section, we don't have safe way to
  	 * clean up shared memory or transaction state.  Though it's not a pleasant
  	 * solution, this is better than messing up database.  This is the least
  	 * desirable bail-out, and whenever you should see this situation, you
  	 * should consider to resolve the actual programming error.
  	 */
  	if (CritSectionCount > 0)
  		elog(PANIC, "process is dying from critical section");
  
  	/*
  	 * Once we set this flag, we are committed to exit.  Any ereport() will
  	 * NOT send control back to the main loop, but right back here.
  	 */
  	proc_exit_inprogress = true;
  
  	/*
  	 * Forget any pending cancel or die requests; we're doing our best to
  	 * close up shop already.  Note that the signal handlers will not set
  	 * these flags again, now that proc_exit_inprogress is set.
  	 */
  	InterruptPending = false;
  	ProcDiePending = false;
  	QueryCancelPending = false;
  	/* And let's just make *sure* we're not interrupted ... */
  	ImmediateInterruptOK = false;
  	InterruptHoldoffCount = 1;
  	CritSectionCount = 0;
  
  	/*
  	 * Also clear the error context stack, to prevent error callbacks from
  	 * being invoked by any elog/ereport calls made during proc_exit. Whatever
  	 * context they might want to offer is probably not relevant, and in any
  	 * case they are likely to fail outright after we've done things like
  	 * aborting any open transaction.  (In normal exit scenarios the context
  	 * stack should be empty anyway, but it might not be in the case of
  	 * elog(FATAL) for example.)
  	 */
  	error_context_stack = NULL;
  	/* For the same reason, reset debug_query_string before it's clobbered */
  	debug_query_string = NULL;
  
  	/*
  	* Make sure interconnect thread quit before shmem_exit() in FATAL case.
  	* Otherwise, shmem_exit() may free MemoryContex of MotionConns in connHtab unexpectedly;
  	*
  	* For example: PORTAL_MULTI_QUERY strategy doesn't bind estate with portal,
  	* so when fatal occurs, MotionConns of estate don't get removed through
  	* TeardownInterconnect(), but MemoryContex of these MotionConns are freed.
  	*
  	* It's ok to shutdown Interconnect background thread here, process is dying, no
  	* necessary to receive more motion data.
  	*/
  	WaitInterconnectQuit();
  
  	elog(DEBUG3, "proc_exit(%d)", code);
  
  	/* do our shared memory exits first */
  	shmem_exit(code);
  
  	elog(DEBUG3, "proc_exit(%d): %d callbacks to make",
  		 code, on_proc_exit_index);
  
  	/*
  	 * call all the registered callbacks.
  	 *
  	 * Note that since we decrement on_proc_exit_index each time, if a
  	 * callback calls ereport(ERROR) or ereport(FATAL) then it won't be
  	 * invoked again when control comes back here (nor will the
  	 * previously-completed callbacks).  So, an infinite loop should not be
  	 * possible.
  	 */
  	while (--on_proc_exit_index >= 0)
  		(*on_proc_exit_list[on_proc_exit_index].function) (code,
  								  on_proc_exit_list[on_proc_exit_index].arg);
  
  	on_proc_exit_index = 0;
  }
  
  /* ------------------
   * Run all of the on_shmem_exit routines --- but don't actually exit.
   * This is used by the postmaster to re-initialize shared memory and
   * semaphores after a backend dies horribly.  As with proc_exit(), we
   * remove each callback from the list before calling it, to avoid
   * infinite loop in case of error.
   * ------------------
   */
  void
  shmem_exit(int code)
  {
  	/*
  	 * Call before_shmem_exit callbacks.
  	 *
  	 * These should be things that need most of the system to still be up and
  	 * working, such as cleanup of temp relations, which requires catalog
  	 * access; or things that need to be completed because later cleanup steps
  	 * depend on them, such as releasing lwlocks.
  	 */
  	elog(DEBUG3, "shmem_exit(%d): %d before_shmem_exit callbacks to make",
  		 code, before_shmem_exit_index);
  	while (--before_shmem_exit_index >= 0)
  		(*before_shmem_exit_list[before_shmem_exit_index].function) (code,
  						before_shmem_exit_list[before_shmem_exit_index].arg);
  	before_shmem_exit_index = 0;
  
  	/*
  	 * Call dynamic shared memory callbacks.
  	 *
  	 * These serve the same purpose as late callbacks, but for dynamic shared
  	 * memory segments rather than the main shared memory segment.
  	 * dsm_backend_shutdown() has the same kind of progressive logic we use
  	 * for the main shared memory segment; namely, it unregisters each
  	 * callback before invoking it, so that we don't get stuck in an infinite
  	 * loop if one of those callbacks itself throws an ERROR or FATAL.
  	 *
  	 * Note that explicitly calling this function here is quite different from
  	 * registering it as an on_shmem_exit callback for precisely this reason:
  	 * if one dynamic shared memory callback errors out, the remaining
  	 * callbacks will still be invoked.  Thus, hard-coding this call puts it
  	 * equal footing with callbacks for the main shared memory segment.
  	 */
  	dsm_backend_shutdown();
  
  	/*
  	 * Call on_shmem_exit callbacks.
  	 *
  	 * These are generally releasing low-level shared memory resources.  In
  	 * some cases, this is a backstop against the possibility that the early
  	 * callbacks might themselves fail, leading to re-entry to this routine;
  	 * in other cases, it's cleanup that only happens at process exit.
  	 */
  	elog(DEBUG3, "shmem_exit(%d): %d on_shmem_exit callbacks to make",
  		 code, on_shmem_exit_index);
  	while (--on_shmem_exit_index >= 0)
  		(*on_shmem_exit_list[on_shmem_exit_index].function) (code,
  								on_shmem_exit_list[on_shmem_exit_index].arg);
  	on_shmem_exit_index = 0;
  }
  
  /* ----------------------------------------------------------------
   *		atexit_callback
   *
   *		Backstop to ensure that direct calls of exit() don't mess us up.
   *
   * Somebody who was being really uncooperative could call _exit(),
   * but for that case we have a "dead man switch" that will make the
   * postmaster treat it as a crash --- see pmsignal.c.
   * ----------------------------------------------------------------
   */
  static void
  atexit_callback(void)
  {
  	/* Clean up everything that must be cleaned up */
  	/* ... too bad we don't know the real exit code ... */
  	proc_exit_prepare(-1);
  }
  
  /* ----------------------------------------------------------------
   *		on_proc_exit
   *
   *		this function adds a callback function to the list of
   *		functions invoked by proc_exit().   -cim 2/6/90
   * ----------------------------------------------------------------
   */
  void
  on_proc_exit(pg_on_exit_callback function, Datum arg)
  {
  	if (on_proc_exit_index >= MAX_ON_EXITS)
  		ereport(FATAL,
  				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
  				 errmsg_internal("out of on_proc_exit slots")));
  
  	on_proc_exit_list[on_proc_exit_index].function = function;
  	on_proc_exit_list[on_proc_exit_index].arg = arg;
  
  	++on_proc_exit_index;
  
  	if (!atexit_callback_setup)
  	{
  		atexit(atexit_callback);
  		atexit_callback_setup = true;
  	}
  }
  
  /* ----------------------------------------------------------------
   *		before_shmem_exit
   *
   *		Register early callback to perform user-level cleanup,
   *		e.g. transaction abort, before we begin shutting down
   *		low-level subsystems.
   * ----------------------------------------------------------------
   */
  void
  before_shmem_exit(pg_on_exit_callback function, Datum arg)
  {
  	if (before_shmem_exit_index >= MAX_ON_EXITS)
  		ereport(FATAL,
  				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
  				 errmsg_internal("out of before_shmem_exit slots")));
  
  	before_shmem_exit_list[before_shmem_exit_index].function = function;
  	before_shmem_exit_list[before_shmem_exit_index].arg = arg;
  
  	++before_shmem_exit_index;
  
  	if (!atexit_callback_setup)
  	{
  		atexit(atexit_callback);
  		atexit_callback_setup = true;
  	}
  }
  
  /* ----------------------------------------------------------------
   *		on_shmem_exit
   *
   *		Register ordinary callback to perform low-level shutdown
   *		(e.g. releasing our PGPROC); run after before_shmem_exit
   *		callbacks and before on_proc_exit callbacks.
   * ----------------------------------------------------------------
   */
  void
  on_shmem_exit(pg_on_exit_callback function, Datum arg)
  {
  	if (on_shmem_exit_index >= MAX_ON_EXITS)
  		ereport(FATAL,
  				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
  				 errmsg_internal("out of on_shmem_exit slots")));
  
  	on_shmem_exit_list[on_shmem_exit_index].function = function;
  	on_shmem_exit_list[on_shmem_exit_index].arg = arg;
  
  	++on_shmem_exit_index;
  
  	if (!atexit_callback_setup)
  	{
  		atexit(atexit_callback);
  		atexit_callback_setup = true;
  	}
  }
  
  /* ----------------------------------------------------------------
   *		cancel_before_shmem_exit
   *
   *		this function removes a previously-registed before_shmem_exit
   *		callback.  For simplicity, only the latest entry can be
   *		removed.  (We could work harder but there is no need for
   *		current uses.)
   * ----------------------------------------------------------------
   */
  void
  cancel_before_shmem_exit(pg_on_exit_callback function, Datum arg)
  {
  	if (before_shmem_exit_index > 0 &&
  		before_shmem_exit_list[before_shmem_exit_index - 1].function
  		== function &&
  		before_shmem_exit_list[before_shmem_exit_index - 1].arg == arg)
  		--before_shmem_exit_index;
  }
  
  /* ----------------------------------------------------------------
   *		on_exit_reset
   *
   *		this function clears all on_proc_exit() and on_shmem_exit()
   *		registered functions.  This is used just after forking a backend,
   *		so that the backend doesn't believe it should call the postmaster's
   *		on-exit routines when it exits...
   * ----------------------------------------------------------------
   */
  void
  on_exit_reset(void)
  {
  	before_shmem_exit_index = 0;
  	on_shmem_exit_index = 0;
  	on_proc_exit_index = 0;
  	reset_on_dsm_detach();
  }
  