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/*-------------------------------------------------------------------------
*
* 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) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/ipc.c,v 1.100 2008/01/01 19:45:51 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include <sys/stat.h>
#include "miscadmin.h"
#ifdef PROFILE_PID_DIR
#include "postmaster/autovacuum.h"
#endif
#include "storage/ipc.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;
/* ----------------------------------------------------------------
* exit() handling stuff
*
* These functions are in generally the same spirit as atexit(2),
* 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
static struct ONEXIT
{
void (*function) (int code, Datum arg);
Datum arg;
} on_proc_exit_list[MAX_ON_EXITS], on_shmem_exit_list[MAX_ON_EXITS];
static int on_proc_exit_index,
on_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
* ----------------------------------------------------------------
*/
void
proc_exit(int code)
{
/*
* 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;
elog(DEBUG3, "proc_exit(%d)", code);
/* do our shared memory exits first */
shmem_exit(code);
/*
* call all the callbacks registered before calling exit().
*
* 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);
elog(DEBUG3, "exit(%d)", 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.
*/
char gprofDirName[32];
if (IsAutoVacuumWorkerProcess())
snprintf(gprofDirName, 32, "gprof/avworker");
else
snprintf(gprofDirName, 32, "gprof/%d", (int) getpid());
mkdir("gprof", 0777);
mkdir(gprofDirName, 0777);
chdir(gprofDirName);
}
#endif
exit(code);
}
/* ------------------
* 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.
* ------------------
*/
void
shmem_exit(int code)
{
elog(DEBUG3, "shmem_exit(%d)", code);
/*
* call all the registered callbacks.
*
* As with proc_exit(), we remove each callback from the list before
* calling it, to avoid infinite loop in case of error.
*/
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;
}
/* ----------------------------------------------------------------
* 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(void (*function) (int code, Datum arg), 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;
}
/* ----------------------------------------------------------------
* on_shmem_exit
*
* this function adds a callback function to the list of
* functions invoked by shmem_exit(). -cim 2/6/90
* ----------------------------------------------------------------
*/
void
on_shmem_exit(void (*function) (int code, Datum arg), 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;
}
/* ----------------------------------------------------------------
* 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)
{
on_shmem_exit_index = 0;
on_proc_exit_index = 0;
}
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