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/*--------------------------------------------------------------------
* Symbols referenced in this file:
* - proc_exit_inprogress
* - proc_exit
*--------------------------------------------------------------------
*/
/*-------------------------------------------------------------------------
*
* 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) 1996-2023, 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 <signal.h>
#include <unistd.h>
#include <sys/stat.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"
/*
* 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...
*/
__thread bool proc_exit_inprogress = false;
/*
* Set when shmem_exit() is in progress.
*/
/*
* This flag tracks whether we've called atexit() in the current process
* (or in the parent postmaster).
*/
/* local functions */
static void proc_exit_prepare(int code);
/* ----------------------------------------------------------------
* 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;
};
/* ----------------------------------------------------------------
* 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) { printf("Terminating process due to FATAL error\n"); exit(1); }
/*
* 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.
*/
/* ------------------
* 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.
* ------------------
*/
/* ----------------------------------------------------------------
* 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.
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* on_proc_exit
*
* this function adds a callback function to the list of
* functions invoked by proc_exit(). -cim 2/6/90
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* before_shmem_exit
*
* Register early callback to perform user-level cleanup,
* e.g. transaction abort, before we begin shutting down
* low-level subsystems.
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* 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.
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* cancel_before_shmem_exit
*
* this function removes a previously-registered before_shmem_exit
* callback. We only look at the latest entry for removal, as we
* expect callers to add and remove temporary before_shmem_exit
* callbacks in strict LIFO order.
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* 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...
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* check_on_shmem_exit_lists_are_empty
*
* Debugging check that no shmem cleanup handlers have been registered
* prematurely in the current process.
* ----------------------------------------------------------------
*/
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