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/*-------------------------------------------------------------------------
*
* pmsignal.c
* routines for signaling the postmaster from its child processes
*
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/pmsignal.c,v 1.13 2004/02/08 22:28:56 neilc Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "miscadmin.h"
#include "storage/pmsignal.h"
#include "storage/shmem.h"
/*
* The postmaster is signaled by its children by sending SIGUSR1. The
* specific reason is communicated via flags in shared memory. We keep
* a boolean flag for each possible "reason", so that different reasons
* can be signaled by different backends at the same time. (However,
* if the same reason is signaled more than once simultaneously, the
* postmaster will observe it only once.)
*
* The flags are actually declared as "volatile sig_atomic_t" for maximum
* portability. This should ensure that loads and stores of the flag
* values are atomic, allowing us to dispense with any explicit locking.
*/
static volatile sig_atomic_t *PMSignalFlags;
/*
* PMSignalInit - initialize during shared-memory creation
*/
void
PMSignalInit(void)
{
bool found;
PMSignalFlags = (sig_atomic_t *)
ShmemInitStruct("PMSignalFlags",NUM_PMSIGNALS * sizeof(sig_atomic_t),&found);
if (!found)
MemSet(PMSignalFlags, 0, NUM_PMSIGNALS * sizeof(sig_atomic_t));
}
/*
* SendPostmasterSignal - signal the postmaster from a child process
*/
void
SendPostmasterSignal(PMSignalReason reason)
{
/* If called in a standalone backend, do nothing */
if (!IsUnderPostmaster)
return;
/* Atomically set the proper flag */
PMSignalFlags[reason] = true;
/* Send signal to postmaster */
kill(PostmasterPid, SIGUSR1);
}
/*
* CheckPostmasterSignal - check to see if a particular reason has been
* signaled, and clear the signal flag. Should be called by postmaster
* after receiving SIGUSR1.
*/
bool
CheckPostmasterSignal(PMSignalReason reason)
{
/* Careful here --- don't clear flag if we haven't seen it set */
if (PMSignalFlags[reason])
{
PMSignalFlags[reason] = false;
return true;
}
return false;
}
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