pmsignal.h

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/*-------------------------------------------------------------------------
 *
 * pmsignal.h
 *    routines for signaling between the postmaster and its child processes
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/pmsignal.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PMSIGNAL_H
#define PMSIGNAL_H
 
#include <signal.h>
 
#ifdef HAVE_SYS_PRCTL_H
#include "sys/prctl.h"
#endif
 
#ifdef HAVE_SYS_PROCCTL_H
#include "sys/procctl.h"
#endif
 
/*
 * Reasons for signaling the postmaster.  We can cope with simultaneous
 * signals for different reasons.  If the same reason is signaled multiple
 * times in quick succession, however, the postmaster is likely to observe
 * only one notification of it.  This is okay for the present uses.
 */
typedef enum
{
    PMSIGNAL_RECOVERY_STARTED,  /* recovery has started */
    PMSIGNAL_RECOVERY_CONSISTENT,   /* recovery has reached consistent state */
    PMSIGNAL_BEGIN_HOT_STANDBY, /* begin Hot Standby */
    PMSIGNAL_ROTATE_LOGFILE,    /* send SIGUSR1 to syslogger to rotate logfile */
    PMSIGNAL_START_AUTOVAC_LAUNCHER,    /* start an autovacuum launcher */
    PMSIGNAL_START_AUTOVAC_WORKER,  /* start an autovacuum worker */
    PMSIGNAL_BACKGROUND_WORKER_CHANGE,  /* background worker state change */
    PMSIGNAL_START_WALRECEIVER, /* start a walreceiver */
    PMSIGNAL_ADVANCE_STATE_MACHINE, /* advance postmaster's state machine */
    PMSIGNAL_XLOG_IS_SHUTDOWN,  /* ShutdownXLOG() completed */
} PMSignalReason;
 
#define NUM_PMSIGNALS (PMSIGNAL_XLOG_IS_SHUTDOWN+1)
 
/*
 * Reasons why the postmaster would send SIGQUIT to its children.
 */
typedef enum
{
    PMQUIT_NOT_SENT = 0,        /* postmaster hasn't sent SIGQUIT */
    PMQUIT_FOR_CRASH,           /* some other backend bought the farm */
    PMQUIT_FOR_STOP,            /* immediate stop was commanded */
} QuitSignalReason;
 
/* PMSignalData is an opaque struct, details known only within pmsignal.c */
typedef struct PMSignalData PMSignalData;
 
#ifdef EXEC_BACKEND
extern PGDLLIMPORT volatile PMSignalData *PMSignalState;
#endif
 
/*
 * prototypes for functions in pmsignal.c
 */
extern Size PMSignalShmemSize(void);
extern void PMSignalShmemInit(void);
extern void SendPostmasterSignal(PMSignalReason reason);
extern bool CheckPostmasterSignal(PMSignalReason reason);
extern void SetQuitSignalReason(QuitSignalReason reason);
extern QuitSignalReason GetQuitSignalReason(void);
extern void MarkPostmasterChildSlotAssigned(int slot);
extern bool MarkPostmasterChildSlotUnassigned(int slot);
extern bool IsPostmasterChildWalSender(int slot);
extern void RegisterPostmasterChildActive(void);
extern void MarkPostmasterChildWalSender(void);
extern bool PostmasterIsAliveInternal(void);
extern void PostmasterDeathSignalInit(void);
 
 
/*
 * Do we have a way to ask for a signal on parent death?
 *
 * If we do, pmsignal.c will set up a signal handler, that sets a flag when
 * the parent dies.  Checking the flag first makes PostmasterIsAlive() a lot
 * cheaper in usual case that the postmaster is alive.
 */
#if (defined(HAVE_SYS_PRCTL_H) && defined(PR_SET_PDEATHSIG)) || \
    (defined(HAVE_SYS_PROCCTL_H) && defined(PROC_PDEATHSIG_CTL))
#define USE_POSTMASTER_DEATH_SIGNAL
#endif
 
#ifdef USE_POSTMASTER_DEATH_SIGNAL
extern PGDLLIMPORT volatile sig_atomic_t postmaster_possibly_dead;
 
static inline bool
PostmasterIsAlive(void)
{
    if (likely(!postmaster_possibly_dead))
        return true;
    return PostmasterIsAliveInternal();
}
#else
#define PostmasterIsAlive() PostmasterIsAliveInternal()
#endif
 
#endif                          /* PMSIGNAL_H */