Quelle  pmsignal.h

/*-------------------------------------------------------------------------
 *
 * 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 */