1 files changed, 105 insertions, 0 deletions
diff --git a/src/include/storage/pmsignal.h b/src/include/storage/pmsignal.h
new file mode 100644
index 0000000..8ed4d87
--- /dev/null
+++ b/src/include/storage/pmsignal.h
@@ -0,0 +1,105 @@
+/*-------------------------------------------------------------------------
+ *
+ * pmsignal.h
+ *	  routines for signaling between the postmaster and its child processes
+ *
+ *
+ * Portions Copyright (c) 1996-2021, 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_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 */
+
+	NUM_PMSIGNALS				/* Must be last value of enum! */
+} PMSignalReason;
+
+/*
+ * 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;
+
+/*
+ * 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 int	AssignPostmasterChildSlot(void);
+extern bool ReleasePostmasterChildSlot(int slot);
+extern bool IsPostmasterChildWalSender(int slot);
+extern void MarkPostmasterChildActive(void);
+extern void MarkPostmasterChildInactive(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 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 */