1 files changed, 86 insertions, 0 deletions
diff --git a/src/backend/storage/ipc/pmsignal.c b/src/backend/storage/ipc/pmsignal.c
new file mode 100644
index 00000000000..38c5d730c7f
--- /dev/null
+++ b/src/backend/storage/ipc/pmsignal.c
@@ -0,0 +1,86 @@
+/*-------------------------------------------------------------------------
+ *
+ * pmsignal.c
+ *	  routines for signaling the postmaster from its child processes
+ *
+ *
+ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/pmsignal.c,v 1.1 2001/11/04 19:55:31 tgl 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)
+{
+	/* Should be called only once */
+	Assert(!PMSignalFlags);
+
+	PMSignalFlags = (sig_atomic_t *)
+		ShmemAlloc(NUM_PMSIGNALS * sizeof(sig_atomic_t));
+
+	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 (assume it is our direct parent) */
+	kill(getppid(), 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;
+}