Change ProcSendSignal() to take pgprocno.

Instead of referring to target backends by pid, use pgprocno.  This
means that we don't have to scan the ProcArray and we can drop some
special case code for dealing with the startup process.

Discussion: https://postgr.es/m/CA%2BhUKGLYRyDaneEwz5Uya_OgFLMx5BgJfkQSD%3Dq9HmwsfRRb-w%40mail.gmail.com
Reviewed-by: Soumyadeep Chakraborty <soumyadeep2007@gmail.com>
Reviewed-by: Ashwin Agrawal <ashwinstar@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>

1 files changed, 5 insertions, 45 deletions

diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index b7d9da0aa9f..d1d3cd0dc88 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -177,8 +177,6 @@ InitProcGlobal(void)
 	ProcGlobal->autovacFreeProcs = NULL;
 	ProcGlobal->bgworkerFreeProcs = NULL;
 	ProcGlobal->walsenderFreeProcs = NULL;
-	ProcGlobal->startupProc = NULL;
-	ProcGlobal->startupProcPid = 0;
 	ProcGlobal->startupBufferPinWaitBufId = -1;
 	ProcGlobal->walwriterLatch = NULL;
 	ProcGlobal->checkpointerLatch = NULL;
@@ -625,21 +623,6 @@ InitAuxiliaryProcess(void)
 }
 
 /*
- * Record the PID and PGPROC structures for the Startup process, for use in
- * ProcSendSignal().  See comments there for further explanation.
- */
-void
-PublishStartupProcessInformation(void)
-{
-	SpinLockAcquire(ProcStructLock);
-
-	ProcGlobal->startupProc = MyProc;
-	ProcGlobal->startupProcPid = MyProcPid;
-
-	SpinLockRelease(ProcStructLock);
-}
-
-/*
  * Used from bufmgr to share the value of the buffer that Startup waits on,
  * or to reset the value to "not waiting" (-1). This allows processing
  * of recovery conflicts for buffer pins. Set is made before backends look
@@ -1903,38 +1886,15 @@ ProcWaitForSignal(uint32 wait_event_info)
 }
 
 /*
- * ProcSendSignal - send a signal to a backend identified by PID
+ * ProcSendSignal - set the latch of a backend identified by pgprocno
  */
 void
-ProcSendSignal(int pid)
+ProcSendSignal(int pgprocno)
 {
-	PGPROC	   *proc = NULL;
+	if (pgprocno < 0 || pgprocno >= ProcGlobal->allProcCount)
+		elog(ERROR, "pgprocno out of range");
 
-	if (RecoveryInProgress())
-	{
-		SpinLockAcquire(ProcStructLock);
-
-		/*
-		 * Check to see whether it is the Startup process we wish to signal.
-		 * This call is made by the buffer manager when it wishes to wake up a
-		 * process that has been waiting for a pin in so it can obtain a
-		 * cleanup lock using LockBufferForCleanup(). Startup is not a normal
-		 * backend, so BackendPidGetProc() will not return any pid at all. So
-		 * we remember the information for this special case.
-		 */
-		if (pid == ProcGlobal->startupProcPid)
-			proc = ProcGlobal->startupProc;
-
-		SpinLockRelease(ProcStructLock);
-	}
-
-	if (proc == NULL)
-		proc = BackendPidGetProc(pid);
-
-	if (proc != NULL)
-	{
-		SetLatch(&proc->procLatch);
-	}
+	SetLatch(&ProcGlobal->allProcs[pgprocno].procLatch);
 }
 
 /*