From 5a26c7b310b629f8893483cc3cce5bbfa7879115 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Thu, 12 Jan 2023 15:04:08 +1300
Subject: [PATCH] Refactor DetermineSleepTime() to use milliseconds.

Since we're not using select() anymore, we don't need to bother with
struct timeval.  We can work directly in milliseconds, which the latch
API wants.

Discussion: https://postgr.es/m/CA%2BhUKG%2BZ-HpOj1JsO9eWUP%2Bar7npSVinsC_npxSy%2BjdOMsx%3DGg%40mail.gmail.com
---
 src/backend/postmaster/postmaster.c | 57 +++++++++--------------------
 1 file changed, 18 insertions(+), 39 deletions(-)

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index ac0102b486..9cedc1b9f0 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -1586,7 +1586,7 @@ checkControlFile(void)
 }
 
 /*
- * Determine how long should we let ServerLoop sleep.
+ * Determine how long should we let ServerLoop sleep, in milliseconds.
  *
  * In normal conditions we wait at most one minute, to ensure that the other
  * background tasks handled by ServerLoop get done even when no requests are
@@ -1594,8 +1594,8 @@ checkControlFile(void)
  * we don't actually sleep so that they are quickly serviced.  Other exception
  * cases are as shown in the code.
  */
-static void
-DetermineSleepTime(struct timeval *timeout)
+static int
+DetermineSleepTime(void)
 {
 	TimestampTz next_wakeup = 0;
 
@@ -1608,26 +1608,20 @@ DetermineSleepTime(struct timeval *timeout)
 	{
 		if (AbortStartTime != 0)
 		{
+			int			seconds;
+
 			/* time left to abort; clamp to 0 in case it already expired */
-			timeout->tv_sec = SIGKILL_CHILDREN_AFTER_SECS -
+			seconds = SIGKILL_CHILDREN_AFTER_SECS -
 				(time(NULL) - AbortStartTime);
-			timeout->tv_sec = Max(timeout->tv_sec, 0);
-			timeout->tv_usec = 0;
+
+			return Max(seconds * 1000, 0);
 		}
 		else
-		{
-			timeout->tv_sec = 60;
-			timeout->tv_usec = 0;
-		}
-		return;
+			return 60 * 1000;
 	}
 
 	if (StartWorkerNeeded)
-	{
-		timeout->tv_sec = 0;
-		timeout->tv_usec = 0;
-		return;
-	}
+		return 0;
 
 	if (HaveCrashedWorker)
 	{
@@ -1665,26 +1659,14 @@ DetermineSleepTime(struct timeval *timeout)
 
 	if (next_wakeup != 0)
 	{
-		long		secs;
-		int			microsecs;
-
-		TimestampDifference(GetCurrentTimestamp(), next_wakeup,
-							&secs, &microsecs);
-		timeout->tv_sec = secs;
-		timeout->tv_usec = microsecs;
-
-		/* Ensure we don't exceed one minute */
-		if (timeout->tv_sec > 60)
-		{
-			timeout->tv_sec = 60;
-			timeout->tv_usec = 0;
-		}
-	}
-	else
-	{
-		timeout->tv_sec = 60;
-		timeout->tv_usec = 0;
+		/* Ensure we don't exceed one minute, or go under 0. */
+		return Max(0,
+				   Min(60 * 1000,
+					   TimestampDifferenceMilliseconds(GetCurrentTimestamp(),
+													   next_wakeup)));
 	}
+
+	return 60 * 1000;
 }
 
 /*
@@ -1743,12 +1725,9 @@ ServerLoop(void)
 	for (;;)
 	{
 		time_t		now;
-		struct timeval timeout;
-
-		DetermineSleepTime(&timeout);
 
 		nevents = WaitEventSetWait(pm_wait_set,
-								   timeout.tv_sec * 1000 + timeout.tv_usec / 1000,
+								   DetermineSleepTime(),
 								   events,
 								   lengthof(events),
 								   0 /* postmaster posts no wait_events */ );