Handle EACCES errors from kevent() better.

macdice · macdice · commit 47522ee00ddb · 2020-10-15T18:38:03.000+13:00
While registering for postmaster exit events, we have to handle a couple of edge cases where the postmaster is already gone. Commit 815c2f0 missed one: EACCES must surely imply that PostmasterPid no longer belongs to our postmaster process (or alternatively an unexpected permissions model has been imposed on us). Like ESRCH, this should be treated as a WL_POSTMASTER_DEATH event, rather than being raised with ereport(). No known problems reported in the wild. Per code review from Tom Lane. Back-patch to 13. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/3624029.1602701929%40sss.pgh.pa.us
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
@@ -1085,7 +1085,8 @@ WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events)
 
 	if (rc < 0)
 	{
-		if (event->events == WL_POSTMASTER_DEATH && errno == ESRCH)
+		if (event->events == WL_POSTMASTER_DEATH &&
+			(errno == ESRCH || errno == EACCES))
 			set->report_postmaster_not_running = true;
 		else
 			ereport(ERROR,

Original file line number	Diff line number	Diff line change
`@@ -1085,7 +1085,8 @@ WaitEventAdjustKqueue(WaitEventSet set, WaitEvent event, int old_events)`
`1085`	`1085`
`1086`	`1086`	`if (rc < 0)`
`1087`	`1087`	`{`
`1088`		`- if (event->events == WL_POSTMASTER_DEATH && errno == ESRCH)`
	`1088`	`+ if (event->events == WL_POSTMASTER_DEATH &&`
	`1089`	`+ (errno == ESRCH \|\| errno == EACCES))`
`1089`	`1090`	`set->report_postmaster_not_running = true;`
`1090`	`1091`	`else`
`1091`	`1092`	`ereport(ERROR,`