Handle EACCES errors from kevent() better.

While registering for postmaster exit events, we have to handle a couple
of edge cases where the postmaster is already gone.  Commit 815c2f09
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
index 256cc60a24292aba47b06977f29fbd52a5845ee3..dcf85c906373d78d566513f7dd2eeec04b5dd954 100644 (file)
--- 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,