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Unset MyBEEntry, making elog.c's call to pgstat_get_my_query_id() safe.

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Previously log messages late during shutdown could end up using either another
backend's PgBackendStatus (multi user) or segfault (single user) because
pgstat_get_my_query_id()'s check for !MyBEEntry didn't filter out use after
pgstat_beshutdown_hook().

This became a bug in 4f0b0966c86, but was a bit fishy before. But given
there's no known problematic cases before 14, it doesn't seem worth
backpatching further.

Also fixes a wrong filename in a comment, introduced in e1025044.

Reported-By: Andres Freund <andres@anarazel.de>
Reviewed-By: Julien Rouhaud <rjuju123@gmail.com>
Discussion: https://postgr.es/m/Julien Rouhaud <rjuju123@gmail.com>
Backpatch: 14-
This commit is contained in:
Andres Freund 2021-08-19 04:59:06 -07:00
parent e191564665
commit 18914f24ec
1 changed files with 4 additions and 1 deletions
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5
src/backend/utils/activity/backend_status.c
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@ -46,7 +46,7 @@ bool pgstat_track_activities = false;
int pgstat_track_activity_query_size = 1024; int pgstat_track_activity_query_size = 1024;
/* exposed so that progress.c can access it */ /* exposed so that backend_progress.c can access it */
PgBackendStatus *MyBEEntry = NULL; PgBackendStatus *MyBEEntry = NULL;
@ -469,6 +469,9 @@ pgstat_beshutdown_hook(int code, Datum arg)
beentry->st_procpid = 0; /* mark invalid */ beentry->st_procpid = 0; /* mark invalid */
PGSTAT_END_WRITE_ACTIVITY(beentry); PGSTAT_END_WRITE_ACTIVITY(beentry);
/* so that functions can check if backend_status.c is up via MyBEEntry */
MyBEEntry = NULL;
} }
/* /*