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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2021-01-06 22:02:35 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2021-01-06 22:09:16 -0500 |
| commit | 9486e7b666fd113f043d5f091fd42bc1ef72acd8 (patch) | |
| tree | 84e5d5a84a515b8ee2c9e14308b2999ac6727633 /src/backend/utils/misc/timeout.c | |
| parent | 55fe26a4b580b17d721c5accb842cc6a08295273 (diff) | |
| download | postgresql-9486e7b666fd113f043d5f091fd42bc1ef72acd8.tar.gz postgresql-9486e7b666fd113f043d5f091fd42bc1ef72acd8.zip | |
Improve commentary in timeout.c.
On re-reading I realized that I'd missed one race condition in the new
timeout code. It's safe, but add a comment explaining it.
Discussion: https://postgr.es/m/CA+hUKG+o6pbuHBJSGnud=TadsuXySWA7CCcPgCt2QE9F6_4iHQ@mail.gmail.com
Diffstat (limited to 'src/backend/utils/misc/timeout.c')
| -rw-r--r-- | src/backend/utils/misc/timeout.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/src/backend/utils/misc/timeout.c b/src/backend/utils/misc/timeout.c index 88139ab82b6..95a273d9cfb 100644 --- a/src/backend/utils/misc/timeout.c +++ b/src/backend/utils/misc/timeout.c @@ -307,7 +307,14 @@ schedule_alarm(TimestampTz now) * signal is still coming. * * Other race conditions involved with setting/checking signal_pending - * are okay, for the reasons described above. + * are okay, for the reasons described above. One additional point is + * that the signal handler could fire after we set signal_due_at, but + * still before the setitimer() call. Then the handler could + * overwrite signal_due_at with a value it computes, which will be the + * same as or perhaps later than what we just computed. After we + * perform setitimer(), the net effect would be that signal_due_at + * gives a time later than when the interrupt will really happen; + * which is a safe situation. */ signal_due_at = nearest_timeout; signal_pending = true; |