At Mon, 02 Nov 2020 17:25:04 +0900 (JST), Kyotaro Horiguchi
<horikyota....@gmail.com> wrote in
> I called SetLatch() during WaitLatch(NULL, ) but that doesn't fire
> WL_LATCH_SET event for me on Windows. (I got it fired on Linux..) On
> Windows, the latch is detected after exiting the WaitLatch()
> call. Seems like MyLatch of waiter is different from
> peerPGPROC->procLatch. And... an update for Visual Studio broke my
> environment... I will investigate this further but everything feel
> cumbersome on Windows...
I managed to reproduce the issue. FWIW the attached modifies
pg_backend_pid() to call "WaitLatch(NULL," and
pg_terminate_backend(pid) to SetLatch() to the process latch of the
pid. (It's minunderstanding that I could reproduce this on Linux.)
Session A:
=# select pg_backend_pid(); -- sleeps for 10 seconds.
Session B:
=# select pg_terminate_backend(A-pid);
[11628] LOG: server process (PID 14568) was terminated by exception 0xC0000005
[11628] DETAIL: Failed process was running: select pg_backend_pid();
[11628] HINT: See C include file "ntstatus.h" for a description of the
hexadecimal value.
[11628] LOG: terminating any other active server processes
[2948] WARNING: terminating connection because of crash of another server
process
2
With the fix patch, it changes to:
[16632] LOG: FALSE LATCH: 0000000000000000
rebards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index 24d44c98..e900bd3c 100644
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -1845,6 +1845,8 @@ WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
occurred_events++;
returned_events++;
}
+ else if (!set->latch)
+ elog(LOG, "FALSE LATCH: %p", set->latch);
}
else if (cur_event->events == WL_POSTMASTER_DEATH)
{
diff --git a/src/backend/storage/ipc/signalfuncs.c b/src/backend/storage/ipc/signalfuncs.c
index d822e82c..b7340bf4 100644
--- a/src/backend/storage/ipc/signalfuncs.c
+++ b/src/backend/storage/ipc/signalfuncs.c
@@ -134,7 +134,13 @@ pg_cancel_backend(PG_FUNCTION_ARGS)
Datum
pg_terminate_backend(PG_FUNCTION_ARGS)
{
- int r = pg_signal_backend(PG_GETARG_INT32(0), SIGTERM);
+ int r = 0;
+ PGPROC *p = BackendPidGetProc(PG_GETARG_INT32(0));
+
+ if (p)
+ SetLatch(&p->procLatch);
+
+ PG_RETURN_BOOL(false);
if (r == SIGNAL_BACKEND_NOSUPERUSER)
ereport(ERROR,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index a210fc93..1e2b97a9 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -960,6 +960,9 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
Datum
pg_backend_pid(PG_FUNCTION_ARGS)
{
+ WaitLatch(MyLatch, WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, 1, WAIT_EVENT_RECOVERY_PAUSE);
+ WaitLatch(NULL, WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, 10000, WAIT_EVENT_RECOVERY_PAUSE);
+
PG_RETURN_INT32(MyProcPid);
}
