Hi, it seems we can release spinlock twice in
/src/backend/storage/ipc/procsignal.c file, method ProcSignalInit.
void
ProcSignalInit(bool cancel_key_valid, int32 cancel_key)
{
ProcSignalSlot *slot;
uint64 barrier_generation;
..............................................................................
slot = &ProcSignal->psh_slot[MyProcNumber];
/* sanity check */
SpinLockAcquire(&slot->pss_mutex);
if (pg_atomic_read_u32(&slot->pss_pid) != 0)
{
*SpinLockRelease(&slot->pss_mutex);*
elog(LOG, "process %d taking over ProcSignal slot %d, but it's
not empty",
MyProcPid, MyProcNumber);
}
/* Clear out any leftover signal reasons */
MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS *
sizeof(sig_atomic_t));
......................
slot->pss_cancel_key_valid = cancel_key_valid;
slot->pss_cancel_key = cancel_key;
pg_atomic_write_u32(&slot->pss_pid, MyProcPid);
*SpinLockRelease(&slot->pss_mutex);*
First in the if clause, second near the end of function. Such behavior
can lead to unpredictable concurrent issues.
In applied patch I removed spinlock release in if clause.
From ece7b5d6bf16111ad388fcb47ed9fd7572ef151e Mon Sep 17 00:00:00 2001
From: Maksim Melnikov <m.melni...@postgrespro.ru>
Date: Tue, 25 Feb 2025 22:22:36 +0300
Subject: [PATCH] Spinlock can be released twice in procsignal.c
---
src/backend/storage/ipc/procsignal.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index 7401b6e625..ae4cc0873a 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -178,7 +178,6 @@ ProcSignalInit(bool cancel_key_valid, int32 cancel_key)
SpinLockAcquire(&slot->pss_mutex);
if (pg_atomic_read_u32(&slot->pss_pid) != 0)
{
- SpinLockRelease(&slot->pss_mutex);
elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
MyProcPid, MyProcNumber);
}
--
2.43.0
