spinlock emulation: Fix bug when more than INT_MAX spinlocks are initialized.

anarazel · anarazel · commit 4d4ca24efe8e · 2020-06-17T12:50:54.000-07:00
Once the counter goes negative we ended up with spinlocks that errored out on first use (due to check in tas_sema). Author: Andres Freund Reviewed-By: Robert Haas Discussion: https://postgr.es/m/20200606023103.avzrctgv7476xj7i@alap3.anarazel.de Backpatch: 9.5-
diff --git a/src/backend/storage/lmgr/spin.c b/src/backend/storage/lmgr/spin.c
@@ -106,7 +106,7 @@ SpinlockSemaInit(void)
 void
 s_init_lock_sema(volatile slock_t *lock, bool nested)
 {
-	static int	counter = 0;
+	static uint32 counter = 0;
 
 	*lock = ((++counter) % NUM_SPINLOCK_SEMAPHORES) + 1;
 }

Original file line number	Diff line number	Diff line change
`@@ -106,7 +106,7 @@ SpinlockSemaInit(void)`
`106`	`106`	`void`
`107`	`107`	`s_init_lock_sema(volatile slock_t *lock, bool nested)`
`108`	`108`	`{`
`109`		`- static int counter = 0;`
	`109`	`+ static uint32 counter = 0;`
`110`	`110`
`111`	`111`	`*lock = ((++counter) % NUM_SPINLOCK_SEMAPHORES) + 1;`
`112`	`112`	`}`