On Thu, Aug 25, 2022 at 01:55:06PM +0200, Pankaj Raghav wrote:

On Thu, Aug 25, 2022 at 01:48:43PM +0200, Pankaj Raghav wrote:

quoted

On Wed, Aug 24, 2022 at 01:14:40PM -0700, Keith Busch wrote:

quoted

 
-static bool __sbq_wake_up(struct sbitmap_queue *sbq)
+static bool __sbq_wake_up(struct sbitmap_queue *sbq, int *nr)
 {
 	struct sbq_wait_state *ws;
-	unsigned int wake_batch;
-	int wait_cnt;
+	int wake_batch, wait_cnt, sub, cur;
 
 	ws = sbq_wake_ptr(sbq);
 	if (!ws)
 		return false;
 
-	wait_cnt = atomic_dec_return(&ws->wait_cnt);
+	wake_batch = READ_ONCE(sbq->wake_batch);
+	do {
+		cur = atomic_read(&ws->wait_cnt);

I think the above statement is not needed if we use atomic_try_cmpxchg
as the old value is updated in that function itself.
https://docs.kernel.org/staging/index.html?highlight=atomic_try_cmpxchg#atomic-types

I mean after moving the cur = atomic_read(..) above the do statement:

wake_batch = READ_ONCE(sbq->wake_batch);
cur = atomic_read(&ws->wait_cnt);
do {
	sub = min3(wake_batch, *nr, cur);
	wait_cnt = cur - sub;
} while (!atomic_try_cmpxchg(&ws->wait_cnt, &cur, wait_cnt));

Yeah, that's a good change. I'll fix it up.