From 767a65e9f31789d80e41edd03a802314905e8fbf Mon Sep 17 00:00:00 2001 From: Hao Xu Date: Sun, 12 Sep 2021 03:40:52 +0800 Subject: [PATCH] io-wq: fix potential race of acct->nr_workers Given max_worker is 1, and we currently have 1 running and it is exiting. There may be race like: io_wqe_enqueue worker1 no work there and timeout unlock(wqe->lock) ->insert work -->io_worker_exit lock(wqe->lock) ->if(!nr_workers) //it's still 1 unlock(wqe->lock) goto run_cancel lock(wqe->lock) nr_workers-- ->dec_running ->worker creation fails unlock(wqe->lock) We enqueued one work but there is no workers, causes hung. Signed-off-by: Hao Xu Signed-off-by: Jens Axboe --- fs/io-wq.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/io-wq.c b/fs/io-wq.c index a1685b40a4bf..3d4460df845c 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -176,7 +176,6 @@ static void io_worker_ref_put(struct io_wq *wq) static void io_worker_exit(struct io_worker *worker) { struct io_wqe *wqe = worker->wqe; - struct io_wqe_acct *acct = io_wqe_get_acct(worker); if (refcount_dec_and_test(&worker->ref)) complete(&worker->ref_done); @@ -186,7 +185,6 @@ static void io_worker_exit(struct io_worker *worker) if (worker->flags & IO_WORKER_F_FREE) hlist_nulls_del_rcu(&worker->nulls_node); list_del_rcu(&worker->all_list); - acct->nr_workers--; preempt_disable(); io_wqe_dec_running(worker); worker->flags = 0; @@ -569,6 +567,7 @@ static int io_wqe_worker(void *data) } /* timed out, exit unless we're the last worker */ if (last_timeout && acct->nr_workers > 1) { + acct->nr_workers--; raw_spin_unlock(&wqe->lock); __set_current_state(TASK_RUNNING); break; -- GitLab