public inbox for [email protected]
 help / color / mirror / Atom feed
From: Hao Xu <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected], Pavel Begunkov <[email protected]>,
	Joseph Qi <[email protected]>
Subject: [PATCH 4/4] io-wq: fix potential race of acct->nr_workers
Date: Sun, 12 Sep 2021 03:40:52 +0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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 <[email protected]>
---
 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 75e79571bdfd..b84dc8df6c68 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();
 	refcount_set(&worker->ref, 1);
 	io_wqe_dec_running(worker);
@@ -571,6 +569,7 @@ 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;
-- 
2.24.4


  parent reply	other threads:[~2021-09-11 19:41 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-11 19:40 [PATCH 0/4] iowq fix Hao Xu
2021-09-11 19:40 ` [PATCH 1/4] io-wq: tweak return value of io_wqe_create_worker() Hao Xu
2021-09-12 18:10   ` Jens Axboe
2021-09-12 19:02     ` Hao Xu
2021-09-12 21:34       ` Jens Axboe
2021-09-13  6:37         ` Hao Xu
2021-09-11 19:40 ` [PATCH 2/4] io-wq: code clean " Hao Xu
2021-09-12 18:18   ` Jens Axboe
2021-09-13  8:30   ` Hao Xu
2021-09-11 19:40 ` [PATCH 3/4] io-wq: fix worker->refcount when creating worker in work exit Hao Xu
2021-09-11 22:13   ` Jens Axboe
2021-09-12  9:04     ` Hao Xu
2021-09-12 18:07       ` Jens Axboe
2021-09-11 19:40 ` Hao Xu [this message]
2021-09-12 18:23   ` [PATCH 4/4] io-wq: fix potential race of acct->nr_workers Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox