From 18ca51d074726833f8fef279c90efd3651b1d4a3 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Fri, 24 Jul 2020 20:07:21 +0300 Subject: [PATCH] io_uring: fix lockup in io_fail_links() to #29608102 commit 4ae6dbd683860b9edc254ea8acf5e04b5ae242e5 upstream. io_fail_links() doesn't consider REQ_F_COMP_LOCKED leading to nested spin_lock(completion_lock) and lockup. [ 197.680409] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 6-... } 18239 jiffies s: 1421 root: 0x40/. [ 197.680411] rcu: blocking rcu_node structures: [ 197.680412] Task dump for CPU 6: [ 197.680413] link-timeout R running task 0 1669 1 0x8000008a [ 197.680414] Call Trace: [ 197.680420] ? io_req_find_next+0xa0/0x200 [ 197.680422] ? io_put_req_find_next+0x2a/0x50 [ 197.680423] ? io_poll_task_func+0xcf/0x140 [ 197.680425] ? task_work_run+0x67/0xa0 [ 197.680426] ? do_exit+0x35d/0xb70 [ 197.680429] ? syscall_trace_enter+0x187/0x2c0 [ 197.680430] ? do_group_exit+0x43/0xa0 [ 197.680448] ? __x64_sys_exit_group+0x18/0x20 [ 197.680450] ? do_syscall_64+0x52/0xa0 [ 197.680452] ? entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe Signed-off-by: Jiufei Xue Reviewed-by: Joseph Qi --- fs/io_uring.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index d42f2eea5416..c6eb0cfdb157 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4161,10 +4161,9 @@ static void io_poll_task_handler(struct io_kiocb *req, struct io_kiocb **nxt) hash_del(&req->hash_node); io_poll_complete(req, req->result, 0); - req->flags |= REQ_F_COMP_LOCKED; - io_put_req_find_next(req, nxt); spin_unlock_irq(&ctx->completion_lock); + io_put_req_find_next(req, nxt); io_cqring_ev_posted(ctx); } -- GitLab