Commit 724cb4f9 authored by Hao Xu's avatar Hao Xu Committed by Jens Axboe
Browse files

io_uring: check sqring and iopoll_list before shedule 



do this to avoid race below:

         userspace                         kernel

                               |  check sqring and iopoll_list
submit sqe                     |
check IORING_SQ_NEED_WAKEUP    |
(which is not set)    |        |
                               |  set IORING_SQ_NEED_WAKEUP
wait cqe                       |  schedule(never wakeup again)

Signed-off-by: default avatarHao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619018351-75883-1-git-send-email-haoxu@linux.alibaba.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f2a48dd0

fs/io_uring.c

+19 −17
Original line number Diff line number Diff line
@@ -6839,8 +6839,12 @@ static int io_sq_thread(void *data) 
			continue;

		}



		needs_sched = true;

		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);

		if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) {

			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)

				io_ring_set_wakeup_flag(ctx);



			needs_sched = true;

			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {

				if ((ctx->flags & IORING_SETUP_IOPOLL) &&

				    !list_empty_careful(&ctx->iopoll_list)) {
@@ -6853,13 +6857,11 @@ static int io_sq_thread(void *data) 
				}

			}



		if (needs_sched && !test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) {

			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)

				io_ring_set_wakeup_flag(ctx);



			if (needs_sched) {

				mutex_unlock(&sqd->lock);

				schedule();

				mutex_lock(&sqd->lock);

			}

			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)

				io_ring_clear_wakeup_flag(ctx);

		}