From 724cb4f9ec905173f32c5bd08fec26abaecc6a1d Mon Sep 17 00:00:00 2001 From: Hao Xu Date: Wed, 21 Apr 2021 23:19:11 +0800 Subject: [PATCH] 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: Hao Xu Link: https://lore.kernel.org/r/1619018351-75883-1-git-send-email-haoxu@linux.alibaba.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 36 +++++++++++++++++++----------------- 1 file changed, 19 insertions(+), 17 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 2d49197..40f3825 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -6839,27 +6839,29 @@ static int io_sq_thread(void *data) continue; } - needs_sched = true; prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE); - list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) { - if ((ctx->flags & IORING_SETUP_IOPOLL) && - !list_empty_careful(&ctx->iopoll_list)) { - needs_sched = false; - break; - } - if (io_sqring_entries(ctx)) { - needs_sched = false; - break; - } - } - - if (needs_sched && !test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) { + 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); - mutex_unlock(&sqd->lock); - schedule(); - mutex_lock(&sqd->lock); + 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)) { + needs_sched = false; + break; + } + if (io_sqring_entries(ctx)) { + needs_sched = false; + break; + } + } + + 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); } -- 2.7.4