| From 6a713d15dd33c271bef11b60d091905a44c63f2c Mon Sep 17 00:00:00 2001 |
| From: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> |
| Date: Sat, 22 Feb 2020 14:46:05 +0800 |
| Subject: [PATCH] io_uring: fix __io_iopoll_check deadlock in io_sq_thread |
| |
| commit c7849be9cc2dd2754c48ddbaca27c2de6d80a95d upstream. |
| |
| Since commit a3a0e43fd770 ("io_uring: don't enter poll loop if we have |
| CQEs pending"), if we already events pending, we won't enter poll loop. |
| In case SETUP_IOPOLL and SETUP_SQPOLL are both enabled, if app has |
| been terminated and don't reap pending events which are already in cq |
| ring, and there are some reqs in poll_list, io_sq_thread will enter |
| __io_iopoll_check(), and find pending events, then return, this loop |
| will never have a chance to exit. |
| |
| I have seen this issue in fio stress tests, to fix this issue, let |
| io_sq_thread call io_iopoll_getevents() with argument 'min' being zero, |
| and remove __io_iopoll_check(). |
| |
| Fixes: a3a0e43fd770 ("io_uring: don't enter poll loop if we have CQEs pending") |
| Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/fs/io_uring.c b/fs/io_uring.c |
| index abfbc55e8782..0761c28e8b2e 100644 |
| --- a/fs/io_uring.c |
| +++ b/fs/io_uring.c |
| @@ -756,11 +756,17 @@ static void io_iopoll_reap_events(struct io_ring_ctx *ctx) |
| mutex_unlock(&ctx->uring_lock); |
| } |
| |
| -static int __io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, |
| - long min) |
| +static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, |
| + long min) |
| { |
| int iters = 0, ret = 0; |
| |
| + /* |
| + * We disallow the app entering submit/complete with polling, but we |
| + * still need to lock the ring to prevent racing with polled issue |
| + * that got punted to a workqueue. |
| + */ |
| + mutex_lock(&ctx->uring_lock); |
| do { |
| int tmin = 0; |
| |
| @@ -796,21 +802,6 @@ static int __io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, |
| ret = 0; |
| } while (min && !*nr_events && !need_resched()); |
| |
| - return ret; |
| -} |
| - |
| -static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, |
| - long min) |
| -{ |
| - int ret; |
| - |
| - /* |
| - * We disallow the app entering submit/complete with polling, but we |
| - * still need to lock the ring to prevent racing with polled issue |
| - * that got punted to a workqueue. |
| - */ |
| - mutex_lock(&ctx->uring_lock); |
| - ret = __io_iopoll_check(ctx, nr_events, min); |
| mutex_unlock(&ctx->uring_lock); |
| return ret; |
| } |
| @@ -2150,7 +2141,7 @@ static int io_sq_thread(void *data) |
| */ |
| mutex_lock(&ctx->uring_lock); |
| if (!list_empty(&ctx->poll_list)) |
| - __io_iopoll_check(ctx, &nr_events, 0); |
| + io_iopoll_getevents(ctx, &nr_events, 0); |
| else |
| inflight = 0; |
| mutex_unlock(&ctx->uring_lock); |
| -- |
| 2.7.4 |
| |