From: Xiaoguang Wang xiaoguang.wang@linux.alibaba.com
mainline inclusion from mainline-5.6-rc3 commit c7849be9cc2dd2754c48ddbaca27c2de6d80a95d category: feature bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27 CVE: NA ---------------------------
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: yangerkun yangerkun@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- fs/io_uring.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index c3f0df489a57..717055df430a 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1666,11 +1666,17 @@ 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;
@@ -1706,21 +1712,6 @@ 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; } @@ -5052,7 +5043,7 @@ 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);