io_uring: fix io_sq_thread no schedule when busy

When the user consumes and generates sqe at a fast rate,
io_sqring_entries can always get sqe, and ret will not be equal to -EBUSY,
so that io_sq_thread will never call cond_resched or schedule, and then
we will get the following system error prompt:

rcu: INFO: rcu_sched self-detected stall on CPU
or
watchdog: BUG: soft lockup-CPU#23 stuck for 112s! [io_uring-sq:1863]

This patch checks whether need to call cond_resched() by checking
the need_resched() function every cycle.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a78201b..9de9db7 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6011,7 +6011,7 @@ static int io_sq_thread(void *data)
                 * If submit got -EBUSY, flag us as needing the application
                 * to enter the kernel to reap and flush events.
                 */
-               if (!to_submit || ret == -EBUSY) {
+               if (!to_submit || ret == -EBUSY || need_resched()) {
                        /*
                         * Drop cur_mm before scheduling, we can't hold it for
                         * long periods (or over schedule()). Do this before
@@ -6027,7 +6027,7 @@ static int io_sq_thread(void *data)
                         * more IO, we should wait for the application to
                         * reap events and wake us up.
                         */
-                       if (!list_empty(&ctx->poll_list) ||
+                       if (!list_empty(&ctx->poll_list) || need_resched() ||
                            (!time_after(jiffies, timeout) && ret != -EBUSY &&
                            !percpu_ref_is_dying(&ctx->refs))) {
                                if (current->task_works)