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authorXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>2020-02-22 07:46:05 +0100
committerJens Axboe <axboe@kernel.dk>2020-02-22 15:45:03 +0100
commitc7849be9cc2dd2754c48ddbaca27c2de6d80a95d (patch)
treef097b2326d01be9834bcad66d20b1818464db2f1 /fs/io_uring.c
parentio_uring: prevent sq_thread from spinning when it should stop (diff)
downloadlinux-c7849be9cc2dd2754c48ddbaca27c2de6d80a95d.tar.xz
linux-c7849be9cc2dd2754c48ddbaca27c2de6d80a95d.zip
io_uring: fix __io_iopoll_check deadlock in io_sq_thread
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>
Diffstat (limited to '')
-rw-r--r--fs/io_uring.c27
1 files changed, 9 insertions, 18 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index b43467b3a8dc..de650df9ac53 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1672,11 +1672,17 @@ 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;
@@ -1712,21 +1718,6 @@ 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;
}
@@ -5118,7 +5109,7 @@ 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);