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Message-Id: <20200227132252.298299837@linuxfoundation.org>
Date: Thu, 27 Feb 2020 14:37:52 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org,
Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.5 135/150] io_uring: fix __io_iopoll_check deadlock in io_sq_thread
From: Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
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@...ux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
fs/io_uring.c | 27 +++++++++------------------
1 file changed, 9 insertions(+), 18 deletions(-)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1286,11 +1286,17 @@ static void io_iopoll_reap_events(struct
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;
@@ -1326,21 +1332,6 @@ static int __io_iopoll_check(struct io_r
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;
}
@@ -3884,7 +3875,7 @@ 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);
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