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Message-Id: <20200507142726.25751-45-sashal@kernel.org>
Date: Thu, 7 May 2020 10:27:21 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
linux-fsdevel@...r.kernel.org, io-uring@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 45/50] io_uring: use cond_resched() in io_ring_ctx_wait_and_kill()
From: Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
[ Upstream commit 3fd44c86711f71156b586c22b0495c58f69358bb ]
While working on to make io_uring sqpoll mode support syscalls that need
struct files_struct, I got cpu soft lockup in io_ring_ctx_wait_and_kill(),
while (ctx->sqo_thread && !wq_has_sleeper(&ctx->sqo_wait))
cpu_relax();
above loop never has an chance to exit, it's because preempt isn't enabled
in the kernel, and the context calling io_ring_ctx_wait_and_kill() and
io_sq_thread() run in the same cpu, if io_sq_thread calls a cond_resched()
yield cpu and another context enters above loop, then io_sq_thread() will
always in runqueue and never exit.
Use cond_resched() can fix this issue.
Reported-by: syzbot+66243bb7126c410cefe6@...kaller.appspotmail.com
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
fs/io_uring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a46de2cfc28e8..b5ade01379029 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6449,7 +6449,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
* it could cause shutdown to hang.
*/
while (ctx->sqo_thread && !wq_has_sleeper(&ctx->sqo_wait))
- cpu_relax();
+ cond_resched();
io_kill_timeouts(ctx);
io_poll_remove_all(ctx);
--
2.20.1
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