* [PATCH AUTOSEL 5.6 45/50] io_uring: use cond_resched() in io_ring_ctx_wait_and_kill()
[not found] <[email protected]>
@ 2020-05-07 14:27 ` Sasha Levin
0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2020-05-07 14:27 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Xiaoguang Wang, Jens Axboe, Sasha Levin, linux-fsdevel, io-uring
From: Xiaoguang Wang <[email protected]>
[ 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: [email protected]
Signed-off-by: Xiaoguang Wang <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
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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