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authorXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>2020-05-01 08:52:56 +0800
committerJens Axboe <axboe@kernel.dk>2020-04-30 22:24:27 -0600
commit3fd44c86711f71156b586c22b0495c58f69358bb (patch)
treef68fdffa820b90785254cabbebee9c8f0563dbac
parentdd461af65946de060bff2dab08a63676d2731afe (diff)
io_uring: use cond_resched() in io_ring_ctx_wait_and_kill()
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@syzkaller.appspotmail.com Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--fs/io_uring.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3da2a02531e6..5ca2da6648d0 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7343,7 +7343,7 @@ 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);