Commit 3fd44c86 authored by Xiaoguang Wang's avatar Xiaoguang Wang Committed by Jens Axboe

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: default avatarXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent dd461af6
...@@ -7343,7 +7343,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx) ...@@ -7343,7 +7343,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
* it could cause shutdown to hang. * it could cause shutdown to hang.
*/ */
while (ctx->sqo_thread && !wq_has_sleeper(&ctx->sqo_wait)) while (ctx->sqo_thread && !wq_has_sleeper(&ctx->sqo_wait))
cpu_relax(); cond_resched();
io_kill_timeouts(ctx); io_kill_timeouts(ctx);
io_poll_remove_all(ctx); io_poll_remove_all(ctx);
......
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