Re: [PATCH] io_uring/rsrc: don't lock while !TASK_RUNNING

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/12/24 13:56, Pavel Begunkov wrote:
> There is a report of io_rsrc_ref_quiesce() locking a mutex while not
> TASK_RUNNING, which is due to forgetting restoring the state back after
> io_run_task_work_sig() and attempts to break out of the waiting loop.

Jens, can you add while applying please?

Reported-by: Li Shi <sl1589472800@gmail.com>


> do not call blocking ops when !TASK_RUNNING; state=1 set at
> [<ffffffff815d2494>] prepare_to_wait+0xa4/0x380
> kernel/sched/wait.c:237
> WARNING: CPU: 2 PID: 397056 at kernel/sched/core.c:10099
> __might_sleep+0x114/0x160 kernel/sched/core.c:10099
> RIP: 0010:__might_sleep+0x114/0x160 kernel/sched/core.c:10099
> Call Trace:
>   <TASK>
>   __mutex_lock_common kernel/locking/mutex.c:585 [inline]
>   __mutex_lock+0xb4/0x940 kernel/locking/mutex.c:752
>   io_rsrc_ref_quiesce+0x590/0x940 io_uring/rsrc.c:253
>   io_sqe_buffers_unregister+0xa2/0x340 io_uring/rsrc.c:799
>   __io_uring_register io_uring/register.c:424 [inline]
>   __do_sys_io_uring_register+0x5b9/0x2400 io_uring/register.c:613
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xd8/0x270 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x6f/0x77
> 
> Fixes: 4ea15b56f0810 ("io_uring/rsrc: use wq for quiescing")
> Cc: stable@vger.kernel.org
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>   io_uring/rsrc.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 65417c9553b1..edb9c5baf2e2 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -249,6 +249,7 @@ __cold static int io_rsrc_ref_quiesce(struct io_rsrc_data *data,
>   
>   		ret = io_run_task_work_sig(ctx);
>   		if (ret < 0) {
> +			__set_current_state(TASK_RUNNING);
>   			mutex_lock(&ctx->uring_lock);
>   			if (list_empty(&ctx->rsrc_ref_list))
>   				ret = 0;

-- 
Pavel Begunkov