Re: [PATCH 5.13] io_uring: don't set IORING_SQ_NEED_WAKEUP when sqthread is dying

[Hao Xu <haoxu@linux.alibaba.com>]

在 2021/4/27 下午10:35, Hao Xu 写道:
> 在 2021/4/27 下午9:13, Pavel Begunkov 写道:
>> On 4/27/21 1:45 PM, Hao Xu wrote:
>>> we don't need to re-fork the sqthread over exec, so no need to set
>>> IORING_SQ_NEED_WAKEUP when sqthread is dying.
>>
>> It forces users to call io_uring_enter() for it to return
>> -EOWNERDEAD. Consider that scenario with the ring given
>> away to some other task not in current group, e.g. via socket.
>>
> Ah, I see. Thank you Pavel.
Here I've a question: for processes that aren't in same group, io_uring
is now designed that sqthread cannot be shared between these processes?
But It seems if users do fork(), they can still call io_uring_enter()
in the forked task?
>> if (ctx->flags & IORING_SETUP_SQPOLL) {
>>     io_cqring_overflow_flush(ctx, false);
>>
>>     ret = -EOWNERDEAD;
>>     if (unlikely(ctx->sq_data->thread == NULL)) {
>>         goto out;
>>     }
>>     ...
>> }
>>
>> btw, can use a comment
>>
>>>
>>> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
>>> ---
>>>   fs/io_uring.c | 2 --
>>>   1 file changed, 2 deletions(-)
>>>
>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>> index 6b578c380e73..92dcd1c21516 100644
>>> --- a/fs/io_uring.c
>>> +++ b/fs/io_uring.c
>>> @@ -6897,8 +6897,6 @@ static int io_sq_thread(void *data)
>>>       io_uring_cancel_sqpoll(sqd);
>>>       sqd->thread = NULL;
>>> -    list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
>>> -        io_ring_set_wakeup_flag(ctx);
>>>       io_run_task_work();
>>>       io_run_task_work_head(&sqd->park_task_work);
>>>       mutex_unlock(&sqd->lock);
>>>
>>