On 2/20/20 3:58 PM, Jann Horn wrote:
> On Thu, Feb 20, 2020 at 11:56 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>> On 2/20/20 3:38 PM, Jann Horn wrote:
>>> On Thu, Feb 20, 2020 at 11:23 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>>>> On 2/20/20 3:14 PM, Jens Axboe wrote:
>>>>>>> @@ -3646,46 +3596,11 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
>>>>>>>
>>>>>>> list_del_init(&poll->wait.entry);
>>>>>>>
>>>>>> [...]
>>>>>>> + tsk = req->task;
>>>>>>> + req->result = mask;
>>>>>>> + init_task_work(&req->sched_work, io_poll_task_func);
>>>>>>> + sched_work_add(tsk, &req->sched_work);
>>>>>>
>>>>>> Doesn't this have to check the return value?
>>>>>
>>>>> Trying to think if we can get here with TASK_EXITING, but probably safer
>>>>> to just handle it in any case. I'll add that.
>>>>
>>>> Double checked this one, and I think it's good as-is, but needs a
>>>> comment. If the sched_work_add() fails, then the work item is still in
>>>> the poll hash on the ctx. That work is canceled on exit.
>>>
>>> You mean via io_poll_remove_all()? That doesn't happen when a thread
>>> dies, right?
>>
>> Off of io_uring_flush, we do:
>>
>> if (fatal_signal_pending(current) || (current->flags & PF_EXITING)) {
>> io_uring_cancel_task_poll(current);
>> io_uring_cancel_task_async(current);
>> io_wq_cancel_pid(ctx->io_wq, task_pid_vnr(current));
>> }
>>
>> to cancel _anything_ that the task has pending.
>
> ->flush() is only for when the uring instance is dropped from a file
> descriptor table; threads typically share their file descriptor
> tables, and therefore won't ->flush() until the last one dies.
True, then I guess I'll need some other notifier for that particular
case. Might be able to use sched_work_run() for that, since we know
that'll definitely get called when the task exits.
--
Jens Axboe
