Re: [PATCH 2/6] kernel: add task_sigpending() helper

Jens Axboe
2020-10-08T13:38:07Z

On 10/8/20 7:24 AM, Oleg Nesterov wrote:
> On 10/05, Jens Axboe wrote:
>>
>> @@ -4447,7 +4447,7 @@ SYSCALL_DEFINE0(pause)
>> __set_current_state(TASK_INTERRUPTIBLE);
>> schedule();
>> }
>> - return -ERESTARTNOHAND;
>> + return task_sigpending(current) ? -ERESTARTNOHAND : -ERESTARTSYS;
>> }
>>
>> #endif
>> @@ -4462,7 +4462,7 @@ static int sigsuspend(sigset_t *set)
>> schedule();
>> }
>> set_restore_sigmask();
>> - return -ERESTARTNOHAND;
>> + return task_sigpending(current) ? -ERESTARTNOHAND : -ERESTARTSYS;
>> }
>
> Both changes are equally wrong. Why do you think sigsuspend() should ever
> return -ERESTARTSYS ?
>
> If get_signal() deques a signal, handle_signal() will restart this syscall
> if ERESTARTSYS, this is wrong.

The intent was that if we get woken up and signal_pending() is true, then
we want to restart it if we're just doing TIF_SIGNAL_NOTIFY. But I guess
it can't be 100% reliable, even if TIF_SIGPENDING isn't set at this point,
but it is by the time a signal is attempted dequeued.

I'll drop these too, thanks Oleg.

--
Jens Axboe