linux-kernel - Re: [RFC PATCH 1/8] signal: Dequeue SIGKILL even if SIGNAL_GROUP_EXIT/group_exec

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Date:   Thu, 18 May 2023 11:42:12 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>, linux@...mhuis.info,
        nicolas.dichtel@...nd.com, axboe@...nel.dk,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, mst@...hat.com,
        sgarzare@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
        brauner@...nel.org
Subject: Re: [RFC PATCH 1/8] signal: Dequeue SIGKILL even if
 SIGNAL_GROUP_EXIT/group_exec_task is set

On 5/18/23 11:25 AM, Oleg Nesterov wrote:
> I too do not understand the 1st change in this patch ...
> 
> On 05/18, Mike Christie wrote:
>>
>> In the other patches we do:
>>
>> if (get_signal(ksig))
>> 	start_exit_cleanup_by_stopping_newIO()
>> 	flush running IO()
>> 	exit()
>>
>> But to do the flush running IO() part of this I need to wait for it so
>> that's why I wanted to be able to dequeue the SIGKILL and clear the
>> TIF_SIGPENDING bit.
> 
> But get_signal() will do what you need, dequeue SIGKILL and clear SIGPENDING ?
> 
> 	if ((signal->flags & SIGNAL_GROUP_EXIT) ||
> 	     signal->group_exec_task) {
> 		clear_siginfo(&ksig->info);
> 		ksig->info.si_signo = signr = SIGKILL;
> 		sigdelset(&current->pending.signal, SIGKILL);
> 
> this "dequeues" SIGKILL,
> 
> 		trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
> 			&sighand->action[SIGKILL - 1]);
> 		recalc_sigpending();
> 
> this clears TIF_SIGPENDING.
> 

I see what you guys meant. TIF_SIGPENDING isn't getting cleared.
I'll dig into why.