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Date:   Thu, 15 Oct 2020 16:34:10 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org,
        io-uring@vger.kernel.org, peterz@infradead.org
Subject: Re: [PATCH 4/5] x86: wire up TIF_NOTIFY_SIGNAL
Message-ID: <20201015143409.GC24156@redhat.com>
References: <20201015131701.511523-1-axboe@kernel.dk>
 <20201015131701.511523-5-axboe@kernel.dk>
 <87o8l3a8af.fsf@nanos.tec.linutronix.de>
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On 10/15, Thomas Gleixner wrote:
>
> On Thu, Oct 15 2020 at 07:17, Jens Axboe wrote:
> > --- a/arch/x86/kernel/signal.c
> > +++ b/arch/x86/kernel/signal.c
> > @@ -808,7 +808,10 @@ void arch_do_signal(struct pt_regs *regs, unsigned long ti_work)
> >  {
> >  	struct ksignal ksig;
> >  
> > -	if (get_signal(&ksig)) {
> > +	if (ti_work & _TIF_NOTIFY_SIGNAL)
> > +		tracehook_notify_signal();
> > +
> > +	if ((ti_work & _TIF_SIGPENDING) && get_signal(&ksig)) {
> >  		/* Whee! Actually deliver the signal.  */
> >  		handle_signal(&ksig, regs);
> >  		return;
> 
> Instead of adding this to every architectures signal magic, we can
> handle TIF_NOTIFY_SIGNAL in the core code:
> 
> static void handle_singal_work(ti_work, regs)
> {
> 	if (ti_work & _TIF_NOTIFY_SIGNAL)
>         	tracehook_notify_signal();
> 
>         arch_do_signal(ti_work, regs);
> }
> 
>       loop {
>       		if (ti_work & (SIGPENDING | NOTIFY_SIGNAL))
>                 	handle_signal_work(ti_work, regs);
>       }

To me this looks like unnecessary complication. We need to change
every architecture anyway, how can this helper help?

Oleg.