Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 15 Oct 2020 16:37:29 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     linux-kernel@vger.kernel.org, io-uring@vger.kernel.org,
        peterz@infradead.org, tglx@linutronix.de
Subject: Re: [PATCH 3/5] kernel: add support for TIF_NOTIFY_SIGNAL
Message-ID: <20201015143728.GE24156@redhat.com>
References: <20201015131701.511523-1-axboe@kernel.dk>
 <20201015131701.511523-4-axboe@kernel.dk>
 <20201015143151.GB24156@redhat.com>
 <5d231aa1-b8c7-ae4e-90bb-211f82b57547@kernel.dk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <5d231aa1-b8c7-ae4e-90bb-211f82b57547@kernel.dk>
User-Agent: Mutt/1.5.24 (2015-08-30)
Precedence: bulk

On 10/15, Jens Axboe wrote:
>
> On 10/15/20 8:31 AM, Oleg Nesterov wrote:
> > On 10/15, Jens Axboe wrote:
> >>
> >>  static inline int signal_pending(struct task_struct *p)
> >>  {
> >> +#if defined(CONFIG_GENERIC_ENTRY) && defined(TIF_NOTIFY_SIGNAL)
> >> +	/*
> >> +	 * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same
> >> +	 * behavior in terms of ensuring that we break out of wait loops
> >> +	 * so that notify signal callbacks can be processed.
> >> +	 */
> >> +	if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
> >> +		return 1;
> >> +#endif
> >>  	return task_sigpending(p);
> >>  }
> > 
> > I don't understand why does this version requires CONFIG_GENERIC_ENTRY.
> > 
> > Afaics, it is very easy to change all the non-x86 arches to support
> > TIF_NOTIFY_SIGNAL, but it is not trivial to change them all to use
> > kernel/entry/common.c ?
> 
> I think that Thomas wants to gate TIF_NOTIFY_SIGNAL on conversion to
> the generic entry code?

Then I think TIF_NOTIFY_SIGNAL will be never fully supported ;)

Oleg.