linux-kernel - Re: [RFC][PATCH 2/2] time: alarmtimer: Use TASK

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Date: Thu, 27 Jun 2024 09:46:24 +0200
From: Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, John Stultz <jstultz@...gle.com>, 
	LKML <linux-kernel@...r.kernel.org>, Stephen Boyd <sboyd@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, Michael <michael@...isi.de>, kernel-team@...roid.com, 
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC][PATCH 2/2] time: alarmtimer: Use TASK_FREEZABLE to cleanup
 freezer handling

Hi Thomas

On Thu, Mar 2, 2023 at 11:58 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Thu, Mar 02 2023 at 23:21, Thomas Gleixner wrote:
> > On Thu, Mar 02 2023 at 15:32, Rafael J. Wysocki wrote:
> >> On Mon, Feb 20, 2023 at 10:19 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> >>> +static atomic_t alarmtimer_wakeup;
> >>>
> >>>  /**
> >>>   * alarmtimer_fired - Handles alarm hrtimer being fired.
> >>> @@ -194,6 +196,8 @@ static enum hrtimer_restart alarmtimer_f
> >>>         int ret = HRTIMER_NORESTART;
> >>>         int restart = ALARMTIMER_NORESTART;
> >>>
> >>> +       atomic_inc(&alarmtimer_wakeup);
> >>> +
> >>
> >> This appears to be still somewhat racy, because the notifier can run
> >> at this point AFAICS.
> >
> > Indeed it is. Let me think more about this.
>
> All of this is inherently racy as there is zero feedback whether the
> event has been consumed or not. Making this feedback based is not
> necessarily trivial, but let me stare into that.
>

Sorry to come back on this topic but I would like to know, if we can
find a way to be sure
to not lost wakeup or if you have already addressed in some series

Michael


> Thanks,
>
>         tglx
>


-- 
Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
M. +39 347 913 2170
michael@...rulasolutions.com
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