linux-kernel - Re: [PATCH 0/2] nohz: Deal with clock reprogram skipping issues v3

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Message-ID: <20170523131042.GA26103@lerouge>
Date:   Tue, 23 May 2017 15:10:45 +0200
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        James Hartsock <hartsjc@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org,
        Tim Wright <tim@...bash.co.uk>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH 0/2] nohz: Deal with clock reprogram skipping issues v3

On Tue, May 23, 2017 at 09:25:08AM +0200, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
> > v2 had issues on -tip tree and triggered a warning. It seems to have
> > disappeared. Perhaps it was due to another timer issue. Anyway this
> > version brings more debugging informations, with a layout that is more
> > bisection-friendly and it also handles ticks that fire outside IRQ
> > context and thus carry NULL irq regs. This happen when
> > hrtimer_interrupt() is called on hotplug cpu down for example.
> > 
> > We'll see if the issue arises again.
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> > 	nohz/fixes
> > 
> > HEAD: cd15f46b284f04dbedd065a9d99a4e0badae379a
> > 
> > Thanks,
> > 	Frederic
> > ---
> > 
> > Frederic Weisbecker (2):
> >       nohz: Add hrtimer sanity check
> >       nohz: Fix collision between tick and other hrtimers, again
> > 
> > 
> >  kernel/time/tick-sched.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
> >  kernel/time/tick-sched.h |  2 ++
> >  2 files changed, 45 insertions(+), 5 deletions(-)
> 
> So I think the 3 commits queued up right now:
> 
>  99fa871820cf: nohz: Reset next_tick cache even when the timer has no regs
>  411fe24e6b7c: nohz: Fix collision between tick and other hrtimers, again
>  ce6cf9a15d62: nohz: Add hrtimer sanity check
> 
> are OK and I'd not rebase them unless there's some breakage.
> 
> One thing I noticed: your second series does appear to have:
> 
>  99fa871820cf: nohz: Reset next_tick cache even when the timer has no regs
> 
> is that intentional? That is pretty much the only commit I'd love to rebase with a 
> proper description added.

Yes in my latest series I melted "nohz: Reset next_tick cache even when the timer has no regs"
into "nohz: Fix collision between tick and other hrtimers, again" because it's a fixup and
keeping that patch separate may break bisection.

So ideally, it would be nice if you could fixup 411fe24e6b7c with 99fa871820cf. That's roughly
all I did in my latest series.

Thanks!