From: Ulf Hansson <ulf.hansson@linaro.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Linux PM <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-omap <linux-omap@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Biju Das <biju.das@bp.renesas.com>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH v2 ] PM-runtime: fix deadlock with ktime
Date: Tue, 5 Feb 2019 14:40:04 +0100 [thread overview]
Message-ID: <CAPDyKFqSofB2TfQXqhngQhaSKRZr-k-z2CXpQ2oWvnCn3JeFHQ@mail.gmail.com> (raw)
In-Reply-To: <CAMuHMdWdbRpA_M4V1kigab6U8rSDgGYXtidiSU4MVdj5xarK8g@mail.gmail.com>
On Tue, 5 Feb 2019 at 14:24, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Ulf,
>
> On Wed, Jan 30, 2019 at 1:15 PM Ulf Hansson <ulf.hansson@linaro.org> wrote:
> > On Wed, 30 Jan 2019 at 12:16, Vincent Guittot
> > <vincent.guittot@linaro.org> wrote:
> > >
> > > A deadlock has been seen when swicthing clocksources which use PM runtime.
> > > The call path is:
> > > change_clocksource
> > > ...
> > > write_seqcount_begin
> > > ...
> > > timekeeping_update
> > > ...
> > > sh_cmt_clocksource_enable
> > > ...
> > > rpm_resume
> >
> > Hmm, isn't this already a problem in genpd then?
> >
> > In genpd's ->runtime_resume() callback (genpd_runtime_resume()) we
> > call ktime_get() to measure the latency of running the callback.
> >
> > Or, perhaps irq_safe_dev_in_no_sleep_domain() returns true for the
> > genpd + device in question, which means the ktime thingy is skipped.
> >
> > Geert?
>
> Correct. After adding
>
> dev_info(dev, "%s: pm_runtime_is_irq_safe = %d,
> genpd_is_irq_safe(%s) = %d => %s\n", __func__,
> pm_runtime_is_irq_safe(dev), genpd->name, genpd_is_irq_safe(genpd),
> ret ? "true" : "false");
>
> I see on R-Car M2-W:
>
> sh_cmt ffca0000.timer: irq_safe_dev_in_no_sleep_domain:
> pm_runtime_is_irq_safe = 1, genpd_is_irq_safe(always-on) = 0 => true
>
> For all other devices, the result is false.
Thanks for confirming! I guess we have been lucky so far.
Anyway, if runtime PM core converts to use ktime_get_mono_fast_ns(),
we should probably consider to convert genpd to this as well. Don't
you think?
Kind regards
Uffe
next prev parent reply other threads:[~2019-02-05 13:40 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-30 11:16 [PATCH v2 ] PM-runtime: fix deadlock with ktime Vincent Guittot
2019-01-30 12:14 ` Ulf Hansson
2019-02-05 13:24 ` Geert Uytterhoeven
2019-02-05 13:40 ` Ulf Hansson [this message]
2019-01-30 13:06 ` Rafael J. Wysocki
2019-01-30 13:18 ` Vincent Guittot
2019-01-30 19:39 ` Ladislav Michl
2019-01-30 17:26 ` [PATCH v3] " Vincent Guittot
2019-01-30 21:53 ` Rafael J. Wysocki
2019-02-01 15:02 ` Biju Das
2019-02-01 15:28 ` Vincent Guittot
2019-02-01 15:44 ` Biju Das
2019-02-01 15:48 ` Vincent Guittot
2019-02-01 15:52 ` Vincent Guittot
2019-02-04 9:29 ` Biju Das
2019-02-01 15:45 ` Vincent Guittot
2019-01-30 21:32 ` [PATCH v2 ] " Ladislav Michl
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