From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Kevin Hilman <khilman@kernel.org>,
Magnus Damm <damm@opensource.se>,
Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Linux-sh list <linux-sh@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code
Date: Wed, 24 Jun 2015 15:48:12 +0200 [thread overview]
Message-ID: <1472640.FZpH0ugFKI@vostro.rjw.lan> (raw)
In-Reply-To: <CAMuHMdUzj_jZXw8OdsH89fVmrK-hQZx-wQR7cVbo9d3QJ8JJVg@mail.gmail.com>
On Wednesday, June 24, 2015 10:35:44 AM Geert Uytterhoeven wrote:
> On Wed, Jun 24, 2015 at 10:33 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> > [...]
> >
> >>>>
> >>>> @@ -2183,6 +2191,7 @@ int genpd_dev_pm_attach(struct device *dev)
> >>>> {
> >>>> struct of_phandle_args pd_args;
> >>>> struct generic_pm_domain *pd;
> >>>> + unsigned int i;
> >>>> int ret;
> >>>>
> >>>> if (!dev->of_node)
> >>>> @@ -2218,10 +2227,13 @@ int genpd_dev_pm_attach(struct device *dev)
> >>>>
> >>>> dev_dbg(dev, "adding to PM domain %s\n", pd->name);
> >>>>
> >>>> - while (1) {
> >>>> + for (i = 0; i < GENPD_RETRIES; i++) {
> >>>> ret = pm_genpd_add_device(pd, dev);
> >>>> if (ret != -EAGAIN)
> >>>> break;
> >>>> +
> >>>> + if (i > GENPD_RETRIES / 2)
> >>>> + udelay(GENPD_DELAY_US);
> >>>
> >>> In this execution path, we retry when getting -EAGAIN while believing
> >>> the reason to the error are only *temporary* as we are soon waiting
> >>> for all devices in the genpd to be system PM resumed. At least that's
> >>> my understanding to why we want to deal with -EAGAIN here, but I might
> >>> be wrong.
> >>>
> >>> In this regards, I wonder whether it could be better to re-try only a
> >>> few times but with a far longer interval time than a couple us. What
> >>> do you think?
> >>
> >> That's indeed viable. I have no idea for how long this temporary state can
> >> extend.
> >
> > That will depend on the system PM resume time for the devices residing
> > in the genpd. So, I guess we need a guestimate then. How about a total
> > sleep time of a few seconds?
> >
> >>
> >>> However, what if the reason to why we get -EAGAIN isn't *temporary*,
> >>> because we are about to enter system PM suspend state. Then the caller
> >>> of this function which comes via some bus' ->probe(), will hang until
> >>> the a system PM resume is completed. Is that really going to work? So,
> >>> for this case your limited re-try approach will affect this scenario
> >>> as well, have you considered that?
> >>
> >> There's a limit on the number of retries, so it won't hang indefinitely.
> >
> > What happens with the timer functions (like msleep()) during the
> > system PM suspend transition?
>
> I guess we can no longer call msleep() after syscore suspend?
That's correct. Time is effectively frozen at that point.
Rafael
WARNING: multiple messages have this Message-ID (diff)
From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: linux-sh@vger.kernel.org
Subject: Re: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code
Date: Wed, 24 Jun 2015 13:48:12 +0000 [thread overview]
Message-ID: <1472640.FZpH0ugFKI@vostro.rjw.lan> (raw)
In-Reply-To: <1434622954-26747-3-git-send-email-geert+renesas@glider.be>
On Wednesday, June 24, 2015 10:35:44 AM Geert Uytterhoeven wrote:
> On Wed, Jun 24, 2015 at 10:33 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> > [...]
> >
> >>>>
> >>>> @@ -2183,6 +2191,7 @@ int genpd_dev_pm_attach(struct device *dev)
> >>>> {
> >>>> struct of_phandle_args pd_args;
> >>>> struct generic_pm_domain *pd;
> >>>> + unsigned int i;
> >>>> int ret;
> >>>>
> >>>> if (!dev->of_node)
> >>>> @@ -2218,10 +2227,13 @@ int genpd_dev_pm_attach(struct device *dev)
> >>>>
> >>>> dev_dbg(dev, "adding to PM domain %s\n", pd->name);
> >>>>
> >>>> - while (1) {
> >>>> + for (i = 0; i < GENPD_RETRIES; i++) {
> >>>> ret = pm_genpd_add_device(pd, dev);
> >>>> if (ret != -EAGAIN)
> >>>> break;
> >>>> +
> >>>> + if (i > GENPD_RETRIES / 2)
> >>>> + udelay(GENPD_DELAY_US);
> >>>
> >>> In this execution path, we retry when getting -EAGAIN while believing
> >>> the reason to the error are only *temporary* as we are soon waiting
> >>> for all devices in the genpd to be system PM resumed. At least that's
> >>> my understanding to why we want to deal with -EAGAIN here, but I might
> >>> be wrong.
> >>>
> >>> In this regards, I wonder whether it could be better to re-try only a
> >>> few times but with a far longer interval time than a couple us. What
> >>> do you think?
> >>
> >> That's indeed viable. I have no idea for how long this temporary state can
> >> extend.
> >
> > That will depend on the system PM resume time for the devices residing
> > in the genpd. So, I guess we need a guestimate then. How about a total
> > sleep time of a few seconds?
> >
> >>
> >>> However, what if the reason to why we get -EAGAIN isn't *temporary*,
> >>> because we are about to enter system PM suspend state. Then the caller
> >>> of this function which comes via some bus' ->probe(), will hang until
> >>> the a system PM resume is completed. Is that really going to work? So,
> >>> for this case your limited re-try approach will affect this scenario
> >>> as well, have you considered that?
> >>
> >> There's a limit on the number of retries, so it won't hang indefinitely.
> >
> > What happens with the timer functions (like msleep()) during the
> > system PM suspend transition?
>
> I guess we can no longer call msleep() after syscore suspend?
That's correct. Time is effectively frozen at that point.
Rafael
next prev parent reply other threads:[~2015-06-24 13:22 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-18 10:22 [PATCH 0/2] PM / Domains: Infinite loop during reboot Geert Uytterhoeven
2015-06-18 10:22 ` Geert Uytterhoeven
2015-06-18 10:22 ` [PATCH 1/2] clocksource: sh_cmt: Only perform clocksource suspend/resume if enabled Geert Uytterhoeven
2015-06-18 10:22 ` Geert Uytterhoeven
2015-06-18 14:14 ` Laurent Pinchart
2015-06-18 14:14 ` Laurent Pinchart
2015-06-18 14:19 ` Geert Uytterhoeven
2015-06-18 14:19 ` Geert Uytterhoeven
2015-06-18 10:22 ` [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code Geert Uytterhoeven
2015-06-18 10:22 ` Geert Uytterhoeven
2015-06-22 7:30 ` Geert Uytterhoeven
2015-06-22 7:30 ` Geert Uytterhoeven
2015-06-22 7:30 ` Geert Uytterhoeven
2015-06-22 7:31 ` Geert Uytterhoeven
2015-06-22 7:31 ` Geert Uytterhoeven
2015-06-22 7:31 ` Geert Uytterhoeven
2015-06-22 23:41 ` Rafael J. Wysocki
2015-06-22 23:41 ` Rafael J. Wysocki
2015-06-22 23:41 ` Rafael J. Wysocki
2015-06-23 7:16 ` Geert Uytterhoeven
2015-06-23 7:16 ` Geert Uytterhoeven
2015-06-23 7:16 ` Geert Uytterhoeven
2015-06-23 12:50 ` Ulf Hansson
2015-06-23 12:50 ` Ulf Hansson
2015-06-23 13:20 ` Geert Uytterhoeven
2015-06-23 13:20 ` Geert Uytterhoeven
2015-06-23 13:38 ` Rafael J. Wysocki
2015-06-23 13:38 ` Rafael J. Wysocki
2015-06-23 13:45 ` Geert Uytterhoeven
2015-06-23 13:45 ` Geert Uytterhoeven
2015-06-24 8:33 ` Ulf Hansson
2015-06-24 8:33 ` Ulf Hansson
2015-06-24 8:35 ` Geert Uytterhoeven
2015-06-24 8:35 ` Geert Uytterhoeven
2015-06-24 13:48 ` Rafael J. Wysocki [this message]
2015-06-24 13:48 ` Rafael J. Wysocki
2015-06-24 13:44 ` Rafael J. Wysocki
2015-06-24 14:10 ` Rafael J. Wysocki
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