linux-kernel - Re: [PATCH] power: suspend: Add suspend timeout handler

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Date:   Fri, 16 Oct 2020 15:24:23 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     josephjang@...gle.com
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>, jonglin@...gle.com,
        woodylin@...gle.com, markcheng@...gle.com
Subject: Re: [PATCH] power: suspend: Add suspend timeout handler

On Fri, Oct 16, 2020 at 3:22 PM <josephjang@...gle.com> wrote:
>
> Thank you Rafael's promptly response.
>
> > On Fri, Oct 16, 2020 at 5:51 AM Joseph Jang <josephjang@...gle.com> wrote:
> > >
> > > From: josephjang <josephjang@...gle.com>
> > >
> > > Add suspend timeout handler to prevent device stuck during suspend/
> > > resume process. Suspend timeout handler will dump disk sleep task
> > > at first round timeout and trigger kernel panic at second round timeout.
> > > The default timer for each round is 30 seconds.
> > >
> > > Note: Can use following command to simulate suspend hang for testing.
> > >     adb shell echo 1 > /sys/power/pm_hang
> > >     adb shell echo mem > /sys/power/state
> > > Signed-off-by: josephjang <josephjang@...gle.com>
> > > ---
> > >  include/linux/console.h |   1 +
> > >  kernel/power/Kconfig    |   9 +++
> > >  kernel/power/main.c     |  66 ++++++++++++++++
> > >  kernel/power/suspend.c  | 162 ++++++++++++++++++++++++++++++++++++++++
> > >  kernel/printk/printk.c  |   5 ++
> > >  5 files changed, 243 insertions(+)
> > >
> > > diff --git a/include/linux/console.h b/include/linux/console.h
> > > index 0670d3491e0e..ac468c602c0b 100644
> > > --- a/include/linux/console.h
> > > +++ b/include/linux/console.h
> > > @@ -192,6 +192,7 @@ static inline void console_sysfs_notify(void)
> > >  { }
> > >  #endif
> > >  extern bool console_suspend_enabled;
> > > +extern int is_console_suspended(void);
> > >
> > >  /* Suspend and resume console messages over PM events */
> > >  extern void suspend_console(void);
> > > diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> > > index a7320f07689d..52b7a181b6d8 100644
> > > --- a/kernel/power/Kconfig
> > > +++ b/kernel/power/Kconfig
> > > @@ -207,6 +207,15 @@ config PM_SLEEP_DEBUG
> > >         def_bool y
> > >         depends on PM_DEBUG && PM_SLEEP
> > >
> > > +config PM_SLEEP_MONITOR
> > > +       bool "Linux kernel suspend/resume process monitor"
> > > +       depends on PM_SLEEP
> > > +       help
> > > +       This option will enable suspend/resume monitor to prevent device
> > > +       stuck during suspend/resume process. Suspend timeout handler
> > will
> > > +       dump disk sleep task at first round timeout and trigger kernel
> > panic
> > > +       at second round timeout. The default timer for each round is 30
> > seconds.
> > > +
>
> > The facility associated with the Kconfig entry right below is supposed
> > to do exactly the same thing.
>
> > What's the reason to add another one?  What is missing?
>
>
>
> > >  config DPM_WATCHDOG
> > >         bool "Device suspend/resume watchdog"
> > >         depends on PM_DEBUG && PSTORE && EXPERT
>
> Because we found some suspend hand issue that cannot be detected by
> "CONFIG_DPM_WATCHDOG" (which is focus on device PM).

What's that issue?

> Our suspend timeout monitor can cover PM core and Device PM hang issues.

Then I'd suggest to extend the existing watchdog instead of adding a
whole new implementation.