linux-kernel - Re: [PATCH RFC] suspend: Prevent might sleep splats

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Date:   Thu, 24 May 2018 17:57:56 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH RFC] suspend: Prevent might sleep splats

On Thu, May 24, 2018 at 5:45 PM, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
> On 2018-05-24 17:07:16 [+0200], Rafael J. Wysocki wrote:
>> On Thu, May 24, 2018 at 4:24 PM, Sebastian Andrzej Siewior
>> <bigeasy@...utronix.de> wrote:
>> > From: Thomas Gleixner <tglx@...utronix.de>
>> >
>> > timekeeping suspend/resume calls read_persistent_clock() which takes
>> > rtc_lock. That results in might sleep warnings because at that point
>> > we run with interrupts disabled.
>> >
>> > We cannot convert rtc_lock to a raw spinlock as that would trigger
>> > other might sleep warnings.
>> >
>> > As a workaround we disable the might sleep warnings by setting
>> > system_state to SYSTEM_SUSPEND before calling sysdev_suspend() and
>> > restoring it to SYSTEM_RUNNING afer sysdev_resume().
>> >
>> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>>
>> Hmm.  Don't we also need to cover suspend-to-idle?
>
> Well, if you agree with the approach then I would look into it.

As long as the SYSTEM_SUSPEND system state is defined unambiguously, I
don't have a problem with doing this.