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

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Message-ID: <20180524154505.d5r77w7xinpbc36n@linutronix.de>
Date:   Thu, 24 May 2018 17:45:05 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     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 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.

Sebastian