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Date:   Thu, 05 Jul 2018 11:50:11 +0200
Message-ID: <s5hk1qaui3w.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Thomas =?UTF-8?B?SMOkbmln?= <haenig@cosifan.de>,
        Linux PM <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [REGRESSION 4.17] Spurious wakeup / reboot with power button
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On Thu, 05 Jul 2018 11:34:59 +0200,
Rafael J. Wysocki wrote:
> 
> Hi,
> 
> On Thu, Jul 5, 2018 at 9:05 AM, Takashi Iwai <tiwai@suse.de> wrote:
> > Hi,
> >
> > we've got a regression report since 4.17 about the behavior of
> > power-off with the power button.  When a machine is powered off with
> > the power button on desktop, it reboots after a few seconds instead of
> > power down.
> >
> > The manual power down via "systemctl poweroff" works fine, so it's
> > possibly some spurious wakeup by the power button action, and some
> > ACPI-related change is suspected.
> > The regression still remains in 4.18-rc3.
> 
> There are only a few ACPI commits directly related to power management
> between 4.16 and 4.17 and none of them looks particularly suspicious.

OK, interesting.

> It looks like the power button state may not be cleared sufficiently
> after it's been pressed which is now visible for some reason.

Hmm, where can such a state remain?  Since it happens after the
machine turned off, some (ACPI) wakeup bits?

> How does the button poweroff work, exactly?  I guess the event is
> collected by a user space demon which then triggers power of via sysfs
> or similar?

Usually X desktop environment receives an input event from the ACPI
power button input device, and deals the event accordingly depending
on the setup.  The power-down behavior itself should be equivalent
with "systemctl poweroff" or such.


thanks,

Takashi