linux-kernel - Re: [PATCH 4.19 085/271] ACPICA: Clear status of GPEs on first direct enable

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Message-ID: <20190726175706.GB5945@xo-6d-61-c0.localdomain>
Date:   Fri, 26 Jul 2019 19:57:06 +0200
From:   Pavel Machek <pavel@....cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Furquan Shaikh <furquan@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 085/271] ACPICA: Clear status of GPEs on first
 direct enable

On Wed 2019-07-24 21:19:14, Greg Kroah-Hartman wrote:
> [ Upstream commit 44758bafa53602f2581a6857bb20b55d4d8ad5b2 ]
> 
> ACPI GPEs (other than the EC one) can be enabled in two situations.
> First, the GPEs with existing _Lxx and _Exx methods are enabled
> implicitly by ACPICA during system initialization.  Second, the
> GPEs without these methods (like GPEs listed by _PRW objects for
> wakeup devices) need to be enabled directly by the code that is
> going to use them (e.g. ACPI power management or device drivers).
> 
> In the former case, if the status of a given GPE is set to start
> with, its handler method (either _Lxx or _Exx) needs to be invoked
> to take care of the events (possibly) signaled before the GPE was
> enabled.  In the latter case, however, the first caller of
> acpi_enable_gpe() for a given GPE should not be expected to care
> about any events that might be signaled through it earlier.  In
> that case, it is better to clear the status of the GPE before
> enabling it, to prevent stale events from triggering unwanted
> actions (like spurious system resume, for example).

Given the complexity of ACPI and number of implementations, I don't
think this is safe for stable.

Notebooks are not part of automated test farms, so it did not get
nearly enough testing...

								Pavel