linux-kernel - Re: [BACKPORT 4.4.y] PM / sleep: prohibit devices probing during suspend/hibernation

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Message-ID: <20190606010857.GF29739@sasha-vm>
Date:   Wed, 5 Jun 2019 21:08:57 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Chunyan Zhang <zhang.chunyan@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        Grygorii Strashko <grygorii.Strashko@...com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [BACKPORT 4.4.y] PM / sleep: prohibit devices probing during
 suspend/hibernation

On Wed, Jun 05, 2019 at 07:14:12PM +0800, Chunyan Zhang wrote:
>From: "Strashko, Grygorii" <grygorii.strashko@...com>
>
>[ Upstream commit 013c074f8642d8e815ad670601f8e27155a74b57 ]
>
>It is unsafe [1] if probing of devices will happen during suspend or
>hibernation and system behavior will be unpredictable in this case.
>So, let's prohibit device's probing in dpm_prepare() and defer their
>probing instead. The normal behavior will be restored in
>dpm_complete().
>
>This patch introduces new DD core APIs:
> device_block_probing()
>   It will disable probing of devices and defer their probes instead.
> device_unblock_probing()
>   It will restore normal behavior and trigger re-probing of deferred
>   devices.
>
>[1] https://lkml.org/lkml/2015/9/11/554
>
>Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>Acked-by: Pavel Machek <pavel@....cz>
>Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>

This patch had to be fixed a few times (see 015bb5e134 and 9a2a5a638f8),
we can't just take it as is.

It might be just simpler to move to a newer kernel at this point.

--
Thanks,
Sasha