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

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Date:   Mon, 10 Jun 2019 10:33:51 +0800
From:   Chunyan Zhang <zhang.chunyan@...aro.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Linux Kernel Mailing List <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 Thu, 6 Jun 2019 at 09:08, Sasha Levin <sashal@...nel.org> wrote:
>
> 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 for the information and suggestion!

Chunyan

>
> --
> Thanks,
> Sasha