linux-kernel - Re: [PATCH] PM / EM: postpone creating the debugfs dir till fs

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Date:   Tue, 23 Mar 2021 16:26:06 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rjw@...ysocki.net, rafael@...nel.org, ionela.voinescu@....com,
        Dietmar.Eggemann@....com
Subject: Re: [PATCH] PM / EM: postpone creating the debugfs dir till
 fs_initcall

On Tue, Mar 23, 2021 at 02:56:08PM +0000, Lukasz Luba wrote:
> The debugfs directory '/sys/kernel/debug/energy_model' is needed before
> the Energy Model registration can happen. With the recent change in
> debugfs subsystem it's not allowed to create this directory at early stage
> (core_initcall). Thus creating this directory would fail.
> Postpone the creation of the EM debug dir to later stage: fs_initcall.
> It should be safe since all clients: CPUFreq drivers, Devfreq drivers will
> be initialized in later stages.
> The custom debug log below prints the time of creation the EM debug dir at
> fs_initcall and successful registration of EMs at later stages.
> 
> [    1.505717] energy_model: creating rootdir
> [    3.698307] cpu cpu0: EM: created perf domain
> [    3.709022] cpu cpu1: EM: created perf domain
> 
> fixes: 56348560d495 ("debugfs: do not attempt to create a new file before the filesystem is initalized")
> Reported-by: Ionela Voinescu <ionela.voinescu@....com>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
> Hi Rafael,
> 
> Please take this patch into your PM v5.12 fixes. The change described in
> the patch above landed in v5.12-rc1. Some of our EAS/EM tests are failing.

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>