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

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Message-ID: <39cee1e7-c085-88d2-9b3b-e4ffbbee04eb@arm.com>
Date:   Tue, 23 Mar 2021 15:57:51 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
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 3/23/21 3:26 PM, Greg KH wrote:
> 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>
> 

Thank you Greg!

Regards,
Lukasz