linux-kernel - Re: [PATCH v7 03/20] reboot: Print error message if restart handler has duplicated priority

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Message-ID: <af51d9d0-26ba-fc66-05f1-d92ef7172730@collabora.com>
Date:   Thu, 14 Apr 2022 01:23:52 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
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Subject: Re: [PATCH v7 03/20] reboot: Print error message if restart handler
 has duplicated priority

On 4/13/22 21:48, Rafael J. Wysocki wrote:
> On Tue, Apr 12, 2022 at 1:39 AM Dmitry Osipenko
> <dmitry.osipenko@...labora.com> wrote:
>>
>> Add sanity check which ensures that there are no two restart handlers
>> registered using the same priority. This requirement will become mandatory
>> once all drivers will be converted to the new API and such errors will be
>> fixed.
>>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> 
> The first two patches in the series are fine with me and there's only
> one minor nit regarding this one (below).
> 
>> ---
>>  kernel/reboot.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>> diff --git a/kernel/reboot.c b/kernel/reboot.c
>> index ed4e6dfb7d44..acdae4e95061 100644
>> --- a/kernel/reboot.c
>> +++ b/kernel/reboot.c
>> @@ -182,6 +182,21 @@ static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
>>   */
>>  int register_restart_handler(struct notifier_block *nb)
>>  {
>> +       int ret;
>> +
>> +       ret = atomic_notifier_chain_register_unique_prio(&restart_handler_list, nb);
>> +       if (ret != -EBUSY)
>> +               return ret;
>> +
>> +       /*
>> +        * Handler must have unique priority. Otherwise call order is
>> +        * determined by registration order, which is unreliable.
>> +        *
>> +        * This requirement will become mandatory once all drivers
>> +        * will be converted to use new sys-off API.
>> +        */
>> +       pr_err("failed to register restart handler using unique priority\n");
> 
> I would use pr_info() here, because this is not a substantial error AFAICS.

It's indeed not a substantial error so far, but it will become
substantial later on once only unique priorities will be allowed. The
pr_warn() could be a good compromise here, pr_info() is too mild, IMO.