Re: [PATCH v2 2/2] cpufreq: Serialize global boost updates

[Sumit Gupta <sumitg@nvidia.com>]

On 05/11/26 20:31, Zhongqiu Han wrote:
> External email: Use caution opening links or attachments
> 
> 
> On 11/5/2026 10:41 PM, Sumit Gupta wrote:
>>
>>
>> On 05/11/26 14:33, Christian Loehle wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> Serialize concurrent global boost sysfs writes with a mutex.
>>>
>>> Fixes: 6f19efc0a1ca ("cpufreq: Add boost frequency support in core")
>>> Signed-off-by: Christian Loehle <christian.loehle@arm.com>
>>> Reviewed-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>> ---
>>>   drivers/cpufreq/cpufreq.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>> index 23a77f5524df..d95c849f79c5 100644
>>> --- a/drivers/cpufreq/cpufreq.c
>>> +++ b/drivers/cpufreq/cpufreq.c
>>> @@ -2810,6 +2810,8 @@ int cpufreq_boost_set_sw(struct cpufreq_policy
>>> *policy, int state)
>>>   }
>>>   EXPORT_SYMBOL_GPL(cpufreq_boost_set_sw);
>>>
>>> +static DEFINE_MUTEX(cpufreq_boost_mutex);
>>> +
>>>   static int cpufreq_boost_trigger_state(int state)
>>>   {
>>>          struct cpufreq_policy *policy;
>>> @@ -2817,6 +2819,8 @@ static int cpufreq_boost_trigger_state(int state)
>>>          bool boost_enabled;
>>>          int ret = -EOPNOTSUPP;
>>>
>>> +       guard(mutex)(&cpufreq_boost_mutex);
>>> +
>>
>>
>> The policy->rwsem case from [1] seems to be still open. The per-policy
>> boost attribute calls policy_set_boost() with policy->rwsem held, but
>> cpufreq_boost_trigger_state() and cpufreq_online() don't, so they can
>> race with per-policy writers like ospm_nominal_freq in [1].
>>
>> Could cpufreq_boost_trigger_state() take the policy lock, as
>> cpufreq_suspend() does?
>>
>>    scoped_guard(cpufreq_policy_write, policy)
>>        ret = policy_set_boost(policy, state);
>>
>> [1] https://lore.kernel.org/lkml/20261030172745.2045743-4-
>> sumitg@nvidia.com/
>>
> 
> Hi Sumit,
> 
> Could you please check whether the following patch addresses the issue
> you mentioned?
> 
> https://lore.kernel.org/all/be3739f8-e668-4711-912c-91459d77ed35@arm.com/
> 
> 
Yes, that covers it. I missed that. Please ignore my comment.

Reviewed-by: Sumit Gupta <sumitg@nvidia.com>

Thanks,
Sumit