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

[Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>]

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/



> Thanks,
> Sumit
> 
> 


-- 
Thx and BRs,
Zhongqiu Han