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

[Zhongqiu Han]

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@xxxxxxx>
> > Reviewed-by: Pengjie Zhang <zhangpengjie2@xxxxxxxxxx>
> > ---
> >   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@xxxxxxxxxx/

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@xxxxxxx/



> Thanks,
> Sumit


--
Thx and BRs,
Zhongqiu Han