Re: [PATCH v1] cpufreq: Avoid get_governor() for first policy

[Zihuan Zhang]

Hi,

在 2025/7/24 19:28, zhenglifeng (A) 写道:
> On 2025/7/24 17:36, Zihuan Zhang wrote:
>
> > When a cpufreq driver registers the first policy, it may attempt to
> > initialize the policy governor from `last_governor`. However, this is
> > meaningless for the first policy instance, because `last_governor` is
> > only updated when policies are removed (e.g. during CPU offline).
> >
> > The `last_governor` mechanism is intended to restore the previously
> > used governor across CPU hotplug events. For the very first policy,
> > there is no "previous governor" to restore, so calling
> > get_governor(last_governor) is unnecessary and potentially confusing.
> >
> > This patch skips looking up `last_governor` when registering the first
> > policy. Instead, it directly uses the default governor after all
> > governors have been registered and are available.
> >
> > This avoids meaningless lookups, reduces unnecessary module reference
> > handling, and simplifies the initial policy path.
> >
> > Signed-off-by: Zihuan Zhang <zhangzihuan@xxxxxxxxxx>
> > ---
> >   drivers/cpufreq/cpufreq.c | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index d7426e1d8bdd..b5ebd4519eab 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -1121,9 +1121,9 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
> >   	int ret;
> >   
> >   	if (has_target()) {
> > -		/* Update policy governor to the one used before hotplug. */
> > -		gov = get_governor(policy->last_governor);
> > -		if (gov) {
> > +		if (policy->last_governor[0] != '\0') {
> > +			/* Update policy governor to the one used before hotplug. */
> > +			gov = get_governor(policy->last_governor);
> What if gov is null here? For example, the last governor has been removed.
> The default governor should be used in this situation I think.
Thank you for pointing it out, I will fix it in the next version.

> >   			pr_debug("Restoring governor %s for cpu %d\n",
> >   				 gov->name, policy->cpu);
> >   		} else {