On Thu, Sep 4, 2025 at 12:38 PM Zihuan Zhang <zhangzihuan@xxxxxxxxxx> wrote:
>
>
> 在 2025/9/3 21:45, Rafael J. Wysocki 写道:
> > On Wed, Sep 3, 2025 at 3:18 PM Zihuan Zhang <zhangzihuan@xxxxxxxxxx> wrote:
> >> Replace the manual cpufreq_cpu_put() with __free(put_cpufreq_policy)
> >> annotation for policy references. This reduces the risk of reference
> >> counting mistakes and aligns the code with the latest kernel style.
> >>
> >> No functional change intended.
> >>
> >> Signed-off-by: Zihuan Zhang <zhangzihuan@xxxxxxxxxx>
> >> ---
> >> drivers/powercap/dtpm_cpu.c | 30 +++++++++++-------------------
> >> 1 file changed, 11 insertions(+), 19 deletions(-)
> >>
> >> diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
> >> index 99390ec1481f..f76594185fa2 100644
> >> --- a/drivers/powercap/dtpm_cpu.c
> >> +++ b/drivers/powercap/dtpm_cpu.c
> >> @@ -144,19 +144,17 @@ static int update_pd_power_uw(struct dtpm *dtpm)
> >> static void pd_release(struct dtpm *dtpm)
> >> {
> >> struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
> >> - struct cpufreq_policy *policy;
> >>
> >> if (freq_qos_request_active(&dtpm_cpu->qos_req))
> >> freq_qos_remove_request(&dtpm_cpu->qos_req);
> >>
> >> - policy = cpufreq_cpu_get(dtpm_cpu->cpu);
> >> - if (policy) {
> >> + struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> >> + cpufreq_cpu_get(dtpm_cpu->cpu);
> >> +
> >> + if (policy)
> >> for_each_cpu(dtpm_cpu->cpu, policy->related_cpus)
> >> per_cpu(dtpm_per_cpu, dtpm_cpu->cpu) = NULL;
> >>
> >> - cpufreq_cpu_put(policy);
> >> - }
> >> -
> >> kfree(dtpm_cpu);
> >> }
> >>
> >> @@ -192,7 +190,6 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
> >> static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
> >> {
> >> struct dtpm_cpu *dtpm_cpu;
> >> - struct cpufreq_policy *policy;
> >> struct em_perf_state *table;
> >> struct em_perf_domain *pd;
> >> char name[CPUFREQ_NAME_LEN];
> >> @@ -202,21 +199,19 @@ static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
> >> if (dtpm_cpu)
> >> return 0;
> >>
> >> - policy = cpufreq_cpu_get(cpu);
> >> + struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> >> + cpufreq_cpu_get(cpu);
> >> +
> >> if (!policy)
> >> return 0;
> >>
> >> pd = em_cpu_get(cpu);
> >> - if (!pd || em_is_artificial(pd)) {
> >> - ret = -EINVAL;
> >> - goto release_policy;
> >> - }
> >> + if (!pd || em_is_artificial(pd))
> >> + return -EINVAL;
> >>
> >> dtpm_cpu = kzalloc(sizeof(*dtpm_cpu), GFP_KERNEL);
> >> - if (!dtpm_cpu) {
> >> - ret = -ENOMEM;
> >> - goto release_policy;
> >> - }
> >> + if (!dtpm_cpu)
> >> + return -ENOMEM;
> >>
> >> dtpm_init(&dtpm_cpu->dtpm, &dtpm_ops);
> >> dtpm_cpu->cpu = cpu;
> >> @@ -239,7 +234,6 @@ static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
> >> if (ret < 0)
> >> goto out_dtpm_unregister;
> > So this change kind of goes against another recommendation given in cleanup.h:
> >
> > * Lastly, given that the benefit of cleanup helpers is removal of
> > * "goto", and that the "goto" statement can jump between scopes, the
> > * expectation is that usage of "goto" and cleanup helpers is never
> > * mixed in the same function. I.e. for a given routine, convert all
> > * resources that need a "goto" cleanup to scope-based cleanup, or
> > * convert none of them.
>
>
> Should I replace all the memory allocation cleanups here with `__free`?
> That would allow us to drop all the `goto`s, but since this function has
> quite a few of them, I’m concerned it might introduce new issues. What’s
> your recommendation?
Frankly, don't use __free() in this code at all, at least for the time being.
There is a problem with dropping the reference to policy at the end of
__dtpm_cpu_setup() because that policy may be subsequently indirectly
used in set_pd_power_limit() which calls
freq_qos_update_request(&dtpm_cpu->qos_req, freq) and
dtpm_cpu->qos_req->qos is policy->constraints, so using it will cause
policy->constraints to be dereferenced in freq_qos_apply() which will
crash and burn if the policy goes away in the meantime. So AFAICS
__dtpm_cpu_setup() shouldn't call cpufreq_cpu_put() at all and the
policy should be released in pd_release() without acquiring a new
reference to it.
You may as well try to fix this if you have free cycles.
