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Power management fix for 6.12 (final)

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Fix a locking issue in the asymmetric CPU capacity setup code in the
 intel_pstate driver that may lead to a deadlock if CPU online/offline
 runs in parallel with the code in question, which is unlikely but not
 impossible (Rafael Wysocki).
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Merge tag 'pm-6.12-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fix from Rafael Wysocki:
 "Fix a locking issue in the asymmetric CPU capacity setup code in the
  intel_pstate driver that may lead to a deadlock if CPU online/offline
  runs in parallel with the code in question, which is unlikely but not
  impossible (Rafael Wysocki)"

* tag 'pm-6.12-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  cpufreq: intel_pstate: Rearrange locking in hybrid_init_cpu_capacity_scaling()
This commit is contained in:
Linus Torvalds 2024-11-13 13:32:51 -08:00
commit 0a9b9d17f3
1 changed files with 17 additions and 20 deletions
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37
drivers/cpufreq/intel_pstate.c
View File

@ -1028,26 +1028,29 @@ static void hybrid_update_cpu_capacity_scaling(void)
}
}
static void __hybrid_init_cpu_capacity_scaling(void)
static void __hybrid_refresh_cpu_capacity_scaling(void)
{
hybrid_max_perf_cpu = NULL;
hybrid_update_cpu_capacity_scaling();
}
static void hybrid_refresh_cpu_capacity_scaling(void)
{
guard(mutex)(&hybrid_capacity_lock);
__hybrid_refresh_cpu_capacity_scaling();
}
static void hybrid_init_cpu_capacity_scaling(bool refresh)
{
bool disable_itmt = false;
mutex_lock(&hybrid_capacity_lock);
/*
* If hybrid_max_perf_cpu is set at this point, the hybrid CPU capacity
* scaling has been enabled already and the driver is just changing the
* operation mode.
*/
if (refresh) {
__hybrid_init_cpu_capacity_scaling();
goto unlock;
hybrid_refresh_cpu_capacity_scaling();
return;
}
/*
@ -1056,19 +1059,13 @@ static void hybrid_init_cpu_capacity_scaling(bool refresh)
* do not do that when SMT is in use.
*/
if (hwp_is_hybrid && !sched_smt_active() && arch_enable_hybrid_capacity_scale()) {
__hybrid_init_cpu_capacity_scaling();
disable_itmt = true;
}
unlock:
mutex_unlock(&hybrid_capacity_lock);
/*
* Disabling ITMT causes sched domains to be rebuilt to disable asym
* packing and enable asym capacity.
*/
if (disable_itmt)
hybrid_refresh_cpu_capacity_scaling();
/*
* Disabling ITMT causes sched domains to be rebuilt to disable asym
* packing and enable asym capacity.
*/
sched_clear_itmt_support();
}
}
static bool hybrid_clear_max_perf_cpu(void)
@ -1404,7 +1401,7 @@ static void intel_pstate_update_limits_for_all(void)
mutex_lock(&hybrid_capacity_lock);
if (hybrid_max_perf_cpu)
__hybrid_init_cpu_capacity_scaling();
__hybrid_refresh_cpu_capacity_scaling();
mutex_unlock(&hybrid_capacity_lock);
}