Hi Mike, On 08/07/15 16:19, Michael Turquette wrote: > Quoting Morten Rasmussen (2015-07-07 11:24:22) >> From: Juri Lelli <juri.le...@arm.com> >> >> Introduce a static key to only affect scheduler hot paths when sched >> governor is enabled. >> >> cc: Ingo Molnar <mi...@redhat.com> >> cc: Peter Zijlstra <pet...@infradead.org> >> >> Signed-off-by: Juri Lelli <juri.le...@arm.com> >> --- >> kernel/sched/cpufreq_sched.c | 14 ++++++++++++++ >> kernel/sched/fair.c | 1 + >> kernel/sched/sched.h | 6 ++++++ >> 3 files changed, 21 insertions(+) >> >> diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c >> index 5020f24..2968f3a 100644 >> --- a/kernel/sched/cpufreq_sched.c >> +++ b/kernel/sched/cpufreq_sched.c >> @@ -203,6 +203,18 @@ void cpufreq_sched_set_cap(int cpu, unsigned long >> capacity) >> return; >> } >> >> +static inline void set_sched_energy_freq(void) >> +{ >> + if (!sched_energy_freq()) >> + static_key_slow_inc(&__sched_energy_freq); >> +} >> + >> +static inline void clear_sched_energy_freq(void) >> +{ >> + if (sched_energy_freq()) >> + static_key_slow_dec(&__sched_energy_freq); >> +} >> + >> static int cpufreq_sched_start(struct cpufreq_policy *policy) >> { >> struct gov_data *gd; >> @@ -243,6 +255,7 @@ static int cpufreq_sched_start(struct cpufreq_policy >> *policy) >> >> policy->governor_data = gd; >> gd->policy = policy; >> + set_sched_energy_freq(); >> return 0; >> >> err: >> @@ -254,6 +267,7 @@ static int cpufreq_sched_stop(struct cpufreq_policy >> *policy) >> { >> struct gov_data *gd = policy->governor_data; >> >> + clear_sched_energy_freq(); > > <paranoia> > > These controls are exposed to userspace via cpufreq sysfs knobs. Should > we use a struct static_key_deferred and static_key_slow_dec_deferred() > instead? This helps avoid a possible attack vector for slowing down the > system. > > </paranoia> > > I don't really know what a sane default rate limit would be in that case > though.
I guess we could go with HZ, as it seems to be the common default. > Otherwise feel free to add: > > Reviewed-by: Michael Turquette <mturque...@baylibre.com> > Thanks, - Juri > Regards, > Mike > >> if (cpufreq_driver_might_sleep()) { >> kthread_stop(gd->task); >> } >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index f7cb6c9..d395bc9 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -4282,6 +4282,7 @@ static inline void hrtick_update(struct rq *rq) >> #endif >> >> static bool cpu_overutilized(int cpu); >> +struct static_key __sched_energy_freq __read_mostly = STATIC_KEY_INIT_FALSE; >> >> /* >> * The enqueue_task method is called before nr_running is >> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >> index 30aa0c4..b5e27d9 100644 >> --- a/kernel/sched/sched.h >> +++ b/kernel/sched/sched.h >> @@ -1476,6 +1476,12 @@ unsigned long arch_scale_cpu_capacity(struct >> sched_domain *sd, int cpu) >> } >> #endif >> >> +extern struct static_key __sched_energy_freq; >> +static inline bool sched_energy_freq(void) >> +{ >> + return static_key_false(&__sched_energy_freq); >> +} >> + >> #ifdef CONFIG_CPU_FREQ_GOV_SCHED >> void cpufreq_sched_set_cap(int cpu, unsigned long util); >> #else >> -- >> 1.9.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/