| Message ID | 1499363600-10732-1-git-send-email-markivx@codeaurora.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On Thursday, July 06, 2017 10:53:20 AM Vikram Mulukutla wrote: > With a shared policy in place, when one of the CPUs in the policy is > hotplugged out and then brought back online, sugov_stop and > sugov_start are called in order. > > sugov_stop removes utilization hooks for each CPU in the policy and > does nothing else in the for_each_cpu loop. sugov_start on the other > hand iterates through the CPUs in the policy and re-initializes the > per-cpu structure _and_ adds the utilization hook. This implies that > the scheduler is allowed to invoke a CPU's utilization update hook > when the rest of the per-cpu structures have yet to be re-inited. > > Apart from some strange values in tracepoints this doesn't cause a > problem, but if we do end up accessing a pointer from the per-cpu > sugov_cpu structure somewhere in the sugov_update_shared path, > we will likely see crashes since the memset for another CPU in the > policy is free to race with sugov_update_shared from the CPU that is > ready to go. So let's fix this now to first init all per-cpu > structures, and then add the per-cpu utilization update hooks all at > once. > > Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org> OK Any objections anyone? > --- > kernel/sched/cpufreq_schedutil.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 076a2e3..29a3970 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -610,6 +610,11 @@ static int sugov_start(struct cpufreq_policy *policy) > sg_cpu->sg_policy = sg_policy; > sg_cpu->flags = SCHED_CPUFREQ_RT; > sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq; > + } > + > + for_each_cpu(cpu, policy->cpus) { > + struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu); > + > cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, > policy_is_shared(policy) ? > sugov_update_shared : >
On 06-07-17, 10:53, Vikram Mulukutla wrote: > With a shared policy in place, when one of the CPUs in the policy is > hotplugged out and then brought back online, sugov_stop and > sugov_start are called in order. > > sugov_stop removes utilization hooks for each CPU in the policy and > does nothing else in the for_each_cpu loop. sugov_start on the other > hand iterates through the CPUs in the policy and re-initializes the > per-cpu structure _and_ adds the utilization hook. This implies that > the scheduler is allowed to invoke a CPU's utilization update hook > when the rest of the per-cpu structures have yet to be re-inited. > > Apart from some strange values in tracepoints this doesn't cause a > problem, but if we do end up accessing a pointer from the per-cpu > sugov_cpu structure somewhere in the sugov_update_shared path, > we will likely see crashes since the memset for another CPU in the > policy is free to race with sugov_update_shared from the CPU that is > ready to go. So let's fix this now to first init all per-cpu > structures, and then add the per-cpu utilization update hooks all at > once. > > Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org> > --- > kernel/sched/cpufreq_schedutil.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 076a2e3..29a3970 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -610,6 +610,11 @@ static int sugov_start(struct cpufreq_policy *policy) > sg_cpu->sg_policy = sg_policy; > sg_cpu->flags = SCHED_CPUFREQ_RT; > sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq; > + } > + > + for_each_cpu(cpu, policy->cpus) { > + struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu); > + > cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, > policy_is_shared(policy) ? > sugov_update_shared : Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
On Friday, July 07, 2017 08:55:09 AM Viresh Kumar wrote: > On 06-07-17, 10:53, Vikram Mulukutla wrote: > > With a shared policy in place, when one of the CPUs in the policy is > > hotplugged out and then brought back online, sugov_stop and > > sugov_start are called in order. > > > > sugov_stop removes utilization hooks for each CPU in the policy and > > does nothing else in the for_each_cpu loop. sugov_start on the other > > hand iterates through the CPUs in the policy and re-initializes the > > per-cpu structure _and_ adds the utilization hook. This implies that > > the scheduler is allowed to invoke a CPU's utilization update hook > > when the rest of the per-cpu structures have yet to be re-inited. > > > > Apart from some strange values in tracepoints this doesn't cause a > > problem, but if we do end up accessing a pointer from the per-cpu > > sugov_cpu structure somewhere in the sugov_update_shared path, > > we will likely see crashes since the memset for another CPU in the > > policy is free to race with sugov_update_shared from the CPU that is > > ready to go. So let's fix this now to first init all per-cpu > > structures, and then add the per-cpu utilization update hooks all at > > once. > > > > Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org> > > --- > > kernel/sched/cpufreq_schedutil.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > > index 076a2e3..29a3970 100644 > > --- a/kernel/sched/cpufreq_schedutil.c > > +++ b/kernel/sched/cpufreq_schedutil.c > > @@ -610,6 +610,11 @@ static int sugov_start(struct cpufreq_policy *policy) > > sg_cpu->sg_policy = sg_policy; > > sg_cpu->flags = SCHED_CPUFREQ_RT; > > sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq; > > + } > > + > > + for_each_cpu(cpu, policy->cpus) { > > + struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu); > > + > > cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, > > policy_is_shared(policy) ? > > sugov_update_shared : > > Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Applied, thanks!
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 076a2e3..29a3970 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -610,6 +610,11 @@ static int sugov_start(struct cpufreq_policy *policy) sg_cpu->sg_policy = sg_policy; sg_cpu->flags = SCHED_CPUFREQ_RT; sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq; + } + + for_each_cpu(cpu, policy->cpus) { + struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu); + cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, policy_is_shared(policy) ? sugov_update_shared :
With a shared policy in place, when one of the CPUs in the policy is hotplugged out and then brought back online, sugov_stop and sugov_start are called in order. sugov_stop removes utilization hooks for each CPU in the policy and does nothing else in the for_each_cpu loop. sugov_start on the other hand iterates through the CPUs in the policy and re-initializes the per-cpu structure _and_ adds the utilization hook. This implies that the scheduler is allowed to invoke a CPU's utilization update hook when the rest of the per-cpu structures have yet to be re-inited. Apart from some strange values in tracepoints this doesn't cause a problem, but if we do end up accessing a pointer from the per-cpu sugov_cpu structure somewhere in the sugov_update_shared path, we will likely see crashes since the memset for another CPU in the policy is free to race with sugov_update_shared from the CPU that is ready to go. So let's fix this now to first init all per-cpu structures, and then add the per-cpu utilization update hooks all at once. Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org> --- kernel/sched/cpufreq_schedutil.c | 5 +++++ 1 file changed, 5 insertions(+)