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| author | Vikram Mulukutla <markivx@codeaurora.org> | 2017-07-06 19:53:20 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2017-07-12 14:47:48 +0200 |
| commit | ab2f7cf141aa6734c4ca7525132d8cc236efee77 (patch) | |
| tree | 6a2e41128c88d4843b795f566c69c3d572708871 | |
| parent | Linux 4.12 (diff) | |
| download | linux-ab2f7cf141aa6734c4ca7525132d8cc236efee77.tar.xz linux-ab2f7cf141aa6734c4ca7525132d8cc236efee77.zip | |
cpufreq: schedutil: Fix sugov_start() versus sugov_update_shared() race
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>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | kernel/sched/cpufreq_schedutil.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 076a2e31951c..29a397067ffa 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 : |