Commit 41cfd64c authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
Browse files

intel_pstate: Update frequencies of policy->cpus only from ->set_policy()



The intel-pstate driver is using intel_pstate_hwp_set() from two
separate paths, i.e. ->set_policy() callback and sysfs update path for
the files present in /sys/devices/system/cpu/intel_pstate/ directory.

While an update to the sysfs path applies to all the CPUs being managed
by the driver (which essentially means all the online CPUs), the update
via the ->set_policy() callback applies to a smaller group of CPUs
managed by the policy for which ->set_policy() is called.

And so, intel_pstate_hwp_set() should update frequencies of only the
CPUs that are part of policy->cpus mask, while it is called from
->set_policy() callback.

In order to do that, add a parameter (cpumask) to intel_pstate_hwp_set()
and apply the frequency changes only to the concerned CPUs.

For ->set_policy() path, we are only concerned about policy->cpus, and
so policy->rwsem lock taken by the core prior to calling ->set_policy()
is enough to take care of any races. The larger lock acquired by
get_online_cpus() is required only for the updates to sysfs files.

Add another routine, intel_pstate_hwp_set_online_cpus(), and call it
from the sysfs update paths.

This also fixes a lockdep reported recently, where policy->rwsem and
get_online_cpus() could have been acquired in any order causing an ABBA
deadlock. The sequence of events leading to that was:

intel_pstate_init(...)
	...cpufreq_online(...)
		down_write(&policy->rwsem); // Locks policy->rwsem
		...
		cpufreq_init_policy(policy);
			...intel_pstate_hwp_set();
				get_online_cpus(); // Temporarily locks cpu_hotplug.lock
		...
		up_write(&policy->rwsem);

pm_suspend(...)
	...disable_nonboot_cpus()
		_cpu_down()
			cpu_hotplug_begin(); // Locks cpu_hotplug.lock
			__cpu_notify(CPU_DOWN_PREPARE, ...);
				...cpufreq_offline_prepare();
					down_write(&policy->rwsem); // Locks policy->rwsem
Reported-and-tested-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent fd7dc7e6
......@@ -286,7 +286,7 @@ static inline void update_turbo_state(void)
cpu->pstate.max_pstate == cpu->pstate.turbo_pstate);
}
static void intel_pstate_hwp_set(void)
static void intel_pstate_hwp_set(const struct cpumask *cpumask)
{
int min, hw_min, max, hw_max, cpu, range, adj_range;
u64 value, cap;
......@@ -296,9 +296,7 @@ static void intel_pstate_hwp_set(void)
hw_max = HWP_HIGHEST_PERF(cap);
range = hw_max - hw_min;
get_online_cpus();
for_each_online_cpu(cpu) {
for_each_cpu(cpu, cpumask) {
rdmsrl_on_cpu(cpu, MSR_HWP_REQUEST, &value);
adj_range = limits->min_perf_pct * range / 100;
min = hw_min + adj_range;
......@@ -317,7 +315,12 @@ static void intel_pstate_hwp_set(void)
value |= HWP_MAX_PERF(max);
wrmsrl_on_cpu(cpu, MSR_HWP_REQUEST, value);
}
}
static void intel_pstate_hwp_set_online_cpus(void)
{
get_online_cpus();
intel_pstate_hwp_set(cpu_online_mask);
put_online_cpus();
}
......@@ -439,7 +442,7 @@ static ssize_t store_no_turbo(struct kobject *a, struct attribute *b,
limits->no_turbo = clamp_t(int, input, 0, 1);
if (hwp_active)
intel_pstate_hwp_set();
intel_pstate_hwp_set_online_cpus();
return count;
}
......@@ -465,7 +468,7 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b,
int_tofp(100));
if (hwp_active)
intel_pstate_hwp_set();
intel_pstate_hwp_set_online_cpus();
return count;
}
......@@ -490,7 +493,7 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b,
int_tofp(100));
if (hwp_active)
intel_pstate_hwp_set();
intel_pstate_hwp_set_online_cpus();
return count;
}
......@@ -1141,7 +1144,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
pr_debug("intel_pstate: set performance\n");
limits = &performance_limits;
if (hwp_active)
intel_pstate_hwp_set();
intel_pstate_hwp_set(policy->cpus);
return 0;
}
......@@ -1173,7 +1176,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
int_tofp(100));
if (hwp_active)
intel_pstate_hwp_set();
intel_pstate_hwp_set(policy->cpus);
return 0;
}
......
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