linux-kernel - [PATCH 2/3] cpufreq: intel_pstate: Use locking in intel_cpufreq_verify

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Date:   Fri, 30 Dec 2016 15:57:11 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/3] cpufreq: intel_pstate: Use locking in intel_cpufreq_verify_policy()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Race conditions are possible if intel_cpufreq_verify_policy()
is executed in parallel with global limits updates from sysfs,
so the invocation of intel_pstate_update_perf_limits() in it
should be carried out under intel_pstate_limits_lock.

Make that happen.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/intel_pstate.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -2157,8 +2157,12 @@ static int intel_cpufreq_verify_policy(s
 	if (per_cpu_limits)
 		perf_limits = cpu->perf_limits;
 
+	mutex_lock(&intel_pstate_limits_lock);
+
 	intel_pstate_update_perf_limits(policy, perf_limits);
 
+	mutex_unlock(&intel_pstate_limits_lock);
+
 	return 0;
 }