linux-kernel - [PATCH 1/3] cpufreq: intel_pstate: Use locking in intel_pstate

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Date:   Fri, 30 Dec 2016 15:56:14 +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 1/3] cpufreq: intel_pstate: Use locking in intel_pstate_resume()

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

Theoretically, intel_pstate_resume() may be executed in parallel
with intel_pstate_set_policy(), if the latter is invoked via
cpufreq_update_policy() as a result of a notification, so use
intel_pstate_limits_lock in there too to avoid race conditions.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/intel_pstate.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -968,12 +968,20 @@ static int intel_pstate_hwp_save_state(s
 
 static int intel_pstate_resume(struct cpufreq_policy *policy)
 {
+	int ret;
+
 	if (!hwp_active)
 		return 0;
 
+	mutex_lock(&intel_pstate_limits_lock);
+
 	all_cpu_data[policy->cpu]->epp_policy = 0;
 
-	return intel_pstate_hwp_set_policy(policy);
+	ret = intel_pstate_hwp_set_policy(policy);
+
+	mutex_unlock(&intel_pstate_limits_lock);
+
+	return ret;
 }
 
 static void intel_pstate_hwp_set_online_cpus(void)