linux-kernel - [RFC PATCH 17/19] cpufreq: stop checking for cpufreq_driver being present in cpufreq_cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 11 Jan 2016 17:35:58 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-pm@...r.kernel.org, peterz@...radead.org, rjw@...ysocki.net,
	viresh.kumar@...aro.org, mturquette@...libre.com,
	steve.muckle@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com,
	juri.lelli@....com
Subject: [RFC PATCH 17/19] cpufreq: stop checking for cpufreq_driver being present in cpufreq_cpu_get

After cpufreq_driver_lock() is acquired in cpufreq_cpu_get() we are sure
we can't race with cpufreq_policy_free() (which is in the path that ends
up removing cpufreq_driver). We can thus safely remove check for
cpufreq_driver being present (which is a leftover from commit
6eed9404ab3c ("cpufreq: Use rwsem for protecting critical sections")).

Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Juri Lelli <juri.lelli@....com>
---
 drivers/cpufreq/cpufreq.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 797bfae..6c9bef7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -282,15 +282,15 @@ struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
 	if (WARN_ON(cpu >= nr_cpu_ids))
 		return NULL;
 
-	/* get the cpufreq driver */
 	read_lock_irqsave(&cpufreq_driver_lock, flags);
 
-	if (cpufreq_driver) {
-		/* get the CPU */
-		policy = cpufreq_cpu_get_raw(cpu);
-		if (policy)
-			kobject_get(&policy->kobj);
-	}
+	/*
+	 * If we get a policy, cpufreq_policy_free() didn't
+	 * yet run.
+	 */
+	policy = cpufreq_cpu_get_raw(cpu);
+	if (policy)
+		kobject_get(&policy->kobj);
 
 	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
-- 
2.2.2