linux-kernel - Re: linux-next: Tree for Apr 9 [cpufreq: NULL pointer deref]

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Date:	Mon, 15 Apr 2013 22:52:28 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
Cc:	sedat.dilek@...il.com, "Rafael J. Wysocki" <rjw@...k.pl>,
	Dirk Brandewie <dirk.j.brandewie@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org, Linux PM list <linux-pm@...r.kernel.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Nathan Zimmer <nzimmer@....com>
Subject: Re: linux-next: Tree for Apr 9 [cpufreq: NULL pointer deref]

On 15 April 2013 21:37, Dirk Brandewie <dirk.brandewie@...il.com> wrote:
> If the intel_pstate driver is being used __cpufreq_governor() should NOT be
> called intel_pstate does not implement the target() callback.
>
> Nathan's commit 5800043b2 changed the fence around the call to
> __cpufreq_governor() in __cpufreq_remove_dev() here is the relevant hunk.

No it isn't.

> +       if (has_target)
>                 __cpufreq_governor(data, CPUFREQ_GOV_STOP);

As it has taken care of this limitation.

BUT some of my earlier patches haven't. :(
Here is the fix (Sedat please try this and give your tested-by, use the attached
patch as gmail might break what i am copying in mail)..

Sorry for being late in fixing this issue, i am still down with Tonsil infection
and fever.. Today only i got some power to fix it after seeing Dirk's mail.

Your tested-by may help me to recover quickly :)

@Rafael: I will probably be down for one more week and so not doing any
reviews for now... I do check important mails sent directly to me though.

------------x----------------------x------------------

From: Viresh Kumar <viresh.kumar@...aro.org>
Date: Mon, 15 Apr 2013 22:43:57 +0530
Subject: [PATCH] cpufreq: Don't call __cpufreq_governor() for drivers without
 target()

Some cpufreq drivers implement their own governor and so don't need us to call
generic governors interface via __cpufreq_governor(). Few recent commits haven't
obeyed this law well and we saw some regressions.

This patch tries to fix this issue.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cpufreq.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 3564947..a6f6595 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -858,13 +858,18 @@ static int cpufreq_add_policy_cpu(unsigned int
cpu, unsigned int sibling,
 				  struct device *dev)
 {
 	struct cpufreq_policy *policy;
-	int ret = 0;
+	int ret = 0, has_target = 0;
 	unsigned long flags;

 	policy = cpufreq_cpu_get(sibling);
 	WARN_ON(!policy);

-	__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+	rcu_read_lock();
+	has_target = !!rcu_dereference(cpufreq_driver)->target;
+	rcu_read_unlock();
+
+	if (has_target)
+		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);

 	lock_policy_rwsem_write(sibling);

@@ -877,8 +882,10 @@ static int cpufreq_add_policy_cpu(unsigned int
cpu, unsigned int sibling,

 	unlock_policy_rwsem_write(sibling);

-	__cpufreq_governor(policy, CPUFREQ_GOV_START);
-	__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+	if (has_target) {
+		__cpufreq_governor(policy, CPUFREQ_GOV_START);
+		__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+	}

 	ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
 	if (ret) {
@@ -1146,7 +1153,8 @@ static int __cpufreq_remove_dev(struct device
*dev, struct subsys_interface *sif

 	/* If cpu is last user of policy, free policy */
 	if (cpus == 1) {
-		__cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);
+		if (has_target)
+			__cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);

 		lock_policy_rwsem_read(cpu);
 		kobj = &data->kobj;

Download attachment "0001-cpufreq-Don-t-call-__cpufreq_governor-for-drivers-wi.patch" of type "application/octet-stream" (2279 bytes)