linux-kernel - Re: [Update][PATCH] cpufreq: Do not hold driver module references for additional policy CPUs

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]

Message-ID: <CAKohpon7jyJWhf+j-M6Nuqy-AaY73YUpBpt-1uh12e_SYRv2bQ@mail.gmail.com>
Date:	Fri, 2 Aug 2013 16:25:58 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux PM list <linux-pm@...r.kernel.org>, cpufreq@...r.kernel.org,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: Re: [Update][PATCH] cpufreq: Do not hold driver module references for
 additional policy CPUs

On 2 August 2013 10:07, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>> @@ -908,7 +905,8 @@ static int cpufreq_add_policy_cpu(unsign
>>         unsigned long flags;
>>
>>         policy = cpufreq_cpu_get(sibling);
>
> This can be skipped completely at this place. Caller of
> cpufreq_add_policy_cpu() has got the policy pointer with it and so
> can be passed. I haven't done it earlier as the impression was we need
> to call cpufreq_cpu_get()..

And here is the fixup to do this (attached too):

---
 drivers/cpufreq/cpufreq.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 46e70ae..47f2a6e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -889,21 +889,17 @@ static void cpufreq_init_policy(struct
cpufreq_policy *policy)
 }

 #ifdef CONFIG_HOTPLUG_CPU
-static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
-				  struct device *dev, bool frozen)
+static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
+				  unsigned int cpu, struct device *dev,
+				  bool frozen)
 {
-	struct cpufreq_policy *policy;
 	int ret = 0, has_target = !!cpufreq_driver->target;
 	unsigned long flags;

-	policy = cpufreq_cpu_get(sibling);
-	if (WARN_ON_ONCE(!policy))
-		return -ENODATA;
-
 	if (has_target)
 		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);

-	lock_policy_rwsem_write(sibling);
+	lock_policy_rwsem_write(policy->cpu);

 	write_lock_irqsave(&cpufreq_driver_lock, flags);

@@ -912,7 +908,7 @@ static int cpufreq_add_policy_cpu(unsigned int
cpu, unsigned int sibling,
 	per_cpu(cpufreq_cpu_data, cpu) = policy;
 	write_unlock_irqrestore(&cpufreq_driver_lock, flags);

-	unlock_policy_rwsem_write(sibling);
+	unlock_policy_rwsem_write(policy->cpu);

 	if (has_target) {
 		__cpufreq_governor(policy, CPUFREQ_GOV_START);
@@ -923,7 +919,6 @@ static int cpufreq_add_policy_cpu(unsigned int
cpu, unsigned int sibling,
 	if (!frozen)
 		ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");

-	cpufreq_cpu_put(policy);
 	return ret;
 }
 #endif
@@ -1006,8 +1001,7 @@ static int __cpufreq_add_dev(struct device *dev,
struct subsys_interface *sif,
 		struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
 		if (cp && cpumask_test_cpu(cpu, cp->related_cpus)) {
 			read_unlock_irqrestore(&cpufreq_driver_lock, flags);
-			return cpufreq_add_policy_cpu(cpu, sibling, dev,
-						      frozen);
+			return cpufreq_add_policy_cpu(cp, cpu, dev, frozen);
 		}
 	}
 	read_unlock_irqrestore(&cpufreq_driver_lock, flags);

Download attachment "0001-Fix.patch" of type "application/octet-stream" (2437 bytes)