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[PATCH] cpufreq: Make cpufreq_quick_get() safe to call.

Started byRichard Cochran <rcochran@linutronix.de>
First post2016-03-10 16:20 +0100
Last post2016-03-12 01:00 +0100
Articles 5 — 4 participants

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  [PATCH] cpufreq: Make cpufreq_quick_get() safe to call. Richard Cochran <rcochran@linutronix.de> - 2016-03-10 16:20 +0100
    Re: [PATCH] cpufreq: Make cpufreq_quick_get() safe to call. "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-03-10 23:20 +0100
      Re: [PATCH] cpufreq: Make cpufreq_quick_get() safe to call. "Rafael J. Wysocki" <rafael@kernel.org> - 2016-03-11 03:30 +0100
        [PATCH v2] cpufreq: Make cpufreq_quick_get() safe to call. Richard Cochran <rcochran@linutronix.de> - 2016-03-11 09:50 +0100
          Re: [PATCH v2] cpufreq: Make cpufreq_quick_get() safe to call. Viresh Kumar <viresh.kumar@linaro.org> - 2016-03-12 01:00 +0100

#1355189 — [PATCH] cpufreq: Make cpufreq_quick_get() safe to call.

FromRichard Cochran <rcochran@linutronix.de>
Date2016-03-10 16:20 +0100
Subject[PATCH] cpufreq: Make cpufreq_quick_get() safe to call.
Message-ID<rbaxz-jy-3@gated-at.bofh.it>
The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
its fields without taking the associated lock, cpufreq_driver_lock.

Without the locking, nothing guarantees that 'cpufreq_driver' remains
consistent during the call.  This patch fixes the issue by taking the lock
before accessing the data structure.

Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
---
 drivers/cpufreq/cpufreq.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e979ec7..ce02b2b 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1457,9 +1457,17 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
 {
 	struct cpufreq_policy *policy;
 	unsigned int ret_freq = 0;
+	unsigned long flags;
+
+	read_lock_irqsave(&cpufreq_driver_lock, flags);
 
 	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
-		return cpufreq_driver->get(cpu);
+		ret_freq = cpufreq_driver->get(cpu);
+
+	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+	if (ret_freq)
+		return ret_freq;
 
 	policy = cpufreq_cpu_get(cpu);
 	if (policy) {
-- 
2.1.4

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#1355425

From"Rafael J. Wysocki" <rjw@rjwysocki.net>
Date2016-03-10 23:20 +0100
Message-ID<rbh62-4Y2-5@gated-at.bofh.it>
In reply to#1355189
On Thursday, March 10, 2016 04:10:36 PM Richard Cochran wrote:
> The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
> its fields without taking the associated lock, cpufreq_driver_lock.
> 
> Without the locking, nothing guarantees that 'cpufreq_driver' remains
> consistent during the call.  This patch fixes the issue by taking the lock
> before accessing the data structure.
> 
> Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Signed-off-by: Richard Cochran <rcochran@linutronix.de>

Can you please CC PM-related patches to linux-pm@vger.kernel.org?  They
are much easier to handle for me then.

> ---
>  drivers/cpufreq/cpufreq.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index e979ec7..ce02b2b 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1457,9 +1457,17 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
>  {
>  	struct cpufreq_policy *policy;
>  	unsigned int ret_freq = 0;
> +	unsigned long flags;
> +
> +	read_lock_irqsave(&cpufreq_driver_lock, flags);
>  
>  	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
> -		return cpufreq_driver->get(cpu);
> +		ret_freq = cpufreq_driver->get(cpu);
> +
> +	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
> +
> +	if (ret_freq)
> +		return ret_freq;
>  
>  	policy = cpufreq_cpu_get(cpu);
>  	if (policy) {
> 

I would prefer something like this:

	read_lock_irqsave(&cpufreq_driver_lock, flags);

  	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) {
		unsigned int ret_freq = cpufreq_driver->get(cpu);

		read_unlock_irqrestore(&cpufreq_driver_lock, flags);
		return ret_freq;
	}

	read_unlock_irqrestore(&cpufreq_driver_lock, flags);

Thanks,
Rafael

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#1355547

From"Rafael J. Wysocki" <rafael@kernel.org>
Date2016-03-11 03:30 +0100
Message-ID<rbkZX-7ID-1@gated-at.bofh.it>
In reply to#1355425
On Thu, Mar 10, 2016 at 11:20 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Thursday, March 10, 2016 04:10:36 PM Richard Cochran wrote:
>> The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
>> its fields without taking the associated lock, cpufreq_driver_lock.
>>
>> Without the locking, nothing guarantees that 'cpufreq_driver' remains
>> consistent during the call.  This patch fixes the issue by taking the lock
>> before accessing the data structure.
>>
>> Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
>> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
>> Signed-off-by: Richard Cochran <rcochran@linutronix.de>
>
> Can you please CC PM-related patches to linux-pm@vger.kernel.org?  They
> are much easier to handle for me then.
>
>> ---
>>  drivers/cpufreq/cpufreq.c | 10 +++++++++-
>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index e979ec7..ce02b2b 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1457,9 +1457,17 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
>>  {
>>       struct cpufreq_policy *policy;
>>       unsigned int ret_freq = 0;
>> +     unsigned long flags;
>> +
>> +     read_lock_irqsave(&cpufreq_driver_lock, flags);
>>
>>       if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
>> -             return cpufreq_driver->get(cpu);
>> +             ret_freq = cpufreq_driver->get(cpu);
>> +
>> +     read_unlock_irqrestore(&cpufreq_driver_lock, flags);
>> +
>> +     if (ret_freq)
>> +             return ret_freq;
>>
>>       policy = cpufreq_cpu_get(cpu);
>>       if (policy) {
>>
>
> I would prefer something like this:
>
>         read_lock_irqsave(&cpufreq_driver_lock, flags);
>
>         if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) {
>                 unsigned int ret_freq = cpufreq_driver->get(cpu);

Sorry, ret_freq is needed outside of this block anyway, so that would be

                   ret_freq = cpufreq_driver->get(cpu);
>
>                 read_unlock_irqrestore(&cpufreq_driver_lock, flags);
>                 return ret_freq;
>         }
>
>         read_unlock_irqrestore(&cpufreq_driver_lock, flags);

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#1355707 — [PATCH v2] cpufreq: Make cpufreq_quick_get() safe to call.

FromRichard Cochran <rcochran@linutronix.de>
Date2016-03-11 09:50 +0100
Subject[PATCH v2] cpufreq: Make cpufreq_quick_get() safe to call.
Message-ID<rbqVK-3vt-37@gated-at.bofh.it>
In reply to#1355547
The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
its fields without taking the associated lock, cpufreq_driver_lock.

Without the locking, nothing guarantees that 'cpufreq_driver' remains
consistent during the call.  This patch fixes the issue by taking the lock
before accessing the data structure.

Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
---
 drivers/cpufreq/cpufreq.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e979ec7..053aa1f 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1457,9 +1457,17 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
 {
 	struct cpufreq_policy *policy;
 	unsigned int ret_freq = 0;
+	unsigned long flags;
 
-	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
-		return cpufreq_driver->get(cpu);
+	read_lock_irqsave(&cpufreq_driver_lock, flags);
+
+	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) {
+		ret_freq = cpufreq_driver->get(cpu);
+		read_unlock_irqrestore(&cpufreq_driver_lock, flags);
+		return ret_freq;
+	}
+
+	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
 	policy = cpufreq_cpu_get(cpu);
 	if (policy) {
-- 
2.1.4

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#1356293 — Re: [PATCH v2] cpufreq: Make cpufreq_quick_get() safe to call.

FromViresh Kumar <viresh.kumar@linaro.org>
Date2016-03-12 01:00 +0100
SubjectRe: [PATCH v2] cpufreq: Make cpufreq_quick_get() safe to call.
Message-ID<rbF8m-5sL-5@gated-at.bofh.it>
In reply to#1355707
On 11-03-16, 09:43, Richard Cochran wrote:
> The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
> its fields without taking the associated lock, cpufreq_driver_lock.
> 
> Without the locking, nothing guarantees that 'cpufreq_driver' remains
> consistent during the call.  This patch fixes the issue by taking the lock
> before accessing the data structure.
> 
> Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: linux-pm@vger.kernel.org
> Signed-off-by: Richard Cochran <rcochran@linutronix.de>
> ---
>  drivers/cpufreq/cpufreq.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

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