lkml.org 
[lkml]   [2014]   [Mar]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC v3] cpufreq: Make sure frequency transitions are serialized
From
On 19 March 2014 17:45, Srivatsa S. Bhat
<srivatsa.bhat@linux.vnet.ibm.com> wrote:
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 199b52b..e90388f 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -349,6 +349,38 @@ void cpufreq_notify_post_transition(struct cpufreq_policy *policy,
> EXPORT_SYMBOL_GPL(cpufreq_notify_post_transition);
>
>
> +void cpufreq_freq_transition_begin(struct cpufreq_policy *policy,
> + struct cpufreq_freqs *freqs, unsigned int state)
> +{
> +wait:
> + wait_event(&policy->transition_wait, !policy->transition_ongoing);

I think its broken here. At this point another thread can come take lock,
update transition_ongoing, send notification and finally unlock..

And after that we can take the lock and send another notification..

Correct?

> + if (!mutex_trylock(&policy->transition_lock))
> + goto wait;
> +
> + policy->transition_ongoing++;

s/++/ = true

> + cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE);
> +
> + mutex_unlock(&policy->transition_lock);

We can release the lock before sending notifications, its there just to
protect transition_ongoing.


\
 
 \ /
  Last update: 2014-03-20 06:01    [W:0.061 / U:3.960 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site