Re: [PATCH] cpufreq: Fix serialization of frequency transitions

On Tuesday, July 02, 2013 04:36:28 PM Viresh Kumar wrote:

Commit 7c30ed ("cpufreq: make sure frequency transitions are serialized") interacts poorly with systems that have a single core freqency for all cores. On such systems we have a single policy for all cores with several CPUs. When we do a frequency transition the governor calls the pre and post change notifiers which causes cpufreq_notify_transition() per CPU. Since the policy is the same for all of them all CPUs after the first and the warnings added are generated by checking a per-policy flag the warnings will be triggered for all cores after the first.

Fix this by allowing notifier to be called for n times. Where n is the number of cpus in policy->cpus.

Reported-and-Tested-by: Mark Brown broonie@linaro.org Signed-off-by: Viresh Kumar viresh.kumar@linaro.org

---

Hi Rafael,

This is a fix for 3.11.

Queued up for 3.11.

Thanks, Rafael

drivers/cpufreq/cpufreq.c | 7 ++++--- include/linux/cpufreq.h | 2 +- 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index b557503..b7bda8d 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -312,11 +312,12 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy, switch (state) { case CPUFREQ_PRECHANGE:

• if (WARN(policy->transition_ongoing,
  

• if (WARN(policy->transition_ongoing ==
  

• 			cpumask_weight(policy->cpus),
  	"In middle of another frequency transition\n"))
  return;
  

• policy->transition_ongoing = true;
  

• policy->transition_ongoing++;
  

/* detect if the driver reported a value as "old frequency" * which is not equal to what the cpufreq core thinks is @@ -341,7 +342,7 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy, "No frequency transition in progress\n")) return;

• policy->transition_ongoing = false;
  

• policy->transition_ongoing--;
  

adjust_jiffies(CPUFREQ_POSTCHANGE, freqs); pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new, diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 4d7390b..90d5a15 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -119,7 +119,7 @@ struct cpufreq_policy { struct kobject kobj; struct completion kobj_unregister;

• bool transition_ongoing; /* Tracks transition status */

• int transition_ongoing; /* Tracks transition status */

}; #define CPUFREQ_ADJUST (0)