On 08/07/2014 01:54 AM, Viresh Kumar wrote:

Sorry for the really long delay this time around. I am used to replying within a
day normally, and this time it just took so much time.

For next time please rebase on latest updates in pm/linux-next as there are
few updates there.

Will do.

On 25 July 2014 06:37, Saravana Kannan [off-list ref] wrote:

quoted

There's no need to wait for the CPU going down to fully go offline to
restart the governor. We can stop the governor, change policy->cpus and
immediately restart the governor. This should reduce the time without any
CPUfreq monitoring and also help future patches with simplifying the code.

I agree with the idea here, though the $subject can be improved a bit
here..

Suggestions welcome. I think the current one explains the main point of 
this change.

quoted

Signed-off-by: Saravana Kannan <redacted>
---
  drivers/cpufreq/cpufreq.c | 33 ++++++++++++++++++---------------
  1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 62259d2..ee0eb7b 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c

@@ -1390,6 +1390,21 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
                 cpufreq_driver->stop_cpu(policy);
         }

+       down_write(&policy->rwsem);
+       cpumask_clear_cpu(cpu, policy->cpus);
+       up_write(&policy->rwsem);

There is a down_read() present early in this routine and we better update this
at that place only.

I would rather not. My v1 patch series was super refactored to allow a 
lot of reuse, etc. But you guys complained about the diffs being 
confusing (which was a valid point).

Also, if we are talking about refactoring this, there's room for much 
better refactor at the end of the series. I will add a patch to the 
series to do the refactoring.

quoted

+       if (cpus > 1 && has_target()) {

We already have a if (cpus > 1) block, move this there.

That only runs if cpu != policy->cpu. This needs to run irrespective of 
that.

quoted

+               ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
+               if (!ret)
+                       ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+
+               if (ret) {
+                       pr_err("%s: Failed to start governor\n", __func__);
+                       return ret;
+               }
+       }
+
         return 0;
  }

@@ -1410,15 +1425,12 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
                 return -EINVAL;
         }

-       down_write(&policy->rwsem);
+       down_read(&policy->rwsem);
         cpus = cpumask_weight(policy->cpus);
-
-       if (cpus > 1)
-               cpumask_clear_cpu(cpu, policy->cpus);
-       up_write(&policy->rwsem);
+       up_read(&policy->rwsem);

         /* If cpu is last user of policy, free policy */
-       if (cpus == 1) {
+       if (cpus == 0) {
                 if (has_target()) {
                         ret = __cpufreq_governor(policy,
                                         CPUFREQ_GOV_POLICY_EXIT);

@@ -1447,15 +1459,6 @@ static int __cpufreq_remove_dev_finish(struct device *dev,

                 if (!cpufreq_suspended)
                         cpufreq_policy_free(policy);
-       } else if (has_target()) {
-               ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
-               if (!ret)
-                       ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
-
-               if (ret) {
-                       pr_err("%s: Failed to start governor\n", __func__);
-                       return ret;
-               }
         }

Also, you must mention in the log about an important change you are making.
Don't know if there are any side effects...

You are emptying policy->cpus on removal of last CPU of a policy, which wasn't
the case earlier.

You mean the log in the cover letter? Will do.

-Saravana

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation