On 07/24/2014 06:07 PM, Saravana Kannan wrote:
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.
Signed-off-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
---
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);
+
+ if (cpus > 1 && 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;
+ }
+ }
+
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;
- }
}
per_cpu(cpufreq_cpu_data, cpu) = NULL;
This patch should also fix another issue reported in-house recently.
cpufreq_update_policy() fails for an ONLINE CPU. This is the scenario
that triggers it:
Thead A
- Cluster with 4 CPUs
- CPU3 is going down.
- Governor is STOPed.
- CPU3 is removed, but governor not STARTed yet.
Thread B
- get_online_cpus()
- We cross this hotplug barrier since since POST_DEAD is sent AFTER
releasing the hotplug lock.
- cpufreq_update_policy(CPU0) does a bunch of stuff
- Then sends GOV_LIMITS to governor.
- governor is currently STOPed, so it returns an error and
cpufreq_update_policy() fails.
Thread A
- In POST_DEAD notifier, STARTs the governor again.
So, a perfectly valid call (doing get_online_cpus() and checking for
cpu_online() on a CPU before calling) fails.
-Saravana
--
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