| Message ID | 1406250448-470-2-git-send-email-skannan@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@codeaurora.org> > --- > 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
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;
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@codeaurora.org> --- drivers/cpufreq/cpufreq.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-)