From: skannan@codeaurora.org (Saravana Kannan)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor
Date: Thu, 31 Jul 2014 13:47:48 -0700 [thread overview]
Message-ID: <53DAAB74.7050003@codeaurora.org> (raw)
In-Reply-To: <1406250448-470-2-git-send-email-skannan@codeaurora.org>
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
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2014-07-31 20:47 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-10 2:37 [PATCH] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Saravana Kannan
2014-07-11 4:18 ` [PATCH v2] " Saravana Kannan
2014-07-11 6:19 ` Viresh Kumar
2014-07-11 9:59 ` skannan at codeaurora.org
2014-07-11 10:07 ` skannan at codeaurora.org
2014-07-11 10:52 ` Viresh Kumar
2014-07-12 2:44 ` Saravana Kannan
2014-07-14 6:09 ` Viresh Kumar
2014-07-14 19:08 ` Saravana Kannan
2014-07-15 4:35 ` Viresh Kumar
2014-07-15 5:36 ` Saravana Kannan
2014-07-15 5:52 ` Viresh Kumar
2014-07-15 6:58 ` Srivatsa S. Bhat
2014-07-15 17:35 ` skannan at codeaurora.org
2014-07-16 7:44 ` Srivatsa S. Bhat
2014-07-16 5:44 ` Viresh Kumar
2014-07-16 7:49 ` Srivatsa S. Bhat
2014-07-12 3:06 ` Saravana Kannan
2014-07-14 6:13 ` Viresh Kumar
2014-07-14 19:10 ` Saravana Kannan
2014-07-11 7:43 ` Srivatsa S. Bhat
2014-07-11 10:02 ` skannan at codeaurora.org
2014-07-15 22:47 ` [PATCH v3 0/2] Simplify hotplug/suspend handling Saravana Kannan
2014-07-15 22:47 ` [PATCH v3 1/2] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Saravana Kannan
2014-07-16 0:28 ` Saravana Kannan
2014-07-16 8:30 ` Viresh Kumar
2014-07-16 19:19 ` Saravana Kannan
2014-07-16 8:24 ` Viresh Kumar
2014-07-16 11:16 ` Srivatsa S. Bhat
2014-07-16 13:13 ` Viresh Kumar
2014-07-16 18:04 ` Srivatsa S. Bhat
2014-07-16 19:56 ` Saravana Kannan
2014-07-17 5:51 ` Viresh Kumar
2014-07-16 19:56 ` Saravana Kannan
2014-07-17 5:35 ` Viresh Kumar
2014-07-18 3:25 ` Saravana Kannan
2014-07-18 4:19 ` Viresh Kumar
2014-07-16 20:25 ` Saravana Kannan
2014-07-16 21:45 ` Saravana Kannan
2014-07-17 6:24 ` Viresh Kumar
2014-07-16 14:29 ` Dirk Brandewie
2014-07-16 15:28 ` Viresh Kumar
2014-07-16 19:42 ` Saravana Kannan
2014-07-15 22:47 ` [PATCH v3 2/2] cpufreq: Simplify and fix mutual exclusion with hotplug Saravana Kannan
2014-07-16 8:48 ` Viresh Kumar
2014-07-16 19:34 ` Saravana Kannan
2014-07-25 1:07 ` [PATCH v4 0/5] Simplify hotplug/suspend handling Saravana Kannan
2014-07-25 1:07 ` [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor Saravana Kannan
2014-07-31 20:47 ` Saravana Kannan [this message]
2014-07-25 1:07 ` [PATCH v4 2/5] cpufreq: Keep track of which CPU owns the kobj/sysfs nodes separately Saravana Kannan
2014-08-07 9:02 ` Viresh Kumar
2014-07-25 1:07 ` [PATCH v4 3/5] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Saravana Kannan
2014-07-31 21:56 ` Rafael J. Wysocki
2014-07-31 22:15 ` Saravana Kannan
2014-07-31 23:48 ` Saravana Kannan
2014-08-07 10:51 ` Viresh Kumar
2014-08-12 9:17 ` Viresh Kumar
2014-08-07 10:48 ` Viresh Kumar
2014-08-11 22:13 ` Saravana Kannan
2014-08-12 8:51 ` Viresh Kumar
2014-07-25 1:07 ` [PATCH v4 4/5] cpufreq: Properly handle physical CPU hot-add/hot-remove Saravana Kannan
2014-08-07 11:02 ` Viresh Kumar
2014-08-11 22:15 ` Saravana Kannan
2014-07-25 1:07 ` [PATCH v4 5/5] cpufreq: Delete dead code related to policy save/restore Saravana Kannan
2014-08-07 11:06 ` Viresh Kumar
2014-07-29 5:52 ` [PATCH v4 0/5] Simplify hotplug/suspend handling skannan at codeaurora.org
2014-07-30 0:29 ` Rafael J. Wysocki
2014-07-31 20:25 ` Saravana Kannan
2014-08-07 6:04 ` skannan at codeaurora.org
2014-10-16 8:53 ` Viresh Kumar
2014-10-23 21:41 ` Saravana Kannan
2014-07-16 22:02 ` [PATCH] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend Rafael J. Wysocki
2014-07-16 22:35 ` Saravana Kannan
2014-07-24 3:02 ` Saravana Kannan
2014-07-24 5:04 ` Viresh Kumar
2014-07-24 9:12 ` skannan at codeaurora.org
[not found] <CAKohpon=xWZJzfN0PceVntumAUFfCsbG1ibUwSxewB7bE=U7bQ@mail.gmail.com>
2014-08-11 22:11 ` [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor Saravana Kannan
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