From: Viresh Kumar <viresh.kumar@linaro.org>
To: Rafael Wysocki <rjw@rjwysocki.net>, juri.lelli@arm.com
Cc: linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
skannan@codeaurora.org, peterz@infradead.org,
mturquette@baylibre.com, steve.muckle@linaro.org,
vincent.guittot@linaro.org, morten.rasmussen@arm.com,
dietmar.eggemann@arm.com, linux-kernel@vger.kernel.org,
Viresh Kumar <viresh.kumar@linaro.org>
Subject: [PATCH V2 6/7] cpufreq: Call __cpufreq_governor() with policy->rwsem held
Date: Wed, 3 Feb 2016 19:32:22 +0530 [thread overview]
Message-ID: <c7d9903e34dc658025fb20f90c610fa7cc0c8e5d.1454507872.git.viresh.kumar@linaro.org> (raw)
In-Reply-To: <cover.1454507872.git.viresh.kumar@linaro.org>
In-Reply-To: <cover.1454507872.git.viresh.kumar@linaro.org>
This isn't followed properly by all parts of the core code, some follow
it, whereas others don't.
Enforcing it will also enable us to remove cpufreq_governor_lock, that
is used today because we can't guarantee that __cpufreq_governor() isn't
executed in parallel.
We should also ensure that the lock is held across state changes to the
governors.
For example, while adding a CPU to the policy on cpu-online path, we
need to stop the governor, change policy->cpus, start the governor and
then refresh its limits. The complete sequence must be guaranteed to
execute without any concurrent races. And that can be achieved using
policy->rwsem around these use cases.
Also note that cpufreq_driver->stop_cpu() and ->exit() can get called
while policy->rwsem is held. That shouldn't have any side effects
though.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
drivers/cpufreq/cpufreq.c | 45 ++++++++++++++++++++++++++++++---------------
1 file changed, 30 insertions(+), 15 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index dc43294e7b31..4fc3889ca7c9 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -996,30 +996,29 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
if (cpumask_test_cpu(cpu, policy->cpus))
return 0;
+ down_write(&policy->rwsem);
if (has_target()) {
ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
if (ret) {
pr_err("%s: Failed to stop governor\n", __func__);
- return ret;
+ goto unlock;
}
}
- down_write(&policy->rwsem);
cpumask_set_cpu(cpu, policy->cpus);
- up_write(&policy->rwsem);
if (has_target()) {
ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
if (!ret)
ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
- if (ret) {
+ if (ret)
pr_err("%s: Failed to start governor\n", __func__);
- return ret;
- }
}
- return 0;
+unlock:
+ up_write(&policy->rwsem);
+ return ret;
}
static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
@@ -1322,13 +1321,13 @@ static void cpufreq_offline(unsigned int cpu)
return;
}
+ down_write(&policy->rwsem);
if (has_target()) {
ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
if (ret)
pr_err("%s: Failed to stop governor\n", __func__);
}
- down_write(&policy->rwsem);
cpumask_clear_cpu(cpu, policy->cpus);
if (policy_is_inactive(policy)) {
@@ -1341,7 +1340,6 @@ static void cpufreq_offline(unsigned int cpu)
/* Nominate new CPU */
policy->cpu = cpumask_any(policy->cpus);
}
- up_write(&policy->rwsem);
/* Start governor again for active policy */
if (!policy_is_inactive(policy)) {
@@ -1376,6 +1374,7 @@ static void cpufreq_offline(unsigned int cpu)
cpufreq_driver->exit(policy);
policy->freq_table = NULL;
}
+ up_write(&policy->rwsem);
}
/**
@@ -1572,6 +1571,7 @@ EXPORT_SYMBOL(cpufreq_generic_suspend);
void cpufreq_suspend(void)
{
struct cpufreq_policy *policy;
+ int ret;
if (!cpufreq_driver)
return;
@@ -1582,7 +1582,11 @@ void cpufreq_suspend(void)
pr_debug("%s: Suspending Governors\n", __func__);
for_each_active_policy(policy) {
- if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP))
+ down_write(&policy->rwsem);
+ ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+ up_write(&policy->rwsem);
+
+ if (ret)
pr_err("%s: Failed to stop governor for policy: %p\n",
__func__, policy);
else if (cpufreq_driver->suspend
@@ -1604,6 +1608,7 @@ void cpufreq_suspend(void)
void cpufreq_resume(void)
{
struct cpufreq_policy *policy;
+ int ret;
if (!cpufreq_driver)
return;
@@ -1616,13 +1621,20 @@ void cpufreq_resume(void)
pr_debug("%s: Resuming Governors\n", __func__);
for_each_active_policy(policy) {
- if (cpufreq_driver->resume && cpufreq_driver->resume(policy))
+ if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) {
pr_err("%s: Failed to resume driver: %p\n", __func__,
policy);
- else if (__cpufreq_governor(policy, CPUFREQ_GOV_START)
- || __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))
- pr_err("%s: Failed to start governor for policy: %p\n",
- __func__, policy);
+ } else {
+ down_write(&policy->rwsem);
+ ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
+ if (!ret)
+ __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+ up_write(&policy->rwsem);
+
+ if (ret)
+ pr_err("%s: Failed to start governor for policy: %p\n",
+ __func__, policy);
+ }
}
/*
@@ -2276,8 +2288,11 @@ static int cpufreq_boost_set_sw(int state)
__func__);
break;
}
+
+ down_write(&policy->rwsem);
policy->user_policy.max = policy->max;
__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+ up_write(&policy->rwsem);
}
}
--
2.7.0.79.gdc08a19
next prev parent reply other threads:[~2016-02-03 14:02 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 14:02 [PATCH V2 0/7] cpufreq: governors: Fix ABBA lockups Viresh Kumar
2016-02-03 14:02 ` [PATCH V2 1/7] cpufreq: governor: Treat min_sampling_rate as a governor-specific tunable Viresh Kumar
2016-02-05 2:31 ` Rafael J. Wysocki
2016-02-05 2:47 ` Viresh Kumar
2016-02-03 14:02 ` [PATCH V2 2/7] cpufreq: governor: New sysfs show/store callbacks for governor tunables Viresh Kumar
2016-02-03 16:17 ` Viresh Kumar
2016-02-03 14:02 ` [PATCH V2 3/7] cpufreq: governor: Drop unused macros for creating governor tunable attributes Viresh Kumar
2016-02-03 14:02 ` [PATCH V2 4/7] Revert "cpufreq: Drop rwsem lock around CPUFREQ_GOV_POLICY_EXIT" Viresh Kumar
2016-02-03 14:02 ` [PATCH V2 5/7] cpufreq: Merge cpufreq_offline_prepare/finish routines Viresh Kumar
2016-02-03 20:21 ` Saravana Kannan
2016-02-04 1:49 ` Viresh Kumar
2016-02-03 14:02 ` Viresh Kumar [this message]
2016-02-03 14:02 ` [PATCH V2 7/7] cpufreq: Remove cpufreq_governor_lock Viresh Kumar
2016-02-04 6:43 ` Viresh Kumar
2016-02-03 15:54 ` [PATCH V2 0/7] cpufreq: governors: Fix ABBA lockups Juri Lelli
2016-02-03 16:10 ` Viresh Kumar
2016-02-03 17:20 ` Juri Lelli
2016-02-03 17:20 ` Rafael J. Wysocki
2016-02-03 23:31 ` Shilpa Bhat
2016-02-03 23:50 ` Rafael J. Wysocki
2016-02-04 5:51 ` Viresh Kumar
2016-02-04 11:09 ` Viresh Kumar
2016-02-04 17:43 ` Saravana Kannan
2016-02-04 17:44 ` Saravana Kannan
2016-02-04 18:18 ` Rafael J. Wysocki
2016-02-05 2:44 ` Viresh Kumar
2016-02-05 3:54 ` Rafael J. Wysocki
2016-02-05 9:49 ` Viresh Kumar
2016-02-08 2:20 ` Rafael J. Wysocki
2016-02-06 2:22 ` Saravana Kannan
2016-02-08 2:28 ` Rafael J. Wysocki
2016-02-09 21:02 ` Saravana Kannan
2016-02-04 6:24 ` Viresh Kumar
2016-02-04 12:17 ` Viresh Kumar
2016-02-04 20:50 ` Shilpasri G Bhat
2016-02-05 2:49 ` Viresh Kumar
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