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
Subject: Re: [PATCH V2 7/7] cpufreq: Remove cpufreq_governor_lock
Date: Thu, 4 Feb 2016 12:13:04 +0530 [thread overview]
Message-ID: <20160204064304.GA3469@vireshk> (raw)
In-Reply-To: <75f5a53c38b1efcfe7dc496525b0e96b6343a93e.1454507872.git.viresh.kumar@linaro.org>
On 03-02-16, 19:32, Viresh Kumar wrote:
> We used to drop policy->rwsem just before calling __cpufreq_governor()
> in some cases earlier and so it was possible that __cpufreq_governor()
> runs concurrently via separate threads.
>
> In order to guarantee valid state transitions for governors,
> 'governor_enabled' was required to be protected using some locking and
> we created cpufreq_governor_lock for that.
>
> But now, __cpufreq_governor() is always called from within policy->rwsem
> held and so 'governor_enabled' is protected against races even without
> cpufreq_governor_lock.
>
> Get rid of the extra lock now.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> drivers/cpufreq/cpufreq.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 4fc3889ca7c9..7bc8a5ed97e5 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -102,7 +102,6 @@ static LIST_HEAD(cpufreq_governor_list);
> static struct cpufreq_driver *cpufreq_driver;
> static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
> static DEFINE_RWLOCK(cpufreq_driver_lock);
> -DEFINE_MUTEX(cpufreq_governor_lock);
>
> /* Flag to suspend/resume CPUFreq governors */
> static bool cpufreq_suspended;
> @@ -1963,11 +1962,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
>
> pr_debug("%s: for CPU %u, event %u\n", __func__, policy->cpu, event);
>
> - mutex_lock(&cpufreq_governor_lock);
> if ((policy->governor_enabled && event == CPUFREQ_GOV_START)
> || (!policy->governor_enabled
> && (event == CPUFREQ_GOV_LIMITS || event == CPUFREQ_GOV_STOP))) {
> - mutex_unlock(&cpufreq_governor_lock);
> return -EBUSY;
> }
>
> @@ -1976,8 +1973,6 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
> else if (event == CPUFREQ_GOV_START)
> policy->governor_enabled = true;
>
> - mutex_unlock(&cpufreq_governor_lock);
> -
> ret = policy->governor->governor(policy, event);
>
> if (!ret) {
> @@ -1987,12 +1982,10 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
> policy->governor->initialized--;
> } else {
> /* Restore original values */
> - mutex_lock(&cpufreq_governor_lock);
> if (event == CPUFREQ_GOV_STOP)
> policy->governor_enabled = true;
> else if (event == CPUFREQ_GOV_START)
> policy->governor_enabled = false;
> - mutex_unlock(&cpufreq_governor_lock);
> }
>
> if (((event == CPUFREQ_GOV_POLICY_INIT) && ret) ||
+ minor cleanup:
diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
index ed328a39c4ac..7bed63e14e7d 100644
--- a/drivers/cpufreq/cpufreq_governor.h
+++ b/drivers/cpufreq/cpufreq_governor.h
@@ -214,7 +214,6 @@ static inline int delay_for_sampling_rate(unsigned int sampling_rate)
return delay;
}
-extern struct mutex cpufreq_governor_lock;
extern const struct sysfs_ops governor_sysfs_ops;
void gov_add_timers(struct cpufreq_policy *policy, unsigned int delay);
--
viresh
next prev parent reply other threads:[~2016-02-04 6:43 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 ` [PATCH V2 6/7] cpufreq: Call __cpufreq_governor() with policy->rwsem held Viresh Kumar
2016-02-03 14:02 ` [PATCH V2 7/7] cpufreq: Remove cpufreq_governor_lock Viresh Kumar
2016-02-04 6:43 ` Viresh Kumar [this message]
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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