On Wednesday, November 05, 2014 09:53:58 AM Prarit Bhargava wrote:
> The policy->initialized value can be modified from several cpus concurrently
> if
> !CPUFREQ_HAVE_GOVERNOR_PER_POLICY. This leads to a situation where a
> governor maybe switched out even though the governor->initialized is greater
> than one. It must be switched to atomic_t and protected with a mutex to
> make sure that future read/writes obtain the correct data.
Same comments as for [3/5]. If you add a new mutex, you can avoid using
atomic_t.
> Cc: "Rafael J. Wysocki" <r...@rjwysocki.net>
> Cc: Viresh Kumar <viresh.ku...@linaro.org>
> Cc: linux...@vger.kernel.org
> Signed-off-by: Prarit Bhargava <pra...@redhat.com>
> ---
> drivers/cpufreq/cpufreq.c | 12 +++++++++---
> drivers/cpufreq/cpufreq_governor.c | 4 ++--
> include/linux/cpufreq.h | 3 ++-
> 3 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index e33cb15..cf11de6 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2059,10 +2059,12 @@ static int __cpufreq_governor(struct cpufreq_policy
> *policy,
> ret = policy->governor->governor(policy, event);
>
> if (!ret) {
> + mutex_lock(&policy->governor->initialized_mutex);
> if (event == CPUFREQ_GOV_POLICY_INIT)
> - policy->governor->initialized++;
> + atomic_inc(&policy->governor->initialized);
> else if (event == CPUFREQ_GOV_POLICY_EXIT)
> - policy->governor->initialized--;
> + atomic_dec(&policy->governor->initialized);
> + mutex_unlock(&policy->governor->initialized_mutex);
> } else {
> /* Restore original values */
> mutex_lock(&cpufreq_governor_lock);
> @@ -2092,7 +2094,11 @@ int cpufreq_register_governor(struct cpufreq_governor
> *governor)
>
> mutex_lock(&cpufreq_governor_mutex);
>
> - governor->initialized = 0;
> + mutex_init(&governor->initialized_mutex);
> + mutex_lock(&governor->initialized_mutex);
> + atomic_set(&governor->initialized, 0);
> + mutex_unlock(&governor->initialized_mutex);
> +
> err = -EBUSY;
> if (__find_governor(governor->name) == NULL) {
> err = 0;
> diff --git a/drivers/cpufreq/cpufreq_governor.c
> b/drivers/cpufreq/cpufreq_governor.c
> index 32ad9db..b1ee597 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -315,7 +315,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
> latency * LATENCY_MULTIPLIER));
>
> if ((cdata->governor == GOV_CONSERVATIVE) &&
> - (!policy->governor->initialized)) {
> + (!atomic_read(&policy->governor->initialized))) {
> struct cs_ops *cs_ops = dbs_data->cdata->gov_ops;
>
> cpufreq_register_notifier(cs_ops->notifier_block,
> @@ -336,7 +336,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
> cpufreq_put_global_kobject();
>
> if ((dbs_data->cdata->governor == GOV_CONSERVATIVE) &&
> - (policy->governor->initialized == 1)) {
> + atomic_read(&policy->governor->initialized) == 1) {
> struct cs_ops *cs_ops =
> dbs_data->cdata->gov_ops;
>
>
> cpufreq_unregister_notifier(cs_ops->notifier_block,
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 43909ad..73cec45 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -431,7 +431,8 @@ static inline unsigned long cpufreq_scale(unsigned long
> old, u_int div,
>
> struct cpufreq_governor {
> char name[CPUFREQ_NAME_LEN];
> - int initialized;
> + struct mutex initialized_mutex;
> + atomic_t initialized;
> int (*governor) (struct cpufreq_policy *policy,
> unsigned int event);
> ssize_t (*show_setspeed) (struct cpufreq_policy *policy,
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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