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.
Cc: "Rafael J. Wysocki" <[email protected]> Cc: Viresh Kumar <[email protected]> Cc: [email protected] Signed-off-by: Prarit Bhargava <[email protected]> --- 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, -- 1.7.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
