From 1112e9d83e5cd153b35dfbb52721f8b3d3163016 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sun, 21 Feb 2016 00:53:06 +0100 Subject: [PATCH] cpufreq: governor: Narrow down the dbs_data_mutex coverage Since cpufreq_governor_dbs() is now always called with policy->rwsem held, it cannot be executed twice in parallel for the same policy. Thus it is not necessary to hold dbs_data_mutex around the invocations of cpufreq_governor_start/stop/limits() from it as those functions never modify any data that can be shared between different policies. However, cpufreq_governor_dbs() may be executed twice in parallal for different policies using the same gov->gdbs_data object and dbs_data_mutex is still necessary to protect that object against concurrent updates. For this reason, narrow down the dbs_data_mutex locking to cpufreq_governor_init/exit() where it is needed and rename the mutex to gov_dbs_data_mutex to reflect its purpose. Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar --- drivers/cpufreq/cpufreq_governor.c | 46 +++++++++++++++--------------- 1 file changed, 23 insertions(+), 23 deletions(-) diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index 4f0bd482b59e..542c9caf8815 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -24,7 +24,7 @@ static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs); -static DEFINE_MUTEX(dbs_data_mutex); +static DEFINE_MUTEX(gov_dbs_data_mutex); /* Common sysfs tunables */ /** @@ -421,10 +421,10 @@ static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs, static int cpufreq_governor_init(struct cpufreq_policy *policy) { struct dbs_governor *gov = dbs_governor_of(policy); - struct dbs_data *dbs_data = gov->gdbs_data; + struct dbs_data *dbs_data; struct policy_dbs_info *policy_dbs; unsigned int latency; - int ret; + int ret = 0; /* State should be equivalent to EXIT */ if (policy->governor_data) @@ -434,6 +434,10 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) if (!policy_dbs) return -ENOMEM; + /* Protect gov->gdbs_data against concurrent updates. */ + mutex_lock(&gov_dbs_data_mutex); + + dbs_data = gov->gdbs_data; if (dbs_data) { if (WARN_ON(have_governor_per_policy())) { ret = -EINVAL; @@ -446,8 +450,7 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) dbs_data->usage_count++; list_add(&policy_dbs->list, &dbs_data->policy_dbs_list); mutex_unlock(&dbs_data->mutex); - - return 0; + goto out; } dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL); @@ -488,7 +491,7 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) get_governor_parent_kobj(policy), "%s", gov->gov.name); if (!ret) - return 0; + goto out; /* Failure, so roll back. */ pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret); @@ -502,6 +505,9 @@ static int cpufreq_governor_init(struct cpufreq_policy *policy) free_policy_dbs_info: free_policy_dbs_info(policy_dbs, gov); + +out: + mutex_unlock(&gov_dbs_data_mutex); return ret; } @@ -512,6 +518,9 @@ static int cpufreq_governor_exit(struct cpufreq_policy *policy) struct dbs_data *dbs_data = policy_dbs->dbs_data; int count; + /* Protect gov->gdbs_data against concurrent updates. */ + mutex_lock(&gov_dbs_data_mutex); + mutex_lock(&dbs_data->mutex); list_del(&policy_dbs->list); count = --dbs_data->usage_count; @@ -533,6 +542,8 @@ static int cpufreq_governor_exit(struct cpufreq_policy *policy) } free_policy_dbs_info(policy_dbs, gov); + + mutex_unlock(&gov_dbs_data_mutex); return 0; } @@ -599,31 +610,20 @@ static int cpufreq_governor_limits(struct cpufreq_policy *policy) int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event) { - int ret = -EINVAL; - - /* Lock governor to block concurrent initialization of governor */ - mutex_lock(&dbs_data_mutex); - if (event == CPUFREQ_GOV_POLICY_INIT) { - ret = cpufreq_governor_init(policy); + return cpufreq_governor_init(policy); } else if (policy->governor_data) { switch (event) { case CPUFREQ_GOV_POLICY_EXIT: - ret = cpufreq_governor_exit(policy); - break; + return cpufreq_governor_exit(policy); case CPUFREQ_GOV_START: - ret = cpufreq_governor_start(policy); - break; + return cpufreq_governor_start(policy); case CPUFREQ_GOV_STOP: - ret = cpufreq_governor_stop(policy); - break; + return cpufreq_governor_stop(policy); case CPUFREQ_GOV_LIMITS: - ret = cpufreq_governor_limits(policy); - break; + return cpufreq_governor_limits(policy); } } - - mutex_unlock(&dbs_data_mutex); - return ret; + return -EINVAL; } EXPORT_SYMBOL_GPL(cpufreq_governor_dbs); -- 2.20.1