The usage_count value can be modified from several cpus concurrently if !CPUFREQ_HAVE_GOVERNOR_PER_POLICY. This leads to a variety of panics in which the usage_count is negative or exceeds the number of cpus in the system. 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_governor.c | 16 ++++++++++++---- drivers/cpufreq/cpufreq_governor.h | 3 ++- 2 files changed, 14 insertions(+), 5 deletions(-) diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index 1b44496..32ad9db 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -265,7 +265,9 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, if (have_governor_per_policy()) { WARN_ON(dbs_data); } else if (dbs_data) { - dbs_data->usage_count++; + mutex_lock(&dbs_data->usage_count_mutex); + atomic_inc(&dbs_data->usage_count); + mutex_unlock(&dbs_data->usage_count_mutex); policy->governor_data = dbs_data; return 0; } @@ -277,7 +279,10 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, } dbs_data->cdata = cdata; - dbs_data->usage_count = 1; + mutex_init(&dbs_data->usage_count_mutex); + mutex_lock(&dbs_data->usage_count_mutex); + atomic_set(&dbs_data->usage_count, 1); + mutex_unlock(&dbs_data->usage_count_mutex); rc = cdata->init(dbs_data); if (rc) { pr_err("%s: POLICY_INIT: init() failed\n", __func__); @@ -322,7 +327,8 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, return 0; case CPUFREQ_GOV_POLICY_EXIT: - if (!--dbs_data->usage_count) { + mutex_lock(&dbs_data->usage_count_mutex); + if (atomic_dec_and_test(&dbs_data->usage_count)) { sysfs_remove_group(get_governor_parent_kobj(policy), get_sysfs_attr(dbs_data)); @@ -338,9 +344,11 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, } cdata->exit(dbs_data); + mutex_unlock(&dbs_data->usage_count_mutex); kfree(dbs_data); cdata->gdbs_data = NULL; - } + } else + mutex_unlock(&dbs_data->usage_count_mutex); policy->governor_data = NULL; return 0; diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h index cc401d1..53ca449 100644 --- a/drivers/cpufreq/cpufreq_governor.h +++ b/drivers/cpufreq/cpufreq_governor.h @@ -219,7 +219,8 @@ struct common_dbs_data { struct dbs_data { struct common_dbs_data *cdata; unsigned int min_sampling_rate; - int usage_count; + struct mutex usage_count_mutex; + atomic_t usage_count; void *tuners; /* dbs_mutex protects dbs_enable in governor start/stop */ -- 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/
