OPP: Protect dev_list with opp_table lock

The dev_list needs to be protected with a lock, else we may have
simultaneous access (addition/removal) to it and that would be racy.
Extend scope of the opp_table lock to protect dev_list as well.

Tested-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 31ff03dbeb83771be1ba57fde89ea6c32f63c2aa..9f8aa31265feeb7cbf945250f159e8e8ee3009f6 100644 (file)
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -48,9 +48,14 @@ static struct opp_device *_find_opp_dev(const struct device *dev,
 static struct opp_table *_find_opp_table_unlocked(struct device *dev)
 {
        struct opp_table *opp_table;
+       bool found;
 
        list_for_each_entry(opp_table, &opp_tables, node) {
-               if (_find_opp_dev(dev, opp_table)) {
+               mutex_lock(&opp_table->lock);
+               found = !!_find_opp_dev(dev, opp_table);
+               mutex_unlock(&opp_table->lock);
+
+               if (found) {
                        _get_opp_table_kref(opp_table);
 
                        return opp_table;
@@ -766,6 +771,8 @@ struct opp_device *_add_opp_dev(const struct device *dev,
 
        /* Initialize opp-dev */
        opp_dev->dev = dev;
+
+       mutex_lock(&opp_table->lock);
        list_add(&opp_dev->node, &opp_table->dev_list);
 
        /* Create debugfs entries for the opp_table */
@@ -773,6 +780,7 @@ struct opp_device *_add_opp_dev(const struct device *dev,
        if (ret)
                dev_err(dev, "%s: Failed to register opp debugfs (%d)\n",
                        __func__, ret);
+       mutex_unlock(&opp_table->lock);
 
        return opp_dev;
 }
@@ -791,6 +799,7 @@ static struct opp_table *_allocate_opp_table(struct device *dev)
        if (!opp_table)
                return NULL;
 
+       mutex_init(&opp_table->lock);
        INIT_LIST_HEAD(&opp_table->dev_list);
 
        opp_dev = _add_opp_dev(dev, opp_table);
@@ -812,7 +821,6 @@ static struct opp_table *_allocate_opp_table(struct device *dev)
 
        BLOCKING_INIT_NOTIFIER_HEAD(&opp_table->head);
        INIT_LIST_HEAD(&opp_table->opp_list);
-       mutex_init(&opp_table->lock);
        kref_init(&opp_table->kref);
 
        /* Secure the device table modification */
@@ -854,6 +862,10 @@ static void _opp_table_kref_release(struct kref *kref)
        if (!IS_ERR(opp_table->clk))
                clk_put(opp_table->clk);
 
+       /*
+        * No need to take opp_table->lock here as we are guaranteed that no
+        * references to the OPP table are taken at this point.
+        */
        opp_dev = list_first_entry(&opp_table->dev_list, struct opp_device,
                                   node);
 
@@ -1716,6 +1728,9 @@ void _dev_pm_opp_remove_table(struct opp_table *opp_table, struct device *dev,
 {
        struct dev_pm_opp *opp, *tmp;
 
+       /* Protect dev_list */
+       mutex_lock(&opp_table->lock);
+
        /* Find if opp_table manages a single device */
        if (list_is_singular(&opp_table->dev_list)) {
                /* Free static OPPs */
@@ -1733,6 +1748,8 @@ void _dev_pm_opp_remove_table(struct opp_table *opp_table, struct device *dev,
        } else {
                _remove_opp_dev(_find_opp_dev(dev, opp_table), opp_table);
        }
+
+       mutex_unlock(&opp_table->lock);
 }
 
 void _dev_pm_opp_find_and_remove_table(struct device *dev, bool remove_all)

diff --git a/drivers/opp/cpu.c b/drivers/opp/cpu.c
index 2eb5e2e7ff667a40e96086f5d50a8a9c3f8175b9..36586f66cd837a7c9f47cf510d284d663d6b58f2 100644 (file)
--- a/drivers/opp/cpu.c
+++ b/drivers/opp/cpu.c
@@ -226,8 +226,10 @@ int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
        cpumask_clear(cpumask);
 
        if (opp_table->shared_opp == OPP_TABLE_ACCESS_SHARED) {
+               mutex_lock(&opp_table->lock);
                list_for_each_entry(opp_dev, &opp_table->dev_list, node)
                        cpumask_set_cpu(opp_dev->dev->id, cpumask);
+               mutex_unlock(&opp_table->lock);
        } else {
                cpumask_set_cpu(cpu_dev->id, cpumask);
        }

diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
index a9d22aa534c30bcf6630c54cf00716d154a089e8..88e9f47aadf19497ff3270ea580efd8b7c8ea2a3 100644 (file)
--- a/drivers/opp/opp.h
+++ b/drivers/opp/opp.h
@@ -126,7 +126,7 @@ enum opp_table_access {
  * @dev_list:  list of devices that share these OPPs
  * @opp_list:  table of opps
  * @kref:      for reference count of the table.
- * @lock:      mutex protecting the opp_list.
+ * @lock:      mutex protecting the opp_list and dev_list.
  * @np:                struct device_node pointer for opp's DT node.
  * @clock_latency_ns_max: Max clock latency in nanoseconds.
  * @shared_opp: OPP is shared between multiple devices.