PM / OPP: Take kref from _find_opp_table()

Take reference of the OPP table from within _find_opp_table(). Also
update the callers of _find_opp_table() to call
dev_pm_opp_put_opp_table() after they have used the OPP table.

Note that _find_opp_table() increments the reference under the
opp_table_lock.

Now that the OPP table wouldn't get freed until the callers of
_find_opp_table() call dev_pm_opp_put_opp_table(), there is no need to
take the opp_table_lock or rcu_read_lock() around it. Drop them.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index a6efa81..69452a4 100644 (file)
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -54,6 +54,21 @@ static struct opp_device *_find_opp_dev(const struct device *dev,
        return NULL;
 }
 
+struct opp_table *_find_opp_table_unlocked(struct device *dev)
+{
+       struct opp_table *opp_table;
+
+       list_for_each_entry(opp_table, &opp_tables, node) {
+               if (_find_opp_dev(dev, opp_table)) {
+                       _get_opp_table_kref(opp_table);
+
+                       return opp_table;
+               }
+       }
+
+       return ERR_PTR(-ENODEV);
+}
+
 /**
  * _find_opp_table() - find opp_table struct using device pointer
  * @dev:       device pointer used to lookup OPP table
@@ -64,28 +79,22 @@ static struct opp_device *_find_opp_dev(const struct device *dev,
  * Return: pointer to 'struct opp_table' if found, otherwise -ENODEV or
  * -EINVAL based on type of error.
  *
- * Locking: For readers, this function must be called under rcu_read_lock().
- * opp_table is a RCU protected pointer, which means that opp_table is valid
- * as long as we are under RCU lock.
- *
- * For Writers, this function must be called with opp_table_lock held.
+ * The callers must call dev_pm_opp_put_opp_table() after the table is used.
  */
 struct opp_table *_find_opp_table(struct device *dev)
 {
        struct opp_table *opp_table;
 
-       opp_rcu_lockdep_assert();
-
        if (IS_ERR_OR_NULL(dev)) {
                pr_err("%s: Invalid parameters\n", __func__);
                return ERR_PTR(-EINVAL);
        }
 
-       list_for_each_entry_rcu(opp_table, &opp_tables, node)
-               if (_find_opp_dev(dev, opp_table))
-                       return opp_table;
+       mutex_lock(&opp_table_lock);
+       opp_table = _find_opp_table_unlocked(dev);
+       mutex_unlock(&opp_table_lock);
 
-       return ERR_PTR(-ENODEV);
+       return opp_table;
 }
 
 /**
@@ -175,23 +184,20 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_is_turbo);
  * @dev:       device for which we do this operation
  *
  * Return: This function returns the max clock latency in nanoseconds.
- *
- * Locking: This function takes rcu_read_lock().
  */
 unsigned long dev_pm_opp_get_max_clock_latency(struct device *dev)
 {
        struct opp_table *opp_table;
        unsigned long clock_latency_ns;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table))
-               clock_latency_ns = 0;
-       else
-               clock_latency_ns = opp_table->clock_latency_ns_max;
+               return 0;
+
+       clock_latency_ns = opp_table->clock_latency_ns_max;
+
+       dev_pm_opp_put_opp_table(opp_table);
 
-       rcu_read_unlock();
        return clock_latency_ns;
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_clock_latency);
@@ -201,15 +207,13 @@ static int _get_regulator_count(struct device *dev)
        struct opp_table *opp_table;
        int count;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (!IS_ERR(opp_table))
-               count = opp_table->regulator_count;
-       else
-               count = 0;
+       if (IS_ERR(opp_table))
+               return 0;
 
-       rcu_read_unlock();
+       count = opp_table->regulator_count;
+
+       dev_pm_opp_put_opp_table(opp_table);
 
        return count;
 }
@@ -248,13 +252,11 @@ unsigned long dev_pm_opp_get_max_volt_latency(struct device *dev)
        if (!uV)
                goto free_regulators;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (IS_ERR(opp_table)) {
-               rcu_read_unlock();
+       if (IS_ERR(opp_table))
                goto free_uV;
-       }
+
+       rcu_read_lock();
 
        memcpy(regulators, opp_table->regulators, count * sizeof(*regulators));
 
@@ -274,6 +276,7 @@ unsigned long dev_pm_opp_get_max_volt_latency(struct device *dev)
        }
 
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        /*
         * The caller needs to ensure that opp_table (and hence the regulator)
@@ -323,17 +326,15 @@ unsigned long dev_pm_opp_get_suspend_opp_freq(struct device *dev)
        struct opp_table *opp_table;
        unsigned long freq = 0;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (IS_ERR(opp_table) || !opp_table->suspend_opp ||
-           !opp_table->suspend_opp->available)
-               goto unlock;
+       if (IS_ERR(opp_table))
+               return 0;
 
-       freq = dev_pm_opp_get_freq(opp_table->suspend_opp);
+       if (opp_table->suspend_opp && opp_table->suspend_opp->available)
+               freq = dev_pm_opp_get_freq(opp_table->suspend_opp);
+
+       dev_pm_opp_put_opp_table(opp_table);
 
-unlock:
-       rcu_read_unlock();
        return freq;
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_get_suspend_opp_freq);
@@ -353,23 +354,24 @@ int dev_pm_opp_get_opp_count(struct device *dev)
        struct dev_pm_opp *temp_opp;
        int count = 0;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                count = PTR_ERR(opp_table);
                dev_err(dev, "%s: OPP table not found (%d)\n",
                        __func__, count);
-               goto out_unlock;
+               return count;
        }
 
+       rcu_read_lock();
+
        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available)
                        count++;
        }
 
-out_unlock:
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
+
        return count;
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_get_opp_count);
@@ -404,17 +406,16 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
        struct opp_table *opp_table;
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                int r = PTR_ERR(opp_table);
 
                dev_err(dev, "%s: OPP table not found (%d)\n", __func__, r);
-               rcu_read_unlock();
                return ERR_PTR(r);
        }
 
+       rcu_read_lock();
+
        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available == available &&
                                temp_opp->rate == freq) {
@@ -427,6 +428,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
        }
 
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        return opp;
 }
@@ -480,17 +482,16 @@ struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
                return ERR_PTR(-EINVAL);
        }
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (IS_ERR(opp_table)) {
-               rcu_read_unlock();
+       if (IS_ERR(opp_table))
                return ERR_CAST(opp_table);
-       }
+
+       rcu_read_lock();
 
        opp = _find_freq_ceil(opp_table, freq);
 
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        return opp;
 }
@@ -525,13 +526,11 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
                return ERR_PTR(-EINVAL);
        }
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (IS_ERR(opp_table)) {
-               rcu_read_unlock();
+       if (IS_ERR(opp_table))
                return ERR_CAST(opp_table);
-       }
+
+       rcu_read_lock();
 
        list_for_each_entry_rcu(temp_opp, &opp_table->opp_list, node) {
                if (temp_opp->available) {
@@ -547,6 +546,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
        if (!IS_ERR(opp))
                dev_pm_opp_get(opp);
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        if (!IS_ERR(opp))
                *freq = opp->rate;
@@ -564,22 +564,18 @@ static struct clk *_get_opp_clk(struct device *dev)
        struct opp_table *opp_table;
        struct clk *clk;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "%s: device opp doesn't exist\n", __func__);
-               clk = ERR_CAST(opp_table);
-               goto unlock;
+               return ERR_CAST(opp_table);
        }
 
        clk = opp_table->clk;
        if (IS_ERR(clk))
                dev_err(dev, "%s: No clock available for the device\n",
                        __func__);
+       dev_pm_opp_put_opp_table(opp_table);
 
-unlock:
-       rcu_read_unlock();
        return clk;
 }
 
@@ -715,15 +711,14 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
                return 0;
        }
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                dev_err(dev, "%s: device opp doesn't exist\n", __func__);
-               rcu_read_unlock();
                return PTR_ERR(opp_table);
        }
 
+       rcu_read_lock();
+
        old_opp = _find_freq_ceil(opp_table, &old_freq);
        if (IS_ERR(old_opp)) {
                dev_err(dev, "%s: failed to find current OPP for freq %lu (%ld)\n",
@@ -738,6 +733,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
                if (!IS_ERR(old_opp))
                        dev_pm_opp_put(old_opp);
                rcu_read_unlock();
+               dev_pm_opp_put_opp_table(opp_table);
                return ret;
        }
 
@@ -752,6 +748,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
                if (!IS_ERR(old_opp))
                        dev_pm_opp_put(old_opp);
                rcu_read_unlock();
+               dev_pm_opp_put_opp_table(opp_table);
                return _generic_set_opp_clk_only(dev, clk, old_freq, freq);
        }
 
@@ -780,6 +777,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
        if (!IS_ERR(old_opp))
                dev_pm_opp_put(old_opp);
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        return set_opp(data);
 }
@@ -893,11 +891,9 @@ struct opp_table *dev_pm_opp_get_opp_table(struct device *dev)
        /* Hold our table modification lock here */
        mutex_lock(&opp_table_lock);
 
-       opp_table = _find_opp_table(dev);
-       if (!IS_ERR(opp_table)) {
-               _get_opp_table_kref(opp_table);
+       opp_table = _find_opp_table_unlocked(dev);
+       if (!IS_ERR(opp_table))
                goto unlock;
-       }
 
        opp_table = _allocate_opp_table(dev);
 
@@ -1004,12 +1000,9 @@ void dev_pm_opp_remove(struct device *dev, unsigned long freq)
        struct opp_table *opp_table;
        bool found = false;
 
-       /* Hold our table modification lock here */
-       mutex_lock(&opp_table_lock);
-
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table))
-               goto unlock;
+               return;
 
        mutex_lock(&opp_table->lock);
 
@@ -1022,15 +1015,14 @@ void dev_pm_opp_remove(struct device *dev, unsigned long freq)
 
        mutex_unlock(&opp_table->lock);
 
-       if (!found) {
+       if (found) {
+               dev_pm_opp_put(opp);
+       } else {
                dev_warn(dev, "%s: Couldn't find OPP with freq: %lu\n",
                         __func__, freq);
-               goto unlock;
        }
 
-       dev_pm_opp_put(opp);
-unlock:
-       mutex_unlock(&opp_table_lock);
+       dev_pm_opp_put_opp_table(opp_table);
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_remove);
 
@@ -1648,14 +1640,12 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
        if (!new_opp)
                return -ENOMEM;
 
-       mutex_lock(&opp_table_lock);
-
        /* Find the opp_table */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
                r = PTR_ERR(opp_table);
                dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
-               goto unlock;
+               goto free_opp;
        }
 
        mutex_lock(&opp_table->lock);
@@ -1668,8 +1658,6 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
                }
        }
 
-       mutex_unlock(&opp_table->lock);
-
        if (IS_ERR(opp)) {
                r = PTR_ERR(opp);
                goto unlock;
@@ -1685,7 +1673,6 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
        new_opp->available = availability_req;
 
        list_replace_rcu(&opp->node, &new_opp->node);
-       mutex_unlock(&opp_table_lock);
        call_srcu(&opp_table->srcu_head.srcu, &opp->rcu_head, _kfree_opp_rcu);
 
        /* Notify the change of the OPP availability */
@@ -1696,10 +1683,14 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
                srcu_notifier_call_chain(&opp_table->srcu_head,
                                         OPP_EVENT_DISABLE, new_opp);
 
+       mutex_unlock(&opp_table->lock);
+       dev_pm_opp_put_opp_table(opp_table);
        return 0;
 
 unlock:
-       mutex_unlock(&opp_table_lock);
+       mutex_unlock(&opp_table->lock);
+       dev_pm_opp_put_opp_table(opp_table);
+free_opp:
        kfree(new_opp);
        return r;
 }
@@ -1767,18 +1758,16 @@ int dev_pm_opp_register_notifier(struct device *dev, struct notifier_block *nb)
        struct opp_table *opp_table;
        int ret;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (IS_ERR(opp_table)) {
-               ret = PTR_ERR(opp_table);
-               goto unlock;
-       }
+       if (IS_ERR(opp_table))
+               return PTR_ERR(opp_table);
+
+       rcu_read_lock();
 
        ret = srcu_notifier_chain_register(&opp_table->srcu_head, nb);
 
-unlock:
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        return ret;
 }
@@ -1797,18 +1786,14 @@ int dev_pm_opp_unregister_notifier(struct device *dev,
        struct opp_table *opp_table;
        int ret;
 
-       rcu_read_lock();
-
        opp_table = _find_opp_table(dev);
-       if (IS_ERR(opp_table)) {
-               ret = PTR_ERR(opp_table);
-               goto unlock;
-       }
+       if (IS_ERR(opp_table))
+               return PTR_ERR(opp_table);
 
        ret = srcu_notifier_chain_unregister(&opp_table->srcu_head, nb);
 
-unlock:
        rcu_read_unlock();
+       dev_pm_opp_put_opp_table(opp_table);
 
        return ret;
 }
@@ -1839,9 +1824,6 @@ void _dev_pm_opp_find_and_remove_table(struct device *dev, bool remove_all)
 {
        struct opp_table *opp_table;
 
-       /* Hold our table modification lock here */
-       mutex_lock(&opp_table_lock);
-
        /* Check for existing table for 'dev' */
        opp_table = _find_opp_table(dev);
        if (IS_ERR(opp_table)) {
@@ -1852,13 +1834,12 @@ void _dev_pm_opp_find_and_remove_table(struct device *dev, bool remove_all)
                             IS_ERR_OR_NULL(dev) ?
                                        "Invalid device" : dev_name(dev),
                             error);
-               goto unlock;
+               return;
        }
 
        _dev_pm_opp_remove_table(opp_table, dev, remove_all);
 
-unlock:
-       mutex_unlock(&opp_table_lock);
+       dev_pm_opp_put_opp_table(opp_table);
 }
 
 /**

diff --git a/drivers/base/power/opp/cpu.c b/drivers/base/power/opp/cpu.c
index adef788..df29f08 100644 (file)
--- a/drivers/base/power/opp/cpu.c
+++ b/drivers/base/power/opp/cpu.c
@@ -174,13 +174,9 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev,
        struct device *dev;
        int cpu, ret = 0;
 
-       mutex_lock(&opp_table_lock);
-
        opp_table = _find_opp_table(cpu_dev);
-       if (IS_ERR(opp_table)) {
-               ret = PTR_ERR(opp_table);
-               goto unlock;
-       }
+       if (IS_ERR(opp_table))
+               return PTR_ERR(opp_table);
 
        for_each_cpu(cpu, cpumask) {
                if (cpu == cpu_dev->id)
@@ -203,8 +199,8 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev,
                /* Mark opp-table as multiple CPUs are sharing it now */
                opp_table->shared_opp = OPP_TABLE_ACCESS_SHARED;
        }
-unlock:
-       mutex_unlock(&opp_table_lock);
+
+       dev_pm_opp_put_opp_table(opp_table);
 
        return ret;
 }
@@ -232,17 +228,13 @@ int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
        struct opp_table *opp_table;
        int ret = 0;
 
-       mutex_lock(&opp_table_lock);
-
        opp_table = _find_opp_table(cpu_dev);
-       if (IS_ERR(opp_table)) {
-               ret = PTR_ERR(opp_table);
-               goto unlock;
-       }
+       if (IS_ERR(opp_table))
+               return PTR_ERR(opp_table);
 
        if (opp_table->shared_opp == OPP_TABLE_ACCESS_UNKNOWN) {
                ret = -EINVAL;
-               goto unlock;
+               goto put_opp_table;
        }
 
        cpumask_clear(cpumask);
@@ -254,8 +246,8 @@ int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
                cpumask_set_cpu(cpu_dev->id, cpumask);
        }
 
-unlock:
-       mutex_unlock(&opp_table_lock);
+put_opp_table:
+       dev_pm_opp_put_opp_table(opp_table);
 
        return ret;
 }