PM / cpuidle: Add driver reference counter

Add a reference counter for the cpuidle driver, so that it can't
be unregistered when it is in use.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 28 insertions, 1 deletions

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 40cd3f3024df..58bf3b1ac9c4 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -16,6 +16,7 @@
 
 static struct cpuidle_driver *cpuidle_curr_driver;
 DEFINE_SPINLOCK(cpuidle_driver_lock);
+int cpuidle_driver_refcount;
 
 static void __cpuidle_register_driver(struct cpuidle_driver *drv)
 {
@@ -89,8 +90,34 @@ void cpuidle_unregister_driver(struct cpuidle_driver *drv)
         }
 
         spin_lock(&cpuidle_driver_lock);
-        cpuidle_curr_driver = NULL;
+
+        if (!WARN_ON(cpuidle_driver_refcount > 0))
+                cpuidle_curr_driver = NULL;
+
         spin_unlock(&cpuidle_driver_lock);
 }
 
 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
+
+struct cpuidle_driver *cpuidle_driver_ref(void)
+{
+        struct cpuidle_driver *drv;
+
+        spin_lock(&cpuidle_driver_lock);
+
+        drv = cpuidle_curr_driver;
+        cpuidle_driver_refcount++;
+
+        spin_unlock(&cpuidle_driver_lock);
+        return drv;
+}
+
+void cpuidle_driver_unref(void)
+{
+        spin_lock(&cpuidle_driver_lock);
+
+        if (!WARN_ON(cpuidle_driver_refcount <= 0))
+                cpuidle_driver_refcount--;
+
+        spin_unlock(&cpuidle_driver_lock);
+}