linux-kernel - [RFC][PATCH 1/2] PM / cpuidle: Add driver reference counter

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Message-Id: <201205092341.56059.rjw@sisk.pl>
Date:	Wed, 9 May 2012 23:41:55 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linux PM list <linux-pm@...r.kernel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>,
	Colin Cross <ccross@...roid.com>,
	Kevin Hilman <khilman@...com>,
	Magnus Damm <magnus.damm@...il.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>
Subject: [RFC][PATCH 1/2] PM / cpuidle: Add driver reference counter

From: Rafael J. Wysocki <rjw@...k.pl>

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@...k.pl>
---
 drivers/cpuidle/driver.c |   29 ++++++++++++++++++++++++++++-
 include/linux/cpuidle.h  |    6 +++++-
 2 files changed, 33 insertions(+), 2 deletions(-)

Index: linux/drivers/cpuidle/driver.c
===================================================================
--- linux.orig/drivers/cpuidle/driver.c
+++ linux/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 cp
 	}
 
 	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);
+}
Index: linux/include/linux/cpuidle.h
===================================================================
--- linux.orig/include/linux/cpuidle.h
+++ linux/include/linux/cpuidle.h
@@ -136,7 +136,9 @@ struct cpuidle_driver {
 extern void disable_cpuidle(void);
 extern int cpuidle_idle_call(void);
 extern int cpuidle_register_driver(struct cpuidle_driver *drv);
-struct cpuidle_driver *cpuidle_get_driver(void);
+extern struct cpuidle_driver *cpuidle_get_driver(void);
+extern struct cpuidle_driver *cpuidle_driver_ref(void);
+extern void cpuidle_driver_unref(void);
 extern void cpuidle_unregister_driver(struct cpuidle_driver *drv);
 extern int cpuidle_register_device(struct cpuidle_device *dev);
 extern void cpuidle_unregister_device(struct cpuidle_device *dev);
@@ -157,6 +159,8 @@ static inline int cpuidle_idle_call(void
 static inline int cpuidle_register_driver(struct cpuidle_driver *drv)
 {return -ENODEV; }
 static inline struct cpuidle_driver *cpuidle_get_driver(void) {return NULL; }
+static inline struct cpuidle_driver *cpuidle_driver_ref(void) {return NULL; }
+static inline void cpuidle_driver_unref(void) {}
 static inline void cpuidle_unregister_driver(struct cpuidle_driver *drv) { }
 static inline int cpuidle_register_device(struct cpuidle_device *dev)
 {return -ENODEV; }

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