linux-kernel - [PATCH 2/3] PM / Runtime: Don't run callbacks under lock for power.irq

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Message-Id: <201109242325.53563.rjw@sisk.pl>
Date:	Sat, 24 Sep 2011 23:25:53 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Linux-sh list" <linux-sh@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Kevin Hilman <khilman@...com>, jean.pihet@...oldbits.com,
	Ming Lei <tom.leiming@...il.com>
Subject: [PATCH 2/3] PM / Runtime: Don't run callbacks under lock for power.irq_safe set

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

The rpm_suspend() and rpm_resume() routines execute subsystem or PM
domain callbacks under power.lock if power.irq_safe is set for the
given device.  This is inconsistent with that rpm_idle() does after
commit 02b2677 (PM / Runtime: Allow _put_sync() from
interrupts-disabled context) and is problematic for subsystems and PM
domains wanting to use power.lock for synchronization in their
runtime PM callbacks.

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
 drivers/base/power/runtime.c |   68 +++++++++++++++++++++++++++++--------------
 1 file changed, 46 insertions(+), 22 deletions(-)

Index: linux/drivers/base/power/runtime.c
===================================================================
--- linux.orig/drivers/base/power/runtime.c
+++ linux/drivers/base/power/runtime.c
@@ -155,6 +155,31 @@ static int rpm_check_suspend_allowed(str
 }
 
 /**
+ * __rpm_callback - Run a given runtime PM callback for a given device.
+ * @cb: Runtime PM callback to run.
+ * @dev: Device to run the callback for.
+ */
+static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
+	__releases(&dev->power.lock) __acquires(&dev->power.lock)
+{
+	int retval;
+
+	if (dev->power.irq_safe)
+		spin_unlock(&dev->power.lock);
+	else
+		spin_unlock_irq(&dev->power.lock);
+
+	retval = cb(dev);
+
+	if (dev->power.irq_safe)
+		spin_lock(&dev->power.lock);
+	else
+		spin_lock_irq(&dev->power.lock);
+
+	return retval;
+}
+
+/**
  * rpm_idle - Notify device bus type if the device can be suspended.
  * @dev: Device to notify the bus type about.
  * @rpmflags: Flag bits.
@@ -225,19 +250,8 @@ static int rpm_idle(struct device *dev,
 	else
 		callback = NULL;
 
-	if (callback) {
-		if (dev->power.irq_safe)
-			spin_unlock(&dev->power.lock);
-		else
-			spin_unlock_irq(&dev->power.lock);
-
-		callback(dev);
-
-		if (dev->power.irq_safe)
-			spin_lock(&dev->power.lock);
-		else
-			spin_lock_irq(&dev->power.lock);
-	}
+	if (callback)
+		__rpm_callback(callback, dev);
 
 	dev->power.idle_notification = false;
 	wake_up_all(&dev->power.wait_queue);
@@ -252,22 +266,14 @@ static int rpm_idle(struct device *dev,
  * @dev: Device to run the callback for.
  */
 static int rpm_callback(int (*cb)(struct device *), struct device *dev)
-	__releases(&dev->power.lock) __acquires(&dev->power.lock)
 {
 	int retval;
 
 	if (!cb)
 		return -ENOSYS;
 
-	if (dev->power.irq_safe) {
-		retval = cb(dev);
-	} else {
-		spin_unlock_irq(&dev->power.lock);
-
-		retval = cb(dev);
+	retval = __rpm_callback(cb, dev);
 
-		spin_lock_irq(&dev->power.lock);
-	}
 	dev->power.runtime_error = retval;
 	return retval != -EACCES ? retval : -EIO;
 }
@@ -347,6 +353,15 @@ static int rpm_suspend(struct device *de
 			goto out;
 		}
 
+		if (dev->power.irq_safe) {
+			spin_unlock(&dev->power.lock);
+
+			cpu_relax();
+
+			spin_lock(&dev->power.lock);
+			goto repeat;
+		}
+
 		/* Wait for the other suspend running in parallel with us. */
 		for (;;) {
 			prepare_to_wait(&dev->power.wait_queue, &wait,
@@ -496,6 +511,15 @@ static int rpm_resume(struct device *dev
 			goto out;
 		}
 
+		if (dev->power.irq_safe) {
+			spin_unlock(&dev->power.lock);
+
+			cpu_relax();
+
+			spin_lock(&dev->power.lock);
+			goto repeat;
+		}
+
 		/* Wait for the operation carried out in parallel with us. */
 		for (;;) {
 			prepare_to_wait(&dev->power.wait_queue, &wait,

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