linux-kernel - [PATCH v2] PM: runtime: add might

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Date:	Mon, 25 Jul 2011 13:55:44 -0700
From:	Colin Cross <ccross@...roid.com>
To:	linux-pm@...ts.linux-foundation.org
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	Kevin Hilman <khilman@...com>, Nishanth Menon <nm@...com>,
	Alan Stern <stern@...land.harvard.edu>,
	Colin Cross <ccross@...roid.com>
Subject: [PATCH v2] PM: runtime: add might_sleep to PM runtime functions

Some of the entry points to pm runtime are not safe to
call in atomic context unless pm_runtime_irq_safe() has
been called.  Inspecting the code, it is not immediately
obvious that the functions sleep at all, as they run
inside a spin_lock_irqsave, but under some conditions
they can drop the lock and turn on irqs.

If a driver incorrectly calls the pm_runtime apis, it can
cause sleeping and irq processing when it expects to stay
in atomic context.

Add might_sleep_if to all the __pm_runtime_* entry points
to enforce correct usage.

Add pm_runtime_put_sync_autosuspend to the list of
functions that can be called in atomic context.

Signed-off-by: Colin Cross <ccross@...roid.com>
---
 Documentation/power/runtime_pm.txt |    1 +
 drivers/base/power/runtime.c       |   15 ++++++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index c291233..1ad507c 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -469,6 +469,7 @@ pm_runtime_resume()
 pm_runtime_get_sync()
 pm_runtime_put_sync()
 pm_runtime_put_sync_suspend()
+pm_runtime_put_sync_autosuspend()
 
 5. Run-time PM Initialization, Device Probing and Removal
 
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 2e746f8..f3d8583 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -731,13 +731,16 @@ EXPORT_SYMBOL_GPL(pm_schedule_suspend);
  * return immediately if it is larger than zero.  Then carry out an idle
  * notification, either synchronous or asynchronous.
  *
- * This routine may be called in atomic context if the RPM_ASYNC flag is set.
+ * This routine may be called in atomic context if the RPM_ASYNC flag is set,
+ * or if pm_runtime_irq_safe() has been called.
  */
 int __pm_runtime_idle(struct device *dev, int rpmflags)
 {
 	unsigned long flags;
 	int retval;
 
+	might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);
+
 	if (rpmflags & RPM_GET_PUT) {
 		if (!atomic_dec_and_test(&dev->power.usage_count))
 			return 0;
@@ -760,13 +763,16 @@ EXPORT_SYMBOL_GPL(__pm_runtime_idle);
  * return immediately if it is larger than zero.  Then carry out a suspend,
  * either synchronous or asynchronous.
  *
- * This routine may be called in atomic context if the RPM_ASYNC flag is set.
+ * This routine may be called in atomic context if the RPM_ASYNC flag is set,
+ * or if pm_runtime_irq_safe() has been called.
  */
 int __pm_runtime_suspend(struct device *dev, int rpmflags)
 {
 	unsigned long flags;
 	int retval;
 
+	might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);
+
 	if (rpmflags & RPM_GET_PUT) {
 		if (!atomic_dec_and_test(&dev->power.usage_count))
 			return 0;
@@ -788,13 +794,16 @@ EXPORT_SYMBOL_GPL(__pm_runtime_suspend);
  * If the RPM_GET_PUT flag is set, increment the device's usage count.  Then
  * carry out a resume, either synchronous or asynchronous.
  *
- * This routine may be called in atomic context if the RPM_ASYNC flag is set.
+ * This routine may be called in atomic context if the RPM_ASYNC flag is set,
+ * or if pm_runtime_irq_safe() has been called.
  */
 int __pm_runtime_resume(struct device *dev, int rpmflags)
 {
 	unsigned long flags;
 	int retval;
 
+	might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);
+
 	if (rpmflags & RPM_GET_PUT)
 		atomic_inc(&dev->power.usage_count);
 
-- 
1.7.4.1

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