drivers: power: Add watchdog timer to catch drivers which lockup during suspend.

	Rather than hard-lock the kernel, we now BUG() when a driver takes
> 3 seconds to suspend. If the underlying platform supports panic dumps,
then the data can be collected for debug.

Signed-off-by: San Mehat <san@google.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 8aa2443182d5..55b9e6bd4f1b 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -25,6 +25,7 @@
 #include <linux/resume-trace.h>
 #include <linux/rwsem.h>
 #include <linux/interrupt.h>
+#include <linux/timer.h>
 
 #include "../base.h"
 #include "power.h"
@@ -43,6 +44,9 @@ LIST_HEAD(dpm_list);
 
 static DEFINE_MUTEX(dpm_list_mtx);
 
+static void dpm_drv_timeout(unsigned long data);
+static DEFINE_TIMER(dpm_drv_wd, dpm_drv_timeout, 0, 0);
+
 /*
  * Set once the preparation of devices for a PM transition has started, reset
  * before starting to resume devices.  Protected by dpm_list_mtx.
@@ -432,6 +436,45 @@ static int device_resume(struct device *dev, pm_message_t state)
 }
 
 /**
+ *	dpm_drv_timeout - Driver suspend / resume watchdog handler
+ *	@data: struct device which timed out
+ *
+ * 	Called when a driver has timed out suspending or resuming.
+ * 	There's not much we can do here to recover so
+ * 	BUG() out for a crash-dump
+ *
+ */
+static void dpm_drv_timeout(unsigned long data)
+{
+	struct device *dev = (struct device *) data;
+
+	printk(KERN_EMERG "**** DPM device timeout: %s (%s)\n", dev_name(dev),
+	       (dev->driver ? dev->driver->name : "no driver"));
+	BUG();
+}
+
+/**
+ *	dpm_drv_wdset - Sets up driver suspend/resume watchdog timer.
+ *	@dev: struct device which we're guarding.
+ *
+ */
+static void dpm_drv_wdset(struct device *dev)
+{
+	dpm_drv_wd.data = (unsigned long) dev;
+	mod_timer(&dpm_drv_wd, jiffies + (HZ * 3));
+}
+
+/**
+ *	dpm_drv_wdclr - clears driver suspend/resume watchdog timer.
+ *	@dev: struct device which we're no longer guarding.
+ *
+ */
+static void dpm_drv_wdclr(struct device *dev)
+{
+	del_timer_sync(&dpm_drv_wd);
+}
+
+/**
  * dpm_resume - Execute "resume" callbacks for non-sysdev devices.
  * @state: PM transition of the system being carried out.
  *
@@ -689,7 +732,9 @@ static int dpm_suspend(pm_message_t state)
 		get_device(dev);
 		mutex_unlock(&dpm_list_mtx);
 
+		dpm_drv_wdset(dev);
 		error = device_suspend(dev, state);
+		dpm_drv_wdclr(dev);
 
 		mutex_lock(&dpm_list_mtx);
 		if (error) {