PM: Do not acquire device semaphores upfront during suspend

Remove the code that acquires all device semaphores from the suspend
code path as it causes multiple problems to appear (most notably,
http://bugzilla.kernel.org/show_bug.cgi?id=10030) and revert the
change introduced by commit 4145ed6dc597a9bea5f6ae8c574653b2de10620f
depending on the code being removed.

Remove pm_sleep_lock()/pm_sleep_unlock() from device_add() to avoid
the issue reported at http://bugzilla.kernel.org/show_bug.cgi?id=9874.

It should fix the regreesions reported at:
	http://bugzilla.kernel.org/show_bug.cgi?id=9874
	http://bugzilla.kernel.org/show_bug.cgi?id=10030

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 16 insertions, 98 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 9c0070b5bd3e..1e2e0fa8a450 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -770,13 +770,6 @@ int device_add(struct device *dev)
         struct class_interface *class_intf;
         int error;
 
-        error = pm_sleep_lock();
-        if (error) {
-                dev_warn(dev, "Suspicious %s during suspend\n", __FUNCTION__);
-                dump_stack();
-                return error;
-        }
-
         dev = get_device(dev);
         if (!dev || !strlen(dev->bus_id)) {
                 error = -EINVAL;
@@ -843,7 +836,6 @@ int device_add(struct device *dev)
         }
  Done:
         put_device(dev);
-        pm_sleep_unlock();
         return error;
  BusError:
         device_pm_remove(dev);
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index ee9d1c8db0d6..b0c16f6fc186 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -48,7 +48,6 @@
  */
 
 LIST_HEAD(dpm_active);
-static LIST_HEAD(dpm_locked);
 static LIST_HEAD(dpm_off);
 static LIST_HEAD(dpm_off_irq);
 static LIST_HEAD(dpm_destroy);
@@ -81,28 +80,6 @@ void device_pm_add(struct device *dev)
  */
 void device_pm_remove(struct device *dev)
 {
-        /*
-         * If this function is called during a suspend, it will be blocked,
-         * because we're holding the device's semaphore at that time, which may
-         * lead to a deadlock.  In that case we want to print a warning.
-         * However, it may also be called by unregister_dropped_devices() with
-         * the device's semaphore released, in which case the warning should
-         * not be printed.
-         */
-        if (down_trylock(&dev->sem)) {
-                if (down_read_trylock(&pm_sleep_rwsem)) {
-                        /* No suspend in progress, wait on dev->sem */
-                        down(&dev->sem);
-                        up_read(&pm_sleep_rwsem);
-                } else {
-                        /* Suspend in progress, we may deadlock */
-                        dev_warn(dev, "Suspicious %s during suspend\n",
-                                __FUNCTION__);
-                        dump_stack();
-                        /* The user has been warned ... */
-                        down(&dev->sem);
-                }
-        }
         pr_debug("PM: Removing info for %s:%s\n",
                  dev->bus ? dev->bus->name : "No Bus",
                  kobject_name(&dev->kobj));
@@ -110,7 +87,6 @@ void device_pm_remove(struct device *dev)
         dpm_sysfs_remove(dev);
         list_del_init(&dev->power.entry);
         mutex_unlock(&dpm_list_mtx);
-        up(&dev->sem);
 }
 
 /**
@@ -230,6 +206,8 @@ static int resume_device(struct device *dev)
         TRACE_DEVICE(dev);
         TRACE_RESUME(0);
 
+        down(&dev->sem);
+
         if (dev->bus && dev->bus->resume) {
                 dev_dbg(dev,"resuming\n");
                 error = dev->bus->resume(dev);
@@ -245,6 +223,8 @@ static int resume_device(struct device *dev)
                 error = dev->class->resume(dev);
         }
 
+        up(&dev->sem);
+
         TRACE_RESUME(error);
         return error;
 }
@@ -266,7 +246,7 @@ static void dpm_resume(void)
                 struct list_head *entry = dpm_off.next;
                 struct device *dev = to_device(entry);
 
-                list_move_tail(entry, &dpm_locked);
+                list_move_tail(entry, &dpm_active);
                 mutex_unlock(&dpm_list_mtx);
                 resume_device(dev);
                 mutex_lock(&dpm_list_mtx);
@@ -275,25 +255,6 @@ static void dpm_resume(void)
 }
 
 /**
- *      unlock_all_devices - Release each device's semaphore
- *
- *      Go through the dpm_off list.  Put each device on the dpm_active
- *      list and unlock it.
- */
-static void unlock_all_devices(void)
-{
-        mutex_lock(&dpm_list_mtx);
-        while (!list_empty(&dpm_locked)) {
-                struct list_head *entry = dpm_locked.prev;
-                struct device *dev = to_device(entry);
-
-                list_move(entry, &dpm_active);
-                up(&dev->sem);
-        }
-        mutex_unlock(&dpm_list_mtx);
-}
-
-/**
  *      unregister_dropped_devices - Unregister devices scheduled for removal
  *
  *      Unregister all devices on the dpm_destroy list.
@@ -305,7 +266,6 @@ static void unregister_dropped_devices(void)
                 struct list_head *entry = dpm_destroy.next;
                 struct device *dev = to_device(entry);
 
-                up(&dev->sem);
                 mutex_unlock(&dpm_list_mtx);
                 /* This also removes the device from the list */
                 device_unregister(dev);
@@ -324,7 +284,6 @@ void device_resume(void)
 {
         might_sleep();
         dpm_resume();
-        unlock_all_devices();
         unregister_dropped_devices();
         up_write(&pm_sleep_rwsem);
 }
@@ -388,18 +347,15 @@ int device_power_down(pm_message_t state)
                 struct list_head *entry = dpm_off.prev;
                 struct device *dev = to_device(entry);
 
-                list_del_init(&dev->power.entry);
                 error = suspend_device_late(dev, state);
                 if (error) {
                         printk(KERN_ERR "Could not power down device %s: "
                                         "error %d\n",
                                         kobject_name(&dev->kobj), error);
-                        if (list_empty(&dev->power.entry))
-                                list_add(&dev->power.entry, &dpm_off);
                         break;
                 }
-                if (list_empty(&dev->power.entry))
-                        list_add(&dev->power.entry, &dpm_off_irq);
+                if (!list_empty(&dev->power.entry))
+                        list_move(&dev->power.entry, &dpm_off_irq);
         }
 
         if (!error)
@@ -419,6 +375,8 @@ static int suspend_device(struct device *dev, pm_message_t state)
 {
         int error = 0;
 
+        down(&dev->sem);
+
         if (dev->power.power_state.event) {
                 dev_dbg(dev, "PM: suspend %d-->%d\n",
                         dev->power.power_state.event, state.event);
@@ -441,6 +399,9 @@ static int suspend_device(struct device *dev, pm_message_t state)
                 error = dev->bus->suspend(dev, state);
                 suspend_report_result(dev->bus->suspend, error);
         }
+
+        up(&dev->sem);
+
         return error;
 }
 
@@ -461,11 +422,10 @@ static int dpm_suspend(pm_message_t state)
         int error = 0;
 
         mutex_lock(&dpm_list_mtx);
-        while (!list_empty(&dpm_locked)) {
-                struct list_head *entry = dpm_locked.prev;
+        while (!list_empty(&dpm_active)) {
+                struct list_head *entry = dpm_active.prev;
                 struct device *dev = to_device(entry);
 
-                list_del_init(&dev->power.entry);
                 mutex_unlock(&dpm_list_mtx);
                 error = suspend_device(dev, state);
                 if (error) {
@@ -476,14 +436,11 @@ static int dpm_suspend(pm_message_t state)
                                         (error == -EAGAIN ?
                                         " (please convert to suspend_late)" :
                                         ""));
-                        mutex_lock(&dpm_list_mtx);
-                        if (list_empty(&dev->power.entry))
-                                list_add(&dev->power.entry, &dpm_locked);
                         break;
                 }
                 mutex_lock(&dpm_list_mtx);
-                if (list_empty(&dev->power.entry))
-                        list_add(&dev->power.entry, &dpm_off);
+                if (!list_empty(&dev->power.entry))
+                        list_move(&dev->power.entry, &dpm_off);
         }
         mutex_unlock(&dpm_list_mtx);
 
@@ -491,36 +448,6 @@ static int dpm_suspend(pm_message_t state)
 }
 
 /**
- *      lock_all_devices - Acquire every device's semaphore
- *
- *      Go through the dpm_active list. Carefully lock each device's
- *      semaphore and put it in on the dpm_locked list.
- */
-static void lock_all_devices(void)
-{
-        mutex_lock(&dpm_list_mtx);
-        while (!list_empty(&dpm_active)) {
-                struct list_head *entry = dpm_active.next;
-                struct device *dev = to_device(entry);
-
-                /* Required locking order is dev->sem first,
-                 * then dpm_list_mutex.  Hence this awkward code.
-                 */
-                get_device(dev);
-                mutex_unlock(&dpm_list_mtx);
-                down(&dev->sem);
-                mutex_lock(&dpm_list_mtx);
-
-                if (list_empty(entry))
-                        up(&dev->sem);          /* Device was removed */
-                else
-                        list_move_tail(entry, &dpm_locked);
-                put_device(dev);
-        }
-        mutex_unlock(&dpm_list_mtx);
-}
-
-/**
  *      device_suspend - Save state and stop all devices in system.
  *      @state: new power management state
  *
@@ -533,7 +460,6 @@ int device_suspend(pm_message_t state)
 
         might_sleep();
         down_write(&pm_sleep_rwsem);
-        lock_all_devices();
         error = dpm_suspend(state);
         if (error)
                 device_resume();