PM: Do not acquire device semaphores upfront during suspend

[linux-2.6-omap-h63xx.git] / drivers / base / power / main.c

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index ee9d1c8db0d6215c407a18d4a015e3e0ebb56c53..b0c16f6fc1864654a53e6da1be60b19a7ea6a15d 100644 (file)
--- 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);
@@ -274,25 +254,6 @@ static void dpm_resume(void)
        mutex_unlock(&dpm_list_mtx);
 }
 
-/**
- *     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
  *
@@ -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) {
@@ -476,50 +436,17 @@ 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);
 
        return error;
 }
 
-/**
- *     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();