2 files changed, 342 insertions, 172 deletions

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 691ffb64cc37..200ed5fafd50 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -24,20 +24,45 @@
 #include <linux/mutex.h>
 #include <linux/pm.h>
 #include <linux/resume-trace.h>
+#include <linux/rwsem.h>
 
 #include "../base.h"
 #include "power.h"
 
+/*
+ * The entries in the dpm_active list are in a depth first order, simply
+ * because children are guaranteed to be discovered after parents, and
+ * are inserted at the back of the list on discovery.
+ *
+ * All the other lists are kept in the same order, for consistency.
+ * However the lists aren't always traversed in the same order.
+ * Semaphores must be acquired from the top (i.e., front) down
+ * and released in the opposite order.  Devices must be suspended
+ * from the bottom (i.e., end) up and resumed in the opposite order.
+ * That way no parent will be suspended while it still has an active
+ * child.
+ *
+ * Since device_pm_add() may be called with a device semaphore held,
+ * we must never try to acquire a device semaphore while holding
+ * dpm_list_mutex.
+ */
+
 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);
 
-static DEFINE_MUTEX(dpm_mtx);
 static DEFINE_MUTEX(dpm_list_mtx);
 
-int (*platform_enable_wakeup)(struct device *dev, int is_on);
+static DECLARE_RWSEM(pm_sleep_rwsem);
 
+int (*platform_enable_wakeup)(struct device *dev, int is_on);
 
+/**
+ *      device_pm_add - add a device to the list of active devices
+ *      @dev:   Device to be added to the list
+ */
 void device_pm_add(struct device *dev)
 {
         pr_debug("PM: Adding info for %s:%s\n",
@@ -48,8 +73,36 @@ void device_pm_add(struct device *dev)
         mutex_unlock(&dpm_list_mtx);
 }
 
+/**
+ *      device_pm_remove - remove a device from the list of active devices
+ *      @dev:   Device to be removed from the list
+ *
+ *      This function also removes the device's PM-related sysfs attributes.
+ */
 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));
@@ -57,25 +110,124 @@ 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);
+}
+
+/**
+ *      device_pm_schedule_removal - schedule the removal of a suspended device
+ *      @dev:   Device to destroy
+ *
+ *      Moves the device to the dpm_destroy list for further processing by
+ *      unregister_dropped_devices().
+ */
+void device_pm_schedule_removal(struct device *dev)
+{
+        pr_debug("PM: Preparing for removal: %s:%s\n",
+                dev->bus ? dev->bus->name : "No Bus",
+                kobject_name(&dev->kobj));
+        mutex_lock(&dpm_list_mtx);
+        list_move_tail(&dev->power.entry, &dpm_destroy);
+        mutex_unlock(&dpm_list_mtx);
+}
+
+/**
+ *      pm_sleep_lock - mutual exclusion for registration and suspend
+ *
+ *      Returns 0 if no suspend is underway and device registration
+ *      may proceed, otherwise -EBUSY.
+ */
+int pm_sleep_lock(void)
+{
+        if (down_read_trylock(&pm_sleep_rwsem))
+                return 0;
+
+        return -EBUSY;
+}
+
+/**
+ *      pm_sleep_unlock - mutual exclusion for registration and suspend
+ *
+ *      This routine undoes the effect of device_pm_add_lock
+ *      when a device's registration is complete.
+ */
+void pm_sleep_unlock(void)
+{
+        up_read(&pm_sleep_rwsem);
 }
 
 
 /*------------------------- Resume routines -------------------------*/
 
 /**
- *      resume_device - Restore state for one device.
+ *      resume_device_early - Power on one device (early resume).
  *      @dev:   Device.
  *
+ *      Must be called with interrupts disabled.
  */
-
-static int resume_device(struct device * dev)
+static int resume_device_early(struct device *dev)
 {
         int error = 0;
 
         TRACE_DEVICE(dev);
         TRACE_RESUME(0);
 
-        down(&dev->sem);
+        if (dev->bus && dev->bus->resume_early) {
+                dev_dbg(dev, "EARLY resume\n");
+                error = dev->bus->resume_early(dev);
+        }
+
+        TRACE_RESUME(error);
+        return error;
+}
+
+/**
+ *      dpm_power_up - Power on all regular (non-sysdev) devices.
+ *
+ *      Walk the dpm_off_irq list and power each device up. This
+ *      is used for devices that required they be powered down with
+ *      interrupts disabled. As devices are powered on, they are moved
+ *      to the dpm_off list.
+ *
+ *      Must be called with interrupts disabled and only one CPU running.
+ */
+static void dpm_power_up(void)
+{
+
+        while (!list_empty(&dpm_off_irq)) {
+                struct list_head *entry = dpm_off_irq.next;
+                struct device *dev = to_device(entry);
+
+                list_move_tail(entry, &dpm_off);
+                resume_device_early(dev);
+        }
+}
+
+/**
+ *      device_power_up - Turn on all devices that need special attention.
+ *
+ *      Power on system devices, then devices that required we shut them down
+ *      with interrupts disabled.
+ *
+ *      Must be called with interrupts disabled.
+ */
+void device_power_up(void)
+{
+        sysdev_resume();
+        dpm_power_up();
+}
+EXPORT_SYMBOL_GPL(device_power_up);
+
+/**
+ *      resume_device - Restore state for one device.
+ *      @dev:   Device.
+ *
+ */
+static int resume_device(struct device *dev)
+{
+        int error = 0;
+
+        TRACE_DEVICE(dev);
+        TRACE_RESUME(0);
 
         if (dev->bus && dev->bus->resume) {
                 dev_dbg(dev,"resuming\n");
@@ -92,126 +244,94 @@ static int resume_device(struct device * dev)
                 error = dev->class->resume(dev);
         }
 
-        up(&dev->sem);
-
         TRACE_RESUME(error);
         return error;
 }
 
-
-static int resume_device_early(struct device * dev)
-{
-        int error = 0;
-
-        TRACE_DEVICE(dev);
-        TRACE_RESUME(0);
-        if (dev->bus && dev->bus->resume_early) {
-                dev_dbg(dev,"EARLY resume\n");
-                error = dev->bus->resume_early(dev);
-        }
-        TRACE_RESUME(error);
-        return error;
-}
-
-/*
- * Resume the devices that have either not gone through
- * the late suspend, or that did go through it but also
- * went through the early resume
+/**
+ *      dpm_resume - Resume every device.
+ *
+ *      Resume the devices that have either not gone through
+ *      the late suspend, or that did go through it but also
+ *      went through the early resume.
+ *
+ *      Take devices from the dpm_off_list, resume them,
+ *      and put them on the dpm_locked list.
  */
 static void dpm_resume(void)
 {
         mutex_lock(&dpm_list_mtx);
         while(!list_empty(&dpm_off)) {
-                struct list_head * entry = dpm_off.next;
-                struct device * dev = to_device(entry);
-
-                get_device(dev);
-                list_move_tail(entry, &dpm_active);
+                struct list_head *entry = dpm_off.next;
+                struct device *dev = to_device(entry);
 
+                list_move_tail(entry, &dpm_locked);
                 mutex_unlock(&dpm_list_mtx);
                 resume_device(dev);
                 mutex_lock(&dpm_list_mtx);
-                put_device(dev);
         }
         mutex_unlock(&dpm_list_mtx);
 }
 
-
 /**
- *      device_resume - Restore state of each device in system.
+ *      unlock_all_devices - Release each device's semaphore
  *
- *      Walk the dpm_off list, remove each entry, resume the device,
- *      then add it to the dpm_active list.
+ *      Go through the dpm_off list.  Put each device on the dpm_active
+ *      list and unlock it.
  */
-
-void device_resume(void)
+static void unlock_all_devices(void)
 {
-        might_sleep();
-        mutex_lock(&dpm_mtx);
-        dpm_resume();
-        mutex_unlock(&dpm_mtx);
-}
-
-EXPORT_SYMBOL_GPL(device_resume);
+        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);
+}
 
 /**
- *      dpm_power_up - Power on some devices.
- *
- *      Walk the dpm_off_irq list and power each device up. This
- *      is used for devices that required they be powered down with
- *      interrupts disabled. As devices are powered on, they are moved
- *      to the dpm_active list.
+ *      unregister_dropped_devices - Unregister devices scheduled for removal
  *
- *      Interrupts must be disabled when calling this.
+ *      Unregister all devices on the dpm_destroy list.
  */
-
-static void dpm_power_up(void)
+static void unregister_dropped_devices(void)
 {
-        while(!list_empty(&dpm_off_irq)) {
-                struct list_head * entry = dpm_off_irq.next;
-                struct device * dev = to_device(entry);
+        mutex_lock(&dpm_list_mtx);
+        while (!list_empty(&dpm_destroy)) {
+                struct list_head *entry = dpm_destroy.next;
+                struct device *dev = to_device(entry);
 
-                list_move_tail(entry, &dpm_off);
-                resume_device_early(dev);
+                up(&dev->sem);
+                mutex_unlock(&dpm_list_mtx);
+                /* This also removes the device from the list */
+                device_unregister(dev);
+                mutex_lock(&dpm_list_mtx);
         }
+        mutex_unlock(&dpm_list_mtx);
 }
 
-
 /**
- *      device_power_up - Turn on all devices that need special attention.
+ *      device_resume - Restore state of each device in system.
  *
- *      Power on system devices then devices that required we shut them down
- *      with interrupts disabled.
- *      Called with interrupts disabled.
+ *      Resume all the devices, unlock them all, and allow new
+ *      devices to be registered once again.
  */
-
-void device_power_up(void)
+void device_resume(void)
 {
-        sysdev_resume();
-        dpm_power_up();
+        might_sleep();
+        dpm_resume();
+        unlock_all_devices();
+        unregister_dropped_devices();
+        up_write(&pm_sleep_rwsem);
 }
-
-EXPORT_SYMBOL_GPL(device_power_up);
+EXPORT_SYMBOL_GPL(device_resume);
 
 
 /*------------------------- Suspend routines -------------------------*/
 
-/*
- * The entries in the dpm_active list are in a depth first order, simply
- * because children are guaranteed to be discovered after parents, and
- * are inserted at the back of the list on discovery.
- *
- * All list on the suspend path are done in reverse order, so we operate
- * on the leaves of the device tree (or forests, depending on how you want
- * to look at it ;) first. As nodes are removed from the back of the list,
- * they are inserted into the front of their destintation lists.
- *
- * Things are the reverse on the resume path - iterations are done in
- * forward order, and nodes are inserted at the back of their destination
- * lists. This way, the ancestors will be accessed before their descendents.
- */
-
 static inline char *suspend_verb(u32 event)
 {
         switch (event) {
@@ -222,7 +342,6 @@ static inline char *suspend_verb(u32 event)
         }
 }
 
-
 static void
 suspend_device_dbg(struct device *dev, pm_message_t state, char *info)
 {
@@ -232,16 +351,73 @@ suspend_device_dbg(struct device *dev, pm_message_t state, char *info)
 }
 
 /**
- *      suspend_device - Save state of one device.
+ *      suspend_device_late - Shut down one device (late suspend).
  *      @dev:   Device.
  *      @state: Power state device is entering.
+ *
+ *      This is called with interrupts off and only a single CPU running.
  */
+static int suspend_device_late(struct device *dev, pm_message_t state)
+{
+        int error = 0;
 
-static int suspend_device(struct device * dev, pm_message_t state)
+        if (dev->bus && dev->bus->suspend_late) {
+                suspend_device_dbg(dev, state, "LATE ");
+                error = dev->bus->suspend_late(dev, state);
+                suspend_report_result(dev->bus->suspend_late, error);
+        }
+        return error;
+}
+
+/**
+ *      device_power_down - Shut down special devices.
+ *      @state:         Power state to enter.
+ *
+ *      Power down devices that require interrupts to be disabled
+ *      and move them from the dpm_off list to the dpm_off_irq list.
+ *      Then power down system devices.
+ *
+ *      Must be called with interrupts disabled and only one CPU running.
+ */
+int device_power_down(pm_message_t state)
+{
+        int error = 0;
+
+        while (!list_empty(&dpm_off)) {
+                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 (!error)
+                error = sysdev_suspend(state);
+        if (error)
+                dpm_power_up();
+        return error;
+}
+EXPORT_SYMBOL_GPL(device_power_down);
+
+/**
+ *      suspend_device - Save state of one device.
+ *      @dev:   Device.
+ *      @state: Power state device is entering.
+ */
+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);
@@ -264,123 +440,105 @@ 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;
-}
-
-
-/*
- * This is called with interrupts off, only a single CPU
- * running. We can't acquire a mutex or semaphore (and we don't
- * need the protection)
- */
-static int suspend_device_late(struct device *dev, pm_message_t state)
-{
-        int error = 0;
-
-        if (dev->bus && dev->bus->suspend_late) {
-                suspend_device_dbg(dev, state, "LATE ");
-                error = dev->bus->suspend_late(dev, state);
-                suspend_report_result(dev->bus->suspend_late, error);
-        }
         return error;
 }
 
 /**
- *      device_suspend - Save state and stop all devices in system.
- *      @state:         Power state to put each device in.
+ *      dpm_suspend - Suspend every device.
+ *      @state: Power state to put each device in.
  *
- *      Walk the dpm_active list, call ->suspend() for each device, and move
- *      it to the dpm_off list.
+ *      Walk the dpm_locked list.  Suspend each device and move it
+ *      to the dpm_off list.
  *
  *      (For historical reasons, if it returns -EAGAIN, that used to mean
  *      that the device would be called again with interrupts disabled.
  *      These days, we use the "suspend_late()" callback for that, so we
  *      print a warning and consider it an error).
- *
- *      If we get a different error, try and back out.
- *
- *      If we hit a failure with any of the devices, call device_resume()
- *      above to bring the suspended devices back to life.
- *
  */
-
-int device_suspend(pm_message_t state)
+static int dpm_suspend(pm_message_t state)
 {
         int error = 0;
 
-        might_sleep();
-        mutex_lock(&dpm_mtx);
         mutex_lock(&dpm_list_mtx);
-        while (!list_empty(&dpm_active) && error == 0) {
-                struct list_head * entry = dpm_active.prev;
-                struct device * dev = to_device(entry);
+        while (!list_empty(&dpm_locked)) {
+                struct list_head *entry = dpm_locked.prev;
+                struct device *dev = to_device(entry);
 
-                get_device(dev);
+                list_del_init(&dev->power.entry);
                 mutex_unlock(&dpm_list_mtx);
-
                 error = suspend_device(dev, state);
-
-                mutex_lock(&dpm_list_mtx);
-
-                /* Check if the device got removed */
-                if (!list_empty(&dev->power.entry)) {
-                        /* Move it to the dpm_off list */
-                        if (!error)
-                                list_move(&dev->power.entry, &dpm_off);
-                }
-                if (error)
+                if (error) {
                         printk(KERN_ERR "Could not suspend device %s: "
-                                "error %d%s\n",
-                                kobject_name(&dev->kobj), error,
-                                error == -EAGAIN ? " (please convert to suspend_late)" : "");
-                put_device(dev);
+                                        "error %d%s\n",
+                                        kobject_name(&dev->kobj),
+                                        error,
+                                        (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);
+                        mutex_unlock(&dpm_list_mtx);
+                        break;
+                }
+                mutex_lock(&dpm_list_mtx);
+                if (list_empty(&dev->power.entry))
+                        list_add(&dev->power.entry, &dpm_off);
         }
         mutex_unlock(&dpm_list_mtx);
-        if (error)
-                dpm_resume();
 
-        mutex_unlock(&dpm_mtx);
         return error;
 }
 
-EXPORT_SYMBOL_GPL(device_suspend);
-
 /**
- *      device_power_down - Shut down special devices.
- *      @state:         Power state to enter.
+ *      lock_all_devices - Acquire every device's semaphore
  *
- *      Walk the dpm_off_irq list, calling ->power_down() for each device that
- *      couldn't power down the device with interrupts enabled. When we're
- *      done, power down system devices.
+ *      Go through the dpm_active list. Carefully lock each device's
+ *      semaphore and put it in on the dpm_locked list.
  */
-
-int device_power_down(pm_message_t state)
+static void lock_all_devices(void)
 {
-        int error = 0;
-        struct device * dev;
+        mutex_lock(&dpm_list_mtx);
+        while (!list_empty(&dpm_active)) {
+                struct list_head *entry = dpm_active.next;
+                struct device *dev = to_device(entry);
 
-        while (!list_empty(&dpm_off)) {
-                struct list_head * entry = dpm_off.prev;
+                /* 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);
 
-                dev = to_device(entry);
-                error = suspend_device_late(dev, state);
-                if (error)
-                        goto Error;
-                list_move(&dev->power.entry, &dpm_off_irq);
+                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.
+ *
+ *      Prevent new devices from being registered, then lock all devices
+ *      and suspend them.
+ */
+int device_suspend(pm_message_t state)
+{
+        int error;
 
-        error = sysdev_suspend(state);
- Done:
+        might_sleep();
+        down_write(&pm_sleep_rwsem);
+        lock_all_devices();
+        error = dpm_suspend(state);
+        if (error)
+                device_resume();
         return error;
- Error:
-        printk(KERN_ERR "Could not power down device %s: "
-                "error %d\n", kobject_name(&dev->kobj), error);
-        dpm_power_up();
-        goto Done;
 }
-
-EXPORT_SYMBOL_GPL(device_power_down);
+EXPORT_SYMBOL_GPL(device_suspend);
 
 void __suspend_report_result(const char *function, void *fn, int ret)
 {
diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
index 379da4e958e0..10c20840395e 100644
--- a/drivers/base/power/power.h
+++ b/drivers/base/power/power.h
@@ -20,6 +20,9 @@ static inline struct device *to_device(struct list_head *entry)
 
 extern void device_pm_add(struct device *);
 extern void device_pm_remove(struct device *);
+extern void device_pm_schedule_removal(struct device *);
+extern int pm_sleep_lock(void);
+extern void pm_sleep_unlock(void);
 
 #else /* CONFIG_PM_SLEEP */
 
@@ -32,6 +35,15 @@ static inline void device_pm_remove(struct device *dev)
 {
 }
 
+static inline int pm_sleep_lock(void)
+{
+        return 0;
+}
+
+static inline void pm_sleep_unlock(void)
+{
+}
+
 #endif
 
 #ifdef CONFIG_PM