pm / runtime: force memory allocation with no I/O during Runtime PM callbcack

[karo-tx-linux.git] / drivers / base / power / runtime.c

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 3148b10dc2e59b92dd5913e2b34c446d54ac69b7..1244930e3d7a4ae73843afb7ecb34c356a5cc72b 100644 (file)
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -124,6 +124,76 @@ unsigned long pm_runtime_autosuspend_expiration(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(pm_runtime_autosuspend_expiration);
 
+static int dev_memalloc_noio(struct device *dev, void *data)
+{
+       return dev->power.memalloc_noio;
+}
+
+/*
+ * pm_runtime_set_memalloc_noio - Set a device's memalloc_noio flag.
+ * @dev: Device to handle.
+ * @enable: True for setting the flag and False for clearing the flag.
+ *
+ * Set the flag for all devices in the path from the device to the
+ * root device in the device tree if @enable is true, otherwise clear
+ * the flag for devices in the path whose siblings don't set the flag.
+ *
+ * The function should only be called by block device, or network
+ * device driver for solving the deadlock problem during runtime
+ * resume/suspend:
+ *
+ *     If memory allocation with GFP_KERNEL is called inside runtime
+ *     resume/suspend callback of any one of its ancestors(or the
+ *     block device itself), the deadlock may be triggered inside the
+ *     memory allocation since it might not complete until the block
+ *     device becomes active and the involed page I/O finishes. The
+ *     situation is pointed out first by Alan Stern. Network device
+ *     are involved in iSCSI kind of situation.
+ *
+ * The lock of dev_hotplug_mutex is held in the function for handling
+ * hotplug race because pm_runtime_set_memalloc_noio() may be called
+ * in async probe().
+ *
+ * The function should be called between device_add() and device_del()
+ * on the affected device(block/network device).
+ */
+void pm_runtime_set_memalloc_noio(struct device *dev, bool enable)
+{
+       static DEFINE_MUTEX(dev_hotplug_mutex);
+
+       mutex_lock(&dev_hotplug_mutex);
+       for (;;) {
+               bool enabled;
+
+               /* hold power lock since bitfield is not SMP-safe. */
+               spin_lock_irq(&dev->power.lock);
+               enabled = dev->power.memalloc_noio;
+               dev->power.memalloc_noio = enable;
+               spin_unlock_irq(&dev->power.lock);
+
+               /*
+                * not need to enable ancestors any more if the device
+                * has been enabled.
+                */
+               if (enabled && enable)
+                       break;
+
+               dev = dev->parent;
+
+               /*
+                * clear flag of the parent device only if all the
+                * children don't set the flag because ancestor's
+                * flag was set by any one of the descendants.
+                */
+               if (!dev || (!enable &&
+                            device_for_each_child(dev, NULL,
+                                                  dev_memalloc_noio)))
+                       break;
+       }
+       mutex_unlock(&dev_hotplug_mutex);
+}
+EXPORT_SYMBOL_GPL(pm_runtime_set_memalloc_noio);
+
 /**
  * rpm_check_suspend_allowed - Test whether a device may be suspended.
  * @dev: Device to test.
@@ -278,7 +348,24 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
        if (!cb)
                return -ENOSYS;
 
-       retval = __rpm_callback(cb, dev);
+       if (dev->power.memalloc_noio) {
+               unsigned int noio_flag;
+
+               /*
+                * Deadlock might be caused if memory allocation with
+                * GFP_KERNEL happens inside runtime_suspend and
+                * runtime_resume callbacks of one block device's
+                * ancestor or the block device itself. Network
+                * device might be thought as part of iSCSI block
+                * device, so network device and its ancestor should
+                * be marked as memalloc_noio too.
+                */
+               noio_flag = memalloc_noio_save();
+               retval = __rpm_callback(cb, dev);
+               memalloc_noio_restore(noio_flag);
+       } else {
+               retval = __rpm_callback(cb, dev);
+       }
 
        dev->power.runtime_error = retval;
        return retval != -EACCES ? retval : -EIO;