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Merge branch 'pm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6

* 'pm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6:
  PM / Runtime: Update documentation regarding driver removal
  PM: Documentation: fix typo: pm_runtime_idle_sync() doesn't exist.
Linus Torvalds пре 14 година
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1 измењених фајлова са 21 додато и 5 уклоњено
  1. 21 5
      Documentation/power/runtime_pm.txt

+ 21 - 5
Documentation/power/runtime_pm.txt

@@ -501,13 +501,29 @@ helper functions described in Section 4.  In that case, pm_runtime_resume()
 should be used.  Of course, for this purpose the device's run-time PM has to be
 should be used.  Of course, for this purpose the device's run-time PM has to be
 enabled earlier by calling pm_runtime_enable().
 enabled earlier by calling pm_runtime_enable().
 
 
-If the device bus type's or driver's ->probe() or ->remove() callback runs
+If the device bus type's or driver's ->probe() callback runs
 pm_runtime_suspend() or pm_runtime_idle() or their asynchronous counterparts,
 pm_runtime_suspend() or pm_runtime_idle() or their asynchronous counterparts,
 they will fail returning -EAGAIN, because the device's usage counter is
 they will fail returning -EAGAIN, because the device's usage counter is
-incremented by the core before executing ->probe() and ->remove().  Still, it
-may be desirable to suspend the device as soon as ->probe() or ->remove() has
-finished, so the PM core uses pm_runtime_idle_sync() to invoke the
-subsystem-level idle callback for the device at that time.
+incremented by the driver core before executing ->probe().  Still, it may be
+desirable to suspend the device as soon as ->probe() has finished, so the driver
+core uses pm_runtime_put_sync() to invoke the subsystem-level idle callback for
+the device at that time.
+
+Moreover, the driver core prevents runtime PM callbacks from racing with the bus
+notifier callback in __device_release_driver(), which is necessary, because the
+notifier is used by some subsystems to carry out operations affecting the
+runtime PM functionality.  It does so by calling pm_runtime_get_sync() before
+driver_sysfs_remove() and the BUS_NOTIFY_UNBIND_DRIVER notifications.  This
+resumes the device if it's in the suspended state and prevents it from
+being suspended again while those routines are being executed.
+
+To allow bus types and drivers to put devices into the suspended state by
+calling pm_runtime_suspend() from their ->remove() routines, the driver core
+executes pm_runtime_put_sync() after running the BUS_NOTIFY_UNBIND_DRIVER
+notifications in __device_release_driver().  This requires bus types and
+drivers to make their ->remove() callbacks avoid races with runtime PM directly,
+but also it allows of more flexibility in the handling of devices during the
+removal of their drivers.
 
 
 The user space can effectively disallow the driver of the device to power manage
 The user space can effectively disallow the driver of the device to power manage
 it at run time by changing the value of its /sys/devices/.../power/control
 it at run time by changing the value of its /sys/devices/.../power/control