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authorRafael J. Wysocki <rjw@sisk.pl>2008-03-12 00:57:22 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2008-04-19 19:10:24 -0700
commit58aca23226a19983571bd3b65167521fc64f5869 (patch)
tree1fd3f54ce5f18dc972b77970289a27a4e4a39bee /Documentation/power
parent6bcf19d02a5d7e627fa054f2f10e0a8d830df326 (diff)
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PM: Handle device registrations during suspend/resume
Modify the PM core to protect its data structures, specifically the dpm_active list, from being corrupted if a child of the currently suspending device is registered concurrently with its ->suspend() callback. In that case, since the new device (the child) is added to dpm_active after its parent, the PM core will attempt to suspend it after the parent, which is wrong. Introduce a new member of struct dev_pm_info, called 'sleeping', and use it to check if the parent of the device being added to dpm_active has been suspended, in which case the device registration fails. Also, use 'sleeping' for checking if the ordering of devices on dpm_active is correct. Introduce variable 'all_sleeping' that will be set to 'true' once all devices have been suspended and make new device registrations fail until 'all_sleeping' is reset to 'false', in order to avoid having unsuspended devices around while the system is going into a sleep state. Remove pm_sleep_rwsem which is not necessary any more. Special thanks to Alan Stern for discussions and suggestions that lead to the creation of this patch. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/devices.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index 461e4f1dbec..421e7d00ffd 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -196,6 +196,11 @@ its parent; and can't be removed or suspended after that parent.
The policy is that the device tree should match hardware bus topology.
(Or at least the control bus, for devices which use multiple busses.)
+In particular, this means that a device registration may fail if the parent of
+the device is suspending (ie. has been chosen by the PM core as the next
+device to suspend) or has already suspended, as well as after all of the other
+devices have been suspended. Device drivers must be prepared to cope with such
+situations.
Suspending Devices