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Commit f0fa7463 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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USB: update to Documentation 



this mentions a new deadlock due to advanced power management.

Signed-off-by: default avatarOliver Neukum <oneukum@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 230ffc75

Documentation/usb/power-management.txt

+6 −1
Original line number Diff line number Diff line
@@ -436,7 +436,12 @@ post_reset; the USB core guarantees that this is true of internal 
suspend/resume events as well.



If a driver wants to block all suspend/resume calls during some

critical section, it can simply acquire udev->pm_mutex.

critical section, it can simply acquire udev->pm_mutex. Note that

calls to resume may be triggered indirectly. Block IO due to memory

allocations can make the vm subsystem resume a device. Thus while

holding this lock you must not allocate memory with GFP_KERNEL or

GFP_NOFS.



Alternatively, if the critical section might call some of the

usb_autopm_* routines, the driver can avoid deadlock by doing: