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USB: update to Documentation

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this mentions a new deadlock due to advanced power management.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Oliver Neukum
2008-07-04 10:10:53 +02:00
committed by Greg Kroah-Hartman
parent 230ffc75b7
commit f0fa74634c
1 changed files with 6 additions and 1 deletions
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7
Documentation/usb/power-management.txt
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@@ -436,7 +436,12 @@ post_reset; the USB core guarantees that this is true of internal
suspend/resume events as well. suspend/resume events as well.
If a driver wants to block all suspend/resume calls during some 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 Alternatively, if the critical section might call some of the
usb_autopm_* routines, the driver can avoid deadlock by doing: usb_autopm_* routines, the driver can avoid deadlock by doing: