USB: update to Documentation
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>
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@ -436,7 +436,12 @@ post_reset; the USB core guarantees that this is true of internal
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suspend/resume events as well.
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If a driver wants to block all suspend/resume calls during some
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critical section, it can simply acquire udev->pm_mutex.
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critical section, it can simply acquire udev->pm_mutex. Note that
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calls to resume may be triggered indirectly. Block IO due to memory
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allocations can make the vm subsystem resume a device. Thus while
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holding this lock you must not allocate memory with GFP_KERNEL or
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GFP_NOFS.
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Alternatively, if the critical section might call some of the
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usb_autopm_* routines, the driver can avoid deadlock by doing:
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