From f0fa74634c0c686618b5318748bde233772a1a8d Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Fri, 4 Jul 2008 10:10:53 +0200 Subject: [PATCH] USB: update to Documentation this mentions a new deadlock due to advanced power management. Signed-off-by: Oliver Neukum Signed-off-by: Greg Kroah-Hartman --- Documentation/usb/power-management.txt | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt index b2fc4d4a9917..9d31140e3f5b 100644 --- a/Documentation/usb/power-management.txt +++ b/Documentation/usb/power-management.txt @@ -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: -- 2.20.1