lkml.org 
[lkml]   [2008]   [Jan]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] PM: Acquire device locks on suspend
On Mon, 7 Jan 2008, Rafael J. Wysocki wrote:

> Please see the patch at: http://lkml.org/lkml/2008/1/6/298 . It represents my
> current idea about how to do that.

It has some problems.

First, note that the list manipulations in dpm_suspend(),
device_power_down(), and so on aren't protected by dpm_list_mtx. So
your patch could corrupt the list pointers. Are you assuming that no
other threads can be running at this time?

Note also that device_pm_destroy_suspended() does up(&dev->sem), but it
doesn't know whether or not dev->sem was locked to begin with.

Do you want to rule out the possibility of a driver's suspend or remove
methods calling destroy_suspended_device() on its own device? With
your synchronous approach, this would mean that the suspend/resume
method would indirectly end up calling the remove method. This is
dangerous at best; with USB it would be a lockdep violation. With an
asynchronous approach, on the other hand, this wouldn't be a problem.

Alan Stern



\
 
 \ /
  Last update: 2008-01-07 18:25    [from the cache]
©2003-2011 Jasper Spaans