lkml.org 
[lkml]   [2012]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: Race condition between driver_probe_device and device_shutdown
From
> Because device_del() will put reference count of the parent, and the patch
> only focuses on race between probe/release and shutdown.

Right. device_del() puts the reference count of the parent -- is it
guaranteed that device_del() won't ever reassign dev->parent though
(e.g., to NULL)? I don't think it is, so I think that patch should
also save the pointer to the parent and use it (instead of what
happens to be in than dev->parent) to release the lock and put the
ref.

> As far as device_move() concerned, looks it might be a problem.
> The problem even exits on driver attach vs. device open/release,
> if device_move is called in open() and open() happens before driver
> attach completes.

Yeah, the pattern of locking the parent followed by the device occurs
in a few places. It looks like they were added by Alan with commit
bf74ad5bc41727d5f2f1c6bedb2c1fac394de731. (And as Greg mentioned,
might be occurring often enough to merit being moved into a common
function.)

I guess the question is whether the callee is allowed to call
device_move(), if not, we're good.

> Your concern on device_remove() might be correct. Also, I am wondering
> if we can walk the 'dpm_list' backwards for device shutdown, which should
> be simpler and more reasonable.

How would that help?


\
 
 \ /
  Last update: 2012-12-07 13:41    [W:0.976 / U:0.864 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site