lkml.org 
[lkml]   [2011]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: lockdep recursive locking detected (rcu_kthread / __cache_free)
On Mon, Oct 03, 2011 at 03:46:11PM -0500, Christoph Lameter wrote:
> On Mon, 3 Oct 2011, Paul E. McKenney wrote:
>
> > The first lock was acquired here in an RCU callback. The later lock that
> > lockdep complained about appears to have been acquired from a recursive
> > call to __cache_free(), with no help from RCU. This looks to me like
> > one of the issues that arise from the slab allocator using itself to
> > allocate slab metadata.
>
> Right. However, this is a false positive since the slab cache with
> the metadata is different from the slab caches with the slab data. The slab
> cache with the metadata does not use itself any metadata slab caches.

Wouldn't it be possible to pass a new flag to the metadata slab caches
upon creation so that their locks could be placed in a separate lock
class? Just allocate a separate lock_class_key structure for each such
lock in that case, and then use lockdep_set_class_and_name to associate
that structure with the corresponding lock. I do this in kernel/rcutree.c
in order to allow the rcu_node tree's locks to nest properly.

Thanx, Paul


\
 
 \ /
  Last update: 2011-10-04 02:07    [from the cache]
©2003-2011 Jasper Spaans