lkml.org 
[lkml]   [2008]   [Apr]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: kmemcheck caught read from freed memory (cfq_free_io_context)
From
Date
On Wed, 2008-04-02 at 13:07 +0200, Jens Axboe wrote:
> On Wed, Apr 02 2008, Pekka Enberg wrote:
> > Hi Paul,
> >
> > On Wed, Apr 2, 2008 at 1:55 PM, Paul E. McKenney
> > <paulmck@linux.vnet.ibm.com> wrote:
> > > I will check this when I get back to some bandwidth -- but in the meantime,
> > > does kmemcheck special-case SLAB_DESTROY_BY_RCU? It is legal to access
> > > newly-freed items in that case, as long as you did rcu_read_lock()
> > > before gaining a reference to them and don't hold the reference past
> > > the matching rcu_read_unlock().
> >
> > No, kmemcheck is work in progress and does not know about
> > SLAB_DESTROY_BY_RCU yet. The reason I asked Vegard to post the warning
> > was because Peter, Vegard, and myself identified this particular
> > warning as a real problem. But yeah, kmemcheck can cause false
> > positives for RCU for now.
>
> Makes sense, and to me Pauls analysis of the code looks totally correct
> - there's no bug there, at least related to hlist traversal and
> kmem_cache_free(), since we are under rcu_read_lock() and thus hold off
> the grace for freeing.

but what holds off the slab allocator re-issueing that same object and
someone else writing other stuff into it?



\
 
 \ /
  Last update: 2008-04-02 13:11    [W:0.481 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site