Re: kmemcheck caught read from freed memory (cfq_free_io_context)

On Wed, 2008-04-02 at 03:55 -0700, Paul E. McKenney wrote:
On Wed, Apr 02, 2008 at 09:28:46AM +0200, Ingo Molnar wrote:

* Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:

On Wed, Apr 02 2008, Pekka J Enberg wrote:
On Wed, 2 Apr 2008, Jens Axboe wrote:
Good catch, I wonder why it didn't complain in my testing. I've added a
patch to fix that, please see it here:

You probably don't have kmemcheck in your kernel ;-)

Ehm no, you are right :)

... and you can get kmemcheck by testing on x86.git/latest:

http://people.redhat.com/mingo/x86.git/README

;-)

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().

I don't think it does.

It would have to register an call_rcu callback itself in order to mark
it freed - and handle the race with the object being handed out again.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages