Re: PREEMPT_RCU breaks anon_vma locking ?

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Sat, Feb 24, 2007 at 10:04:04PM +0000, Hugh Dickins wrote:
> On Sat, 24 Feb 2007, Oleg Nesterov wrote:
>
> Have you checked through the SLAB_DESTROY_BY_RCU end in slab.c?
> Is what that's doing still valid?

The only thing I see needed due to PREEMPT_RCU is the following comment
change.

For a terrified few minutes, I thought that the code assumed that struct
rcu_head was the same size as struct list_head, but it turns out to only
assume that struct slab is at least as large as struct slab_rcu.

						Thanx, Paul

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

diff -urpNa -X dontdiff linux-2.6.20/mm/slab.c linux-2.6.20-slabrcufix/mm/slab.c
--- linux-2.6.20/mm/slab.c	2007-02-04 10:44:54.000000000 -0800
+++ linux-2.6.20-slabrcufix/mm/slab.c	2007-02-24 14:50:39.000000000 -0800
@@ -238,7 +238,7 @@ struct slab {
  * other kind of object (which our subsystem's lock might corrupt).
  *
  * rcu_read_lock before reading the address, then rcu_read_unlock after
- * taking the spinlock within the structure expected at that address.
+ * releasing the spinlock within the structure expected at that address.
  *
  * We assume struct slab_rcu can overlay struct slab when destroying.
  */