lkml.org 
[lkml]   [2011]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 00/21] mm: Preemptibility -v6
From
Date
On Fri, 2011-01-21 at 16:33 +0100, Peter Zijlstra wrote:

> Index: linux-2.6/mm/rmap.c
> ===================================================================
> --- linux-2.6.orig/mm/rmap.c
> +++ linux-2.6/mm/rmap.c
> @@ -1559,9 +1559,20 @@ void __put_anon_vma(struct anon_vma *ano
> * Synchronize against page_lock_anon_vma() such that
> * we can safely hold the lock without the anon_vma getting
> * freed.
> + *
> + * Relies on the full mb implied by the atomic_dec_and_test() from
> + * put_anon_vma() against the full mb implied by mutex_trylock() from
> + * page_lock_anon_vma(). This orders:
> + *
> + * page_lock_anon_vma() VS put_anon_vma()
> + * mutex_trylock() atomic_dec_and_test()
> + * smp_mb() smp_mb()
> + * atomic_read() mutex_is_locked()

Bah!, I thought all mutex_trylock() implementations used an atomic op
with return value (which implies a mb), but it looks like (at least*)
PPC doesn't and only provides a LOCK barrier.


* possibly ARM and SH don't either, but I can't read either ASMs well
enough to tell.



\
 
 \ /
  Last update: 2011-01-24 13:23    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site