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