Re: [PATCH 00/21] mm: Preemptibility -v6
From: Peter Zijlstra <peterz@infradead.org>
Date: 2011-01-24 12:21:28
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linux-mm, lkml
On Fri, 2011-01-21 at 16:33 +0100, Peter Zijlstra wrote:
quoted hunk ↗ jump to hunk
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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>