On Fri, 5 Apr 2013, Minchan Kim wrote: > Now, memory barrier in __do_huge_pmd_anonymous_page doesn't work. > Because lru_cache_add_lru uses pagevec so it could miss spinlock > easily so above rule was broken so user might see inconsistent data. > > I was not first person who pointed out the problem. Mel and Peter > pointed out a few months ago and Peter pointed out further that > even spin_lock/unlock can't make sure it. > http://marc.info/?t=134333512700004 > > In particular: > > *A = a; > LOCK > UNLOCK > *B = b; > > may occur as: > > LOCK, STORE *B, STORE *A, UNLOCK > > At last, Hugh pointed out that even we don't need memory barrier > in there because __SetPageUpdate already have done it from > Nick's [1] explicitly. > > So this patch fixes comment on THP and adds same comment for > do_anonymous_page, too because everybody except Hugh was missing > that. It means we needs COMMENT about that. > > [1] 0ed361dec "mm: fix PageUptodate data race" > > Cc: Mel Gorman <[email protected]> > Cc: Hugh Dickins <[email protected]> > Cc: Kamezawa Hiroyuki <[email protected]> > Cc: David Rientjes <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Acked-by: Andrea Arcangeli <[email protected]> > Signed-off-by: Minchan Kim <[email protected]>
Acked-by: David Rientjes <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
