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 <mgorman@xxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Acked-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>