On Tue, 2 Apr 2013, Minchan Kim wrote: > On Mon, Apr 01, 2013 at 04:35:38PM -0700, David Rientjes wrote: > > On Mon, 1 Apr 2013, Minchan Kim wrote: > > > > > __do_huge_pmd_anonymous_page depends on page_add_new_anon_rmap's > > > spinlock for making sure that clear_huge_page write become visible > > > after set set_pmd_at() write. > > > > > > But lru_cache_add_lru uses pagevec so it could miss spinlock > > > easily so above rule was broken so user may see inconsistent data. > > > > > > This patch fixes it with using explict barrier rather than depending > > > on lru spinlock. > > > > > > > Is this the same issue that Andrea responded to in the "thp and memory > > barrier assumptions" thread at http://marc.info/?t=134333512700004 ? > > Yes and Peter pointed out further step. > Thanks for pointing out. > Not that I know that Andrea alreay noticed it, I don't care about this > patch. > > Remaining question is Kame's one. > > Hmm...how about do_anonymous_page() ? there are no comments/locks/barriers. > > Users can see non-zero value after page fault in theory ? > Isn't there anyone could answer it? See Nick's 2008 0ed361dec "mm: fix PageUptodate data race", which gave us static inline void __SetPageUptodate(struct page *page) { smp_wmb(); __set_bit(PG_uptodate, &(page)->flags); } So both do_anonymous_page() and __do_huge_pmd_anonymous_page() look safe to me already, though the huge_memory one could do with a fixed comment. Hugh -- 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>