On Tue, May 17, 2016 at 04:42:55PM +0900, Naoya Horiguchi wrote: > There's a race window between checking page->flags and unpoisoning, which > taints kernel with "BUG: Bad page state". That's overkill. It's safer to > use bad_flags to detect hwpoisoned page. > I'm not quite getting this one. Minimally, instead of = __PG_HWPOISON, it should have been (bad_flags & __PG_POISON). As Vlastimil already pointed out, __PG_HWPOISON can be 0. What I'm not getting is why this fixes the race. The current race is 1. Check poison, set bad_flags 2. poison clears in parallel 3. Check page->flag state in bad_page and trigger warning The code changes it to 1. Check poison, set bad_flags 2. poison clears in parallel 3. Check bad_flags and trigger warning There is warning either way. What did I miss? -- Mel Gorman SUSE Labs -- 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>