Messages in this thread | | | From | KOSAKI Motohiro <> | Date | Thu, 29 Sep 2011 21:50:02 +0900 | Subject | Re: [PATCH v2] vmscan: add barrier to prevent evictable page in unevictable list |
| |
2011/9/29 Minchan Kim <minchan.kim@gmail.com>: > When racing between putback_lru_page and shmem_lock with lock=0 happens, > progrom execution order is as follows, but clear_bit in processor #1 > could be reordered right before spin_unlock of processor #1. > Then, the page would be stranded on the unevictable list. > > spin_lock > SetPageLRU > spin_unlock > clear_bit(AS_UNEVICTABLE) > spin_lock > if PageLRU() > if !test_bit(AS_UNEVICTABLE) > move evictable list > smp_mb > if !test_bit(AS_UNEVICTABLE) > move evictable list > spin_unlock > > But, pagevec_lookup in scan_mapping_unevictable_pages has rcu_read_[un]lock so > it could protect reordering before reaching test_bit(AS_UNEVICTABLE) on processor #1 > so this problem never happens. But it's a unexpected side effect and we should > solve this problem properly. > > This patch adds a barrier after mapping_clear_unevictable. > > side-note: I didn't meet this problem but just found during review. > > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Cc: Mel Gorman <mel@csn.ul.ie> > Cc: Rik van Riel <riel@redhat.com> > Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> > Acked-by: Johannes Weiner <jweiner@redhat.com> > Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |