On Wed, Sep 28, 2011 at 11:21:58AM +0900, KOSAKI Motohiro wrote: > (2011/09/28 10:45), Minchan Kim wrote: > > When racing between putback_lru_page and shmem_unlock 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. > > Do we still need this after Hannes removes scan_mapping_unevictable_pages? Hi KOSAKI, What Hannes removes is scan_zone_unevictable_pages not scan_mapping_unevictable_pages. -- Kinds regards, Minchan Kim -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>