(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? > > This patch adds a barrier after mapping_clear_unevictable. > > side-note: I didn't meet this problem but just found during review. -- 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>