(2011/09/28 11:25), Minchan Kim wrote: > 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. > Oops, you are right. -- 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>