On 2016/6/23 17:34, Michal Hocko wrote: > On Thu 23-06-16 11:29:46, Michal Hocko wrote: >> On Wed 22-06-16 23:05:24, zhong jiang wrote: >>> Hi Aneesh >>> >>> CPU0 CPU1 >>> shrink_page_list() >>> add_to_swap() >>> split_huge_page_to_list() >>> __split_huge_pmd_locked() >>> pmdp_huge_clear_flush_notify() >>> // pmd_none() == true >>> exit_mmap() >>> unmap_vmas() >>> zap_pmd_range() >>> // no action on pmd since pmd_none() == true >>> pmd_populate() >>> >>> >>> the mm should be the last user when CPU1 process is exiting, CPU0 must be a own mm . >>> two different process should not be influenced each other. in a words , they should not >>> have race. >> No this is a different scenario than >> http://lkml.kernel.org/r/1466517956-13875-1-git-send-email-zhongjiang@xxxxxxxxxx >> we were discussing recently. Note that pages are still on the LRU lists >> while the mm which maps them is exiting. So the above race is very much >> possible. > And just to clarify, I haven't checked the current code after c777e2a8b654 > ("powerpc/mm: Fix Multi hit ERAT cause by recent THP update") which is > ppc specific and I have no idea whether other arches need a similar > treatment. I was merely trying to explain that the mm exclusive argument > doesn't apply to reclaim vs. exit races. Thank for your explaintion! -- 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>