On Tue 12-01-16 16:52:19, Kirill A. Shutemov wrote: > On Tue, Jan 12, 2016 at 03:45:21PM +0100, Michal Hocko wrote: > > On Mon 11-01-16 14:05:28, Kirill A. Shutemov wrote: > > > Dmitry Vyukov has reported[1] possible deadlock (triggered by his syzkaller > > > fuzzer): > > > > > > Possible unsafe locking scenario: > > > > > > CPU0 CPU1 > > > ---- ---- > > > lock(&hugetlbfs_i_mmap_rwsem_key); > > > lock(&mapping->i_mmap_rwsem); > > > lock(&hugetlbfs_i_mmap_rwsem_key); > > > lock(&mapping->i_mmap_rwsem); > > > > > > Both traces points to mm_take_all_locks() as a source of the problem. > > > It doesn't take care about ordering or hugetlbfs_i_mmap_rwsem_key (aka > > > mapping->i_mmap_rwsem for hugetlb mapping) vs. i_mmap_rwsem. > > > > Hmm, but huge_pmd_share is called with mmap_sem held no? > > Why does it matter? > > Both mappings can be mapped to different processes, so mmap_sem is no good > here. You are right! Then it really makes a differencec. Feel free to add Reviewed-by: Michal Hocko <mhocko@xxxxxxxx> -- Michal Hocko SUSE Labs -- 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>