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. -- Kirill A. Shutemov -- 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>