On 09/07/2015 07:40 AM, Kirill A. Shutemov wrote: > On Sun, Sep 06, 2015 at 03:21:05PM -0400, Sasha Levin wrote: >> > ================================================================== >> > ThreadSanitizer: data-race in munlock_vma_pages_range >> > >> > Write of size 8 by thread T378 (K2633, CPU3): >> > [<ffffffff81212579>] munlock_vma_pages_range+0x59/0x3e0 mm/mlock.c:425 >> > [<ffffffff81212ac9>] mlock_fixup+0x1c9/0x280 mm/mlock.c:549 >> > [<ffffffff81212ccc>] do_mlock+0x14c/0x180 mm/mlock.c:589 >> > [< inlined >] SyS_munlock+0x74/0xb0 SYSC_munlock mm/mlock.c:651 >> > [<ffffffff812130b4>] SyS_munlock+0x74/0xb0 mm/mlock.c:643 >> > [<ffffffff81eb352e>] entry_SYSCALL_64_fastpath+0x12/0x71 >> > arch/x86/entry/entry_64.S:186 > ... > >> > Previous read of size 8 by thread T398 (K2623, CPU2): >> > [<ffffffff8121d198>] try_to_unmap_one+0x78/0x4f0 mm/rmap.c:1208 >> > [< inlined >] rmap_walk+0x147/0x450 rmap_walk_file mm/rmap.c:1540 >> > [<ffffffff8121e7b7>] rmap_walk+0x147/0x450 mm/rmap.c:1559 >> > [<ffffffff8121ef72>] try_to_munlock+0xa2/0xc0 mm/rmap.c:1423 >> > [<ffffffff81211bb0>] __munlock_isolated_page+0x30/0x60 mm/mlock.c:129 >> > [<ffffffff81212066>] __munlock_pagevec+0x236/0x3f0 mm/mlock.c:331 >> > [<ffffffff812128a0>] munlock_vma_pages_range+0x380/0x3e0 mm/mlock.c:476 >> > [<ffffffff81212ac9>] mlock_fixup+0x1c9/0x280 mm/mlock.c:549 >> > [<ffffffff81212ccc>] do_mlock+0x14c/0x180 mm/mlock.c:589 >> > [< inlined >] SyS_munlock+0x74/0xb0 SYSC_munlock mm/mlock.c:651 >> > [<ffffffff812130b4>] SyS_munlock+0x74/0xb0 mm/mlock.c:643 >> > [<ffffffff81eb352e>] entry_SYSCALL_64_fastpath+0x12/0x71 >> > arch/x86/entry/entry_64.S:186 > Okay, the detected race is mlock/munlock vs. rmap. > > On rmap side we check vma->vm_flags in few places without taking > vma->vm_mm->mmap_sem. The vma cannot be freed since we hold i_mmap_rwsem > or anon_vma_lock, but nothing prevent vma->vm_flags from changing under > us. > > In this particular case, speculative check in beginning of > try_to_unmap_one() is fine, since we re-check it under mmap_sem later in > the function. So you're suggesting that this isn't the cause of the bad page flags error observed by Andrey and myself? Thanks, Sasha -- 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>