• Peter Zijlstra's avatar
    mm: fix mm_take_all_locks() locking order · 7cd5a02f
    Peter Zijlstra authored
    Lockdep spotted:
    
    =======================================================
    [ INFO: possible circular locking dependency detected ]
    2.6.27-rc1 #270
    -------------------------------------------------------
    qemu-kvm/2033 is trying to acquire lock:
     (&inode->i_data.i_mmap_lock){----}, at: [<ffffffff802996cc>] mm_take_all_locks+0xc2/0xea
    
    but task is already holding lock:
     (&anon_vma->lock){----}, at: [<ffffffff8029967a>] mm_take_all_locks+0x70/0xea
    
    which lock already depends on the new lock.
    
    the existing dependency chain (in reverse order) is:
    
    -> #1 (&anon_vma->lock){----}:
           [<ffffffff8025cd37>] __lock_acquire+0x11be/0x14d2
           [<ffffffff8025d0a9>] lock_acquire+0x5e/0x7a
           [<ffffffff804c655b>] _spin_lock+0x3b/0x47
           [<ffffffff8029a2ef>] vma_adjust+0x200/0x444
           [<ffffffff8029a662>] split_vma+0x12f/0x146
           [<ffffffff8029bc60>] mprotect_fixup+0x13c/0x536
           [<ffffffff8029c203>] sys_mprotect+0x1a9/0x21e
           [<ffffffff8020c0db>] system_call_fastpath+0x16/0x1b
           [<ffffffffffffffff>] 0xffffffffffffffff
    
    -> #0 (&inode->i_data.i_mmap_lock){----}:
           [<ffffffff8025ca54>] __lock_acquire+0xedb/0x14d2
           [<ffffffff8025d397>] lock_release_non_nested+0x1c2/0x219
           [<ffffffff8025d515>] lock_release+0x127/0x14a
           [<ffffffff804c6403>] _spin_unlock+0x1e/0x50
           [<ffffffff802995d9>] mm_drop_all_locks+0x7f/0xb0
           [<ffffffff802a965d>] do_mmu_notifier_register+0xe2/0x112
           [<ffffffff802a96a8>] mmu_notifier_register+0xe/0x10
           [<ffffffffa0043b6b>] kvm_dev_ioctl+0x11e/0x287 [kvm]
           [<ffffffff802bd0ca>] vfs_ioctl+0x2a/0x78
           [<ffffffff802bd36f>] do_vfs_ioctl+0x257/0x274
           [<ffffffff802bd3e1>] sys_ioctl+0x55/0x78
           [<ffffffff8020c0db>] system_call_fastpath+0x16/0x1b
           [<ffffffffffffffff>] 0xffffffffffffffff
    
    other info that might help us debug this:
    
    5 locks held by qemu-kvm/2033:
     #0:  (&mm->mmap_sem){----}, at: [<ffffffff802a95d0>] do_mmu_notifier_register+0x55/0x112
     #1:  (mm_all_locks_mutex){--..}, at: [<ffffffff8029963e>] mm_take_all_locks+0x34/0xea
     #2:  (&anon_vma->lock){----}, at: [<ffffffff8029967a>] mm_take_all_locks+0x70/0xea
     #3:  (&anon_vma->lock){----}, at: [<ffffffff8029967a>] mm_take_all_locks+0x70/0xea
     #4:  (&anon_vma->lock){----}, at: [<ffffffff8029967a>] mm_take_all_locks+0x70/0xea
    
    stack backtrace:
    Pid: 2033, comm: qemu-kvm Not tainted 2.6.27-rc1 #270
    
    Call Trace:
     [<ffffffff8025b7c7>] print_circular_bug_tail+0xb8/0xc3
     [<ffffffff8025ca54>] __lock_acquire+0xedb/0x14d2
     [<ffffffff80259bb1>] ? add_lock_to_list+0x7e/0xad
     [<ffffffff8029967a>] ? mm_take_all_locks+0x70/0xea
     [<ffffffff8029967a>] ? mm_take_all_locks+0x70/0xea
     [<ffffffff8025d397>] lock_release_non_nested+0x1c2/0x219
     [<ffffffff802996cc>] ? mm_take_all_locks+0xc2/0xea
     [<ffffffff802996cc>] ? mm_take_all_locks+0xc2/0xea
     [<ffffffff8025b202>] ? trace_hardirqs_on_caller+0x4d/0x115
     [<ffffffff802995d9>] ? mm_drop_all_locks+0x7f/0xb0
     [<ffffffff8025d515>] lock_release+0x127/0x14a
     [<ffffffff804c6403>] _spin_unlock+0x1e/0x50
     [<ffffffff802995d9>] mm_drop_all_locks+0x7f/0xb0
     [<ffffffff802a965d>] do_mmu_notifier_register+0xe2/0x112
     [<ffffffff802a96a8>] mmu_notifier_register+0xe/0x10
     [<ffffffffa0043b6b>] kvm_dev_ioctl+0x11e/0x287 [kvm]
     [<ffffffff8033f9f2>] ? file_has_perm+0x83/0x8e
     [<ffffffff802bd0ca>] vfs_ioctl+0x2a/0x78
     [<ffffffff802bd36f>] do_vfs_ioctl+0x257/0x274
     [<ffffffff802bd3e1>] sys_ioctl+0x55/0x78
     [<ffffffff8020c0db>] system_call_fastpath+0x16/0x1b
    
    Which the locking hierarchy in mm/rmap.c confirms as valid.
    
    Fix this by first taking all the mapping->i_mmap_lock instances and then
    take all anon_vma->lock instances.
    Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: default avatarHugh Dickins <hugh@veritas.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    7cd5a02f
mmap.c 63.6 KB