Messages in this thread | | | Date | Fri, 4 Jan 2013 13:49:37 +0100 (CET) | From | Jiri Kosina <> | Subject | 3.8-rc2: lockdep is complaining about mm_take_all_locks() |
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This is almost certainly because
commit 5a505085f043e8380f83610f79642853c051e2f1 Author: Ingo Molnar <mingo@kernel.org> Date: Sun Dec 2 19:56:46 2012 +0000
mm/rmap: Convert the struct anon_vma::mutex to an rwsem
did this to mm_take_all_locks():
- mutex_lock_nest_lock(&anon_vma->root->mutex, &mm->mmap_sem); + down_write(&anon_vma->root->rwsem);
killing the lockdep annotation that has been there since
commit 454ed842d55740160334efc9ad56cfef54ed37bc Author: Peter Zijlstra <a.p.zijlstra@chello.nl> Date: Mon Aug 11 09:30:25 2008 +0200
lockdep: annotate mm_take_all_locks()
The locking is obviously correct due to mmap_sem being held throughout the whole operation, but I am not completely sure how to annotate this properly for lockdep in down_write() case though. Ingo, please?
============================================= [ INFO: possible recursive locking detected ] 3.8.0-rc2-00036-g5f73896 #171 Not tainted --------------------------------------------- qemu-kvm/2315 is trying to acquire lock: (&anon_vma->rwsem){+.+...}, at: [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0 but task is already holding lock: (&anon_vma->rwsem){+.+...}, at: [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&anon_vma->rwsem); lock(&anon_vma->rwsem); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by qemu-kvm/2315: #0: (&mm->mmap_sem){++++++}, at: [<ffffffff81177f1c>] do_mmu_notifier_register+0xfc/0x170 #1: (mm_all_locks_mutex){+.+...}, at: [<ffffffff8115d436>] mm_take_all_locks+0x36/0x1b0 #2: (&mapping->i_mmap_mutex){+.+...}, at: [<ffffffff8115d4c9>] mm_take_all_locks+0xc9/0x1b0 #3: (&anon_vma->rwsem){+.+...}, at: [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0 stack backtrace: Pid: 2315, comm: qemu-kvm Not tainted 3.8.0-rc2-00036-g5f73896 #171 Call Trace: [<ffffffff810afea2>] print_deadlock_bug+0xf2/0x100 [<ffffffff810b1a76>] validate_chain+0x4f6/0x720 [<ffffffff810b1ff9>] __lock_acquire+0x359/0x580 [<ffffffff810b0e7d>] ? trace_hardirqs_on_caller+0x12d/0x1b0 [<ffffffff810b2341>] lock_acquire+0x121/0x190 [<ffffffff8115d549>] ? mm_take_all_locks+0x149/0x1b0 [<ffffffff815a12bf>] down_write+0x3f/0x70 [<ffffffff8115d549>] ? mm_take_all_locks+0x149/0x1b0 [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0 [<ffffffff81177e88>] do_mmu_notifier_register+0x68/0x170 [<ffffffff81177fae>] mmu_notifier_register+0xe/0x10 [<ffffffffa04bd6ab>] kvm_create_vm+0x22b/0x330 [kvm] [<ffffffffa04bd8a8>] kvm_dev_ioctl+0xf8/0x1a0 [kvm] [<ffffffff811a45bd>] do_vfs_ioctl+0x9d/0x350 [<ffffffff815ad215>] ? sysret_check+0x22/0x5d [<ffffffff811a4901>] sys_ioctl+0x91/0xb0 [<ffffffff815ad1e9>] system_call_fastpath+0x16/0x1b
-- Jiri Kosina SUSE Labs
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