linux-kernel - Re: Circular vma locking with kvm, seems to be mmu notifiers related

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Message-ID: <48A29D0D.9010801@qumranet.com>
Date:	Wed, 13 Aug 2008 11:36:29 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Max Krasnyansky <maxk@...lcomm.com>
CC:	LKML <linux-kernel@...r.kernel.org>, andrea@...ranet.com
Subject: Re: Circular vma locking with kvm, seems to be mmu notifiers related

Max Krasnyansky wrote:
> Got this on the latest mainline git.
> There are already a couple of lockdep/kvm threads. So maybe it's known.
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 2.6.27-rc2 #36
> ---------------------------------------------
> qemu-system-x86/3445 is trying to acquire lock:
>  (&anon_vma->lock){--..}, at: [<ffffffff8029f84d>] mm_take_all_locks+0x8d/0xf0
>
> but task is already holding lock:
>  (&anon_vma->lock){--..}, at: [<ffffffff8029f84d>] mm_take_all_locks+0x8d/0xf0
>
>   

Seems to be a false positive.  mmu_take_all_locks takes (surprise!) all 
anon_vma->locks belonging to an mm, and takes special care not to 
deadlock while doing this.

We need to communicate this to lockdep somehow.

-- 
error compiling committee.c: too many arguments to function

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