RE: [RFC PATCH v4 08/18] kvm: add the VM introspection subsystem

[Mircea CIRJALIU-MELIU <mcirjaliu@bitdefender.com>]

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> -----Original Message-----
> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> Sent: Friday, 22 December 2017 18:02
> To: Adalber Lazăr <alazar@bitdefender.com>; kvm@vger.kernel.org
> Cc: linux-mm@kvack.org; Radim Krčmář <rkrcmar@redhat.com>; Xiao
> Guangrong <guangrong.xiao@linux.intel.com>; Mihai Donțu
> <mdontu@bitdefender.com>; Nicusor CITU <ncitu@bitdefender.com>;
> Mircea CIRJALIU-MELIU <mcirjaliu@bitdefender.com>; Marian Cristian
> ROTARIU <mrotariu@bitdefender.com>
> Subject: Re: [RFC PATCH v4 08/18] kvm: add the VM introspection subsystem
> 
> On 18/12/2017 20:06, Adalber Lazăr wrote:
> > +	/* VMAs will be modified */
> > +	down_write(&req_mm->mmap_sem);
> > +	down_write(&map_mm->mmap_sem);
> > +
> 
> Is there a locking rule when locking multiple mmap_sems at the same
> time?  As it's written, this can cause deadlocks.

First req_mm, second map_mm.
The other function uses the same nesting.

> 
> Paolo
> 
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