linux-kernel - Re: [PATCH] arm, kvm: fix double lock on cpu_add_remove

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Date:	Tue, 08 Apr 2014 13:33:55 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Ming Lei <tom.leiming@...il.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"ego@...ux.vnet.ibm.com" <ego@...ux.vnet.ibm.com>
Subject: Re: [PATCH] arm, kvm: fix double lock on cpu_add_remove_lock

On Monday, April 07, 2014 12:14:22 PM Srivatsa S. Bhat wrote:
> On 04/06/2014 11:06 PM, Ming Lei wrote:
> > The patch of "arm, kvm: Fix CPU hotplug callback registration"
> > in -next tree holds the lock before calling the two functions:
> > 
> > 	kvm_vgic_hyp_init()
> > 	kvm_timer_hyp_init()
> > 
> > and both the two functions are calling register_cpu_notifier()
> > to register cpu notifier, so cause double lock on cpu_add_remove_lock.
> > 
> > Considered that both two functions are only called inside
> > kvm_arch_init() with holding cpu_add_remove_lock, so simply use
> > __register_cpu_notifier() to fix the problem.
> > 
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Christoffer Dall <christoffer.dall@...aro.org>
> > Cc: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Signed-off-by: Ming Lei <tom.leiming@...il.com>
> 
> Sorry for missing that, and thank you for the fix!
> 
> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

Applied, thanks!

I'm going to include this into my next pull request.

> > ---
> >  virt/kvm/arm/arch_timer.c |    2 +-
> >  virt/kvm/arm/vgic.c       |    2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> > index 5081e80..22fa819 100644
> > --- a/virt/kvm/arm/arch_timer.c
> > +++ b/virt/kvm/arm/arch_timer.c
> > @@ -277,7 +277,7 @@ int kvm_timer_hyp_init(void)
> > 
> >  	host_vtimer_irq = ppi;
> > 
> > -	err = register_cpu_notifier(&kvm_timer_cpu_nb);
> > +	err = __register_cpu_notifier(&kvm_timer_cpu_nb);
> >  	if (err) {
> >  		kvm_err("Cannot register timer CPU notifier\n");
> >  		goto out_free;
> > diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> > index 8ca405c..47b2983 100644
> > --- a/virt/kvm/arm/vgic.c
> > +++ b/virt/kvm/arm/vgic.c
> > @@ -1496,7 +1496,7 @@ int kvm_vgic_hyp_init(void)
> >  		goto out;
> >  	}
> > 
> > -	ret = register_cpu_notifier(&vgic_cpu_nb);
> > +	ret = __register_cpu_notifier(&vgic_cpu_nb);
> >  	if (ret) {
> >  		kvm_err("Cannot register vgic CPU notifier\n");
> >  		goto out_free_irq;
> > 
> 
> --
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-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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