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

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Message-ID: <53424946.4000504@linux.vnet.ibm.com>
Date:	Mon, 07 Apr 2014 12:14:22 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	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 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>

Regards,
Srivatsa S. Bhat

> ---
>  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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