2014-04-06 17:36:30

by Ming Lei

Subject: [PATCH] arm, kvm: fix double lock on cpu_add_remove_lock

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 <[email protected]>
Cc: Christoffer Dall <[email protected]>
Cc: Srivatsa S. Bhat <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
---
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;
--
1.7.9.5

2014-04-07 06:45:08

by Srivatsa S. Bhat

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 <[email protected]>
> Cc: Christoffer Dall <[email protected]>
> Cc: Srivatsa S. Bhat <[email protected]>
> Cc: Rafael J. Wysocki <[email protected]>
> Signed-off-by: Ming Lei <[email protected]>

Sorry for missing that, and thank you for the fix!

Reviewed-by: Srivatsa S. Bhat <[email protected]>

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;
>

2014-04-08 11:17:58

by Rafael J. Wysocki

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 <[email protected]>
> > Cc: Christoffer Dall <[email protected]>
> > Cc: Srivatsa S. Bhat <[email protected]>
> > Cc: Rafael J. Wysocki <[email protected]>
> > Signed-off-by: Ming Lei <[email protected]>
>
> Sorry for missing that, and thank you for the fix!
>
> Reviewed-by: Srivatsa S. Bhat <[email protected]>

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.