linux-kernel - Re: [PATCH] x86: KVM, fix lock imbalance

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Date:	Wed, 7 Jul 2010 15:05:45 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	avi@...hat.com, linux-kernel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Gleb Natapov <gleb@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Gregory Haskins <ghaskins@...ell.com>, kvm@...r.kernel.org
Subject: Re: [PATCH] x86: KVM, fix lock imbalance


* Jiri Slaby <jirislaby@...il.com> wrote:

> Stanse found that there is an omitted unlock in kvm_create_pit in one fail
> path. Add proper unlock there.
> 
> Signed-off-by: Jiri Slaby <jirislaby@...il.com>
> Cc: Avi Kivity <avi@...hat.com>
> Cc: Marcelo Tosatti <mtosatti@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: Gleb Natapov <gleb@...hat.com>
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: Gregory Haskins <ghaskins@...ell.com>
> Cc: kvm@...r.kernel.org
> ---
>  arch/x86/kvm/i8254.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 467cc47..70db4d4 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -696,6 +696,7 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
>  
>  	pit->wq = create_singlethread_workqueue("kvm-pit-wq");
>  	if (!pit->wq) {
> +		mutex_unlock(&pit->pit_state.lock);
>  		kfree(pit);
>  		return NULL;
>  	}

A cleanliness comment: why is that tear-down/dealloc sequence open-coded? It 
should be at the end of the function, with goto labels, like we do it in 
similar cases.

Thanks,

	Ingo
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