linux-kernel - Re: [PATCH] pidns: remove recursion from free_pid

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Message-ID: <20121006191400.GA24391@redhat.com>
Date:	Sat, 6 Oct 2012 21:14:00 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Vagin <avagin@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, criu@...nvz.org,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] pidns: remove recursion from free_pid_ns (v2)

On 10/06, Andrew Vagin wrote:
>
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -138,11 +138,20 @@ void free_pid_ns(struct kref *kref)
>  
>  	ns = container_of(kref, struct pid_namespace, kref);
>  
> -	parent = ns->parent;
> -	destroy_pid_namespace(ns);
> +	while (1) {
>  
> -	if (parent != NULL)
> -		put_pid_ns(parent);
> +		parent = ns->parent;
> +		destroy_pid_namespace(ns);
> +
> +		if (parent == &init_pid_ns)
> +			break;
> +
> +		/* kref_put cannot be used for avoiding recursion */
> +		if (__kref_put(&parent->kref) == 0)
> +			break;
> +
> +		ns = parent;
> +	}
>  }

Reviewed-by: Oleg Nesterov <oleg@...hat.com>

But, Andrew... please note that this adds the unnecessary empty
line after "while (1)". The coding style police will complain
anyway, so I'd suggest you to send v3 ;)

Oleg.

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