linux-kernel - Re: [PATCH 2/2] ipc namespaces: implement support for posix msqueues

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Message-Id: <1229540099.17206.426.camel@nimitz>
Date:	Wed, 17 Dec 2008 10:54:59 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: [PATCH 2/2] ipc namespaces: implement support for posix
	msqueues

On Wed, 2008-12-17 at 11:55 -0600, Serge E. Hallyn wrote:
> -void free_ipc_ns(struct kref *kref)
> +void put_ipc_ns(struct ipc_namespace *ns)
>  {
> -       struct ipc_namespace *ns;
> +       if (ns && atomic_dec_and_lock(&ns->count, &mq_lock)) {
> +               mq_clear_sbinfo(ns);
> +               spin_unlock(&mq_lock);
> +               mq_put_mnt(ns);
> +               free_ipc_ns(ns);
> +       }
> +}

OK, I see now why you wanted to remove the kref and add an atomic_t.
That's probably worth a sentence in the patch description.

I know that atomic_dec_and_lock() can be a nice logical thing to do, but
is it necessary here?  Basically, is there something that happens under
mq_lock that can re-raise the ns->count?

-- Dave

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