From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v9 09/11] seccomp: introduce writer locking
Date: Wed, 9 Jul 2014 20:59:36 +0200
Message-ID: <20140709185936.GA6043@redhat.com>
References: <1403911380-27787-1-git-send-email-keescook@chromium.org> <1403911380-27787-10-git-send-email-keescook@chromium.org>
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To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>, "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>, Alexei Starovoitov <ast@plumgrid.com>, Andrew Morton <akpm@linux-foundation.org>, Daniel Borkmann <dborkman@redhat.com>, Will Drewry <wad@chromium.org>, Julien Tinnes <jln@chromium.org>, David Drysdale <drysdale@google.com>, linux-api@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-arch@vger.kernel.org, linux-security-module@vger.kernel.org
List-Id: linux-arch.vger.kernel.org

On 06/27, Kees Cook wrote:
>
>  void put_seccomp_filter(struct task_struct *tsk)
>  {
> -	struct seccomp_filter *orig = tsk->seccomp.filter;
> +	struct seccomp_filter *orig = smp_load_acquire(&tsk->seccomp.filter);
>  	/* Clean up single-reference branches iteratively. */
>  	while (orig && atomic_dec_and_test(&orig->usage)) {

And this smp_load_acquire() looks unnecessary. atomic_dec_and_test()
is a barrier.

Oleg.

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Wed, 9 Jul 2014 20:59:36 +0200
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v9 09/11] seccomp: introduce writer locking
Message-ID: <20140709185936.GA6043@redhat.com>
References: <1403911380-27787-1-git-send-email-keescook@chromium.org> <1403911380-27787-10-git-send-email-keescook@chromium.org>
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To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>, "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>, Alexei Starovoitov <ast@plumgrid.com>, Andrew Morton <akpm@linux-foundation.org>, Daniel Borkmann <dborkman@redhat.com>, Will Drewry <wad@chromium.org>, Julien Tinnes <jln@chromium.org>, David Drysdale <drysdale@google.com>, linux-api@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-arch@vger.kernel.org, linux-security-module@vger.kernel.org
Message-ID: <20140709185936.71TfAjo4NdN-_K0e8rDt745BdN2P4NTOdMMjDEvWloo@z>

On 06/27, Kees Cook wrote:
>
>  void put_seccomp_filter(struct task_struct *tsk)
>  {
> -	struct seccomp_filter *orig = tsk->seccomp.filter;
> +	struct seccomp_filter *orig = smp_load_acquire(&tsk->seccomp.filter);
>  	/* Clean up single-reference branches iteratively. */
>  	while (orig && atomic_dec_and_test(&orig->usage)) {

And this smp_load_acquire() looks unnecessary. atomic_dec_and_test()
is a barrier.

Oleg.