From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
Subject: Re: [PATCH] ptrace: add ability to retrieve signals without removing
 from a queue (v2)
Date: Mon, 25 Feb 2013 14:13:43 +0400
Message-ID: <512B3957.1020505@parallels.com>
References: <1361786813-14652-1-git-send-email-avagin@openvz.org>
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To: Andrey Vagin <avagin-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, criu-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Roland McGrath <roland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Dave Jones <davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, "Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Pedro Alves <palves-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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> +	for (i = 0; i < arg.nr; i++) {
> +		off = arg.off + i;
> +
> +		spin_lock_irq(&child->sighand->siglock);
> +		list_for_each_entry(q, &pending->list, list) {
> +			if (!off--) {
> +				copy_siginfo(&info, &q->info);
> +				break;
> +			}
> +		}
> +		spin_unlock_irq(&child->sighand->siglock);

What's the point of arg.nr if you for every single siginfo drop the lock
and perform linear search anyway?

Thanks,
Pavel

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Mon, 25 Feb 2013 14:13:43 +0400
From: Pavel Emelyanov <xemul@parallels.com>
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To: Andrey Vagin <avagin@openvz.org>
CC: linux-kernel@vger.kernel.org, criu@openvz.org, linux-api@vger.kernel.org,
        Roland McGrath <roland@redhat.com>, Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        David Howells <dhowells@redhat.com>, Dave Jones <davej@redhat.com>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pedro Alves <palves@redhat.com>
Subject: Re: [PATCH] ptrace: add ability to retrieve signals without removing
 from a queue (v2)
References: <1361786813-14652-1-git-send-email-avagin@openvz.org>
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> +	for (i = 0; i < arg.nr; i++) {
> +		off = arg.off + i;
> +
> +		spin_lock_irq(&child->sighand->siglock);
> +		list_for_each_entry(q, &pending->list, list) {
> +			if (!off--) {
> +				copy_siginfo(&info, &q->info);
> +				break;
> +			}
> +		}
> +		spin_unlock_irq(&child->sighand->siglock);

What's the point of arg.nr if you for every single siginfo drop the lock
and perform linear search anyway?

Thanks,
Pavel