From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757605Ab0ERNwq (ORCPT ); Tue, 18 May 2010 09:52:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37461 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757366Ab0ERNwn (ORCPT ); Tue, 18 May 2010 09:52:43 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20100518133925.GA1353@redhat.com> References: <20100518133925.GA1353@redhat.com> <20100517195414.GA21504@redhat.com> <2996.1274172907@redhat.com> To: Oleg Nesterov Cc: dhowells@redhat.com, Andrew Morton , Andrew Tridgell , Eric Paris , Jakub Jelinek , James Morris , Roland McGrath , Stephen Smalley , linux-kernel@vger.kernel.org Subject: Re: [PATCH] signals: check_kill_permission: don't check creds if same_thread_group() Date: Tue, 18 May 2010 14:50:47 +0100 Message-ID: <25639.1274190647@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov wrote: > Yes, but both current_cred() and same_thread_group(current, t) call > get_current(), and gcc doesn't cache the result because we call > audit_signal_info() in between. Sorry, yes. I was reading get_current() as current_cred() for some reason. However, you are _still_ calling get_current() twice... So that bit of your changelog isn't really correct. In fact, get_current() should be __attribute_const__ since it can't change whilst you're looking at it, except within switch_to(), probably in a piece of assembly code, so gcc should be free to cache it as long as it likes. David