Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756509AbaJXMI1 (ORCPT ); Fri, 24 Oct 2014 08:08:27 -0400 Received: from www.linutronix.de ([62.245.132.108]:47375 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756203AbaJXMIZ (ORCPT ); Fri, 24 Oct 2014 08:08:25 -0400 Date: Fri, 24 Oct 2014 14:08:11 +0200 (CEST) From: Thomas Gleixner To: Qiaowei Ren cc: "H. Peter Anvin" , Ingo Molnar , Dave Hansen , x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@linux-mips.org Subject: Re: [PATCH v9 05/12] x86, mpx: on-demand kernel allocation of bounds tables In-Reply-To: <1413088915-13428-6-git-send-email-qiaowei.ren@intel.com> Message-ID: References: <1413088915-13428-1-git-send-email-qiaowei.ren@intel.com> <1413088915-13428-6-git-send-email-qiaowei.ren@intel.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 12 Oct 2014, Qiaowei Ren wrote: > + /* > + * Go poke the address of the new bounds table in to the > + * bounds directory entry out in userspace memory. Note: > + * we may race with another CPU instantiating the same table. > + * In that case the cmpxchg will see an unexpected > + * 'actual_old_val'. > + */ > + ret = user_atomic_cmpxchg_inatomic(&actual_old_val, bd_entry, > + expected_old_val, bt_addr); This is fully preemptible non-atomic context, right? So this wants a proper comment, why using user_atomic_cmpxchg_inatomic() is the right thing to do here. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/