From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by kanga.kvack.org (Postfix) with ESMTP id 1E2646B0069 for ; Fri, 24 Oct 2014 08:08:26 -0400 (EDT) Received: by mail-wi0-f178.google.com with SMTP id q5so1062207wiv.5 for ; Fri, 24 Oct 2014 05:08:25 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id uw9si5115780wjc.37.2014.10.24.05.08.23 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 24 Oct 2014 05:08:24 -0700 (PDT) Date: Fri, 24 Oct 2014 14:08:11 +0200 (CEST) From: Thomas Gleixner 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: 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 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org