From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ren Qiaowei Date: Mon, 27 Oct 2014 03:20:35 +0000 Subject: Re: [PATCH v9 05/12] x86, mpx: on-demand kernel allocation of bounds tables Message-Id: <544DBA03.1010709@intel.com> List-Id: References: <1413088915-13428-1-git-send-email-qiaowei.ren@intel.com> <1413088915-13428-6-git-send-email-qiaowei.ren@intel.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Thomas Gleixner 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 10/24/2014 08:08 PM, Thomas Gleixner wrote: > 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. > Well, we will address it. Thanks, Qiaowei From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 27 Oct 2014 04:23:46 +0100 (CET) Received: from mga14.intel.com ([192.55.52.115]:7766 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S27010918AbaJ0DXpXvl9Y (ORCPT ); Mon, 27 Oct 2014 04:23:45 +0100 Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP; 26 Oct 2014 20:17:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; d="scan'208";a="406471914" Received: from rqw-ubuntu.sh.intel.com (HELO [10.239.37.69]) ([10.239.37.69]) by FMSMGA003.fm.intel.com with ESMTP; 26 Oct 2014 20:15:40 -0700 Message-ID: <544DBA03.1010709@intel.com> Date: Mon, 27 Oct 2014 11:20:35 +0800 From: Ren Qiaowei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Thomas Gleixner 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 References: <1413088915-13428-1-git-send-email-qiaowei.ren@intel.com> <1413088915-13428-6-git-send-email-qiaowei.ren@intel.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 43573 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: qiaowei.ren@intel.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On 10/24/2014 08:08 PM, Thomas Gleixner wrote: > 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. > Well, we will address it. Thanks, Qiaowei From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f180.google.com (mail-pd0-f180.google.com [209.85.192.180]) by kanga.kvack.org (Postfix) with ESMTP id 012946B0070 for ; Sun, 26 Oct 2014 23:23:39 -0400 (EDT) Received: by mail-pd0-f180.google.com with SMTP id ft15so2851903pdb.11 for ; Sun, 26 Oct 2014 20:23:39 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id hs2si9363422pdb.222.2014.10.26.20.23.38 for ; Sun, 26 Oct 2014 20:23:38 -0700 (PDT) Message-ID: <544DBA03.1010709@intel.com> Date: Mon, 27 Oct 2014 11:20:35 +0800 From: Ren Qiaowei MIME-Version: 1.0 Subject: Re: [PATCH v9 05/12] x86, mpx: on-demand kernel allocation of bounds tables References: <1413088915-13428-1-git-send-email-qiaowei.ren@intel.com> <1413088915-13428-6-git-send-email-qiaowei.ren@intel.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner 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 10/24/2014 08:08 PM, Thomas Gleixner wrote: > 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. > Well, we will address it. Thanks, Qiaowei -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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