From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B6D3183098; Mon, 30 Sep 2024 12:06:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=14.137.139.23 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727697996; cv=none; b=ODs5wqtqsRILEPrHIN/kYrmKBBQaw69zjCb9bCt10TRO/v/cyggYD+L6HTlEs7iFLN5mRlSCKiHuXIYfxsx1Mjf45kteq9A7TZUo1kFGvbgkCqcVJ7Av2fGnadruAVqxf5LwmMCFLBU+ikttle5JIl6ALTjrgbKeww8YlfAflUQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727697996; c=relaxed/simple; bh=3uZm5F8HdZrf1jSahO+r1HjBDvuoNtC9/fe/8536mZc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fhuZrUNSwpnj1nB0UoaZJ9HQOlWRvg5Yau5kDQBHCNc5/adwoLTLNzmGgVEzHnh+XxLO/q61GoSIcWFv9wDqC0ARHy9H8/4RYDJcZrCgGU0RcTERdbPrW85TDsI1Qz91frLTYILfJw+/jx0vGRqlx9vZc8Mnz5VZTS+fVDCCmWs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=14.137.139.23 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.18.186.51]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4XHK6Q326Pz9v7Hy; Mon, 30 Sep 2024 19:46:38 +0800 (CST) Received: from mail02.huawei.com (unknown [7.182.16.27]) by mail.maildlp.com (Postfix) with ESMTP id E46EC14059D; Mon, 30 Sep 2024 20:06:30 +0800 (CST) Received: from [10.81.209.28] (unknown [10.81.209.28]) by APP2 (Coremail) with SMTP id GxC2BwBXBsc2lPpmpbvyAQ--.6803S2; Mon, 30 Sep 2024 13:06:30 +0100 (CET) Message-ID: <50bd6ecb-c8e3-4043-9040-b2b4ee71fc02@huaweicloud.com> Date: Mon, 30 Sep 2024 14:06:12 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] compiler.h: Introduce ptr_eq() to preserve address dependency To: paulmck@kernel.org Cc: Alan Stern , Mathieu Desnoyers , Linus Torvalds , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Sebastian Andrzej Siewior , Will Deacon , Peter Zijlstra , Boqun Feng , John Stultz , Neeraj Upadhyay , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Gary Guo , rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev References: <20240928135128.991110-1-mathieu.desnoyers@efficios.com> <20240928135128.991110-2-mathieu.desnoyers@efficios.com> <02c63e79-ec8c-4d6a-9fcf-75f0e67ea242@rowland.harvard.edu> <2091628c-2d96-4492-99d9-0f6a61b08d1d@efficios.com> <25344f33-b8dc-43fb-a394-529eff03d979@rowland.harvard.edu> <973ae617-96a8-456a-a805-af3d61270125@paulmck-laptop> From: Jonas Oberhauser In-Reply-To: <973ae617-96a8-456a-a805-af3d61270125@paulmck-laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CM-TRANSID:GxC2BwBXBsc2lPpmpbvyAQ--.6803S2 X-Coremail-Antispam: 1UD129KBjDUn29KB7ZKAUJUUUUU529EdanIXcx71UUUUU7v73 VFW2AGmfu7bjvjm3AaLaJ3UjIYCTnIWjp_UUUY37kC6x804xWl14x267AKxVWrJVCq3wAF c2x0x2IEx4CE42xK8VAvwI8IcIk0rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII 0Yj41l84x0c7CEw4AK67xGY2AK021l84ACjcxK6xIIjxv20xvE14v26r1j6r1xM28EF7xv wVC0I7IYx2IY6xkF7I0E14v26r4j6F4UM28EF7xvwVC2z280aVAFwI0_Gr0_Cr1l84ACjc xK6I8E87Iv6xkF7I0E14v26r4UJVWxJr1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG 64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r 1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwACI402YVCY1x02628vn2kI c2xKxwCF04k20xvY0x0EwIxGrwCF54CYxVCY1x0262kKe7AKxVW8ZVWrXwCFx2IqxVCFs4 IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1r MI8E67AF67kF1VAFwI0_GFv_WrylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJV WUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j 6r1xMIIF0xvEx4A2jsIE14v26r4j6F4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr1j6F4UJb IYCTnIWIevJa73UjIFyTuYvjxUFYFCUUUUU X-CM-SenderInfo: 5mrqt2oorev25kdx2v3u6k3tpzhluzxrxghudrp/ Am 9/30/2024 um 1:04 PM schrieb Paul E. McKenney: > On Mon, Sep 30, 2024 at 11:42:11AM +0200, Jonas Oberhauser wrote: >> >> >> I also currently don't see any major difference between the constant and >> register case. The point is that the address is known before loading into b, >> and hence the compiler + hardware can speculatively load *b before loading >> into b. > > In theory, true. In practice, in the register case, you need a little > more bad luck for the compiler to be able to exploit your mistake. If there's one thing I've never run out of, then it is bad luck with technology. jonas