From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out203-205-251-82.mail.qq.com (out203-205-251-82.mail.qq.com [203.205.251.82]) (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 EF5231C2D for ; Thu, 7 Mar 2024 00:51:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=203.205.251.82 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709772712; cv=none; b=ntOTjkNC/0GcIDtGerWSagpXOeYJLEo8wAjCqtATTWqSwmfWRDuLr7aYEnlFa9uxJ1nb45CvS0SawJ3kkFZmsKJ/EPOvdIGuIPj45XJfkAftFb6RnzdB5Wup9yq1rBV7BL993/AYKHZEVyqGb1/gC3cPsPs7MK/pTFitktKg7jM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709772712; c=relaxed/simple; bh=98Yqbd2Wkh4I4wi98kaFvAWL9EqEsWOXtRJLenp0Yfw=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QLEzd+G2RID0DxUMANJU3Bg8Dww3mV9cAnGdZFAv+k/PIF4LlUSWZx6LdSZUNqgFawtEctg0YFYGUy83+boCkUGucCdL1obX96J5kquYldsPf2pgRjiHmxd8m2ct0lqetvWiY3j4hEISamwAGisdDThKVVVdOJ9WRlIm+ZnT1qo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=foxmail.com; spf=pass smtp.mailfrom=foxmail.com; dkim=pass (1024-bit key) header.d=foxmail.com header.i=@foxmail.com header.b=IyY8G5K9; arc=none smtp.client-ip=203.205.251.82 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=foxmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=foxmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=foxmail.com header.i=@foxmail.com header.b="IyY8G5K9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foxmail.com; s=s201512; t=1709772400; bh=uRsiBh41eR5/aRW2EM611Fer1G2Jrc6sG+c+CAIrrDo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=IyY8G5K9ewWfXTINyYLOONbeXUan9uwexYwk2F66tvzheJC8W6S2QMo6BDsX6VCVb 9tsmcCNR9BALMGR8+PAOI/UWaRz0YCz11n+gT/yafPMVhUeYdJKcZzBK8fhuZnjZSx WXdebWNjK1yfrvWtJLx9Km/9cRiJvIMe4xpq/RdM= Received: from localhost ([2409:895a:da03:3c6e:2868:6191:8e02:86e5]) by newxmesmtplogicsvrszc5-0.qq.com (NewEsmtp) with SMTP id BA622026; Thu, 07 Mar 2024 08:46:38 +0800 X-QQ-mid: xmsmtpt1709772398tvx0jauuw Message-ID: X-QQ-XMAILINFO: NDgMZBR9sMmaLSbUu2PkHB1cleGyXUBndN7HqWcwDHwRCtrR3bjcEkMpHS3tsb e7LpuThtPwtuH5Ndw2Jkj7Z147BgMAZ0NJ9MlHgSMeaPJOn5a6hbi8w1PhTSPouK0Q3I+xYee7Hp dI4N8KJqYqHJeIridWclluNar42fQda1Ko+kCjp33MXHAreM6QUs/PMRkCCiqk9RM+6mNzXYqDaQ 6mYpycTjPO0e0ZVbLs9iuLYLDA9DbyYIl1911e1kP1fFxR895e+DxqE1g1FcLNeVOa77ZxyphPe0 qJafQ29hecX55aHyLlZHXjjr/GUm1JEWMMU6RqjynIVk2W5YMJv7Dg8UB2tamTak1quX0kdbLn/m NWjkWN7MQyX08YM+EEmYFw95/Lco3PwCcZZDZtQmBpSGAJx1Y9HN+rj5XuMtvnsDKiHlqBKn+J4I 27Yzj5pCPPZxzItRZ9EL8cz/SM0+i5JVmnP1Luwjc8QWFyl6OXwMVmLam6ncitkUipaOqwA8GUfe 6yLtQMUqYbwb662vTRPuLXNNvMHYulMJVWKWpMob1d55/Tq3sK9Cx16SfVtd3kAmCd9ftkUgL6s2 +5qZCAbGDlvaG+TXupv8SNVCFBu9Fchu4iS2/Y2rN9ghOsA0t5Nn7SIeEw0jPgf0y23OuCp/MqDB i/zfRLGEGo046pq1bVDQVtIEkSGHVWjx61peOONFvzku3E0y6XdXmfO3KXHrKjTCQcdUC0B3jEDb wA3Snq12KgpyGH1x5sHjitFjCQk51nLnACrpjN3r8eG2ndHu1ueD1paBnSde6JGnl7X/A/+KL4jW 4x2AF3gErj3+1jKKBRafr1fkPIm84xoXgzyNRQ9C0WPo+cJ7QBupWzJsi7zFfVRIUd1HrOqrzH6Q GP4ACDPr5uQS702M8DARHG9H+ZqlmQIAHJoekfu4Ard6b87VKz9raJmJ2wXhMeUIdkIbu+8ZF6jy apdIyKB/em9Jm9d9RGXQ== X-QQ-XMRINFO: NS+P29fieYNw95Bth2bWPxk= Sender: kenneth-lee-2012@foxmail.com Date: Thu, 7 Mar 2024 08:45:32 +0800 From: Kenneth-Lee-2012@foxmail.com To: Andrea Parri Cc: Alan Stern , linux-kernel@vger.kernel.org, paulmck@kernel.org Subject: Re: Question about PB rule of LKMM X-OQ-MSGID: <20240307004532.pvatpxz4zjg6fyja@kllt01> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Mar 06, 2024 at 08:24:42PM +0100, Andrea Parri wrote: > Date: Wed, 6 Mar 2024 20:24:42 +0100 > From: Andrea Parri > To: Alan Stern > Cc: Kenneth-Lee-2012@foxmail.com, linux-kernel@vger.kernel.org, > paulmck@kernel.org > Subject: Re: Question about PB rule of LKMM > > > Later on, the file includes this paragraph, which answers the question > > you were asking: > > > > --------------------------------------------------------------------- > > The existence of a pb link from E to F implies that E must execute > > before F. To see why, suppose that F executed first. Then W would > > have propagated to E's CPU before E executed. If E was a store, the > > memory subsystem would then be forced to make E come after W in the > > coherence order, contradicting the fact that E ->coe W. If E was a > > load, the memory subsystem would then be forced to satisfy E's read > > request with the value stored by W or an even later store, > > contradicting the fact that E ->fre W. > > --------------------------------------------------------------------- > > TBF, that just explains (not F ->xb E), or I guess that was the origin > of the question. Yes. I thought a link was just an unconditional pattern for the programmer to match the actual code so the other categories (of links in the same acyclic rule) cannot route back. But now I understand the ->xx* relation in the begining or end of the link can also add xx to the rule. > > Andrea -- -Kenneth Lee