From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e39.co.us.ibm.com (e39.co.us.ibm.com [32.97.110.160]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4B4891A003D for ; Wed, 8 Oct 2014 23:27:23 +1100 (EST) Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 8 Oct 2014 06:27:19 -0600 Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 2F5616E8046 for ; Wed, 8 Oct 2014 08:16:01 -0400 (EDT) Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s98CRGVb44957864 for ; Wed, 8 Oct 2014 12:27:16 GMT Received: from d01av01.pok.ibm.com (localhost [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s98CRGiW014586 for ; Wed, 8 Oct 2014 08:27:16 -0400 Message-ID: <54352DA3.8090509@us.ibm.com> Date: Wed, 08 Oct 2014 07:27:15 -0500 From: Paul Clarke MIME-Version: 1.0 To: Heinz Wrobel , "linuxppc-dev@lists.ozlabs.org" Subject: Re: [PATCH] powerpc: mitigate impact of decrementer reset References: <1412708517-84726-1-git-send-email-pc@us.ibm.com> <54343B54.4060500@us.ibm.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 10/08/2014 12:37 AM, Heinz Wrobel wrote: > what if your tb wraps during the test? Per the Power ISA, Time Base is 64 bits, monotonically increasing, and is writable only in hypervisor state. To my understanding, it is set to zero at boot (although this is not prescribed). Also, as noted by others, the logic is roughly duplicated (with some differences) from the analogous code in __timer_interrupt just above it. I don't see wrapping as a concern. PC