From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755513AbcKOPFf (ORCPT ); Tue, 15 Nov 2016 10:05:35 -0500 Received: from mx2.suse.de ([195.135.220.15]:57190 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751088AbcKOPFe (ORCPT ); Tue, 15 Nov 2016 10:05:34 -0500 Date: Tue, 15 Nov 2016 16:05:31 +0100 From: Johannes Thumshirn To: Bart Van Assche Cc: "jejb@linux.vnet.ibm.com" , "hch@infradead.org" , "linux-kernel@vger.kernel.org" , "hare@suse.de" , "martin.petersen@oracle.com" , "linux-scsi@vger.kernel.org" , "arnd@arndb.de" Subject: Re: [PATCH] libfc: fix seconds_since_last_reset miscalculation Message-ID: <20161115150531.73jvxfclzzbtpfal@linux-x5ow.site> References: <1478594694-98847-1-git-send-email-jthumshirn@suse.de> <20161115091840.7cldqui4dpi7nrz5@linux-x5ow.site> <1479221415.3426.3.camel@sandisk.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1479221415.3426.3.camel@sandisk.com> User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 15, 2016 at 02:50:17PM +0000, Bart Van Assche wrote: > On Tue, 2016-11-15 at 10:18 +0100, Johannes Thumshirn wrote: > > On Tue, Nov 08, 2016 at 03:04:43PM +0000, Bart Van Assche wrote: > > > I think the above code will miscalculate seconds_since_last_reset > > > if  > > > 'jiffies' wraps around after an lport has been created and before  > > > seconds_since_last_reset is computed. Shouldn't > > > seconds_since_last_reset  > > > be computed as follows? > > > > > > fc_stats->seconds_since_last_reset = (jiffies - boot_time) / > > > HZ; > > > > But what happens when jiffies - boot_time becomes negative? Then we > > reintroduce the bug again and have 'fcoeadm -s' show weird values. > > Hello Johannes, > > If your concern is about 'jiffies' wrapping around on 32-bit systems > then you should use get_jiffies_64(). get_jiffies_64() - boot_time > can't become negative. It namely takes several million years before a > 64-bit HZ counter wraps around. You're right. I'll respin using get_jiffies_64() and resent once it is tested. Byte, Johannes -- Johannes Thumshirn Storage jthumshirn@suse.de +49 911 74053 689 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850