Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752595AbbBSRAv (ORCPT ); Thu, 19 Feb 2015 12:00:51 -0500 Received: from cantor2.suse.de ([195.135.220.15]:35075 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbbBSRAu (ORCPT ); Thu, 19 Feb 2015 12:00:50 -0500 Date: Thu, 19 Feb 2015 18:00:48 +0100 From: Jiri Bohac To: Prarit Bhargava Cc: linux-kernel@vger.kernel.org, John Stultz , Thomas Gleixner , Miroslav Lichvar , Peter Zijlstra Subject: Re: [PATCH] time, ntp: Do not update time_state in middle of leap second [v3] Message-ID: <20150219170048.GB25948@midget.suse.cz> References: <1423749499-18520-1-git-send-email-prarit@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1423749499-18520-1-git-send-email-prarit@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2148 Lines: 60 Hi, I'm trying to understand what exactly is going on here... On Thu, Feb 12, 2015 at 08:58:19AM -0500, Prarit Bhargava wrote: > The test did the following in userspace: > > tx.modes = ADJ_STATUS; > tx.status = STA_INS; > > /* send leap second request */ > ret = adjtimex(&tx); > > /* Check adjtimex output every half second */ > now = tx.time.tv_sec; > while (now < next_leap+2) { > char buf[26]; > ret = adjtimex(&tx); > > ctime_r(&tx.time.tv_sec, buf); > buf[strlen(buf)-1] = 0; /*remove trailing\n */ > > printf("%s + %6ld us\t%s\n", > buf, > tx.time.tv_usec, > time_state_str(ret)); > now = tx.time.tv_sec; > /* Sleep for another half second */ > ts.tv_sec = 0; > ts.tv_nsec = NSEC_PER_SEC/2; > clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL); > } > > After some investigation it was noted that the test contained a small error: > the test does not reinitialize tx.status and reissues the STA_INS every > 1/2 second. Prarit, can you explain who sets the STA_PLL flag, so that process_adj_status() detects a STA_PLL->!STA_PLL transition and goes to the branch that sets time_state = TIME_OK? Is that ntpd running in parallel with your test program? If that is the case, you would eventually end up oscilating between the the TIME_INS and TIME_OK states anyway, even with your patch. ntpd will clear the STA_INS flag after midnight, the state machine will transition from TIME_WAIT to TIME_OK and your test program will set STA_INS again (fighting with ntpd which will clear the flag from time to time) ... right? Thanks, -- Jiri Bohac SUSE Labs, SUSE CZ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/