Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751032AbVJTKFP (ORCPT ); Thu, 20 Oct 2005 06:05:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751045AbVJTKFP (ORCPT ); Thu, 20 Oct 2005 06:05:15 -0400 Received: from ms-smtp-01.nyroc.rr.com ([24.24.2.55]:64763 "EHLO ms-smtp-01.nyroc.rr.com") by vger.kernel.org with ESMTP id S1751032AbVJTKFO (ORCPT ); Thu, 20 Oct 2005 06:05:14 -0400 Date: Thu, 20 Oct 2005 06:05:01 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@localhost.localdomain To: Ingo Molnar cc: john stultz , tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: Ktimer / -rt9 (+custom) monotonic_clock going backwards. In-Reply-To: Message-ID: References: <1129734626.19559.275.camel@tglx.tec.linutronix.de> <1129747172.27168.149.camel@cog.beaverton.ibm.com> <20051020073416.GA28581@elte.hu> <20051020080107.GA31342@elte.hu> <20051020085955.GB2903@elte.hu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1481 Lines: 59 On Thu, 20 Oct 2005, Steven Rostedt wrote: > > On Thu, 20 Oct 2005, Ingo Molnar wrote: > > > > > * Steven Rostedt wrote: > > > > > static inline nsec_t __get_nsec_offset(void) > > > { > > > cycle_t cycle_now, cycle_delta; > > > nsec_t ns_offset; > > > > > > /* read clocksource */ > > > cycle_now = read_clocksource(clock); > > > > > > /* calculate the delta since the last timeofday_periodic_hook */ > > > cycle_delta = (cycle_now - cycle_last) & clock->mask; > > > > > > /* convert to nanoseconds */ > > > ns_offset = cyc2ns(clock, ntp_adj, cycle_delta); > > > > > > /* Special case for jiffies tick/offset based systems > > > * add arch specific offset > > > */ > > > ns_offset += arch_getoffset(); > > > > > > return ns_offset; > > > } > > > > > > cycle_now is 32 bits. If the clocksource overflows (which it can in > > > 30 seconds) the cyclec_delta will be wrong. > > > > isnt cycle_t 64 bits? > > > > Not anymore. > > include/linux/time.h: > > /* timeofday base types */ > typedef s64 nsec_t; > typedef unsigned long cycle_t; > FYI, I just switched cycle_t to u64 and hackbench no longer makes the time go backwards. John, would this cause any problems to keep cycle_t at s64? -- Steve - 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/