Date: Sun, 17 Feb 2002 21:55:42 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Bruce Evans <bde@zeta.org.au>, freebsd-current@FreeBSD.ORG Subject: Re: 'microuptime() went backwards ...' using ACPI timer. Shouldn't that be impossible? Message-ID: <6616.1013979342@critter.freebsd.dk> In-Reply-To: Your message of "Sun, 17 Feb 2002 12:25:38 PST." <200202172025.g1HKPc589840@apollo.backplane.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Matt, Easy now, there is more depth to it than that... I have promised myself to get the timecounter paper written and I'll probably present it at BSDcon-euro-2002 in Amsterdam if they want to listen to me. For now, lets concentrate on the PIIX hardware because that's where the problem seems to be... Poul-Henning In message <200202172025.g1HKPc589840@apollo.backplane.com>, Matthew Dillon wri tes: > Ok, I've looked at the code more carefully and I understand how this > works now. However, it is not enough in an SMP environment. You > need a generation count in the timecounter structure and you also need > a synchronization point when you switch time counters or a process > running on a different cpu may wind up using a time counter that is being > actively updated. > > I'm experimenting with your patch now. I'll send email when I have > some test results. > > -Matt > >: >:I just wrote the following fix for some of the overflow problems. >: >:%%% >:Index: kern_tc.c >:=================================================================== >:RCS file: /home/ncvs/src/sys/kern/kern_tc.c,v >:retrieving revision 1.113 >:diff -c -2 -r1.113 kern_tc.c >:... > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-current" in the body of the message > -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?6616.1013979342>