From owner-freebsd-current Wed Sep 6 3:26: 6 2000 Delivered-To: freebsd-current@freebsd.org Received: from critter.freebsd.dk (flutter.freebsd.dk [212.242.40.147]) by hub.freebsd.org (Postfix) with ESMTP id D65F537B422; Wed, 6 Sep 2000 03:25:56 -0700 (PDT) Received: from critter (localhost [127.0.0.1]) by critter.freebsd.dk (8.11.0/8.9.3) with ESMTP id e86APrN64556; Wed, 6 Sep 2000 12:25:53 +0200 (CEST) (envelope-from phk@critter.freebsd.dk) To: Josef Karthauser Cc: current@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: looking for "microuptime went backwards" victims... In-Reply-To: Your message of "Wed, 06 Sep 2000 11:17:13 BST." <20000906111713.E1081@pavilion.net> Date: Wed, 06 Sep 2000 12:25:53 +0200 Message-ID: <64554.968235953@critter> From: Poul-Henning Kamp Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Uhm, that is from the sound driver, not from the timecounter... Poul-Henning In message <20000906111713.E1081@pavilion.net>, Josef Karthauser writes: >I got this last night running 'mtv' on a system with heavy disk I/O. >The errors were: > >Sep 5 23:12:14 genius /kernel: pcm0: hwptr went backwards 8208 -> 8192 >Sep 5 23:12:47 genius /kernel: pcm0: hwptr went backwards 8420 -> 8192 >Sep 5 23:12:57 genius /kernel: pcm0: hwptr went backwards 8212 -> 8192 >Sep 5 23:13:04 genius /kernel: pcm0: hwptr went backwards 8196 -> 8192 >Sep 5 23:13:21 genius /kernel: pcm0: hwptr went backwards 8208 -> 8192 > >etc. > >Joe > >FreeBSD genius.systems.pavilion.net 5.0-CURRENT FreeBSD 5.0-CURRENT #11: Tue Sep 5 12:45:45 BST 2000 joe@genius.systems.pavilion.net:/usr/obj/usr/src/sys/GENIUS i386 > >On Mon, Sep 04, 2000 at 06:41:14PM +0200, Poul-Henning Kamp wrote: >> >> I'm looking for the remaining victims of the dreaded "microuptime >> went backwards" message. >> >> If you can reliably reproduce the problem, please contact me, so >> we can arrange for some very detailed tracing to try to find out >> what exactly is going on. I have not been able to trigger the >> problem in my lab in a long time. >> >> If you see the message only occationally, please try the attached >> patch and let me know if this changes the picture. The patch is >> not meant as a fix, but it might reduce the impact of this condition >> considerably when it happens. Basically by reducing the width of >> the timecounter the magnitude of the hit we take if the timecounter >> goes backwards is reduced from about an hour to approx 110msec. >> >> Reducing the width to less than 17 bits starts to run the risk of >> ambiguity due to clock rollover. >> >> This patch may not be safe with PCAUDIO. >> >> Poul-Henning >> >> Index: clock.c >> =================================================================== >> RCS file: /home/ncvs/src/sys/i386/isa/clock.c,v >> retrieving revision 1.155 >> diff -u -r1.155 clock.c >> --- clock.c 2000/07/30 21:05:22 1.155 >> +++ clock.c 2000/09/04 16:34:16 >> @@ -194,7 +194,7 @@ >> static struct timecounter i8254_timecounter = { >> i8254_get_timecount, /* get_timecount */ >> 0, /* no poll_pps */ >> - ~0u, /* counter_mask */ >> + 0x1ffff, /* counter_mask */ >> 0, /* frequency */ >> "i8254" /* name */ >> }; >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> phk@FreeBSD.ORG | TCP/IP since RFC 956 >> FreeBSD coreteam member | 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-hackers" in the body of the message > >-- >Josef Karthauser FreeBSD: How many times have you booted today? >Technical Manager Viagra for your server (http://www.uk.freebsd.org) >Pavilion Internet plc. [joe@pavilion.net, joe@uk.freebsd.org, joe@tao.org.uk] > -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD coreteam member | 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