Date: Fri, 11 Jan 2008 21:32:15 +0100 (CET) From: "Oliver B. Warzecha" <obw@amarok.ping.de> To: FreeBSD-gnats-submit@FreeBSD.org Subject: i386/119574: 7.0-RC1 times out in calibrate_clocks() Message-ID: <200801112032.m0BKWFXg001186@karnevil9.amarok.ping.de> Resent-Message-ID: <200801112110.m0BLA2ER097596@freefall.freebsd.org>
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>Number: 119574
>Category: i386
>Synopsis: 7.0-RC1 times out in calibrate_clocks()
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-i386
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Jan 11 21:10:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator: Oliver B. Warzecha <obw@amarok.ping.de>
>Release: FreeBSD 7.0-RC1 i386
>Organization:
private
>Environment:
System: FreeBSD karnevil9.amarok.ping.de 7.0-RC1
GENERIC kernel from CD and self compiled
hint.acpi.0.disabled="1" added to /boot/device.hints
>Description:
The 7.0-RC1 GENERIC kernel fails to recognize that the seconds counter
changes during the loops in calibrate_clocks() in sys/i386/isa/clocks.c
The same machine passes this routine quickly with 6.2-RELEASE-p8. It
is a 200 MHz AMD K6 on an ASUS P55T2P4S board.
Through generous use of debugging printf()'s while searching, I could
limit the possible causes to this lines:
timeout = 100000000;
/* Read the mc146818A seconds counter. */
for (;;) {
if (!(rtcin(RTC_STATUSA) & RTCSA_TUP)) {
sec = rtcin(RTC_SEC);
break;
}
if (--timeout == 0)
goto fail;
}
// printf("seconds counter read ... \n");
/* Wait for the mC146818A seconds counter to change. */
start_sec = sec;
for (;;) {
if (!(rtcin(RTC_STATUSA) & RTCSA_TUP)) {
sec = rtcin(RTC_SEC);
if (sec != start_sec)
break;
}
if (--timeout == 0)
goto fail;
}
// printf("seconds counter changed ... \n");
(my debugging printf()s commented out with C++ comments)
The first output "seconds counter read" gets printed very fast.
After that the machine counts back from 0 to 0 and after some minutes
he falls out of the loop and "seconds counter changed" gets never
printed.
As I noticed that rtcin() was reworked during the change to 7.0,
(http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/i386/isa/clock.c.diff?r1=1.222.2.2;r2=1.239.2.1;f=h)
it occurred to me that perhaps there might be some condition
in the new code.
As I said, on a 6.2-RELEASE-p8 kernel it all goes smoothly, I just
checked with boot -v:
Calibrating clock(s) ... i8254 clock: 1193296 Hz
CLK_USE_I8254_CALIBRATION not specified - using default frequency
Timecounter "i8254" frequency 1193182 Hz quality 0
It does *not* say "failed, using default i8254 clock [...]" which
would indicate the "fault" label.
>How-To-Repeat:
boot 7.0-RC1 GENERIC on the hardware mentioned above (tested it on
one other machine with "no ACPI" from the the boot CD, but that
one booted fast and recognized the timer)
>Fix:
One possible workaround would be to reset the timeout variable
to a more sane value, for the first loop it gets set to
100000000. But then this loop seems to work okay, so I have
no idea what a sane value would be. At least it would fail
fast.
For a complete fix I have no idea than to revert to the 6.2-code.
But I think, this may be out of the question.
>Release-Note:
>Audit-Trail:
>Unformatted:
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