In message <[EMAIL PROTECTED]>, Bruce Evans writes:

>> This occurs both with and without the gettimeofday Giant-removal patch, so
>> I am fairly sure it has nothing to do with any of my current work.  This is
>> running -current on a DELL2550 (2xCPUs), compiled with the SMP option.

The Gian removal doesn't come anywhere near this.

>The fact that the timecounter usually goes backwards by about 0.68 seconds
>is probably significant, but I can't quite explain it.

>>     acpi_timer0: <32-bit timer at 3.579545MHz> port 0x808-0x80b on acpi0

        2^32 / 3579545 = 1199.86 seconds.
        2^24 / 3579545 =    4.68 seconds.

So even assuming that ACPI reported a wrong width, four seconds should
still be enough to prevent a wraparound even though we cycle through
the timecounter ring in one second.

>I just wrote the following fix for some of the overflow problems.

It is true that if a process is not running for arbitrary long time
the timecounter may be modified underneat it, and bruce's patch is
actually a pretty elegant solution for that case.  By all means
try it.

I have had one other report of a similar problem, with the added
information that changing to the TSC or i8254 instead of PIXX
made it go away so I am not entirely convinced this is really what
we are looking for in this case.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED]         | 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 [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message

Reply via email to