Date: Fri, 21 Aug 1998 10:36:20 +0200 From: Stefan Eggers <seggers@semyam.dinoco.de> To: Brian Feldman <green@unixhelp.org> Cc: seggers@semyam.dinoco.de, freebsd-current@FreeBSD.ORG Subject: Re: 13 months of user time? Message-ID: <199808210836.KAA02477@semyam.dinoco.de> In-Reply-To: Your message of "Thu, 20 Aug 1998 02:08:08 EDT." <Pine.BSF.4.02.9808200203190.24018-100000@zone.syracuse.net>
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> SIGXCPU kill problem could try putting the following in kern/kern_synch.c
> line 638:
I think better not this one as that is a safe way to a panic IMHO. A
version I think does what you intend this to do I add below. It is
untested code I just added while writing the mail.
> if (switchtime.tv_usec < p->p_switchtime.tv_usec ||
> switchtime.tv_sec < p->p_switchtime.tv_sec)
> panic("bogus microuptime twiddling");
>
> And see if we get some nice panics and cores. Is it worth a shot? I've
As far as I can see the timeval in the process structure is a real
timeval and not abused to be something else. So tv_usec contains the
micro seconds part and tv_sec the seconds.
Let's assume that p->p_switchtime.tv_usec contains 999999 now and
p->p_switchtime.tv_sec is 0. Lets suppose the time continues a little
bit and when we reach the if statement switchtime.tv_usec might
contain 0 and switchtime.tv_sec 1. The time didn't go backward but
with the code above causes a panic.
> never gotten a SIGXCPU out of place, so my machine wouldn't be the one to
> test this on.
And I don't think you want the test this way, anyway. ;-)
One has first to calculate a 64 bit integer from the seconds and micro
seconds and then compare the two resulting numbers. With that it
could actually detect switchtime going backward.
Something like this:
int64_t time1, time2;
[...]
time1 = switchtime.tv_usec + switchtime.tv_sec * (int64_t)1000000;
time2 = p->p_switchtime.tv_usec + p->p_switchtime.tv_sec * (int64_t)1000000;
if (time1 < time2)
panic("Ooops! Switchtime going backward!");
Stefan.
--
Stefan Eggers Lu4 yao2 zhi1 ma3 li4,
Max-Slevogt-Str. 1 ri4 jiu3 jian4 ren2 xin1.
51109 Koeln
Federal Republic of Germany
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