Date: Sun, 17 Feb 2002 12:25:38 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Bruce Evans <bde@zeta.org.au> Cc: <freebsd-current@FreeBSD.ORG> Subject: Re: 'microuptime() went backwards ...' using ACPI timer. Shouldn't that be impossible? Message-ID: <200202172025.g1HKPc589840@apollo.backplane.com> References: <20020217184436.M934-100000@gamplex.bde.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200202172025.g1HKPc589840>