Date: Mon, 4 Oct 2004 13:21:45 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Stephan Uphoff <ups@tree.com> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@FreeBSD.org> Subject: Re: sched_switch (sched_4bsd) may be preempted Message-ID: <200410041321.45142.jhb@FreeBSD.org> In-Reply-To: <1096610130.21577.219.camel@palm.tree.com> References: <1096610130.21577.219.camel@palm.tree.com>
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On Friday 01 October 2004 01:55 am, Stephan Uphoff wrote:
> sched_switch (sched_4bsd) may be preempted in setrunqueue or slot_fill.
> This could be ugly.
> Wrapping it into a critical section and resetting TDP_OWEPREEMPT should
> work.
>
> Hand trimmed patch:
>
> RCS file: /cvsroot/src/sys/kern/sched_4bsd.c,v
> retrieving revision 1.65
> diff -u -r1.65 sched_4bsd.c
> --- sys/kern/sched_4bsd.c 16 Sep 2004 07:12:59 -0000 1.65
> +++ sys/kern/sched_4bsd.c 1 Oct 2004 05:35:28 -0000
> @@ -823,6 +823,7 @@
> TD_SET_CAN_RUN(td);
> else {
> td->td_ksegrp->kg_avail_opennings++;
> + critical_enter();
> if (TD_IS_RUNNING(td)) {
> /* Put us back on the run queue (kse and all).
> */
> setrunqueue(td, SRQ_OURSELF|SRQ_YIELDING);
> @@ -834,6 +835,8 @@
> */
> slot_fill(td->td_ksegrp);
> }
> + critical_exit();
> + td->td_pflags &= ~TDP_OWEPREEMPT;
> }
> if (newtd == NULL)
> newtd = choosethread();
I thought that SRQ_YIELDING turned preempting off already.
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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