Date: Tue, 6 Jul 2004 00:14:21 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Thorsten Greiner <thorsten@tgreiner.net> Cc: current@freebsd.org Subject: Re: Native preemption is the culprit [was Re: today's CURRENT lockups] Message-ID: <Pine.NEB.3.96L.1040706001249.2853I-100000@fledge.watson.org> In-Reply-To: <20040705184940.GA2651@tybalt.greiner.local>
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(This time to more people)
The patch below appears to (brute force) eliminate the crash/hang I'm
experiencing with SCHED_ULE in the post-preemption universe. However, I
was experiencing it only in the SMP case, not UP, so it could be I'm just
not triggering it timing-wise. This would be a temporary fix until jhb is
online again post-USENIX to take a look, assuming this works around the
problem for people other than me.
Note that this is probably damaging to interrupt processing latency.
Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org Principal Research Scientist, McAfee Research
Index: sched_ule.c
===================================================================
RCS file: /data/ncvs/src/sys/kern/sched_ule.c,v
retrieving revision 1.112
diff -u -r1.112 sched_ule.c
--- sched_ule.c 3 Jul 2004 16:57:51 -0000 1.112
+++ sched_ule.c 6 Jul 2004 02:52:18 -0000
@@ -1623,6 +1623,7 @@
if (td->td_priority < curthread->td_priority)
curthread->td_flags |= TDF_NEEDRESCHED;
+#if 0
#ifdef SMP
/*
* Only try to preempt if the thread is unpinned or pinned to the
@@ -1632,6 +1633,7 @@
#endif
if (maybe_preempt(td))
return;
+#endif
ke->ke_ksegrp->kg_runq_kses++;
ke->ke_state = KES_ONRUNQ;
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