Date: Mon, 11 Oct 2004 16:54:14 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Stephan Uphoff <ups@tree.com> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@FreeBSD.org> Subject: Re: scheduler (sched_4bsd) questions Message-ID: <200410111654.14502.jhb@FreeBSD.org> In-Reply-To: <1097437808.80398.4.camel@palm.tree.com> References: <1095468747.31297.241.camel@palm.tree.com> <20041005130308.GA2586@peter.osted.lan> <1097437808.80398.4.camel@palm.tree.com>
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On Sunday 10 October 2004 03:50 pm, Stephan Uphoff wrote: > On Tue, 2004-10-05 at 09:03, Peter Holm wrote: > > On Mon, Oct 04, 2004 at 12:42:53PM -0700, Julian Elischer wrote: > > > > OK, I got a crash dump now, after a few modifications to kern_shutdown.c > > > > There are however a few strange things worth noticing: > > > > 1) The are no panic string: > > > > Mounted root from ufs:/dev/ad0s1a. > > pid 1146: corrected slot count (2->1) > > [thread 100796] > > Stopped at sched_add+0x13: movl 0x14c(%esi),%ebx > > > > 2) The gdb stack trace gets a bit weird at: > > > > #8 0xc07812da in calltrap () at ../../../i386/i386/exception.s:140 > > #9 0xc05f0018 in flock (td=0x0, uap=0x0) at > > ../../../kern/kern_descrip.c:2138 #10 0xc0619fd1 in setrunqueue > > (td=0xc2319180, flags=0x0) at kern_switch.c:521 #11 0xc061921f in > > sched_wakeup (td=0xc2319180) at ../../../kern/sched_4bsd.c:859 > > > > Where did flock() come from? > > > > The full console output is at http://www.holm.cc/stress/log/cons82.html > > > > - Peter > > I am still puzzled. > My newest pet theory is that the sorting of the kg_runq is corrupted > before setrunqueue is called. > Directly changing td_priority while the thread is on the run queue would > be an explanation. > However the only instance that I found is what I think is a rare > condition where sleepq_resume_thread may be called while the thread is > on a runqueue. (John - what did I miss this time ...) This is a good find! > Peter could you try this patch? > > Index: subr_sleepqueue.c > =================================================================== > RCS file: /cvsroot/src/sys/kern/subr_sleepqueue.c,v > retrieving revision 1.11 > diff -u -r1.11 subr_sleepqueue.c > --- subr_sleepqueue.c 19 Aug 2004 11:31:41 -0000 1.11 > +++ subr_sleepqueue.c 10 Oct 2004 18:18:55 -0000 > @@ -642,7 +642,7 @@ > /* Adjust priority if requested. */ > MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX)); > if (pri != -1 && td->td_priority > pri) > - td->td_priority = pri; > + sched_prio(td, pri); > setrunnable(td); > mtx_unlock_spin(&sched_lock); > } > > Should it crash again could you walk the kg_runq to verify the sorting? > > Thanks > Stephan -- 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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