Date: Thu, 5 Sep 2002 15:20:20 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: John Baldwin <jhb@FreeBSD.org> Cc: freebsd-alpha@FreeBSD.org Subject: RE: ithread preemption Message-ID: <15735.44660.835003.901974@grasshopper.cs.duke.edu> In-Reply-To: <XFMail.20020905150640.jhb@FreeBSD.org> References: <15735.38318.66517.366474@grasshopper.cs.duke.edu> <XFMail.20020905150640.jhb@FreeBSD.org>
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John Baldwin writes: > > On 05-Sep-2002 Andrew Gallatin wrote: > > > > I've forgotten -- What are the symptoms of ithread preemption causing > > troubles on alpha? > > Hangs on SMP under load. > > > I have one (probably dumb) idea: Is the ithread preemption code > > guaranteed to switch back to the preempted thread when the ithread > > completes or blocks? And continue through to the end of the interrupt > > dispatch code, returning back to the palcode? > > It is not guaranteed to do that. What keeps you from (eventually) running out of kernel stack space then, as the interrupts keep coming in? Eg, would it help to keep a per-cpu (not per thread) interrupt nesting count and refuse to do preemption if the interrupt nesting count exceeds a small constant? Drew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message
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