Date: Tue, 19 Oct 2004 17:53:07 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Julian Elischer <julian@elischer.org> Subject: Re: Preemption-related bug in propagate_priority(): it's OK to hold Giant but not be running Message-ID: <Pine.NEB.3.96L.1041019175144.81058D-100000@fledge.watson.org> In-Reply-To: <200410191745.59493.jhb@FreeBSD.org>
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On Tue, 19 Oct 2004, John Baldwin wrote: > > it would be relatively simple to put those 'discarded' threads onto a > > single list in the kernel > > and 'c' could put them back on the run queue :-) > > That's a really nasty hack. I almost wonder if we shouldn't just bump > the priority of the thread that panics way up instead, or maybe use a > dedicated thread for handling panics or something. I have to admit I was somewhat surprised to see that a thread was preempted during a panic. I had sort of assumed that as we panicked we disabled interrupts, since the I/O for the debugger is polled, etc. Speaking of which, I've seen a number of bug reports that suggest our polled debugger I/O interfaces for the low level console are not implemented properly by syscons (and maybe also sio), resulting in unnecessary debugging complications (running wakeup() while in DDB and so on). Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research
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