Date: Tue, 8 Feb 2005 21:14:37 +0100 From: Peter Holm <peter@holm.cc> To: John Baldwin <jhb@FreeBSD.org> Cc: freebsd-current@FreeBSD.org Subject: Re: Deadlock with option FULL_PREEMPTION Message-ID: <20050208201437.GA46141@peter.osted.lan> In-Reply-To: <200502081448.43759.jhb@FreeBSD.org> References: <20050206134113.GA77071@peter.osted.lan> <200502081317.40267.jhb@FreeBSD.org> <20050208190836.GA45874@peter.osted.lan> <200502081448.43759.jhb@FreeBSD.org>
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On Tue, Feb 08, 2005 at 02:48:43PM -0500, John Baldwin wrote: > On Tuesday 08 February 2005 02:08 pm, Peter Holm wrote: > > On Tue, Feb 08, 2005 at 01:17:40PM -0500, John Baldwin wrote: > > > On Sunday 06 February 2005 08:41 am, Peter Holm wrote: > > > > With GENERIC HEAD from Feb 5 09:19 UTC + FULL_PREEMPTION + > > > > mpsafe_vfs = 1 I ran into what appears to be the same deadlock > > > > twice. This is the first one: > > > > http://www.holm.cc/stress/log/cons114.html > > > > > > What is the deadlock exactly? > > > > top froze, console login froze after giving login name, but I > > could ping the box. > > So it could be livelock rather than deadlock if interrupt processing still > works (ping). > > > > > > It looks like lots of threads banging on fork() > > > and that they are all waiting on an exclusive lock of allproc_lock while > > > holding a shared lock of proctree_lock (except for the 1 thread currently > > > doing a fork that is on a run queue because it was preempted by IRQ 0 > > > which kicked off softclock). Can you get 'ps' output? > > > > Yes: > > Well, kmail butchered this in my reply so I won't quote any of it, but it does > seem that the process everyone is waiting on is runnable. I'm not sure if > there's anything you can do to recover from the livelock, but the livelock is > holding up all the forks so you can't get a login process to fork a shell, > etc. (At least not quickly apparently). > Oh, recovery is not an issue. I'm stress testing, but this problem does seem to prevent finding other kernel problems with FULL_PREEMPTION. I'll just go back to testing without this option. Thanx for looking at this. > -- > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > "Power Users Use the Power to Serve" = http://www.FreeBSD.org -- Peter Holm
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