Date: Sun, 26 Dec 2004 23:56:51 +0100 From: Peter Holm <peter@holm.cc> To: Bosko Milekic <bmilekic@technokratis.com> Cc: current@freebsd.org Subject: Re: panic: uma_zone_slab is looping Message-ID: <20041226225651.GA87178@peter.osted.lan> In-Reply-To: <20041226181738.GA21533@technokratis.com> References: <20041209144233.GA46928@peter.osted.lan> <20041220234103.GA59225@technokratis.com> <20041222210553.GA28108@peter.osted.lan> <20041222221540.GA70052@technokratis.com> <20041226161153.GA74592@peter.osted.lan> <20041226181738.GA21533@technokratis.com>
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On Sun, Dec 26, 2004 at 01:17:38PM -0500, Bosko Milekic wrote: > > On Sun, Dec 26, 2004 at 05:11:53PM +0100, Peter Holm wrote: > > > > Yes, I think that I have verified your exelent analysis of the > > problem: http://www.holm.cc/stress/log/freeze04.html > > > > So, do have any fix suggenstons? :-) > > Not yet, because the problem is non-obvious from the trace. > > I need to know exactly when the UMA RCntSlabs zone recurses _first_, > and I need to confirm that it is an actual recursion. I've looked at > the VM code and I don't see how/why recursion on the RCntSlabs zone > would happen. > > Please modify the printf code to look exactly like this: > > if (keg->uk_flags & UMA_ZFLAG_INTERNAL && keg->uk_recurse != 0) { > if ((zone == slabzone) || (zone == slabrefzone)) > panic("Zone %s forced to fail due to recurse non-null: %d\n", > zone->uz_name, keg->uk_recurse); > return (NULL); > } > > (You don't need to check any global counter -- the counter is imperfect > anyway -- because even a single recursion on slabzone or slabrefzone > should be illegal). > > I'd like to see the trace from the above panic, if possible. Here it is: http://www.holm.cc/stress/log/freeze05.html > > Also, from your current crash dump, see if you can print the value of > keg->uk_recurse (from frame 11, pid 74804). > > It appears that the other KASSERT being triggered from > propagate_priority() is due to some weird side-effect of process > 74804 looping with the UMA RCntSlabs zone lock held (without it > ever being dropped). We'll have to see. > > The point is: the trace is useless unless it shows where/when the > recursion on slabrefzone _begins_ to happen (not that it has already > happened, that part is obvious now). > > Happy holidays, > -- > Bosko Milekic > bmilekic@technokratis.com > bmilekic@FreeBSD.org -- Peter Holm
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