Date: Wed, 5 Oct 2005 12:10:28 -0400 From: Jung-uk Kim <jkim@FreeBSD.org> To: Peter Edwards <peadar.edwards@gmail.com> Cc: freebsd-current@FreeBSD.org Subject: Re: biodone panics Message-ID: <200510051210.30452.jkim@FreeBSD.org> In-Reply-To: <34cb7c840510050613u36e76be1pef82c41130da8804@mail.gmail.com> References: <34cb7c8405092815247dc89bf6@mail.gmail.com> <200509291303.41181.jhb@FreeBSD.org> <34cb7c840510050613u36e76be1pef82c41130da8804@mail.gmail.com>
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On Wednesday 05 October 2005 09:13 am, Peter Edwards wrote: > Take 2 for the biodone() panics: > > acd_geom_start() implements request limiting by breaking up a large > request in the passed bio into a sequence of smaller ones. As each > request is created, acd_strategy is invoked to start the IO. > > However, I think this IO can complete while still issuing the child > requests, leading to the parent being retired early. (ie, when a > child operation completes, it checks if its the last operation to > complete, and, if so, retires the parent: see g_std_done.) > > The attached patch makes my qemu box much more reliable (I could > crash a qemu hosted system 100% with a "tar fc" of the 6.0-BETA > bootonly ISO without the patch, and it's gone through many > iterations fine with it) > > Any opinions/testing results welcome. I think you nailed it! It's a shame that I had the same theory and I was staring at the same code with scratching my head for hours but I couldn't find proper fix. :-( Tested with QEMU 0.7.2 from ports/qemu for a while with no regression. BTW, minor style comment. Please do s/0/NULL/. Thanks a bunch! Jung-uk Kim
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