Date: Sat, 25 Aug 2007 10:41:09 -0700 From: "Kip Macy" <kip.macy@gmail.com> To: "Andrew Turner" <andrew@fubar.geek.nz>, "Robert Watson" <rwatson@freebsd.org>, freebsd-current@freebsd.org Subject: Re: FreeBSD on xen hvm Message-ID: <b1fa29170708251041q11fee0a3o7f3f319afa40db60@mail.gmail.com> In-Reply-To: <20070826000708.15fbb5bb@hermies.int.fubar.geek.nz> References: <20070824181627.57bed401@hermies.int.fubar.geek.nz> <20070824132409.W3900@fledge.watson.org> <20070826000708.15fbb5bb@hermies.int.fubar.geek.nz>
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Have you tried gdbserver? -Kip On 8/25/07, Andrew Turner <andrew@fubar.geek.nz> wrote: > On Fri, 24 Aug 2007 13:30:17 +0100 (BST) > Robert Watson <rwatson@FreeBSD.org> wrote: > > On Fri, 24 Aug 2007, Andrew Turner wrote: > > > > > 1) PREEMPTION Preemption causes the kernel to panic with a page > > > fault. The dmesg is available from [1]. > > > > Any chance it's possible to get a core for this, or attach GDB > > somehow to the VM? > I haven't managed to get either remote GDB working and it's too early > in the boot for a core. I can get a xen core dump but it would require > processing to get it into something gdb could use. > > It looks like timing in Xen may be exposing a > > race in some or another subsystem with timers, but figuring out which > > subsystem it is will be most easily done if we can inspect the > > callout information, which is most easily done with GDB since you can > > inspect the callout structure more easily. If not, then we can add > > some printfs to extract the information, I expect, or extend DDB. We > > need to find out what the function pointer in the callout structure > > is for. > I've created a patch at [1] to add "show callouts" to ddb. It prints > all the callouts in callwheel and the name of the function they call. > The callouts with preemption are: > loadav > in6_tmpaddrtimer > in6_rtqtimo > in_rtqtimo > in6_mtutimo > uma_timeout > nd6_slowtimo > nfsrv_timer > tcp_isn_tick > scrn_timer > roundrobin > atkbd_timeout > sleepq_timeout > sleepq_timeout > sleepq_timeout > sleepq_timeout > pffasttimo > pfslowtimo > kbdmux_kbd_intr_timo > if_slowtimo > ipport_tick > nd6_timer > lboltcb > tcp_hc_purge > > Preemption does not always cause the kernel to panic, however when it > doesn't it shows the mountroot> prompt and is unable to load the root > as no disk drives show up. > > > > > 3) INVARIANTS Invariants causes a panic from a page fault. See [2] > > > for the dmesg and backtrace. > > > > This appears to be in the start up of Audit as it creates a kernel > > thread. Possibly it's creating the thread too early, or possibly > > something else is going on. Can you try creating a kernel without > > options AUDIT and see if it works better, or if it just panics when > > the next thread is created? > It just panics in the next thread created. > > > > It sounds like Xen may start the timer firing sooner than on plain > > hardware, or possibly at a faster rate initially, and that's causing > > things to happen in a different order, so I expect we'll either bump > > into a series of races of this sort based on different ordering of > > events, or discover the timer isn't properly being disabled or > > managed in Xen :-). > I'm suspecting the timer isn't being managed properly. The timer in the > loader always stays at 10 and with DIAGNOSTIC I'm getting lines like: > Expensive timeout(9) function: 0xc097da70(0xc0bbaa00) -1.982636062 s > > Andrew > > [1] http://fubar.geek.nz/files/freebsd/ddb-callout.diff > > -- > Andrew Turner > http://fubar.geek.nz/blog/ > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >
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