Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 7 Dec 2015 17:59:41 -0800 | Subject | Re: [V9fs-developer] Hang triggered by udev coldplug, looks like a race |
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On Mon, Dec 7, 2015 at 2:46 PM, Dominique Martinet <dominique.martinet@cea.fr> wrote: > Andy Lutomirski wrote on Mon, Dec 07, 2015: >> On Thu, Dec 3, 2015 at 9:52 PM, Andy Lutomirski <luto@amacapital.net> wrote: >> > Sometimes udevadm trigger --action=add hangs the system, and the splat >> > below happens. This seems to be timing dependent, and I haven't been >> > able to trigger it yet with lockdep enabled, sadly. >> > >> > Any ideas? I not, I'll try to instrument it better tomorrow. >> >> More details: this is caused by a storm of /sbin/hotplug UMH calls >> (yes, misconfigured kernel, but still). /sbin is a symlink to >> /usr/sbin, /usr/sbin/hotplug doesn't exist, and all of the above is on >> rootfs, which is 9p over virtio. >> >> Pointing uevent_helper at /usr/sbin/hotplug (which still doesn't >> exist) seems to work around it. > > Can you reproduce it on a booted system with something like > `seq 1 1000000 | xargs -P 1024 -I{} cat /sbin/foo >&/dev/null` ?
This doesn't reproduce it.
This doesn't either:
seq 1 1000000 | xargs -P 1024 -I{} bash -c 'exec /sbin/foo' &>/dev/null
> > (trying execs might be closer to your workload, not sure how much this > or using umh might change) > > > Also, what qemu version please just to try to match your environment ?
$ qemu-system-x86_64 --version QEMU emulator version 2.4.1 (qemu-2.4.1-1.fc23), Copyright (c) 2003-2008 Fabrice Bellard
My reproducer is:
$ virtme-run --kdir . --pwd
using this virtme version:
https://git.kernel.org/cgit/utils/kernel/virtme/virtme.git/commit/?id=17363c2900e8b796c80c920c6fcdcc6747784ef7
Bad kernel config attached. This config with v4.4-rc3 (and no additional patches) reproduces it reliably for me.
With the latest virtme, I don't reproduce it -- the latest virtme turns off uevent_helper early in boot, which suppresses the bug for me, at least most of the time.
If I dump all task states (see attached typescript), I see a bunch of things blocked in 9p rpc. This makes me think it could be a QEMU bug, not a kernel bug.
--Andy
-- Andy Lutomirski AMA Capital Management, LLC [unhandled content-type:application/x-xz][unhandled content-type:application/x-xz] | |