Re: race condition between udevd and modprobe (mtrr_add)

[Kay Sievers]

On Tue, May 4, 2010 at 07:30, Kyle Hubert <khubert@xxxxxxxxx> wrote:
> Hi, while booting an initrd image built off of BusyBox on a thousand
> nodes, we hit a race on a couple of nodes. They hang during the boot
> process with the stack traces listed below. The really simple init
> script in the initrd does a 'udevd --daemon' and then modprobe of a
> device. The device needs to assign an mtrr to the pci resource, and
> instead the whole node hangs. Putting a 'sleep 1' in between these two
> calls prevents any hangs.
>
> mtrr_add_page and the buddy allocator code don't appear to share any
> semaphores, and there isn't an obvious way in which this can hang.
> Possibly the smp_call_function IPI isn't being handled by the other
> cores... That's the best guess. Can anyone help sort this mess out?
>
> Also, is there a better way to test that udevd is fully up? A 'sleep
> 1' is not the preferred solution here.

"udevadm settle" might do it.

Kay
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/