Bug#333052: Bug#333522: possible problem cause: wait4(-1)

[Rusty Russell <rusty@rustcorp.com.au>]

On Mon, 2005-10-31 at 19:53 +0100, Marco d'Itri wrote:
> On Oct 29, Rusty Russell <rusty@rustcorp.com.au> wrote:
> 
> > Please send complete log.
> Here it is. I can reproduce the bug even with a script like:
> 
> while read m; do
>   /sbin/modprobe.real $m &
> done < LIST
> 
> 
> (Each command was logged to different files which have been sorted by
> PID and reassembled.)

Unfortunately, this destroys the time sequence.  But it looks very much
like usbcore is slow to insmod, and the ehci-hcd.ko and uhci-hcd.ko
modules are not waiting for it to be inserted.

Hmm, if the root filesystem is read-only, then the locking will fail
(you need to open a file read/write to get an exclusive fcntl lock).
Perhaps this is happening to you?  If not, please check again that you
have the modified modprobe (strace of modprobe uhci-hcd after usbcore is
already inserted should show it locking usbcore).

We need to change locking strategy, I think.  Yet there's no clear way
to do this.  Might have to lock each module in the kernel somehow.
Fucking Unix, what a mess.

Rusty.
-- 
A bad analogy is like a leaky screwdriver -- Richard Braakman