Reason for the "one dot" hang found!

[Bernie Innocenti]

Hello,

with the serial cable Richard gave me, I figured out what's causing a
rare lockup during boot which has been riddling the XO-1 since when we
moved to F11.

The /etc/rc.sysinit script contains this line:

 # Sync waiting for storage.
 { rmmod scsi_wait_scan ; modprobe scsi_wait_scan ; rmmod  scsi_wait_scan ; } >/dev/null 2>&1

It gets executed while udev is loading modules in parallel. Apparently,
something in the kernel ends up dead-locking on module load:


   1 tty1     Ss+    0:02 /sbin/init
 945 ?        Ss     0:00 /bin/sh -e -c ?runlevel --set S >/dev/null || true???/
 950 ?        S      0:00  \_ /bin/bash /etc/rc.d/rc.sysinit
1597 ?        D      0:00      \_ modprobe scsi_wait_scan
 946 ttyS0    Rs     0:00 /bin/bash --
1712 ttyS0    R+     0:00  \_ ps afx
1010 ?        S<s    0:00 /sbin/udevd -d
1035 ?        D<     0:00 /sbin/modprobe -b pci:v000011ABd00004102sv000011ABsd00


So it's definitely a kernel bug. Would someone like to dig into the init
function of scsi_wait_scan to find out the root cause?

Since the XO-1 is in long-term maintenance at this point, to save time
we could opt instead for a quick & dirty solution such as commenting out
the modprobe line in rc.sysinit. As far as I can tell, it's not needed
on the XO.

-- 
   // Bernie Innocenti - http://codewiz.org/
 \X/  Sugar Labs       - http://sugarlabs.org/