Excerpts from Bruce Guenter's message of 2011-08-01 18:59:15 -0400:

On Mon, Aug 01, 2011 at 04:41:10PM -0600, cwillu wrote:

quoted

The keystroke should be alt-sysrq-w.

Right.  What I meant is that no backtraces are showing up.  I was
actually using

    echo w > /proc/sysrq-trigger

and all I was seeing is:

SysRq : Show Blocked State
  task                        PC stack   pid father

# once per boot, run dmesg -n8
dmesg -n8

echo w > /proc/sysrq-trigger