[ltp] diagnosing a freeze on T60p with ubuntu hardy

Dmitry E. Mikhailov linux-thinkpad@linux-thinkpad.org
Wed, 21 May 2008 16:53:47 +0600


=46rom kernel documentation:

<QUOTE>
*  How do I enable the magic SysRq key?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when
configuring the kernel. When running a kernel with SysRq compiled in,
/proc/sys/kernel/sysrq controls the functions allowed to be invoked via
the SysRq key. By default the file contains 1 which means that every
possible SysRq request is allowed (in older versions SysRq was disabled
by default, and you were required to specifically enable it at run-time
but this is not the case any more). Here is the list of possible values
in /proc/sys/kernel/sysrq:
   0 - disable sysrq completely
   1 - enable all functions of sysrq
  >1 - bitmask of allowed sysrq functions (see below for detailed function
       description):
          2 - enable control of console logging level
          4 - enable control of keyboard (SAK, unraw)
          8 - enable debugging dumps of processes etc.
         16 - enable sync command
         32 - enable remount read-only
         64 - enable signalling of processes (term, kill, oom-kill)
        128 - allow reboot/poweroff
        256 - allow nicing of all RT tasks

You can set the value in the file by the following command:
    echo "number" >/proc/sys/kernel/sysrq

</QUOTE>

So make sure you've enabled the magic key.