Red Hat Bugzilla – Bug 104912
RFE: would like echo p > /proc/sysrq-trigger to show registers
Last modified: 2007-11-30 17:06:53 EST
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Description of problem:
Is it possible to get echo p > /proc/sysrq-trigger to show registers.
I opened a call with RedHat support on this and they told me to
submit a RFE (Request for Enhancement) on bugzilla.
Basicall, echo m > /proc/sysrq-trigger works as well as
echo t > /proc/sysrq-trigger. However, echo p > /proc/sysrq-trigger
does not work. Many times when I call redhat support, they ask for
the output of this syrq "p" trigger.
It would be handy if you could do this remotely or from a script instead of
having to be sitting in front of the console and hitting
the <alt> <sysrq> keys.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. echo 1 > /proc/sys/kernel/sysrq
2. echo p > /proc/sysrq-trigger
Actual Results: dmesg and /var/log/messages show this line:
SysRq: Show Regs
That's it nothing else is printed. If you go to console and
hit <alt> <sysrq> <p> than registers get dumped.
Expected Results: Expect registers to get dumped.
Tested this on e.24, e.27 and beta Linux Enterprise 3 kernel.
If "echo p > /proc/sysrq-trigger" dumps the registers, you are almost certain to
see a process in the middle of sys_write(2), to a file in /proc. More precisely,
it'll be writing to /proc/sysrq-trigger.
I'm not sure how dumping that info would be very useful, since you know what's
happening on your cpu when you echo something to /proc/sysrq-trigger ...
However, let me know if I've overlooked something (I wouldn't be surprised).
You bring up a good point, if the only info you'll gather is capturing a
syswrite from the "echo p" process, than I guess that doesn't make a whole lot
Is there any way to dump the regs remotely if you're not in front of the
Over serial console you can trigger sysrq commands.
By default you need to send a break, followed by the sysrq letter.
In /proc/sys/kernel/sysrq-key you can configure another special key, which is
useful if your terminal program doesn't want to send a break.
Closing as this appears to be resolved.