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Re: [Xen-devel] capturing SIGKILL in DomU

To: Michal Novotny <minovotn@xxxxxxxxxx>
Subject: Re: [Xen-devel] capturing SIGKILL in DomU
From: "Srujan D. Kotikela" <ksrujandas@xxxxxxxxx>
Date: Tue, 5 Oct 2010 08:14:37 -0500
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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Hi Michal,

I have no special interest in SIGKILL. All I want to do is notify Dom0 about an event in DomU (I don't need to pass any data). I am trying to indicate events by signals or interrupts. It means, if a "particular" interrupt has occurred in DomU, the Dom0 should be notified. Is there any other way of doing the same other than using event channels?

I am successful in establishing the event channel. But I am not quite sure how to send a notification that an event occurred in DomU to Dom0. Any pointers for the same would be appreciated.

Srujan D. Kotikela

On Tue, Oct 5, 2010 at 3:36 AM, Michal Novotny <minovotn@xxxxxxxxxx> wrote:
Hi Srujan,
what about adding a signal handler to qemu-dm in the tools/ioemu-dir of the user-space tools? Using the signal() API? Nevertheless why would you like to catch SIGKILL? This one (as can be seen using included program source and killing it using kill -9 pid or kill -SIGKILL pid) is not being caught at all nevertheless most of the other signals can be caught.

This is the source of the example mentioned:
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>

void sig_handler(int sig) {
   fprintf(stderr, "Signal %d caught.\n", sig);

int main()
   signal(SIGINT, sig_handler);
   signal(SIGKILL, sig_handler);

   return 0;

When I did try SIGINT (Ctrl + C or kill -2 pid) it caught the signal well but when I did try kill -9 pid (or kill -SIGKILL pid respectively) it was not working at all since it killed the process instead of going to the signal handler. When you need to catch signals like interruption signal (Ctrl + C one) this will work fine.


On 10/04/2010 09:03 PM, Srujan D. Kotikela wrote:

I am trying to capture SIGKILL through event channel.

On my Dom0, the following process is running (remaining code in attachment).

   int main(void){

       int ret, dom, remote_dom;

       //initialize domains

       //create the event channel
       ret = create_channel(dom, remote_dom);

       if (0 == ret) {
           printf("\n Event Channel established successfully \n");
       } else {
           return -1;    //EVENT_CHANNEL_CREATION_FAILED

       //wait 20 seconds for an event to occur in DomU

       //close the opened interfaces

       return 0;


While this process is running; I killed a process in DomU using `*kill SIGKILL pid*`

How can I capture this event (occured in DomU) at the Dom0. I watched /dev/xen/evtchn, but no notification.

Srujan D. Kotikela

Xen-devel mailing list

Michal Novotny<minovotn@xxxxxxxxxx>, RHCE
Virtualization Team (xen userspace), Red Hat

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