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Re: can systemtap send signal back to an application its monitoring? please help


Hi -

khadija.rsl wrote:

> I am a new user of Systemtap but for some reason I cannot access the
> forum though I get all the mails. [...]

It should let anyone post, if you use plain/text email.


> I am trying to monitor performance of network bound user application
> program (Eg. Wget) performance at kernel using systemtap .While monitoring
> Is it possible for systemtap to send 'signal' back to wget? [...]

We don't have a ready-made tapset function for this.  It's not quite
trivial since if we try:

   function send_sig (sig:long) %{
       send_sig (THIS->sig, current, 1);
   %}

we'd find that send_sig involves taking task->sighand->siglock, which
is not allowed from most of our probe contexts.  The way we'd probably
have to do this is with a formal deferred-work-queue, which involves
somewhat more machinery.  I opened http://sourceware.org/PR13864 about
this so we don't forget.

In the mean time, if immediate delivery of the signal is not
essential, you could try plopping

   system(sprintf("/bin/kill -%d %d", signum, pid))

into your script.  This incurs some latency as a round-trip to
userspace is involved.

- FChE


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