UTRACE_STOP in exec handler

[David Smith]

Roland,

I'm seeing a problem on with the new utrace on
2.6.27-0.323.rc6.fc10.x86_64.  Basically, if I attach a new engine in an
exec handler, and use utrace_control() with UTRACE_STOP, the task
doesn't reliably stop.

I was seeing this behaviour with systemtap, so I started with
crash-suspend.c and mangled it to do something similar, to hopefully
simplify the problem down a bit.

So, try compiling this module, then insmod it with the pid of a bash
process.  What I expected to happen is that every new process exec'ed by
that bash shell gets stopped once.  Instead, "ls" will run to completion
without stopping. If you run "cat", then use Ctrl-C to kill it, you'll
get a quiesce event.

So, is this a problem with the way I'm attempting to stop the thread or
a utrace bug?

(Note that I've tried returning UTRACE_STOP from the exec handler
instead of calling utrace_control(), but it makes no difference.)

-- 
David Smith
dsmith at redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)
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