[Bug runtime/12642] utrace: taskfinder misses events when main thread does not go through at least one quiesce

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12642

--- Comment #5 from David Smith <dsmith at redhat dot com> 2012-11-27 15:35:59 UTC ---
Commit f346b8b fixes this for everything except dyninst.

Here's what was going on with this one.

In the original utrace (RHEL5), UTRACE_STOP could interrupt the target task (by
sending the task a fake signal). This caused the target task to stop even when
it was sleeping.

In the newer utrace (RHEL6), that functionality was split out into
UTRACE_INTERRUPT. So, for RHEL6, we now make a pass after the systemtap session
is started and send all target tasks an UTRACE_INTERRUPT.

For newer kernels without utrace, I've implemented UTRACE_INTERRUPT support, so
just like for RHEL6, we now make a pass after the systemtap session is started
and send all target tasks an UTRACE_INTERRUPT.

I've added a test case, called 'main_quiesce.exp' that tests this issue.

This new test case passes everywhere, except with dyninst. That will need more
investigation.

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