[Bug tapsets/10655] New: SDT semaphores should be prepared for multiple tasks per probe

[Bug tapsets/10655] New: SDT semaphores should be prepared for multiple tasks per probe

[jistone at redhat dot com]

We shouldn't be keeping a tsk field in stap_uprobe_spec or stap_utrace_probe,
because each of those may get many tasks associated with them.  The XXX comments
added in commit a9b59347 show the places where this is happening.  Instead, we
should be poking the semaphores when we are detaching from each task at the end
of the script.  I think task finder may need to be expanded to give the right
callbacks here.

Task death is also a consideration, though it won't matter whether the semaphore
is adjusted in that case.  We just need to make sure we don't try to adjust the
semaphore *after* death, when the memory doesn't exist anymore.

-- 
           Summary: SDT semaphores should be prepared for multiple tasks per
                    probe
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: jistone at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10655

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[Bug tapsets/10655] SDT semaphores should be prepared for multiple tasks per probe

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2009-09-18 19:29 -------
This is critical, since the current code includes statements that
modify const static data (struct stap_uprobe_specs[]; the new ->tgt
field).  This is successfully blocked on some machines (my 4cpu
kvm VM on a xeon5150 pair being one of them), resulting in panic's.
So it has to be fixed.

There may be other such bugs that for some reason are only caught
on a peculiar simulator environment.  Others should check whether
they have NX-capable hardware and kvm, as that seems to be a factor.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|systemtap at sources dot    |fche at redhat dot com
                   |redhat dot com              |
           Severity|normal                      |critical
             Status|NEW                         |ASSIGNED


http://sourceware.org/bugzilla/show_bug.cgi?id=10655

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