[Bug lket/4420] systemtap.samples/lket.exp test crashing RHEL4U4 machine

["joshua dot i dot stone at intel dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From joshua dot i dot stone at intel dot com  2007-07-25 17:33 -------
(In reply to comment #10)
> Possible solutions:
> 1. Use robust fault handling mechanism for handler which access user address
> space and chances of such handler causing page-faults are high. Robust fualt
> handling mechanism will recover from such faults.

This should always be the case.  It doesn't matter whether the chance of failure
is "high"  -- if there's *any* chance of failure we need to use fault-handling
mechanisms.

> 2. Black list __switch_to() routine and do not allow probes on them.
> 3. Restrick the probe handler to __switch_to(), so that probes on
> __switch_to() can be still allowed.
> 4. Use static markers for __switch_to() routines.

I don't understand why you think __switch_to() itself is to blame.  I haven't
been involved in all of the conversations, but it looks like __switch_to() just
provides a reproducible test-case, not the actual *cause* of the problem.

> It makes more sense to identify routines that get frequently executed in the
> hot path and use static markers to collect instrumenation data.

I agree with this for performance reasons, but it shouldn't make a difference as
a matter of correctness.



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http://sourceware.org/bugzilla/show_bug.cgi?id=4420

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