Re: external systemtap meeting notes 20070816

["Frank Ch. Eigler" <fche at redhat dot com>]

Hi -

On Wed, Sep 26, 2007 at 01:42:29AM -0700, Roland McGrath wrote:

> [...]  The future non-signal mechanism I described there can have a
> reporting interface [...]  The other part of the problem is
> insertion/removal.  Naive non-cooperation works if they literally
> nest, but not if removal order is not LIFO.  I don't have any
> implicit-communication solution for that off hand.

Yeah, this is roughly why we pointed out some time back that the
utrace layer would be well situated to provide a high-level
breakpoint-related API.

What do you suggest in the interim?

Would this hack work: have the second utrace engine refuse to put a
breakpoint wherever it suspects another engine may have put one?  Or
even more pessimistically, can an engine know that another one is
already monitoring a given target process, and give up at attach time?
(That would defeat some of the promise of utrace, but so it goes.)

- FChE

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