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SubjectRe: Anyone working on multi-threaded core files for 2.4 ?
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> The synchronization on dump between the processes sharing a VM is quite nasty
> actually. There were patches for it in the past, but they usually got that
> wrong. Linux has no way currently to stop them atomically.

How atomic does it need to be, though ?

In a uni-processor there shouldn't be a problem, since if this thread
is running none of the others can be.

In an SMP then the only thing that can be expected is that the
registers for threads which were executing on a different processor at
the time that a thread dumped show those executing threads as being in
a place which they can reach given the interactions between the
threads. (I.e. that causality is maintained.)

It's like relativity, you can't ask about simultaneity, only
causality.

I was thinking that a scheme in which the core-dumping thread hit all
the others with a SIGSTOP and then (somehow...) waited for them all to
stop before writing the core file would suffice. (Of course, I may be
wrong !)

-- Jim

James Cownie <jcownie@etnus.com>
Etnus, LLC. +44 117 9071438
http://www.etnus.com



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