Linux-kernel mailing list archive 2000-40,: Re: Anyone working on multi-threaded core files for 2.4 ?

# Re: Anyone working on multi-threaded core files for 2.4 ?

Peter Samuelson (peter@cadcamlab.org)
Fri, 29 Sep 2000 11:04:07 -0500

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[James Cownie]
> 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 !)

Can someone explain why core dumping can't be done in userspace?
Probably a deficiency in my binary file format education but I don't
get it. It seems as though libpthreads could install a SEGV handler by
default that would increment a shared got-core-signal variable and
re-send the SEGV to all other threads, then each dump out its own stack
and register context and have one of them dump the memory. (This
collapses to a much simpler handler in libc for non-threaded code.)
Sure it means libc gets a nifty new complex function perhaps linked
against libbfd, but in terms of memory footprint you don't pay that
price until something crashes.

There must be a good reason Unix and Linux don't do this ... but I
haven't thought of it yet. Anyone care to enlighten me?

Peter
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