On Mon, 5 Jun 2023, Beauregard,Christophe (ECCC) wrote:
FWIW, I think I may have figured out what's happening. It's probably
something to note in the http://www.graphicsmagick.org/OpenMP.html
documentation.
In a nutshell, my understanding is that libgomp keeps track of its
thread pool in thread local storage. When that thread local storage
happens to be in the main process, all is well, everything works
fine, etc. When that thread local storage is in a transient pthread
(and, apparently, you're running on a certain class memory/CPU
configuration) and your transient thread terminates, that thread
local storage doesn't (always) get cleaned up.
This is very unfortunate and seems like a serious bug.
I suspect this isn't a particularly desirable situation, as
GraphicsMagick appears to have put at least some effort into making
the API thread-safe.
Considerable effort has been put into making the API as thread-safe as
possible, but invoking OpenMP code from a POSIX thread (or other sort
of thread) has not been significantly tested.
It would be good to write a bug report against gomp (it seems to still
be a GCC product) so that there is hope to get this fixed, or be
informed of a work-around.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
