[GHC] #9656: Process and thread init/deinit hooks for C libraries

[GHC]

#9656: Process and thread init/deinit hooks for C libraries
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              Reporter:  3noch       |            Owner:
                  Type:  feature     |           Status:  closed
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:  FFI
            Resolution:  invalid     |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by AndreasVoellmy):

 (Let me know if this discussion has moved elsewhere.)

 I've wondered about this question, too. I have a multithreaded Haskell
 program that makes some calls into a JVM. To do this, each OS thread
 calling into the JVM needs to have some data initialized. While I could do
 the forkOS approach, I want to have any Haskell thread call into Java,
 rather than having to send a message to my forkOS'd Haskell thread, wait
 for it to be scheduled, have it do the call, send a message back, etc. One
 idea is to have a capability-local data structure, but that doesn't work
 because multiple OS threads might execute a capability (at different
 times). So I have to manage the initialization in the C code: whenever the
 C code is invoked in a given OS thread, the thread checks whether its data
 structures are initialized.

 No conclusions here, just wanted to chime with my experience on this
 topic.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9656#comment:6>
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