[GHC] #10841: Run handler on STM retry

[GHC]

#10841: Run handler on STM retry
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        Reporter:  shlevy            |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  libraries         |                 Version:  7.10.2
  (other)                            |
      Resolution:                    |                Keywords:  stm
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by shlevy):

 fryguybob perhaps there's some confusion due to my calling it a "retry"
 handler? I don't mean merely to catch when the `retry` STM primitive is
 run, I also mean transaction aborts as simonpj mentioned.

 Unrelated to that: I realize now that my "try once" primitive won't work
 because there's no good way for the programmer to figure out when stm
 state has changed enough in other threads to be worth trying again, so the
 runtime does have to be in control of the looping.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10841#comment:6>
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