[GHC] #15136: High CPU when asynchronous exception and unblocking retry on TVar raced

[GHC]

#15136: High CPU when asynchronous exception and unblocking retry on TVar raced
-------------------------------------+-------------------------------------
        Reporter:  nshimaza          |                Owner:  osa1
            Type:  bug               |               Status:  merge
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Runtime System    |              Version:  8.4.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4956
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"502640c90c3d0fbb6c46257be14fdc7e3c694c6c/ghc"
 502640c9/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="502640c90c3d0fbb6c46257be14fdc7e3c694c6c"
 Optimise wakeups for STM

 Avoids repeated wakeup messages being sent when a TVar is written to
 multiple times. See comments for details.

 Test Plan:
 * Test from #15136 (will be added to stm shortly)
 * existing stm tests

 Reviewers: bgamari, osa1, erikd

 Reviewed By: bgamari

 Subscribers: rwbarton, thomie, carter

 GHC Trac Issues: #15136

 Differential Revision: https://phabricator.haskell.org/D4961
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15136#comment:15>
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