[GHC] #13633: testwsdeque failure on POWER8

[GHC]

#13633: testwsdeque failure on POWER8
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        Reporter:  trommler          |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Runtime System    |              Version:  8.1
      Resolution:                    |             Keywords:  SMP, ci-
                                     |  breakage
Operating System:  Linux             |         Architecture:  powerpc64
 Type of failure:  Runtime crash     |            Test Case:
                                     |  rts/testwsdeque
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  ghc/ghc!445
       Wiki Page:                    |
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Comment (by Marge Bot <ben+marge-bot@…>):

 In [changeset:"5c084e0468be46f5ab48b2c1669a7e4d4d0f3c43/ghc"
 5c084e04/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5c084e0468be46f5ab48b2c1669a7e4d4d0f3c43"
 RTS: Add missing memory barrier

 In the work stealing queue a load-load-barrier is required to ensure
 that a read of queue data cannot be reordered before a read of the
 bottom pointer into the queue.

 The added load-load-barrier ensures that the ordering of writes enforced
 at the end of `pushWSDeque` is also respected in the order of reads in
 `stealWSDeque_`. In other words, when reading `q->bottom` we want to make
 sure that we see the updates to `q->elements`.

 Fixes #13633
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13633#comment:9>
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