[commit: ghc] master: Fix deadlock (#10545) (111ba4b)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/111ba4beda4ffc48381723da12e5b237d7f9ac59/ghc

>---------------------------------------------------------------

commit 111ba4beda4ffc48381723da12e5b237d7f9ac59
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Fri Jun 19 15:12:24 2015 +0100

    Fix deadlock (#10545)
    
    yieldCapability() was not prepared to be called by a Task that is not
    either a worker or a bound Task.  This could happen if we ended up in
    yieldCapability via this call stack:
    
    performGC()
    scheduleDoGC()
    requestSync()
    yieldCapability()
    
    and there were a few other ways this could happen via requestSync.
    The fix is to handle this case in yieldCapability(): when the Task is
    not a worker or a bound Task, we put it on the returning_workers
    queue, where it will be woken up again.
    
    Summary of changes:
    
    * `yieldCapability`: factored out subroutine waitForWorkerCapability`
    * `waitForReturnCapability` renamed to `waitForCapability`, and
      factored out subroutine `waitForReturnCapability`
    * `releaseCapabilityAndQueue` worker renamed to `enqueueWorker`, does
      not take a lock and no longer tests if `!isBoundTask()`
    * `yieldCapability` adjusted for refactorings, only change in behavior
      is when it is not a worker or bound task.
    
    Test Plan:
    * new test concurrent/should_run/performGC
    * validate
    
    Reviewers: niteria, austin, ezyang, bgamari
    
    Subscribers: thomie, bgamari
    
    Differential Revision: https://phabricator.haskell.org/D997
    
    GHC Trac Issues: #10545


>---------------------------------------------------------------

111ba4beda4ffc48381723da12e5b237d7f9ac59
 rts/Capability.c                                   | 301 +++++++----
 rts/Capability.h                                   |   8 +-
 rts/RtsAPI.c                                       |   2 +-
 rts/Schedule.c                                     |  14 +-
 rts/Task.h                                         |  11 +
 testsuite/tests/concurrent/should_run/RandomPGC.hs | 597 +++++++++++++++++++++
 testsuite/tests/concurrent/should_run/all.T        |   4 +
 testsuite/tests/concurrent/should_run/performGC.hs |  24 +
 .../tests/concurrent/should_run/performGC.stdout   | 400 ++++++++++++++
 9 files changed, 1231 insertions(+), 130 deletions(-)

Diff suppressed because of size. To see it, use:

    git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc 111ba4beda4ffc48381723da12e5b237d7f9ac59