[GHC] #2411: RaiseAsync and STM segfault with stop_at_atomically in some circumstances.

[GHC]

#2411: RaiseAsync and STM segfault with stop_at_atomically in some circumstances.
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 Reporter:  sclv            |          Owner:         
     Type:  bug             |         Status:  new    
 Priority:  normal          |      Milestone:  6.10.1 
Component:  Runtime System  |        Version:  6.8.3  
 Severity:  normal          |     Resolution:         
 Keywords:                  |     Difficulty:  Unknown
 Testcase:                  |   Architecture:  Unknown
       Os:  Unknown         |  
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Comment (by sclv):

 Ok. So I've narrowed down a relatively simple test case. It crashes even
 at -N1 but crashes much more immediately at -N4. The backtrace is the same
 as above.

 From this test case its pretty clear that there's an issue either with
 catchSTM or directly with RaiseAsync.c or with their interaction, and in
 fact unsafePerformIO and unsafeIOToSTM are nowhere to be found in this
 code.

 This test case can probably be distilled down to something even simpler
 that doesn't use any of the typeclass toys I was playing with that ended
 up here in the first place. But I've taken it about as far as I can today.

 As far as I know though, this is only triggered during validation during
 GC, which is the only time stop_at_atomically is set. So one question I
 have is why a thread which is already hit by an asynchronous exception
 should *then* be treated as invalid as well and subject to an attempt to
 roll back during scheduleDoGC. So it may be that there are two different
 mechanisms (one for exception handling via catchSTM and one for
 validation) that end up stepping on one another's toes. Just spinning a
 theory though.

 I should note this bug occurs in 6.8.3 up through HEAD as far as I know.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2411#comment:3>
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