[GHC] #9516: unsafeUnmask unmasks even inside uninterruptibleMask
#9516: unsafeUnmask unmasks even inside uninterruptibleMask -------------------------------------+------------------------------------- Reporter: edsko | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Control.Exception exports {{{#!hs allowInterrupt :: IO () allowInterrupt = unsafeUnmask $ return () }}} with documentation: ''When invoked inside `mask`, this function allows a blocked asynchronous exception to be raised, if one exists. It is equivalent to performing an interruptible operation, but does not involve any actual blocking. When called outside `mask`, or inside `uninterruptibleMask`, this function has no effect.'' However, this is not actually true: `unsafeUnmask` unmasks exceptions even inside `uninterruptibleUnmask`, as the attached test demonstrates (the test uses a foreign call just to have something non-interruptible but still observable; in particular, doing a `print` ''is'' interruptible because it uses an `MVar` under the hood). I think it is possible to define a better `unsafeUnmask` in user-land: {{{#!hs interruptible :: IO a -> IO a interruptible act = do st <- getMaskingState case st of Unmasked -> act MaskedInterruptible -> unsafeUnmask act MaskedUninterruptible -> act }}} but it still seems to be that we should either (i) change the behaviour of unsafeUnmask, or (ii) provide a version of `unsafeUnmask` with the behaviour as described and then change `allowInterrupt` to use that new version of `unsafeUnmask`, or at the very least (iii) change the documentation. (One question with the above definition of `interruptible` is what happens when we ''nest'' `mask` and `uninterruptibleMask`?) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9516 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9516: unsafeUnmask unmasks even inside uninterruptibleMask -------------------------------------+------------------------------------- Reporter: edsko | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 7.8.2 System | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonmar): good catch, and a nice bug report. I think `unsafeUnmask` is fine, but the implementation of `allowInterrupt` is wrong, and we should replace it with your version. Would you like to submit a patch? (I'm on holiday right now, but no need to wait for me to approve it, Austin can approve and push.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9516#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9516: unsafeUnmask unmasks even inside uninterruptibleMask -------------------------------------+------------------------------------- Reporter: edsko | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 7.8.2 System | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D181 | -------------------------------------+------------------------------------- Changes (by thoughtpolice): * differential: => Phab:D181 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9516#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9516: unsafeUnmask unmasks even inside uninterruptibleMask
-------------------------------------+-------------------------------------
Reporter: edsko | Owner: simonmar
Type: bug | Status: new
Priority: normal | Milestone:
Component: Runtime System | Version: 7.8.2
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Revisions: Phab:D181
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Comment (by Ben Gamari
#9516: unsafeUnmask unmasks even inside uninterruptibleMask -------------------------------------+------------------------------------- Reporter: edsko | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: Component: Runtime System | Version: 7.8.2 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D181 -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9516#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9516: unsafeUnmask unmasks even inside uninterruptibleMask -------------------------------------+------------------------------------- Reporter: edsko | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: 8.0.1 Component: Runtime System | Version: 7.8.2 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D181 -------------------------------------+------------------------------------- Changes (by bgamari): * milestone: => 8.0.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9516#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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