#9292: Race condition when multiple threads wait for a process
-------------------------------------+-------------------------------------
Reporter: snoyberg | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: libraries/process | Version: 7.8.2
Keywords: | Operating System: Unknown/Multiple
Architecture: Unknown/Multiple | Type of failure: None/Unknown
Difficulty: Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: |
-------------------------------------+-------------------------------------
Consider the following code:
{{{
import System.Process
import Control.Concurrent.Async
main :: IO ()
main = do
(_, _, _, ph) <- createProcess $ shell "sleep 1"
let helper i = do
ec <- waitForProcess ph
print (i :: Int, ec)
((), ()) <- concurrently (helper 1) (helper 2)
return ()
}}}
If I compile with the single threaded runtime, I get the output
{{{
(2,ExitSuccess)
(1,ExitSuccess)
}}}
But when compiling with the multithreaded runtime, I get:
{{{
bin: waitForProcess: does not exist (No child processes)
}}}
If you need to wait for a process from multiple threads, you can do so now
by having a dedicated wait thread which writes to an MVar or TMVar, but
the current default behavior can be surprising.
I discussed this in a [http://www.yesodweb.com/blog/2014/07/rfc-new-data-
conduit-process blog post], and there was some
[http://www.reddit.com/r/haskell/comments/2abmwu/rfc_new_dataconduitprocess/…
conversation on Reddit].
At the least, I think we need better documentation, but if there's a
better solution, that would be best.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9292>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
#7828: RebindableSyntax and Arrow
----------------------------------------------+----------------------------
Reporter: AlessandroVermeulen | Owner:
Type: bug | jstolarek
Priority: normal | Status: new
Component: Compiler (Type checker) | Milestone: 7.10.1
Resolution: | Version: 7.6.2
Operating System: Unknown/Multiple | Keywords:
Type of failure: GHC rejects valid program | Architecture:
Test Case: | Unknown/Multiple
Blocking: | Difficulty: Unknown
| Blocked By:
| Related Tickets: #1537,
| #3613
----------------------------------------------+----------------------------
Comment (by jstolarek):
I have made some progress on this one today. I'm able to compile
{{{
test :: Arrow a => a i i
test = proc n -> do
returnA -< n
}}}
using the new desugaring, which was not possible earlier. But I'm still
stuck on this:
{{{
test :: Arrow a => a i i
test = proc n -> do
returnA -< n
returnA -< n
}}}
ie. desugaring of `thenA` although now I have gathered more information.
With my new implementation the code above desugars to:
{{{
(>>>) @ i @ (i, ()) @ i
(arr @ i @ (i, ()) (\ (n :: i) -> (n, ())))
(thenA @ arrow @ i @ (GHC.Prim.Any *) @ (GHC.Prim.Any *) @ i $dArrow_auX
((>>>) @ (i, ()) @ i @ i
(arr @ (i, ()) @ i
(\ (ds2 :: (i, ())) ->
case ds2 of _ { (ds4, ds5) -> ds4 }))
(Control.Arrow.returnA @ arrow @ i $dArrow_auX))
((>>>) @ (i, ()) @ i @ i
(arr @ (i, ()) @ i
(\ (ds2 :: (i, ())) ->
case ds2 of _ { (ds4, ds5) -> ds4 }))
(Control.Arrow.returnA @ arrow @ i $dArrow_auX)))
}}}
This looks correct except for the two `(GHC.Prim.Any *)` type parameters
to `thenA`. One corresponds to the type of the stack, the other to result
of first command (`b` in the type signature `a (e,s) b -> a (e,s) c -> a
(e,s) c`). `thenA` should be polymorphic in these, but it seems that
during typechecking I need to instantiate `s` and `b` to concrete values.
I noticed that desugaring of `cmd` stored in the `BodyStmt` always passes
`()` as the type of the stack. If this is correct then there's only the
problem of what to do with `b`. Help needed here becuase I have no idea
how to figure out the type of `b` from within `tcArrDoStmt`.
Ross, I also tried to implement desugaring of `bind`. When generating the
desugared Core for `cmd 'bind' \ p -> do { ss }` I have problem with the
`\p ->` part. So, given the desugared `do { ss }`, `cmd` and the `bind`
operator how should the generated command lambda look like? I'm still at a
loss to undestand how to explicitly manipulate the stack from within Core.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7828#comment:42>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
#284: RPM doesn't support --prefix
-------------------------------------+------------------------------------
Reporter: skaller | Owner: juhp
Type: feature request | Status: new
Priority: normal | Milestone: ⊥
Component: Build System | Version: None
Resolution: None | Keywords:
Operating System: Unknown/Multiple | Architecture: Unknown/Multiple
Type of failure: None/Unknown | Difficulty: Unknown
Test Case: N/A | Blocked By:
Blocking: | Related Tickets:
-------------------------------------+------------------------------------
Comment (by ydewit):
This is what I see with {{{otool -L}}}:
{{{
/t/g/l/g/array-0.5.0.0 ❯❯❯ otool -L
libHSarray-0.5.0.0-ghc7.9.20140709.dylib
libHSarray-0.5.0.0-ghc7.9.20140709.dylib:
@rpath/libHSarray-0.5.0.0-ghc7.9.20140709.dylib (compatibility
version 0.0.0, current version 0.0.0)
/usr/lib/libiconv.2.dylib (compatibility version 7.0.0, current
version 7.0.0)
/usr/local/lib/libgmp.10.dylib (compatibility version 13.0.0,
current version 13.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current
version 1197.1.1)
@rpath/libHSbase-4.7.1.0-ghc7.9.20140709.dylib (compatibility
version 0.0.0, current version 0.0.0)
@rpath/libHSinteger-gmp-0.5.1.0-ghc7.9.20140709.dylib
(compatibility version 0.0.0, current version 0.0.0)
@rpath/libHSghc-prim-0.3.1.0-ghc7.9.20140709.dylib (compatibility
version 0.0.0, current version 0.0.0)
}}}
My understanding is that {{{@rpath}}}, which seems to be a feature added
in 10.5, means this dylib can be relocated.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/284#comment:21>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
#9291: Best Muscle building supplement
------------------------------------+-------------------------------------
Reporter: herbertlawrence | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.8.2
Keywords: Horsepower XXL | Operating System: Unknown/Multiple
Architecture: Unknown/Multiple | Type of failure: None/Unknown
Difficulty: Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: |
------------------------------------+-------------------------------------
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--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9291>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
#284: RPM doesn't support --prefix
-------------------------------------+------------------------------------
Reporter: skaller | Owner: juhp
Type: feature request | Status: new
Priority: normal | Milestone: ⊥
Component: Build System | Version: None
Resolution: None | Keywords:
Operating System: Unknown/Multiple | Architecture: Unknown/Multiple
Type of failure: None/Unknown | Difficulty: Unknown
Test Case: N/A | Blocked By:
Blocking: | Related Tickets:
-------------------------------------+------------------------------------
Comment (by carter):
I don't think relocating is quite that simple. Eg On OS X, dylibs can't
use relative paths (last I checked), so relocating dylibs requires an
invocation of the install-name-tool to fixup the paths!
(my recollection could be totally wrong mind you)
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/284#comment:20>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
