Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results --+- Reporter: parcs| Owner: Type: bug | Status: closed Priority: highest | Milestone: 7.6.2 Component: Runtime System |Version: 7.6.1 Resolution: fixed| Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Changes (by igloo): * status: merge = closed * resolution: = fixed Comment: Reverted, and merged as 57c8d1c2c8ceba6973a48d138d1bb018ec2988ae -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results
--+-
Reporter: parcs| Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.6.2
Component: Runtime System |Version: 7.6.1
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Comment(by marlowsd@…):
commit a006ecdfd381fa75ab16ddb66c3a2b247f359eb8
{{{
Author: Simon Marlow marlo...@gmail.com
Date: Tue Dec 18 09:10:26 2012 +
A better fix for #7493 (see comment for details)
rts/STM.c | 64
+---
1 files changed, 44 insertions(+), 20 deletions(-)
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:9
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results
--+-
Reporter: parcs| Owner:
Type: bug | Status: merge
Priority: highest | Milestone: 7.6.2
Component: Runtime System |Version: 7.6.1
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Changes (by simonmar):
* status: new = merge
Comment:
I reverted the previous fix:
commit 55c55f141b8b312512cce1d7e0fbd3a8088de964
{{{
Author: Simon Marlow marlo...@gmail.com
Date: Tue Dec 18 08:43:29 2012 +
Revert Fix a bug in the handling of nested orElse
This reverts commit f184d9caffa09750ef6a374a7987b9213d6db28e.
The next commit will fix it in a better way.
}}}
please merge both commits.
@fryguybob, @parcs: see if you can break it again!
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:10
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results
--+-
Reporter: parcs| Owner:
Type: bug | Status: closed
Priority: highest | Milestone: 7.6.2
Component: Runtime System |Version: 7.6.1
Resolution: fixed| Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Comment(by fryguybob):
I built with the fix and for the first program I'm getting:
{{{
[True,False]
[False]
[]
[]
...
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:4
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results --+- Reporter: parcs| Owner: Type: bug | Status: new Priority: highest | Milestone: 7.6.2 Component: Runtime System |Version: 7.6.1 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Changes (by parcs): * status: closed = new * resolution: fixed = Comment: I am getting the same output as fryguybob using GHC 7.7 20121214 and STM 2.4.2. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results
--+-
Reporter: parcs| Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.6.2
Component: Runtime System |Version: 7.6.1
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Comment(by fryguybob):
I've reduced the first program to the following:
{{{
import Control.Concurrent.STM
main = do
x - atomically $ do
r - newTVar []
writeTVar r [2]
writeTVar r [] `orElse` return ()
readTVar r
print x
}}}
This outputs `[2]` when I would expect `[]`. If I use `Int`s it does not
fail and if I have different values for each of the write or new's it
works:
{{{
import Control.Concurrent.STM
main = do
x - atomically $ do
r - newTVar [1]
writeTVar r [2]
writeTVar r [1] `orElse` return ()
readTVar r
print x
}}}
Outputs: `[1]`
{{{
import Control.Concurrent.STM
main = do
x - atomically $ do
r - newTVar 1
writeTVar r 2
writeTVar r 1 `orElse` return ()
readTVar r
print x
}}}
Output: `1`
Also interesting:
{{{
import Control.Concurrent.STM
main = do
x - atomically $ do
r - newTVar Nothing
writeTVar r (Just 2)
writeTVar r Nothing `orElse` return ()
readTVar r
print x
}}}
Output: `Just 2`
I'll start digging around to see what is going on with this example.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:6
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results
--+-
Reporter: parcs| Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.6.2
Component: Runtime System |Version: 7.6.1
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Comment(by fryguybob):
I've traced down the point of divergence between a test that works and one
that does not. The following works:
{{{
import Control.Concurrent.STM
main = do
x - atomically $ do
r - newTVar 1
writeTVar r 2
writeTVar r 1 `orElse` return ()
readTVar r
print x
}}}
But if we change to:
{{{
import Control.Concurrent.STM
main = do
x - atomically $ do
let a = 1
r - newTVar a
writeTVar r 2
writeTVar r a `orElse` return ()
readTVar r
print x
}}}
Then when we try to commit the inner transaction with
`stmCommitNestedTransaction` we enter `validate_and_acquire_ownership` and
hit `entry_is_update`
([https://github.com/ghc/ghc/blob/ghc-7.6/rts/STM.c#L809 code here]) which
returns false (the current value is the exact `a` that initialized in
`newTVar`). In the one that works each `1` is a different thunk
(`Integer`, unlike `Int` I said before; using `Int` it does indeed fail).
I'm still tracking down what happens after this, but now we know the
difference between the examples.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:7
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results --+- Reporter: parcs| Owner: Type: bug | Status: new Priority: highest | Milestone: 7.6.2 Component: Runtime System |Version: 7.6.1 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Comment(by fryguybob): It looks like this particular case is not accounted for. If an outer transaction writes the inner transaction needs to compare with that value to know if it is an update, not with the originally read value (which we need for knowing if there was an update from outside). Worse yet, the write we need to see could be several levels out. Perhaps it would be better to fix it on the other side of things. If a write doesn't update, then when we `merge_read_into` if the outer record entry ''is'' an update, then we know the inner has reversed the update. But here we can't distinguish a write to match the expected value and a read (which we would not want to take as an indication that we should revert our outer update). Perhaps another approach could be to look when we do an `stmWriteTVar` to see if we are an inner transaction writing what matches the expected value. If so, built a thunk (indirection?) so we are sure to get a new value that will be seen by the outer transaction. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results --+- Reporter: parcs| Owner: Type: bug | Status: closed Priority: highest | Milestone: 7.6.2 Component: Runtime System |Version: 7.6.1 Resolution: fixed| Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Changes (by igloo): * status: merge = closed * resolution: = fixed Comment: Merged as 5ea49271f793ed0f872342bf6a1cb0de10a48d94 -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results +--- Reporter: parcs| Owner: Type: bug | Status: new Priority: normal | Component: Runtime System Version: 7.6.1| Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Blockedby: Blocking: |Related: +--- Changes (by meteficha): * cc: felipe.lessa@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7493: STM and TVar report incorrect results
#7493: STM and TVar report incorrect results
-+--
Reporter: parcs | Owner:
Type: bug | Status: merge
Priority: highest | Milestone: 7.6.2
Component: Runtime System| Version: 7.6.1
Keywords:| Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Incorrect result at runtime
Difficulty: Unknown |Testcase:
Blockedby:|Blocking:
Related:|
-+--
Changes (by simonmar):
* priority: normal = highest
* difficulty: = Unknown
* status: new = merge
* milestone: = 7.6.2
Comment:
Fixed (sorry, I didn't notice that you'd filed a ticket until just now):
commit f184d9caffa09750ef6a374a7987b9213d6db28e
{{{
Author: Simon Marlow marlo...@gmail.com
Date: Mon Dec 10 12:00:54 2012 +
Fix a bug in the handling of nested orElse
Exposed by the following snippet, courtesy of Bas van Dijk and Patrick
Palka on librar...@haskell.org:
import Control.Concurrent.STM
main = do
x - atomically $ do
t - newTVar 1
writeTVar t 2
((readTVar t retry) `orElse` return ()) `orElse` return ()
readTVar t
print x
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7493#comment:2
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
