Re: [GHC] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF +--- Reporter: jpet | Owner: simonpj Type: bug| Status: closed Priority: normal | Milestone: 6.12.2 Component: Compiler |Version: 6.10.4 Resolution: fixed | Keywords: Difficulty: | Os: Windows Testcase: | Architecture: x86 Failure: Runtime crash | +--- Changes (by igloo): * status: new = closed * resolution: = fixed Comment: Merged. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#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] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF +--- Reporter: jpet | Owner: simonpj Type: bug| Status: reopened Priority: normal | Milestone: 6.12.2 Component: Compiler |Version: 6.10.4 Resolution: | Keywords: Difficulty: | Os: Windows Testcase: | Architecture: x86 Failure: Runtime crash | +--- Changes (by igloo): * status: closed = reopened * resolution: fixed = -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#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] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF +--- Reporter: jpet | Owner: simonpj Type: bug| Status: new Priority: normal | Milestone: 6.12.2 Component: Compiler |Version: 6.10.4 Resolution: | Keywords: Difficulty: | Os: Windows Testcase: | Architecture: x86 Failure: Runtime crash | +--- Changes (by igloo): * status: reopened = new -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#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] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF +--- Reporter: jpet | Owner: simonpj Type: bug| Status: closed Priority: normal | Milestone: 6.12.2 Component: Compiler |Version: 6.10.4 Resolution: fixed | Keywords: Difficulty: | Os: Windows Testcase: | Architecture: x86 Failure: Runtime crash | +--- Changes (by simonpj): * status: new = closed * resolution: = fixed Comment: I think I checked and found that the optimiser was doing the right thing. It was only without -O that it didn't. So I'll close this. Simon -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#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] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF
+---
Reporter: jpet | Owner: simonpj
Type: bug| Status: new
Priority: normal | Milestone: 6.12.2
Component: Compiler |Version: 6.10.4
Resolution: | Keywords:
Difficulty: | Os: Windows
Testcase: | Architecture: x86
Failure: Runtime crash |
+---
Comment (by igloo):
{{{
Mon Nov 30 03:25:08 PST 2009 Simon Marlow marlo...@gmail.com
* add a test for #3677
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#comment:6
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Re: [GHC] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF
+---
Reporter: jpet | Owner: simonpj
Type: bug| Status: new
Priority: normal | Milestone: 6.12.2
Component: Compiler |Version: 6.10.4
Resolution: | Keywords:
Difficulty: | Os: Windows
Testcase: | Architecture: x86
Failure: Runtime crash |
+---
Changes (by simonmar):
* owner: = simonpj
* milestone: 6.12 branch = 6.12.2
Comment:
Fixed the RTS bit:
{{{
Wed Nov 25 04:59:17 PST 2009 Simon Marlow marlo...@gmail.com
* threadStackOverflow: check whether stack squeezing released some stack
(#3677)
In a stack overflow situation, stack squeezing may reduce the stack
size, but we don't know whether it has been reduced enough for the
stack check to succeed if we try again. Fortunately stack squeezing
is idempotent, so all we need to do is record whether *any* squeezing
happened. If we are at the stack's absolute -K limit, and stack
squeezing happened, then we try running the thread again.
We also want to avoid enlarging the stack if squeezing has already
released some of it. However, we don't want to get into a
pathalogical situation where a thread has a nearly full stack (near
its current limit, but not near the absolute -K limit), keeps
allocating a little bit, squeezing removes a little bit, and then it
runs again. So to avoid this, if we squeezed *and* there is still
less than BLOCK_SIZE_W words free, then we enlarge the stack anyway.
M ./includes/rts/Constants.h +7
M ./rts/Schedule.c -1 +31
M ./rts/ThreadPaused.c +5
}}}
Ian: please merge.
Simon PJ will investigate whether any simplifier changes are needed here.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#comment:5
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Re: [GHC] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF
+---
Reporter: jpet | Owner:
Type: bug| Status: new
Priority: normal | Milestone: 6.12 branch
Component: Compiler |Version: 6.10.4
Resolution: | Keywords:
Difficulty: | Os: Windows
Testcase: | Architecture: x86
Failure: Runtime crash |
+---
Comment (by simonpj):
Nice report, thanks. Here is a totally self-contained example:
{{{
module Main(main) where
main = mapM_ print (edi 0)
edi :: Integer - [Integer]
edi x | x `mod` 1000 == 0 = x : edi (x+1)
| otherwise = edi (x+1)
edi2 :: Integer - [Integer]
edi2 x | x `mod` 1000 == 0 = x : y
| otherwise = y
where
y = edi2 (x+1)
}}}
Works in a 1k stack with `edi`, but needs 95k for `edi2`.
Two bugs here:
* Stack squeezing isn't working right (Simon M will investigate)
* The optimiser should probably convert one into the other anyway (Simon
PJ will look)
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#comment:4
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Re: [GHC] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF
+---
Reporter: jpet | Owner:
Type: bug| Status: new
Priority: normal | Milestone:
Component: Compiler |Version: 6.10.4
Resolution: | Keywords:
Difficulty: | Os: Windows
Testcase: | Architecture: x86
Failure: Runtime crash |
+---
Changes (by igloo):
* difficulty: =
Old description:
The following code creates a stack overflow at -O1 or -O2, when running
with a moderately small stack (+RTS -K94k):
import Data.Bits
hmm :: [Integer]
hmm = filter (\n - (n .. (n-1))==0) [1..]
main = mapM_ print hmm
The lambda just picks out powers of two, so that filter will skip
increasingly long subsequences. It's the filter causing the overflow.
Changing hmm to [Int], or to be let-bound, or compiling with -O0 makes
the overflow go away. Using a 95k stack also makes the overflow go away.
(Below 95k, stack usage is linear with the length of the filtered-out
subsequence; then it seems to cap out.)
New description:
The following code creates a stack overflow at -O1 or -O2, when running
with a moderately small stack (+RTS -K94k):
{{{
import Data.Bits
hmm :: [Integer]
hmm = filter (\n - (n .. (n-1))==0) [1..]
main = mapM_ print hmm
}}}
The lambda just picks out powers of two, so that filter will skip
increasingly long subsequences. It's the filter causing the overflow.
Changing hmm to [Int], or to be let-bound, or compiling with -O0 makes the
overflow go away. Using a 95k stack also makes the overflow go away.
(Below 95k, stack usage is linear with the length of the filtered-out
subsequence; then it seems to cap out.)
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#comment:2
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Re: [GHC] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF +--- Reporter: jpet | Owner: Type: bug| Status: new Priority: normal | Milestone: 6.12 branch Component: Compiler |Version: 6.10.4 Resolution: | Keywords: Difficulty: | Os: Windows Testcase: | Architecture: x86 Failure: Runtime crash | +--- Changes (by igloo): * milestone: = 6.12 branch Comment: Thanks for the report. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#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] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF
-+--
Reporter: jpet | Owner:
Type: bug | Status: new
Priority: normal| Milestone:
Component: Compiler | Version: 6.10.4
Resolution:|Keywords:
Os: Windows |Testcase:
Architecture: x86 | Failure: Runtime crash
-+--
Comment (by jpet):
An even simpler repro:
{{{
x :: [Integer]
x = filter (\n - n `mod` 1000 == 0) [0..]
main = mapM_ print x
}}}
Interestingly, 94k seems to be the magic stack threshold again, and in all
the other simple variations I tried.
The reason I was using such a small stack in the first place was to try to
narrow down the stack overflow in the attached program, which overflows
even an 8M stack. I'm not sure if that program is crashing because of the
same issue, but I notice that using a replacement 'filter' makes the
overflow go away:
{{{
filter' f (x:xs) = case (f x) of
True - x : (filter' f xs)
False - filter' f xs
}}}
As does compiling with -O0. So I suspect it is a variation on the same
problem.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677#comment:1
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[GHC] #3677: Optimizer creates stack overflow on filtered CAF
#3677: Optimizer creates stack overflow on filtered CAF +--- Reporter: jpet | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 6.10.4 |Keywords: Os: Windows |Testcase: Architecture: x86 | Failure: Runtime crash +--- The following code creates a stack overflow at -O1 or -O2, when running with a moderately small stack (+RTS -K94k): import Data.Bits hmm :: [Integer] hmm = filter (\n - (n .. (n-1))==0) [1..] main = mapM_ print hmm The lambda just picks out powers of two, so that filter will skip increasingly long subsequences. It's the filter causing the overflow. Changing hmm to [Int], or to be let-bound, or compiling with -O0 makes the overflow go away. Using a 95k stack also makes the overflow go away. (Below 95k, stack usage is linear with the length of the filtered-out subsequence; then it seems to cap out.) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/3677 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
