GHC 6.4.3 is stalled

[Gregory Wright]

Dear Simon,

Some data and a few questions:

1. The failure on FreeBSD is not the same as on OS X.  I built 6.4.2
from cvs on FreeBSD 6.1, and ran the ghc-regress tests. The tests
took a long time to run (about 14 hours on a dual Xeon 2.8 GHz
with 2 GB of memory). Towards the end of the tests, there were
about 30 "timeout" processes running, apparently doing nothing
but consuming cpu cycles.

However, there were only 47 expected failures, about what I had
expected.  This is quite different from the situation on OS X, where
6.4.2 with the threaded RTS generates about 400 unexpected
failures and about two dozen compiler crashes logged by CrashReporter.

This is slightly unfortunate, since it means that the underlying bug
is probably not the same on the two operating systems.

2. Notes on reproducing the FreeBSD 6.4.2 build:  I used

	fpconfig from the ghc-6-4 branch;
	ghc, libraries, hslibs and testsuite from the ghc-6-4-2 branch;
	gnu make 3.80;
	autoconf 2.59.

Gnu make 3.81 went into an infinite loop, much as gnu make 3.79
did when building ghc on OS X.

3. Did the threaded RTS work on 6.4.1?  Was it used by default?
It would be very helpful to know.   I have built ghc 6.4.2 with  
debugging
turned on using the instructions in the commentary, but haven't gotten
a useful traceback after a crash.

I can provide an RTS thread listing (+RTS -Ds) if that would be a  
starting
point.  Someone would have to explain what it means to me, though.

4. When running with debugging turned on, I have seen the assertion  
failure

ghc-6.4.2: internal error: ASSERTION FAILED: file GC.c, line 4356
     Please report this as a compiler bug.  See:
     http://www.haskell.org/ghc/reportabug

This points toward the stack being corrupted.  Maybe a thread  
overflowing
its stack?  I'm not sure.  The assertion that fails is

     ASSERT(frame < bottom);

It looks as if something has messed up the stack before this.


I am willing to dig into this, but I need a bit more help with where  
to start.


Best Wishes,
Greg



On Jul 25, 2006, at 6:50 AM, Simon Peyton-Jones wrote:

> Folks
>
> GHC 6.4.2's threaded runtime system does not work right on
> 	Solaris
> 	MacOSX
> 	Possibly FreeBSD
>
> We'd love to fix these bugs and release 6.4.3, but we are stalled
> because we don't have easy access to these platforms, nor do we have
> detailed expertise in their intimate details (which is where the bugs
> will be lurking).
>
> If you care about these platforms, would you like to lend a hand?  We
> probably need more help than simply "here's access to the  
> platform", but
> we'd give you very strong support if you were willing to look into it.
>
> Failing that, I think we'll have to stick with 6.4.2.  (And the same
> bugs may well show up in GHC 6.6, which we hope to release before  
> ICFP.)
>
> Simon
>
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