[m-rev.] For review: Improvments to Stack Segments code.

Julien Fischer juliensf at csse.unimelb.edu.au
Wed Apr 6 01:32:42 AEST 2011

On Tue, 5 Apr 2011, Paul Bone wrote:

> On Tue, Apr 05, 2011 at 06:54:03PM +1000, Julien Fischer wrote:
>> On Tue, 5 Apr 2011, Paul Bone wrote:
>>> On Tue, Apr 05, 2011 at 01:41:24AM +1000, Julien Fischer wrote:
>>>> On Mon, 4 Apr 2011, Paul Bone wrote:
>>>>> On Fri, Feb 25, 2011 at 03:38:45PM +1100, Julien Fischer wrote:
>>>>>> On Fri, 25 Feb 2011, Julien Fischer wrote:
>>>>>>> hlc.par.gc.trseg is is broken, the `bounds_inconsistent' test
>>>>>>> with parameter 10000000, appears to go into a loop (possibly it
>>>>>>> deadlocks?)
>>>>>> Same thing for asm_fast.par.gc.trseg.
>>>>> Is this a G12 test?
>>>> Yes, it's part of the G12's FD solver benchmarks.
>>>> (MarkB or Sebastian should be able to point you in direction of
>>>> that particular test case; fortunately it's relatively self-contained.)
>>> Okay I think I've found the problem.
>>> Foreign C code is used to create trail entries, that code is not annotated with
>>> the thread_safe attribute.  A trail entry that would cause the trail to expand
>>> and a new trail segment to be allocated uses Mercury's global lock to determine
>>> the offset for that trail.  This lock has already been aquired by the current
>>> thread and is no reenterant.  The thread is deadlocked.  This may have been a
>>> problem before I modified the memory zones code.
>>> I've replaced the use of the global lock with a CAS loop, I'm testing it now.
>> In which grade is the foreign code not annotated with a thread_safe
>> attrbute?  (For hlc.gc.trseg.par both the library trail ops, in
>> library/private_builtin.m, and the inline versions, in
>> compiler/add_trail_ops.m, do appear to be annotated with thread_safe
>> attributes.)
> set_max_attr_2 and friends in fd.rep.m in g12/solvers/fd

Ah, it was the G12 code that wasn't setting thread safe attribute; I
thought you were referring to the Mercury runtime code.

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