Request for approval: 6929067: Stack guard pages should be removed when thread is detached

[Andrew Haley]

On 08/19/2010 12:41 AM, David Holmes wrote:
> Andrew Haley said the following on 08/17/10 18:14:
>> On 08/16/2010 11:57 PM, David Holmes wrote:
>>> Andrew Haley said the following on 08/16/10 18:42:
>>>> On 08/16/2010 03:46 AM, David Holmes wrote:
>>>>> Looking further into this, isn't the only thread that can be
>>>>> affected by
>>>>> this the main thread? So we could perform this only if
>>>>> os::is_initial_thread() returns true?
>>>> I suppose we could, yes.  I wonder if it'd be a latent bug to assume
>>>> that Java threads could never use growable mappings, though.  Doing
>>>> this makes the system a bit less robust.
>>> As I understand it neither LinuxThreads nor NPTL have used growable
>>> mappings for a very long time. Even if there were a reason to go back to
>>> this it would have to be done in a compatible way and so there would be
>>> time to "enhance" the VM to accommodate it.
>>
>> Oh, I'm sure there would.  The problem is that this bug is very
>> subtle, and if it came back again it would be just as hard to
>> diagnose.  If the change to use growable mappings were made upstream
>> on some platform, would we notice?
> 
> I would hope (and I know hopes can be dashed) that the upstream
> maintainers would not make such a change silently.
> 
> Was there a regression test created for this bug? That would catch any
> change.

Yes there was, and it was attached to the very first message in this thread.

It was never checked in to the source tree, though, and I'm not sure it's
in a suitable form for the regression test suite.

Andrew.