[M3devel] Status of threads for RC4?

[Tony Hosking]

The gross fix is to have threads in blocking pthread calls to post  
their blocked status on entry.  The GC stop-world code can simply  
notice they are blocked and not try to signal them, but just set their  
status to stopping.  When the blocked thread returns from the blocking  
call it can notice the stopping state and transition to stopped,  
waiting on the stop-world semaphore.  This appears to be what the  
Kaffe VM folks do.  The unfortunate thing is that this is *totally  
unnecessary* on every other platform except OpenBSD, as far as I  
know.  We do not want to add cruft to the thread primitives just to  
support a broken user-level threads system.  Better just to revert  
OpenBSD to our own user-level ThreadPosix implementation until OpenBSD  
wakes up to the real world of SMP and multicore.

On 21 Oct 2009, at 09:38, Tony Hosking wrote:

> Precisely.  The problem is that the signal mechanism to stop thread  
> for GC is not working.  This is a bogosity of the OpenBSD user-level  
> threads implementation.  Either we configure OpenBSD to use  
> ThreadPosix instead of ThreadPThread or we switch to rthreads.
>
> On 21 Oct 2009, at 05:06, Jay K wrote:
>
>> Interesting -- Juno on Win32 also doesn't hang with @M3nogc, with  
>> over 200 runs (using @M3no-trestle-await-delete).
>>
>>  ..Jay
>>
>> > Date: Wed, 21 Oct 2009 09:21:57 +0200
>> > From: wagner at elegosoft.com
>> > To: jay.krell at cornell.edu
>> > CC: m3devel at elegosoft.com
>> > Subject: Re: [M3devel] Status of threads for RC4?
>> >
>> > Quoting Jay K <jay.krell at cornell.edu>:
>> >
>> > > Is it reasonable maybe to rewrite this test in C and see if it  
>> hangs?
>> > >
>> > > ie. see if maybe it is an OpenBSD bug?
>> >
>> > It doesn't hang with garbage collection turned off, so there must  
>> be
>> > some unhealthy interaction between that and the thread  
>> implementation.
>> > I don't think you will be able to narrow it down with a C test.
>> >
>> > Olaf
>> > --
>> > Olaf Wagner -- elego Software Solutions GmbH
>> > Gustav-Meyer-Allee 25 / Gebäude 12, 13355 Berlin, Germany
>> > phone: +49 30 23 45 86 96 mobile: +49 177 2345 869 fax: +49 30 23  
>> 45 86 95
>> > http://www.elegosoft.com | Geschäftsführer: Olaf Wagner | Sitz:  
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>> DE163214194
>> >
>

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