RE: sigsetjmp & sigaction survey

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From: Parmelan, Edouard (EP510777@exchange.FRANCE.NCR.com)
Date: Fri Jan 29 1999 - 08:36:56 EST


Godmar,

I just test new jthread with sigsetjmp/siglongjmp and
it fail on NCR MP-RAS :(

1. SP_OFFSET is not the same for jmp_buf and sigjmp_buf
2. sigsetjmp and siglongjmp are in fact getcontext() and
  setcontext(). These two system calls use an ucontext_t
  as parameter.

I change SP_OFFSET to point to ucontext->mc_ucontext.greg[SP],
the STACK_COPY don't SEGV, good. But reschedule() fails with
the assert (lastThread == currentJThread), not good :(

It seems that changing the value of SP in an ucontext don't
work :(

I think that jthread_create() should use an helper function
(aka in assembler language) that changes the stack, calls sigsetjmp()
in that new stack, and finaly restores the original stack.

With this behavior, jthread don't need any more the glue of SP_OFFSET
as the sigjmpbuf will save the context of the new stack.

Bad news for my last message from NCR :(

Remember, don't send comments to address @...France.NCR.COM,
I'll leaving my job at NCR France in about three hours :)

Edouard.

> -----Original Message-----
> From: Parmelan, Edouard
> Sent: Thursday, January 28, 1999 7:09 PM
> To: 'kaffe@rufus.w3.org'
> Subject: RE: sigsetjmp & sigaction survey
>
> Godmar,
>
> > Two questions:
> >
> > 1. Is anybody using kaffe on a system that does not have
sigsetjmp/siglongjmp?
> NCR MP-RAS have sigsetjmp/siglongjmp
> >
> > 2. Is anybody using kaffe on a system that does not support sigaction?
> NCR MP-RAS have sigaction
>
> > The reason I'm asking is because Pat wrote an optimized version of
> > jthreads that uses sigsetjmp and avoids saving the signal state in many
> > cases where we switch threads. On FreeBSD, this cuts thread switching
> > time from 1400 to 450 cycles, and we may be able to go down to 180
cycles,
> > as measured from Java.
> Magic :)
>
> > Now why we would optimize thread switching when the rest of kaffe
> > still sucks so much, don't ask. The answer is: research.
> The answer is: better kaffe
>
> Edouard.


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