Date: Mon, 6 Oct 2003 10:51:41 -0400 (EDT) From: Daniel Eischen <eischen@vigrid.com> To: sparc64@freebsd.org Cc: deischen@freebsd.org Subject: Re: Review for libpthread support Message-ID: <Pine.GSO.4.10.10310061036001.5491-100000@pcnet5.pcnet.com> In-Reply-To: <200310051625.04587.jake@locore.ca>
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On Sun, 5 Oct 2003, Jake Burkholder wrote:
> On Sunday 05 October 2003 13:46, Daniel Eischen wrote:
> > What if a thread gets interrupted while using locals? _thr_setcontext()
> > is suppose to be able to resume a thread that was interrupted anywhere.
> > What if some library function used locals, thread T1 had a page
> > fault, and it's context was exported back to libpthread? The
> > library may run other threads before resuming T1 again.
>
> They're part of T1's context. They'll get saved on T1's stack on entry to the
> kernel to handle the page fault.
One other question. _thr_getcontext() and _thr_setcontext() are similar
to setjmp/longjmp in that _thr_getcontext() has to return 0 when it is
called normally, and 1 when it returns as a result of a _thr_setcontext()
to the saved context.
What register holds the return value for a function? Is it %o0?
And where is this stored in the context? I don't think that the
same method as used for setjmp/longjmp can be used here because
_thr_setcontext() has to be able to return to a context that
was interrupted, not only a context that was generated by
_thr_getcontext() -- so you can't always set the return register
in _thr_setcontext().
The other archs store 1 for the return register in the saved context
and then clear it before returning. A thr_setcontext() just loads
the return register to what has been saved in the context.
So far we have:
ENTRY(__thr_getcontext)
add %o7, 8, %o1
add %o1, 4, %o2
stx %sp, [%o0 + MC_OUT + (6 * 8)]
stx %o1, [%o0 + MC_TPC]
stx %o2, [%o0 + MC_TNPC]
retl
clr %o0 /* ??? */
END(__thr_getcontext)
.weak CNAME(_thr_setcontext)
.set CNAME(_thr_setcontext),CNAME(__thr_setcontext)
ENTRY(__thr_setcontext)
save %sp, -CCFSZ, %sp
flushw
mov %i0, %l0
mov %i1, %l1
mov %i2, %l2
ldx [%l0 + MC_GLOBAL + (1 * 8)], %g1
ldx [%l0 + MC_GLOBAL + (2 * 8)], %g2
ldx [%l0 + MC_GLOBAL + (3 * 8)], %g3
ldx [%l0 + MC_GLOBAL + (4 * 8)], %g4
ldx [%l0 + MC_GLOBAL + (5 * 8)], %g5
ldx [%l0 + MC_GLOBAL + (6 * 8)], %g6
ldx [%l0 + MC_GLOBAL + (7 * 8)], %g7
ldx [%l0 + MC_OUT + (0 * 8)], %i0
ldx [%l0 + MC_OUT + (3 * 8)], %i3
ldx [%l0 + MC_OUT + (4 * 8)], %i4
ldx [%l0 + MC_OUT + (5 * 8)], %i5
ldx [%l0 + MC_OUT + (6 * 8)], %i6
ldx [%l0 + MC_OUT + (7 * 8)], %i7
ldx [%l0 + MC_TPC], %l4
ldx [%l0 + MC_TNPC], %l3
brz %l1, 1f
nop
stx %l1, [%l2]
1: jmpl %l3, %g0
return %l4
END(__thr_setcontext)
Thanks,
--
Dan Eischen
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