"Maciej W. Rozycki" wrote:
> On Fri, 25 May 2001, Jun Sun wrote:
> > Alright, I rolled my sleeve and digged into IRIX 6.5, and guess what?
> > sysmips() does NOT have MIPS_ATOMIC_SET (2001) on IRIX! See the header
> > below.
> I remember Ralf writing of this being a compatibility call with RISC/OS
> (is it the original OS of MIPS, Inc.?), IIRC. Ralf: am I right?
> > So apparently MIPS_ATOMIC_SET was invented for Linux only, probably just to
> > implement _test_and_set(). (It would be interesting to see how IRIX
> > implement
> > _test_and_set() on MIPS I machines. However, the machine I have access uses
> > ll/sc instructions).
> Does IRIX actually run on anything below ISA II?
I assume nobody answering the above questions means nobody really care. So we
can safely move ahead without worrying about them. :-)
> > To me, either 1.a) or 2) is fine with me, although I have a slight faovr
> > over
> > 2) (perhaps because I don't like assembly code and the extra "vertical"
> > calling layer introduced in 1.a)
> What about 3) -- a new syscall with a different semantics and no need to
> care about limitations of current implementations (especially the
> sysmips() bag).
Having a new syscall is fine with me, although seems a little more instrusive
than adding a subcall to sysmips().
> I've just sent a proposal for discussion. I'm looking
> forward for constructive feedback.
The patch looks good to me.
BTW, why wouldn't you choose to have three arguments in the syscall, where the
last one is a pointer to the variable to hold the return value? Doing that
would avoid tricky register manipulation on both calling side (fetching return
value from $v1) and kernel side (setting regs.regs).