Re: sysmips call and glibc atomic set

From: Maciej W. Rozycki (
Date: Thu Dec 28 2000 - 07:06:59 EST

On Tue, 26 Dec 2000, Ralf Baechle wrote:

> The semantics of this syscall were previously defined by Risc/OS and later
> on continued to be used by IRIX.

 Ralf, could you please provide me a copy of a man page for the call? I
don't have access to either of the systems and a search of the Net
returned nothing.

> Don't think about SMP without ll/sc. There's algorithems available for
> that but their complexity leaves them a unpractical, theoretical construct.

 For SMP there is a simple kernel solution available. It suitable for a
syscall or a ll/sc emulation. There is no easy userland-only solution

> Above code will break if the old content of memory has bit 31 set or you take
> pagefaults. The latter problem is a problem even on UP - think multi-
> threading.

 If the code is written carefully you don't ever get a pagefault that
would break consistency.

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail:, PGP key available        +

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