On Mon, 18 Dec 2000, Jun Sun wrote: > It looks like sometime after test5 the MIPS_ATOMIC_SET case in sys_sysmips() > function in the CVS tree is changed. The new code now uses ll/sc instructions > and handles syscall trace, etc.. > > This change does not make sense to me. The userland typically uses > MIPS_ATOMIC_SET when ll/sc instructions are not available. But the new code > itself uses ll/sc, which pretty much forfeit the purpose. Or do I miss > something else? There is no problem with using ll/sc in sysmips() itself for machines that support them. > What do we offer to machines without ll/sc? I asked Ralf for a clarification of the sysmips(MIPS_ATOMIC_SET, ...) call before I write better code. No response so far. I'm now really cosidering implementing the Ultrix atomic_op() syscall -- at least it has a well-known defined behaviour. > BTW, what is the wrong with previous code? I understand it may be broken in > SMP case, but I think that is fixable. Comments? The previous code was definitely broken -- depending on the path taken it would return either the value fetched from memory or an error code. No way to distinguish between them. Maciej -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
