"Maciej W. Rozycki" wrote: > > 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. > Sure - but with ll/sc available the user programs don't need to issue sysmip(MIPS_ATOMIC_SET,...) at the first place ... > > 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. > Where can I find the definitino of atomic_op()? Or can you tell us a little more about it? > > 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. > I notice that. I notice glibc is the only "customer" of the MIPS_SET_ATOMIC call, the bug does not appear to be a big deal because error should not happen. Of course, it will be nice to fix it. Jun
