I would vote for option #4 - make sure the ll/sc emulation stuff works and use ll/sc in glibc instead of sysmips. Beyond the pthreads mutex stuff in glibc I have yet to come across usage of sysmips. Of course you still need sys_sysmips to function correctly (in case somebody did a silly thing like call sysmips directly just for the fun of it), so I like like Florian's solution. Adding a parameter is a silly thing to do, and we don't need to be adding functionality to sys_sysmips through NEW_MO_BETTER_AS_SEEN_ON_TV_ATOMIC_SET or what have you... Joe Jun Sun wrote: > Florian Lohoff wrote: > >> On Mon, May 21, 2001 at 04:23:52PM -0700, Jun Sun wrote: >> >>> The patch seems to be just a fast implementation of sysmips(). Why would it >>> solve an otherwise illegal instruction problem? >>> >>> George, what was exactly the error and the faulty instruction? >> >> Wrong - Its not only a "fast" path sysmips. It solves the illegal instruction >> case as it carefully doesnt touch registers it should not touch. >> >> The sysmips illegal instruction stuff came from the early exit >> needed to skip the -EXXXX case in the scall32.S which did not >> restore the modified registers. This needed fixing and there was >> no clean way of doing this in C thus i wrote an asm sysmips/MIPS_ATOMIC_SET >> and called it "fast_sysmips" which itself would go into the old >> sysmips function when not MIPS_ATOMIC_SET. >> > > > I see. > > I took a look of MIPS ABI in system V and found that the spec only specifies > this extended call in C prototype: > > int _test_and_set(int *p, int v); > > It seems perfectly legal for us to add one more argument to store the return > value while still have the function returns error. Of course, doing that will > break binary compatibility. > > Otherwise, I think Flo's patch is the best fix to satisfy the spec and binary > compatibility although it is a little clunky. > > A third possibility is the have a MIPS_NEW_ATOMIC_SET that take three > arguments. If that approach is taken, I would take out the inline assembly > that jumps to o32_ret_from_sys_call and documents MIPS_ATOMIC_SET as > deprecated and valnerable. > > My preference, in the decreasing order, is 3), 2) and 1). > > Ralf, what do you think? We cannot let the bug sit around in the CVS tree for > long. Have to have some fix. > > Jun -- Joe deBlaquiere Red Hat, Inc. 307 Wynn Drive Huntsville AL, 35805 voice : (256)-704-9200 fax : (256)-837-3839
