On Sat, 7 Apr 2001, Florian Lohoff wrote: > > You are right, of course. That's why glibc contains two versions of > > _test_and_set() code. If compiled for MIPS I, glibc uses a syscall > > (currently sysmips()), while for MIPS II and higher it uses inline > > assembly code which makes use of LL/SC. > > > > That's exactly the way glibc does CPU-model-specific code for other > > archs. > > The problem is that it is compile time - I would like to have > a runtime version - Just export the existance of ll/sc to > userspace somewhow. I can't see any problem. If you want to go for speed -- compile glibc for MIPS II (assuming you have a MIPS II or better CPU). If you want to go for compatibility -- compile glibc for MIPS I (it will still run on MIPS II or better CPUs, although suboptimally; actually, it won't be the worst suboptimality then). Similarly -- an Alpha EV56-compiled glibc will not run on an EV4 CPU, while an EV4-compiled glibc will run on an EV56 CPU, although suboptimally. > > I don't like run-time detection either. The compile-time choice is > > sufficient enough. The _test_and_set() library function already hides > > implementation details from the user. > > It isnt sufficent as we need a glibc beeing able to run on old > decstations AND on newer machines like the Lasat machine > which has an R5000. A MIPS-I-compiled glibc will run on any MIPS CPU, using a kernel _test_and_set() emulation (how kernel emulates _test_and_set() is not the point here -- it has to be done in an MP-safe way, if necessary; LL/SC is the most likely candidate for MIPS II or better kernels). A MIPS-II-compiled glibc will run on any MIPS II or better CPU using LL/SC directly. Similar for MIPS-III-compiled glibc, etc. A MIPS-II-compiled kernel will still provide a _test_and_set() emulation to keep the ABI consistent (e.g. for statically linked MIPS I binaries). Still any problems? I will happily clarify any remaining issues. -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
