Michael Schnell wrote: > >> Seemingly the best instruction to handle these bits is "atomic compare > >> and exchange" (e.g. provided by the X86 CPU). > > > > It's actually not the best, because when it returns "did not match" > > you have to loop and try again. > > The supposedly "best" user space implementation for the X86 I found (in > "Futexes are Tricky") uses both "atomic_compare_and_exchange" and > "atomic_exchange" for the lock part and "atomic_dec" for the unlock part.
That's right. It's possible to use atomic_compare_and_exchange for unlock; it's correct. But you get that extra bit of spinning with SMP, so atomic_dec is better. -- Jamie _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
