On 16 Oct 2014, at 14:41, Mateusz Guzik <mjgu...@gmail.com> wrote: > Well, atomic_set can be as simple as v->counter = i; (which btw will > make it look identical to linux version). This should not give any > measureable effect unless atomic_set on given var is abused quite a lot.
v->counter = i does not establish a happens-before relationship and so there is no guarantee that the write will be visible to other threads until something else does establish such a relationship. The compiler and CPU are both free to reorder the store at will, and to elide it. There is a reason that C11 provides atomic_store and atomic_load operations. It sounds like Linux wants the relaxed consistency model here, which *is* equivalent to v->counter = i on x86, but *will not be the same* on any weakly-ordered architecture (e.g. ARM). Given that we have a stdatomic.h in the base system, which works with all of our supported compilers, please consider using the functionality provided by the C standard to solve your exact problem. David _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
