on 17/05/2011 18:51 John Baldwin said the following: > On Tuesday, May 17, 2011 10:34:41 am Andriy Gapon wrote: >> on 17/05/2011 16:58 John Baldwin said the following: >>> No, it doesn't quite work that way. It wouldn't work on Alpha for example. >>> >>> All load_acq is a load with a memory barrier to order other loads after it. >>> It is still free to load stale data. Only a read-modify-write operation >>> would actually block until it could access an up-to-date value. >> >> Hmm, ok. >> How about atomic_add_acq_int(&smp_rv_waiters[0], 0) ? :-) >> Or an equivalent MI action that doesn't actually change smp_rv_waiters[0] >> value, >> if there could be any. >> Maybe explicit atomic_cmpset_acq_int(&smp_rv_waiters[0], 0, 0) ? >> >> You see at what I am getting? > > Yeah, either of those would work. At this point just leaving the > atomic_add_int() as-is would be the smallest diff. :)
Yes, I agree about the smallest diff. But if we are going to remove that first spin-loop, then we would effectively be wasting one volatile variable. Only a tiny waste, but it could be confusing. Whatever we decide, this was very educational for me. -- Andriy Gapon _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
