On 08/08/2012 04:49 PM, Paolo Bonzini wrote: > Il 08/08/2012 15:32, Peter Maydell ha scritto: >>> > 1. GCC atomics look ugly, :) do not provide rmb/wmb, and in some >>> > versions of GCC mb is known to be (wrongly) a no-op. >>> > >>> > 2. glib atomics do not provide mb/rmb/wmb either, and >>> > g_atomic_int_get/g_atomic_int_set are inefficient: they add barriers >>> > everywhere, while it is clearer if you put barriers manually, and you >>> > often do not need barriers in the get side. glib atomics also do not >>> > provide xchg. >> These are arguments in favour of "don't try to use atomic ops" -- >> if serious large projects like GCC and glib can't produce working >> efficient implementations for all target architectures, what chance >> do we have? > > Well, maybe... but the flaws in both GCC and glib are small in size > (even though large in importance, at least for us) and we can work > around them easily. mb/rmb/wmb is essentially the small set of atomic > operations that we're already using.
We can easily define rmb()/wmb() to be __sync_synchronize() as a default, and only override them where it matters. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
