On Wed, Oct 07, 2020 at 10:11:07AM -0700, Paul E. McKenney wrote: > Challenges include: > > o Unmarked accesses. Compilers are quite aggressive about > moving normal code.
Which is why this thread exists :-) We wants to dis-allow lifting the stores over our volatile-if. > o Separately compiled code. For example, does the compiler have > unfortunatel optimization opportunities when "volatile if" > appears in one translation unit and the dependent stores in > some other translation unit? It can hardly lift anything outside a TU (barring the next point). So I don't see how it can go wrong here. This is in fact the case with the perf ringbuffer. The ctrl-dep lives in a different TU from the stores. > o LTO, as has already been mentioned in this thread. So I would probably advocate the volatile-if to be a full sync point, and LTO would have to preserve that.
