On Wed, Jul 11, 2018 at 10:04:52AM +0000, David Laight wrote: > I also suspect that 'write starvation' is also common - after all the > purpose of the store buffer is to do reads in preference to writes in > order to reduce the cpu stalls waiting for the memory bus (probably > the cpu to cache interface). > > I think your example is just: > *(volatile int *)xxx = 1; > while (!*(volatile int *)yyy) continue; > running on two cpu with xxx and yyy swapped? Yep. And Linux has been relying on that working for (afaict) basically forever. > You need a stronger bus cycle in there somewhere. Since all spin-wait loops _should_ have cpu_relax() that is the natural place to put it.
