On Fri, 2020-05-15 at 16:50 +1000, Nicholas Piggin wrote: > > But what about if there are (real, not speculative) stores in the > store > queue still on the lazy thread from when it was switched, that have > not > yet become coherent? The page is freed by another CPU and reallocated > for something that maps it as nocache. Do you have a coherency > problem > there? > > Ensuring the store queue is drained when switching to lazy seems like > it > would fix it, maybe context switch code does that already or you > have > some other trick or reason it's not a problem. Am I way off base > here?
On x86, all stores become visible in-order globally. I suspect that means any pending stores in the queue would become visible to the rest of the system before the store to the "current" cpu-local variable, as well as other writes from the context switch code become visible to the rest of the system. Is that too naive a way of preventing the scenario you describe? What am I overlooking? -- All Rights Reversed.
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