jdenny added a comment. In D84422#2176802 <https://reviews.llvm.org/D84422#2176802>, @grokos wrote:
> In D84422#2173500 <https://reviews.llvm.org/D84422#2173500>, @jdenny wrote: > > > I've added a comment to the runtime code that performs the check. As you > > can see, the check is performed regardless. It's just a question of > > whether the runtime treats it as an error. I don't think performance is an > > issue. > > > > My concern here is that it will be hard to justify changes to the runtime > > if I cannot formulate a use case. > > > Thinking about it, I don't think there can be a case where something is > present upon entering a target region and not be present when we're exiting. > Whatever code comprises the target region is code executed on the device - it > cannot modify the state of host objects (i.e. libomptarget) in any possible > way. E.g. the kernel cannot invoke libomptarget functions, allocate memory, > map/unmap data etc. > > The only case where something like this would be possible is if we have > multiple host threads executing async offloading. In such a case, one thread > may launch a target region at a moment when the requested mapping is > `present` on the device and while the kernel is executing some other thread > performs a `target data exit` on the desired mapping. Upon exiting the > kernel, the mapping will no longer be present but this is clearly a race > condition (user's fault), so I don't think we should pay attention to such a > scenario. Exactly. As far as I can tell, the runtime simply needs a comment that explains this issue in the case of `omp target`. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D84422/new/ https://reviews.llvm.org/D84422 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
