* Mathieu Desnoyers: > Now we need to discuss how we introduce that fix in a way that will > allow user-space to trust the __rseq_abi.cpu_id field's content. I don't think that's necessary. We can mention it in the glibc distribution notes on the wiki. > The usual approach to kernel bug fixing is typically to push the fix, > mark it for stable kernels, and expect everyone to pick up the > fixes. I wonder how comfortable glibc would be to replace its > sched_getcpu implementation with a broken-until-fixed kernel rseq > implementation without any mechanism in place to know whether it can > trust the value of the cpu_id field. I am extremely reluctant to do > so. We have already had similar regressions in sched_getcpu, and we didn't put anything into glibc to deal with those. Just queue the fix for the stable kernels. I expect that all distributions track stable kernel branches in some way, so just put into the kernel commit message that this commit is needed for a working sched_getcpu in glibc 2.32 and later. Once the upstream fix is in Linus' tree, I'm going to file a request to backport the fix into the Red Hat Enterprise Linux 8. Thanks for finding the root cause so quickly, Florian
