On Mon, May 28, 2018 at 08:59:32AM -0700, Paul Burton wrote: > I agree userspace shouldn't need to care about this but in my case > (using the test program I linked from the previous patch) this triggers > whilst the CPU is being brought online, not taken offline. That means > migrate_tasks() is not involved, and we actually just return from here > back out from a sched_setaffinity syscall & continue running the user > task on a CPU that is no longer present in the task's cpus_allowed. > > I can't think of a good qualifier to limit the warning to only trigger > in that scenario though, so in reality perhaps we're best to just trust > that with patch 1 applied the problem will go away.
Yeah, I'm struggling too.. re-taking task_rq_lock and testing if task_cpu(p) is inside it's own cpus_allowed (which at that time might be different from new_mask) might be the best we can do, but it is fairly expensive for a sanity check.
