On 2021-10-07 10:53:03 [-0700], Eric Biggers wrote: > On Thu, Oct 07, 2021 at 11:42:24AM +0200, Sebastian Andrzej Siewior wrote: > > An alternative might be to move the whole test into a kworker which is > > bound to a specific CPU. So even without disabling preemption/ migration > > the per-CPU pointer would remain stable. > > > > It's only individual test cases that need to use the SIMD disabled flag, not the > whole test. An algorithm test could involve 100 test cases, any subset of which > use the SIMD disabled flag and the others don't. So the assumption is that this > can be a relatively fine-grained knob. Executing different individual test > cases on different threads sounds painful. Your simple change to use > migrate_disable() looks much better, but I'm not sure how to reconcile that with > the claim that migrate_disable() is a temporary workaround. Now that you bring it up, I was under the impression that the "SIMD-disabled" flag is only changed by the tcrypt module not by the individual tests which are performed at the algorithm lookup time. If it is the latter than yes, it will be painful. If it is just tcrypt then you could wrap the whole test-suite (at module init's time) into the kworker and bind it to one CPU). Maybe Peter can bring light into the temporary workaround but it does look like simplest thing here. > - Eric Sebastian
