Hello, Paul. On Fri, Apr 10, 2026 at 12:17:21PM -0700, Paul E. McKenney wrote: > > The easiest way to do this is just creating the initial workers for all > > possible pools. Please see below. However, the downside is that it's going > > to create all workers for all possible cpus. This isn't a problem for > > anybody else but these IBM mainframes often come up with a lot of possible > > but not-yet-or-ever-online CPUs for capacity management, so the cost may not > > be negligible on some configurations. > > > > IBM folks, is that okay? > > I have also seen x86 systems whose firmware claimed very large numbers > of CPUs. :-(
Yeah, I remember seeing those but at least the ones I remember are from long times ago. Hopefully, no bios is getting things that wrong anymore. > > Also, why do you need to queue work items on an offline CPU? Do they > > actually have to be per-cpu? Can you get away with using an unbound > > workqueue? > > It is good for them to run on the specified CPU in the common case for > cache-locality reasons, but if they were occasionally redirected to some > other CPU, that would be just fine. I see. > I am also keeping the patch that avoids queueing work to CPUs that are not > yet fully online. Further adjustments will be needed if someone invokes > call_srcu(), synchronize_srcu(), or synchronize_srcu_expedited() from an > CPU that is not yet fully online. Past experience of course suggests that > this will be happen, and that there will be a good reason for it. ;-) I'm gonna hold for now. From workqueue side, it's a really easy change, so please let me know if this comes up again. Thanks. -- tejun
