On Tue, Jun 20 2023 at 16:02, Nicholas Piggin wrote: > On Sun Jun 11, 2023 at 5:29 AM AEST, Thomas Gleixner wrote: >> /* >> * Invoked on the outgoing CPU in context of the CPU hotplug thread >> * after ensuring that there are no user space tasks left on the CPU. >> * >> * If there is a lazy mm in use on the hotplug thread, drop it and >> * switch to init_mm. >> * >> * The reference count on init_mm is dropped in finish_cpu(). >> */ >> static void sched_force_init_mm(void) >> { >> >> No? > > It could be done in many places. Peter touched it last and it's > been in the tree since prehistoric times. That's an argument for slapping it into some randomly chosen place and be done with it, right? >> > +/* >> > + * After the CPU is offline, double check that it was previously switched to >> > + * init_mm. This call can be removed because the condition is caught in >> > + * finish_cpu() as well. >> >> So why adding it in the first place? >> >> The changelog mumbles something about reducing churn, but I fail to see >> that reduction. This adds 10 lines of pointless code and comments for >> zero value. > > Not sure what you're talking about. The patch didn't add it. Removing it > requires removing it from all archs, which is the churn. Sure. That's left as an exercise for others, right? Oh well. tglx