On Tue, Jun 25, 2024 at 01:30:05PM -1000, Tejun Heo wrote: > Hello, > > On Tue, Jun 25, 2024 at 09:49:35AM +0200, Peter Zijlstra wrote: > > > Imagine a case where a sched_ext task was running but then a RT task wakes > > > up on the CPU. We'd enter the scheduling path, RT's pick_next_task() would > > > return the new RT task to run. We now need to tell the BPF scheduler that we > > > lost the CPU to the RT task but haven't called its pick_next_task() yet. > > > > Bah, I got it backwards indeed. But in this case, don't you also need > > something in pick_task() -- the whole core scheduling thing does much > > the same. > > Yes, indeed we do, but because we're dispatching from the balance path, the > cpu_acquire method is being called from there. Because who was running on > the CPU before us is less interesting, @prev is not passed into > cpu_acquire() but if that becomes necessary, it's already available there > too. I suppose I need to read more, because I'm not knowing what cpu_acquire is :/ I do know I don't much like the asymmetry here, but maybe it makes sense, dunno.
