On Sun, 2024-10-13 at 12:14 +0200, Le Chaudron Nautique wrote: > Thanks a lot. > > I think the chrt command is the one I was missing. > > I will try to set this up on a raspberry Pi 4b, with the current 6.12 > kernel, and maybe later move it to a more robust device if necessary. > > The major difficulty I have in my understanding, is sometimes the limit > between userspace and kernel : > > I would believe pthread is for userspace and kthread for kernel ? And > the management of pthread would be done by sched fonctions, that of > kthread with chrt ? chrt is just a command-line tool that calls the sched functions. The type of thread doesn't matter. > And kthreads are seen as "tasks" with ps where pthread won't be seen, > only the main process ? Only because there's no kernel "process" to group them under. You can see all threads in ps with the H option. > As for the interrupts priorities, the top-half will be 50, but I would > still be able to use a different priority for the bottom half if I use > threaded irqs ? Bottom halves aren't individual threads, so you can't set that kind of priority. The bottom half should typically run in the IRQ thread that raised it, though it could also run in ksoftirqd. If you're writing this driver, it's better to avoid bottom halves entirely, and use other mechanisms such as workqueues or kthreads to defer work. -Crystal
