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Several users in the community have reported issues with RT stalling sched_ext tasks. Add a sched_ext deadline server as well so that sched_ext tasks are also boosted and do not suffer starvation. A kselftest is also provided to verify the starvation issues are now fixed. Btw, there is still something funky going on with CPU hotplug and the relinquish patch. Sometimes the sched_ext's hotplug self-test locks up (./runner -t hotplug). Reverting that patch fixes it, so I am suspecting something is off in dl_server_remove_params() when it is being called on offline CPUs. v2->v3: - Removed code duplication in debugfs. Made ext interface separate. - Fixed issue where rq_lock_irqsave was not used in the relinquish patch. - Fixed running bw accounting issue in dl_server_remove_params. Link to v1: https://lore.kernel.org/all/20250315022158.2354454-1-joelagnelf@nvidia.com/ Link to v2: https://lore.kernel.org/all/20250602180110.816225-1-joelagnelf@nvidia.com/ Andrea Righi (1): selftests/sched_ext: Add test for sched_ext dl_server Joel Fernandes (9): sched/debug: Fix updating of ppos on server write ops sched/debug: Stop and start server based on if it was active sched/deadline: Clear the defer params sched: Add support to pick functions to take rf sched: Add a server arg to dl_server_update_idle_time() sched/ext: Add a DL server for sched_ext tasks sched/debug: Add support to change sched_ext server params sched/deadline: Add support to remove DL server bandwidth sched/ext: Relinquish DL server reservations when not needed include/linux/sched.h | 2 +- kernel/sched/core.c | 19 +- kernel/sched/deadline.c | 78 +++++-- kernel/sched/debug.c | 171 +++++++++++--- kernel/sched/ext.c | 108 ++++++++- kernel/sched/fair.c | 15 +- kernel/sched/idle.c | 4 +- kernel/sched/rt.c | 2 +- kernel/sched/sched.h | 13 +- kernel/sched/stop_task.c | 2 +- tools/testing/selftests/sched_ext/Makefile | 1 + .../selftests/sched_ext/rt_stall.bpf.c | 23 ++ tools/testing/selftests/sched_ext/rt_stall.c | 213 ++++++++++++++++++ 13 files changed, 579 insertions(+), 72 deletions(-) create mode 100644 tools/testing/selftests/sched_ext/rt_stall.bpf.c create mode 100644 tools/testing/selftests/sched_ext/rt_stall.c -- 2.34.1