Le Fri, Jul 10, 2026 at 11:28:18AM +0800, Jing Wu a écrit : > When kernel-noise isolation is requested for a CPU at runtime via a > cpuset isolated partition, tick suppression must be activated on the > affected CPU without requiring nohz_full= at boot. > > tick_nohz_full_mask and tick_nohz_full_running are currently set only > during boot by tick_nohz_full_setup(). There is no runtime path to add > or remove CPUs from the full-dynticks set. > > Add tick_nohz_cpu_isolate() and tick_nohz_cpu_deisolate(), both called > with the target CPU offline (between remove_cpu and add_cpu in the > hotplug cycling path): > > tick_nohz_cpu_isolate(cpu) - lazily allocates tick_nohz_full_mask > if it was never set up at boot, sets the CPU's bit in the mask, > sets tick_nohz_full_running, and calls ct_cpu_track_user() to > activate per-CPU context tracking so kernel/user transitions > suppress the scheduler tick. > > tick_nohz_cpu_deisolate(cpu) - reverses the above: deactivates > context tracking via ct_cpu_untrack_user(), clears the CPU's bit, > and clears tick_nohz_full_running when the mask becomes empty. > > A per-function mutex guards the lazy allocation and running flag > updates against concurrent isolation requests. > > Co-developed-by: Qiliang Yuan <[email protected]> > Signed-off-by: Qiliang Yuan <[email protected]> > Signed-off-by: Jing Wu <[email protected]> > --- > include/linux/tick.h | 4 ++++ > kernel/time/tick-sched.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
tick_nohz_full_running is essentially a duplicate of ~housekeeping_cpumask(HK_TYPE_KERNEL_NOISE) and tick_nohz_full_running a duplicate of housekeeping_enabled(HK_TYPE_KERNEL_NOISE). Perhaps those two variables should be removed? Thanks. -- Frederic Weisbecker SUSE Labs
