diff options
| author | Gabriele Monaco <gmonaco@redhat.com> | 2025-11-20 15:56:51 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2025-11-20 20:17:31 +0100 |
| commit | 185bccc79797d71477e672a1b2a2b7d0325044e7 (patch) | |
| tree | 0d714c79ecb3219201bbd86b36ee089c67e24523 /kernel/sched/isolation.c | |
| parent | 22f8e41680efec63ead03d4693676587814f7a24 (diff) | |
sched/isolation: Force housekeeping if isolcpus and nohz_full don't leave any
Currently the user can set up isolcpus and nohz_full in such a way that
leaves no housekeeping CPU (i.e. no CPU that is neither domain isolated
nor nohz full). This can be a problem for other subsystems (e.g. the
timer wheel imgration).
Prevent this configuration by invalidating the last setting in case the
union of isolcpus (domain) and nohz_full covers all CPUs.
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://patch.msgid.link/20251120145653.296659-6-gmonaco@redhat.com
Diffstat (limited to 'kernel/sched/isolation.c')
| -rw-r--r-- | kernel/sched/isolation.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index a4cf17b1fab0..3ad0d6df6a0a 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -167,6 +167,29 @@ static int __init housekeeping_setup(char *str, unsigned long flags) } } + /* + * Check the combination of nohz_full and isolcpus=domain, + * necessary to avoid problems with the timer migration + * hierarchy. managed_irq is ignored by this check since it + * isn't considered in the timer migration logic. + */ + iter_flags = housekeeping.flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMAIN); + type = find_first_bit(&iter_flags, HK_TYPE_MAX); + /* + * Pass the check if none of these flags were previously set or + * are not in the current selection. + */ + iter_flags = flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMAIN); + first_cpu = (type == HK_TYPE_MAX || !iter_flags) ? 0 : + cpumask_first_and_and(cpu_present_mask, + housekeeping_staging, housekeeping.cpumasks[type]); + if (first_cpu >= min(nr_cpu_ids, setup_max_cpus)) { + pr_warn("Housekeeping: must include one present CPU " + "neither in nohz_full= nor in isolcpus=domain, " + "ignoring setting %s\n", str); + goto free_housekeeping_staging; + } + iter_flags = flags & ~housekeeping.flags; for_each_set_bit(type, &iter_flags, HK_TYPE_MAX) |