From 79c0abaf06fca6e715cf792daed580542fc4a2c4 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 24 Jul 2025 23:38:48 +0200 Subject: sched/arm64: Move fallback task cpumask to HK_TYPE_DOMAIN When none of the allowed CPUs of a task are online, it gets migrated to the fallback cpumask which is all the non nohz_full CPUs. However just like nohz_full CPUs, domain isolated CPUs don't want to be disturbed by tasks that have lost their CPU affinities. And since nohz_full rely on domain isolation to work correctly, the housekeeping mask of domain isolated CPUs should always be a subset of the housekeeping mask of nohz_full CPUs (there can be CPUs that are domain isolated but not nohz_full, OTOH there shouldn't be nohz_full CPUs that are not domain isolated): HK_TYPE_DOMAIN & HK_TYPE_KERNEL_NOISE == HK_TYPE_DOMAIN Therefore use HK_TYPE_DOMAIN as the appropriate fallback target for tasks. Note that cpuset isolated partitions are not supported on those systems and may result in undefined behaviour. Signed-off-by: Frederic Weisbecker Reviewed-by: Waiman Long Acked-by: Will Deacon Tested-by: Will Deacon Cc: Catalin Marinas Cc: Marco Crivellari Cc: Michal Hocko Cc: Peter Zijlstra Cc: Tejun Heo Cc: Thomas Gleixner Cc: Waiman Long Cc: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org --- arch/arm64/kernel/cpufeature.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index c840a93b9ef9..f0e66cb27d17 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1669,7 +1669,7 @@ const struct cpumask *system_32bit_el0_cpumask(void) const struct cpumask *task_cpu_fallback_mask(struct task_struct *p) { - return __task_cpu_possible_mask(p, housekeeping_cpumask(HK_TYPE_TICK)); + return __task_cpu_possible_mask(p, housekeeping_cpumask(HK_TYPE_DOMAIN)); } static int __init parse_32bit_el0_param(char *str) @@ -3987,8 +3987,8 @@ static int enable_mismatched_32bit_el0(unsigned int cpu) bool cpu_32bit = false; if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) { - if (!housekeeping_cpu(cpu, HK_TYPE_TICK)) - pr_info("Treating adaptive-ticks CPU %u as 64-bit only\n", cpu); + if (!housekeeping_cpu(cpu, HK_TYPE_DOMAIN)) + pr_info("Treating domain isolated CPU %u as 64-bit only\n", cpu); else cpu_32bit = true; } -- cgit v1.2.3