From: Alex Belits <abelits@marvell.com> mainline inclusion from mainline-v5.9-rc1 commit 1abdfe706a579a702799fce465bceb9fb01d407c category: bugfix bugzilla: 45956 CVE: NA -------------------------------- The current implementation of cpumask_local_spread() does not respect the isolated CPUs, i.e., even if a CPU has been isolated for Real-Time task, it will return it to the caller for pinning of its IRQ threads. Having these unwanted IRQ threads on an isolated CPU adds up to a latency overhead. Restrict the CPUs that are returned for spreading IRQs only to the available housekeeping CPUs. Signed-off-by: Alex Belits <abelits@marvell.com> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200625223443.2684-2-nitesh@redhat.com Signed-off-by: Liu Chao <liuchao173@huawei.com> Reviewed-by: Jian Cheng <cj.chengjian@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- lib/cpumask.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/lib/cpumask.c b/lib/cpumask.c index beca6244671a..7dde20a9faa7 100644 --- a/lib/cpumask.c +++ b/lib/cpumask.c @@ -5,6 +5,7 @@ #include <linux/cpumask.h> #include <linux/export.h> #include <linux/bootmem.h> +#include <linux/sched/isolation.h> /** * cpumask_next - get the next cpu in a cpumask @@ -201,22 +202,27 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask) */ unsigned int cpumask_local_spread(unsigned int i, int node) { - int cpu; + int cpu, hk_flags; + const struct cpumask *mask; + hk_flags = HK_FLAG_DOMAIN | HK_FLAG_MANAGED_IRQ; + mask = housekeeping_cpumask(hk_flags); /* Wrap: we always want a cpu. */ - i %= num_online_cpus(); + i %= cpumask_weight(mask); if (node == -1) { - for_each_cpu(cpu, cpu_online_mask) + for_each_cpu(cpu, mask) { if (i-- == 0) return cpu; + } } else { /* NUMA first. */ - for_each_cpu_and(cpu, cpumask_of_node(node), cpu_online_mask) + for_each_cpu_and(cpu, cpumask_of_node(node), mask) { if (i-- == 0) return cpu; + } - for_each_cpu(cpu, cpu_online_mask) { + for_each_cpu(cpu, mask) { /* Skip NUMA nodes, done above. */ if (cpumask_test_cpu(cpu, cpumask_of_node(node))) continue; -- 2.25.1