[PATCH 3/4] kernel/sched/isolation: require a present CPU in housekeeping mask

[Nicholas Piggin]

During housekeeping mask setup, currently a possible CPU is required.
That does not guarantee a CPU at boot time, so check to ensure that
at least one present CPU is in the mask.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 kernel/sched/isolation.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index b02d148e7672..687302051a27 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -65,6 +65,7 @@ void __init housekeeping_init(void)
 static int __init housekeeping_setup(char *str, enum hk_flags flags)
 {
        cpumask_var_t non_housekeeping_mask;
+       cpumask_var_t tmp;
        int err;
 
        alloc_bootmem_cpumask_var(&non_housekeeping_mask);
@@ -75,16 +76,23 @@ static int __init housekeeping_setup(char *str, enum 
hk_flags flags)
                return 0;
        }
 
+       alloc_bootmem_cpumask_var(&tmp);
        if (!housekeeping_flags) {
                alloc_bootmem_cpumask_var(&housekeeping_mask);
                cpumask_andnot(housekeeping_mask,
                               cpu_possible_mask, non_housekeeping_mask);
-               if (cpumask_empty(housekeeping_mask))
+
+               cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
+               if (cpumask_empty(tmp)) {
+                       pr_warn("Housekeeping: must include one present CPU, "
+                               "using boot CPU:%d\n", smp_processor_id());
                        __cpumask_set_cpu(smp_processor_id(), 
housekeeping_mask);
+                       __cpumask_clear_cpu(smp_processor_id(), 
non_housekeeping_mask);
+               }
        } else {
-               cpumask_var_t tmp;
-
-               alloc_bootmem_cpumask_var(&tmp);
+               cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
+               if (cpumask_empty(tmp))
+                       __cpumask_clear_cpu(smp_processor_id(), 
non_housekeeping_mask);
                cpumask_andnot(tmp, cpu_possible_mask, non_housekeeping_mask);
                if (!cpumask_equal(tmp, housekeeping_mask)) {
                        pr_warn("Housekeeping: nohz_full= must match 
isolcpus=\n");
@@ -92,8 +100,8 @@ static int __init housekeeping_setup(char *str, enum 
hk_flags flags)
                        free_bootmem_cpumask_var(non_housekeeping_mask);
                        return 0;
                }
-               free_bootmem_cpumask_var(tmp);
        }
+       free_bootmem_cpumask_var(tmp);
 
        if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
                if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
-- 
2.20.1