sched/isolation: Require a present CPU in housekeeping mask

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

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lkml.kernel.org/r/20190411033448.20842-5-npiggin@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index b02d148e767273c3a2641b4c66b9f0d24ea6e9ee..687302051a270d6300acf70822d95c016e1b8a33 100644 (file)
--- 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)) {