[tip: sched/core] sched/isolation: Consolidate check for housekeeping minimum service

[tip-bot2 for Frederic Weisbecker]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     6367b600e31c6b211eadee7bf7f4ed8c755e9176
Gitweb:        https://git.kernel.org/tip/6367b600e31c6b211eadee7bf7f4ed8c755e9176
Author:        Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate:    Mon, 07 Feb 2022 16:59:07 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 16 Feb 2022 15:57:55 +01:00

sched/isolation: Consolidate check for housekeeping minimum service

There can be two subsequent calls to housekeeping_setup() due to
"nohz_full=" and "isolcpus=" that can mix up.  The two passes each have
their own way to deal with an empty housekeeping set of CPUs.
Consolidate this part and remove the awful "tmp" based naming.

Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Reviewed-by: Phil Auld <pauld@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220207155910.527133-6-frederic@xxxxxxxxxx
---
 kernel/sched/isolation.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index a735d9e..23085e6 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -91,8 +91,7 @@ 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;
+	cpumask_var_t non_housekeeping_mask, housekeeping_staging;
 
 	alloc_bootmem_cpumask_var(&non_housekeeping_mask);
 	if (cpulist_parse(str, non_housekeeping_mask) < 0) {
@@ -101,32 +100,32 @@ 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);
+	alloc_bootmem_cpumask_var(&housekeeping_staging);
+	cpumask_andnot(housekeeping_staging,
+		       cpu_possible_mask, non_housekeeping_mask);
 
-		cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
-		if (cpumask_empty(tmp)) {
+	if (!cpumask_intersects(cpu_present_mask, housekeeping_staging)) {
+		__cpumask_set_cpu(smp_processor_id(), housekeeping_staging);
+		__cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
+		if (!housekeeping_flags) {
 			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);
 		}
+	}
+
+	if (!housekeeping_flags) {
+		alloc_bootmem_cpumask_var(&housekeeping_mask);
+		cpumask_copy(housekeeping_mask, housekeeping_staging);
 	} else {
-		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)) {
+		if (!cpumask_equal(housekeeping_staging, housekeeping_mask)) {
 			pr_warn("Housekeeping: nohz_full= must match isolcpus=\n");
-			free_bootmem_cpumask_var(tmp);
+			free_bootmem_cpumask_var(housekeeping_staging);
 			free_bootmem_cpumask_var(non_housekeeping_mask);
 			return 0;
 		}
 	}
-	free_bootmem_cpumask_var(tmp);
+
+	free_bootmem_cpumask_var(housekeeping_staging);
 
 	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
 		if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {