linux-kernel - [tip:sched/core] sched/isolation: Require a present CPU in housekeeping mask

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Date:   Fri, 3 May 2019 04:30:29 -0700
From:   tip-bot for Nicholas Piggin <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     npiggin@...il.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, hpa@...or.com, torvalds@...ux-foundation.org,
        fweisbec@...il.com, mingo@...nel.org, peterz@...radead.org,
        rafael.j.wysocki@...el.com
Subject: [tip:sched/core] sched/isolation: Require a present CPU in
 housekeeping mask

Commit-ID:  e9a140c6d20ee29951a193342ebaccf07ebc63eb
Gitweb:     https://git.kernel.org/tip/e9a140c6d20ee29951a193342ebaccf07ebc63eb
Author:     Nicholas Piggin <npiggin@...il.com>
AuthorDate: Thu, 11 Apr 2019 13:34:47 +1000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 3 May 2019 12:53:14 +0200

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@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linuxppc-dev@...ts.ozlabs.org
Link: https://lkml.kernel.org/r/20190411033448.20842-5-npiggin@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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)) {