linux-kernel - [PATCH 7/8] sched/isolation: Fix housekeeping

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Date:   Mon,  7 Feb 2022 16:59:09 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...two.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Nitesh Lal <nilal@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Nicolas Saenz <nsaenzju@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Phil Auld <pauld@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Zefan Li <lizefan.x@...edance.com>
Subject: [PATCH 7/8] sched/isolation: Fix housekeeping_mask memory leak

If "nohz_full=" or "isolcpus=nohz" are called with CONFIG_NO_HZ_FULL=n,
housekeeping_mask doesn't get freed despite it being unused if
housekeeping_setup() is called for the first time.

Check this scenario first to fix this, so that no useless allocation
is performed.

Reviewed-by: Juri Lelli <juri.lelli@...hat.com>
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: Phil Auld <pauld@...hat.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Nitesh Lal <nilal@...hat.com>
Cc: Nicolas Saenz <nsaenzju@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Christoph Lameter <cl@...two.de>
Cc: Tejun Heo <tj@...nel.org>
Cc: Zefan Li <lizefan.x@...edance.com>
Cc: Alex Belits <abelits@...vell.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 kernel/sched/isolation.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 828dacec483e..883eee9fae22 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -94,6 +94,14 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
 	cpumask_var_t non_housekeeping_mask, housekeeping_staging;
 	int err = 0;
 
+	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
+		if (!IS_ENABLED(CONFIG_NO_HZ_FULL)) {
+			pr_warn("Housekeeping: nohz unsupported."
+				" Build with CONFIG_NO_HZ_FULL\n");
+			return 0;
+		}
+	}
+
 	alloc_bootmem_cpumask_var(&non_housekeeping_mask);
 	if (cpulist_parse(str, non_housekeeping_mask) < 0) {
 		pr_warn("Housekeeping: nohz_full= or isolcpus= incorrect CPU range\n");
@@ -123,15 +131,8 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
 		}
 	}
 
-	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
-		if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
-			tick_nohz_full_setup(non_housekeeping_mask);
-		} else {
-			pr_warn("Housekeeping: nohz unsupported."
-				" Build with CONFIG_NO_HZ_FULL\n");
-			goto free_housekeeping_staging;
-		}
-	}
+	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK))
+		tick_nohz_full_setup(non_housekeeping_mask);
 
 	housekeeping_flags |= flags;
 	err = 1;
-- 
2.25.1