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.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-8-frederic@kernel.org

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)) {
+	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK))
 		tick_nohz_full_setup(non_housekeeping_mask);
-		} else {
-			pr_warn("Housekeeping: nohz unsupported."
-				" Build with CONFIG_NO_HZ_FULL\n");
-			goto free_housekeeping_staging;
-		}
-	}
 
 	housekeeping_flags |= flags;
 	err = 1;