From: Dawei Li <dawei.li@shingroup.cn>
Date: Wed, 3 Apr 2024 15:59:43 +0000 (+0800)
Subject: perf/arm-cmn: Avoid placing cpumask on the stack
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=60c73240f304a654b66811f7f56a3325201f46de;p=linux.git

perf/arm-cmn: Avoid placing cpumask on the stack

In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

Use cpumask_any_and_but() to avoid the need for a temporary cpumask on
the stack.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
Link: https://lore.kernel.org/r/20240403155950.2068109-4-dawei.li@shingroup.cn
Signed-off-by: Will Deacon <will@kernel.org>
---

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 7ef9c7e4836b7..6bfb0c4a1287e 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1950,20 +1950,20 @@ static int arm_cmn_pmu_offline_cpu(unsigned int cpu, struct hlist_node *cpuhp_no
 	struct arm_cmn *cmn;
 	unsigned int target;
 	int node;
-	cpumask_t mask;
 
 	cmn = hlist_entry_safe(cpuhp_node, struct arm_cmn, cpuhp_node);
 	if (cpu != cmn->cpu)
 		return 0;
 
 	node = dev_to_node(cmn->dev);
-	if (cpumask_and(&mask, cpumask_of_node(node), cpu_online_mask) &&
-	    cpumask_andnot(&mask, &mask, cpumask_of(cpu)))
-		target = cpumask_any(&mask);
-	else
+
+	target = cpumask_any_and_but(cpumask_of_node(node), cpu_online_mask, cpu);
+	if (target >= nr_cpu_ids)
 		target = cpumask_any_but(cpu_online_mask, cpu);
+
 	if (target < nr_cpu_ids)
 		arm_cmn_migrate(cmn, target);
+
 	return 0;
 }