linux-kernel - [PATCH v3 10/10] perf/thunderx2: Avoid placing cpumask on the stack

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Date: Wed,  3 Apr 2024 23:59:50 +0800
From: Dawei Li <dawei.li@...ngroup.cn>
To: will@...nel.org,
	mark.rutland@....com,
	yury.norov@...il.com,
	linux@...musvillemoes.dk
Cc: xueshuai@...ux.alibaba.com,
	renyu.zj@...ux.alibaba.com,
	yangyicong@...ilicon.com,
	jonathan.cameron@...wei.com,
	andersson@...nel.org,
	konrad.dybcio@...aro.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	Dawei Li <dawei.li@...ngroup.cn>
Subject: [PATCH v3 10/10] perf/thunderx2: 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@....com>
Reviewed-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Dawei Li <dawei.li@...ngroup.cn>
---
 drivers/perf/thunderx2_pmu.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/perf/thunderx2_pmu.c b/drivers/perf/thunderx2_pmu.c
index e16d10c763de..b3377b662ffc 100644
--- a/drivers/perf/thunderx2_pmu.c
+++ b/drivers/perf/thunderx2_pmu.c
@@ -932,9 +932,8 @@ static int tx2_uncore_pmu_online_cpu(unsigned int cpu,
 static int tx2_uncore_pmu_offline_cpu(unsigned int cpu,
 		struct hlist_node *hpnode)
 {
-	int new_cpu;
 	struct tx2_uncore_pmu *tx2_pmu;
-	struct cpumask cpu_online_mask_temp;
+	unsigned int new_cpu;
 
 	tx2_pmu = hlist_entry_safe(hpnode,
 			struct tx2_uncore_pmu, hpnode);
@@ -945,11 +944,8 @@ static int tx2_uncore_pmu_offline_cpu(unsigned int cpu,
 	if (tx2_pmu->hrtimer_callback)
 		hrtimer_cancel(&tx2_pmu->hrtimer);
 
-	cpumask_copy(&cpu_online_mask_temp, cpu_online_mask);
-	cpumask_clear_cpu(cpu, &cpu_online_mask_temp);
-	new_cpu = cpumask_any_and(
-			cpumask_of_node(tx2_pmu->node),
-			&cpu_online_mask_temp);
+	new_cpu = cpumask_any_and_but(cpumask_of_node(tx2_pmu->node),
+				      cpu_online_mask, cpu);
 
 	tx2_pmu->cpu = new_cpu;
 	if (new_cpu >= nr_cpu_ids)
-- 
2.27.0