linux-kernel - [PATCH v3 08/10] perf/hisi_uncore: Avoid placing cpumask on the stack

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Message-Id: <20240403155950.2068109-9-dawei.li@shingroup.cn>
Date: Wed,  3 Apr 2024 23:59:48 +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 08/10] perf/hisi_uncore: 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/hisilicon/hisi_uncore_pmu.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/perf/hisilicon/hisi_uncore_pmu.c b/drivers/perf/hisilicon/hisi_uncore_pmu.c
index 04031450d5fe..ccc9191ad1b6 100644
--- a/drivers/perf/hisilicon/hisi_uncore_pmu.c
+++ b/drivers/perf/hisilicon/hisi_uncore_pmu.c
@@ -504,7 +504,6 @@ int hisi_uncore_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
 {
 	struct hisi_pmu *hisi_pmu = hlist_entry_safe(node, struct hisi_pmu,
 						     node);
-	cpumask_t pmu_online_cpus;
 	unsigned int target;
 
 	if (!cpumask_test_and_clear_cpu(cpu, &hisi_pmu->associated_cpus))
@@ -518,9 +517,8 @@ int hisi_uncore_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
 	hisi_pmu->on_cpu = -1;
 
 	/* Choose a new CPU to migrate ownership of the PMU to */
-	cpumask_and(&pmu_online_cpus, &hisi_pmu->associated_cpus,
-		    cpu_online_mask);
-	target = cpumask_any_but(&pmu_online_cpus, cpu);
+	target = cpumask_any_and_but(&hisi_pmu->associated_cpus,
+				     cpu_online_mask, cpu);
 	if (target >= nr_cpu_ids)
 		return 0;
 
-- 
2.27.0