linux-kernel - [PATCH v3 02/10] perf/alibaba_uncore_drw: Avoid placing cpumask on the stack

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Date: Wed,  3 Apr 2024 23:59:42 +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 02/10] perf/alibaba_uncore_drw: 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/alibaba_uncore_drw_pmu.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/perf/alibaba_uncore_drw_pmu.c b/drivers/perf/alibaba_uncore_drw_pmu.c
index a9277dcf90ce..d4d14b65c4a5 100644
--- a/drivers/perf/alibaba_uncore_drw_pmu.c
+++ b/drivers/perf/alibaba_uncore_drw_pmu.c
@@ -746,18 +746,14 @@ static int ali_drw_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
 	struct ali_drw_pmu_irq *irq;
 	struct ali_drw_pmu *drw_pmu;
 	unsigned int target;
-	int ret;
-	cpumask_t node_online_cpus;
 
 	irq = hlist_entry_safe(node, struct ali_drw_pmu_irq, node);
 	if (cpu != irq->cpu)
 		return 0;
 
-	ret = cpumask_and(&node_online_cpus,
-			  cpumask_of_node(cpu_to_node(cpu)), cpu_online_mask);
-	if (ret)
-		target = cpumask_any_but(&node_online_cpus, cpu);
-	else
+	target = cpumask_any_and_but(cpumask_of_node(cpu_to_node(cpu)),
+				     cpu_online_mask, cpu);
+	if (target >= nr_cpu_ids)
 		target = cpumask_any_but(cpu_online_mask, cpu);
 
 	if (target >= nr_cpu_ids)
-- 
2.27.0