linux-kernel - [PATCH v4 2/5] sparc/irq: Remove on-stack cpumask var

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Message-Id: <20240424025548.3765250-3-dawei.li@shingroup.cn>
Date: Wed, 24 Apr 2024 10:55:45 +0800
From: Dawei Li <dawei.li@...ngroup.cn>
To: davem@...emloft.net,
	andreas@...sler.com
Cc: sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	sam@...nborg.org,
	Dawei Li <dawei.li@...ngroup.cn>
Subject: [PATCH v4 2/5] sparc/irq: Remove on-stack cpumask var

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.

- Both 2 arguments of cpumask_equal() is constant and free of change, no
  need to allocate extra cpumask variables.

- Merge cpumask_and(), cpumask_first() and cpumask_empty() into
  cpumask_first_and().

Reviewed-by: Sam Ravnborg <sam@...nborg.org>
Signed-off-by: Dawei Li <dawei.li@...ngroup.cn>
---
 arch/sparc/kernel/irq_64.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index 5280e325d4d6..01ee800efde3 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -349,17 +349,13 @@ static unsigned int sun4u_compute_tid(unsigned long imap, unsigned long cpuid)
 #ifdef CONFIG_SMP
 static int irq_choose_cpu(unsigned int irq, const struct cpumask *affinity)
 {
-	cpumask_t mask;
 	int cpuid;
 
-	cpumask_copy(&mask, affinity);
-	if (cpumask_equal(&mask, cpu_online_mask)) {
+	if (cpumask_equal(affinity, cpu_online_mask)) {
 		cpuid = map_to_cpu(irq);
 	} else {
-		cpumask_t tmp;
-
-		cpumask_and(&tmp, cpu_online_mask, &mask);
-		cpuid = cpumask_empty(&tmp) ? map_to_cpu(irq) : cpumask_first(&tmp);
+		cpuid = cpumask_first_and(affinity, cpu_online_mask);
+		cpuid = cpuid < nr_cpu_ids ? cpuid : map_to_cpu(irq);
 	}
 
 	return cpuid;
-- 
2.27.0