linux-kernel - [PATCH] kernel: trace: preemptirq_delay

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Message-Id: <20250620111215.3365305-1-arnd@kernel.org>
Date: Fri, 20 Jun 2025 13:12:12 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Song Chen <chensong_2000@....cn>
Cc: Arnd Bergmann <arnd@...db.de>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH] kernel: trace: preemptirq_delay_test: use offstack cpu mask

From: Arnd Bergmann <arnd@...db.de>

A CPU mask on the stack is broken for large values of CONFIG_NR_CPUS:

kernel/trace/preemptirq_delay_test.c: In function ‘preemptirq_delay_run’:
kernel/trace/preemptirq_delay_test.c:143:1: error: the frame size of 8512 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]

Fall back to dynamic allocation here.

Fixes: 4b9091e1c194 ("kernel: trace: preemptirq_delay_test: add cpu affinity")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 kernel/trace/preemptirq_delay_test.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c
index 9b7037194663..331b49240180 100644
--- a/kernel/trace/preemptirq_delay_test.c
+++ b/kernel/trace/preemptirq_delay_test.c
@@ -117,12 +117,15 @@ static int preemptirq_delay_run(void *data)
 {
 	int i;
 	int s = min(burst_size, NR_TEST_FUNCS);
-	struct cpumask cpu_mask;
+	cpumask_var_t cpu_mask;
+
+	if (!alloc_cpumask_var(&cpu_mask, GFP_KERNEL))
+		return -ENOMEM;
 
 	if (cpu_affinity > -1) {
-		cpumask_clear(&cpu_mask);
-		cpumask_set_cpu(cpu_affinity, &cpu_mask);
-		if (set_cpus_allowed_ptr(current, &cpu_mask))
+		cpumask_clear(cpu_mask);
+		cpumask_set_cpu(cpu_affinity, cpu_mask);
+		if (set_cpus_allowed_ptr(current, cpu_mask))
 			pr_err("cpu_affinity:%d, failed\n", cpu_affinity);
 	}
 
@@ -139,6 +142,8 @@ static int preemptirq_delay_run(void *data)
 
 	__set_current_state(TASK_RUNNING);
 
+	free_cpumask_var(cpu_mask);
+
 	return 0;
 }
 
-- 
2.39.5