printk: kunit: support offstack cpumask

For large values of CONFIG_NR_CPUS, the newly added kunit test fails
to build:

kernel/printk/printk_ringbuffer_kunit_test.c: In function 'test_readerwriter':
kernel/printk/printk_ringbuffer_kunit_test.c:279:1: error: the frame size of 1432 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]

Change this to use cpumask_var_t and allocate it dynamically when
CONFIG_CPUMASK_OFFSTACK is set.

The variable has to be released via a KUnit action wrapper so that it is
freed when the test fails and gets aborted. The parameter type is hardcoded
to "struct cpumask *" because the macro KUNIT_DEFINE_ACTION_WRAPPER()
does not accept an array. But the function does nothing when
CONFIG_CPUMASK_OFFSTACK is not set anyway.

Fixes: 5ea2bcdfbf46 ("printk: ringbuffer: Add KUnit test")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/all/20250620192554.2234184-1-arnd@kernel.org
[pmladek@suse.com: Correctly handle allocation failures and freeing using KUnit test API.]
Link: https://lore.kernel.org/all/20250702095157.110916-3-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>

diff --git a/kernel/printk/printk_ringbuffer_kunit_test.c b/kernel/printk/printk_ringbuffer_kunit_test.c
index e67e1815f4c8f392be61ae1d3f47a42cd8db2328..2282348e869a6f93330737ddb8581fb2f245f9ff 100644 (file)
--- a/kernel/printk/printk_ringbuffer_kunit_test.c
+++ b/kernel/printk/printk_ringbuffer_kunit_test.c
@@ -223,8 +223,17 @@ static int prbtest_reader(struct prbtest_data *test_data, unsigned long timeout_
        return 0;
 }
 
+KUNIT_DEFINE_ACTION_WRAPPER(prbtest_cpumask_cleanup, free_cpumask_var, struct cpumask *);
 KUNIT_DEFINE_ACTION_WRAPPER(prbtest_kthread_cleanup, kthread_stop, struct task_struct *);
 
+static void prbtest_add_cpumask_cleanup(struct kunit *test, cpumask_var_t mask)
+{
+       int err;
+
+       err = kunit_add_action_or_reset(test, prbtest_cpumask_cleanup, mask);
+       KUNIT_ASSERT_EQ(test, err, 0);
+}
+
 static void prbtest_add_kthread_cleanup(struct kunit *test, struct task_struct *kthread)
 {
        int err;
@@ -247,9 +256,12 @@ static void test_readerwriter(struct kunit *test)
        struct prbtest_thread_data *thread_data;
        struct prbtest_data *test_data;
        struct task_struct *thread;
-       cpumask_t test_cpus;
+       cpumask_var_t test_cpus;
        int cpu, reader_cpu;
 
+       KUNIT_ASSERT_TRUE(test, alloc_cpumask_var(&test_cpus, GFP_KERNEL));
+       prbtest_add_cpumask_cleanup(test, test_cpus);
+
        cpus_read_lock();
        /*
         * Failure of KUNIT_ASSERT() kills the current task
@@ -257,15 +269,15 @@ static void test_readerwriter(struct kunit *test)
         * Instead use a snapshot of the online CPUs.
         * If they change during test execution it is unfortunate but not a grave error.
         */
-       cpumask_copy(&test_cpus, cpu_online_mask);
+       cpumask_copy(test_cpus, cpu_online_mask);
        cpus_read_unlock();
 
        /* One CPU is for the reader, all others are writers */
-       reader_cpu = cpumask_first(&test_cpus);
-       if (cpumask_weight(&test_cpus) == 1)
+       reader_cpu = cpumask_first(test_cpus);
+       if (cpumask_weight(test_cpus) == 1)
                kunit_warn(test, "more than one CPU is recommended");
        else
-               cpumask_clear_cpu(reader_cpu, &test_cpus);
+               cpumask_clear_cpu(reader_cpu, test_cpus);
 
        /* KUnit test can get restarted more times. */
        prbtest_prb_reinit(&test_rb);
@@ -278,7 +290,7 @@ static void test_readerwriter(struct kunit *test)
 
        kunit_info(test, "running for %lu ms\n", runtime_ms);
 
-       for_each_cpu(cpu, &test_cpus) {
+       for_each_cpu(cpu, test_cpus) {
                thread_data = kunit_kmalloc(test, sizeof(*thread_data), GFP_KERNEL);
                KUNIT_ASSERT_NOT_NULL(test, thread_data);
                thread_data->test_data = test_data;