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-rw-r--r--kernel/trace/preemptirq_delay_test.c204
1 files changed, 204 insertions, 0 deletions
diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c
new file mode 100644
index 000000000..312d1a0ca
--- /dev/null
+++ b/kernel/trace/preemptirq_delay_test.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Preempt / IRQ disable delay thread to test latency tracers
+ *
+ * Copyright (C) 2018 Joel Fernandes (Google) <joel@joelfernandes.org>
+ */
+
+#include <linux/trace_clock.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/kobject.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/completion.h>
+
+static ulong delay = 100;
+static char test_mode[12] = "irq";
+static uint burst_size = 1;
+
+module_param_named(delay, delay, ulong, 0444);
+module_param_string(test_mode, test_mode, 12, 0444);
+module_param_named(burst_size, burst_size, uint, 0444);
+MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)");
+MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)");
+MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
+
+static struct completion done;
+
+#define MIN(x, y) ((x) < (y) ? (x) : (y))
+
+static void busy_wait(ulong time)
+{
+ u64 start, end;
+ start = trace_clock_local();
+ do {
+ end = trace_clock_local();
+ if (kthread_should_stop())
+ break;
+ } while ((end - start) < (time * 1000));
+}
+
+static __always_inline void irqoff_test(void)
+{
+ unsigned long flags;
+ local_irq_save(flags);
+ busy_wait(delay);
+ local_irq_restore(flags);
+}
+
+static __always_inline void preemptoff_test(void)
+{
+ preempt_disable();
+ busy_wait(delay);
+ preempt_enable();
+}
+
+static void execute_preemptirqtest(int idx)
+{
+ if (!strcmp(test_mode, "irq"))
+ irqoff_test();
+ else if (!strcmp(test_mode, "preempt"))
+ preemptoff_test();
+ else if (!strcmp(test_mode, "alternate")) {
+ if (idx % 2 == 0)
+ irqoff_test();
+ else
+ preemptoff_test();
+ }
+}
+
+#define DECLARE_TESTFN(POSTFIX) \
+ static void preemptirqtest_##POSTFIX(int idx) \
+ { \
+ execute_preemptirqtest(idx); \
+ } \
+
+/*
+ * We create 10 different functions, so that we can get 10 different
+ * backtraces.
+ */
+DECLARE_TESTFN(0)
+DECLARE_TESTFN(1)
+DECLARE_TESTFN(2)
+DECLARE_TESTFN(3)
+DECLARE_TESTFN(4)
+DECLARE_TESTFN(5)
+DECLARE_TESTFN(6)
+DECLARE_TESTFN(7)
+DECLARE_TESTFN(8)
+DECLARE_TESTFN(9)
+
+static void (*testfuncs[])(int) = {
+ preemptirqtest_0,
+ preemptirqtest_1,
+ preemptirqtest_2,
+ preemptirqtest_3,
+ preemptirqtest_4,
+ preemptirqtest_5,
+ preemptirqtest_6,
+ preemptirqtest_7,
+ preemptirqtest_8,
+ preemptirqtest_9,
+};
+
+#define NR_TEST_FUNCS ARRAY_SIZE(testfuncs)
+
+static int preemptirq_delay_run(void *data)
+{
+ int i;
+ int s = MIN(burst_size, NR_TEST_FUNCS);
+
+ for (i = 0; i < s; i++)
+ (testfuncs[i])(i);
+
+ complete(&done);
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ while (!kthread_should_stop()) {
+ schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
+ }
+
+ __set_current_state(TASK_RUNNING);
+
+ return 0;
+}
+
+static int preemptirq_run_test(void)
+{
+ struct task_struct *task;
+ char task_name[50];
+
+ init_completion(&done);
+
+ snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
+ task = kthread_run(preemptirq_delay_run, NULL, task_name);
+ if (IS_ERR(task))
+ return PTR_ERR(task);
+ if (task) {
+ wait_for_completion(&done);
+ kthread_stop(task);
+ }
+ return 0;
+}
+
+
+static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ ssize_t ret;
+
+ ret = preemptirq_run_test();
+ if (ret)
+ return ret;
+ return count;
+}
+
+static struct kobj_attribute trigger_attribute =
+ __ATTR(trigger, 0200, NULL, trigger_store);
+
+static struct attribute *attrs[] = {
+ &trigger_attribute.attr,
+ NULL,
+};
+
+static struct attribute_group attr_group = {
+ .attrs = attrs,
+};
+
+static struct kobject *preemptirq_delay_kobj;
+
+static int __init preemptirq_delay_init(void)
+{
+ int retval;
+
+ retval = preemptirq_run_test();
+ if (retval != 0)
+ return retval;
+
+ preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test",
+ kernel_kobj);
+ if (!preemptirq_delay_kobj)
+ return -ENOMEM;
+
+ retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group);
+ if (retval)
+ kobject_put(preemptirq_delay_kobj);
+
+ return retval;
+}
+
+static void __exit preemptirq_delay_exit(void)
+{
+ kobject_put(preemptirq_delay_kobj);
+}
+
+module_init(preemptirq_delay_init)
+module_exit(preemptirq_delay_exit)
+MODULE_LICENSE("GPL v2");