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Diffstat (limited to 'kernel/trace/preemptirq_delay_test.c')
| -rw-r--r-- | kernel/trace/preemptirq_delay_test.c | 204 |
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"); |