diff options
| -rw-r--r-- | kernel/trace/Kconfig | 15 | ||||
| -rw-r--r-- | kernel/trace/Makefile | 1 | ||||
| -rw-r--r-- | kernel/trace/preemptirq_delay_test.c | 72 |
3 files changed, 88 insertions, 0 deletions
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index dcc0166d1997..e15fadbe5dfb 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -687,6 +687,21 @@ config RING_BUFFER_STARTUP_TEST If unsure, say N +config PREEMPTIRQ_DELAY_TEST + tristate "Preempt / IRQ disable delay thread to test latency tracers" + depends on m + help + Select this option to build a test module that can help test latency + tracers by executing a preempt or irq disable section with a user + configurable delay. The module busy waits for the duration of the + critical section. + + For example, the following invocation forces a one-time irq-disabled + critical section for 500us: + modprobe preemptirq_delay_test test_mode=irq delay=500000 + + If unsure, say N + config TRACE_EVAL_MAP_FILE bool "Show eval mappings for trace events" depends on TRACING diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index e2538c7638d4..31c6b524c260 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -33,6 +33,7 @@ obj-$(CONFIG_TRACING) += trace_seq.o obj-$(CONFIG_TRACING) += trace_stat.o obj-$(CONFIG_TRACING) += trace_printk.o obj-$(CONFIG_TRACING_MAP) += tracing_map.o +obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.o obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o obj-$(CONFIG_PREEMPTIRQ_EVENTS) += trace_irqsoff.o diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c new file mode 100644 index 000000000000..c97a026c0720 --- /dev/null +++ b/kernel/trace/preemptirq_delay_test.c @@ -0,0 +1,72 @@ +// 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/delay.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/kthread.h> +#include <linux/ktime.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/string.h> + +static ulong delay = 100; +static char test_mode[10] = "irq"; + +module_param_named(delay, delay, ulong, S_IRUGO); +module_param_string(test_mode, test_mode, 10, S_IRUGO); +MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)"); +MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)"); + +static void busy_wait(ulong time) +{ + ktime_t start, end; + start = ktime_get(); + do { + end = ktime_get(); + if (kthread_should_stop()) + break; + } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000)); +} + +int preemptirq_delay_run(void *data) +{ + unsigned long flags; + + if (!strcmp(test_mode, "irq")) { + local_irq_save(flags); + busy_wait(delay); + local_irq_restore(flags); + } else if (!strcmp(test_mode, "preempt")) { + preempt_disable(); + busy_wait(delay); + preempt_enable(); + } + + return 0; +} + +static int __init preemptirq_delay_init(void) +{ + char task_name[50]; + struct task_struct *test_task; + + snprintf(task_name, sizeof(task_name), "%s_test", test_mode); + + test_task = kthread_run(preemptirq_delay_run, NULL, task_name); + return PTR_ERR_OR_ZERO(test_task); +} + +static void __exit preemptirq_delay_exit(void) +{ + return; +} + +module_init(preemptirq_delay_init) +module_exit(preemptirq_delay_exit) +MODULE_LICENSE("GPL v2"); |