2 * trace task wakeup timings
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
7 * Based on code from the latency_tracer, that is:
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 William Lee Irwin III
12 #include <linux/module.h>
14 #include <linux/debugfs.h>
15 #include <linux/kallsyms.h>
16 #include <linux/uaccess.h>
17 #include <linux/ftrace.h>
18 #include <trace/events/sched.h>
22 static struct trace_array *wakeup_trace;
23 static int __read_mostly tracer_enabled;
25 static struct task_struct *wakeup_task;
26 static int wakeup_cpu;
27 static int wakeup_current_cpu;
28 static unsigned wakeup_prio = -1;
31 static arch_spinlock_t wakeup_lock =
32 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
34 static void __wakeup_reset(struct trace_array *tr);
36 static int save_lat_flag;
38 #ifdef CONFIG_FUNCTION_TRACER
40 * irqsoff uses its own tracer function to keep the overhead down:
43 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
45 struct trace_array *tr = wakeup_trace;
46 struct trace_array_cpu *data;
53 if (likely(!wakeup_task))
57 resched = ftrace_preempt_disable();
59 cpu = raw_smp_processor_id();
60 if (cpu != wakeup_current_cpu)
64 disabled = atomic_inc_return(&data->disabled);
65 if (unlikely(disabled != 1))
68 local_irq_save(flags);
70 trace_function(tr, ip, parent_ip, flags, pc);
72 local_irq_restore(flags);
75 atomic_dec(&data->disabled);
77 ftrace_preempt_enable(resched);
80 static struct ftrace_ops trace_ops __read_mostly =
82 .func = wakeup_tracer_call,
84 #endif /* CONFIG_FUNCTION_TRACER */
87 * Should this new latency be reported/recorded?
89 static int report_latency(cycle_t delta)
92 if (delta < tracing_thresh)
95 if (delta <= tracing_max_latency)
102 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
104 if (task != wakeup_task)
107 wakeup_current_cpu = cpu;
111 probe_wakeup_sched_switch(void *ignore,
112 struct task_struct *prev, struct task_struct *next)
114 struct trace_array_cpu *data;
115 cycle_t T0, T1, delta;
121 tracing_record_cmdline(prev);
123 if (unlikely(!tracer_enabled))
127 * When we start a new trace, we set wakeup_task to NULL
128 * and then set tracer_enabled = 1. We want to make sure
129 * that another CPU does not see the tracer_enabled = 1
130 * and the wakeup_task with an older task, that might
131 * actually be the same as next.
135 if (next != wakeup_task)
138 pc = preempt_count();
140 /* disable local data, not wakeup_cpu data */
141 cpu = raw_smp_processor_id();
142 disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
143 if (likely(disabled != 1))
146 local_irq_save(flags);
147 arch_spin_lock(&wakeup_lock);
149 /* We could race with grabbing wakeup_lock */
150 if (unlikely(!tracer_enabled || next != wakeup_task))
153 /* The task we are waiting for is waking up */
154 data = wakeup_trace->data[wakeup_cpu];
156 trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
157 tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
159 T0 = data->preempt_timestamp;
160 T1 = ftrace_now(cpu);
163 if (!report_latency(delta))
166 if (likely(!is_tracing_stopped())) {
167 tracing_max_latency = delta;
168 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
172 __wakeup_reset(wakeup_trace);
173 arch_spin_unlock(&wakeup_lock);
174 local_irq_restore(flags);
176 atomic_dec(&wakeup_trace->data[cpu]->disabled);
179 static void __wakeup_reset(struct trace_array *tr)
185 put_task_struct(wakeup_task);
190 static void wakeup_reset(struct trace_array *tr)
194 tracing_reset_online_cpus(tr);
196 local_irq_save(flags);
197 arch_spin_lock(&wakeup_lock);
199 arch_spin_unlock(&wakeup_lock);
200 local_irq_restore(flags);
204 probe_wakeup(void *ignore, struct task_struct *p, int success)
206 struct trace_array_cpu *data;
207 int cpu = smp_processor_id();
212 if (likely(!tracer_enabled))
215 tracing_record_cmdline(p);
216 tracing_record_cmdline(current);
218 if ((wakeup_rt && !rt_task(p)) ||
219 p->prio >= wakeup_prio ||
220 p->prio >= current->prio)
223 pc = preempt_count();
224 disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
225 if (unlikely(disabled != 1))
228 /* interrupts should be off from try_to_wake_up */
229 arch_spin_lock(&wakeup_lock);
231 /* check for races. */
232 if (!tracer_enabled || p->prio >= wakeup_prio)
235 /* reset the trace */
236 __wakeup_reset(wakeup_trace);
238 wakeup_cpu = task_cpu(p);
239 wakeup_current_cpu = wakeup_cpu;
240 wakeup_prio = p->prio;
243 get_task_struct(wakeup_task);
245 local_save_flags(flags);
247 data = wakeup_trace->data[wakeup_cpu];
248 data->preempt_timestamp = ftrace_now(cpu);
249 tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
252 * We must be careful in using CALLER_ADDR2. But since wake_up
253 * is not called by an assembly function (where as schedule is)
254 * it should be safe to use it here.
256 trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
259 arch_spin_unlock(&wakeup_lock);
261 atomic_dec(&wakeup_trace->data[cpu]->disabled);
264 static void start_wakeup_tracer(struct trace_array *tr)
268 ret = register_trace_sched_wakeup(probe_wakeup, NULL);
270 pr_info("wakeup trace: Couldn't activate tracepoint"
271 " probe to kernel_sched_wakeup\n");
275 ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
277 pr_info("wakeup trace: Couldn't activate tracepoint"
278 " probe to kernel_sched_wakeup_new\n");
282 ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
284 pr_info("sched trace: Couldn't activate tracepoint"
285 " probe to kernel_sched_switch\n");
286 goto fail_deprobe_wake_new;
289 ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
291 pr_info("wakeup trace: Couldn't activate tracepoint"
292 " probe to kernel_sched_migrate_task\n");
299 * Don't let the tracer_enabled = 1 show up before
300 * the wakeup_task is reset. This may be overkill since
301 * wakeup_reset does a spin_unlock after setting the
302 * wakeup_task to NULL, but I want to be safe.
303 * This is a slow path anyway.
307 register_ftrace_function(&trace_ops);
309 if (tracing_is_enabled())
315 fail_deprobe_wake_new:
316 unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
318 unregister_trace_sched_wakeup(probe_wakeup, NULL);
321 static void stop_wakeup_tracer(struct trace_array *tr)
324 unregister_ftrace_function(&trace_ops);
325 unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
326 unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
327 unregister_trace_sched_wakeup(probe_wakeup, NULL);
328 unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
331 static int __wakeup_tracer_init(struct trace_array *tr)
333 save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
334 trace_flags |= TRACE_ITER_LATENCY_FMT;
336 tracing_max_latency = 0;
338 start_wakeup_tracer(tr);
342 static int wakeup_tracer_init(struct trace_array *tr)
345 return __wakeup_tracer_init(tr);
348 static int wakeup_rt_tracer_init(struct trace_array *tr)
351 return __wakeup_tracer_init(tr);
354 static void wakeup_tracer_reset(struct trace_array *tr)
356 stop_wakeup_tracer(tr);
357 /* make sure we put back any tasks we are tracing */
361 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
364 static void wakeup_tracer_start(struct trace_array *tr)
370 static void wakeup_tracer_stop(struct trace_array *tr)
375 static struct tracer wakeup_tracer __read_mostly =
378 .init = wakeup_tracer_init,
379 .reset = wakeup_tracer_reset,
380 .start = wakeup_tracer_start,
381 .stop = wakeup_tracer_stop,
383 #ifdef CONFIG_FTRACE_SELFTEST
384 .selftest = trace_selftest_startup_wakeup,
388 static struct tracer wakeup_rt_tracer __read_mostly =
391 .init = wakeup_rt_tracer_init,
392 .reset = wakeup_tracer_reset,
393 .start = wakeup_tracer_start,
394 .stop = wakeup_tracer_stop,
395 .wait_pipe = poll_wait_pipe,
397 #ifdef CONFIG_FTRACE_SELFTEST
398 .selftest = trace_selftest_startup_wakeup,
402 __init static int init_wakeup_tracer(void)
406 ret = register_tracer(&wakeup_tracer);
410 ret = register_tracer(&wakeup_rt_tracer);
416 device_initcall(init_wakeup_tracer);