302 lines
6.3 KiB
C
302 lines
6.3 KiB
C
/*
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* trace task wakeup timings
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
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*
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* Based on code from the latency_tracer, that is:
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*
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* Copyright (C) 2004-2006 Ingo Molnar
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* Copyright (C) 2004 William Lee Irwin III
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/debugfs.h>
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#include <linux/kallsyms.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include "trace.h"
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static struct trace_array *wakeup_trace;
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static int __read_mostly tracer_enabled;
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static struct task_struct *wakeup_task;
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static int wakeup_cpu;
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static unsigned wakeup_prio = -1;
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static DEFINE_SPINLOCK(wakeup_lock);
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static void __wakeup_reset(struct trace_array *tr);
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/*
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* Should this new latency be reported/recorded?
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*/
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static int report_latency(cycle_t delta)
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{
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if (tracing_thresh) {
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if (delta < tracing_thresh)
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return 0;
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} else {
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if (delta <= tracing_max_latency)
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return 0;
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}
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return 1;
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}
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void
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wakeup_sched_switch(struct task_struct *prev, struct task_struct *next)
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{
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unsigned long latency = 0, t0 = 0, t1 = 0;
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struct trace_array *tr = wakeup_trace;
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struct trace_array_cpu *data;
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cycle_t T0, T1, delta;
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unsigned long flags;
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long disabled;
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int cpu;
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if (unlikely(!tracer_enabled))
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return;
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/*
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* When we start a new trace, we set wakeup_task to NULL
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* and then set tracer_enabled = 1. We want to make sure
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* that another CPU does not see the tracer_enabled = 1
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* and the wakeup_task with an older task, that might
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* actually be the same as next.
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*/
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smp_rmb();
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if (next != wakeup_task)
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return;
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/* The task we are waitng for is waking up */
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data = tr->data[wakeup_cpu];
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/* disable local data, not wakeup_cpu data */
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cpu = raw_smp_processor_id();
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disabled = atomic_inc_return(&tr->data[cpu]->disabled);
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if (likely(disabled != 1))
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goto out;
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spin_lock_irqsave(&wakeup_lock, flags);
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/* We could race with grabbing wakeup_lock */
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if (unlikely(!tracer_enabled || next != wakeup_task))
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goto out_unlock;
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trace_function(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
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/*
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* usecs conversion is slow so we try to delay the conversion
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* as long as possible:
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*/
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T0 = data->preempt_timestamp;
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T1 = ftrace_now(cpu);
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delta = T1-T0;
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if (!report_latency(delta))
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goto out_unlock;
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latency = nsecs_to_usecs(delta);
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tracing_max_latency = delta;
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t0 = nsecs_to_usecs(T0);
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t1 = nsecs_to_usecs(T1);
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update_max_tr(tr, wakeup_task, wakeup_cpu);
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if (tracing_thresh) {
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printk(KERN_INFO "(%16s-%-5d|#%d):"
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" %lu us wakeup latency violates %lu us threshold.\n",
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wakeup_task->comm, wakeup_task->pid,
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raw_smp_processor_id(),
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latency, nsecs_to_usecs(tracing_thresh));
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} else {
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printk(KERN_INFO "(%16s-%-5d|#%d):"
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" new %lu us maximum wakeup latency.\n",
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wakeup_task->comm, wakeup_task->pid,
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cpu, latency);
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}
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out_unlock:
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__wakeup_reset(tr);
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spin_unlock_irqrestore(&wakeup_lock, flags);
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out:
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atomic_dec(&tr->data[cpu]->disabled);
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}
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static void __wakeup_reset(struct trace_array *tr)
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{
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struct trace_array_cpu *data;
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int cpu;
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assert_spin_locked(&wakeup_lock);
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for_each_possible_cpu(cpu) {
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data = tr->data[cpu];
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tracing_reset(data);
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}
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wakeup_cpu = -1;
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wakeup_prio = -1;
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if (wakeup_task)
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put_task_struct(wakeup_task);
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wakeup_task = NULL;
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}
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static void wakeup_reset(struct trace_array *tr)
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{
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unsigned long flags;
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spin_lock_irqsave(&wakeup_lock, flags);
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__wakeup_reset(tr);
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spin_unlock_irqrestore(&wakeup_lock, flags);
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}
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static void
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wakeup_check_start(struct trace_array *tr, struct task_struct *p,
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struct task_struct *curr)
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{
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int cpu = smp_processor_id();
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unsigned long flags;
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long disabled;
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if (likely(!rt_task(p)) ||
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p->prio >= wakeup_prio ||
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p->prio >= curr->prio)
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return;
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disabled = atomic_inc_return(&tr->data[cpu]->disabled);
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if (unlikely(disabled != 1))
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goto out;
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/* interrupts should be off from try_to_wake_up */
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spin_lock(&wakeup_lock);
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/* check for races. */
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if (!tracer_enabled || p->prio >= wakeup_prio)
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goto out_locked;
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/* reset the trace */
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__wakeup_reset(tr);
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wakeup_cpu = task_cpu(p);
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wakeup_prio = p->prio;
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wakeup_task = p;
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get_task_struct(wakeup_task);
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local_save_flags(flags);
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tr->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu);
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trace_function(tr, tr->data[wakeup_cpu],
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CALLER_ADDR1, CALLER_ADDR2, flags);
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out_locked:
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spin_unlock(&wakeup_lock);
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out:
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atomic_dec(&tr->data[cpu]->disabled);
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}
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void wakeup_sched_wakeup(struct task_struct *wakee, struct task_struct *curr)
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{
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if (likely(!tracer_enabled))
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return;
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tracing_record_cmdline(curr);
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tracing_record_cmdline(wakee);
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wakeup_check_start(wakeup_trace, wakee, curr);
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}
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static void start_wakeup_tracer(struct trace_array *tr)
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{
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wakeup_reset(tr);
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/*
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* Don't let the tracer_enabled = 1 show up before
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* the wakeup_task is reset. This may be overkill since
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* wakeup_reset does a spin_unlock after setting the
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* wakeup_task to NULL, but I want to be safe.
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* This is a slow path anyway.
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*/
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smp_wmb();
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tracer_enabled = 1;
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return;
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}
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static void stop_wakeup_tracer(struct trace_array *tr)
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{
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tracer_enabled = 0;
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}
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static void wakeup_tracer_init(struct trace_array *tr)
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{
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wakeup_trace = tr;
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if (tr->ctrl)
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start_wakeup_tracer(tr);
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}
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static void wakeup_tracer_reset(struct trace_array *tr)
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{
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if (tr->ctrl) {
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stop_wakeup_tracer(tr);
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/* make sure we put back any tasks we are tracing */
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wakeup_reset(tr);
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}
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}
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static void wakeup_tracer_ctrl_update(struct trace_array *tr)
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{
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if (tr->ctrl)
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start_wakeup_tracer(tr);
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else
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stop_wakeup_tracer(tr);
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}
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static void wakeup_tracer_open(struct trace_iterator *iter)
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{
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/* stop the trace while dumping */
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if (iter->tr->ctrl)
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stop_wakeup_tracer(iter->tr);
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}
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static void wakeup_tracer_close(struct trace_iterator *iter)
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{
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/* forget about any processes we were recording */
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if (iter->tr->ctrl)
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start_wakeup_tracer(iter->tr);
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}
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static struct tracer wakeup_tracer __read_mostly =
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{
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.name = "wakeup",
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.init = wakeup_tracer_init,
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.reset = wakeup_tracer_reset,
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.open = wakeup_tracer_open,
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.close = wakeup_tracer_close,
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.ctrl_update = wakeup_tracer_ctrl_update,
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.print_max = 1,
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#ifdef CONFIG_FTRACE_SELFTEST
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.selftest = trace_selftest_startup_wakeup,
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#endif
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};
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__init static int init_wakeup_tracer(void)
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{
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int ret;
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ret = register_tracer(&wakeup_tracer);
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if (ret)
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return ret;
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return 0;
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}
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device_initcall(init_wakeup_tracer);
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