/* * trace task wakeup timings * * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com> * * Based on code from the latency_tracer, that is: * * Copyright (C) 2004-2006 Ingo Molnar * Copyright (C) 2004 William Lee Irwin III */ #include <linux/module.h> #include <linux/fs.h> #include <linux/debugfs.h> #include <linux/kallsyms.h> #include <linux/uaccess.h> #include <linux/ftrace.h> #include <trace/sched.h> #include "trace.h" static struct trace_array *wakeup_trace; static int __read_mostly tracer_enabled; static struct task_struct *wakeup_task; static int wakeup_cpu; static unsigned wakeup_prio = -1; static raw_spinlock_t wakeup_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; static void __wakeup_reset(struct trace_array *tr); #ifdef CONFIG_FUNCTION_TRACER /* * irqsoff uses its own tracer function to keep the overhead down: */ static void wakeup_tracer_call(unsigned long ip, unsigned long parent_ip) { struct trace_array *tr = wakeup_trace; struct trace_array_cpu *data; unsigned long flags; long disabled; int resched; int cpu; int pc; if (likely(!wakeup_task)) return; pc = preempt_count(); resched = ftrace_preempt_disable(); cpu = raw_smp_processor_id(); data = tr->data[cpu]; disabled = atomic_inc_return(&data->disabled); if (unlikely(disabled != 1)) goto out; local_irq_save(flags); __raw_spin_lock(&wakeup_lock); if (unlikely(!wakeup_task)) goto unlock; /* * The task can't disappear because it needs to * wake up first, and we have the wakeup_lock. */ if (task_cpu(wakeup_task) != cpu) goto unlock; trace_function(tr, data, ip, parent_ip, flags, pc); unlock: __raw_spin_unlock(&wakeup_lock); local_irq_restore(flags); out: atomic_dec(&data->disabled); ftrace_preempt_enable(resched); } static struct ftrace_ops trace_ops __read_mostly = { .func = wakeup_tracer_call, }; #endif /* CONFIG_FUNCTION_TRACER */ /* * Should this new latency be reported/recorded? */ static int report_latency(cycle_t delta) { if (tracing_thresh) { if (delta < tracing_thresh) return 0; } else { if (delta <= tracing_max_latency) return 0; } return 1; } static void notrace probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next) { unsigned long latency = 0, t0 = 0, t1 = 0; struct trace_array_cpu *data; cycle_t T0, T1, delta; unsigned long flags; long disabled; int cpu; int pc; tracing_record_cmdline(prev); if (unlikely(!tracer_enabled)) return; /* * When we start a new trace, we set wakeup_task to NULL * and then set tracer_enabled = 1. We want to make sure * that another CPU does not see the tracer_enabled = 1 * and the wakeup_task with an older task, that might * actually be the same as next. */ smp_rmb(); if (next != wakeup_task) return; pc = preempt_count(); /* The task we are waiting for is waking up */ data = wakeup_trace->data[wakeup_cpu]; /* disable local data, not wakeup_cpu data */ cpu = raw_smp_processor_id(); disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); if (likely(disabled != 1)) goto out; local_irq_save(flags); __raw_spin_lock(&wakeup_lock); /* We could race with grabbing wakeup_lock */ if (unlikely(!tracer_enabled || next != wakeup_task)) goto out_unlock; trace_function(wakeup_trace, data, CALLER_ADDR1, CALLER_ADDR2, flags, pc); /* * usecs conversion is slow so we try to delay the conversion * as long as possible: */ T0 = data->preempt_timestamp; T1 = ftrace_now(cpu); delta = T1-T0; if (!report_latency(delta)) goto out_unlock; latency = nsecs_to_usecs(delta); tracing_max_latency = delta; t0 = nsecs_to_usecs(T0); t1 = nsecs_to_usecs(T1); update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu); out_unlock: __wakeup_reset(wakeup_trace); __raw_spin_unlock(&wakeup_lock); local_irq_restore(flags); out: atomic_dec(&wakeup_trace->data[cpu]->disabled); } static void __wakeup_reset(struct trace_array *tr) { struct trace_array_cpu *data; int cpu; for_each_possible_cpu(cpu) { data = tr->data[cpu]; tracing_reset(tr, cpu); } wakeup_cpu = -1; wakeup_prio = -1; if (wakeup_task) put_task_struct(wakeup_task); wakeup_task = NULL; } static void wakeup_reset(struct trace_array *tr) { unsigned long flags; local_irq_save(flags); __raw_spin_lock(&wakeup_lock); __wakeup_reset(tr); __raw_spin_unlock(&wakeup_lock); local_irq_restore(flags); } static void probe_wakeup(struct rq *rq, struct task_struct *p, int success) { int cpu = smp_processor_id(); unsigned long flags; long disabled; int pc; if (likely(!tracer_enabled)) return; tracing_record_cmdline(p); tracing_record_cmdline(current); if (likely(!rt_task(p)) || p->prio >= wakeup_prio || p->prio >= current->prio) return; pc = preempt_count(); disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled); if (unlikely(disabled != 1)) goto out; /* interrupts should be off from try_to_wake_up */ __raw_spin_lock(&wakeup_lock); /* check for races. */ if (!tracer_enabled || p->prio >= wakeup_prio) goto out_locked; /* reset the trace */ __wakeup_reset(wakeup_trace); wakeup_cpu = task_cpu(p); wakeup_prio = p->prio; wakeup_task = p; get_task_struct(wakeup_task); local_save_flags(flags); wakeup_trace->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu); trace_function(wakeup_trace, wakeup_trace->data[wakeup_cpu], CALLER_ADDR1, CALLER_ADDR2, flags, pc); out_locked: __raw_spin_unlock(&wakeup_lock); out: atomic_dec(&wakeup_trace->data[cpu]->disabled); } /* * save_tracer_enabled is used to save the state of the tracer_enabled * variable when we disable it when we open a trace output file. */ static int save_tracer_enabled; static void start_wakeup_tracer(struct trace_array *tr) { int ret; ret = register_trace_sched_wakeup(probe_wakeup); if (ret) { pr_info("wakeup trace: Couldn't activate tracepoint" " probe to kernel_sched_wakeup\n"); return; } ret = register_trace_sched_wakeup_new(probe_wakeup); if (ret) { pr_info("wakeup trace: Couldn't activate tracepoint" " probe to kernel_sched_wakeup_new\n"); goto fail_deprobe; } ret = register_trace_sched_switch(probe_wakeup_sched_switch); if (ret) { pr_info("sched trace: Couldn't activate tracepoint" " probe to kernel_sched_schedule\n"); goto fail_deprobe_wake_new; } wakeup_reset(tr); /* * Don't let the tracer_enabled = 1 show up before * the wakeup_task is reset. This may be overkill since * wakeup_reset does a spin_unlock after setting the * wakeup_task to NULL, but I want to be safe. * This is a slow path anyway. */ smp_wmb(); register_ftrace_function(&trace_ops); if (tracing_is_enabled()) { tracer_enabled = 1; save_tracer_enabled = 1; } else { tracer_enabled = 0; save_tracer_enabled = 0; } return; fail_deprobe_wake_new: unregister_trace_sched_wakeup_new(probe_wakeup); fail_deprobe: unregister_trace_sched_wakeup(probe_wakeup); } static void stop_wakeup_tracer(struct trace_array *tr) { tracer_enabled = 0; save_tracer_enabled = 0; unregister_ftrace_function(&trace_ops); unregister_trace_sched_switch(probe_wakeup_sched_switch); unregister_trace_sched_wakeup_new(probe_wakeup); unregister_trace_sched_wakeup(probe_wakeup); } static int wakeup_tracer_init(struct trace_array *tr) { wakeup_trace = tr; start_wakeup_tracer(tr); return 0; } static void wakeup_tracer_reset(struct trace_array *tr) { stop_wakeup_tracer(tr); /* make sure we put back any tasks we are tracing */ wakeup_reset(tr); } static void wakeup_tracer_start(struct trace_array *tr) { wakeup_reset(tr); tracer_enabled = 1; save_tracer_enabled = 1; } static void wakeup_tracer_stop(struct trace_array *tr) { tracer_enabled = 0; save_tracer_enabled = 0; } static void wakeup_tracer_open(struct trace_iterator *iter) { /* stop the trace while dumping */ tracer_enabled = 0; } static void wakeup_tracer_close(struct trace_iterator *iter) { /* forget about any processes we were recording */ if (save_tracer_enabled) { wakeup_reset(iter->tr); tracer_enabled = 1; } } static struct tracer wakeup_tracer __read_mostly = { .name = "wakeup", .init = wakeup_tracer_init, .reset = wakeup_tracer_reset, .start = wakeup_tracer_start, .stop = wakeup_tracer_stop, .open = wakeup_tracer_open, .close = wakeup_tracer_close, .print_max = 1, #ifdef CONFIG_FTRACE_SELFTEST .selftest = trace_selftest_startup_wakeup, #endif }; __init static int init_wakeup_tracer(void) { int ret; ret = register_tracer(&wakeup_tracer); if (ret) return ret; return 0; } device_initcall(init_wakeup_tracer);