kernel/trace/trace_sched_switch.c

   1 /*
   2  * trace context switch
   3  *
   4  * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
   5  *
   6  */
   7 #include <linux/module.h>
   8 #include <linux/fs.h>
   9 #include <linux/debugfs.h>
  10 #include <linux/kallsyms.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/marker.h>
  13 #include <linux/ftrace.h>
  14
  15 #include "trace.h"
  16
  17 static struct trace_array       *ctx_trace;
  18 static int __read_mostly        tracer_enabled;
  19
  20 static void
  21 ctx_switch_func(struct task_struct *prev, struct task_struct *next)
  22 {
  23         struct trace_array *tr = ctx_trace;
  24         struct trace_array_cpu *data;
  25         unsigned long flags;
  26         long disabled;
  27         int cpu;
  28
  29         if (!tracer_enabled)
  30                 return;
  31
  32         local_irq_save(flags);
  33         cpu = raw_smp_processor_id();
  34         data = tr->data[cpu];
  35         disabled = atomic_inc_return(&data->disabled);
  36
  37         if (likely(disabled == 1))
  38                 tracing_sched_switch_trace(tr, data, prev, next, flags);
  39
  40         atomic_dec(&data->disabled);
  41         local_irq_restore(flags);
  42 }
  43
  44 static void wakeup_func(struct task_struct *wakee, struct task_struct *curr)
  45 {
  46         struct trace_array *tr = ctx_trace;
  47         struct trace_array_cpu *data;
  48         unsigned long flags;
  49         long disabled;
  50         int cpu;
  51
  52         if (!tracer_enabled)
  53                 return;
  54
  55         local_irq_save(flags);
  56         cpu = raw_smp_processor_id();
  57         data = tr->data[cpu];
  58         disabled = atomic_inc_return(&data->disabled);
  59
  60         if (likely(disabled == 1))
  61                 tracing_sched_wakeup_trace(tr, data, wakee, curr, flags);
  62
  63         atomic_dec(&data->disabled);
  64         local_irq_restore(flags);
  65 }
  66
  67 void ftrace_ctx_switch(struct task_struct *prev, struct task_struct *next)
  68 {
  69         tracing_record_cmdline(prev);
  70
  71         /*
  72          * If tracer_switch_func only points to the local
  73          * switch func, it still needs the ptr passed to it.
  74          */
  75         ctx_switch_func(prev, next);
  76
  77         /*
  78          * Chain to the wakeup tracer (this is a NOP if disabled):
  79          */
  80         wakeup_sched_switch(prev, next);
  81 }
  82
  83 void
  84 ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr)
  85 {
  86         tracing_record_cmdline(curr);
  87
  88         wakeup_func(wakee, curr);
  89
  90         /*
  91          * Chain to the wakeup tracer (this is a NOP if disabled):
  92          */
  93         wakeup_sched_wakeup(wakee, curr);
  94 }
  95
  96 static void sched_switch_reset(struct trace_array *tr)
  97 {
  98         int cpu;
  99
 100         tr->time_start = ftrace_now(tr->cpu);
 101
 102         for_each_online_cpu(cpu)
 103                 tracing_reset(tr->data[cpu]);
 104 }
 105
 106 static void start_sched_trace(struct trace_array *tr)
 107 {
 108         sched_switch_reset(tr);
 109         tracer_enabled = 1;
 110 }
 111
 112 static void stop_sched_trace(struct trace_array *tr)
 113 {
 114         tracer_enabled = 0;
 115 }
 116
 117 static void sched_switch_trace_init(struct trace_array *tr)
 118 {
 119         ctx_trace = tr;
 120
 121         if (tr->ctrl)
 122                 start_sched_trace(tr);
 123 }
 124
 125 static void sched_switch_trace_reset(struct trace_array *tr)
 126 {
 127         if (tr->ctrl)
 128                 stop_sched_trace(tr);
 129 }
 130
 131 static void sched_switch_trace_ctrl_update(struct trace_array *tr)
 132 {
 133         /* When starting a new trace, reset the buffers */
 134         if (tr->ctrl)
 135                 start_sched_trace(tr);
 136         else
 137                 stop_sched_trace(tr);
 138 }
 139
 140 static struct tracer sched_switch_trace __read_mostly =
 141 {
 142         .name           = "sched_switch",
 143         .init           = sched_switch_trace_init,
 144         .reset          = sched_switch_trace_reset,
 145         .ctrl_update    = sched_switch_trace_ctrl_update,
 146 #ifdef CONFIG_FTRACE_SELFTEST
 147         .selftest    = trace_selftest_startup_sched_switch,
 148 #endif
 149 };
 150
 151 __init static int init_sched_switch_trace(void)
 152 {
 153         return register_tracer(&sched_switch_trace);
 154 }
 155 device_initcall(init_sched_switch_trace);