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007c05d4d2
We have two markers now that are enabled on sched_switch. One that records the context switching and the other that records task wake ups. Currently we enable the tracing first and then set the markers. This causes some confusing traces: # tracer: sched_switch # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | trace-cmd-3973 [00] 115.834817: 3973:120:R + 3: 0:S trace-cmd-3973 [01] 115.834910: 3973:120:R + 6: 0:S trace-cmd-3973 [02] 115.834910: 3973:120:R + 9: 0:S trace-cmd-3973 [03] 115.834910: 3973:120:R + 12: 0:S trace-cmd-3973 [02] 115.834910: 3973:120:R + 9: 0:S <idle>-0 [02] 115.834910: 0:140:R ==> 3973:120:R Here we see that trace-cmd with PID 3973 wakes up task 9 but the next line shows the idle task doing a context switch to task 3973. Enabling the tracing to _after_ the markers are set creates a much saner output: # tracer: sched_switch # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | <idle>-0 [02] 7922.634225: 0:140:R ==> 4790:120:R trace-cmd-4789 [03] 7922.634225: 0:140:R + 4790:120:R Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
287 lines
6.0 KiB
C
287 lines
6.0 KiB
C
/*
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* trace context switch
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*
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* Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
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*
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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/marker.h>
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#include <linux/ftrace.h>
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#include "trace.h"
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static struct trace_array *ctx_trace;
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static int __read_mostly tracer_enabled;
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static atomic_t sched_ref;
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static void
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sched_switch_func(void *private, void *__rq, struct task_struct *prev,
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struct task_struct *next)
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{
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struct trace_array **ptr = private;
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struct trace_array *tr = *ptr;
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struct trace_array_cpu *data;
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unsigned long flags;
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long disabled;
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int cpu;
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tracing_record_cmdline(prev);
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tracing_record_cmdline(next);
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if (!tracer_enabled)
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return;
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local_irq_save(flags);
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cpu = raw_smp_processor_id();
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data = tr->data[cpu];
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disabled = atomic_inc_return(&data->disabled);
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if (likely(disabled == 1))
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tracing_sched_switch_trace(tr, data, prev, next, flags);
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atomic_dec(&data->disabled);
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local_irq_restore(flags);
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}
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static notrace void
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sched_switch_callback(void *probe_data, void *call_data,
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const char *format, va_list *args)
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{
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struct task_struct *prev;
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struct task_struct *next;
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struct rq *__rq;
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if (!atomic_read(&sched_ref))
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return;
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/* skip prev_pid %d next_pid %d prev_state %ld */
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(void)va_arg(*args, int);
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(void)va_arg(*args, int);
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(void)va_arg(*args, long);
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__rq = va_arg(*args, typeof(__rq));
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prev = va_arg(*args, typeof(prev));
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next = va_arg(*args, typeof(next));
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/*
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* If tracer_switch_func only points to the local
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* switch func, it still needs the ptr passed to it.
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*/
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sched_switch_func(probe_data, __rq, prev, next);
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}
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static void
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wakeup_func(void *private, void *__rq, struct task_struct *wakee, struct
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task_struct *curr)
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{
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struct trace_array **ptr = private;
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struct trace_array *tr = *ptr;
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struct trace_array_cpu *data;
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unsigned long flags;
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long disabled;
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int cpu;
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if (!tracer_enabled)
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return;
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tracing_record_cmdline(curr);
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local_irq_save(flags);
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cpu = raw_smp_processor_id();
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data = tr->data[cpu];
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disabled = atomic_inc_return(&data->disabled);
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if (likely(disabled == 1))
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tracing_sched_wakeup_trace(tr, data, wakee, curr, flags);
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atomic_dec(&data->disabled);
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local_irq_restore(flags);
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}
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static notrace void
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wake_up_callback(void *probe_data, void *call_data,
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const char *format, va_list *args)
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{
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struct task_struct *curr;
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struct task_struct *task;
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struct rq *__rq;
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if (likely(!tracer_enabled))
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return;
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/* Skip pid %d state %ld */
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(void)va_arg(*args, int);
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(void)va_arg(*args, long);
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/* now get the meat: "rq %p task %p rq->curr %p" */
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__rq = va_arg(*args, typeof(__rq));
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task = va_arg(*args, typeof(task));
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curr = va_arg(*args, typeof(curr));
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tracing_record_cmdline(task);
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tracing_record_cmdline(curr);
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wakeup_func(probe_data, __rq, task, curr);
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}
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static void sched_switch_reset(struct trace_array *tr)
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{
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int cpu;
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tr->time_start = ftrace_now(tr->cpu);
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for_each_online_cpu(cpu)
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tracing_reset(tr->data[cpu]);
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}
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static int tracing_sched_register(void)
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{
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int ret;
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ret = marker_probe_register("kernel_sched_wakeup",
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"pid %d state %ld ## rq %p task %p rq->curr %p",
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wake_up_callback,
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&ctx_trace);
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if (ret) {
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pr_info("wakeup trace: Couldn't add marker"
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" probe to kernel_sched_wakeup\n");
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return ret;
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}
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ret = marker_probe_register("kernel_sched_wakeup_new",
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"pid %d state %ld ## rq %p task %p rq->curr %p",
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wake_up_callback,
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&ctx_trace);
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if (ret) {
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pr_info("wakeup trace: Couldn't add marker"
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" probe to kernel_sched_wakeup_new\n");
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goto fail_deprobe;
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}
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ret = marker_probe_register("kernel_sched_schedule",
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"prev_pid %d next_pid %d prev_state %ld "
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"## rq %p prev %p next %p",
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sched_switch_callback,
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&ctx_trace);
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if (ret) {
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pr_info("sched trace: Couldn't add marker"
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" probe to kernel_sched_schedule\n");
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goto fail_deprobe_wake_new;
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}
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return ret;
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fail_deprobe_wake_new:
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marker_probe_unregister("kernel_sched_wakeup_new",
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wake_up_callback,
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&ctx_trace);
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fail_deprobe:
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marker_probe_unregister("kernel_sched_wakeup",
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wake_up_callback,
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&ctx_trace);
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return ret;
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}
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static void tracing_sched_unregister(void)
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{
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marker_probe_unregister("kernel_sched_schedule",
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sched_switch_callback,
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&ctx_trace);
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marker_probe_unregister("kernel_sched_wakeup_new",
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wake_up_callback,
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&ctx_trace);
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marker_probe_unregister("kernel_sched_wakeup",
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wake_up_callback,
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&ctx_trace);
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}
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static void tracing_start_sched_switch(void)
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{
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long ref;
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ref = atomic_inc_return(&sched_ref);
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if (ref == 1)
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tracing_sched_register();
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}
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static void tracing_stop_sched_switch(void)
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{
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long ref;
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ref = atomic_dec_and_test(&sched_ref);
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if (ref)
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tracing_sched_unregister();
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}
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void tracing_start_cmdline_record(void)
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{
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tracing_start_sched_switch();
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}
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void tracing_stop_cmdline_record(void)
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{
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tracing_stop_sched_switch();
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}
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static void start_sched_trace(struct trace_array *tr)
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{
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sched_switch_reset(tr);
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tracing_start_cmdline_record();
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tracer_enabled = 1;
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}
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static void stop_sched_trace(struct trace_array *tr)
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{
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tracer_enabled = 0;
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tracing_stop_cmdline_record();
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}
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static void sched_switch_trace_init(struct trace_array *tr)
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{
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ctx_trace = tr;
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if (tr->ctrl)
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start_sched_trace(tr);
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}
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static void sched_switch_trace_reset(struct trace_array *tr)
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{
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if (tr->ctrl)
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stop_sched_trace(tr);
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}
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static void sched_switch_trace_ctrl_update(struct trace_array *tr)
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{
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/* When starting a new trace, reset the buffers */
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if (tr->ctrl)
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start_sched_trace(tr);
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else
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stop_sched_trace(tr);
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}
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static struct tracer sched_switch_trace __read_mostly =
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{
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.name = "sched_switch",
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.init = sched_switch_trace_init,
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.reset = sched_switch_trace_reset,
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.ctrl_update = sched_switch_trace_ctrl_update,
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#ifdef CONFIG_FTRACE_SELFTEST
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.selftest = trace_selftest_startup_sched_switch,
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#endif
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};
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__init static int init_sched_switch_trace(void)
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{
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int ret = 0;
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if (atomic_read(&sched_ref))
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ret = tracing_sched_register();
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if (ret) {
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pr_info("error registering scheduler trace\n");
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return ret;
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}
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return register_tracer(&sched_switch_trace);
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}
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device_initcall(init_sched_switch_trace);
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