linux/kernel/trace/trace_sched_wakeup.c
Steven Rostedt (Red Hat) b1169cc69b tracing: Remove mock up poll wait function
Now that the ring buffer has a built in way to wake up readers
when there's data, using irq_work such that it is safe to do it
in any context. But it was still using the old "poor man's"
wait polling that checks every 1/10 of a second to see if it
should wake up a waiter. This makes the latency for a wake up
excruciatingly long. No need to do that anymore.

Completely remove the different wait_poll types from the tracers
and have them all use the default one now.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2014-04-30 08:40:05 -04:00

763 lines
17 KiB
C

/*
* 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 Nadia Yvette Chambers
*/
#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 <linux/sched/rt.h>
#include <linux/sched/deadline.h>
#include <trace/events/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 int wakeup_current_cpu;
static unsigned wakeup_prio = -1;
static int wakeup_rt;
static int wakeup_dl;
static int tracing_dl = 0;
static arch_spinlock_t wakeup_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
static void wakeup_reset(struct trace_array *tr);
static void __wakeup_reset(struct trace_array *tr);
static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
static void wakeup_graph_return(struct ftrace_graph_ret *trace);
static int save_flags;
static bool function_enabled;
#define TRACE_DISPLAY_GRAPH 1
static struct tracer_opt trace_opts[] = {
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* display latency trace as call graph */
{ TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
#endif
{ } /* Empty entry */
};
static struct tracer_flags tracer_flags = {
.val = 0,
.opts = trace_opts,
};
#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
#ifdef CONFIG_FUNCTION_TRACER
/*
* Prologue for the wakeup function tracers.
*
* Returns 1 if it is OK to continue, and preemption
* is disabled and data->disabled is incremented.
* 0 if the trace is to be ignored, and preemption
* is not disabled and data->disabled is
* kept the same.
*
* Note, this function is also used outside this ifdef but
* inside the #ifdef of the function graph tracer below.
* This is OK, since the function graph tracer is
* dependent on the function tracer.
*/
static int
func_prolog_preempt_disable(struct trace_array *tr,
struct trace_array_cpu **data,
int *pc)
{
long disabled;
int cpu;
if (likely(!wakeup_task))
return 0;
*pc = preempt_count();
preempt_disable_notrace();
cpu = raw_smp_processor_id();
if (cpu != wakeup_current_cpu)
goto out_enable;
*data = per_cpu_ptr(tr->trace_buffer.data, cpu);
disabled = atomic_inc_return(&(*data)->disabled);
if (unlikely(disabled != 1))
goto out;
return 1;
out:
atomic_dec(&(*data)->disabled);
out_enable:
preempt_enable_notrace();
return 0;
}
/*
* wakeup uses its own tracer function to keep the overhead down:
*/
static void
wakeup_tracer_call(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *pt_regs)
{
struct trace_array *tr = wakeup_trace;
struct trace_array_cpu *data;
unsigned long flags;
int pc;
if (!func_prolog_preempt_disable(tr, &data, &pc))
return;
local_irq_save(flags);
trace_function(tr, ip, parent_ip, flags, pc);
local_irq_restore(flags);
atomic_dec(&data->disabled);
preempt_enable_notrace();
}
#endif /* CONFIG_FUNCTION_TRACER */
static int register_wakeup_function(struct trace_array *tr, int graph, int set)
{
int ret;
/* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
if (function_enabled || (!set && !(trace_flags & TRACE_ITER_FUNCTION)))
return 0;
if (graph)
ret = register_ftrace_graph(&wakeup_graph_return,
&wakeup_graph_entry);
else
ret = register_ftrace_function(tr->ops);
if (!ret)
function_enabled = true;
return ret;
}
static void unregister_wakeup_function(struct trace_array *tr, int graph)
{
if (!function_enabled)
return;
if (graph)
unregister_ftrace_graph();
else
unregister_ftrace_function(tr->ops);
function_enabled = false;
}
static void wakeup_function_set(struct trace_array *tr, int set)
{
if (set)
register_wakeup_function(tr, is_graph(), 1);
else
unregister_wakeup_function(tr, is_graph());
}
static int wakeup_flag_changed(struct trace_array *tr, u32 mask, int set)
{
struct tracer *tracer = tr->current_trace;
if (mask & TRACE_ITER_FUNCTION)
wakeup_function_set(tr, set);
return trace_keep_overwrite(tracer, mask, set);
}
static int start_func_tracer(struct trace_array *tr, int graph)
{
int ret;
ret = register_wakeup_function(tr, graph, 0);
if (!ret && tracing_is_enabled())
tracer_enabled = 1;
else
tracer_enabled = 0;
return ret;
}
static void stop_func_tracer(struct trace_array *tr, int graph)
{
tracer_enabled = 0;
unregister_wakeup_function(tr, graph);
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int
wakeup_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
{
if (!(bit & TRACE_DISPLAY_GRAPH))
return -EINVAL;
if (!(is_graph() ^ set))
return 0;
stop_func_tracer(tr, !set);
wakeup_reset(wakeup_trace);
tr->max_latency = 0;
return start_func_tracer(tr, set);
}
static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
{
struct trace_array *tr = wakeup_trace;
struct trace_array_cpu *data;
unsigned long flags;
int pc, ret = 0;
if (!func_prolog_preempt_disable(tr, &data, &pc))
return 0;
local_save_flags(flags);
ret = __trace_graph_entry(tr, trace, flags, pc);
atomic_dec(&data->disabled);
preempt_enable_notrace();
return ret;
}
static void wakeup_graph_return(struct ftrace_graph_ret *trace)
{
struct trace_array *tr = wakeup_trace;
struct trace_array_cpu *data;
unsigned long flags;
int pc;
if (!func_prolog_preempt_disable(tr, &data, &pc))
return;
local_save_flags(flags);
__trace_graph_return(tr, trace, flags, pc);
atomic_dec(&data->disabled);
preempt_enable_notrace();
return;
}
static void wakeup_trace_open(struct trace_iterator *iter)
{
if (is_graph())
graph_trace_open(iter);
}
static void wakeup_trace_close(struct trace_iterator *iter)
{
if (iter->private)
graph_trace_close(iter);
}
#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \
TRACE_GRAPH_PRINT_ABS_TIME | \
TRACE_GRAPH_PRINT_DURATION)
static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
{
/*
* In graph mode call the graph tracer output function,
* otherwise go with the TRACE_FN event handler
*/
if (is_graph())
return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
return TRACE_TYPE_UNHANDLED;
}
static void wakeup_print_header(struct seq_file *s)
{
if (is_graph())
print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
else
trace_default_header(s);
}
static void
__trace_function(struct trace_array *tr,
unsigned long ip, unsigned long parent_ip,
unsigned long flags, int pc)
{
if (is_graph())
trace_graph_function(tr, ip, parent_ip, flags, pc);
else
trace_function(tr, ip, parent_ip, flags, pc);
}
#else
#define __trace_function trace_function
static int
wakeup_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
{
return -EINVAL;
}
static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
{
return -1;
}
static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
{
return TRACE_TYPE_UNHANDLED;
}
static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
static void wakeup_trace_open(struct trace_iterator *iter) { }
static void wakeup_trace_close(struct trace_iterator *iter) { }
#ifdef CONFIG_FUNCTION_TRACER
static void wakeup_print_header(struct seq_file *s)
{
trace_default_header(s);
}
#else
static void wakeup_print_header(struct seq_file *s)
{
trace_latency_header(s);
}
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
/*
* Should this new latency be reported/recorded?
*/
static int report_latency(struct trace_array *tr, cycle_t delta)
{
if (tracing_thresh) {
if (delta < tracing_thresh)
return 0;
} else {
if (delta <= tr->max_latency)
return 0;
}
return 1;
}
static void
probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
{
if (task != wakeup_task)
return;
wakeup_current_cpu = cpu;
}
static void notrace
probe_wakeup_sched_switch(void *ignore,
struct task_struct *prev, struct task_struct *next)
{
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();
/* disable local data, not wakeup_cpu data */
cpu = raw_smp_processor_id();
disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
if (likely(disabled != 1))
goto out;
local_irq_save(flags);
arch_spin_lock(&wakeup_lock);
/* We could race with grabbing wakeup_lock */
if (unlikely(!tracer_enabled || next != wakeup_task))
goto out_unlock;
/* The task we are waiting for is waking up */
data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);
__trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
T0 = data->preempt_timestamp;
T1 = ftrace_now(cpu);
delta = T1-T0;
if (!report_latency(wakeup_trace, delta))
goto out_unlock;
if (likely(!is_tracing_stopped())) {
wakeup_trace->max_latency = delta;
update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
}
out_unlock:
__wakeup_reset(wakeup_trace);
arch_spin_unlock(&wakeup_lock);
local_irq_restore(flags);
out:
atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
}
static void __wakeup_reset(struct trace_array *tr)
{
wakeup_cpu = -1;
wakeup_prio = -1;
tracing_dl = 0;
if (wakeup_task)
put_task_struct(wakeup_task);
wakeup_task = NULL;
}
static void wakeup_reset(struct trace_array *tr)
{
unsigned long flags;
tracing_reset_online_cpus(&tr->trace_buffer);
local_irq_save(flags);
arch_spin_lock(&wakeup_lock);
__wakeup_reset(tr);
arch_spin_unlock(&wakeup_lock);
local_irq_restore(flags);
}
static void
probe_wakeup(void *ignore, struct task_struct *p, int success)
{
struct trace_array_cpu *data;
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);
/*
* Semantic is like this:
* - wakeup tracer handles all tasks in the system, independently
* from their scheduling class;
* - wakeup_rt tracer handles tasks belonging to sched_dl and
* sched_rt class;
* - wakeup_dl handles tasks belonging to sched_dl class only.
*/
if (tracing_dl || (wakeup_dl && !dl_task(p)) ||
(wakeup_rt && !dl_task(p) && !rt_task(p)) ||
(!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio)))
return;
pc = preempt_count();
disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
if (unlikely(disabled != 1))
goto out;
/* interrupts should be off from try_to_wake_up */
arch_spin_lock(&wakeup_lock);
/* check for races. */
if (!tracer_enabled || tracing_dl ||
(!dl_task(p) && p->prio >= wakeup_prio))
goto out_locked;
/* reset the trace */
__wakeup_reset(wakeup_trace);
wakeup_cpu = task_cpu(p);
wakeup_current_cpu = wakeup_cpu;
wakeup_prio = p->prio;
/*
* Once you start tracing a -deadline task, don't bother tracing
* another task until the first one wakes up.
*/
if (dl_task(p))
tracing_dl = 1;
else
tracing_dl = 0;
wakeup_task = p;
get_task_struct(wakeup_task);
local_save_flags(flags);
data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);
data->preempt_timestamp = ftrace_now(cpu);
tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
/*
* We must be careful in using CALLER_ADDR2. But since wake_up
* is not called by an assembly function (where as schedule is)
* it should be safe to use it here.
*/
__trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
out_locked:
arch_spin_unlock(&wakeup_lock);
out:
atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
}
static void start_wakeup_tracer(struct trace_array *tr)
{
int ret;
ret = register_trace_sched_wakeup(probe_wakeup, NULL);
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, NULL);
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, NULL);
if (ret) {
pr_info("sched trace: Couldn't activate tracepoint"
" probe to kernel_sched_switch\n");
goto fail_deprobe_wake_new;
}
ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
if (ret) {
pr_info("wakeup trace: Couldn't activate tracepoint"
" probe to kernel_sched_migrate_task\n");
return;
}
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();
if (start_func_tracer(tr, is_graph()))
printk(KERN_ERR "failed to start wakeup tracer\n");
return;
fail_deprobe_wake_new:
unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
fail_deprobe:
unregister_trace_sched_wakeup(probe_wakeup, NULL);
}
static void stop_wakeup_tracer(struct trace_array *tr)
{
tracer_enabled = 0;
stop_func_tracer(tr, is_graph());
unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
unregister_trace_sched_wakeup(probe_wakeup, NULL);
unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
}
static bool wakeup_busy;
static int __wakeup_tracer_init(struct trace_array *tr)
{
save_flags = trace_flags;
/* non overwrite screws up the latency tracers */
set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
tr->max_latency = 0;
wakeup_trace = tr;
ftrace_init_array_ops(tr, wakeup_tracer_call);
start_wakeup_tracer(tr);
wakeup_busy = true;
return 0;
}
static int wakeup_tracer_init(struct trace_array *tr)
{
if (wakeup_busy)
return -EBUSY;
wakeup_dl = 0;
wakeup_rt = 0;
return __wakeup_tracer_init(tr);
}
static int wakeup_rt_tracer_init(struct trace_array *tr)
{
if (wakeup_busy)
return -EBUSY;
wakeup_dl = 0;
wakeup_rt = 1;
return __wakeup_tracer_init(tr);
}
static int wakeup_dl_tracer_init(struct trace_array *tr)
{
if (wakeup_busy)
return -EBUSY;
wakeup_dl = 1;
wakeup_rt = 0;
return __wakeup_tracer_init(tr);
}
static void wakeup_tracer_reset(struct trace_array *tr)
{
int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
stop_wakeup_tracer(tr);
/* make sure we put back any tasks we are tracing */
wakeup_reset(tr);
set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
ftrace_reset_array_ops(tr);
wakeup_busy = false;
}
static void wakeup_tracer_start(struct trace_array *tr)
{
wakeup_reset(tr);
tracer_enabled = 1;
}
static void wakeup_tracer_stop(struct trace_array *tr)
{
tracer_enabled = 0;
}
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,
.print_max = true,
.print_header = wakeup_print_header,
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
.flag_changed = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
.open = wakeup_trace_open,
.close = wakeup_trace_close,
.allow_instances = true,
.use_max_tr = true,
};
static struct tracer wakeup_rt_tracer __read_mostly =
{
.name = "wakeup_rt",
.init = wakeup_rt_tracer_init,
.reset = wakeup_tracer_reset,
.start = wakeup_tracer_start,
.stop = wakeup_tracer_stop,
.print_max = true,
.print_header = wakeup_print_header,
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
.flag_changed = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
.open = wakeup_trace_open,
.close = wakeup_trace_close,
.allow_instances = true,
.use_max_tr = true,
};
static struct tracer wakeup_dl_tracer __read_mostly =
{
.name = "wakeup_dl",
.init = wakeup_dl_tracer_init,
.reset = wakeup_tracer_reset,
.start = wakeup_tracer_start,
.stop = wakeup_tracer_stop,
.print_max = true,
.print_header = wakeup_print_header,
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
.flag_changed = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
.open = wakeup_trace_open,
.close = wakeup_trace_close,
.use_max_tr = true,
};
__init static int init_wakeup_tracer(void)
{
int ret;
ret = register_tracer(&wakeup_tracer);
if (ret)
return ret;
ret = register_tracer(&wakeup_rt_tracer);
if (ret)
return ret;
ret = register_tracer(&wakeup_dl_tracer);
if (ret)
return ret;
return 0;
}
core_initcall(init_wakeup_tracer);