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tracing: Add function-trace option to disable function tracing of latency tracers 

Currently, the only way to stop the latency tracers from doing function
tracing is to fully disable the function tracer from the proc file
system:

  echo 0 > /proc/sys/kernel/ftrace_enabled

This is a big hammer approach as it disables function tracing for
all users. This includes kprobes, perf, stack tracer, etc.

Instead, create a function-trace option that the latency tracers can
check to determine if it should enable function tracing or not.
This option can be set or cleared even while the tracer is active
and the tracers will disable or enable function tracing depending
on how the option was set.

Instead of using the proc file, disable latency function tracing with

  echo 0 > /debug/tracing/options/function-trace

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
hifive-unleashed-5.1
Steven Rostedt (Red Hat) 2013-03-14 12:10:40 -04:00 committed by Steven Rostedt
parent 4df297129f
commit 328df4759c
4 changed files with 112 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
kernel/trace/trace.c
View File

@ -328,7 +328,7 @@ static inline void trace_access_lock_init(void)
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE |
TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS;
TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS | TRACE_ITER_FUNCTION;
/**
* tracing_on - enable tracing buffers
@ -635,6 +635,7 @@ static const char *trace_options[] = {
"disable_on_free",
"irq-info",
"markers",
"function-trace",
NULL
};

1
kernel/trace/trace.h
View File

@ -867,6 +867,7 @@ enum trace_iterator_flags {
TRACE_ITER_STOP_ON_FREE = 0x400000,
TRACE_ITER_IRQ_INFO = 0x800000,
TRACE_ITER_MARKERS = 0x1000000,
TRACE_ITER_FUNCTION = 0x2000000,
};
/*

67
kernel/trace/trace_irqsoff.c
View File

@ -33,6 +33,7 @@ enum {
static int trace_type __read_mostly;
static int save_flags;
static bool function_enabled;
static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
static int start_irqsoff_tracer(struct trace_array *tr, int graph);
@ -528,15 +529,60 @@ void trace_preempt_off(unsigned long a0, unsigned long a1)
}
#endif /* CONFIG_PREEMPT_TRACER */
static int start_irqsoff_tracer(struct trace_array *tr, int graph)
static int register_irqsoff_function(int graph, int set)
{
int ret = 0;
int ret;
if (!graph)
ret = register_ftrace_function(&trace_ops);
else
/* '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(&irqsoff_graph_return,
&irqsoff_graph_entry);
else
ret = register_ftrace_function(&trace_ops);
if (!ret)
function_enabled = true;
return ret;
}
static void unregister_irqsoff_function(int graph)
{
if (!function_enabled)
return;
if (graph)
unregister_ftrace_graph();
else
unregister_ftrace_function(&trace_ops);
function_enabled = false;
}
static void irqsoff_function_set(int set)
{
if (set)
register_irqsoff_function(is_graph(), 1);
else
unregister_irqsoff_function(is_graph());
}
static int irqsoff_flag_changed(struct tracer *tracer, u32 mask, int set)
{
if (mask & TRACE_ITER_FUNCTION)
irqsoff_function_set(set);
return trace_keep_overwrite(tracer, mask, set);
}
static int start_irqsoff_tracer(struct trace_array *tr, int graph)
{
int ret;
ret = register_irqsoff_function(graph, 0);
if (!ret && tracing_is_enabled())
tracer_enabled = 1;
@ -550,10 +596,7 @@ static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
{
tracer_enabled = 0;
if (!graph)
unregister_ftrace_function(&trace_ops);
else
unregister_ftrace_graph();
unregister_irqsoff_function(graph);
}
static void __irqsoff_tracer_init(struct trace_array *tr)
@ -615,7 +658,7 @@ static struct tracer irqsoff_tracer __read_mostly =
.print_line = irqsoff_print_line,
.flags = &tracer_flags,
.set_flag = irqsoff_set_flag,
.flag_changed = trace_keep_overwrite,
.flag_changed = irqsoff_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_irqsoff,
#endif
@ -649,7 +692,7 @@ static struct tracer preemptoff_tracer __read_mostly =
.print_line = irqsoff_print_line,
.flags = &tracer_flags,
.set_flag = irqsoff_set_flag,
.flag_changed = trace_keep_overwrite,
.flag_changed = irqsoff_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_preemptoff,
#endif
@ -685,7 +728,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
.print_line = irqsoff_print_line,
.flags = &tracer_flags,
.set_flag = irqsoff_set_flag,
.flag_changed = trace_keep_overwrite,
.flag_changed = irqsoff_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_preemptirqsoff,
#endif

65
kernel/trace/trace_sched_wakeup.c
View File

@ -37,6 +37,7 @@ 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
@ -134,15 +135,60 @@ static struct ftrace_ops trace_ops __read_mostly =
};
#endif /* CONFIG_FUNCTION_TRACER */
static int register_wakeup_function(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(&trace_ops);
if (!ret)
function_enabled = true;
return ret;
}
static void unregister_wakeup_function(int graph)
{
if (!function_enabled)
return;
if (graph)
unregister_ftrace_graph();
else
unregister_ftrace_function(&trace_ops);
function_enabled = false;
}
static void wakeup_function_set(int set)
{
if (set)
register_wakeup_function(is_graph(), 1);
else
unregister_wakeup_function(is_graph());
}
static int wakeup_flag_changed(struct tracer *tracer, u32 mask, int set)
{
if (mask & TRACE_ITER_FUNCTION)
wakeup_function_set(set);
return trace_keep_overwrite(tracer, mask, set);
}
static int start_func_tracer(int graph)
{
int ret;
if (!graph)
ret = register_ftrace_function(&trace_ops);
else
ret = register_ftrace_graph(&wakeup_graph_return,
&wakeup_graph_entry);
ret = register_wakeup_function(graph, 0);
if (!ret && tracing_is_enabled())
tracer_enabled = 1;
@ -156,10 +202,7 @@ static void stop_func_tracer(int graph)
{
tracer_enabled = 0;
if (!graph)
unregister_ftrace_function(&trace_ops);
else
unregister_ftrace_graph();
unregister_wakeup_function(graph);
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
@ -600,7 +643,7 @@ static struct tracer wakeup_tracer __read_mostly =
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
.flag_changed = trace_keep_overwrite,
.flag_changed = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
@ -622,7 +665,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
.flag_changed = trace_keep_overwrite,
.flag_changed = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif