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tracing: Add function probe triggers to enable/disable events 

Add triggers to function tracer that lets an event get enabled or
disabled when a function is called:

format is:

 <function>:enable_event:<system>:<event>[:<count>]
 <function>:disable_event:<system>:<event>[:<count>]

 echo 'schedule:enable_event:sched:sched_switch' > /debug/tracing/set_ftrace_filter

Every time schedule is called, it will enable the sched_switch event.

 echo 'schedule:disable_event:sched:sched_switch:2' > /debug/tracing/set_ftrace_filter

The first two times schedule is called while the sched_switch
event is enabled, it will disable it. It will not count for a time
that the event is already disabled (or enabled for enable_event).

[ fixed return without mutex_unlock() - thanks to Dan Carpenter and smatch ]

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2013-03-12 19:35:13 -04:00 committed by Steven Rostedt
parent 417944c4c7
commit 3cd715de26
1 changed files with 279 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

279
kernel/trace/trace_events.c
View File

@ -1798,6 +1798,283 @@ __trace_add_event_dirs(struct trace_array *tr)
}
}
#ifdef CONFIG_DYNAMIC_FTRACE
/* Avoid typos */
#define ENABLE_EVENT_STR "enable_event"
#define DISABLE_EVENT_STR "disable_event"
struct event_probe_data {
struct ftrace_event_file *file;
unsigned long count;
int ref;
bool enable;
};
static struct ftrace_event_file *
find_event_file(struct trace_array *tr, const char *system, const char *event)
{
struct ftrace_event_file *file;
struct ftrace_event_call *call;
list_for_each_entry(file, &tr->events, list) {
call = file->event_call;
if (!call->name || !call->class || !call->class->reg)
continue;
if (call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
continue;
if (strcmp(event, call->name) == 0 &&
strcmp(system, call->class->system) == 0)
return file;
}
return NULL;
}
static void
event_enable_probe(unsigned long ip, unsigned long parent_ip, void **_data)
{
struct event_probe_data **pdata = (struct event_probe_data **)_data;
struct event_probe_data *data = *pdata;
if (!data)
return;
if (data->enable)
clear_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &data->file->flags);
else
set_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &data->file->flags);
}
static void
event_enable_count_probe(unsigned long ip, unsigned long parent_ip, void **_data)
{
struct event_probe_data **pdata = (struct event_probe_data **)_data;
struct event_probe_data *data = *pdata;
if (!data)
return;
if (!data->count)
return;
/* Skip if the event is in a state we want to switch to */
if (data->enable == !(data->file->flags & FTRACE_EVENT_FL_SOFT_DISABLED))
return;
if (data->count != -1)
(data->count)--;
event_enable_probe(ip, parent_ip, _data);
}
static int
event_enable_print(struct seq_file *m, unsigned long ip,
struct ftrace_probe_ops *ops, void *_data)
{
struct event_probe_data *data = _data;
seq_printf(m, "%ps:", (void *)ip);
seq_printf(m, "%s:%s:%s",
data->enable ? ENABLE_EVENT_STR : DISABLE_EVENT_STR,
data->file->event_call->class->system,
data->file->event_call->name);
if (data->count == -1)
seq_printf(m, ":unlimited\n");
else
seq_printf(m, ":count=%ld\n", data->count);
return 0;
}
static int
event_enable_init(struct ftrace_probe_ops *ops, unsigned long ip,
void **_data)
{
struct event_probe_data **pdata = (struct event_probe_data **)_data;
struct event_probe_data *data = *pdata;
data->ref++;
return 0;
}
static void
event_enable_free(struct ftrace_probe_ops *ops, unsigned long ip,
void **_data)
{
struct event_probe_data **pdata = (struct event_probe_data **)_data;
struct event_probe_data *data = *pdata;
if (WARN_ON_ONCE(data->ref <= 0))
return;
data->ref--;
if (!data->ref) {
/* Remove the SOFT_MODE flag */
__ftrace_event_enable_disable(data->file, 0, 1);
module_put(data->file->event_call->mod);
kfree(data);
}
*pdata = NULL;
}
static struct ftrace_probe_ops event_enable_probe_ops = {
.func = event_enable_probe,
.print = event_enable_print,
.init = event_enable_init,
.free = event_enable_free,
};
static struct ftrace_probe_ops event_enable_count_probe_ops = {
.func = event_enable_count_probe,
.print = event_enable_print,
.init = event_enable_init,
.free = event_enable_free,
};
static struct ftrace_probe_ops event_disable_probe_ops = {
.func = event_enable_probe,
.print = event_enable_print,
.init = event_enable_init,
.free = event_enable_free,
};
static struct ftrace_probe_ops event_disable_count_probe_ops = {
.func = event_enable_count_probe,
.print = event_enable_print,
.init = event_enable_init,
.free = event_enable_free,
};
static int
event_enable_func(struct ftrace_hash *hash,
char *glob, char *cmd, char *param, int enabled)
{
struct trace_array *tr = top_trace_array();
struct ftrace_event_file *file;
struct ftrace_probe_ops *ops;
struct event_probe_data *data;
const char *system;
const char *event;
char *number;
bool enable;
int ret;
/* hash funcs only work with set_ftrace_filter */
if (!enabled)
return -EINVAL;
if (!param)
return -EINVAL;
system = strsep(&param, ":");
if (!param)
return -EINVAL;
event = strsep(&param, ":");
mutex_lock(&event_mutex);
ret = -EINVAL;
file = find_event_file(tr, system, event);
if (!file)
goto out;
enable = strcmp(cmd, ENABLE_EVENT_STR) == 0;
if (enable)
ops = param ? &event_enable_count_probe_ops : &event_enable_probe_ops;
else
ops = param ? &event_disable_count_probe_ops : &event_disable_probe_ops;
if (glob[0] == '!') {
unregister_ftrace_function_probe_func(glob+1, ops);
ret = 0;
goto out;
}
ret = -ENOMEM;
data = kzalloc(sizeof(*data), GFP_KERNEL);
if (!data)
goto out;
data->enable = enable;
data->count = -1;
data->file = file;
if (!param)
goto out_reg;
number = strsep(&param, ":");
ret = -EINVAL;
if (!strlen(number))
goto out_free;
/*
* We use the callback data field (which is a pointer)
* as our counter.
*/
ret = kstrtoul(number, 0, &data->count);
if (ret)
goto out_free;
out_reg:
/* Don't let event modules unload while probe registered */
ret = try_module_get(file->event_call->mod);
if (!ret)
goto out_free;
ret = __ftrace_event_enable_disable(file, 1, 1);
if (ret < 0)
goto out_put;
ret = register_ftrace_function_probe(glob, ops, data);
if (!ret)
goto out_disable;
out:
mutex_unlock(&event_mutex);
return ret;
out_disable:
__ftrace_event_enable_disable(file, 0, 1);
out_put:
module_put(file->event_call->mod);
out_free:
kfree(data);
goto out;
}
static struct ftrace_func_command event_enable_cmd = {
.name = ENABLE_EVENT_STR,
.func = event_enable_func,
};
static struct ftrace_func_command event_disable_cmd = {
.name = DISABLE_EVENT_STR,
.func = event_enable_func,
};
static __init int register_event_cmds(void)
{
int ret;
ret = register_ftrace_command(&event_enable_cmd);
if (WARN_ON(ret < 0))
return ret;
ret = register_ftrace_command(&event_disable_cmd);
if (WARN_ON(ret < 0))
unregister_ftrace_command(&event_enable_cmd);
return ret;
}
#else
static inline int register_event_cmds(void) { return 0; }
#endif /* CONFIG_DYNAMIC_FTRACE */
/*
* The top level array has already had its ftrace_event_file
* descriptors created in order to allow for early events to
@ -2058,6 +2335,8 @@ static __init int event_trace_enable(void)
trace_printk_start_comm();
register_event_cmds();
return 0;
}