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tracing: Add 'traceon' and 'traceoff' event trigger commands 

Add 'traceon' and 'traceoff' event_command commands.  traceon and
traceoff event triggers are added by the user via these commands in a
similar way and using practically the same syntax as the analagous
'traceon' and 'traceoff' ftrace function commands, but instead of
writing to the set_ftrace_filter file, the traceon and traceoff
triggers are written to the per-event 'trigger' files:

    echo 'traceon' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff' > .../tracing/events/somesys/someevent/trigger

The above command will turn tracing on or off whenever someevent is
hit.

This also adds a 'count' version that limits the number of times the
command will be invoked:

    echo 'traceon:N' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff:N' > .../tracing/events/somesys/someevent/trigger

Where N is the number of times the command will be invoked.

The above commands will will turn tracing on or off whenever someevent
is hit, but only N times.

Some common register/unregister_trigger() implementations of the
event_command reg()/unreg() callbacks are also provided, which add and
remove trigger instances to the per-event list of triggers, and
arm/disarm them as appropriate.  event_trigger_callback() is a
general-purpose event_command func() implementation that orchestrates
command parsing and registration for most normal commands.

Most event commands will use these, but some will override and
possibly reuse them.

The event_trigger_init(), event_trigger_free(), and
event_trigger_print() functions are meant to be common implementations
of the event_trigger_ops init(), free(), and print() ops,
respectively.

Most trigger_ops implementations will use these, but some will
override and possibly reuse them.

Link: http://lkml.kernel.org/r/00a52816703b98d2072947478dd6e2d70cde5197.1382622043.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2013-10-24 08:59:25 -05:00 committed by Steven Rostedt
parent 85f2b08268
commit 2a2df32115
2 changed files with 447 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/ftrace_event.h
View File

@ -345,6 +345,7 @@ struct ftrace_event_file {
enum event_trigger_type {
ETT_NONE = (0),
ETT_TRACE_ONOFF = (1 << 0),
};
extern void destroy_preds(struct ftrace_event_file *file);

446
kernel/trace/trace_events_trigger.c
View File

@ -28,6 +28,13 @@
static LIST_HEAD(trigger_commands);
static DEFINE_MUTEX(trigger_cmd_mutex);
static void
trigger_data_free(struct event_trigger_data *data)
{
synchronize_sched(); /* make sure current triggers exit before free */
kfree(data);
}
/**
* event_triggers_call - Call triggers associated with a trace event
* @file: The ftrace_event_file associated with the event
@ -224,6 +231,129 @@ const struct file_operations event_trigger_fops = {
.release = event_trigger_release,
};
/*
* Currently we only register event commands from __init, so mark this
* __init too.
*/
static __init int register_event_command(struct event_command *cmd)
{
struct event_command *p;
int ret = 0;
mutex_lock(&trigger_cmd_mutex);
list_for_each_entry(p, &trigger_commands, list) {
if (strcmp(cmd->name, p->name) == 0) {
ret = -EBUSY;
goto out_unlock;
}
}
list_add(&cmd->list, &trigger_commands);
out_unlock:
mutex_unlock(&trigger_cmd_mutex);
return ret;
}
/*
* Currently we only unregister event commands from __init, so mark
* this __init too.
*/
static __init int unregister_event_command(struct event_command *cmd)
{
struct event_command *p, *n;
int ret = -ENODEV;
mutex_lock(&trigger_cmd_mutex);
list_for_each_entry_safe(p, n, &trigger_commands, list) {
if (strcmp(cmd->name, p->name) == 0) {
ret = 0;
list_del_init(&p->list);
goto out_unlock;
}
}
out_unlock:
mutex_unlock(&trigger_cmd_mutex);
return ret;
}
/**
* event_trigger_print - Generic event_trigger_ops @print implementation
* @name: The name of the event trigger
* @m: The seq_file being printed to
* @data: Trigger-specific data
* @filter_str: filter_str to print, if present
*
* Common implementation for event triggers to print themselves.
*
* Usually wrapped by a function that simply sets the @name of the
* trigger command and then invokes this.
*
* Return: 0 on success, errno otherwise
*/
static int
event_trigger_print(const char *name, struct seq_file *m,
void *data, char *filter_str)
{
long count = (long)data;
seq_printf(m, "%s", name);
if (count == -1)
seq_puts(m, ":unlimited");
else
seq_printf(m, ":count=%ld", count);
if (filter_str)
seq_printf(m, " if %s\n", filter_str);
else
seq_puts(m, "\n");
return 0;
}
/**
* event_trigger_init - Generic event_trigger_ops @init implementation
* @ops: The trigger ops associated with the trigger
* @data: Trigger-specific data
*
* Common implementation of event trigger initialization.
*
* Usually used directly as the @init method in event trigger
* implementations.
*
* Return: 0 on success, errno otherwise
*/
static int
event_trigger_init(struct event_trigger_ops *ops,
struct event_trigger_data *data)
{
data->ref++;
return 0;
}
/**
* event_trigger_free - Generic event_trigger_ops @free implementation
* @ops: The trigger ops associated with the trigger
* @data: Trigger-specific data
*
* Common implementation of event trigger de-initialization.
*
* Usually used directly as the @free method in event trigger
* implementations.
*/
static void
event_trigger_free(struct event_trigger_ops *ops,
struct event_trigger_data *data)
{
if (WARN_ON_ONCE(data->ref <= 0))
return;
data->ref--;
if (!data->ref)
trigger_data_free(data);
}
static int trace_event_trigger_enable_disable(struct ftrace_event_file *file,
int trigger_enable)
{
@ -272,7 +402,323 @@ clear_event_triggers(struct trace_array *tr)
}
}
/**
* register_trigger - Generic event_command @reg implementation
* @glob: The raw string used to register the trigger
* @ops: The trigger ops associated with the trigger
* @data: Trigger-specific data to associate with the trigger
* @file: The ftrace_event_file associated with the event
*
* Common implementation for event trigger registration.
*
* Usually used directly as the @reg method in event command
* implementations.
*
* Return: 0 on success, errno otherwise
*/
static int register_trigger(char *glob, struct event_trigger_ops *ops,
struct event_trigger_data *data,
struct ftrace_event_file *file)
{
struct event_trigger_data *test;
int ret = 0;
list_for_each_entry_rcu(test, &file->triggers, list) {
if (test->cmd_ops->trigger_type == data->cmd_ops->trigger_type) {
ret = -EEXIST;
goto out;
}
}
if (data->ops->init) {
ret = data->ops->init(data->ops, data);
if (ret < 0)
goto out;
}
list_add_rcu(&data->list, &file->triggers);
ret++;
if (trace_event_trigger_enable_disable(file, 1) < 0) {
list_del_rcu(&data->list);
ret--;
}
out:
return ret;
}
/**
* unregister_trigger - Generic event_command @unreg implementation
* @glob: The raw string used to register the trigger
* @ops: The trigger ops associated with the trigger
* @test: Trigger-specific data used to find the trigger to remove
* @file: The ftrace_event_file associated with the event
*
* Common implementation for event trigger unregistration.
*
* Usually used directly as the @unreg method in event command
* implementations.
*/
static void unregister_trigger(char *glob, struct event_trigger_ops *ops,
struct event_trigger_data *test,
struct ftrace_event_file *file)
{
struct event_trigger_data *data;
bool unregistered = false;
list_for_each_entry_rcu(data, &file->triggers, list) {
if (data->cmd_ops->trigger_type == test->cmd_ops->trigger_type) {
unregistered = true;
list_del_rcu(&data->list);
trace_event_trigger_enable_disable(file, 0);
break;
}
}
if (unregistered && data->ops->free)
data->ops->free(data->ops, data);
}
/**
* event_trigger_callback - Generic event_command @func implementation
* @cmd_ops: The command ops, used for trigger registration
* @file: The ftrace_event_file associated with the event
* @glob: The raw string used to register the trigger
* @cmd: The cmd portion of the string used to register the trigger
* @param: The params portion of the string used to register the trigger
*
* Common implementation for event command parsing and trigger
* instantiation.
*
* Usually used directly as the @func method in event command
* implementations.
*
* Return: 0 on success, errno otherwise
*/
static int
event_trigger_callback(struct event_command *cmd_ops,
struct ftrace_event_file *file,
char *glob, char *cmd, char *param)
{
struct event_trigger_data *trigger_data;
struct event_trigger_ops *trigger_ops;
char *trigger = NULL;
char *number;
int ret;
/* separate the trigger from the filter (t:n [if filter]) */
if (param && isdigit(param[0]))
trigger = strsep(&param, " \t");
trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
ret = -ENOMEM;
trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
if (!trigger_data)
goto out;
trigger_data->count = -1;
trigger_data->ops = trigger_ops;
trigger_data->cmd_ops = cmd_ops;
INIT_LIST_HEAD(&trigger_data->list);
if (glob[0] == '!') {
cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
kfree(trigger_data);
ret = 0;
goto out;
}
if (trigger) {
number = strsep(&trigger, ":");
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, &trigger_data->count);
if (ret)
goto out_free;
}
if (!param) /* if param is non-empty, it's supposed to be a filter */
goto out_reg;
if (!cmd_ops->set_filter)
goto out_reg;
ret = cmd_ops->set_filter(param, trigger_data, file);
if (ret < 0)
goto out_free;
out_reg:
ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
/*
* The above returns on success the # of functions enabled,
* but if it didn't find any functions it returns zero.
* Consider no functions a failure too.
*/
if (!ret) {
ret = -ENOENT;
goto out_free;
} else if (ret < 0)
goto out_free;
ret = 0;
out:
return ret;
out_free:
kfree(trigger_data);
goto out;
}
static void
traceon_trigger(struct event_trigger_data *data)
{
if (tracing_is_on())
return;
tracing_on();
}
static void
traceon_count_trigger(struct event_trigger_data *data)
{
if (!data->count)
return;
if (data->count != -1)
(data->count)--;
traceon_trigger(data);
}
static void
traceoff_trigger(struct event_trigger_data *data)
{
if (!tracing_is_on())
return;
tracing_off();
}
static void
traceoff_count_trigger(struct event_trigger_data *data)
{
if (!data->count)
return;
if (data->count != -1)
(data->count)--;
traceoff_trigger(data);
}
static int
traceon_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
struct event_trigger_data *data)
{
return event_trigger_print("traceon", m, (void *)data->count,
data->filter_str);
}
static int
traceoff_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
struct event_trigger_data *data)
{
return event_trigger_print("traceoff", m, (void *)data->count,
data->filter_str);
}
static struct event_trigger_ops traceon_trigger_ops = {
.func = traceon_trigger,
.print = traceon_trigger_print,
.init = event_trigger_init,
.free = event_trigger_free,
};
static struct event_trigger_ops traceon_count_trigger_ops = {
.func = traceon_count_trigger,
.print = traceon_trigger_print,
.init = event_trigger_init,
.free = event_trigger_free,
};
static struct event_trigger_ops traceoff_trigger_ops = {
.func = traceoff_trigger,
.print = traceoff_trigger_print,
.init = event_trigger_init,
.free = event_trigger_free,
};
static struct event_trigger_ops traceoff_count_trigger_ops = {
.func = traceoff_count_trigger,
.print = traceoff_trigger_print,
.init = event_trigger_init,
.free = event_trigger_free,
};
static struct event_trigger_ops *
onoff_get_trigger_ops(char *cmd, char *param)
{
struct event_trigger_ops *ops;
/* we register both traceon and traceoff to this callback */
if (strcmp(cmd, "traceon") == 0)
ops = param ? &traceon_count_trigger_ops :
&traceon_trigger_ops;
else
ops = param ? &traceoff_count_trigger_ops :
&traceoff_trigger_ops;
return ops;
}
static struct event_command trigger_traceon_cmd = {
.name = "traceon",
.trigger_type = ETT_TRACE_ONOFF,
.func = event_trigger_callback,
.reg = register_trigger,
.unreg = unregister_trigger,
.get_trigger_ops = onoff_get_trigger_ops,
};
static struct event_command trigger_traceoff_cmd = {
.name = "traceoff",
.trigger_type = ETT_TRACE_ONOFF,
.func = event_trigger_callback,
.reg = register_trigger,
.unreg = unregister_trigger,
.get_trigger_ops = onoff_get_trigger_ops,
};
static __init void unregister_trigger_traceon_traceoff_cmds(void)
{
unregister_event_command(&trigger_traceon_cmd);
unregister_event_command(&trigger_traceoff_cmd);
}
static __init int register_trigger_traceon_traceoff_cmds(void)
{
int ret;
ret = register_event_command(&trigger_traceon_cmd);
if (WARN_ON(ret < 0))
return ret;
ret = register_event_command(&trigger_traceoff_cmd);
if (WARN_ON(ret < 0))
unregister_trigger_traceon_traceoff_cmds();
return ret;
}
__init int register_trigger_cmds(void)
{
register_trigger_traceon_traceoff_cmds();
return 0;
}