[PATCH 20/32] tracing: Add support for dynamic tracepoints

Tom Zanussi
2017-06-26T22:54:48Z

The tracepoint infrastructure assumes statically-defined tracepoints
and uses static_keys for tracepoint enablement. In order to define
tracepoints on the fly, we need to have a dynamic counterpart.

Add a dynamic_tracepoint_probe_register() and a dynamic param onto
tracepoint_probe_unregister() for this purpose.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
include/linux/tracepoint.h | 11 +++++++----
kernel/trace/trace_events.c | 4 ++--
kernel/tracepoint.c | 42 ++++++++++++++++++++++++++++++------------
3 files changed, 39 insertions(+), 18 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a26ffbe..dfb07dd 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -37,9 +37,12 @@ struct trace_eval_map {
tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
extern int
tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
- int prio);
+ int prio, bool dynamic);
+extern int dynamic_tracepoint_probe_register(struct tracepoint *tp,
+ void *probe, void *data);
extern int
-tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
+tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data,
+ bool dynamic);
extern void
for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
void *priv);
@@ -210,13 +213,13 @@ static inline void tracepoint_synchronize_unregister(void)
int prio) \
{ \
return tracepoint_probe_register_prio(&__tracepoint_##name, \
- (void *)probe, data, prio); \
+ (void *)probe, data, prio, false); \
} \
static inline int \
unregister_trace_##name(void (*probe)(data_proto), void *data) \
{ \
return tracepoint_probe_unregister(&__tracepoint_##name,\
- (void *)probe, data); \
+ (void *)probe, data, false); \
} \
static inline void \
check_trace_callback_type_##name(void (*cb)(data_proto)) \
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 83dfd0d..1324393 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -297,7 +297,7 @@ int trace_event_reg(struct trace_event_call *call,
case TRACE_REG_UNREGISTER:
tracepoint_probe_unregister(call->tp,
call->class->probe,
- file);
+ file, false);
return 0;

#ifdef CONFIG_PERF_EVENTS
@@ -308,7 +308,7 @@ int trace_event_reg(struct trace_event_call *call,
case TRACE_REG_PERF_UNREGISTER:
tracepoint_probe_unregister(call->tp,
call->class->perf_probe,
- call);
+ call, false);
return 0;
case TRACE_REG_PERF_OPEN:
case TRACE_REG_PERF_CLOSE:
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 685c50a..4068809 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -192,12 +192,15 @@ static void *func_remove(struct tracepoint_func **funcs,
* Add the probe function to a tracepoint.
*/
static int tracepoint_add_func(struct tracepoint *tp,
- struct tracepoint_func *func, int prio)
+ struct tracepoint_func *func, int prio,
+ bool dynamic)
{
struct tracepoint_func *old, *tp_funcs;
int ret;

- if (tp->regfunc && !static_key_enabled(&tp->key)) {
+ if (tp->regfunc &&
+ ((dynamic && !(atomic_read(&tp->key.enabled) > 0)) ||
+ !static_key_enabled(&tp->key))) {
ret = tp->regfunc();
if (ret < 0)
return ret;
@@ -219,7 +222,9 @@ static int tracepoint_add_func(struct tracepoint *tp,
* is used.
*/
rcu_assign_pointer(tp->funcs, tp_funcs);
- if (!static_key_enabled(&tp->key))
+ if (dynamic && !(atomic_read(&tp->key.enabled) > 0))
+ atomic_inc(&tp->key.enabled);
+ else if (!dynamic && !static_key_enabled(&tp->key))
static_key_slow_inc(&tp->key);
release_probes(old);
return 0;
@@ -232,7 +237,7 @@ static int tracepoint_add_func(struct tracepoint *tp,
* by preempt_disable around the call site.
*/
static int tracepoint_remove_func(struct tracepoint *tp,
- struct tracepoint_func *func)
+ struct tracepoint_func *func, bool dynamic)
{
struct tracepoint_func *old, *tp_funcs;

@@ -246,10 +251,14 @@ static int tracepoint_remove_func(struct tracepoint *tp,

if (!tp_funcs) {
/* Removed last function */
- if (tp->unregfunc && static_key_enabled(&tp->key))
+ if (tp->unregfunc &&
+ ((dynamic && (atomic_read(&tp->key.enabled) > 0)) ||
+ static_key_enabled(&tp->key)))
tp->unregfunc();

- if (static_key_enabled(&tp->key))
+ if (dynamic && (atomic_read(&tp->key.enabled) > 0))
+ atomic_dec(&tp->key.enabled);
+ else if (!dynamic && static_key_enabled(&tp->key))
static_key_slow_dec(&tp->key);
}
rcu_assign_pointer(tp->funcs, tp_funcs);
@@ -258,7 +267,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
}

/**
- * tracepoint_probe_register - Connect a probe to a tracepoint
+ * tracepoint_probe_register_prio - Connect a probe to a tracepoint
* @tp: tracepoint
* @probe: probe handler
* @data: tracepoint data
@@ -271,7 +280,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
* within module exit functions.
*/
int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
- void *data, int prio)
+ void *data, int prio, bool dynamic)
{
struct tracepoint_func tp_func;
int ret;
@@ -280,7 +289,7 @@ int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
tp_func.func = probe;
tp_func.data = data;
tp_func.prio = prio;
- ret = tracepoint_add_func(tp, &tp_func, prio);
+ ret = tracepoint_add_func(tp, &tp_func, prio, dynamic);
mutex_unlock(&tracepoints_mutex);
return ret;
}
@@ -301,10 +310,18 @@ int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
*/
int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
{
- return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
+ return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO, false);
}
EXPORT_SYMBOL_GPL(tracepoint_probe_register);

+int dynamic_tracepoint_probe_register(struct tracepoint *tp, void *probe,
+ void *data)
+{
+ return tracepoint_probe_register_prio(tp, probe, data,
+ TRACEPOINT_DEFAULT_PRIO, true);
+}
+EXPORT_SYMBOL_GPL(dynamic_tracepoint_probe_register);
+
/**
* tracepoint_probe_unregister - Disconnect a probe from a tracepoint
* @tp: tracepoint
@@ -313,7 +330,8 @@ int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
*
* Returns 0 if ok, error value on error.
*/
-int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
+int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data,
+ bool dynamic)
{
struct tracepoint_func tp_func;
int ret;
@@ -321,7 +339,7 @@ int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
mutex_lock(&tracepoints_mutex);
tp_func.func = probe;
tp_func.data = data;
- ret = tracepoint_remove_func(tp, &tp_func);
+ ret = tracepoint_remove_func(tp, &tp_func, dynamic);
mutex_unlock(&tracepoints_mutex);
return ret;
}
--
1.9.3