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Subject[PATCH v2 25/40] tracing: Add support for dynamic tracepoints
Date
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' flag to struct tracepoint along with accompanying
logic for this purpose.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
include/linux/tracepoint-defs.h | 1 +
kernel/tracepoint.c | 18 +++++++++++++-----
2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index a031920..bc22d54 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -32,6 +32,7 @@ struct tracepoint {
int (*regfunc)(void);
void (*unregfunc)(void);
struct tracepoint_func __rcu *funcs;
+ bool dynamic;
};

#endif
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 685c50a..1c5957f 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -197,7 +197,9 @@ static int tracepoint_add_func(struct tracepoint *tp,
struct tracepoint_func *old, *tp_funcs;
int ret;

- if (tp->regfunc && !static_key_enabled(&tp->key)) {
+ if (tp->regfunc &&
+ ((tp->dynamic && !(atomic_read(&tp->key.enabled) > 0)) ||
+ !static_key_enabled(&tp->key))) {
ret = tp->regfunc();
if (ret < 0)
return ret;
@@ -219,7 +221,9 @@ static int tracepoint_add_func(struct tracepoint *tp,
* is used.
*/
rcu_assign_pointer(tp->funcs, tp_funcs);
- if (!static_key_enabled(&tp->key))
+ if (tp->dynamic && !(atomic_read(&tp->key.enabled) > 0))
+ atomic_inc(&tp->key.enabled);
+ else if (!tp->dynamic && !static_key_enabled(&tp->key))
static_key_slow_inc(&tp->key);
release_probes(old);
return 0;
@@ -246,10 +250,14 @@ 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 &&
+ ((tp->dynamic && (atomic_read(&tp->key.enabled) > 0)) ||
+ static_key_enabled(&tp->key)))
tp->unregfunc();

- if (static_key_enabled(&tp->key))
+ if (tp->dynamic && (atomic_read(&tp->key.enabled) > 0))
+ atomic_dec(&tp->key.enabled);
+ else if (!tp->dynamic && static_key_enabled(&tp->key))
static_key_slow_dec(&tp->key);
}
rcu_assign_pointer(tp->funcs, tp_funcs);
@@ -258,7 +266,7 @@ 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
--
1.9.3
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