[PATCH 15/15] tracepoints: Use static_call

From: Peter Zijlstra
Date: Wed Jun 05 2019 - 09:27:42 EST

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From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

... Changelog goes here ...

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
include/linux/tracepoint-defs.h | 4 ++
include/linux/tracepoint.h | 73 ++++++++++++++++++++++++++--------------
include/trace/define_trace.h | 14 +++----
kernel/tracepoint.c | 25 +++++++++++--
4 files changed, 80 insertions(+), 36 deletions(-)

--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -11,6 +11,8 @@
#include <linux/atomic.h>
#include <linux/static_key.h>

+struct static_call_key;
+
struct trace_print_flags {
unsigned long mask;
const char *name;
@@ -30,6 +32,8 @@ struct tracepoint_func {
struct tracepoint {
const char *name; /* Tracepoint name */
struct static_key key;
+ struct static_call_key *static_call_key;
+ void *iterator;
int (*regfunc)(void);
void (*unregfunc)(void);
struct tracepoint_func __rcu *funcs;
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -21,6 +21,7 @@
#include <linux/cpumask.h>
#include <linux/rcupdate.h>
#include <linux/tracepoint-defs.h>
+#include <linux/static_call.h>

struct module;
struct tracepoint;
@@ -94,7 +95,9 @@ extern int syscall_regfunc(void);
extern void syscall_unregfunc(void);
#endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */

+#ifndef PARAMS
#define PARAMS(args...) args
+#endif

#define TRACE_DEFINE_ENUM(x)
#define TRACE_DEFINE_SIZEOF(x)
@@ -161,12 +164,11 @@ static inline struct tracepoint *tracepo
* as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
* "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
*/
-#define __DO_TRACE(tp, proto, args, cond, rcuidle) \
+#define __DO_TRACE(name, proto, args, cond, rcuidle) \
do { \
struct tracepoint_func *it_func_ptr; \
- void *it_func; \
- void *__data; \
int __maybe_unused __idx = 0; \
+ void *__data; \
\
if (!(cond)) \
return; \
@@ -186,14 +188,11 @@ static inline struct tracepoint *tracepo
rcu_irq_enter_irqson(); \
} \
\
- it_func_ptr = rcu_dereference_raw((tp)->funcs); \
- \
+ it_func_ptr = \
+ rcu_dereference_raw((&__tracepoint_##name)->funcs); \
if (it_func_ptr) { \
- do { \
- it_func = (it_func_ptr)->func; \
- __data = (it_func_ptr)->data; \
- ((void(*)(proto))(it_func))(args); \
- } while ((++it_func_ptr)->func); \
+ __data = (it_func_ptr)->data; \
+ static_call(tp_func_##name, args); \
} \
\
if (rcuidle) { \
@@ -209,7 +208,7 @@ static inline struct tracepoint *tracepo
static inline void trace_##name##_rcuidle(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
- __DO_TRACE(&__tracepoint_##name, \
+ __DO_TRACE(name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), 1); \
@@ -231,11 +230,13 @@ static inline struct tracepoint *tracepo
* poking RCU a bit.
*/
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
+ extern int __tracepoint_iter_##name(data_proto); \
+ DECLARE_STATIC_CALL(tp_func_##name, __tracepoint_iter_##name); \
extern struct tracepoint __tracepoint_##name; \
static inline void trace_##name(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
- __DO_TRACE(&__tracepoint_##name, \
+ __DO_TRACE(name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), 0); \
@@ -281,21 +282,43 @@ static inline struct tracepoint *tracepo
* structures, so we create an array of pointers that will be used for iteration
* on the tracepoints.
*/
-#define DEFINE_TRACE_FN(name, reg, unreg) \
- static const char __tpstrtab_##name[] \
- __attribute__((section("__tracepoints_strings"))) = #name; \
- struct tracepoint __tracepoint_##name \
- __attribute__((section("__tracepoints"), used)) = \
- { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
- __TRACEPOINT_ENTRY(name);
+#define DEFINE_TRACE_FN(name, reg, unreg, proto, args) \
+ static const char __tpstrtab_##name[] \
+ __attribute__((section("__tracepoints_strings"))) = #name; \
+ extern struct static_call_key tp_func_##name; \
+ int __tracepoint_iter_##name(void *__data, proto); \
+ struct tracepoint __tracepoint_##name \
+ __attribute__((section("__tracepoints"), used)) = \
+ { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, \
+ &tp_func_##name, __tracepoint_iter_##name, \
+ reg, unreg, NULL }; \
+ __TRACEPOINT_ENTRY(name); \
+ int __tracepoint_iter_##name(void *__data, proto) \
+ { \
+ struct tracepoint_func *it_func_ptr; \
+ void *it_func; \
+ \
+ it_func_ptr = \
+ rcu_dereference_raw((&__tracepoint_##name)->funcs); \
+ do { \
+ it_func = (it_func_ptr)->func; \
+ __data = (it_func_ptr)->data; \
+ ((void(*)(void *, proto))(it_func))(__data, args); \
+ } while ((++it_func_ptr)->func); \
+ return 0; \
+ } \
+ DEFINE_STATIC_CALL(tp_func_##name, __tracepoint_iter_##name);

-#define DEFINE_TRACE(name) \
- DEFINE_TRACE_FN(name, NULL, NULL);
+#define DEFINE_TRACE(name, proto, args) \
+ DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));

#define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
- EXPORT_SYMBOL_GPL(__tracepoint_##name)
+ EXPORT_SYMBOL_GPL(__tracepoint_##name); \
+ EXPORT_STATIC_CALL_GPL(tp_func_##name)
#define EXPORT_TRACEPOINT_SYMBOL(name) \
- EXPORT_SYMBOL(__tracepoint_##name)
+ EXPORT_SYMBOL(__tracepoint_##name); \
+ EXPORT_STATIC_CALL(tp_func_##name)
+

#else /* !TRACEPOINTS_ENABLED */
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
@@ -324,8 +347,8 @@ static inline struct tracepoint *tracepo
return false; \
}

-#define DEFINE_TRACE_FN(name, reg, unreg)
-#define DEFINE_TRACE(name)
+#define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
+#define DEFINE_TRACE(name, proto, args)
#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
#define EXPORT_TRACEPOINT_SYMBOL(name)

--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -25,7 +25,7 @@

#undef TRACE_EVENT
#define TRACE_EVENT(name, proto, args, tstruct, assign, print) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef TRACE_EVENT_CONDITION
#define TRACE_EVENT_CONDITION(name, proto, args, cond, tstruct, assign, print) \
@@ -39,12 +39,12 @@
#undef TRACE_EVENT_FN
#define TRACE_EVENT_FN(name, proto, args, tstruct, \
assign, print, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg)
+ DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef TRACE_EVENT_FN_COND
#define TRACE_EVENT_FN_COND(name, proto, args, cond, tstruct, \
assign, print, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg)
+ DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef TRACE_EVENT_NOP
#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)
@@ -54,15 +54,15 @@

#undef DEFINE_EVENT
#define DEFINE_EVENT(template, name, proto, args) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT_FN
#define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg)
+ DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT_PRINT
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef DEFINE_EVENT_CONDITION
#define DEFINE_EVENT_CONDITION(template, name, proto, args, cond) \
@@ -70,7 +70,7 @@

#undef DECLARE_TRACE
#define DECLARE_TRACE(name, proto, args) \
- DEFINE_TRACE(name)
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))

#undef TRACE_INCLUDE
#undef __TRACE_INCLUDE
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -127,7 +127,7 @@ static void debug_print_probes(struct tr

static struct tracepoint_func *
func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
- int prio)
+ int prio, int *tot_probes)
{
struct tracepoint_func *old, *new;
int nr_probes = 0;
@@ -170,11 +170,12 @@ func_add(struct tracepoint_func **funcs,
new[nr_probes + 1].func = NULL;
*funcs = new;
debug_print_probes(*funcs);
+ *tot_probes = nr_probes + 1;
return old;
}

static void *func_remove(struct tracepoint_func **funcs,
- struct tracepoint_func *tp_func)
+ struct tracepoint_func *tp_func, int *left)
{
int nr_probes = 0, nr_del = 0, i;
struct tracepoint_func *old, *new;
@@ -228,6 +229,7 @@ static int tracepoint_add_func(struct tr
struct tracepoint_func *func, int prio)
{
struct tracepoint_func *old, *tp_funcs;
+ int probes = 0;
int ret;

if (tp->regfunc && !static_key_enabled(&tp->key)) {
@@ -238,7 +240,7 @@ static int tracepoint_add_func(struct tr

tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
- old = func_add(&tp_funcs, func, prio);
+ old = func_add(&tp_funcs, func, prio, &probes);
if (IS_ERR(old)) {
WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
return PTR_ERR(old);
@@ -253,6 +255,13 @@ static int tracepoint_add_func(struct tr
rcu_assign_pointer(tp->funcs, tp_funcs);
if (!static_key_enabled(&tp->key))
static_key_slow_inc(&tp->key);
+
+ if (probes == 1) {
+ __static_call_update(tp->static_call_key, tp_funcs->func);
+ } else {
+ __static_call_update(tp->static_call_key, tp->iterator);
+ }
+
release_probes(old);
return 0;
}
@@ -267,10 +276,11 @@ static int tracepoint_remove_func(struct
struct tracepoint_func *func)
{
struct tracepoint_func *old, *tp_funcs;
+ int probes_left = 0;

tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
- old = func_remove(&tp_funcs, func);
+ old = func_remove(&tp_funcs, func, &probes_left);
if (IS_ERR(old)) {
WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
return PTR_ERR(old);
@@ -284,6 +294,13 @@ static int tracepoint_remove_func(struct
if (static_key_enabled(&tp->key))
static_key_slow_dec(&tp->key);
}
+
+ if (probes_left == 1) {
+ __static_call_update(tp->static_call_key, tp_funcs->func);
+ } else {
+ __static_call_update(tp->static_call_key, tp->iterator);
+ }
+
rcu_assign_pointer(tp->funcs, tp_funcs);
release_probes(old);
return 0;

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