[for-next][PATCH 08/11] tracing: Introduce tracepoint_is_faultable()

Steven Rostedt
2024-11-01T10:36:10Z

From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Introduce a "faultable" flag within the extended structure to know
whether a tracepoint needs rcu tasks trace grace period before reclaim.
This can be queried using tracepoint_is_faultable().

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Jordan Rife <jrife@google.com>
Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jordan Rife <jrife@google.com>
Cc: linux-trace-kernel@vger.kernel.org
Link: https://lore.kernel.org/20241031152056.744137-3-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
include/linux/tracepoint-defs.h | 2 ++
include/linux/tracepoint.h | 24 ++++++++++++++++++++++++
include/trace/define_trace.h | 2 +-
3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 967c08d9da84..aebf0571c736 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -32,6 +32,8 @@ struct tracepoint_func {
struct tracepoint_ext {
int (*regfunc)(void);
void (*unregfunc)(void);
+ /* Flags. */
+ unsigned int faultable:1;
};

struct tracepoint {
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 862ab49177a4..906f3091d23d 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -104,6 +104,12 @@ void for_each_tracepoint_in_module(struct module *mod,
* tracepoint_synchronize_unregister must be called between the last tracepoint
* probe unregistration and the end of module exit to make sure there is no
* caller executing a probe when it is freed.
+ *
+ * An alternative is to use the following for batch reclaim associated
+ * with a given tracepoint:
+ *
+ * - tracepoint_is_faultable() == false: call_rcu()
+ * - tracepoint_is_faultable() == true: call_rcu_tasks_trace()
*/
#ifdef CONFIG_TRACEPOINTS
static inline void tracepoint_synchronize_unregister(void)
@@ -111,9 +117,17 @@ static inline void tracepoint_synchronize_unregister(void)
synchronize_rcu_tasks_trace();
synchronize_rcu();
}
+static inline bool tracepoint_is_faultable(struct tracepoint *tp)
+{
+ return tp->ext && tp->ext->faultable;
+}
#else
static inline void tracepoint_synchronize_unregister(void)
{ }
+static inline bool tracepoint_is_faultable(struct tracepoint *tp)
+{
+ return false;
+}
#endif

#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
@@ -345,6 +359,15 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
static struct tracepoint_ext __tracepoint_ext_##_name = { \
.regfunc = _reg, \
.unregfunc = _unreg, \
+ .faultable = false, \
+ }; \
+ __DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
+
+#define DEFINE_TRACE_SYSCALL(_name, _reg, _unreg, _proto, _args) \
+ static struct tracepoint_ext __tracepoint_ext_##_name = { \
+ .regfunc = _reg, \
+ .unregfunc = _unreg, \
+ .faultable = true, \
}; \
__DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));

@@ -389,6 +412,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#define __DECLARE_TRACE_SYSCALL __DECLARE_TRACE

#define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
+#define DEFINE_TRACE_SYSCALL(name, reg, unreg, proto, args)
#define DEFINE_TRACE(name, proto, args)
#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
#define EXPORT_TRACEPOINT_SYMBOL(name)
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index ff5fa17a6259..63fea2218afa 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -48,7 +48,7 @@

#undef TRACE_EVENT_SYSCALL
#define TRACE_EVENT_SYSCALL(name, proto, args, struct, assign, print, reg, unreg) \
- DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))
+ DEFINE_TRACE_SYSCALL(name, reg, unreg, PARAMS(proto), PARAMS(args))

#undef TRACE_EVENT_NOP
#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)
--
2.45.2