[v5,1/6] perf tools: Derive trigger class from auxtrace_snapshot

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 5b4758a..ad37f69 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -34,6 +34,7 @@ 
 #include "util/parse-regs-options.h"
 #include "util/llvm-utils.h"
 #include "util/bpf-loader.h"
+#include "util/trigger.h"
 #include "asm/bug.h"
 
 #include <unistd.h>
@@ -127,44 +128,8 @@  static volatile int done;
 static volatile int signr = -1;
 static volatile int child_finished;
 
-static volatile enum {
-	AUXTRACE_SNAPSHOT_OFF = -1,
-	AUXTRACE_SNAPSHOT_DISABLED = 0,
-	AUXTRACE_SNAPSHOT_ENABLED = 1,
-} auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_OFF;
-
-static inline void
-auxtrace_snapshot_on(void)
-{
-	auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_DISABLED;
-}
-
-static inline void
-auxtrace_snapshot_enable(void)
-{
-	if (auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_OFF)
-		return;
-	auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_ENABLED;
-}
-
-static inline void
-auxtrace_snapshot_disable(void)
-{
-	if (auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_OFF)
-		return;
-	auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_DISABLED;
-}
-
-static inline bool
-auxtrace_snapshot_is_enabled(void)
-{
-	if (auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_OFF)
-		return false;
-	return auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_ENABLED;
-}
-
-static volatile int auxtrace_snapshot_err;
 static volatile int auxtrace_record__snapshot_started;
+static DEFINE_TRIGGER(auxtrace_snapshot);
 
 static void sig_handler(int sig)
 {
@@ -282,11 +247,12 @@  static void record__read_auxtrace_snapshot(struct record *rec)
 {
 	pr_debug("Recording AUX area tracing snapshot\n");
 	if (record__auxtrace_read_snapshot_all(rec) < 0) {
-		auxtrace_snapshot_err = -1;
+		auxtrace_snapshot_error();
 	} else {
-		auxtrace_snapshot_err = auxtrace_record__snapshot_finish(rec->itr);
-		if (!auxtrace_snapshot_err)
-			auxtrace_snapshot_enable();
+		if (auxtrace_record__snapshot_finish(rec->itr))
+			auxtrace_snapshot_error();
+		else
+			auxtrace_snapshot_ready();
 	}
 }
 
@@ -815,21 +781,21 @@  static int __cmd_record(struct record *rec, int argc, const char **argv)
 		perf_evlist__enable(rec->evlist);
 	}
 
-	auxtrace_snapshot_enable();
+	auxtrace_snapshot_ready();
 	for (;;) {
 		unsigned long long hits = rec->samples;
 
 		if (record__mmap_read_all(rec) < 0) {
-			auxtrace_snapshot_disable();
+			auxtrace_snapshot_error();
 			err = -1;
 			goto out_child;
 		}
 
 		if (auxtrace_record__snapshot_started) {
 			auxtrace_record__snapshot_started = 0;
-			if (!auxtrace_snapshot_err)
+			if (!auxtrace_snapshot_is_error())
 				record__read_auxtrace_snapshot(rec);
-			if (auxtrace_snapshot_err) {
+			if (auxtrace_snapshot_is_error()) {
 				pr_err("AUX area tracing snapshot failed\n");
 				err = -1;
 				goto out_child;
@@ -858,12 +824,12 @@  static int __cmd_record(struct record *rec, int argc, const char **argv)
 		 * disable events in this case.
 		 */
 		if (done && !disabled && !target__none(&opts->target)) {
-			auxtrace_snapshot_disable();
+			auxtrace_snapshot_off();
 			perf_evlist__disable(rec->evlist);
 			disabled = true;
 		}
 	}
-	auxtrace_snapshot_disable();
+	auxtrace_snapshot_off();
 
 	if (forks && workload_exec_errno) {
 		char msg[STRERR_BUFSIZE];
@@ -1447,9 +1413,10 @@  out_symbol_exit:
 
 static void snapshot_sig_handler(int sig __maybe_unused)
 {
-	if (!auxtrace_snapshot_is_enabled())
+	if (!auxtrace_snapshot_is_ready())
 		return;
-	auxtrace_snapshot_disable();
-	auxtrace_snapshot_err = auxtrace_record__snapshot_start(record.itr);
+	auxtrace_snapshot_toggle();
 	auxtrace_record__snapshot_started = 1;
+	if (auxtrace_record__snapshot_start(record.itr))
+		auxtrace_snapshot_error();
 }
diff --git a/tools/perf/util/trigger.h b/tools/perf/util/trigger.h
new file mode 100644
index 0000000..89a30e9
--- /dev/null
+++ b/tools/perf/util/trigger.h
@@ -0,0 +1,109 @@ 
+#ifndef __TRIGGER_H_
+#define __TRIGGER_H_ 1
+
+#include "util/debug.h"
+#include "asm/bug.h"
+
+/*
+ * Use trigger to model operations which need to be executed when
+ * an event (a signal, for example) is observed.
+ *
+ * States and transits:
+ *
+ *
+ *  OFF--(on)--> READY --(toggle)--> TOGGLED
+ *                 ^                    |   
+ *                 |                 (ready)
+ *                 |                    |   
+ *                  \__________________/
+ *
+ * is_toggled and is_ready are two key functions to query the state of
+ * a trigger. is_toggled means the event already happen; is_ready means the
+ * trigger is waiting for the event.
+ */
+
+struct trigger {
+	volatile enum {
+		TRIGGER_ERROR		= -2,
+		TRIGGER_OFF		= -1,
+		TRIGGER_READY		= 0,
+		TRIGGER_TOGGLED		= 1,
+	} state;
+	const char *name;
+};
+
+#define TRIGGER_WARN_ONCE(t, exp) \
+	WARN_ONCE(t->state != exp, "trigger '%s' state transist error: %d in %s()\n", \
+		  t->name, t->state, __func__)
+
+static inline bool trigger_is_available(struct trigger *t)
+{
+	return t->state >= 0;
+}
+
+static inline bool trigger_is_error(struct trigger *t)
+{
+	return t->state <= TRIGGER_ERROR;
+}
+
+static inline void trigger_on(struct trigger *t)
+{
+	TRIGGER_WARN_ONCE(t, TRIGGER_OFF);
+	t->state = TRIGGER_READY;
+}
+
+static inline void trigger_ready(struct trigger *t)
+{
+	if (!trigger_is_available(t))
+		return;
+	t->state = TRIGGER_READY;
+}
+
+static inline void trigger_toggle(struct trigger *t)
+{
+	if (!trigger_is_available(t))
+		return;
+	TRIGGER_WARN_ONCE(t, TRIGGER_READY);
+	t->state = TRIGGER_TOGGLED;
+}
+
+static inline void trigger_off(struct trigger *t)
+{
+	if (!trigger_is_available(t))
+		return;
+	t->state = TRIGGER_OFF;
+}
+
+static inline void trigger_error(struct trigger *t)
+{
+	t->state = TRIGGER_ERROR;
+}
+
+static inline bool trigger_is_ready(struct trigger *t)
+{
+	return t->state == TRIGGER_READY;
+}
+
+static inline bool trigger_is_toggled(struct trigger *t)
+{
+	return t->state == TRIGGER_TOGGLED;
+}
+
+#define __TRIGGER_VAR(n) n##_state
+#define __DEF_TRIGGER_VOID_FUNC(n, op)	\
+static inline void n##_##op(void) {trigger_##op(&__TRIGGER_VAR(n)); }
+#define __DEF_TRIGGER_BOOL_FUNC(n, op)	\
+static inline bool n##_##op(void) {return trigger_##op(&__TRIGGER_VAR(n)); }
+
+#define DEFINE_TRIGGER(n)					\
+struct trigger n##_state = {.state = TRIGGER_OFF, .name = #n};	\
+__DEF_TRIGGER_VOID_FUNC(n, on)					\
+__DEF_TRIGGER_VOID_FUNC(n, ready)				\
+__DEF_TRIGGER_VOID_FUNC(n, toggle)				\
+__DEF_TRIGGER_VOID_FUNC(n, off)					\
+__DEF_TRIGGER_VOID_FUNC(n, error)				\
+__DEF_TRIGGER_BOOL_FUNC(n, is_ready)				\
+__DEF_TRIGGER_BOOL_FUNC(n, is_toggled)				\
+__DEF_TRIGGER_BOOL_FUNC(n, is_error)
+
+#endif