v4.19.13 snapshot.
diff --git a/tools/perf/util/trigger.h b/tools/perf/util/trigger.h
new file mode 100644
index 0000000..88223bc
--- /dev/null
+++ b/tools/perf/util/trigger.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#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 --(hit)--> HIT
+ * ^ |
+ * | (ready)
+ * | |
+ * \_____________/
+ *
+ * is_hit and is_ready are two key functions to query the state of
+ * a trigger. is_hit 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_ON = 0,
+ TRIGGER_READY = 1,
+ TRIGGER_HIT = 2,
+ } 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_ON;
+}
+
+static inline void trigger_ready(struct trigger *t)
+{
+ if (!trigger_is_available(t))
+ return;
+ t->state = TRIGGER_READY;
+}
+
+static inline void trigger_hit(struct trigger *t)
+{
+ if (!trigger_is_available(t))
+ return;
+ TRIGGER_WARN_ONCE(t, TRIGGER_READY);
+ t->state = TRIGGER_HIT;
+}
+
+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_hit(struct trigger *t)
+{
+ return t->state == TRIGGER_HIT;
+}
+
+#define DEFINE_TRIGGER(n) \
+struct trigger n = {.state = TRIGGER_OFF, .name = #n}
+#endif