From 1f23fe3fd82898469315b1b817099856051654a7 Mon Sep 17 00:00:00 2001
From: Shuo A Liu <shuo.a.liu@intel.com>
Date: Tue, 31 Dec 2019 12:55:01 +0800
Subject: [PATCH] hv: sched: simple event implemention

This simple event implemention can only support exclusive waiting
at same time. It mainly used by thread who want to wait for special event
happens.
  Thread A who want to wait for some events calls
	wait_event(struct sched_event *);

  Thread B who can give the event signal calls
	signal_event(struct sched_event *);

Tracked-On: #4329
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
---
 hypervisor/Makefile               |  1 +
 hypervisor/common/event.c         | 57 +++++++++++++++++++++++++++++++
 hypervisor/include/common/event.h | 16 +++++++++
 3 files changed, 74 insertions(+)
 create mode 100644 hypervisor/common/event.c
 create mode 100644 hypervisor/include/common/event.h

diff --git a/hypervisor/Makefile b/hypervisor/Makefile
index 4a6569d0b..e8694eefc 100644
--- a/hypervisor/Makefile
+++ b/hypervisor/Makefile
@@ -211,6 +211,7 @@ HW_C_SRCS += arch/x86/cat.c
 HW_C_SRCS += arch/x86/sgx.c
 HW_C_SRCS += common/softirq.c
 HW_C_SRCS += common/schedule.c
+HW_C_SRCS += common/event.c
 ifeq ($(CONFIG_SCHED_NOOP),y)
 HW_C_SRCS += common/sched_noop.c
 endif
diff --git a/hypervisor/common/event.c b/hypervisor/common/event.c
new file mode 100644
index 000000000..6c00ed83f
--- /dev/null
+++ b/hypervisor/common/event.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2018 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include <cpu.h>
+#include <schedule.h>
+#include <event.h>
+#include <logmsg.h>
+
+void init_event(struct sched_event *event)
+{
+	spinlock_init(&event->lock);
+	event->set = false;
+	event->waiting_thread = NULL;
+}
+
+void reset_event(struct sched_event *event)
+{
+	uint64_t rflag;
+
+	spinlock_irqsave_obtain(&event->lock, &rflag);
+	event->set = false;
+	event->waiting_thread = NULL;
+	spinlock_irqrestore_release(&event->lock, rflag);
+}
+
+/* support exclusive waiting only */
+void wait_event(struct sched_event *event)
+{
+	uint64_t rflag;
+
+	spinlock_irqsave_obtain(&event->lock, &rflag);
+	ASSERT((event->waiting_thread == NULL), "only support exclusive waiting");
+	while (!event->set) {
+		event->waiting_thread = sched_get_current(get_pcpu_id());
+		sleep_thread(event->waiting_thread);
+		spinlock_irqrestore_release(&event->lock, rflag);
+		schedule();
+		spinlock_irqsave_obtain(&event->lock, &rflag);
+	}
+	event->set = false;
+	event->waiting_thread = NULL;
+	spinlock_irqrestore_release(&event->lock, rflag);
+}
+
+void signal_event(struct sched_event *event)
+{
+	uint64_t rflag;
+
+	spinlock_irqsave_obtain(&event->lock, &rflag);
+	event->set = true;
+	if (event->waiting_thread != NULL) {
+		wake_thread(event->waiting_thread);
+	}
+	spinlock_irqrestore_release(&event->lock, rflag);
+}
diff --git a/hypervisor/include/common/event.h b/hypervisor/include/common/event.h
new file mode 100644
index 000000000..c7f398032
--- /dev/null
+++ b/hypervisor/include/common/event.h
@@ -0,0 +1,16 @@
+#ifndef EVENT_H
+#define EVENT_H
+#include <spinlock.h>
+
+struct sched_event {
+	spinlock_t lock;
+	bool set;
+	struct thread_object* waiting_thread;
+};
+
+void init_event(struct sched_event *event);
+void reset_event(struct sched_event *event);
+void wait_event(struct sched_event *event);
+void signal_event(struct sched_event *event);
+
+#endif /* EVENT_H */