bthread: implement basic Linux-like completion API

So far, completions made sense only in one direction: The main thread
can wait for pollers, but the other way around didn't work. With the new
bthread support, any bthread can wait for another to complete().
Wrap this up using the Linux completion API to make porting threaded
code easier.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20210622082617.18011-6-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 55 insertions, 0 deletions

diff --git a/include/linux/completion.h b/include/linux/completion.h
new file mode 100644
index 0000000000..e897e4f65b
--- /dev/null
+++ b/include/linux/completion.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * (C) Copyright 2021 Ahmad Fatoum
+ *
+ * Async wait-for-completion handler data structures.
+ * This allows one bthread to wait for another
+ */
+
+#ifndef __LINUX_COMPLETION_H
+#define __LINUX_COMPLETION_H
+
+#include <stdio.h>
+#include <errno.h>
+#include <bthread.h>
+
+struct completion {
+	unsigned int done;
+};
+
+static inline void init_completion(struct completion *x)
+{
+	x->done = 0;
+}
+
+static inline void reinit_completion(struct completion *x)
+{
+	x->done = 0;
+}
+
+static inline int wait_for_completion_interruptible(struct completion *x)
+{
+	while (!x->done) {
+		switch (bthread_should_stop()) {
+		case -EINTR:
+			if (!ctrlc())
+				continue;
+		case 1:
+			return -ERESTARTSYS;
+		}
+	}
+
+	return 0;
+}
+
+static inline bool completion_done(struct completion *x)
+{
+	return x->done;
+}
+
+static inline void complete(struct completion *x)
+{
+	x->done = 1;
+}
+
+#endif