From 024d772be8df74546add085b70ac04676401c6d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Sat, 27 Jan 2018 22:06:36 +0100
Subject: [PATCH] Queues using some macro magic

---
 src/kernel/include/queue.h     | 39 ++++++++++++++++++++++++++++++++++
 src/kernel/include/scheduler.h |  5 +++++
 src/kernel/include/thread.h    |  5 +++--
 src/kernel/proc/scheduler.c    | 21 ++++++------------
 4 files changed, 53 insertions(+), 17 deletions(-)
 create mode 100644 src/kernel/include/queue.h

diff --git a/src/kernel/include/queue.h b/src/kernel/include/queue.h
new file mode 100644
index 0000000..bd48111
--- /dev/null
+++ b/src/kernel/include/queue.h
@@ -0,0 +1,39 @@
+#pragma once
+
+#define _QUEUE_DECL(queue, entry, type) \
+  struct queue{ \
+    type *first; \
+    type *last; \
+  }
+#define QUEUE_DECL(...) _QUEUE_DECL(__VA_ARGS__)
+#define _QUEUE_HEAD(queue, entry, type) \
+  struct queue queue
+#define QUEUE_HEAD(...) _QUEUE_HEAD(__VA_ARGS__)
+#define QUEUE_HEAD_EMPTY(...) _QUEUE_HEAD(__VA_ARGS__) = {0,0}
+
+#define _QUEUE_SPOT(queue, entry, type) \
+  type *entry
+#define QUEUE_SPOT(...) _QUEUE_SPOT(__VA_ARGS__)
+
+#define _QUEUE_EMPTY(queue, entry, type) \
+  (!(queue.last))
+#define QUEUE_EMPTY(...) _QUEUE_EMPTY(__VA_ARGS__)
+#define QUEUE_NOT_EMPTY(...) (!(_QUEUE_EMPTY(__VA_ARGS__)))
+
+#define _QUEUE_ADD(queue, entry, type, item) \
+  if(!queue.last) \
+    queue.first = item; \
+  else \
+    queue.last->entry = item; \
+  queue.last = item; \
+  item->entry = 0;
+#define QUEUE_ADD(...) _QUEUE_ADD(__VA_ARGS__)
+
+#define _QUEUE_DROP(queue, entry, type) \
+    if(!(queue.first = queue.first->entry)) \
+      queue.last = 0;
+#define QUEUE_DROP(...) _QUEUE_DROP(__VA_ARGS__)
+
+#define _QUEUE_PEEK(queue, entry, type) \
+    (queue.first)
+#define QUEUE_PEEK(...) _QUEUE_PEEK(__VA_ARGS__)
diff --git a/src/kernel/include/scheduler.h b/src/kernel/include/scheduler.h
index 6566cd7..888fecb 100644
--- a/src/kernel/include/scheduler.h
+++ b/src/kernel/include/scheduler.h
@@ -1,4 +1,9 @@
 #pragma once
+#include <queue.h>
+
+#define READYQ readyQ, readyQ_next, struct thread
+QUEUE_DECL(READYQ);
+QUEUE_HEAD(READYQ);
 
 void ready(struct thread *th);
 struct thread *scheduler_next();
diff --git a/src/kernel/include/thread.h b/src/kernel/include/thread.h
index d09bed5..bc36d42 100644
--- a/src/kernel/include/thread.h
+++ b/src/kernel/include/thread.h
@@ -1,13 +1,14 @@
 #pragma once
+#include <queue.h>
+#include <scheduler.h>
 #include <memory.h>
 
-
 struct thread
 {
   uintptr_t stack_ptr;
   uint64_t tid;
   uint64_t state;
-  struct thread *next;
+  QUEUE_SPOT(READYQ);
 };
 
 #define TCB_OFFSET (PAGE_SIZE - sizeof(struct thread))
diff --git a/src/kernel/proc/scheduler.c b/src/kernel/proc/scheduler.c
index c94f454..f4e1395 100644
--- a/src/kernel/proc/scheduler.c
+++ b/src/kernel/proc/scheduler.c
@@ -1,26 +1,17 @@
+#include <scheduler.h>
+#include <queue.h>
 #include <thread.h>
 
-struct {
-  struct thread *first;
-  struct thread *last;
-} readyQ = {0,0};
+QUEUE_HEAD_EMPTY(READYQ);
 
 void ready(struct thread *th)
 {
-  if(!readyQ.last)
-  {
-    th->next = 0;
-    readyQ.first = readyQ.last = th;
-  } else {
-    readyQ.last->next = th;
-    readyQ.last = th;
-  }
+  QUEUE_ADD(READYQ, th);
 }
 
 struct thread *scheduler_next()
 {
-  struct thread *th = readyQ.first;
-  if(!(readyQ.first = th->next))
-    readyQ.last = 0;
+  struct thread *th = QUEUE_PEEK(READYQ);
+  QUEUE_DROP(READYQ);
   return th;
 }