From 8b36a39774789cee66d84db9f0086af15cacc211 Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Fri, 26 Aug 2022 22:31:52 -0700
Subject: No used mutex queue

---
 kernel/sys/schedule.c |  2 ++
 kernel/util/mutex.c   | 68 ++++++++++++++-------------------------------------
 2 files changed, 20 insertions(+), 50 deletions(-)

(limited to 'kernel')

diff --git a/kernel/sys/schedule.c b/kernel/sys/schedule.c
index 3157c5d..142ffaf 100644
--- a/kernel/sys/schedule.c
+++ b/kernel/sys/schedule.c
@@ -21,6 +21,7 @@ void init_scheduler(void)
 	usrloopthread.old_priority = -1;
 	usrloopthread.status = THREAD_READY;
 	usrloopthread.offset = -1;
+	usrloopthread.highest_mutex = 0;
 	scheduler.rthread = &usrloopthread;
 
 	// Initialize Scheduling Queues
@@ -56,6 +57,7 @@ void init_scheduler(void)
 		struct Thread* t = &threads[i];
 		t->offset = i;
 		t->sp_base = 0x20000000 - STACK_SIZE*i;
+		t->highest_mutex = 0;
 		thread_entries[i].value = t;
 		thread_entries[i].next = &thread_entries[(i+1)];
 		thread_entries[i].entry_type = VALUE_ENTRY;
diff --git a/kernel/util/mutex.c b/kernel/util/mutex.c
index 8e85f8f..997d85d 100644
--- a/kernel/util/mutex.c
+++ b/kernel/util/mutex.c
@@ -21,13 +21,6 @@ void mutex_init(void)
 	mutex_manager.free.end.next = &mutex_entries[MAX_MUTEXS-1];
 	mutex_entries[MAX_MUTEXS-1].next = &mutex_manager.free.end;
 	mutex_manager.free.end.entry_type = END_ENTRY;
-	// Initialize In-use Mutexs
-	mutex_manager.used.start.value = 0;
-	mutex_manager.used.start.next = &mutex_manager.used.end;
-	mutex_manager.used.start.entry_type = START_ENTRY;
-	mutex_manager.used.end.value = 0;
-	mutex_manager.used.end.next = &mutex_manager.used.start;
-	mutex_manager.used.end.entry_type = END_ENTRY;
 }
 
 struct Mutex* create_mutex(void* addr)
@@ -38,70 +31,45 @@ struct Mutex* create_mutex(void* addr)
 	struct Mutex* m = e->value;
 	m->pid = 0;
 	m->addr = addr;
-	push_to_queue(e, &mutex_manager.used);
+	mutex_manager.used_mutexes++;
 	return e->value;
 }
 
 unsigned char delete_mutex(struct Mutex* m)
 {
-	struct Entry* entry = find_value(m, &mutex_manager.used);
-	if (entry == 0)
+	unsigned long spacing = (unsigned long)&mutexs[1] - (unsigned long)&mutexs[0];
+	unsigned long difference = (unsigned long)m - (unsigned long)&mutexs[0];
+	unsigned long index = difference/spacing;
+	if (index >= MAX_MUTEXS)
 		return 1;
-	// Remove it from the queue
-	struct Entry* theentry = remove_next_from_queue(entry);
+	struct Entry* entry = &mutex_entries[index];
 	// Add it to the free queue
-	prepend_to_queue(theentry, &mutex_manager.free);
+	prepend_to_queue(entry, &mutex_manager.free);
 	return 0;
 }
 
 void uart_mutexes(void)
 {
-	struct Entry* entry = mutex_manager.used.start.next;
-	while (entry->entry_type == VALUE_ENTRY)
-	{
-		struct Mutex* m = entry->value;
-		uart_hex((unsigned long)m);
-		uart_char(' ');
-		uart_hex(m->pid);
-		uart_char(' ');
-		uart_hexn((unsigned long)m->addr);
-		entry = entry->next;
-	}
-	unsigned long count = 0;
-	entry = mutex_manager.free.start.next;
-	while (entry->entry_type == VALUE_ENTRY) {
-		count++;
-		entry = entry->next;
-	}
-	uart_hexn(count);
+	uart_hexn(mutex_manager.used_mutexes);
 }
 
-void lock_mutex(struct Mutex* m)
+unsigned char lock_mutex(struct Mutex* m)
 {
 	struct Thread* rthread = scheduler.rthread;
-	unsigned long rpid = rthread->pid;
 	unsigned long mode = getmode() & 0x1F;
 	if (mode == 0x10) {
-		// Find this mutex
-		struct Entry* mentry = find_value(m, &mutex_manager.used);
+		unsigned long spacing = (unsigned long)&mutexs[1] - (unsigned long)&mutexs[0];
+		unsigned long difference = (unsigned long)m - (unsigned long)&mutexs[0];
+		unsigned long index = difference/spacing;
 		// If it is not a managed mutex, break away
-		if (mentry == 0)
-			return;
-		struct Entry* entry = mutex_manager.used.start.next;
-		// Ensure this thread locks all mutexs sequentially
-		//  To avoid a deadlock
-		while (entry->entry_type == VALUE_ENTRY) {
-			struct Mutex* vmutex = entry->value;
-			// If this thread had locked it
-			//  Toggle the lock to prevent deadlock
-			if (vmutex->pid == rpid) {
-				sys1(SYS_UNLOCK, vmutex);
-				sys1(SYS_LOCK, vmutex);
-			}
-			entry = entry->next;
-		}
+		if (index >= MAX_MUTEXS)
+			return 1;
+		if ((unsigned char) index > rthread->highest_mutex)
+			return 2;
 		sys1(SYS_LOCK, m);
+		return 0;
 	}
+	return 3;
 }
 
 void unlock_mutex(struct Mutex* m)
-- 
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