Add mutex implementation

core/kthread.c

@@ -106,7 +106,6 @@ struct cpu_state *kthreadSwitch(struct cpu_state *prevCpu)
     currentThread->cpuState    = prevCpu;
     currentThread->state       = READY;
     struct kthread *nextThread = kthreadSelectNext();
-    printStringDetails(nextThread->name, RED, BLACK, 40, VGA_HEIGHT - 1);
     currentThread        = nextThread;
     currentThread->state = RUNNING;
     restore_IRQs(flags);
@@ -121,7 +120,7 @@ int kthreadOnJieffiesTick()
     disable_IRQs(flags);
     list_foreach(currentThread, nextThread, idx)
     {
-        if (nextThread->state == SLEEPING) {
+        if (nextThread->state == SLEEPING && nextThread->jiffiesSleeping) {
             nextThread->jiffiesSleeping--;
             if (!nextThread->jiffiesSleeping) {
                 nextThread->state = READY;
@@ -132,23 +131,62 @@ int kthreadOnJieffiesTick()
     return 0;
 }
 
-int kthreadYield()
+int kthreadUnsched(struct kthread *th)
+{
+    list_delete(currentThread, th);
+
+    return 0;
+}
+
+int kthreadSaveAndYield(struct kthread *current)
 {
     uint32_t flags;
+
     disable_IRQs(flags);
-    struct kthread *next    = kthreadSelectNext();
-    struct kthread *current = currentThread;
+    struct kthread *next = kthreadSelectNext();
+
     if (current == next) {
         restore_IRQs(flags);
         return 0;
     }
-    assert(current->state == RUNNING);
-    assert(next->state == READY);
-    current->state       = READY;
+
+    assertmsg(next->state == READY, "thread %s is in state %d\n", next->name, next->state);
+
+    if (current->state == RUNNING)
+        current->state = READY;
+
     currentThread        = next;
     currentThread->state = RUNNING;
     cpu_context_switch(&current->cpuState, next->cpuState);
     restore_IRQs(flags);
+
+    return 0;
+}
+
+int kthreadYield()
+{
+    uint32_t flags;
+
+    disable_IRQs(flags);
+    struct kthread *next    = kthreadSelectNext();
+    struct kthread *current = currentThread;
+
+    if (current == next) {
+        restore_IRQs(flags);
+        return 0;
+    }
+
+    assert(current->state == RUNNING);
+    assertmsg(next->state == READY, "thread %s is in state %d\n", next->name, next->state);
+
+    if (current->state == RUNNING)
+        current->state = READY;
+
+    currentThread        = next;
+    currentThread->state = RUNNING;
+    cpu_context_switch(&current->cpuState, next->cpuState);
+    restore_IRQs(flags);
+
     return 0;
 }
 
@@ -157,7 +195,8 @@ int kthreadMsleep(unsigned long msec)
     uint32_t flags;
     disable_IRQs(flags);
     struct kthread *current = currentThread;
-    assert(current->state == RUNNING);
+    assertmsg(current->state == RUNNING, "thread %s is in state %d for %d\n", current->name,
+              current->state, msec);
     current->state       = SLEEPING;
     struct kthread *next = kthreadSelectNext();
     assert(next != current);
@@ -174,3 +213,14 @@ struct kthread *getCurrenThread()
 {
     return currentThread;
 }
+
+int kthreadAddThread(struct kthread *th)
+{
+    if (th->state == READY)
+        return 0;
+
+    th->state = READY;
+    list_add_tail(currentThread, th);
+
+    return 0;
+}

core/kthread.h

@@ -11,6 +11,7 @@ typedef enum {
     RUNNING,
     READY,
     SLEEPING,
+    WAITING,
     EXITING
 } kthread_state;
 
@@ -35,6 +36,9 @@ struct kthread *kthreadSelectNext();
 struct cpu_state *kthreadSwitch(struct cpu_state *prevCpu);
 
 int kthreadYield();
+int kthreadSaveAndYield(struct kthread *);
 int kthreadMsleep(unsigned long msec);
 int kthreadOnJieffiesTick();
 struct kthread *getCurrenThread();
+int kthreadAddThread(struct kthread *th);
+int kthreadUnsched(struct kthread *th);

core/synchro.c

@@ -0,0 +1,92 @@
+#include "assert.h"
+#include "synchro.h"
+#include "alloc.h"
+#include "irq.h"
+#include "klibc.h"
+#include "list.h"
+#include "time.h"
+
+struct wait_queue *waitQueues = NULL;
+
+int mutexInit(struct mutex *m)
+{
+    uint32_t flags;
+
+    m->owner = NULL;
+    m->wait  = (struct wait_queue *)malloc(sizeof(struct wait_queue));
+    if (!m->wait)
+        return ENOMEM;
+    list_init(m->wait->thread);
+
+    disable_IRQs(flags);
+    list_add_tail(waitQueues, m->wait);
+    restore_IRQs(flags);
+
+    return 0;
+}
+
+int mutexFree(struct mutex *m)
+{
+    int ret = 0;
+
+    if (m) {
+        uint32_t flags;
+
+        disable_IRQs(flags);
+        if (list_is_empty(m->wait)) {
+#ifdef DEBUG
+            if (m->owner) {
+                printf("Warning: freeing a owned mutex 0x%. owned by 0x%p 0x%p\n", m, m->owner,
+                       getCurrenThread());
+            }
+#endif
+            list_delete(waitQueues, m->wait);
+            free(m->wait);
+        } else {
+            ret = EBUSY;
+        }
+        restore_IRQs(flags);
+    }
+
+    return ret;
+}
+
+int mutexLock(struct mutex *m)
+{
+    uint32_t flags;
+    struct kthread *current;
+
+    disable_IRQs(flags);
+    current = getCurrenThread();
+    assert(m->owner != current);
+    while (m->owner) {
+        kthreadUnsched(current);
+        list_add_tail(m->wait->thread, current);
+        current->state = WAITING;
+        kthreadSaveAndYield(current);
+    }
+    m->owner = current;
+
+    restore_IRQs(flags);
+
+    return 0;
+}
+
+int mutexUnlock(struct mutex *m)
+{
+    struct kthread *th;
+    uint32_t flags;
+
+    disable_IRQs(flags);
+    assert(m->owner == getCurrenThread());
+
+    m->owner = NULL;
+    
+    list_collapse(m->wait->thread, th){
+        kthreadAddThread(th);
+    }
+
+    restore_IRQs(flags);
+
+    return 0;
+}

core/synchro.h

@@ -0,0 +1,7 @@
+#pragma once
+#include <wait.h>
+
+int mutexInit(struct mutex *);
+int mutexFree(struct mutex *);
+int mutexLock(struct mutex *);
+int mutexUnlock(struct mutex *);

core/wait.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "kthread.h"
+
+struct wait_queue {
+    struct kthread *thread;
+    struct wait_queue *next;
+    struct wait_queue *prev;
+};
+
+struct semaphore {
+	int count;
+	struct wait_queue *wait;
+};
+
+struct mutex {
+        struct kthread *owner;
+        struct wait_queue *wait;
+};