1 files changed, 88 insertions, 0 deletions
diff --git a/kernel/proc/kmutex.c b/kernel/proc/kmutex.c
new file mode 100644
index 0000000..0433468
--- /dev/null
+++ b/kernel/proc/kmutex.c
@@ -0,0 +1,88 @@
+// SMP.1 + SMP.3
+// spinlock + mask interrupts
+#include "proc/kmutex.h"
+#include "globals.h"
+#include "main/interrupt.h"
+#include <errno.h>
+
+/*
+ * IMPORTANT: Mutexes can _NEVER_ be locked or unlocked from an
+ * interrupt context. Mutexes are _ONLY_ lock or unlocked from a
+ * thread context.
+ */
+
+/*
+ * Checks for the specific deadlock case where:
+ *  curthr wants mtx, but the owner of mtx is waiting on a mutex that curthr is
+ * holding
+ */
+#define DEBUG_DEADLOCKS 1
+void detect_deadlocks(kmutex_t *mtx)
+{
+#if DEBUG_DEADLOCKS
+    list_iterate(&curthr->kt_mutexes, held, kmutex_t, km_link)
+    {
+        list_iterate(&held->km_waitq.tq_list, waiter, kthread_t, kt_qlink)
+        {
+            if (waiter == mtx->km_holder)
+            {
+                panic(
+                    "detected deadlock between P%d and P%d (mutexes 0x%p, "
+                    "0x%p)\n",
+                    curproc->p_pid, waiter->kt_proc->p_pid, held, mtx);
+            }
+        }
+    }
+#endif
+}
+
+/*
+ * Initializes the members of mtx
+ */
+void kmutex_init(kmutex_t *mtx)
+{
+    NOT_YET_IMPLEMENTED("PROCS: ***none***");
+}
+
+/*
+ * Obtains a mutex, potentially blocking.
+ *
+ * Hints:
+ * You are strongly advised to maintain the kt_mutexes member of curthr and call
+ * detect_deadlocks() to help debugging.
+ */
+void kmutex_lock(kmutex_t *mtx)
+{
+    NOT_YET_IMPLEMENTED("PROCS: ***none***");
+}
+
+/*
+ * Releases a mutex.
+ *
+ * Hints:
+ * Again, you are strongly advised to maintain kt_mutexes.
+ * Use sched_wakeup_on() to hand off the mutex - think carefully about how
+ *  these two functions interact to ensure that the mutex's km_holder is
+ * properly set before the new owner is runnable.
+ */
+void kmutex_unlock(kmutex_t *mtx)
+{
+    NOT_YET_IMPLEMENTED("PROCS: ***none***");
+}
+
+/*
+ * Checks if mtx's wait queue is empty.
+ */
+long kmutex_has_waiters(kmutex_t *mtx)
+{
+    return !sched_queue_empty(&mtx->km_waitq);
+    ;
+}
+
+/*
+ * Checks if the current thread owns mtx.
+ */
+inline long kmutex_owns_mutex(kmutex_t *mtx)
+{
+    return curthr && mtx->km_holder == curthr;
+}