initial commit of lk (little kernel) project
diff --git a/kernel/mutex.c b/kernel/mutex.c
new file mode 100644
index 0000000..4998b6a
--- /dev/null
+++ b/kernel/mutex.c
@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2008 Travis Geiselbrecht
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <debug.h>
+#include <err.h>
+#include <kernel/mutex.h>
+#include <kernel/thread.h>
+
+#if DEBUGLEVEL > 1
+#define MUTEX_CHECK 1
+#endif
+
+void mutex_init(mutex_t *m)
+{
+#if MUTEX_CHECK
+// ASSERT(m->magic != MUTEX_MAGIC);
+#endif
+
+ m->magic = MUTEX_MAGIC;
+ m->count = 0;
+ m->holder = 0;
+ wait_queue_init(&m->wait);
+}
+
+void mutex_destroy(mutex_t *m)
+{
+ enter_critical_section();
+
+#if MUTEX_CHECK
+ ASSERT(m->magic == MUTEX_MAGIC);
+#endif
+
+ if (m->holder != 0 && current_thread != m->holder)
+ panic("mutex_destroy: thread %p (%s) tried to release mutex %p it doesn't own. owned by %p (%s)\n",
+ current_thread, current_thread->name, m, m->holder, m->holder ? m->holder->name : "none");
+
+ m->magic = 0;
+ m->count = 0;
+ wait_queue_destroy(&m->wait, true);
+ exit_critical_section();
+}
+
+status_t mutex_acquire(mutex_t *m)
+{
+ status_t ret = NO_ERROR;
+
+ if (current_thread == m->holder)
+ panic("mutex_acquire: thread %p (%s) tried to acquire mutex %p it already owns.\n",
+ current_thread, current_thread->name, m);
+
+ enter_critical_section();
+
+#if MUTEX_CHECK
+ ASSERT(m->magic == MUTEX_MAGIC);
+#endif
+
+// dprintf("mutex_acquire: m %p, count %d, curr %p\n", m, m->count, current_thread);
+
+ m->count++;
+ if (unlikely(m->count > 1)) {
+ /*
+ * block on the wait queue. If it returns an error, it was likely destroyed
+ * out from underneath us, so make sure we dont scribble thread ownership
+ * on the mutex.
+ */
+ ret = wait_queue_block(&m->wait, INFINITE_TIME);
+ if (ret < 0)
+ goto err;
+ }
+ m->holder = current_thread;
+
+err:
+ exit_critical_section();
+
+ return ret;
+}
+
+status_t mutex_acquire_timeout(mutex_t *m, time_t timeout)
+{
+ status_t ret = NO_ERROR;
+
+ if (current_thread == m->holder)
+ panic("mutex_acquire_timeout: thread %p (%s) tried to acquire mutex %p it already owns.\n",
+ current_thread, current_thread->name, m);
+
+ if (timeout == INFINITE_TIME)
+ return mutex_acquire(m);
+
+ enter_critical_section();
+
+#if MUTEX_CHECK
+ ASSERT(m->magic == MUTEX_MAGIC);
+#endif
+
+// dprintf("mutex_acquire_timeout: m %p, count %d, curr %p, timeout %d\n", m, m->count, current_thread, timeout);
+
+ m->count++;
+ if (unlikely(m->count > 1)) {
+ ret = wait_queue_block(&m->wait, timeout);
+ if (ret < NO_ERROR) {
+ /* if the acquisition timed out, back out the acquire and exit */
+ if (ret == ERR_TIMED_OUT) {
+ /*
+ * XXX race: the mutex may have been destroyed after the timeout,
+ * but before we got scheduled again which makes messing with the
+ * count variable dangerous.
+ */
+ m->count--;
+ goto err;
+ }
+ /* if there was a general error, it may have been destroyed out from
+ * underneath us, so just exit (which is really an invalid state anyway)
+ */
+ }
+ }
+ m->holder = current_thread;
+
+err:
+ exit_critical_section();
+
+ return ret;
+}
+
+status_t mutex_release(mutex_t *m)
+{
+ if (current_thread != m->holder)
+ panic("mutex_release: thread %p (%s) tried to release mutex %p it doesn't own. owned by %p (%s)\n",
+ current_thread, current_thread->name, m, m->holder, m->holder ? m->holder->name : "none");
+
+ enter_critical_section();
+
+#if MUTEX_CHECK
+ ASSERT(m->magic == MUTEX_MAGIC);
+#endif
+
+// dprintf("mutex_release: m %p, count %d, holder %p, curr %p\n", m, m->count, m->holder, current_thread);
+
+ m->holder = 0;
+ m->count--;
+ if (unlikely(m->count >= 1)) {
+ /* release a thread */
+// dprintf("releasing thread\n");
+ wait_queue_wake_one(&m->wait, true, NO_ERROR);
+ }
+
+ exit_critical_section();
+
+ return NO_ERROR;
+}
+