1 files changed, 152 insertions, 0 deletions

diff --git a/firmware/kernel/mutex.c b/firmware/kernel/mutex.c
new file mode 100644
index 0000000000..f1e4b3c722
--- /dev/null
+++ b/firmware/kernel/mutex.c
@@ -0,0 +1,152 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2002 by Björn Stenberg
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+
+/****************************************************************************
+ * Simple mutex functions ;)
+ ****************************************************************************/
+
+#include <stdbool.h>
+#include "config.h"
+#include "system.h"
+#include "mutex.h"
+#include "corelock.h"
+#include "thread-internal.h"
+#include "kernel-internal.h"
+
+static inline void __attribute__((always_inline))
+mutex_set_thread(struct mutex *mtx, struct thread_entry *td)
+{
+#ifdef HAVE_PRIORITY_SCHEDULING
+    mtx->blocker.thread = td;
+#else
+    mtx->thread = td;
+#endif
+}
+
+static inline struct thread_entry * __attribute__((always_inline))
+mutex_get_thread(volatile struct mutex *mtx)
+{
+#ifdef HAVE_PRIORITY_SCHEDULING
+    return mtx->blocker.thread;
+#else
+    return mtx->thread;
+#endif
+}
+
+/* Initialize a mutex object - call before any use and do not call again once
+ * the object is available to other threads */
+void mutex_init(struct mutex *m)
+{
+    corelock_init(&m->cl);
+    m->queue = NULL;
+    m->recursion = 0;
+    mutex_set_thread(m, NULL);
+#ifdef HAVE_PRIORITY_SCHEDULING
+    m->blocker.priority = PRIORITY_IDLE;
+    m->blocker.wakeup_protocol = wakeup_priority_protocol_transfer;
+    m->no_preempt = false;
+#endif
+}
+
+/* Gain ownership of a mutex object or block until it becomes free */
+void mutex_lock(struct mutex *m)
+{
+    struct thread_entry *current = thread_self_entry();
+
+    if(current == mutex_get_thread(m))
+    {
+        /* current thread already owns this mutex */
+        m->recursion++;
+        return;
+    }
+
+    /* lock out other cores */
+    corelock_lock(&m->cl);
+
+    /* must read thread again inside cs (a multiprocessor concern really) */
+    if(LIKELY(mutex_get_thread(m) == NULL))
+    {
+        /* lock is open */
+        mutex_set_thread(m, current);
+        corelock_unlock(&m->cl);
+        return;
+    }
+
+    /* block until the lock is open... */
+    IF_COP( current->obj_cl = &m->cl; )
+    IF_PRIO( current->blocker = &m->blocker; )
+    current->bqp = &m->queue;
+
+    disable_irq();
+    block_thread(current);
+
+    corelock_unlock(&m->cl);
+
+    /* ...and turn control over to next thread */
+    switch_thread();
+}
+
+/* Release ownership of a mutex object - only owning thread must call this */
+void mutex_unlock(struct mutex *m)
+{
+    /* unlocker not being the owner is an unlocking violation */
+    KERNEL_ASSERT(mutex_get_thread(m) == thread_self_entry(),
+                  "mutex_unlock->wrong thread (%s != %s)\n",
+                  mutex_get_thread(m)->name,
+                  thread_self_entry()->name);
+
+    if(m->recursion > 0)
+    {
+        /* this thread still owns lock */
+        m->recursion--;
+        return;
+    }
+
+    /* lock out other cores */
+    corelock_lock(&m->cl);
+
+    /* transfer to next queued thread if any */
+    if(LIKELY(m->queue == NULL))
+    {
+        /* no threads waiting - open the lock */
+        mutex_set_thread(m, NULL);
+        corelock_unlock(&m->cl);
+        return;
+    }
+    else
+    {
+        const int oldlevel = disable_irq_save();
+        /* Tranfer of owning thread is handled in the wakeup protocol
+         * if priorities are enabled otherwise just set it from the
+         * queue head. */
+        IFN_PRIO( mutex_set_thread(m, m->queue); )
+        IF_PRIO( unsigned int result = ) wakeup_thread(&m->queue);
+        restore_irq(oldlevel);
+
+        corelock_unlock(&m->cl);
+
+#ifdef HAVE_PRIORITY_SCHEDULING
+        if((result & THREAD_SWITCH) && !m->no_preempt)
+            switch_thread();
+#endif
+    }
+}