Implement cooperative threads on hosted platforms using C code.

This replaces SDL threads with real cooperative threads, which are less cpu intensive and allow priority scheduling.
The backend for context switching is dependant on the host (sigaltstack/longjmp on Unix, Fibers on Windows).
configure has options to force or disallow SDL threads.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29327 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 85 insertions, 0 deletions

diff --git a/firmware/target/hosted/thread-win32.c b/firmware/target/hosted/thread-win32.c
new file mode 100644
index 0000000000..a60198494a
--- /dev/null
+++ b/firmware/target/hosted/thread-win32.c
@@ -0,0 +1,85 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2010 by Thomas Martitz
+ *
+ * Generic ARM threading support
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+
+#include <windows.h>
+#include "system.h"
+
+#define INIT_MAIN_THREAD
+
+#define THREAD_STARTUP_INIT(core, thread, function) \
+    ({ (thread)->context.stack_size = (thread)->stack_size, \
+       (thread)->context.stack = (uintptr_t)(thread)->stack; \
+       (thread)->context.start = function; })
+
+static void init_main_thread(void *addr)
+{
+    struct regs *context = (struct regs*)addr;
+    /* we must convert the current main thread to a fiber to be able to
+     * schedule other fibers */
+    context->uc = ConvertThreadToFiber(NULL);
+    context->stack_size = 0;
+}
+
+static inline void store_context(void* addr)
+{
+    (void)addr;
+    /* nothing to do here, Fibers continue after the SwitchToFiber call */
+}
+
+static void start_thread(void)
+{
+    void (*func)(void) = GetFiberData();
+    func();
+    /* go out if thread function returns */
+    thread_exit();
+}
+
+/*
+ * Load context and run it
+ *
+ * Resume execution from the last load_context call for the thread
+ */
+
+static inline void load_context(const void* addr)
+{
+    struct regs *context = (struct regs*)addr;
+    if (UNLIKELY(context->start))
+    {   /* need setup before switching to it */
+        context->uc = CreateFiber(context->stack_size,
+                        (LPFIBER_START_ROUTINE)start_thread, context->start);
+        /* can't assign stack pointer, only stack size */
+        context->stack_size = 0;
+        context->start = NULL;
+    }
+    SwitchToFiber(context->uc);
+}
+
+/*
+ * play nice with the host and sleep while waiting for the tick */
+static inline void core_sleep(void)
+{
+    enable_irq();
+    wait_for_interrupt();
+}
+