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diff --git a/util/coroutine-win32.c b/util/coroutine-win32.c
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+/*
+ * Win32 coroutine initialization code
+ *
+ * Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
+ *
+ * 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 "qemu-common.h"
+#include "qemu/coroutine_int.h"
+
+typedef struct
+{
+ Coroutine base;
+
+ LPVOID fiber;
+ CoroutineAction action;
+} CoroutineWin32;
+
+static __thread CoroutineWin32 leader;
+static __thread Coroutine *current;
+
+/* This function is marked noinline to prevent GCC from inlining it
+ * into coroutine_trampoline(). If we allow it to do that then it
+ * hoists the code to get the address of the TLS variable "current"
+ * out of the while() loop. This is an invalid transformation because
+ * the SwitchToFiber() call may be called when running thread A but
+ * return in thread B, and so we might be in a different thread
+ * context each time round the loop.
+ */
+CoroutineAction __attribute__((noinline))
+qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
+ CoroutineAction action)
+{
+ CoroutineWin32 *from = DO_UPCAST(CoroutineWin32, base, from_);
+ CoroutineWin32 *to = DO_UPCAST(CoroutineWin32, base, to_);
+
+ current = to_;
+
+ to->action = action;
+ SwitchToFiber(to->fiber);
+ return from->action;
+}
+
+static void CALLBACK coroutine_trampoline(void *co_)
+{
+ Coroutine *co = co_;
+
+ while (true) {
+ co->entry(co->entry_arg);
+ qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
+ }
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+ const size_t stack_size = 1 << 20;
+ CoroutineWin32 *co;
+
+ co = g_malloc0(sizeof(*co));
+ co->fiber = CreateFiber(stack_size, coroutine_trampoline, &co->base);
+ return &co->base;
+}
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+ CoroutineWin32 *co = DO_UPCAST(CoroutineWin32, base, co_);
+
+ DeleteFiber(co->fiber);
+ g_free(co);
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+ if (!current) {
+ current = &leader.base;
+ leader.fiber = ConvertThreadToFiber(NULL);
+ }
+ return current;
+}
+
+bool qemu_in_coroutine(void)
+{
+ return current && current->caller;
+}