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+/*
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+ * QEMU coroutine implementation
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+ *
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+ * Copyright IBM, Corp. 2011
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+ *
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+ * Authors:
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+ * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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+ * Kevin Wolf <kwolf@redhat.com>
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+ *
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+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
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+ * See the COPYING.LIB file in the top-level directory.
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+ *
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+ */
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+
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+#ifndef QEMU_COROUTINE_CORE_H
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+#define QEMU_COROUTINE_CORE_H
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+
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+/**
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+ * Coroutines are a mechanism for stack switching and can be used for
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+ * cooperative userspace threading. These functions provide a simple but
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+ * useful flavor of coroutines that is suitable for writing sequential code,
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+ * rather than callbacks, for operations that need to give up control while
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+ * waiting for events to complete.
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+ *
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+ * These functions are re-entrant and may be used outside the global mutex.
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+ *
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+ * Functions that execute in coroutine context cannot be called
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+ * directly from normal functions. Use @coroutine_fn to mark such
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+ * functions. For example:
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+ *
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+ * static void coroutine_fn foo(void) {
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+ * ....
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+ * }
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+ *
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+ * In the future it would be nice to have the compiler or a static
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+ * checker catch misuse of such functions. This annotation might make
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+ * it possible and in the meantime it serves as documentation.
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+ */
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+
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+/**
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+ * Mark a function that executes in coroutine context
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+ *
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+ *
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+ * Functions that execute in coroutine context cannot be called
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+ * directly from normal functions. Use @coroutine_fn to mark such
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+ * functions. For example:
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+ *
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+ * static void coroutine_fn foo(void) {
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+ * ....
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+ * }
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+ *
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+ * In the future it would be nice to have the compiler or a static
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+ * checker catch misuse of such functions. This annotation might make
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+ * it possible and in the meantime it serves as documentation.
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+ */
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+
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+typedef struct Coroutine Coroutine;
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+typedef struct CoMutex CoMutex;
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+
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+/**
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+ * Coroutine entry point
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+ *
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+ * When the coroutine is entered for the first time, opaque is passed in as an
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+ * argument.
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+ *
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+ * When this function returns, the coroutine is destroyed automatically and
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+ * execution continues in the caller who last entered the coroutine.
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+ */
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+typedef void coroutine_fn CoroutineEntry(void *opaque);
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+
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+/**
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+ * Create a new coroutine
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+ *
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+ * Use qemu_coroutine_enter() to actually transfer control to the coroutine.
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+ * The opaque argument is passed as the argument to the entry point.
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+ */
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+Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque);
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+
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+/**
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+ * Transfer control to a coroutine
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+ */
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+void qemu_coroutine_enter(Coroutine *coroutine);
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+
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+/**
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+ * Transfer control to a coroutine if it's not active (i.e. part of the call
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+ * stack of the running coroutine). Otherwise, do nothing.
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+ */
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+void qemu_coroutine_enter_if_inactive(Coroutine *co);
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+
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+/**
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+ * Transfer control to a coroutine and associate it with ctx
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+ */
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+void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co);
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+
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+/**
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+ * Transfer control back to a coroutine's caller
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+ *
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+ * This function does not return until the coroutine is re-entered using
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+ * qemu_coroutine_enter().
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+ */
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+void coroutine_fn qemu_coroutine_yield(void);
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+
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+/**
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+ * Get the AioContext of the given coroutine
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+ */
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+AioContext *qemu_coroutine_get_aio_context(Coroutine *co);
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+
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+/**
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+ * Get the currently executing coroutine
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+ */
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+Coroutine *qemu_coroutine_self(void);
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+
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+/**
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+ * Return whether or not currently inside a coroutine
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+ *
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+ * This can be used to write functions that work both when in coroutine context
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+ * and when not in coroutine context. Note that such functions cannot use the
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+ * coroutine_fn annotation since they work outside coroutine context.
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+ */
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+bool qemu_in_coroutine(void);
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+
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+/**
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+ * Return true if the coroutine is currently entered
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+ *
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+ * A coroutine is "entered" if it has not yielded from the current
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+ * qemu_coroutine_enter() call used to run it. This does not mean that the
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+ * coroutine is currently executing code since it may have transferred control
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+ * to another coroutine using qemu_coroutine_enter().
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+ *
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+ * When several coroutines enter each other there may be no way to know which
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+ * ones have already been entered. In such situations this function can be
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+ * used to avoid recursively entering coroutines.
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+ */
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+bool qemu_coroutine_entered(Coroutine *co);
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+
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+/**
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+ * Initialises a CoMutex. This must be called before any other operation is used
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+ * on the CoMutex.
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+ */
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+void qemu_co_mutex_init(CoMutex *mutex);
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+
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+/**
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+ * Locks the mutex. If the lock cannot be taken immediately, control is
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+ * transferred to the caller of the current coroutine.
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+ */
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+void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
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+
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+/**
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+ * Unlocks the mutex and schedules the next coroutine that was waiting for this
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+ * lock to be run.
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+ */
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+void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
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+
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+#endif
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Markus Armbruster