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/*
* QEMU coroutine implementation
*
* Copyright IBM, Corp. 2011
*
* Authors:
* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#ifndef QEMU_COROUTINE_H
#define QEMU_COROUTINE_H
#include <stdbool.h>
/**
* Coroutines are a mechanism for stack switching and can be used for
* cooperative userspace threading. These functions provide a simple but
* useful flavor of coroutines that is suitable for writing sequential code,
* rather than callbacks, for operations that need to give up control while
* waiting for events to complete.
*
* These functions are re-entrant and may be used outside the global mutex.
*/
/**
* Mark a function that executes in coroutine context
*
* Functions that execute in coroutine context cannot be called directly from
* normal functions. In the future it would be nice to enable compiler or
* static checker support for catching such errors. This annotation might make
* it possible and in the meantime it serves as documentation.
*
* For example:
*
* static void coroutine_fn foo(void) {
* ....
* }
*/
#define coroutine_fn
typedef struct Coroutine Coroutine;
/**
* Coroutine entry point
*
* When the coroutine is entered for the first time, opaque is passed in as an
* argument.
*
* When this function returns, the coroutine is destroyed automatically and
* execution continues in the caller who last entered the coroutine.
*/
typedef void coroutine_fn CoroutineEntry(void *opaque);
/**
* Create a new coroutine
*
* Use qemu_coroutine_enter() to actually transfer control to the coroutine.
*/
Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
/**
* Transfer control to a coroutine
*
* The opaque argument is passed as the argument to the entry point when
* entering the coroutine for the first time. It is subsequently ignored.
*/
void qemu_coroutine_enter(Coroutine *coroutine, void *opaque);
/**
* Transfer control back to a coroutine's caller
*
* This function does not return until the coroutine is re-entered using
* qemu_coroutine_enter().
*/
void coroutine_fn qemu_coroutine_yield(void);
/**
* Get the currently executing coroutine
*/
Coroutine *coroutine_fn qemu_coroutine_self(void);
/**
* Return whether or not currently inside a coroutine
*
* This can be used to write functions that work both when in coroutine context
* and when not in coroutine context. Note that such functions cannot use the
* coroutine_fn annotation since they work outside coroutine context.
*/
bool qemu_in_coroutine(void);
#endif /* QEMU_COROUTINE_H */
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