2 * QEMU coroutine implementation
4 * Copyright IBM, Corp. 2011
7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
8 * Kevin Wolf <kwolf@redhat.com>
10 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
11 * See the COPYING.LIB file in the top-level directory.
15 #ifndef QEMU_COROUTINE_H
16 #define QEMU_COROUTINE_H
19 #include "qemu/typedefs.h"
20 #include "qemu/queue.h"
21 #include "qemu/timer.h"
24 * Coroutines are a mechanism for stack switching and can be used for
25 * cooperative userspace threading. These functions provide a simple but
26 * useful flavor of coroutines that is suitable for writing sequential code,
27 * rather than callbacks, for operations that need to give up control while
28 * waiting for events to complete.
30 * These functions are re-entrant and may be used outside the global mutex.
34 * Mark a function that executes in coroutine context
36 * Functions that execute in coroutine context cannot be called directly from
37 * normal functions. In the future it would be nice to enable compiler or
38 * static checker support for catching such errors. This annotation might make
39 * it possible and in the meantime it serves as documentation.
43 * static void coroutine_fn foo(void) {
49 typedef struct Coroutine Coroutine
;
52 * Coroutine entry point
54 * When the coroutine is entered for the first time, opaque is passed in as an
57 * When this function returns, the coroutine is destroyed automatically and
58 * execution continues in the caller who last entered the coroutine.
60 typedef void coroutine_fn
CoroutineEntry(void *opaque
);
63 * Create a new coroutine
65 * Use qemu_coroutine_enter() to actually transfer control to the coroutine.
67 Coroutine
*qemu_coroutine_create(CoroutineEntry
*entry
);
70 * Transfer control to a coroutine
72 * The opaque argument is passed as the argument to the entry point when
73 * entering the coroutine for the first time. It is subsequently ignored.
75 void qemu_coroutine_enter(Coroutine
*coroutine
, void *opaque
);
78 * Transfer control back to a coroutine's caller
80 * This function does not return until the coroutine is re-entered using
81 * qemu_coroutine_enter().
83 void coroutine_fn
qemu_coroutine_yield(void);
86 * Get the currently executing coroutine
88 Coroutine
*coroutine_fn
qemu_coroutine_self(void);
91 * Return whether or not currently inside a coroutine
93 * This can be used to write functions that work both when in coroutine context
94 * and when not in coroutine context. Note that such functions cannot use the
95 * coroutine_fn annotation since they work outside coroutine context.
97 bool qemu_in_coroutine(void);
102 * CoQueues are a mechanism to queue coroutines in order to continue executing
103 * them later. They provide the fundamental primitives on which coroutine locks
106 typedef struct CoQueue
{
107 QTAILQ_HEAD(, Coroutine
) entries
;
112 * Initialise a CoQueue. This must be called before any other operation is used
115 void qemu_co_queue_init(CoQueue
*queue
);
118 * Adds the current coroutine to the CoQueue and transfers control to the
119 * caller of the coroutine.
121 void coroutine_fn
qemu_co_queue_wait(CoQueue
*queue
);
124 * Adds the current coroutine to the head of the CoQueue and transfers control to the
125 * caller of the coroutine.
127 void coroutine_fn
qemu_co_queue_wait_insert_head(CoQueue
*queue
);
130 * Restarts the next coroutine in the CoQueue and removes it from the queue.
132 * Returns true if a coroutine was restarted, false if the queue is empty.
134 bool coroutine_fn
qemu_co_queue_next(CoQueue
*queue
);
137 * Restarts all coroutines in the CoQueue and leaves the queue empty.
139 void coroutine_fn
qemu_co_queue_restart_all(CoQueue
*queue
);
142 * Enter the next coroutine in the queue
144 bool qemu_co_enter_next(CoQueue
*queue
);
147 * Checks if the CoQueue is empty.
149 bool qemu_co_queue_empty(CoQueue
*queue
);
153 * Provides a mutex that can be used to synchronise coroutines
155 typedef struct CoMutex
{
161 * Initialises a CoMutex. This must be called before any other operation is used
164 void qemu_co_mutex_init(CoMutex
*mutex
);
167 * Locks the mutex. If the lock cannot be taken immediately, control is
168 * transferred to the caller of the current coroutine.
170 void coroutine_fn
qemu_co_mutex_lock(CoMutex
*mutex
);
173 * Unlocks the mutex and schedules the next coroutine that was waiting for this
176 void coroutine_fn
qemu_co_mutex_unlock(CoMutex
*mutex
);
178 typedef struct CoRwlock
{
185 * Initialises a CoRwlock. This must be called before any other operation
186 * is used on the CoRwlock
188 void qemu_co_rwlock_init(CoRwlock
*lock
);
191 * Read locks the CoRwlock. If the lock cannot be taken immediately because
192 * of a parallel writer, control is transferred to the caller of the current
195 void qemu_co_rwlock_rdlock(CoRwlock
*lock
);
198 * Write Locks the mutex. If the lock cannot be taken immediately because
199 * of a parallel reader, control is transferred to the caller of the current
202 void qemu_co_rwlock_wrlock(CoRwlock
*lock
);
205 * Unlocks the read/write lock and schedules the next coroutine that was
206 * waiting for this lock to be run.
208 void qemu_co_rwlock_unlock(CoRwlock
*lock
);
211 * Yield the coroutine for a given duration
213 * Note this function uses timers and hence only works when a main loop is in
214 * use. See main-loop.h and do not use from qemu-tool programs.
216 void coroutine_fn
co_sleep_ns(QEMUClockType type
, int64_t ns
);
219 * Yield until a file descriptor becomes readable
221 * Note that this function clobbers the handlers for the file descriptor.
223 void coroutine_fn
yield_until_fd_readable(int fd
);
224 #endif /* QEMU_COROUTINE_H */