hw/timer: Add value matching support to aspeed_timer
[qemu/ar7.git] / include / qemu / coroutine.h
blob305fe76c29d51654d394255e5facc196fe644c41
1 /*
2 * QEMU coroutine implementation
4 * Copyright IBM, Corp. 2011
6 * Authors:
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
18 #include "qemu/queue.h"
19 #include "qemu/timer.h"
21 /**
22 * Coroutines are a mechanism for stack switching and can be used for
23 * cooperative userspace threading. These functions provide a simple but
24 * useful flavor of coroutines that is suitable for writing sequential code,
25 * rather than callbacks, for operations that need to give up control while
26 * waiting for events to complete.
28 * These functions are re-entrant and may be used outside the global mutex.
31 /**
32 * Mark a function that executes in coroutine context
34 * Functions that execute in coroutine context cannot be called directly from
35 * normal functions. In the future it would be nice to enable compiler or
36 * static checker support for catching such errors. This annotation might make
37 * it possible and in the meantime it serves as documentation.
39 * For example:
41 * static void coroutine_fn foo(void) {
42 * ....
43 * }
45 #define coroutine_fn
47 typedef struct Coroutine Coroutine;
49 /**
50 * Coroutine entry point
52 * When the coroutine is entered for the first time, opaque is passed in as an
53 * argument.
55 * When this function returns, the coroutine is destroyed automatically and
56 * execution continues in the caller who last entered the coroutine.
58 typedef void coroutine_fn CoroutineEntry(void *opaque);
60 /**
61 * Create a new coroutine
63 * Use qemu_coroutine_enter() to actually transfer control to the coroutine.
65 Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
67 /**
68 * Transfer control to a coroutine
70 * The opaque argument is passed as the argument to the entry point when
71 * entering the coroutine for the first time. It is subsequently ignored.
73 void qemu_coroutine_enter(Coroutine *coroutine, void *opaque);
75 /**
76 * Transfer control back to a coroutine's caller
78 * This function does not return until the coroutine is re-entered using
79 * qemu_coroutine_enter().
81 void coroutine_fn qemu_coroutine_yield(void);
83 /**
84 * Get the currently executing coroutine
86 Coroutine *coroutine_fn qemu_coroutine_self(void);
88 /**
89 * Return whether or not currently inside a coroutine
91 * This can be used to write functions that work both when in coroutine context
92 * and when not in coroutine context. Note that such functions cannot use the
93 * coroutine_fn annotation since they work outside coroutine context.
95 bool qemu_in_coroutine(void);
99 /**
100 * CoQueues are a mechanism to queue coroutines in order to continue executing
101 * them later. They provide the fundamental primitives on which coroutine locks
102 * are built.
104 typedef struct CoQueue {
105 QTAILQ_HEAD(, Coroutine) entries;
106 } CoQueue;
109 * Initialise a CoQueue. This must be called before any other operation is used
110 * on the CoQueue.
112 void qemu_co_queue_init(CoQueue *queue);
115 * Adds the current coroutine to the CoQueue and transfers control to the
116 * caller of the coroutine.
118 void coroutine_fn qemu_co_queue_wait(CoQueue *queue);
121 * Restarts the next coroutine in the CoQueue and removes it from the queue.
123 * Returns true if a coroutine was restarted, false if the queue is empty.
125 bool coroutine_fn qemu_co_queue_next(CoQueue *queue);
128 * Restarts all coroutines in the CoQueue and leaves the queue empty.
130 void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue);
133 * Enter the next coroutine in the queue
135 bool qemu_co_enter_next(CoQueue *queue);
138 * Checks if the CoQueue is empty.
140 bool qemu_co_queue_empty(CoQueue *queue);
144 * Provides a mutex that can be used to synchronise coroutines
146 typedef struct CoMutex {
147 bool locked;
148 CoQueue queue;
149 } CoMutex;
152 * Initialises a CoMutex. This must be called before any other operation is used
153 * on the CoMutex.
155 void qemu_co_mutex_init(CoMutex *mutex);
158 * Locks the mutex. If the lock cannot be taken immediately, control is
159 * transferred to the caller of the current coroutine.
161 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
164 * Unlocks the mutex and schedules the next coroutine that was waiting for this
165 * lock to be run.
167 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
169 typedef struct CoRwlock {
170 bool writer;
171 int reader;
172 CoQueue queue;
173 } CoRwlock;
176 * Initialises a CoRwlock. This must be called before any other operation
177 * is used on the CoRwlock
179 void qemu_co_rwlock_init(CoRwlock *lock);
182 * Read locks the CoRwlock. If the lock cannot be taken immediately because
183 * of a parallel writer, control is transferred to the caller of the current
184 * coroutine.
186 void qemu_co_rwlock_rdlock(CoRwlock *lock);
189 * Write Locks the mutex. If the lock cannot be taken immediately because
190 * of a parallel reader, control is transferred to the caller of the current
191 * coroutine.
193 void qemu_co_rwlock_wrlock(CoRwlock *lock);
196 * Unlocks the read/write lock and schedules the next coroutine that was
197 * waiting for this lock to be run.
199 void qemu_co_rwlock_unlock(CoRwlock *lock);
202 * Yield the coroutine for a given duration
204 * Behaves similarly to co_sleep_ns(), but the sleeping coroutine will be
205 * resumed when using aio_poll().
207 void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
208 int64_t ns);
211 * Yield until a file descriptor becomes readable
213 * Note that this function clobbers the handlers for the file descriptor.
215 void coroutine_fn yield_until_fd_readable(int fd);
217 #endif /* QEMU_COROUTINE_H */