PPC: e500: msync is 440 only, e500 has real sync
[qemu.git] / qemu-thread-win32.c
1 /*
2 * Win32 implementation for mutex/cond/thread functions
3 *
4 * Copyright Red Hat, Inc. 2010
5 *
6 * Author:
7 * Paolo Bonzini <pbonzini@redhat.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2 or later.
10 * See the COPYING file in the top-level directory.
11 *
12 */
13 #include "qemu-common.h"
14 #include "qemu-thread.h"
15 #include <process.h>
16 #include <assert.h>
17 #include <limits.h>
18
19 static void error_exit(int err, const char *msg)
20 {
21 char *pstr;
22
23 FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,
24 NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
25 fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
26 LocalFree(pstr);
27 abort();
28 }
29
30 void qemu_mutex_init(QemuMutex *mutex)
31 {
32 mutex->owner = 0;
33 InitializeCriticalSection(&mutex->lock);
34 }
35
36 void qemu_mutex_destroy(QemuMutex *mutex)
37 {
38 assert(mutex->owner == 0);
39 DeleteCriticalSection(&mutex->lock);
40 }
41
42 void qemu_mutex_lock(QemuMutex *mutex)
43 {
44 EnterCriticalSection(&mutex->lock);
45
46 /* Win32 CRITICAL_SECTIONs are recursive. Assert that we're not
47 * using them as such.
48 */
49 assert(mutex->owner == 0);
50 mutex->owner = GetCurrentThreadId();
51 }
52
53 int qemu_mutex_trylock(QemuMutex *mutex)
54 {
55 int owned;
56
57 owned = TryEnterCriticalSection(&mutex->lock);
58 if (owned) {
59 assert(mutex->owner == 0);
60 mutex->owner = GetCurrentThreadId();
61 }
62 return !owned;
63 }
64
65 void qemu_mutex_unlock(QemuMutex *mutex)
66 {
67 assert(mutex->owner == GetCurrentThreadId());
68 mutex->owner = 0;
69 LeaveCriticalSection(&mutex->lock);
70 }
71
72 void qemu_cond_init(QemuCond *cond)
73 {
74 memset(cond, 0, sizeof(*cond));
75
76 cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
77 if (!cond->sema) {
78 error_exit(GetLastError(), __func__);
79 }
80 cond->continue_event = CreateEvent(NULL, /* security */
81 FALSE, /* auto-reset */
82 FALSE, /* not signaled */
83 NULL); /* name */
84 if (!cond->continue_event) {
85 error_exit(GetLastError(), __func__);
86 }
87 }
88
89 void qemu_cond_destroy(QemuCond *cond)
90 {
91 BOOL result;
92 result = CloseHandle(cond->continue_event);
93 if (!result) {
94 error_exit(GetLastError(), __func__);
95 }
96 cond->continue_event = 0;
97 result = CloseHandle(cond->sema);
98 if (!result) {
99 error_exit(GetLastError(), __func__);
100 }
101 cond->sema = 0;
102 }
103
104 void qemu_cond_signal(QemuCond *cond)
105 {
106 DWORD result;
107
108 /*
109 * Signal only when there are waiters. cond->waiters is
110 * incremented by pthread_cond_wait under the external lock,
111 * so we are safe about that.
112 */
113 if (cond->waiters == 0) {
114 return;
115 }
116
117 /*
118 * Waiting threads decrement it outside the external lock, but
119 * only if another thread is executing pthread_cond_broadcast and
120 * has the mutex. So, it also cannot be decremented concurrently
121 * with this particular access.
122 */
123 cond->target = cond->waiters - 1;
124 result = SignalObjectAndWait(cond->sema, cond->continue_event,
125 INFINITE, FALSE);
126 if (result == WAIT_ABANDONED || result == WAIT_FAILED) {
127 error_exit(GetLastError(), __func__);
128 }
129 }
130
131 void qemu_cond_broadcast(QemuCond *cond)
132 {
133 BOOLEAN result;
134 /*
135 * As in pthread_cond_signal, access to cond->waiters and
136 * cond->target is locked via the external mutex.
137 */
138 if (cond->waiters == 0) {
139 return;
140 }
141
142 cond->target = 0;
143 result = ReleaseSemaphore(cond->sema, cond->waiters, NULL);
144 if (!result) {
145 error_exit(GetLastError(), __func__);
146 }
147
148 /*
149 * At this point all waiters continue. Each one takes its
150 * slice of the semaphore. Now it's our turn to wait: Since
151 * the external mutex is held, no thread can leave cond_wait,
152 * yet. For this reason, we can be sure that no thread gets
153 * a chance to eat *more* than one slice. OTOH, it means
154 * that the last waiter must send us a wake-up.
155 */
156 WaitForSingleObject(cond->continue_event, INFINITE);
157 }
158
159 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
160 {
161 /*
162 * This access is protected under the mutex.
163 */
164 cond->waiters++;
165
166 /*
167 * Unlock external mutex and wait for signal.
168 * NOTE: we've held mutex locked long enough to increment
169 * waiters count above, so there's no problem with
170 * leaving mutex unlocked before we wait on semaphore.
171 */
172 qemu_mutex_unlock(mutex);
173 WaitForSingleObject(cond->sema, INFINITE);
174
175 /* Now waiters must rendez-vous with the signaling thread and
176 * let it continue. For cond_broadcast this has heavy contention
177 * and triggers thundering herd. So goes life.
178 *
179 * Decrease waiters count. The mutex is not taken, so we have
180 * to do this atomically.
181 *
182 * All waiters contend for the mutex at the end of this function
183 * until the signaling thread relinquishes it. To ensure
184 * each waiter consumes exactly one slice of the semaphore,
185 * the signaling thread stops until it is told by the last
186 * waiter that it can go on.
187 */
188 if (InterlockedDecrement(&cond->waiters) == cond->target) {
189 SetEvent(cond->continue_event);
190 }
191
192 qemu_mutex_lock(mutex);
193 }
194
195 struct QemuThreadData {
196 /* Passed to win32_start_routine. */
197 void *(*start_routine)(void *);
198 void *arg;
199 short mode;
200
201 /* Only used for joinable threads. */
202 bool exited;
203 void *ret;
204 CRITICAL_SECTION cs;
205 };
206
207 static int qemu_thread_tls_index = TLS_OUT_OF_INDEXES;
208
209 static unsigned __stdcall win32_start_routine(void *arg)
210 {
211 QemuThreadData *data = (QemuThreadData *) arg;
212 void *(*start_routine)(void *) = data->start_routine;
213 void *thread_arg = data->arg;
214
215 if (data->mode == QEMU_THREAD_DETACHED) {
216 g_free(data);
217 data = NULL;
218 } else {
219 InitializeCriticalSection(&data->cs);
220 }
221 TlsSetValue(qemu_thread_tls_index, data);
222 qemu_thread_exit(start_routine(thread_arg));
223 abort();
224 }
225
226 void qemu_thread_exit(void *arg)
227 {
228 QemuThreadData *data = TlsGetValue(qemu_thread_tls_index);
229 if (data) {
230 data->ret = arg;
231 EnterCriticalSection(&data->cs);
232 data->exited = true;
233 LeaveCriticalSection(&data->cs);
234 }
235 _endthreadex(0);
236 }
237
238 void *qemu_thread_join(QemuThread *thread)
239 {
240 QemuThreadData *data;
241 void *ret;
242 HANDLE handle;
243
244 data = thread->data;
245 if (!data) {
246 return NULL;
247 }
248 /*
249 * Because multiple copies of the QemuThread can exist via
250 * qemu_thread_get_self, we need to store a value that cannot
251 * leak there. The simplest, non racy way is to store the TID,
252 * discard the handle that _beginthreadex gives back, and
253 * get another copy of the handle here.
254 */
255 handle = qemu_thread_get_handle(thread);
256 if (handle) {
257 WaitForSingleObject(handle, INFINITE);
258 CloseHandle(handle);
259 }
260 ret = data->ret;
261 DeleteCriticalSection(&data->cs);
262 g_free(data);
263 return ret;
264 }
265
266 static inline void qemu_thread_init(void)
267 {
268 if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
269 qemu_thread_tls_index = TlsAlloc();
270 if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
271 error_exit(ERROR_NO_SYSTEM_RESOURCES, __func__);
272 }
273 }
274 }
275
276
277 void qemu_thread_create(QemuThread *thread,
278 void *(*start_routine)(void *),
279 void *arg, int mode)
280 {
281 HANDLE hThread;
282
283 struct QemuThreadData *data;
284 qemu_thread_init();
285 data = g_malloc(sizeof *data);
286 data->start_routine = start_routine;
287 data->arg = arg;
288 data->mode = mode;
289 data->exited = false;
290
291 hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
292 data, 0, &thread->tid);
293 if (!hThread) {
294 error_exit(GetLastError(), __func__);
295 }
296 CloseHandle(hThread);
297 thread->data = (mode == QEMU_THREAD_DETACHED) ? NULL : data;
298 }
299
300 void qemu_thread_get_self(QemuThread *thread)
301 {
302 qemu_thread_init();
303 thread->data = TlsGetValue(qemu_thread_tls_index);
304 thread->tid = GetCurrentThreadId();
305 }
306
307 HANDLE qemu_thread_get_handle(QemuThread *thread)
308 {
309 QemuThreadData *data;
310 HANDLE handle;
311
312 data = thread->data;
313 if (!data) {
314 return NULL;
315 }
316
317 EnterCriticalSection(&data->cs);
318 if (!data->exited) {
319 handle = OpenThread(SYNCHRONIZE | THREAD_SUSPEND_RESUME, FALSE,
320 thread->tid);
321 } else {
322 handle = NULL;
323 }
324 LeaveCriticalSection(&data->cs);
325 return handle;
326 }
327
328 int qemu_thread_is_self(QemuThread *thread)
329 {
330 return GetCurrentThreadId() == thread->tid;
331 }