Paolo Bonzini | 9257d46 | 2011-03-12 17:43:52 +0100 | [diff] [blame] | 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 | exit(1); |
| 28 | } |
| 29 | |
| 30 | void qemu_mutex_init(QemuMutex *mutex) |
| 31 | { |
| 32 | mutex->owner = 0; |
| 33 | InitializeCriticalSection(&mutex->lock); |
| 34 | } |
| 35 | |
Stefan Weil | 1a290ae | 2011-03-13 19:00:52 +0100 | [diff] [blame] | 36 | void qemu_mutex_destroy(QemuMutex *mutex) |
| 37 | { |
| 38 | assert(mutex->owner == 0); |
| 39 | DeleteCriticalSection(&mutex->lock); |
| 40 | } |
| 41 | |
Paolo Bonzini | 9257d46 | 2011-03-12 17:43:52 +0100 | [diff] [blame] | 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 | |
Stefan Weil | 1a290ae | 2011-03-13 19:00:52 +0100 | [diff] [blame] | 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 | |
Paolo Bonzini | 9257d46 | 2011-03-12 17:43:52 +0100 | [diff] [blame] | 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 | QemuThread *thread; |
| 197 | void *(*start_routine)(void *); |
| 198 | void *arg; |
| 199 | }; |
| 200 | |
| 201 | static int qemu_thread_tls_index = TLS_OUT_OF_INDEXES; |
| 202 | |
| 203 | static unsigned __stdcall win32_start_routine(void *arg) |
| 204 | { |
| 205 | struct QemuThreadData data = *(struct QemuThreadData *) arg; |
| 206 | QemuThread *thread = data.thread; |
| 207 | |
| 208 | free(arg); |
| 209 | TlsSetValue(qemu_thread_tls_index, thread); |
| 210 | |
| 211 | /* |
| 212 | * Use DuplicateHandle instead of assigning thread->thread in the |
| 213 | * creating thread to avoid races. It's simpler this way than with |
| 214 | * synchronization. |
| 215 | */ |
| 216 | DuplicateHandle(GetCurrentProcess(), GetCurrentThread(), |
| 217 | GetCurrentProcess(), &thread->thread, |
| 218 | 0, FALSE, DUPLICATE_SAME_ACCESS); |
| 219 | |
| 220 | qemu_thread_exit(data.start_routine(data.arg)); |
| 221 | abort(); |
| 222 | } |
| 223 | |
| 224 | void qemu_thread_exit(void *arg) |
| 225 | { |
| 226 | QemuThread *thread = TlsGetValue(qemu_thread_tls_index); |
| 227 | thread->ret = arg; |
| 228 | CloseHandle(thread->thread); |
| 229 | thread->thread = NULL; |
| 230 | ExitThread(0); |
| 231 | } |
| 232 | |
| 233 | static inline void qemu_thread_init(void) |
| 234 | { |
| 235 | if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) { |
| 236 | qemu_thread_tls_index = TlsAlloc(); |
| 237 | if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) { |
| 238 | error_exit(ERROR_NO_SYSTEM_RESOURCES, __func__); |
| 239 | } |
| 240 | } |
| 241 | } |
| 242 | |
| 243 | |
| 244 | void qemu_thread_create(QemuThread *thread, |
| 245 | void *(*start_routine)(void *), |
| 246 | void *arg) |
| 247 | { |
| 248 | HANDLE hThread; |
| 249 | |
| 250 | struct QemuThreadData *data; |
| 251 | qemu_thread_init(); |
| 252 | data = qemu_malloc(sizeof *data); |
| 253 | data->thread = thread; |
| 254 | data->start_routine = start_routine; |
| 255 | data->arg = arg; |
| 256 | |
| 257 | hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine, |
| 258 | data, 0, NULL); |
| 259 | if (!hThread) { |
| 260 | error_exit(GetLastError(), __func__); |
| 261 | } |
| 262 | CloseHandle(hThread); |
| 263 | } |
| 264 | |
| 265 | void qemu_thread_get_self(QemuThread *thread) |
| 266 | { |
| 267 | if (!thread->thread) { |
| 268 | /* In the main thread of the process. Initialize the QemuThread |
| 269 | pointer in TLS, and use the dummy GetCurrentThread handle as |
| 270 | the identifier for qemu_thread_is_self. */ |
| 271 | qemu_thread_init(); |
| 272 | TlsSetValue(qemu_thread_tls_index, thread); |
| 273 | thread->thread = GetCurrentThread(); |
| 274 | } |
| 275 | } |
| 276 | |
| 277 | int qemu_thread_is_self(QemuThread *thread) |
| 278 | { |
| 279 | QemuThread *this_thread = TlsGetValue(qemu_thread_tls_index); |
| 280 | return this_thread->thread == thread->thread; |
| 281 | } |