2011-03-12 17:43:52 +01:00
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/*
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* Win32 implementation for mutex/cond/thread functions
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*
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* Copyright Red Hat, Inc. 2010
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*
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* Author:
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* Paolo Bonzini <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#include "qemu-common.h"
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#include "qemu-thread.h"
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#include <process.h>
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#include <assert.h>
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#include <limits.h>
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static void error_exit(int err, const char *msg)
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{
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char *pstr;
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FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,
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NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
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fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
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LocalFree(pstr);
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2011-09-21 09:28:31 +02:00
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abort();
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2011-03-12 17:43:52 +01:00
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}
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void qemu_mutex_init(QemuMutex *mutex)
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{
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mutex->owner = 0;
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InitializeCriticalSection(&mutex->lock);
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}
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2011-03-13 19:00:52 +01:00
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void qemu_mutex_destroy(QemuMutex *mutex)
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{
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assert(mutex->owner == 0);
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DeleteCriticalSection(&mutex->lock);
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}
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2011-03-12 17:43:52 +01:00
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void qemu_mutex_lock(QemuMutex *mutex)
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{
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EnterCriticalSection(&mutex->lock);
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/* Win32 CRITICAL_SECTIONs are recursive. Assert that we're not
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* using them as such.
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*/
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assert(mutex->owner == 0);
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mutex->owner = GetCurrentThreadId();
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}
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int qemu_mutex_trylock(QemuMutex *mutex)
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{
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int owned;
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owned = TryEnterCriticalSection(&mutex->lock);
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if (owned) {
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assert(mutex->owner == 0);
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mutex->owner = GetCurrentThreadId();
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}
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return !owned;
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}
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void qemu_mutex_unlock(QemuMutex *mutex)
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{
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assert(mutex->owner == GetCurrentThreadId());
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mutex->owner = 0;
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LeaveCriticalSection(&mutex->lock);
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}
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void qemu_cond_init(QemuCond *cond)
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{
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memset(cond, 0, sizeof(*cond));
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cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
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if (!cond->sema) {
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error_exit(GetLastError(), __func__);
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}
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cond->continue_event = CreateEvent(NULL, /* security */
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FALSE, /* auto-reset */
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FALSE, /* not signaled */
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NULL); /* name */
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if (!cond->continue_event) {
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error_exit(GetLastError(), __func__);
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}
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}
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2011-03-13 19:00:52 +01:00
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void qemu_cond_destroy(QemuCond *cond)
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{
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BOOL result;
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result = CloseHandle(cond->continue_event);
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if (!result) {
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error_exit(GetLastError(), __func__);
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}
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cond->continue_event = 0;
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result = CloseHandle(cond->sema);
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if (!result) {
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error_exit(GetLastError(), __func__);
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}
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cond->sema = 0;
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}
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2011-03-12 17:43:52 +01:00
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void qemu_cond_signal(QemuCond *cond)
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{
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DWORD result;
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/*
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* Signal only when there are waiters. cond->waiters is
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* incremented by pthread_cond_wait under the external lock,
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* so we are safe about that.
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*/
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if (cond->waiters == 0) {
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return;
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}
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/*
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* Waiting threads decrement it outside the external lock, but
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* only if another thread is executing pthread_cond_broadcast and
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* has the mutex. So, it also cannot be decremented concurrently
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* with this particular access.
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*/
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cond->target = cond->waiters - 1;
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result = SignalObjectAndWait(cond->sema, cond->continue_event,
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INFINITE, FALSE);
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if (result == WAIT_ABANDONED || result == WAIT_FAILED) {
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error_exit(GetLastError(), __func__);
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}
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}
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void qemu_cond_broadcast(QemuCond *cond)
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{
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BOOLEAN result;
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/*
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* As in pthread_cond_signal, access to cond->waiters and
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* cond->target is locked via the external mutex.
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*/
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if (cond->waiters == 0) {
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return;
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}
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cond->target = 0;
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result = ReleaseSemaphore(cond->sema, cond->waiters, NULL);
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if (!result) {
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error_exit(GetLastError(), __func__);
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}
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/*
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* At this point all waiters continue. Each one takes its
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* slice of the semaphore. Now it's our turn to wait: Since
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* the external mutex is held, no thread can leave cond_wait,
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* yet. For this reason, we can be sure that no thread gets
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* a chance to eat *more* than one slice. OTOH, it means
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* that the last waiter must send us a wake-up.
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*/
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WaitForSingleObject(cond->continue_event, INFINITE);
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}
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void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
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{
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/*
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* This access is protected under the mutex.
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*/
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cond->waiters++;
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/*
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* Unlock external mutex and wait for signal.
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* NOTE: we've held mutex locked long enough to increment
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* waiters count above, so there's no problem with
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* leaving mutex unlocked before we wait on semaphore.
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*/
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qemu_mutex_unlock(mutex);
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WaitForSingleObject(cond->sema, INFINITE);
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/* Now waiters must rendez-vous with the signaling thread and
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* let it continue. For cond_broadcast this has heavy contention
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* and triggers thundering herd. So goes life.
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*
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* Decrease waiters count. The mutex is not taken, so we have
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* to do this atomically.
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*
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* All waiters contend for the mutex at the end of this function
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* until the signaling thread relinquishes it. To ensure
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* each waiter consumes exactly one slice of the semaphore,
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* the signaling thread stops until it is told by the last
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* waiter that it can go on.
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*/
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if (InterlockedDecrement(&cond->waiters) == cond->target) {
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SetEvent(cond->continue_event);
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}
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qemu_mutex_lock(mutex);
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}
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struct QemuThreadData {
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2011-12-12 17:21:33 +01:00
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/* Passed to win32_start_routine. */
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void *(*start_routine)(void *);
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void *arg;
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short mode;
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/* Only used for joinable threads. */
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bool exited;
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void *ret;
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CRITICAL_SECTION cs;
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2011-03-12 17:43:52 +01:00
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};
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static int qemu_thread_tls_index = TLS_OUT_OF_INDEXES;
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static unsigned __stdcall win32_start_routine(void *arg)
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{
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2011-12-12 17:21:33 +01:00
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QemuThreadData *data = (QemuThreadData *) arg;
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void *(*start_routine)(void *) = data->start_routine;
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void *thread_arg = data->arg;
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if (data->mode == QEMU_THREAD_DETACHED) {
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g_free(data);
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data = NULL;
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} else {
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InitializeCriticalSection(&data->cs);
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}
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TlsSetValue(qemu_thread_tls_index, data);
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qemu_thread_exit(start_routine(thread_arg));
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2011-03-12 17:43:52 +01:00
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abort();
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}
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void qemu_thread_exit(void *arg)
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{
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2011-12-12 17:21:33 +01:00
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QemuThreadData *data = TlsGetValue(qemu_thread_tls_index);
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if (data) {
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data->ret = arg;
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EnterCriticalSection(&data->cs);
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data->exited = true;
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LeaveCriticalSection(&data->cs);
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}
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_endthreadex(0);
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}
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void *qemu_thread_join(QemuThread *thread)
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{
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QemuThreadData *data;
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void *ret;
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HANDLE handle;
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data = thread->data;
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if (!data) {
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return NULL;
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}
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/*
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* Because multiple copies of the QemuThread can exist via
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* qemu_thread_get_self, we need to store a value that cannot
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* leak there. The simplest, non racy way is to store the TID,
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* discard the handle that _beginthreadex gives back, and
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* get another copy of the handle here.
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*/
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EnterCriticalSection(&data->cs);
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if (!data->exited) {
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handle = OpenThread(SYNCHRONIZE, FALSE, thread->tid);
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LeaveCriticalSection(&data->cs);
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WaitForSingleObject(handle, INFINITE);
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CloseHandle(handle);
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} else {
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LeaveCriticalSection(&data->cs);
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}
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ret = data->ret;
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DeleteCriticalSection(&data->cs);
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g_free(data);
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return ret;
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2011-03-12 17:43:52 +01:00
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}
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static inline void qemu_thread_init(void)
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{
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if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
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qemu_thread_tls_index = TlsAlloc();
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if (qemu_thread_tls_index == TLS_OUT_OF_INDEXES) {
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error_exit(ERROR_NO_SYSTEM_RESOURCES, __func__);
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}
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}
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}
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void qemu_thread_create(QemuThread *thread,
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void *(*start_routine)(void *),
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2011-12-12 17:21:31 +01:00
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void *arg, int mode)
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2011-03-12 17:43:52 +01:00
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{
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HANDLE hThread;
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struct QemuThreadData *data;
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qemu_thread_init();
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2011-08-21 05:09:37 +02:00
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data = g_malloc(sizeof *data);
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2011-03-12 17:43:52 +01:00
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data->start_routine = start_routine;
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data->arg = arg;
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2011-12-12 17:21:33 +01:00
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data->mode = mode;
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data->exited = false;
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2011-03-12 17:43:52 +01:00
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hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
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2011-12-12 17:21:33 +01:00
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data, 0, &thread->tid);
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2011-03-12 17:43:52 +01:00
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if (!hThread) {
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error_exit(GetLastError(), __func__);
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}
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CloseHandle(hThread);
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2011-12-12 17:21:33 +01:00
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thread->data = (mode == QEMU_THREAD_DETACHED) ? NULL : data;
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2011-03-12 17:43:52 +01:00
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}
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void qemu_thread_get_self(QemuThread *thread)
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{
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2011-12-12 17:21:33 +01:00
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qemu_thread_init();
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thread->data = TlsGetValue(qemu_thread_tls_index);
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thread->tid = GetCurrentThreadId();
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2011-03-12 17:43:52 +01:00
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}
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int qemu_thread_is_self(QemuThread *thread)
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{
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2011-12-12 17:21:33 +01:00
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return GetCurrentThreadId() == thread->tid;
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2011-03-12 17:43:52 +01:00
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}
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