提交 403e6331 编写于 作者: P Paolo Bonzini 提交者: Anthony Liguori

qemu-thread: implement joinable threads for Win32

Rewrite the handshaking between qemu_thread_create and the
win32_start_routine, so that the thread can be joined without races.
Similar handshaking is done now between qemu_thread_exit and
qemu_thread_join.

This also simplifies how QemuThreads are initialized.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
上级 8763046b
......@@ -193,41 +193,78 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
}
struct QemuThreadData {
QemuThread *thread;
void *(*start_routine)(void *);
void *arg;
/* Passed to win32_start_routine. */
void *(*start_routine)(void *);
void *arg;
short mode;
/* Only used for joinable threads. */
bool exited;
void *ret;
CRITICAL_SECTION cs;
};
static int qemu_thread_tls_index = TLS_OUT_OF_INDEXES;
static unsigned __stdcall win32_start_routine(void *arg)
{
struct QemuThreadData data = *(struct QemuThreadData *) arg;
QemuThread *thread = data.thread;
free(arg);
TlsSetValue(qemu_thread_tls_index, thread);
/*
* Use DuplicateHandle instead of assigning thread->thread in the
* creating thread to avoid races. It's simpler this way than with
* synchronization.
*/
DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
GetCurrentProcess(), &thread->thread,
0, FALSE, DUPLICATE_SAME_ACCESS);
qemu_thread_exit(data.start_routine(data.arg));
QemuThreadData *data = (QemuThreadData *) arg;
void *(*start_routine)(void *) = data->start_routine;
void *thread_arg = data->arg;
if (data->mode == QEMU_THREAD_DETACHED) {
g_free(data);
data = NULL;
} else {
InitializeCriticalSection(&data->cs);
}
TlsSetValue(qemu_thread_tls_index, data);
qemu_thread_exit(start_routine(thread_arg));
abort();
}
void qemu_thread_exit(void *arg)
{
QemuThread *thread = TlsGetValue(qemu_thread_tls_index);
thread->ret = arg;
CloseHandle(thread->thread);
thread->thread = NULL;
ExitThread(0);
QemuThreadData *data = TlsGetValue(qemu_thread_tls_index);
if (data) {
data->ret = arg;
EnterCriticalSection(&data->cs);
data->exited = true;
LeaveCriticalSection(&data->cs);
}
_endthreadex(0);
}
void *qemu_thread_join(QemuThread *thread)
{
QemuThreadData *data;
void *ret;
HANDLE handle;
data = thread->data;
if (!data) {
return NULL;
}
/*
* Because multiple copies of the QemuThread can exist via
* qemu_thread_get_self, we need to store a value that cannot
* leak there. The simplest, non racy way is to store the TID,
* discard the handle that _beginthreadex gives back, and
* get another copy of the handle here.
*/
EnterCriticalSection(&data->cs);
if (!data->exited) {
handle = OpenThread(SYNCHRONIZE, FALSE, thread->tid);
LeaveCriticalSection(&data->cs);
WaitForSingleObject(handle, INFINITE);
CloseHandle(handle);
} else {
LeaveCriticalSection(&data->cs);
}
ret = data->ret;
DeleteCriticalSection(&data->cs);
g_free(data);
return ret;
}
static inline void qemu_thread_init(void)
......@@ -247,37 +284,31 @@ void qemu_thread_create(QemuThread *thread,
{
HANDLE hThread;
assert(mode == QEMU_THREAD_DETACHED);
struct QemuThreadData *data;
qemu_thread_init();
data = g_malloc(sizeof *data);
data->thread = thread;
data->start_routine = start_routine;
data->arg = arg;
data->mode = mode;
data->exited = false;
hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
data, 0, NULL);
data, 0, &thread->tid);
if (!hThread) {
error_exit(GetLastError(), __func__);
}
CloseHandle(hThread);
thread->data = (mode == QEMU_THREAD_DETACHED) ? NULL : data;
}
void qemu_thread_get_self(QemuThread *thread)
{
if (!thread->thread) {
/* In the main thread of the process. Initialize the QemuThread
pointer in TLS, and use the dummy GetCurrentThread handle as
the identifier for qemu_thread_is_self. */
qemu_thread_init();
TlsSetValue(qemu_thread_tls_index, thread);
thread->thread = GetCurrentThread();
}
qemu_thread_init();
thread->data = TlsGetValue(qemu_thread_tls_index);
thread->tid = GetCurrentThreadId();
}
int qemu_thread_is_self(QemuThread *thread)
{
QemuThread *this_thread = TlsGetValue(qemu_thread_tls_index);
return this_thread->thread == thread->thread;
return GetCurrentThreadId() == thread->tid;
}
......@@ -13,9 +13,10 @@ struct QemuCond {
HANDLE continue_event;
};
typedef struct QemuThreadData QemuThreadData;
struct QemuThread {
HANDLE thread;
void *ret;
QemuThreadData *data;
unsigned tid;
};
#endif
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