xref: /openbmc/qemu/util/qemu-thread-win32.c (revision 6c5df4b4)
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 
14 #include "qemu/osdep.h"
15 #include "qemu/thread.h"
16 #include "qemu/notify.h"
17 #include "qemu-thread-common.h"
18 #include <process.h>
19 
20 static bool name_threads;
21 
22 typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
23                                                  PCWSTR lpThreadDescription);
24 static pSetThreadDescription SetThreadDescriptionFunc;
25 static HMODULE kernel32_module;
26 
load_set_thread_description(void)27 static bool load_set_thread_description(void)
28 {
29     static gsize _init_once = 0;
30 
31     if (g_once_init_enter(&_init_once)) {
32         kernel32_module = LoadLibrary("kernel32.dll");
33         if (kernel32_module) {
34             SetThreadDescriptionFunc =
35                 (pSetThreadDescription)GetProcAddress(kernel32_module,
36                                                       "SetThreadDescription");
37             if (!SetThreadDescriptionFunc) {
38                 FreeLibrary(kernel32_module);
39             }
40         }
41         g_once_init_leave(&_init_once, 1);
42     }
43 
44     return !!SetThreadDescriptionFunc;
45 }
46 
qemu_thread_naming(bool enable)47 void qemu_thread_naming(bool enable)
48 {
49     name_threads = enable;
50 
51     if (enable && !load_set_thread_description()) {
52         fprintf(stderr, "qemu: thread naming not supported on this host\n");
53         name_threads = false;
54     }
55 }
56 
error_exit(int err,const char * msg)57 static void error_exit(int err, const char *msg)
58 {
59     char *pstr;
60 
61     FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,
62                   NULL, err, 0, (LPTSTR)&pstr, 2, NULL);
63     fprintf(stderr, "qemu: %s: %s\n", msg, pstr);
64     LocalFree(pstr);
65     abort();
66 }
67 
qemu_mutex_init(QemuMutex * mutex)68 void qemu_mutex_init(QemuMutex *mutex)
69 {
70     InitializeSRWLock(&mutex->lock);
71     qemu_mutex_post_init(mutex);
72 }
73 
qemu_mutex_destroy(QemuMutex * mutex)74 void qemu_mutex_destroy(QemuMutex *mutex)
75 {
76     assert(mutex->initialized);
77     mutex->initialized = false;
78     InitializeSRWLock(&mutex->lock);
79 }
80 
qemu_mutex_lock_impl(QemuMutex * mutex,const char * file,const int line)81 void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line)
82 {
83     assert(mutex->initialized);
84     qemu_mutex_pre_lock(mutex, file, line);
85     AcquireSRWLockExclusive(&mutex->lock);
86     qemu_mutex_post_lock(mutex, file, line);
87 }
88 
qemu_mutex_trylock_impl(QemuMutex * mutex,const char * file,const int line)89 int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line)
90 {
91     int owned;
92 
93     assert(mutex->initialized);
94     owned = TryAcquireSRWLockExclusive(&mutex->lock);
95     if (owned) {
96         qemu_mutex_post_lock(mutex, file, line);
97         return 0;
98     }
99     return -EBUSY;
100 }
101 
qemu_mutex_unlock_impl(QemuMutex * mutex,const char * file,const int line)102 void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line)
103 {
104     assert(mutex->initialized);
105     qemu_mutex_pre_unlock(mutex, file, line);
106     ReleaseSRWLockExclusive(&mutex->lock);
107 }
108 
qemu_rec_mutex_init(QemuRecMutex * mutex)109 void qemu_rec_mutex_init(QemuRecMutex *mutex)
110 {
111     InitializeCriticalSection(&mutex->lock);
112     mutex->initialized = true;
113 }
114 
qemu_rec_mutex_destroy(QemuRecMutex * mutex)115 void qemu_rec_mutex_destroy(QemuRecMutex *mutex)
116 {
117     assert(mutex->initialized);
118     mutex->initialized = false;
119     DeleteCriticalSection(&mutex->lock);
120 }
121 
qemu_rec_mutex_lock_impl(QemuRecMutex * mutex,const char * file,int line)122 void qemu_rec_mutex_lock_impl(QemuRecMutex *mutex, const char *file, int line)
123 {
124     assert(mutex->initialized);
125     EnterCriticalSection(&mutex->lock);
126 }
127 
qemu_rec_mutex_trylock_impl(QemuRecMutex * mutex,const char * file,int line)128 int qemu_rec_mutex_trylock_impl(QemuRecMutex *mutex, const char *file, int line)
129 {
130     assert(mutex->initialized);
131     return !TryEnterCriticalSection(&mutex->lock);
132 }
133 
qemu_rec_mutex_unlock_impl(QemuRecMutex * mutex,const char * file,int line)134 void qemu_rec_mutex_unlock_impl(QemuRecMutex *mutex, const char *file, int line)
135 {
136     assert(mutex->initialized);
137     LeaveCriticalSection(&mutex->lock);
138 }
139 
qemu_cond_init(QemuCond * cond)140 void qemu_cond_init(QemuCond *cond)
141 {
142     memset(cond, 0, sizeof(*cond));
143     InitializeConditionVariable(&cond->var);
144     cond->initialized = true;
145 }
146 
qemu_cond_destroy(QemuCond * cond)147 void qemu_cond_destroy(QemuCond *cond)
148 {
149     assert(cond->initialized);
150     cond->initialized = false;
151     InitializeConditionVariable(&cond->var);
152 }
153 
qemu_cond_signal(QemuCond * cond)154 void qemu_cond_signal(QemuCond *cond)
155 {
156     assert(cond->initialized);
157     WakeConditionVariable(&cond->var);
158 }
159 
qemu_cond_broadcast(QemuCond * cond)160 void qemu_cond_broadcast(QemuCond *cond)
161 {
162     assert(cond->initialized);
163     WakeAllConditionVariable(&cond->var);
164 }
165 
qemu_cond_wait_impl(QemuCond * cond,QemuMutex * mutex,const char * file,const int line)166 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
167 {
168     assert(cond->initialized);
169     qemu_mutex_pre_unlock(mutex, file, line);
170     SleepConditionVariableSRW(&cond->var, &mutex->lock, INFINITE, 0);
171     qemu_mutex_post_lock(mutex, file, line);
172 }
173 
qemu_cond_timedwait_impl(QemuCond * cond,QemuMutex * mutex,int ms,const char * file,const int line)174 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
175                               const char *file, const int line)
176 {
177     int rc = 0;
178 
179     assert(cond->initialized);
180     trace_qemu_mutex_unlock(mutex, file, line);
181     if (!SleepConditionVariableSRW(&cond->var, &mutex->lock, ms, 0)) {
182         rc = GetLastError();
183     }
184     trace_qemu_mutex_locked(mutex, file, line);
185     if (rc && rc != ERROR_TIMEOUT) {
186         error_exit(rc, __func__);
187     }
188     return rc != ERROR_TIMEOUT;
189 }
190 
qemu_sem_init(QemuSemaphore * sem,int init)191 void qemu_sem_init(QemuSemaphore *sem, int init)
192 {
193     /* Manual reset.  */
194     sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
195     sem->initialized = true;
196 }
197 
qemu_sem_destroy(QemuSemaphore * sem)198 void qemu_sem_destroy(QemuSemaphore *sem)
199 {
200     assert(sem->initialized);
201     sem->initialized = false;
202     CloseHandle(sem->sema);
203 }
204 
qemu_sem_post(QemuSemaphore * sem)205 void qemu_sem_post(QemuSemaphore *sem)
206 {
207     assert(sem->initialized);
208     ReleaseSemaphore(sem->sema, 1, NULL);
209 }
210 
qemu_sem_timedwait(QemuSemaphore * sem,int ms)211 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
212 {
213     int rc;
214 
215     assert(sem->initialized);
216     rc = WaitForSingleObject(sem->sema, ms);
217     if (rc == WAIT_OBJECT_0) {
218         return 0;
219     }
220     if (rc != WAIT_TIMEOUT) {
221         error_exit(GetLastError(), __func__);
222     }
223     return -1;
224 }
225 
qemu_sem_wait(QemuSemaphore * sem)226 void qemu_sem_wait(QemuSemaphore *sem)
227 {
228     assert(sem->initialized);
229     if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
230         error_exit(GetLastError(), __func__);
231     }
232 }
233 
234 /* Wrap a Win32 manual-reset event with a fast userspace path.  The idea
235  * is to reset the Win32 event lazily, as part of a test-reset-test-wait
236  * sequence.  Such a sequence is, indeed, how QemuEvents are used by
237  * RCU and other subsystems!
238  *
239  * Valid transitions:
240  * - free->set, when setting the event
241  * - busy->set, when setting the event, followed by SetEvent
242  * - set->free, when resetting the event
243  * - free->busy, when waiting
244  *
245  * set->busy does not happen (it can be observed from the outside but
246  * it really is set->free->busy).
247  *
248  * busy->free provably cannot happen; to enforce it, the set->free transition
249  * is done with an OR, which becomes a no-op if the event has concurrently
250  * transitioned to free or busy (and is faster than cmpxchg).
251  */
252 
253 #define EV_SET         0
254 #define EV_FREE        1
255 #define EV_BUSY       -1
256 
qemu_event_init(QemuEvent * ev,bool init)257 void qemu_event_init(QemuEvent *ev, bool init)
258 {
259     /* Manual reset.  */
260     ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
261     ev->value = (init ? EV_SET : EV_FREE);
262     ev->initialized = true;
263 }
264 
qemu_event_destroy(QemuEvent * ev)265 void qemu_event_destroy(QemuEvent *ev)
266 {
267     assert(ev->initialized);
268     ev->initialized = false;
269     CloseHandle(ev->event);
270 }
271 
qemu_event_set(QemuEvent * ev)272 void qemu_event_set(QemuEvent *ev)
273 {
274     assert(ev->initialized);
275 
276     /*
277      * Pairs with both qemu_event_reset() and qemu_event_wait().
278      *
279      * qemu_event_set has release semantics, but because it *loads*
280      * ev->value we need a full memory barrier here.
281      */
282     smp_mb();
283     if (qatomic_read(&ev->value) != EV_SET) {
284         int old = qatomic_xchg(&ev->value, EV_SET);
285 
286         /* Pairs with memory barrier after ResetEvent.  */
287         smp_mb__after_rmw();
288         if (old == EV_BUSY) {
289             /* There were waiters, wake them up.  */
290             SetEvent(ev->event);
291         }
292     }
293 }
294 
qemu_event_reset(QemuEvent * ev)295 void qemu_event_reset(QemuEvent *ev)
296 {
297     assert(ev->initialized);
298 
299     /*
300      * If there was a concurrent reset (or even reset+wait),
301      * do nothing.  Otherwise change EV_SET->EV_FREE.
302      */
303     qatomic_or(&ev->value, EV_FREE);
304 
305     /*
306      * Order reset before checking the condition in the caller.
307      * Pairs with the first memory barrier in qemu_event_set().
308      */
309     smp_mb__after_rmw();
310 }
311 
qemu_event_wait(QemuEvent * ev)312 void qemu_event_wait(QemuEvent *ev)
313 {
314     unsigned value;
315 
316     assert(ev->initialized);
317 
318     /*
319      * qemu_event_wait must synchronize with qemu_event_set even if it does
320      * not go down the slow path, so this load-acquire is needed that
321      * synchronizes with the first memory barrier in qemu_event_set().
322      *
323      * If we do go down the slow path, there is no requirement at all: we
324      * might miss a qemu_event_set() here but ultimately the memory barrier in
325      * qemu_futex_wait() will ensure the check is done correctly.
326      */
327     value = qatomic_load_acquire(&ev->value);
328     if (value != EV_SET) {
329         if (value == EV_FREE) {
330             /*
331              * Here the underlying kernel event is reset, but qemu_event_set is
332              * not yet going to call SetEvent.  However, there will be another
333              * check for EV_SET below when setting EV_BUSY.  At that point it
334              * is safe to call WaitForSingleObject.
335              */
336             ResetEvent(ev->event);
337 
338             /*
339              * It is not clear whether ResetEvent provides this barrier; kernel
340              * APIs (KeResetEvent/KeClearEvent) do not.  Better safe than sorry!
341              */
342             smp_mb();
343 
344             /*
345              * Leave the event reset and tell qemu_event_set that there are
346              * waiters.  No need to retry, because there cannot be a concurrent
347              * busy->free transition.  After the CAS, the event will be either
348              * set or busy.
349              */
350             if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
351                 return;
352             }
353         }
354 
355         /*
356          * ev->value is now EV_BUSY.  Since we didn't observe EV_SET,
357          * qemu_event_set() must observe EV_BUSY and call SetEvent().
358          */
359         WaitForSingleObject(ev->event, INFINITE);
360     }
361 }
362 
363 struct QemuThreadData {
364     /* Passed to win32_start_routine.  */
365     void             *(*start_routine)(void *);
366     void             *arg;
367     short             mode;
368     NotifierList      exit;
369 
370     /* Only used for joinable threads. */
371     bool              exited;
372     void             *ret;
373     CRITICAL_SECTION  cs;
374 };
375 
376 static bool atexit_registered;
377 static NotifierList main_thread_exit;
378 
379 static __thread QemuThreadData *qemu_thread_data;
380 
run_main_thread_exit(void)381 static void run_main_thread_exit(void)
382 {
383     notifier_list_notify(&main_thread_exit, NULL);
384 }
385 
qemu_thread_atexit_add(Notifier * notifier)386 void qemu_thread_atexit_add(Notifier *notifier)
387 {
388     if (!qemu_thread_data) {
389         if (!atexit_registered) {
390             atexit_registered = true;
391             atexit(run_main_thread_exit);
392         }
393         notifier_list_add(&main_thread_exit, notifier);
394     } else {
395         notifier_list_add(&qemu_thread_data->exit, notifier);
396     }
397 }
398 
qemu_thread_atexit_remove(Notifier * notifier)399 void qemu_thread_atexit_remove(Notifier *notifier)
400 {
401     notifier_remove(notifier);
402 }
403 
win32_start_routine(void * arg)404 static unsigned __stdcall win32_start_routine(void *arg)
405 {
406     QemuThreadData *data = (QemuThreadData *) arg;
407     void *(*start_routine)(void *) = data->start_routine;
408     void *thread_arg = data->arg;
409 
410     qemu_thread_data = data;
411     qemu_thread_exit(start_routine(thread_arg));
412     abort();
413 }
414 
qemu_thread_exit(void * arg)415 void qemu_thread_exit(void *arg)
416 {
417     QemuThreadData *data = qemu_thread_data;
418 
419     notifier_list_notify(&data->exit, NULL);
420     if (data->mode == QEMU_THREAD_JOINABLE) {
421         data->ret = arg;
422         EnterCriticalSection(&data->cs);
423         data->exited = true;
424         LeaveCriticalSection(&data->cs);
425     } else {
426         g_free(data);
427     }
428     _endthreadex(0);
429 }
430 
qemu_thread_join(QemuThread * thread)431 void *qemu_thread_join(QemuThread *thread)
432 {
433     QemuThreadData *data;
434     void *ret;
435     HANDLE handle;
436 
437     data = thread->data;
438     if (data->mode == QEMU_THREAD_DETACHED) {
439         return NULL;
440     }
441 
442     /*
443      * Because multiple copies of the QemuThread can exist via
444      * qemu_thread_get_self, we need to store a value that cannot
445      * leak there.  The simplest, non racy way is to store the TID,
446      * discard the handle that _beginthreadex gives back, and
447      * get another copy of the handle here.
448      */
449     handle = qemu_thread_get_handle(thread);
450     if (handle) {
451         WaitForSingleObject(handle, INFINITE);
452         CloseHandle(handle);
453     }
454     ret = data->ret;
455     DeleteCriticalSection(&data->cs);
456     g_free(data);
457     return ret;
458 }
459 
set_thread_description(HANDLE h,const char * name)460 static bool set_thread_description(HANDLE h, const char *name)
461 {
462     HRESULT hr;
463     g_autofree wchar_t *namew = NULL;
464 
465     if (!load_set_thread_description()) {
466         return false;
467     }
468 
469     namew = g_utf8_to_utf16(name, -1, NULL, NULL, NULL);
470     if (!namew) {
471         return false;
472     }
473 
474     hr = SetThreadDescriptionFunc(h, namew);
475 
476     return SUCCEEDED(hr);
477 }
478 
qemu_thread_create(QemuThread * thread,const char * name,void * (* start_routine)(void *),void * arg,int mode)479 void qemu_thread_create(QemuThread *thread, const char *name,
480                        void *(*start_routine)(void *),
481                        void *arg, int mode)
482 {
483     HANDLE hThread;
484     struct QemuThreadData *data;
485 
486     data = g_malloc(sizeof *data);
487     data->start_routine = start_routine;
488     data->arg = arg;
489     data->mode = mode;
490     data->exited = false;
491     notifier_list_init(&data->exit);
492 
493     if (data->mode != QEMU_THREAD_DETACHED) {
494         InitializeCriticalSection(&data->cs);
495     }
496 
497     hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
498                                       data, 0, &thread->tid);
499     if (!hThread) {
500         error_exit(GetLastError(), __func__);
501     }
502     if (name_threads && name && !set_thread_description(hThread, name)) {
503         fprintf(stderr, "qemu: failed to set thread description: %s\n", name);
504     }
505     CloseHandle(hThread);
506 
507     thread->data = data;
508 }
509 
qemu_thread_set_affinity(QemuThread * thread,unsigned long * host_cpus,unsigned long nbits)510 int qemu_thread_set_affinity(QemuThread *thread, unsigned long *host_cpus,
511                              unsigned long nbits)
512 {
513     return -ENOSYS;
514 }
515 
qemu_thread_get_affinity(QemuThread * thread,unsigned long ** host_cpus,unsigned long * nbits)516 int qemu_thread_get_affinity(QemuThread *thread, unsigned long **host_cpus,
517                              unsigned long *nbits)
518 {
519     return -ENOSYS;
520 }
521 
qemu_thread_get_self(QemuThread * thread)522 void qemu_thread_get_self(QemuThread *thread)
523 {
524     thread->data = qemu_thread_data;
525     thread->tid = GetCurrentThreadId();
526 }
527 
qemu_thread_get_handle(QemuThread * thread)528 HANDLE qemu_thread_get_handle(QemuThread *thread)
529 {
530     QemuThreadData *data;
531     HANDLE handle;
532 
533     data = thread->data;
534     if (data->mode == QEMU_THREAD_DETACHED) {
535         return NULL;
536     }
537 
538     EnterCriticalSection(&data->cs);
539     if (!data->exited) {
540         handle = OpenThread(SYNCHRONIZE | THREAD_SUSPEND_RESUME |
541                             THREAD_SET_CONTEXT, FALSE, thread->tid);
542     } else {
543         handle = NULL;
544     }
545     LeaveCriticalSection(&data->cs);
546     return handle;
547 }
548 
qemu_thread_is_self(QemuThread * thread)549 bool qemu_thread_is_self(QemuThread *thread)
550 {
551     return GetCurrentThreadId() == thread->tid;
552 }
553