2 * monitor.c: Monitor locking functions
5 * Dick Porter (dick@ximian.com)
7 * Copyright 2003 Ximian, Inc (http://www.ximian.com)
8 * Copyright 2004-2009 Novell, Inc (http://www.novell.com)
15 #include <mono/metadata/monitor.h>
16 #include <mono/metadata/threads-types.h>
17 #include <mono/metadata/exception.h>
18 #include <mono/metadata/threads.h>
19 #include <mono/io-layer/io-layer.h>
20 #include <mono/metadata/object-internals.h>
21 #include <mono/metadata/class-internals.h>
22 #include <mono/metadata/gc-internal.h>
23 #include <mono/metadata/method-builder.h>
24 #include <mono/metadata/debug-helpers.h>
25 #include <mono/metadata/tabledefs.h>
26 #include <mono/metadata/marshal.h>
27 #include <mono/metadata/profiler-private.h>
28 #include <mono/utils/mono-time.h>
31 * Pull the list of opcodes
33 #define OPDEF(a,b,c,d,e,f,g,h,i,j) \
37 #include "mono/cil/opcode.def"
42 /*#define LOCK_DEBUG(a) do { a; } while (0)*/
46 * The monitor implementation here is based on
47 * http://www.usenix.org/events/jvm01/full_papers/dice/dice.pdf and
48 * http://www.research.ibm.com/people/d/dfb/papers/Bacon98Thin.ps
50 * The Dice paper describes a technique for saving lock record space
51 * by returning records to a free list when they become unused. That
52 * sounds like unnecessary complexity to me, though if it becomes
53 * clear that unused lock records are taking up lots of space or we
54 * need to shave more time off by avoiding a malloc then we can always
55 * implement the free list idea later. The timeout parameter to
56 * try_enter voids some of the assumptions about the reference count
57 * field in Dice's implementation too. In his version, the thread
58 * attempting to lock a contended object will block until it succeeds,
59 * so the reference count will never be decremented while an object is
62 * Bacon's thin locks have a fast path that doesn't need a lock record
63 * for the common case of locking an unlocked or shallow-nested
64 * object, but the technique relies on encoding the thread ID in 15
65 * bits (to avoid too much per-object space overhead.) Unfortunately
66 * I don't think it's possible to reliably encode a pthread_t into 15
67 * bits. (The JVM implementation used seems to have a 15-bit
68 * per-thread identifier available.)
70 * This implementation then combines Dice's basic lock model with
71 * Bacon's simplification of keeping a lock record for the lifetime of
75 struct _MonoThreadsSync
77 gsize owner; /* thread ID */
79 #ifdef HAVE_MOVING_COLLECTOR
82 volatile gint32 entry_count;
88 typedef struct _MonitorArray MonitorArray;
90 struct _MonitorArray {
93 MonoThreadsSync monitors [MONO_ZERO_LEN_ARRAY];
96 #define mono_monitor_allocator_lock() EnterCriticalSection (&monitor_mutex)
97 #define mono_monitor_allocator_unlock() LeaveCriticalSection (&monitor_mutex)
98 static CRITICAL_SECTION monitor_mutex;
99 static MonoThreadsSync *monitor_freelist;
100 static MonitorArray *monitor_allocated;
101 static int array_size = 16;
103 #ifdef HAVE_KW_THREAD
104 static __thread gsize tls_pthread_self MONO_TLS_FAST;
108 #ifdef HAVE_KW_THREAD
109 #define GetCurrentThreadId() tls_pthread_self
112 * The usual problem: we can't replace GetCurrentThreadId () with a macro because
113 * it is in a public header.
115 #define GetCurrentThreadId() ((gsize)pthread_self ())
120 mono_monitor_init (void)
122 InitializeCriticalSection (&monitor_mutex);
126 mono_monitor_cleanup (void)
128 MonoThreadsSync *mon;
129 MonitorArray *marray, *next = NULL;
131 /*DeleteCriticalSection (&monitor_mutex);*/
133 /* The monitors on the freelist don't have weak links - mark them */
134 for (mon = monitor_freelist; mon; mon = mon->data)
135 mon->wait_list = (gpointer)-1;
137 for (marray = monitor_allocated; marray; marray = next) {
140 for (i = 0; i < marray->num_monitors; ++i) {
141 mon = &marray->monitors [i];
142 if (mon->wait_list != (gpointer)-1)
143 mono_gc_weak_link_remove (&mon->data);
152 * mono_monitor_init_tls:
154 * Setup TLS variables used by the monitor code for the current thread.
157 mono_monitor_init_tls (void)
159 #if !defined(HOST_WIN32) && defined(HAVE_KW_THREAD)
160 tls_pthread_self = pthread_self ();
165 monitor_is_on_freelist (MonoThreadsSync *mon)
167 MonitorArray *marray;
168 for (marray = monitor_allocated; marray; marray = marray->next) {
169 if (mon >= marray->monitors && mon < &marray->monitors [marray->num_monitors])
179 * Print a report on stdout of the managed locks currently held by
180 * threads. If @include_untaken is specified, list also inflated locks
182 * This is supposed to be used in debuggers like gdb.
185 mono_locks_dump (gboolean include_untaken)
188 int used = 0, on_freelist = 0, to_recycle = 0, total = 0, num_arrays = 0;
189 MonoThreadsSync *mon;
190 MonitorArray *marray;
191 for (mon = monitor_freelist; mon; mon = mon->data)
193 for (marray = monitor_allocated; marray; marray = marray->next) {
194 total += marray->num_monitors;
196 for (i = 0; i < marray->num_monitors; ++i) {
197 mon = &marray->monitors [i];
198 if (mon->data == NULL) {
199 if (i < marray->num_monitors - 1)
202 if (!monitor_is_on_freelist (mon->data)) {
203 MonoObject *holder = mono_gc_weak_link_get (&mon->data);
205 g_print ("Lock %p in object %p held by thread %p, nest level: %d\n",
206 mon, holder, (void*)mon->owner, mon->nest);
208 g_print ("\tWaiting on semaphore %p: %d\n", mon->entry_sem, mon->entry_count);
209 } else if (include_untaken) {
210 g_print ("Lock %p in object %p untaken\n", mon, holder);
217 g_print ("Total locks (in %d array(s)): %d, used: %d, on freelist: %d, to recycle: %d\n",
218 num_arrays, total, used, on_freelist, to_recycle);
221 /* LOCKING: this is called with monitor_mutex held */
223 mon_finalize (MonoThreadsSync *mon)
225 LOCK_DEBUG (g_message ("%s: Finalizing sync %p", __func__, mon));
227 if (mon->entry_sem != NULL) {
228 CloseHandle (mon->entry_sem);
229 mon->entry_sem = NULL;
231 /* If this isn't empty then something is seriously broken - it
232 * means a thread is still waiting on the object that owned
233 * this lock, but the object has been finalized.
235 g_assert (mon->wait_list == NULL);
237 mon->entry_count = 0;
238 /* owner and nest are set in mon_new, no need to zero them out */
240 mon->data = monitor_freelist;
241 monitor_freelist = mon;
242 mono_perfcounters->gc_sync_blocks--;
245 /* LOCKING: this is called with monitor_mutex held */
246 static MonoThreadsSync *
249 MonoThreadsSync *new;
251 if (!monitor_freelist) {
252 MonitorArray *marray;
254 /* see if any sync block has been collected */
256 for (marray = monitor_allocated; marray; marray = marray->next) {
257 for (i = 0; i < marray->num_monitors; ++i) {
258 if (marray->monitors [i].data == NULL) {
259 new = &marray->monitors [i];
260 if (new->wait_list) {
261 /* Orphaned events left by aborted threads */
262 while (new->wait_list) {
263 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d): Closing orphaned event %d", GetCurrentThreadId (), new->wait_list->data));
264 CloseHandle (new->wait_list->data);
265 new->wait_list = g_slist_remove (new->wait_list, new->wait_list->data);
268 mono_gc_weak_link_remove (&new->data);
269 new->data = monitor_freelist;
270 monitor_freelist = new;
273 /* small perf tweak to avoid scanning all the blocks */
277 /* need to allocate a new array of monitors */
278 if (!monitor_freelist) {
280 LOCK_DEBUG (g_message ("%s: allocating more monitors: %d", __func__, array_size));
281 marray = g_malloc0 (sizeof (MonoArray) + array_size * sizeof (MonoThreadsSync));
282 marray->num_monitors = array_size;
284 /* link into the freelist */
285 for (i = 0; i < marray->num_monitors - 1; ++i) {
286 marray->monitors [i].data = &marray->monitors [i + 1];
288 marray->monitors [i].data = NULL; /* the last one */
289 monitor_freelist = &marray->monitors [0];
290 /* we happend the marray instead of prepending so that
291 * the collecting loop above will need to scan smaller arrays first
293 if (!monitor_allocated) {
294 monitor_allocated = marray;
296 last = monitor_allocated;
304 new = monitor_freelist;
305 monitor_freelist = new->data;
310 mono_perfcounters->gc_sync_blocks++;
315 * Format of the lock word:
316 * thinhash | fathash | data
318 * thinhash is the lower bit: if set data is the shifted hashcode of the object.
319 * fathash is another bit: if set the hash code is stored in the MonoThreadsSync
320 * struct pointed to by data
321 * if neither bit is set and data is non-NULL, data is a MonoThreadsSync
325 MonoThreadsSync *sync;
329 LOCK_WORD_THIN_HASH = 1,
330 LOCK_WORD_FAT_HASH = 1 << 1,
331 LOCK_WORD_BITS_MASK = 0x3,
332 LOCK_WORD_HASH_SHIFT = 2
335 #define MONO_OBJECT_ALIGNMENT_SHIFT 3
341 * Calculate a hash code for @obj that is constant while @obj is alive.
344 mono_object_hash (MonoObject* obj)
346 #ifdef HAVE_MOVING_COLLECTOR
351 lw.sync = obj->synchronisation;
352 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
353 /*g_print ("fast thin hash %d for obj %p store\n", (unsigned int)lw.lock_word >> LOCK_WORD_HASH_SHIFT, obj);*/
354 return (unsigned int)lw.lock_word >> LOCK_WORD_HASH_SHIFT;
356 if (lw.lock_word & LOCK_WORD_FAT_HASH) {
357 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
358 /*g_print ("fast fat hash %d for obj %p store\n", lw.sync->hash_code, obj);*/
359 return lw.sync->hash_code;
362 * while we are inside this function, the GC will keep this object pinned,
363 * since we are in the unmanaged stack. Thanks to this and to the hash
364 * function that depends only on the address, we can ignore the races if
365 * another thread computes the hash at the same time, because it'll end up
366 * with the same value.
368 hash = (GPOINTER_TO_UINT (obj) >> MONO_OBJECT_ALIGNMENT_SHIFT) * 2654435761u;
369 /* clear the top bits as they can be discarded */
370 hash &= ~(LOCK_WORD_BITS_MASK << 30);
371 /* no hash flags were set, so it must be a MonoThreadsSync pointer if not NULL */
373 lw.sync->hash_code = hash;
374 /*g_print ("storing hash code %d for obj %p in sync %p\n", hash, obj, lw.sync);*/
375 lw.lock_word |= LOCK_WORD_FAT_HASH;
376 /* this is safe since we don't deflate locks */
377 obj->synchronisation = lw.sync;
379 /*g_print ("storing thin hash code %d for obj %p\n", hash, obj);*/
380 lw.lock_word = LOCK_WORD_THIN_HASH | (hash << LOCK_WORD_HASH_SHIFT);
381 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, NULL) == NULL)
383 /*g_print ("failed store\n");*/
384 /* someone set the hash flag or someone inflated the object */
385 lw.sync = obj->synchronisation;
386 if (lw.lock_word & LOCK_WORD_THIN_HASH)
388 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
389 lw.sync->hash_code = hash;
390 lw.lock_word |= LOCK_WORD_FAT_HASH;
391 /* this is safe since we don't deflate locks */
392 obj->synchronisation = lw.sync;
397 * Wang's address-based hash function:
398 * http://www.concentric.net/~Ttwang/tech/addrhash.htm
400 return (GPOINTER_TO_UINT (obj) >> MONO_OBJECT_ALIGNMENT_SHIFT) * 2654435761u;
404 /* If allow_interruption==TRUE, the method will be interrumped if abort or suspend
405 * is requested. In this case it returns -1.
408 mono_monitor_try_enter_internal (MonoObject *obj, guint32 ms, gboolean allow_interruption)
410 MonoThreadsSync *mon;
411 gsize id = GetCurrentThreadId ();
413 guint32 then = 0, now, delta;
416 MonoInternalThread *thread;
418 LOCK_DEBUG (g_message("%s: (%d) Trying to lock object %p (%d ms)", __func__, id, obj, ms));
420 if (G_UNLIKELY (!obj)) {
421 mono_raise_exception (mono_get_exception_argument_null ("obj"));
426 mon = obj->synchronisation;
428 /* If the object has never been locked... */
429 if (G_UNLIKELY (mon == NULL)) {
430 mono_monitor_allocator_lock ();
432 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, mon, NULL) == NULL) {
433 mono_gc_weak_link_add (&mon->data, obj, FALSE);
434 mono_monitor_allocator_unlock ();
435 /* Successfully locked */
438 #ifdef HAVE_MOVING_COLLECTOR
440 lw.sync = obj->synchronisation;
441 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
442 MonoThreadsSync *oldlw = lw.sync;
443 /* move the already calculated hash */
444 mon->hash_code = lw.lock_word >> LOCK_WORD_HASH_SHIFT;
446 lw.lock_word |= LOCK_WORD_FAT_HASH;
447 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, oldlw) == oldlw) {
448 mono_gc_weak_link_add (&mon->data, obj, FALSE);
449 mono_monitor_allocator_unlock ();
450 /* Successfully locked */
454 mono_monitor_allocator_unlock ();
457 } else if (lw.lock_word & LOCK_WORD_FAT_HASH) {
459 mono_monitor_allocator_unlock ();
460 /* get the old lock without the fat hash bit */
461 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
465 mono_monitor_allocator_unlock ();
466 mon = obj->synchronisation;
470 mono_monitor_allocator_unlock ();
471 mon = obj->synchronisation;
475 #ifdef HAVE_MOVING_COLLECTOR
478 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
479 MonoThreadsSync *oldlw = lw.sync;
480 mono_monitor_allocator_lock ();
482 /* move the already calculated hash */
483 mon->hash_code = lw.lock_word >> LOCK_WORD_HASH_SHIFT;
485 lw.lock_word |= LOCK_WORD_FAT_HASH;
486 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, oldlw) == oldlw) {
487 mono_gc_weak_link_add (&mon->data, obj, TRUE);
488 mono_monitor_allocator_unlock ();
489 /* Successfully locked */
493 mono_monitor_allocator_unlock ();
500 #ifdef HAVE_MOVING_COLLECTOR
504 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
509 /* If the object has previously been locked but isn't now... */
511 /* This case differs from Dice's case 3 because we don't
512 * deflate locks or cache unused lock records
514 if (G_LIKELY (mon->owner == 0)) {
515 /* Try to install our ID in the owner field, nest
516 * should have been left at 1 by the previous unlock
519 if (G_LIKELY (InterlockedCompareExchangePointer ((gpointer *)&mon->owner, (gpointer)id, 0) == 0)) {
521 g_assert (mon->nest == 1);
529 /* If the object is currently locked by this thread... */
530 if (mon->owner == id) {
535 /* The object must be locked by someone else... */
536 mono_perfcounters->thread_contentions++;
538 /* If ms is 0 we don't block, but just fail straight away */
540 LOCK_DEBUG (g_message ("%s: (%d) timed out, returning FALSE", __func__, id));
544 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_CONTENTION);
546 /* The slow path begins here. */
548 /* a small amount of duplicated code, but it allows us to insert the profiler
549 * callbacks without impacting the fast path: from here on we don't need to go back to the
550 * retry label, but to retry_contended. At this point mon is already installed in the object
553 /* This case differs from Dice's case 3 because we don't
554 * deflate locks or cache unused lock records
556 if (G_LIKELY (mon->owner == 0)) {
557 /* Try to install our ID in the owner field, nest
558 * should have been left at 1 by the previous unlock
561 if (G_LIKELY (InterlockedCompareExchangePointer ((gpointer *)&mon->owner, (gpointer)id, 0) == 0)) {
563 g_assert (mon->nest == 1);
564 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_DONE);
569 /* If the object is currently locked by this thread... */
570 if (mon->owner == id) {
572 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_DONE);
576 /* We need to make sure there's a semaphore handle (creating it if
577 * necessary), and block on it
579 if (mon->entry_sem == NULL) {
580 /* Create the semaphore */
581 sem = CreateSemaphore (NULL, 0, 0x7fffffff, NULL);
582 g_assert (sem != NULL);
583 if (InterlockedCompareExchangePointer ((gpointer*)&mon->entry_sem, sem, NULL) != NULL) {
584 /* Someone else just put a handle here */
589 /* If we need to time out, record a timestamp and adjust ms,
590 * because WaitForSingleObject doesn't tell us how long it
593 * Don't block forever here, because theres a chance the owner
594 * thread released the lock while we were creating the
595 * semaphore: we would not get the wakeup. Using the event
596 * handle technique from pulse/wait would involve locking the
597 * lock struct and therefore slowing down the fast path.
599 if (ms != INFINITE) {
600 then = mono_msec_ticks ();
610 InterlockedIncrement (&mon->entry_count);
612 mono_perfcounters->thread_queue_len++;
613 mono_perfcounters->thread_queue_max++;
614 thread = mono_thread_internal_current ();
616 mono_thread_set_state (thread, ThreadState_WaitSleepJoin);
619 * We pass TRUE instead of allow_interruption since we have to check for the
620 * StopRequested case below.
622 ret = WaitForSingleObjectEx (mon->entry_sem, waitms, TRUE);
624 mono_thread_clr_state (thread, ThreadState_WaitSleepJoin);
626 InterlockedDecrement (&mon->entry_count);
627 mono_perfcounters->thread_queue_len--;
629 if (ms != INFINITE) {
630 now = mono_msec_ticks ();
633 /* The counter must have wrapped around */
634 LOCK_DEBUG (g_message ("%s: wrapped around! now=0x%x then=0x%x", __func__, now, then));
636 now += (0xffffffff - then);
639 LOCK_DEBUG (g_message ("%s: wrap rejig: now=0x%x then=0x%x delta=0x%x", __func__, now, then, now-then));
649 if ((ret == WAIT_TIMEOUT || (ret == WAIT_IO_COMPLETION && !allow_interruption)) && ms > 0) {
651 goto retry_contended;
654 if (ret == WAIT_TIMEOUT || (ret == WAIT_IO_COMPLETION && !allow_interruption)) {
655 if (ret == WAIT_IO_COMPLETION && (mono_thread_test_state (mono_thread_internal_current (), (ThreadState_StopRequested|ThreadState_SuspendRequested)))) {
657 * We have to obey a stop/suspend request even if
658 * allow_interruption is FALSE to avoid hangs at shutdown.
660 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_FAIL);
663 /* Infinite wait, so just try again */
664 goto retry_contended;
668 if (ret == WAIT_OBJECT_0) {
669 /* retry from the top */
670 goto retry_contended;
673 /* We must have timed out */
674 LOCK_DEBUG (g_message ("%s: (%d) timed out waiting, returning FALSE", __func__, id));
676 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_FAIL);
678 if (ret == WAIT_IO_COMPLETION)
685 mono_monitor_enter (MonoObject *obj)
687 return mono_monitor_try_enter_internal (obj, INFINITE, FALSE) == 1;
691 mono_monitor_try_enter (MonoObject *obj, guint32 ms)
693 return mono_monitor_try_enter_internal (obj, ms, FALSE) == 1;
697 mono_monitor_exit (MonoObject *obj)
699 MonoThreadsSync *mon;
702 LOCK_DEBUG (g_message ("%s: (%d) Unlocking %p", __func__, GetCurrentThreadId (), obj));
704 if (G_UNLIKELY (!obj)) {
705 mono_raise_exception (mono_get_exception_argument_null ("obj"));
709 mon = obj->synchronisation;
711 #ifdef HAVE_MOVING_COLLECTOR
715 if (lw.lock_word & LOCK_WORD_THIN_HASH)
717 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
721 if (G_UNLIKELY (mon == NULL)) {
722 /* No one ever used Enter. Just ignore the Exit request as MS does */
725 if (G_UNLIKELY (mon->owner != GetCurrentThreadId ())) {
729 nest = mon->nest - 1;
731 LOCK_DEBUG (g_message ("%s: (%d) Object %p is now unlocked", __func__, GetCurrentThreadId (), obj));
733 /* object is now unlocked, leave nest==1 so we don't
734 * need to set it when the lock is reacquired
738 /* Do the wakeup stuff. It's possible that the last
739 * blocking thread gave up waiting just before we
740 * release the semaphore resulting in a futile wakeup
741 * next time there's contention for this object, but
742 * it means we don't have to waste time locking the
745 if (mon->entry_count > 0) {
746 ReleaseSemaphore (mon->entry_sem, 1, NULL);
749 LOCK_DEBUG (g_message ("%s: (%d) Object %p is now locked %d times", __func__, GetCurrentThreadId (), obj, nest));
755 mono_monitor_get_object_monitor_weak_link (MonoObject *object)
758 MonoThreadsSync *sync = NULL;
760 lw.sync = object->synchronisation;
761 if (lw.lock_word & LOCK_WORD_FAT_HASH) {
762 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
764 } else if (!(lw.lock_word & LOCK_WORD_THIN_HASH)) {
768 if (sync && sync->data)
774 emit_obj_syncp_check (MonoMethodBuilder *mb, int syncp_loc, int *obj_null_branch, int *syncp_true_false_branch,
775 gboolean branch_on_true)
782 mono_mb_emit_byte (mb, CEE_LDARG_0);
783 *obj_null_branch = mono_mb_emit_short_branch (mb, CEE_BRFALSE_S);
788 ldc.i4 G_STRUCT_OFFSET(MonoObject, synchronisation) objp off
793 brtrue/false.s syncp_true_false
796 mono_mb_emit_byte (mb, CEE_LDARG_0);
797 mono_mb_emit_byte (mb, CEE_CONV_I);
798 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoObject, synchronisation));
799 mono_mb_emit_byte (mb, CEE_ADD);
800 mono_mb_emit_byte (mb, CEE_LDIND_I);
801 mono_mb_emit_stloc (mb, syncp_loc);
802 mono_mb_emit_ldloc (mb, syncp_loc);
803 *syncp_true_false_branch = mono_mb_emit_short_branch (mb, branch_on_true ? CEE_BRTRUE_S : CEE_BRFALSE_S);
807 mono_monitor_get_fast_enter_method (MonoMethod *monitor_enter_method)
809 static MonoMethod *fast_monitor_enter;
810 static MonoMethod *compare_exchange_method;
812 MonoMethodBuilder *mb;
813 int obj_null_branch, syncp_null_branch, has_owner_branch, other_owner_branch, tid_branch;
814 int tid_loc, syncp_loc, owner_loc;
815 int thread_tls_offset;
817 #ifdef HAVE_MOVING_COLLECTOR
821 thread_tls_offset = mono_thread_get_tls_offset ();
822 if (thread_tls_offset == -1)
825 if (fast_monitor_enter)
826 return fast_monitor_enter;
828 if (!compare_exchange_method) {
829 MonoMethodDesc *desc;
832 desc = mono_method_desc_new ("Interlocked:CompareExchange(intptr&,intptr,intptr)", FALSE);
833 class = mono_class_from_name (mono_defaults.corlib, "System.Threading", "Interlocked");
834 compare_exchange_method = mono_method_desc_search_in_class (desc, class);
835 mono_method_desc_free (desc);
837 if (!compare_exchange_method)
841 mb = mono_mb_new (mono_defaults.monitor_class, "FastMonitorEnter", MONO_WRAPPER_UNKNOWN);
843 mb->method->slot = -1;
844 mb->method->flags = METHOD_ATTRIBUTE_PUBLIC | METHOD_ATTRIBUTE_STATIC |
845 METHOD_ATTRIBUTE_HIDE_BY_SIG | METHOD_ATTRIBUTE_FINAL;
847 tid_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
848 syncp_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
849 owner_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
851 emit_obj_syncp_check (mb, syncp_loc, &obj_null_branch, &syncp_null_branch, FALSE);
854 mono. tls thread_tls_offset threadp
855 ldc.i4 G_STRUCT_OFFSET(MonoThread, tid) threadp off
860 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
868 mono_mb_emit_byte (mb, MONO_CUSTOM_PREFIX);
869 mono_mb_emit_byte (mb, CEE_MONO_TLS);
870 mono_mb_emit_i4 (mb, thread_tls_offset);
871 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoInternalThread, tid));
872 mono_mb_emit_byte (mb, CEE_ADD);
873 mono_mb_emit_byte (mb, CEE_LDIND_I);
874 mono_mb_emit_stloc (mb, tid_loc);
875 mono_mb_emit_ldloc (mb, syncp_loc);
876 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
877 mono_mb_emit_byte (mb, CEE_ADD);
878 mono_mb_emit_byte (mb, CEE_LDIND_I);
879 mono_mb_emit_stloc (mb, owner_loc);
880 mono_mb_emit_ldloc (mb, owner_loc);
881 tid_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
885 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
888 ldc.i4 0 &owner tid 0
889 call System.Threading.Interlocked.CompareExchange oldowner
894 mono_mb_emit_ldloc (mb, syncp_loc);
895 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
896 mono_mb_emit_byte (mb, CEE_ADD);
897 mono_mb_emit_ldloc (mb, tid_loc);
898 mono_mb_emit_byte (mb, CEE_LDC_I4_0);
899 mono_mb_emit_managed_call (mb, compare_exchange_method, NULL);
900 has_owner_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
901 mono_mb_emit_byte (mb, CEE_RET);
909 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, nest) syncp off
913 ldc.i4 1 &nest nest 1
919 mono_mb_patch_short_branch (mb, tid_branch);
920 mono_mb_emit_ldloc (mb, owner_loc);
921 mono_mb_emit_ldloc (mb, tid_loc);
922 other_owner_branch = mono_mb_emit_short_branch (mb, CEE_BNE_UN_S);
923 mono_mb_emit_ldloc (mb, syncp_loc);
924 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, nest));
925 mono_mb_emit_byte (mb, CEE_ADD);
926 mono_mb_emit_byte (mb, CEE_DUP);
927 mono_mb_emit_byte (mb, CEE_LDIND_I4);
928 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
929 mono_mb_emit_byte (mb, CEE_ADD);
930 mono_mb_emit_byte (mb, CEE_STIND_I4);
931 mono_mb_emit_byte (mb, CEE_RET);
934 obj_null, syncp_null, has_owner, other_owner:
936 call System.Threading.Monitor.Enter
940 mono_mb_patch_short_branch (mb, obj_null_branch);
941 mono_mb_patch_short_branch (mb, syncp_null_branch);
942 mono_mb_patch_short_branch (mb, has_owner_branch);
943 mono_mb_patch_short_branch (mb, other_owner_branch);
944 mono_mb_emit_byte (mb, CEE_LDARG_0);
945 mono_mb_emit_managed_call (mb, monitor_enter_method, NULL);
946 mono_mb_emit_byte (mb, CEE_RET);
948 fast_monitor_enter = mono_mb_create_method (mb, mono_signature_no_pinvoke (monitor_enter_method), 5);
951 return fast_monitor_enter;
955 mono_monitor_get_fast_exit_method (MonoMethod *monitor_exit_method)
957 static MonoMethod *fast_monitor_exit;
959 MonoMethodBuilder *mb;
960 int obj_null_branch, has_waiting_branch, has_syncp_branch, owned_branch, nested_branch;
961 int thread_tls_offset;
964 #ifdef HAVE_MOVING_COLLECTOR
968 thread_tls_offset = mono_thread_get_tls_offset ();
969 if (thread_tls_offset == -1)
972 if (fast_monitor_exit)
973 return fast_monitor_exit;
975 mb = mono_mb_new (mono_defaults.monitor_class, "FastMonitorExit", MONO_WRAPPER_UNKNOWN);
977 mb->method->slot = -1;
978 mb->method->flags = METHOD_ATTRIBUTE_PUBLIC | METHOD_ATTRIBUTE_STATIC |
979 METHOD_ATTRIBUTE_HIDE_BY_SIG | METHOD_ATTRIBUTE_FINAL;
981 syncp_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
983 emit_obj_syncp_check (mb, syncp_loc, &obj_null_branch, &has_syncp_branch, TRUE);
989 mono_mb_emit_byte (mb, CEE_RET);
994 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
997 mono. tls thread_tls_offset owner threadp
998 ldc.i4 G_STRUCT_OFFSET(MonoThread, tid) owner threadp off
1004 mono_mb_patch_short_branch (mb, has_syncp_branch);
1005 mono_mb_emit_ldloc (mb, syncp_loc);
1006 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
1007 mono_mb_emit_byte (mb, CEE_ADD);
1008 mono_mb_emit_byte (mb, CEE_LDIND_I);
1009 mono_mb_emit_byte (mb, MONO_CUSTOM_PREFIX);
1010 mono_mb_emit_byte (mb, CEE_MONO_TLS);
1011 mono_mb_emit_i4 (mb, thread_tls_offset);
1012 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoInternalThread, tid));
1013 mono_mb_emit_byte (mb, CEE_ADD);
1014 mono_mb_emit_byte (mb, CEE_LDIND_I);
1015 owned_branch = mono_mb_emit_short_branch (mb, CEE_BEQ_S);
1021 mono_mb_emit_byte (mb, CEE_RET);
1026 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, nest) syncp off
1031 ldc.i4 1 &nest nest nest 1
1032 bgt.un.s nested &nest nest
1035 mono_mb_patch_short_branch (mb, owned_branch);
1036 mono_mb_emit_ldloc (mb, syncp_loc);
1037 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, nest));
1038 mono_mb_emit_byte (mb, CEE_ADD);
1039 mono_mb_emit_byte (mb, CEE_DUP);
1040 mono_mb_emit_byte (mb, CEE_LDIND_I4);
1041 mono_mb_emit_byte (mb, CEE_DUP);
1042 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
1043 nested_branch = mono_mb_emit_short_branch (mb, CEE_BGT_UN_S);
1049 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, entry_count) syncp off
1052 brtrue.s has_waiting
1055 mono_mb_emit_byte (mb, CEE_POP);
1056 mono_mb_emit_byte (mb, CEE_POP);
1057 mono_mb_emit_ldloc (mb, syncp_loc);
1058 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, entry_count));
1059 mono_mb_emit_byte (mb, CEE_ADD);
1060 mono_mb_emit_byte (mb, CEE_LDIND_I4);
1061 has_waiting_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
1065 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
1072 mono_mb_emit_ldloc (mb, syncp_loc);
1073 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
1074 mono_mb_emit_byte (mb, CEE_ADD);
1075 mono_mb_emit_byte (mb, CEE_LDNULL);
1076 mono_mb_emit_byte (mb, CEE_STIND_I);
1077 mono_mb_emit_byte (mb, CEE_RET);
1081 ldc.i4 1 &nest nest 1
1087 mono_mb_patch_short_branch (mb, nested_branch);
1088 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
1089 mono_mb_emit_byte (mb, CEE_SUB);
1090 mono_mb_emit_byte (mb, CEE_STIND_I4);
1091 mono_mb_emit_byte (mb, CEE_RET);
1094 obj_null, has_waiting:
1096 call System.Threading.Monitor.Exit
1100 mono_mb_patch_short_branch (mb, obj_null_branch);
1101 mono_mb_patch_short_branch (mb, has_waiting_branch);
1102 mono_mb_emit_byte (mb, CEE_LDARG_0);
1103 mono_mb_emit_managed_call (mb, monitor_exit_method, NULL);
1104 mono_mb_emit_byte (mb, CEE_RET);
1106 fast_monitor_exit = mono_mb_create_method (mb, mono_signature_no_pinvoke (monitor_exit_method), 5);
1109 return fast_monitor_exit;
1113 mono_monitor_get_fast_path (MonoMethod *enter_or_exit)
1115 if (strcmp (enter_or_exit->name, "Enter") == 0)
1116 return mono_monitor_get_fast_enter_method (enter_or_exit);
1117 if (strcmp (enter_or_exit->name, "Exit") == 0)
1118 return mono_monitor_get_fast_exit_method (enter_or_exit);
1119 g_assert_not_reached ();
1124 * mono_monitor_threads_sync_member_offset:
1125 * @owner_offset: returns size and offset of the "owner" member
1126 * @nest_offset: returns size and offset of the "nest" member
1127 * @entry_count_offset: returns size and offset of the "entry_count" member
1129 * Returns the offsets and sizes of three members of the
1130 * MonoThreadsSync struct. The Monitor ASM fastpaths need this.
1133 mono_monitor_threads_sync_members_offset (int *owner_offset, int *nest_offset, int *entry_count_offset)
1137 #define ENCODE_OFF_SIZE(o,s) (((o) << 8) | ((s) & 0xff))
1139 *owner_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, owner), sizeof (ts.owner));
1140 *nest_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, nest), sizeof (ts.nest));
1141 *entry_count_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, entry_count), sizeof (ts.entry_count));
1145 ves_icall_System_Threading_Monitor_Monitor_try_enter (MonoObject *obj, guint32 ms)
1150 res = mono_monitor_try_enter_internal (obj, ms, TRUE);
1152 mono_thread_interruption_checkpoint ();
1153 } while (res == -1);
1159 ves_icall_System_Threading_Monitor_Monitor_test_owner (MonoObject *obj)
1161 MonoThreadsSync *mon;
1163 LOCK_DEBUG (g_message ("%s: Testing if %p is owned by thread %d", __func__, obj, GetCurrentThreadId()));
1165 mon = obj->synchronisation;
1166 #ifdef HAVE_MOVING_COLLECTOR
1170 if (lw.lock_word & LOCK_WORD_THIN_HASH)
1172 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1180 if(mon->owner==GetCurrentThreadId ()) {
1188 ves_icall_System_Threading_Monitor_Monitor_test_synchronised (MonoObject *obj)
1190 MonoThreadsSync *mon;
1192 LOCK_DEBUG (g_message("%s: (%d) Testing if %p is owned by any thread", __func__, GetCurrentThreadId (), obj));
1194 mon = obj->synchronisation;
1195 #ifdef HAVE_MOVING_COLLECTOR
1199 if (lw.lock_word & LOCK_WORD_THIN_HASH)
1201 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1209 if (mon->owner != 0) {
1216 /* All wait list manipulation in the pulse, pulseall and wait
1217 * functions happens while the monitor lock is held, so we don't need
1218 * any extra struct locking
1222 ves_icall_System_Threading_Monitor_Monitor_pulse (MonoObject *obj)
1224 MonoThreadsSync *mon;
1226 LOCK_DEBUG (g_message ("%s: (%d) Pulsing %p", __func__, GetCurrentThreadId (), obj));
1228 mon = obj->synchronisation;
1229 #ifdef HAVE_MOVING_COLLECTOR
1233 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1234 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1237 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1242 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1245 if (mon->owner != GetCurrentThreadId ()) {
1246 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1250 LOCK_DEBUG (g_message ("%s: (%d) %d threads waiting", __func__, GetCurrentThreadId (), g_slist_length (mon->wait_list)));
1252 if (mon->wait_list != NULL) {
1253 LOCK_DEBUG (g_message ("%s: (%d) signalling and dequeuing handle %p", __func__, GetCurrentThreadId (), mon->wait_list->data));
1255 SetEvent (mon->wait_list->data);
1256 mon->wait_list = g_slist_remove (mon->wait_list, mon->wait_list->data);
1261 ves_icall_System_Threading_Monitor_Monitor_pulse_all (MonoObject *obj)
1263 MonoThreadsSync *mon;
1265 LOCK_DEBUG (g_message("%s: (%d) Pulsing all %p", __func__, GetCurrentThreadId (), obj));
1267 mon = obj->synchronisation;
1268 #ifdef HAVE_MOVING_COLLECTOR
1272 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1273 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1276 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1281 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1284 if (mon->owner != GetCurrentThreadId ()) {
1285 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1289 LOCK_DEBUG (g_message ("%s: (%d) %d threads waiting", __func__, GetCurrentThreadId (), g_slist_length (mon->wait_list)));
1291 while (mon->wait_list != NULL) {
1292 LOCK_DEBUG (g_message ("%s: (%d) signalling and dequeuing handle %p", __func__, GetCurrentThreadId (), mon->wait_list->data));
1294 SetEvent (mon->wait_list->data);
1295 mon->wait_list = g_slist_remove (mon->wait_list, mon->wait_list->data);
1300 ves_icall_System_Threading_Monitor_Monitor_wait (MonoObject *obj, guint32 ms)
1302 MonoThreadsSync *mon;
1306 gboolean success = FALSE;
1308 MonoInternalThread *thread = mono_thread_internal_current ();
1310 LOCK_DEBUG (g_message ("%s: (%d) Trying to wait for %p with timeout %dms", __func__, GetCurrentThreadId (), obj, ms));
1312 mon = obj->synchronisation;
1313 #ifdef HAVE_MOVING_COLLECTOR
1317 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1318 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1321 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1326 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1329 if (mon->owner != GetCurrentThreadId ()) {
1330 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1334 /* Do this WaitSleepJoin check before creating the event handle */
1335 mono_thread_current_check_pending_interrupt ();
1337 event = CreateEvent (NULL, FALSE, FALSE, NULL);
1338 if (event == NULL) {
1339 mono_raise_exception (mono_get_exception_synchronization_lock ("Failed to set up wait event"));
1343 LOCK_DEBUG (g_message ("%s: (%d) queuing handle %p", __func__, GetCurrentThreadId (), event));
1345 mono_thread_current_check_pending_interrupt ();
1347 mono_thread_set_state (thread, ThreadState_WaitSleepJoin);
1349 mon->wait_list = g_slist_append (mon->wait_list, event);
1351 /* Save the nest count, and release the lock */
1354 mono_monitor_exit (obj);
1356 LOCK_DEBUG (g_message ("%s: (%d) Unlocked %p lock %p", __func__, GetCurrentThreadId (), obj, mon));
1358 /* There's no race between unlocking mon and waiting for the
1359 * event, because auto reset events are sticky, and this event
1360 * is private to this thread. Therefore even if the event was
1361 * signalled before we wait, we still succeed.
1363 ret = WaitForSingleObjectEx (event, ms, TRUE);
1365 /* Reset the thread state fairly early, so we don't have to worry
1366 * about the monitor error checking
1368 mono_thread_clr_state (thread, ThreadState_WaitSleepJoin);
1370 if (mono_thread_interruption_requested ()) {
1372 * Can't remove the event from wait_list, since the monitor is not locked by
1373 * us. So leave it there, mon_new () will delete it when the mon structure
1374 * is placed on the free list.
1375 * FIXME: The caller expects to hold the lock after the wait returns, but it
1376 * doesn't happen in this case:
1377 * http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=97268
1382 /* Regain the lock with the previous nest count */
1384 regain = mono_monitor_try_enter_internal (obj, INFINITE, TRUE);
1386 mono_thread_interruption_checkpoint ();
1387 } while (regain == -1);
1390 /* Something went wrong, so throw a
1391 * SynchronizationLockException
1393 CloseHandle (event);
1394 mono_raise_exception (mono_get_exception_synchronization_lock ("Failed to regain lock"));
1400 LOCK_DEBUG (g_message ("%s: (%d) Regained %p lock %p", __func__, GetCurrentThreadId (), obj, mon));
1402 if (ret == WAIT_TIMEOUT) {
1403 /* Poll the event again, just in case it was signalled
1404 * while we were trying to regain the monitor lock
1406 ret = WaitForSingleObjectEx (event, 0, FALSE);
1409 /* Pulse will have popped our event from the queue if it signalled
1410 * us, so we only do it here if the wait timed out.
1412 * This avoids a race condition where the thread holding the
1413 * lock can Pulse several times before the WaitForSingleObject
1414 * returns. If we popped the queue here then this event might
1415 * be signalled more than once, thereby starving another
1419 if (ret == WAIT_OBJECT_0) {
1420 LOCK_DEBUG (g_message ("%s: (%d) Success", __func__, GetCurrentThreadId ()));
1423 LOCK_DEBUG (g_message ("%s: (%d) Wait failed, dequeuing handle %p", __func__, GetCurrentThreadId (), event));
1424 /* No pulse, so we have to remove ourself from the
1427 mon->wait_list = g_slist_remove (mon->wait_list, event);
1429 CloseHandle (event);