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;
107 #ifndef PLATFORM_WIN32
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 /*DeleteCriticalSection (&monitor_mutex);*/
132 * mono_monitor_init_tls:
134 * Setup TLS variables used by the monitor code for the current thread.
137 mono_monitor_init_tls (void)
139 #if !defined(PLATFORM_WIN32) && defined(HAVE_KW_THREAD)
140 tls_pthread_self = pthread_self ();
145 monitor_is_on_freelist (MonoThreadsSync *mon)
147 MonitorArray *marray;
148 for (marray = monitor_allocated; marray; marray = marray->next) {
149 if (mon >= marray->monitors && mon < &marray->monitors [marray->num_monitors])
159 * Print a report on stdout of the managed locks currently held by
160 * threads. If @include_untaken is specified, list also inflated locks
162 * This is supposed to be used in debuggers like gdb.
165 mono_locks_dump (gboolean include_untaken)
168 int used = 0, on_freelist = 0, to_recycle = 0, total = 0, num_arrays = 0;
169 MonoThreadsSync *mon;
170 MonitorArray *marray;
171 for (mon = monitor_freelist; mon; mon = mon->data)
173 for (marray = monitor_allocated; marray; marray = marray->next) {
174 total += marray->num_monitors;
176 for (i = 0; i < marray->num_monitors; ++i) {
177 mon = &marray->monitors [i];
178 if (mon->data == NULL) {
179 if (i < marray->num_monitors - 1)
182 if (!monitor_is_on_freelist (mon->data)) {
183 MonoObject *holder = mono_gc_weak_link_get (&mon->data);
185 g_print ("Lock %p in object %p held by thread %p, nest level: %d\n",
186 mon, holder, (void*)mon->owner, mon->nest);
188 g_print ("\tWaiting on semaphore %p: %d\n", mon->entry_sem, mon->entry_count);
189 } else if (include_untaken) {
190 g_print ("Lock %p in object %p untaken\n", mon, holder);
197 g_print ("Total locks (in %d array(s)): %d, used: %d, on freelist: %d, to recycle: %d\n",
198 num_arrays, total, used, on_freelist, to_recycle);
201 /* LOCKING: this is called with monitor_mutex held */
203 mon_finalize (MonoThreadsSync *mon)
205 LOCK_DEBUG (g_message ("%s: Finalizing sync %p", __func__, mon));
207 if (mon->entry_sem != NULL) {
208 CloseHandle (mon->entry_sem);
209 mon->entry_sem = NULL;
211 /* If this isn't empty then something is seriously broken - it
212 * means a thread is still waiting on the object that owned
213 * this lock, but the object has been finalized.
215 g_assert (mon->wait_list == NULL);
217 mon->entry_count = 0;
218 /* owner and nest are set in mon_new, no need to zero them out */
220 mon->data = monitor_freelist;
221 monitor_freelist = mon;
222 mono_perfcounters->gc_sync_blocks--;
225 /* LOCKING: this is called with monitor_mutex held */
226 static MonoThreadsSync *
229 MonoThreadsSync *new;
231 if (!monitor_freelist) {
232 MonitorArray *marray;
234 /* see if any sync block has been collected */
236 for (marray = monitor_allocated; marray; marray = marray->next) {
237 for (i = 0; i < marray->num_monitors; ++i) {
238 if (marray->monitors [i].data == NULL) {
239 new = &marray->monitors [i];
240 new->data = monitor_freelist;
241 monitor_freelist = new;
244 /* small perf tweak to avoid scanning all the blocks */
248 /* need to allocate a new array of monitors */
249 if (!monitor_freelist) {
251 LOCK_DEBUG (g_message ("%s: allocating more monitors: %d", __func__, array_size));
252 marray = g_malloc0 (sizeof (MonoArray) + array_size * sizeof (MonoThreadsSync));
253 marray->num_monitors = array_size;
255 /* link into the freelist */
256 for (i = 0; i < marray->num_monitors - 1; ++i) {
257 marray->monitors [i].data = &marray->monitors [i + 1];
259 marray->monitors [i].data = NULL; /* the last one */
260 monitor_freelist = &marray->monitors [0];
261 /* we happend the marray instead of prepending so that
262 * the collecting loop above will need to scan smaller arrays first
264 if (!monitor_allocated) {
265 monitor_allocated = marray;
267 last = monitor_allocated;
275 new = monitor_freelist;
276 monitor_freelist = new->data;
281 mono_perfcounters->gc_sync_blocks++;
286 * Format of the lock word:
287 * thinhash | fathash | data
289 * thinhash is the lower bit: if set data is the shifted hashcode of the object.
290 * fathash is another bit: if set the hash code is stored in the MonoThreadsSync
291 * struct pointed to by data
292 * if neither bit is set and data is non-NULL, data is a MonoThreadsSync
296 MonoThreadsSync *sync;
300 LOCK_WORD_THIN_HASH = 1,
301 LOCK_WORD_FAT_HASH = 1 << 1,
302 LOCK_WORD_BITS_MASK = 0x3,
303 LOCK_WORD_HASH_SHIFT = 2
306 #define MONO_OBJECT_ALIGNMENT_SHIFT 3
312 * Calculate a hash code for @obj that is constant while @obj is alive.
315 mono_object_hash (MonoObject* obj)
317 #ifdef HAVE_MOVING_COLLECTOR
322 lw.sync = obj->synchronisation;
323 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
324 /*g_print ("fast thin hash %d for obj %p store\n", (unsigned int)lw.lock_word >> LOCK_WORD_HASH_SHIFT, obj);*/
325 return (unsigned int)lw.lock_word >> LOCK_WORD_HASH_SHIFT;
327 if (lw.lock_word & LOCK_WORD_FAT_HASH) {
328 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
329 /*g_print ("fast fat hash %d for obj %p store\n", lw.sync->hash_code, obj);*/
330 return lw.sync->hash_code;
333 * while we are inside this function, the GC will keep this object pinned,
334 * since we are in the unmanaged stack. Thanks to this and to the hash
335 * function that depends only on the address, we can ignore the races if
336 * another thread computes the hash at the same time, because it'll end up
337 * with the same value.
339 hash = (GPOINTER_TO_UINT (obj) >> MONO_OBJECT_ALIGNMENT_SHIFT) * 2654435761u;
340 /* clear the top bits as they can be discarded */
341 hash &= ~(LOCK_WORD_BITS_MASK << 30);
342 /* no hash flags were set, so it must be a MonoThreadsSync pointer if not NULL */
344 lw.sync->hash_code = hash;
345 /*g_print ("storing hash code %d for obj %p in sync %p\n", hash, obj, lw.sync);*/
346 lw.lock_word |= LOCK_WORD_FAT_HASH;
347 /* this is safe since we don't deflate locks */
348 obj->synchronisation = lw.sync;
350 /*g_print ("storing thin hash code %d for obj %p\n", hash, obj);*/
351 lw.lock_word = LOCK_WORD_THIN_HASH | (hash << LOCK_WORD_HASH_SHIFT);
352 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, NULL) == NULL)
354 /*g_print ("failed store\n");*/
355 /* someone set the hash flag or someone inflated the object */
356 lw.sync = obj->synchronisation;
357 if (lw.lock_word & LOCK_WORD_THIN_HASH)
359 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
360 lw.sync->hash_code = hash;
361 lw.lock_word |= LOCK_WORD_FAT_HASH;
362 /* this is safe since we don't deflate locks */
363 obj->synchronisation = lw.sync;
368 * Wang's address-based hash function:
369 * http://www.concentric.net/~Ttwang/tech/addrhash.htm
371 return (GPOINTER_TO_UINT (obj) >> MONO_OBJECT_ALIGNMENT_SHIFT) * 2654435761u;
375 /* If allow_interruption==TRUE, the method will be interrumped if abort or suspend
376 * is requested. In this case it returns -1.
379 mono_monitor_try_enter_internal (MonoObject *obj, guint32 ms, gboolean allow_interruption)
381 MonoThreadsSync *mon;
382 gsize id = GetCurrentThreadId ();
384 guint32 then = 0, now, delta;
389 LOCK_DEBUG (g_message("%s: (%d) Trying to lock object %p (%d ms)", __func__, id, obj, ms));
391 if (G_UNLIKELY (!obj)) {
392 mono_raise_exception (mono_get_exception_argument_null ("obj"));
397 mon = obj->synchronisation;
399 /* If the object has never been locked... */
400 if (G_UNLIKELY (mon == NULL)) {
401 mono_monitor_allocator_lock ();
403 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, mon, NULL) == NULL) {
404 mono_gc_weak_link_add (&mon->data, obj, FALSE);
405 mono_monitor_allocator_unlock ();
406 /* Successfully locked */
409 #ifdef HAVE_MOVING_COLLECTOR
411 lw.sync = obj->synchronisation;
412 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
413 MonoThreadsSync *oldlw = lw.sync;
414 /* move the already calculated hash */
415 mon->hash_code = lw.lock_word >> LOCK_WORD_HASH_SHIFT;
417 lw.lock_word |= LOCK_WORD_FAT_HASH;
418 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, oldlw) == oldlw) {
419 mono_gc_weak_link_add (&mon->data, obj, FALSE);
420 mono_monitor_allocator_unlock ();
421 /* Successfully locked */
425 mono_monitor_allocator_unlock ();
428 } else if (lw.lock_word & LOCK_WORD_FAT_HASH) {
430 mono_monitor_allocator_unlock ();
431 /* get the old lock without the fat hash bit */
432 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
436 mono_monitor_allocator_unlock ();
437 mon = obj->synchronisation;
441 mono_monitor_allocator_unlock ();
442 mon = obj->synchronisation;
446 #ifdef HAVE_MOVING_COLLECTOR
449 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
450 MonoThreadsSync *oldlw = lw.sync;
451 mono_monitor_allocator_lock ();
453 /* move the already calculated hash */
454 mon->hash_code = lw.lock_word >> LOCK_WORD_HASH_SHIFT;
456 lw.lock_word |= LOCK_WORD_FAT_HASH;
457 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, oldlw) == oldlw) {
458 mono_gc_weak_link_add (&mon->data, obj, TRUE);
459 mono_monitor_allocator_unlock ();
460 /* Successfully locked */
464 mono_monitor_allocator_unlock ();
471 #ifdef HAVE_MOVING_COLLECTOR
475 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
480 /* If the object has previously been locked but isn't now... */
482 /* This case differs from Dice's case 3 because we don't
483 * deflate locks or cache unused lock records
485 if (G_LIKELY (mon->owner == 0)) {
486 /* Try to install our ID in the owner field, nest
487 * should have been left at 1 by the previous unlock
490 if (G_LIKELY (InterlockedCompareExchangePointer ((gpointer *)&mon->owner, (gpointer)id, 0) == 0)) {
492 g_assert (mon->nest == 1);
500 /* If the object is currently locked by this thread... */
501 if (mon->owner == id) {
506 /* The object must be locked by someone else... */
507 mono_perfcounters->thread_contentions++;
509 /* If ms is 0 we don't block, but just fail straight away */
511 LOCK_DEBUG (g_message ("%s: (%d) timed out, returning FALSE", __func__, id));
515 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_CONTENTION);
517 /* The slow path begins here. */
519 /* a small amount of duplicated code, but it allows us to insert the profiler
520 * callbacks without impacting the fast path: from here on we don't need to go back to the
521 * retry label, but to retry_contended. At this point mon is already installed in the object
524 /* This case differs from Dice's case 3 because we don't
525 * deflate locks or cache unused lock records
527 if (G_LIKELY (mon->owner == 0)) {
528 /* Try to install our ID in the owner field, nest
529 * should have been left at 1 by the previous unlock
532 if (G_LIKELY (InterlockedCompareExchangePointer ((gpointer *)&mon->owner, (gpointer)id, 0) == 0)) {
534 g_assert (mon->nest == 1);
535 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_DONE);
540 /* If the object is currently locked by this thread... */
541 if (mon->owner == id) {
543 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_DONE);
547 /* We need to make sure there's a semaphore handle (creating it if
548 * necessary), and block on it
550 if (mon->entry_sem == NULL) {
551 /* Create the semaphore */
552 sem = CreateSemaphore (NULL, 0, 0x7fffffff, NULL);
553 g_assert (sem != NULL);
554 if (InterlockedCompareExchangePointer ((gpointer*)&mon->entry_sem, sem, NULL) != NULL) {
555 /* Someone else just put a handle here */
560 /* If we need to time out, record a timestamp and adjust ms,
561 * because WaitForSingleObject doesn't tell us how long it
564 * Don't block forever here, because theres a chance the owner
565 * thread released the lock while we were creating the
566 * semaphore: we would not get the wakeup. Using the event
567 * handle technique from pulse/wait would involve locking the
568 * lock struct and therefore slowing down the fast path.
570 if (ms != INFINITE) {
571 then = mono_msec_ticks ();
581 InterlockedIncrement (&mon->entry_count);
583 mono_perfcounters->thread_queue_len++;
584 mono_perfcounters->thread_queue_max++;
585 thread = mono_thread_current ();
587 mono_thread_set_state (thread, ThreadState_WaitSleepJoin);
590 * We pass TRUE instead of allow_interruption since we have to check for the
591 * StopRequested case below.
593 ret = WaitForSingleObjectEx (mon->entry_sem, waitms, TRUE);
595 mono_thread_clr_state (thread, ThreadState_WaitSleepJoin);
597 InterlockedDecrement (&mon->entry_count);
598 mono_perfcounters->thread_queue_len--;
600 if (ms != INFINITE) {
601 now = mono_msec_ticks ();
604 /* The counter must have wrapped around */
605 LOCK_DEBUG (g_message ("%s: wrapped around! now=0x%x then=0x%x", __func__, now, then));
607 now += (0xffffffff - then);
610 LOCK_DEBUG (g_message ("%s: wrap rejig: now=0x%x then=0x%x delta=0x%x", __func__, now, then, now-then));
620 if ((ret == WAIT_TIMEOUT || (ret == WAIT_IO_COMPLETION && !allow_interruption)) && ms > 0) {
622 goto retry_contended;
625 if (ret == WAIT_TIMEOUT || (ret == WAIT_IO_COMPLETION && !allow_interruption)) {
626 if (ret == WAIT_IO_COMPLETION && (mono_thread_test_state (mono_thread_current (), (ThreadState_StopRequested|ThreadState_SuspendRequested)))) {
628 * We have to obey a stop/suspend request even if
629 * allow_interruption is FALSE to avoid hangs at shutdown.
631 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_FAIL);
634 /* Infinite wait, so just try again */
635 goto retry_contended;
639 if (ret == WAIT_OBJECT_0) {
640 /* retry from the top */
641 goto retry_contended;
644 /* We must have timed out */
645 LOCK_DEBUG (g_message ("%s: (%d) timed out waiting, returning FALSE", __func__, id));
647 mono_profiler_monitor_event (obj, MONO_PROFILER_MONITOR_FAIL);
649 if (ret == WAIT_IO_COMPLETION)
656 mono_monitor_enter (MonoObject *obj)
658 return mono_monitor_try_enter_internal (obj, INFINITE, FALSE) == 1;
662 mono_monitor_try_enter (MonoObject *obj, guint32 ms)
664 return mono_monitor_try_enter_internal (obj, ms, FALSE) == 1;
668 mono_monitor_exit (MonoObject *obj)
670 MonoThreadsSync *mon;
673 LOCK_DEBUG (g_message ("%s: (%d) Unlocking %p", __func__, GetCurrentThreadId (), obj));
675 if (G_UNLIKELY (!obj)) {
676 mono_raise_exception (mono_get_exception_argument_null ("obj"));
680 mon = obj->synchronisation;
682 #ifdef HAVE_MOVING_COLLECTOR
686 if (lw.lock_word & LOCK_WORD_THIN_HASH)
688 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
692 if (G_UNLIKELY (mon == NULL)) {
693 /* No one ever used Enter. Just ignore the Exit request as MS does */
696 if (G_UNLIKELY (mon->owner != GetCurrentThreadId ())) {
700 nest = mon->nest - 1;
702 LOCK_DEBUG (g_message ("%s: (%d) Object %p is now unlocked", __func__, GetCurrentThreadId (), obj));
704 /* object is now unlocked, leave nest==1 so we don't
705 * need to set it when the lock is reacquired
709 /* Do the wakeup stuff. It's possible that the last
710 * blocking thread gave up waiting just before we
711 * release the semaphore resulting in a futile wakeup
712 * next time there's contention for this object, but
713 * it means we don't have to waste time locking the
716 if (mon->entry_count > 0) {
717 ReleaseSemaphore (mon->entry_sem, 1, NULL);
720 LOCK_DEBUG (g_message ("%s: (%d) Object %p is now locked %d times", __func__, GetCurrentThreadId (), obj, nest));
726 mono_monitor_get_object_monitor_weak_link (MonoObject *object)
729 MonoThreadsSync *sync = NULL;
731 lw.sync = object->synchronisation;
732 if (lw.lock_word & LOCK_WORD_FAT_HASH) {
733 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
735 } else if (!(lw.lock_word & LOCK_WORD_THIN_HASH)) {
739 if (sync && sync->data)
745 emit_obj_syncp_check (MonoMethodBuilder *mb, int syncp_loc, int *obj_null_branch, int *syncp_true_false_branch,
746 gboolean branch_on_true)
753 mono_mb_emit_byte (mb, CEE_LDARG_0);
754 *obj_null_branch = mono_mb_emit_short_branch (mb, CEE_BRFALSE_S);
759 ldc.i4 G_STRUCT_OFFSET(MonoObject, synchronisation) objp off
764 brtrue/false.s syncp_true_false
767 mono_mb_emit_byte (mb, CEE_LDARG_0);
768 mono_mb_emit_byte (mb, CEE_CONV_I);
769 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoObject, synchronisation));
770 mono_mb_emit_byte (mb, CEE_ADD);
771 mono_mb_emit_byte (mb, CEE_LDIND_I);
772 mono_mb_emit_stloc (mb, syncp_loc);
773 mono_mb_emit_ldloc (mb, syncp_loc);
774 *syncp_true_false_branch = mono_mb_emit_short_branch (mb, branch_on_true ? CEE_BRTRUE_S : CEE_BRFALSE_S);
778 mono_monitor_get_fast_enter_method (MonoMethod *monitor_enter_method)
780 static MonoMethod *fast_monitor_enter;
781 static MonoMethod *compare_exchange_method;
783 MonoMethodBuilder *mb;
784 int obj_null_branch, syncp_null_branch, has_owner_branch, other_owner_branch, tid_branch;
785 int tid_loc, syncp_loc, owner_loc;
786 int thread_tls_offset;
788 #ifdef HAVE_MOVING_COLLECTOR
792 thread_tls_offset = mono_thread_get_tls_offset ();
793 if (thread_tls_offset == -1)
796 if (fast_monitor_enter)
797 return fast_monitor_enter;
799 if (!compare_exchange_method) {
800 MonoMethodDesc *desc;
803 desc = mono_method_desc_new ("Interlocked:CompareExchange(intptr&,intptr,intptr)", FALSE);
804 class = mono_class_from_name (mono_defaults.corlib, "System.Threading", "Interlocked");
805 compare_exchange_method = mono_method_desc_search_in_class (desc, class);
806 mono_method_desc_free (desc);
808 if (!compare_exchange_method)
812 mb = mono_mb_new (mono_defaults.monitor_class, "FastMonitorEnter", MONO_WRAPPER_UNKNOWN);
814 mb->method->slot = -1;
815 mb->method->flags = METHOD_ATTRIBUTE_PUBLIC | METHOD_ATTRIBUTE_STATIC |
816 METHOD_ATTRIBUTE_HIDE_BY_SIG | METHOD_ATTRIBUTE_FINAL;
818 tid_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
819 syncp_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
820 owner_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
822 emit_obj_syncp_check (mb, syncp_loc, &obj_null_branch, &syncp_null_branch, FALSE);
825 mono. tls thread_tls_offset threadp
826 ldc.i4 G_STRUCT_OFFSET(MonoThread, tid) threadp off
831 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
839 mono_mb_emit_byte (mb, MONO_CUSTOM_PREFIX);
840 mono_mb_emit_byte (mb, CEE_MONO_TLS);
841 mono_mb_emit_i4 (mb, thread_tls_offset);
842 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThread, tid));
843 mono_mb_emit_byte (mb, CEE_ADD);
844 mono_mb_emit_byte (mb, CEE_LDIND_I);
845 mono_mb_emit_stloc (mb, tid_loc);
846 mono_mb_emit_ldloc (mb, syncp_loc);
847 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
848 mono_mb_emit_byte (mb, CEE_ADD);
849 mono_mb_emit_byte (mb, CEE_LDIND_I);
850 mono_mb_emit_stloc (mb, owner_loc);
851 mono_mb_emit_ldloc (mb, owner_loc);
852 tid_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
856 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
859 ldc.i4 0 &owner tid 0
860 call System.Threading.Interlocked.CompareExchange oldowner
865 mono_mb_emit_ldloc (mb, syncp_loc);
866 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
867 mono_mb_emit_byte (mb, CEE_ADD);
868 mono_mb_emit_ldloc (mb, tid_loc);
869 mono_mb_emit_byte (mb, CEE_LDC_I4_0);
870 mono_mb_emit_managed_call (mb, compare_exchange_method, NULL);
871 has_owner_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
872 mono_mb_emit_byte (mb, CEE_RET);
880 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, nest) syncp off
884 ldc.i4 1 &nest nest 1
890 mono_mb_patch_short_branch (mb, tid_branch);
891 mono_mb_emit_ldloc (mb, owner_loc);
892 mono_mb_emit_ldloc (mb, tid_loc);
893 other_owner_branch = mono_mb_emit_short_branch (mb, CEE_BNE_UN_S);
894 mono_mb_emit_ldloc (mb, syncp_loc);
895 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, nest));
896 mono_mb_emit_byte (mb, CEE_ADD);
897 mono_mb_emit_byte (mb, CEE_DUP);
898 mono_mb_emit_byte (mb, CEE_LDIND_I4);
899 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
900 mono_mb_emit_byte (mb, CEE_ADD);
901 mono_mb_emit_byte (mb, CEE_STIND_I4);
902 mono_mb_emit_byte (mb, CEE_RET);
905 obj_null, syncp_null, has_owner, other_owner:
907 call System.Threading.Monitor.Enter
911 mono_mb_patch_short_branch (mb, obj_null_branch);
912 mono_mb_patch_short_branch (mb, syncp_null_branch);
913 mono_mb_patch_short_branch (mb, has_owner_branch);
914 mono_mb_patch_short_branch (mb, other_owner_branch);
915 mono_mb_emit_byte (mb, CEE_LDARG_0);
916 mono_mb_emit_managed_call (mb, monitor_enter_method, NULL);
917 mono_mb_emit_byte (mb, CEE_RET);
919 fast_monitor_enter = mono_mb_create_method (mb, mono_signature_no_pinvoke (monitor_enter_method), 5);
922 return fast_monitor_enter;
926 mono_monitor_get_fast_exit_method (MonoMethod *monitor_exit_method)
928 static MonoMethod *fast_monitor_exit;
930 MonoMethodBuilder *mb;
931 int obj_null_branch, has_waiting_branch, has_syncp_branch, owned_branch, nested_branch;
932 int thread_tls_offset;
935 #ifdef HAVE_MOVING_COLLECTOR
939 thread_tls_offset = mono_thread_get_tls_offset ();
940 if (thread_tls_offset == -1)
943 if (fast_monitor_exit)
944 return fast_monitor_exit;
946 mb = mono_mb_new (mono_defaults.monitor_class, "FastMonitorExit", MONO_WRAPPER_UNKNOWN);
948 mb->method->slot = -1;
949 mb->method->flags = METHOD_ATTRIBUTE_PUBLIC | METHOD_ATTRIBUTE_STATIC |
950 METHOD_ATTRIBUTE_HIDE_BY_SIG | METHOD_ATTRIBUTE_FINAL;
952 syncp_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
954 emit_obj_syncp_check (mb, syncp_loc, &obj_null_branch, &has_syncp_branch, TRUE);
960 mono_mb_emit_byte (mb, CEE_RET);
965 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
968 mono. tls thread_tls_offset owner threadp
969 ldc.i4 G_STRUCT_OFFSET(MonoThread, tid) owner threadp off
975 mono_mb_patch_short_branch (mb, has_syncp_branch);
976 mono_mb_emit_ldloc (mb, syncp_loc);
977 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
978 mono_mb_emit_byte (mb, CEE_ADD);
979 mono_mb_emit_byte (mb, CEE_LDIND_I);
980 mono_mb_emit_byte (mb, MONO_CUSTOM_PREFIX);
981 mono_mb_emit_byte (mb, CEE_MONO_TLS);
982 mono_mb_emit_i4 (mb, thread_tls_offset);
983 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThread, tid));
984 mono_mb_emit_byte (mb, CEE_ADD);
985 mono_mb_emit_byte (mb, CEE_LDIND_I);
986 owned_branch = mono_mb_emit_short_branch (mb, CEE_BEQ_S);
992 mono_mb_emit_byte (mb, CEE_RET);
997 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, nest) syncp off
1002 ldc.i4 1 &nest nest nest 1
1003 bgt.un.s nested &nest nest
1006 mono_mb_patch_short_branch (mb, owned_branch);
1007 mono_mb_emit_ldloc (mb, syncp_loc);
1008 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, nest));
1009 mono_mb_emit_byte (mb, CEE_ADD);
1010 mono_mb_emit_byte (mb, CEE_DUP);
1011 mono_mb_emit_byte (mb, CEE_LDIND_I4);
1012 mono_mb_emit_byte (mb, CEE_DUP);
1013 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
1014 nested_branch = mono_mb_emit_short_branch (mb, CEE_BGT_UN_S);
1020 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, entry_count) syncp off
1023 brtrue.s has_waiting
1026 mono_mb_emit_byte (mb, CEE_POP);
1027 mono_mb_emit_byte (mb, CEE_POP);
1028 mono_mb_emit_ldloc (mb, syncp_loc);
1029 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, entry_count));
1030 mono_mb_emit_byte (mb, CEE_ADD);
1031 mono_mb_emit_byte (mb, CEE_LDIND_I4);
1032 has_waiting_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
1036 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
1043 mono_mb_emit_ldloc (mb, syncp_loc);
1044 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
1045 mono_mb_emit_byte (mb, CEE_ADD);
1046 mono_mb_emit_byte (mb, CEE_LDNULL);
1047 mono_mb_emit_byte (mb, CEE_STIND_I);
1048 mono_mb_emit_byte (mb, CEE_RET);
1052 ldc.i4 1 &nest nest 1
1058 mono_mb_patch_short_branch (mb, nested_branch);
1059 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
1060 mono_mb_emit_byte (mb, CEE_SUB);
1061 mono_mb_emit_byte (mb, CEE_STIND_I4);
1062 mono_mb_emit_byte (mb, CEE_RET);
1065 obj_null, has_waiting:
1067 call System.Threading.Monitor.Exit
1071 mono_mb_patch_short_branch (mb, obj_null_branch);
1072 mono_mb_patch_short_branch (mb, has_waiting_branch);
1073 mono_mb_emit_byte (mb, CEE_LDARG_0);
1074 mono_mb_emit_managed_call (mb, monitor_exit_method, NULL);
1075 mono_mb_emit_byte (mb, CEE_RET);
1077 fast_monitor_exit = mono_mb_create_method (mb, mono_signature_no_pinvoke (monitor_exit_method), 5);
1080 return fast_monitor_exit;
1084 mono_monitor_get_fast_path (MonoMethod *enter_or_exit)
1086 if (strcmp (enter_or_exit->name, "Enter") == 0)
1087 return mono_monitor_get_fast_enter_method (enter_or_exit);
1088 if (strcmp (enter_or_exit->name, "Exit") == 0)
1089 return mono_monitor_get_fast_exit_method (enter_or_exit);
1090 g_assert_not_reached ();
1095 * mono_monitor_threads_sync_member_offset:
1096 * @owner_offset: returns size and offset of the "owner" member
1097 * @nest_offset: returns size and offset of the "nest" member
1098 * @entry_count_offset: returns size and offset of the "entry_count" member
1100 * Returns the offsets and sizes of three members of the
1101 * MonoThreadsSync struct. The Monitor ASM fastpaths need this.
1104 mono_monitor_threads_sync_members_offset (int *owner_offset, int *nest_offset, int *entry_count_offset)
1108 #define ENCODE_OFF_SIZE(o,s) (((o) << 8) | ((s) & 0xff))
1110 *owner_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, owner), sizeof (ts.owner));
1111 *nest_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, nest), sizeof (ts.nest));
1112 *entry_count_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, entry_count), sizeof (ts.entry_count));
1116 ves_icall_System_Threading_Monitor_Monitor_try_enter (MonoObject *obj, guint32 ms)
1121 res = mono_monitor_try_enter_internal (obj, ms, TRUE);
1123 mono_thread_interruption_checkpoint ();
1124 } while (res == -1);
1130 ves_icall_System_Threading_Monitor_Monitor_test_owner (MonoObject *obj)
1132 MonoThreadsSync *mon;
1134 LOCK_DEBUG (g_message ("%s: Testing if %p is owned by thread %d", __func__, obj, GetCurrentThreadId()));
1136 mon = obj->synchronisation;
1137 #ifdef HAVE_MOVING_COLLECTOR
1141 if (lw.lock_word & LOCK_WORD_THIN_HASH)
1143 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1151 if(mon->owner==GetCurrentThreadId ()) {
1159 ves_icall_System_Threading_Monitor_Monitor_test_synchronised (MonoObject *obj)
1161 MonoThreadsSync *mon;
1163 LOCK_DEBUG (g_message("%s: (%d) Testing if %p is owned by any thread", __func__, GetCurrentThreadId (), obj));
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 != 0) {
1187 /* All wait list manipulation in the pulse, pulseall and wait
1188 * functions happens while the monitor lock is held, so we don't need
1189 * any extra struct locking
1193 ves_icall_System_Threading_Monitor_Monitor_pulse (MonoObject *obj)
1195 MonoThreadsSync *mon;
1197 LOCK_DEBUG (g_message ("%s: (%d) Pulsing %p", __func__, GetCurrentThreadId (), obj));
1199 mon = obj->synchronisation;
1200 #ifdef HAVE_MOVING_COLLECTOR
1204 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1205 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1208 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1213 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1216 if (mon->owner != GetCurrentThreadId ()) {
1217 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1221 LOCK_DEBUG (g_message ("%s: (%d) %d threads waiting", __func__, GetCurrentThreadId (), g_slist_length (mon->wait_list)));
1223 if (mon->wait_list != NULL) {
1224 LOCK_DEBUG (g_message ("%s: (%d) signalling and dequeuing handle %p", __func__, GetCurrentThreadId (), mon->wait_list->data));
1226 SetEvent (mon->wait_list->data);
1227 mon->wait_list = g_slist_remove (mon->wait_list, mon->wait_list->data);
1232 ves_icall_System_Threading_Monitor_Monitor_pulse_all (MonoObject *obj)
1234 MonoThreadsSync *mon;
1236 LOCK_DEBUG (g_message("%s: (%d) Pulsing all %p", __func__, GetCurrentThreadId (), obj));
1238 mon = obj->synchronisation;
1239 #ifdef HAVE_MOVING_COLLECTOR
1243 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1244 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1247 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1252 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1255 if (mon->owner != GetCurrentThreadId ()) {
1256 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1260 LOCK_DEBUG (g_message ("%s: (%d) %d threads waiting", __func__, GetCurrentThreadId (), g_slist_length (mon->wait_list)));
1262 while (mon->wait_list != NULL) {
1263 LOCK_DEBUG (g_message ("%s: (%d) signalling and dequeuing handle %p", __func__, GetCurrentThreadId (), mon->wait_list->data));
1265 SetEvent (mon->wait_list->data);
1266 mon->wait_list = g_slist_remove (mon->wait_list, mon->wait_list->data);
1271 ves_icall_System_Threading_Monitor_Monitor_wait (MonoObject *obj, guint32 ms)
1273 MonoThreadsSync *mon;
1277 gboolean success = FALSE;
1279 MonoThread *thread = mono_thread_current ();
1281 LOCK_DEBUG (g_message ("%s: (%d) Trying to wait for %p with timeout %dms", __func__, GetCurrentThreadId (), obj, ms));
1283 mon = obj->synchronisation;
1284 #ifdef HAVE_MOVING_COLLECTOR
1288 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1289 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1292 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1297 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1300 if (mon->owner != GetCurrentThreadId ()) {
1301 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1305 /* Do this WaitSleepJoin check before creating the event handle */
1306 mono_thread_current_check_pending_interrupt ();
1308 event = CreateEvent (NULL, FALSE, FALSE, NULL);
1309 if (event == NULL) {
1310 mono_raise_exception (mono_get_exception_synchronization_lock ("Failed to set up wait event"));
1314 LOCK_DEBUG (g_message ("%s: (%d) queuing handle %p", __func__, GetCurrentThreadId (), event));
1316 mono_thread_current_check_pending_interrupt ();
1318 mono_thread_set_state (thread, ThreadState_WaitSleepJoin);
1320 mon->wait_list = g_slist_append (mon->wait_list, event);
1322 /* Save the nest count, and release the lock */
1325 mono_monitor_exit (obj);
1327 LOCK_DEBUG (g_message ("%s: (%d) Unlocked %p lock %p", __func__, GetCurrentThreadId (), obj, mon));
1329 /* There's no race between unlocking mon and waiting for the
1330 * event, because auto reset events are sticky, and this event
1331 * is private to this thread. Therefore even if the event was
1332 * signalled before we wait, we still succeed.
1334 ret = WaitForSingleObjectEx (event, ms, TRUE);
1336 /* Reset the thread state fairly early, so we don't have to worry
1337 * about the monitor error checking
1339 mono_thread_clr_state (thread, ThreadState_WaitSleepJoin);
1341 if (mono_thread_interruption_requested ()) {
1342 CloseHandle (event);
1346 /* Regain the lock with the previous nest count */
1348 regain = mono_monitor_try_enter_internal (obj, INFINITE, TRUE);
1350 mono_thread_interruption_checkpoint ();
1351 } while (regain == -1);
1354 /* Something went wrong, so throw a
1355 * SynchronizationLockException
1357 CloseHandle (event);
1358 mono_raise_exception (mono_get_exception_synchronization_lock ("Failed to regain lock"));
1364 LOCK_DEBUG (g_message ("%s: (%d) Regained %p lock %p", __func__, GetCurrentThreadId (), obj, mon));
1366 if (ret == WAIT_TIMEOUT) {
1367 /* Poll the event again, just in case it was signalled
1368 * while we were trying to regain the monitor lock
1370 ret = WaitForSingleObjectEx (event, 0, FALSE);
1373 /* Pulse will have popped our event from the queue if it signalled
1374 * us, so we only do it here if the wait timed out.
1376 * This avoids a race condition where the thread holding the
1377 * lock can Pulse several times before the WaitForSingleObject
1378 * returns. If we popped the queue here then this event might
1379 * be signalled more than once, thereby starving another
1383 if (ret == WAIT_OBJECT_0) {
1384 LOCK_DEBUG (g_message ("%s: (%d) Success", __func__, GetCurrentThreadId ()));
1387 LOCK_DEBUG (g_message ("%s: (%d) Wait failed, dequeuing handle %p", __func__, GetCurrentThreadId (), event));
1388 /* No pulse, so we have to remove ourself from the
1391 mon->wait_list = g_slist_remove (mon->wait_list, event);
1393 CloseHandle (event);