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/utils/mono-time.h>
30 * Pull the list of opcodes
32 #define OPDEF(a,b,c,d,e,f,g,h,i,j) \
36 #include "mono/cil/opcode.def"
41 /*#define LOCK_DEBUG(a) do { a; } while (0)*/
45 * The monitor implementation here is based on
46 * http://www.usenix.org/events/jvm01/full_papers/dice/dice.pdf and
47 * http://www.research.ibm.com/people/d/dfb/papers/Bacon98Thin.ps
49 * The Dice paper describes a technique for saving lock record space
50 * by returning records to a free list when they become unused. That
51 * sounds like unnecessary complexity to me, though if it becomes
52 * clear that unused lock records are taking up lots of space or we
53 * need to shave more time off by avoiding a malloc then we can always
54 * implement the free list idea later. The timeout parameter to
55 * try_enter voids some of the assumptions about the reference count
56 * field in Dice's implementation too. In his version, the thread
57 * attempting to lock a contended object will block until it succeeds,
58 * so the reference count will never be decremented while an object is
61 * Bacon's thin locks have a fast path that doesn't need a lock record
62 * for the common case of locking an unlocked or shallow-nested
63 * object, but the technique relies on encoding the thread ID in 15
64 * bits (to avoid too much per-object space overhead.) Unfortunately
65 * I don't think it's possible to reliably encode a pthread_t into 15
66 * bits. (The JVM implementation used seems to have a 15-bit
67 * per-thread identifier available.)
69 * This implementation then combines Dice's basic lock model with
70 * Bacon's simplification of keeping a lock record for the lifetime of
74 struct _MonoThreadsSync
76 gsize owner; /* thread ID */
78 #ifdef HAVE_MOVING_COLLECTOR
81 volatile gint32 entry_count;
87 typedef struct _MonitorArray MonitorArray;
89 struct _MonitorArray {
92 MonoThreadsSync monitors [MONO_ZERO_LEN_ARRAY];
95 #define mono_monitor_allocator_lock() EnterCriticalSection (&monitor_mutex)
96 #define mono_monitor_allocator_unlock() LeaveCriticalSection (&monitor_mutex)
97 static CRITICAL_SECTION monitor_mutex;
98 static MonoThreadsSync *monitor_freelist;
99 static MonitorArray *monitor_allocated;
100 static int array_size = 16;
102 #ifdef HAVE_KW_THREAD
103 static __thread gsize tls_pthread_self MONO_TLS_FAST;
106 #ifndef PLATFORM_WIN32
107 #ifdef HAVE_KW_THREAD
108 #define GetCurrentThreadId() tls_pthread_self
111 * The usual problem: we can't replace GetCurrentThreadId () with a macro because
112 * it is in a public header.
114 #define GetCurrentThreadId() ((gsize)pthread_self ())
119 mono_monitor_init (void)
121 InitializeCriticalSection (&monitor_mutex);
125 mono_monitor_cleanup (void)
127 /*DeleteCriticalSection (&monitor_mutex);*/
131 * mono_monitor_init_tls:
133 * Setup TLS variables used by the monitor code for the current thread.
136 mono_monitor_init_tls (void)
138 #if !defined(PLATFORM_WIN32) && defined(HAVE_KW_THREAD)
139 tls_pthread_self = pthread_self ();
144 monitor_is_on_freelist (MonoThreadsSync *mon)
146 MonitorArray *marray;
147 for (marray = monitor_allocated; marray; marray = marray->next) {
148 if (mon >= marray->monitors && mon < &marray->monitors [marray->num_monitors])
158 * Print a report on stdout of the managed locks currently held by
159 * threads. If @include_untaken is specified, list also inflated locks
161 * This is supposed to be used in debuggers like gdb.
164 mono_locks_dump (gboolean include_untaken)
167 int used = 0, on_freelist = 0, to_recycle = 0, total = 0, num_arrays = 0;
168 MonoThreadsSync *mon;
169 MonitorArray *marray;
170 for (mon = monitor_freelist; mon; mon = mon->data)
172 for (marray = monitor_allocated; marray; marray = marray->next) {
173 total += marray->num_monitors;
175 for (i = 0; i < marray->num_monitors; ++i) {
176 mon = &marray->monitors [i];
177 if (mon->data == NULL) {
178 if (i < marray->num_monitors - 1)
181 if (!monitor_is_on_freelist (mon->data)) {
182 MonoObject *holder = mono_gc_weak_link_get (&mon->data);
184 g_print ("Lock %p in object %p held by thread %p, nest level: %d\n",
185 mon, holder, (void*)mon->owner, mon->nest);
187 g_print ("\tWaiting on semaphore %p: %d\n", mon->entry_sem, mon->entry_count);
188 } else if (include_untaken) {
189 g_print ("Lock %p in object %p untaken\n", mon, holder);
196 g_print ("Total locks (in %d array(s)): %d, used: %d, on freelist: %d, to recycle: %d\n",
197 num_arrays, total, used, on_freelist, to_recycle);
200 /* LOCKING: this is called with monitor_mutex held */
202 mon_finalize (MonoThreadsSync *mon)
204 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": Finalizing sync %p", mon));
206 if (mon->entry_sem != NULL) {
207 CloseHandle (mon->entry_sem);
208 mon->entry_sem = NULL;
210 /* If this isn't empty then something is seriously broken - it
211 * means a thread is still waiting on the object that owned
212 * this lock, but the object has been finalized.
214 g_assert (mon->wait_list == NULL);
216 mon->entry_count = 0;
217 /* owner and nest are set in mon_new, no need to zero them out */
219 mon->data = monitor_freelist;
220 monitor_freelist = mon;
221 mono_perfcounters->gc_sync_blocks--;
224 /* LOCKING: this is called with monitor_mutex held */
225 static MonoThreadsSync *
228 MonoThreadsSync *new;
230 if (!monitor_freelist) {
231 MonitorArray *marray;
233 /* see if any sync block has been collected */
235 for (marray = monitor_allocated; marray; marray = marray->next) {
236 for (i = 0; i < marray->num_monitors; ++i) {
237 if (marray->monitors [i].data == NULL) {
238 new = &marray->monitors [i];
239 new->data = monitor_freelist;
240 monitor_freelist = new;
243 /* small perf tweak to avoid scanning all the blocks */
247 /* need to allocate a new array of monitors */
248 if (!monitor_freelist) {
250 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": allocating more monitors: %d", array_size));
251 marray = g_malloc0 (sizeof (MonoArray) + array_size * sizeof (MonoThreadsSync));
252 marray->num_monitors = array_size;
254 /* link into the freelist */
255 for (i = 0; i < marray->num_monitors - 1; ++i) {
256 marray->monitors [i].data = &marray->monitors [i + 1];
258 marray->monitors [i].data = NULL; /* the last one */
259 monitor_freelist = &marray->monitors [0];
260 /* we happend the marray instead of prepending so that
261 * the collecting loop above will need to scan smaller arrays first
263 if (!monitor_allocated) {
264 monitor_allocated = marray;
266 last = monitor_allocated;
274 new = monitor_freelist;
275 monitor_freelist = new->data;
280 mono_perfcounters->gc_sync_blocks++;
285 * Format of the lock word:
286 * thinhash | fathash | data
288 * thinhash is the lower bit: if set data is the shifted hashcode of the object.
289 * fathash is another bit: if set the hash code is stored in the MonoThreadsSync
290 * struct pointed to by data
291 * if neither bit is set and data is non-NULL, data is a MonoThreadsSync
295 MonoThreadsSync *sync;
299 LOCK_WORD_THIN_HASH = 1,
300 LOCK_WORD_FAT_HASH = 1 << 1,
301 LOCK_WORD_BITS_MASK = 0x3,
302 LOCK_WORD_HASH_SHIFT = 2
305 #define MONO_OBJECT_ALIGNMENT_SHIFT 3
311 * Calculate a hash code for @obj that is constant while @obj is alive.
314 mono_object_hash (MonoObject* obj)
316 #ifdef HAVE_MOVING_COLLECTOR
321 lw.sync = obj->synchronisation;
322 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
323 /*g_print ("fast thin hash %d for obj %p store\n", (unsigned int)lw.lock_word >> LOCK_WORD_HASH_SHIFT, obj);*/
324 return (unsigned int)lw.lock_word >> LOCK_WORD_HASH_SHIFT;
326 if (lw.lock_word & LOCK_WORD_FAT_HASH) {
327 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
328 /*g_print ("fast fat hash %d for obj %p store\n", lw.sync->hash_code, obj);*/
329 return lw.sync->hash_code;
332 * while we are inside this function, the GC will keep this object pinned,
333 * since we are in the unmanaged stack. Thanks to this and to the hash
334 * function that depends only on the address, we can ignore the races if
335 * another thread computes the hash at the same time, because it'll end up
336 * with the same value.
338 hash = (GPOINTER_TO_UINT (obj) >> MONO_OBJECT_ALIGNMENT_SHIFT) * 2654435761u;
339 /* clear the top bits as they can be discarded */
340 hash &= ~(LOCK_WORD_BITS_MASK << 30);
341 /* no hash flags were set, so it must be a MonoThreadsSync pointer if not NULL */
343 lw.sync->hash_code = hash;
344 /*g_print ("storing hash code %d for obj %p in sync %p\n", hash, obj, lw.sync);*/
345 lw.lock_word |= LOCK_WORD_FAT_HASH;
346 /* this is safe since we don't deflate locks */
347 obj->synchronisation = lw.sync;
349 /*g_print ("storing thin hash code %d for obj %p\n", hash, obj);*/
350 lw.lock_word = LOCK_WORD_THIN_HASH | (hash << LOCK_WORD_HASH_SHIFT);
351 if (InterlockedCompareExchangePointer ((gpointer*)&obj->synchronisation, lw.sync, NULL) == NULL)
353 /*g_print ("failed store\n");*/
354 /* someone set the hash flag or someone inflated the object */
355 lw.sync = obj->synchronisation;
356 if (lw.lock_word & LOCK_WORD_THIN_HASH)
358 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
359 lw.sync->hash_code = hash;
360 lw.lock_word |= LOCK_WORD_FAT_HASH;
361 /* this is safe since we don't deflate locks */
362 obj->synchronisation = lw.sync;
367 * Wang's address-based hash function:
368 * http://www.concentric.net/~Ttwang/tech/addrhash.htm
370 return (GPOINTER_TO_UINT (obj) >> MONO_OBJECT_ALIGNMENT_SHIFT) * 2654435761u;
374 /* If allow_interruption==TRUE, the method will be interrumped if abort or suspend
375 * is requested. In this case it returns -1.
378 mono_monitor_try_enter_internal (MonoObject *obj, guint32 ms, gboolean allow_interruption)
380 MonoThreadsSync *mon;
381 gsize id = GetCurrentThreadId ();
383 guint32 then = 0, now, delta;
388 LOCK_DEBUG (g_message(G_GNUC_PRETTY_FUNCTION
389 ": (%d) Trying to lock object %p (%d ms)", 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);
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);
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);
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 (G_GNUC_PRETTY_FUNCTION ": (%d) timed out, returning FALSE", id));
515 /* The slow path begins here. We need to make sure theres a
516 * semaphore handle (creating it if necessary), and block on
519 if (mon->entry_sem == NULL) {
520 /* Create the semaphore */
521 sem = CreateSemaphore (NULL, 0, 0x7fffffff, NULL);
522 g_assert (sem != NULL);
523 if (InterlockedCompareExchangePointer ((gpointer*)&mon->entry_sem, sem, NULL) != NULL) {
524 /* Someone else just put a handle here */
529 /* If we need to time out, record a timestamp and adjust ms,
530 * because WaitForSingleObject doesn't tell us how long it
533 * Don't block forever here, because theres a chance the owner
534 * thread released the lock while we were creating the
535 * semaphore: we would not get the wakeup. Using the event
536 * handle technique from pulse/wait would involve locking the
537 * lock struct and therefore slowing down the fast path.
539 if (ms != INFINITE) {
540 then = mono_msec_ticks ();
550 InterlockedIncrement (&mon->entry_count);
552 mono_perfcounters->thread_queue_len++;
553 mono_perfcounters->thread_queue_max++;
554 thread = mono_thread_current ();
556 mono_thread_set_state (thread, ThreadState_WaitSleepJoin);
559 * We pass TRUE instead of allow_interruption since we have to check for the
560 * StopRequested case below.
562 ret = WaitForSingleObjectEx (mon->entry_sem, waitms, TRUE);
564 mono_thread_clr_state (thread, ThreadState_WaitSleepJoin);
566 InterlockedDecrement (&mon->entry_count);
567 mono_perfcounters->thread_queue_len--;
569 if (ms != INFINITE) {
570 now = mono_msec_ticks ();
573 /* The counter must have wrapped around */
574 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
575 ": wrapped around! now=0x%x then=0x%x", now, then));
577 now += (0xffffffff - then);
580 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": wrap rejig: now=0x%x then=0x%x delta=0x%x", now, then, now-then));
590 if ((ret == WAIT_TIMEOUT || (ret == WAIT_IO_COMPLETION && !allow_interruption)) && ms > 0) {
595 if (ret == WAIT_TIMEOUT || (ret == WAIT_IO_COMPLETION && !allow_interruption)) {
596 if (ret == WAIT_IO_COMPLETION && mono_thread_test_state (mono_thread_current (), ThreadState_StopRequested)) {
598 * We have to obey a stop request even if allow_interruption is
599 * FALSE to avoid hangs at shutdown.
603 /* Infinite wait, so just try again */
608 if (ret == WAIT_OBJECT_0) {
609 /* retry from the top */
613 /* We must have timed out */
614 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) timed out waiting, returning FALSE", id));
616 if (ret == WAIT_IO_COMPLETION)
623 mono_monitor_enter (MonoObject *obj)
625 return mono_monitor_try_enter_internal (obj, INFINITE, FALSE) == 1;
629 mono_monitor_try_enter (MonoObject *obj, guint32 ms)
631 return mono_monitor_try_enter_internal (obj, ms, FALSE) == 1;
635 mono_monitor_exit (MonoObject *obj)
637 MonoThreadsSync *mon;
640 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) Unlocking %p", GetCurrentThreadId (), obj));
642 if (G_UNLIKELY (!obj)) {
643 mono_raise_exception (mono_get_exception_argument_null ("obj"));
647 mon = obj->synchronisation;
649 #ifdef HAVE_MOVING_COLLECTOR
653 if (lw.lock_word & LOCK_WORD_THIN_HASH)
655 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
659 if (G_UNLIKELY (mon == NULL)) {
660 /* No one ever used Enter. Just ignore the Exit request as MS does */
663 if (G_UNLIKELY (mon->owner != GetCurrentThreadId ())) {
667 nest = mon->nest - 1;
669 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
670 ": (%d) Object %p is now unlocked", GetCurrentThreadId (), obj));
672 /* object is now unlocked, leave nest==1 so we don't
673 * need to set it when the lock is reacquired
677 /* Do the wakeup stuff. It's possible that the last
678 * blocking thread gave up waiting just before we
679 * release the semaphore resulting in a futile wakeup
680 * next time there's contention for this object, but
681 * it means we don't have to waste time locking the
684 if (mon->entry_count > 0) {
685 ReleaseSemaphore (mon->entry_sem, 1, NULL);
688 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
689 ": (%d) Object %p is now locked %d times", GetCurrentThreadId (), obj, nest));
695 emit_obj_syncp_check (MonoMethodBuilder *mb, int syncp_loc, int *obj_null_branch, int *syncp_true_false_branch,
696 gboolean branch_on_true)
703 mono_mb_emit_byte (mb, CEE_LDARG_0);
704 *obj_null_branch = mono_mb_emit_short_branch (mb, CEE_BRFALSE_S);
709 ldc.i4 G_STRUCT_OFFSET(MonoObject, synchronisation) objp off
714 brtrue/false.s syncp_true_false
717 mono_mb_emit_byte (mb, CEE_LDARG_0);
718 mono_mb_emit_byte (mb, CEE_CONV_I);
719 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoObject, synchronisation));
720 mono_mb_emit_byte (mb, CEE_ADD);
721 mono_mb_emit_byte (mb, CEE_LDIND_I);
722 mono_mb_emit_stloc (mb, syncp_loc);
723 mono_mb_emit_ldloc (mb, syncp_loc);
724 *syncp_true_false_branch = mono_mb_emit_short_branch (mb, branch_on_true ? CEE_BRTRUE_S : CEE_BRFALSE_S);
728 mono_monitor_get_fast_enter_method (MonoMethod *monitor_enter_method)
730 static MonoMethod *fast_monitor_enter;
731 static MonoMethod *compare_exchange_method;
733 MonoMethodBuilder *mb;
734 int obj_null_branch, syncp_null_branch, has_owner_branch, other_owner_branch, tid_branch;
735 int tid_loc, syncp_loc, owner_loc;
736 int thread_tls_offset;
738 #ifdef HAVE_MOVING_COLLECTOR
742 thread_tls_offset = mono_thread_get_tls_offset ();
743 if (thread_tls_offset == -1)
746 if (fast_monitor_enter)
747 return fast_monitor_enter;
749 if (!compare_exchange_method) {
750 MonoMethodDesc *desc;
753 desc = mono_method_desc_new ("Interlocked:CompareExchange(intptr&,intptr,intptr)", FALSE);
754 class = mono_class_from_name (mono_defaults.corlib, "System.Threading", "Interlocked");
755 compare_exchange_method = mono_method_desc_search_in_class (desc, class);
756 mono_method_desc_free (desc);
758 if (!compare_exchange_method)
762 mb = mono_mb_new (mono_defaults.monitor_class, "FastMonitorEnter", MONO_WRAPPER_UNKNOWN);
764 mb->method->slot = -1;
765 mb->method->flags = METHOD_ATTRIBUTE_PUBLIC | METHOD_ATTRIBUTE_STATIC |
766 METHOD_ATTRIBUTE_HIDE_BY_SIG | METHOD_ATTRIBUTE_FINAL;
768 tid_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
769 syncp_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
770 owner_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
772 emit_obj_syncp_check (mb, syncp_loc, &obj_null_branch, &syncp_null_branch, FALSE);
775 mono. tls thread_tls_offset threadp
776 ldc.i4 G_STRUCT_OFFSET(MonoThread, tid) threadp off
781 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
789 mono_mb_emit_byte (mb, MONO_CUSTOM_PREFIX);
790 mono_mb_emit_byte (mb, CEE_MONO_TLS);
791 mono_mb_emit_i4 (mb, thread_tls_offset);
792 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThread, tid));
793 mono_mb_emit_byte (mb, CEE_ADD);
794 mono_mb_emit_byte (mb, CEE_LDIND_I);
795 mono_mb_emit_stloc (mb, tid_loc);
796 mono_mb_emit_ldloc (mb, syncp_loc);
797 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
798 mono_mb_emit_byte (mb, CEE_ADD);
799 mono_mb_emit_byte (mb, CEE_LDIND_I);
800 mono_mb_emit_stloc (mb, owner_loc);
801 mono_mb_emit_ldloc (mb, owner_loc);
802 tid_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
806 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
809 ldc.i4 0 &owner tid 0
810 call System.Threading.Interlocked.CompareExchange oldowner
815 mono_mb_emit_ldloc (mb, syncp_loc);
816 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
817 mono_mb_emit_byte (mb, CEE_ADD);
818 mono_mb_emit_ldloc (mb, tid_loc);
819 mono_mb_emit_byte (mb, CEE_LDC_I4_0);
820 mono_mb_emit_managed_call (mb, compare_exchange_method, NULL);
821 has_owner_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
822 mono_mb_emit_byte (mb, CEE_RET);
830 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, nest) syncp off
834 ldc.i4 1 &nest nest 1
840 mono_mb_patch_short_branch (mb, tid_branch);
841 mono_mb_emit_ldloc (mb, owner_loc);
842 mono_mb_emit_ldloc (mb, tid_loc);
843 other_owner_branch = mono_mb_emit_short_branch (mb, CEE_BNE_UN_S);
844 mono_mb_emit_ldloc (mb, syncp_loc);
845 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, nest));
846 mono_mb_emit_byte (mb, CEE_ADD);
847 mono_mb_emit_byte (mb, CEE_DUP);
848 mono_mb_emit_byte (mb, CEE_LDIND_I4);
849 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
850 mono_mb_emit_byte (mb, CEE_ADD);
851 mono_mb_emit_byte (mb, CEE_STIND_I4);
852 mono_mb_emit_byte (mb, CEE_RET);
855 obj_null, syncp_null, has_owner, other_owner:
857 call System.Threading.Monitor.Enter
861 mono_mb_patch_short_branch (mb, obj_null_branch);
862 mono_mb_patch_short_branch (mb, syncp_null_branch);
863 mono_mb_patch_short_branch (mb, has_owner_branch);
864 mono_mb_patch_short_branch (mb, other_owner_branch);
865 mono_mb_emit_byte (mb, CEE_LDARG_0);
866 mono_mb_emit_managed_call (mb, monitor_enter_method, NULL);
867 mono_mb_emit_byte (mb, CEE_RET);
869 fast_monitor_enter = mono_mb_create_method (mb, mono_signature_no_pinvoke (monitor_enter_method), 5);
872 return fast_monitor_enter;
876 mono_monitor_get_fast_exit_method (MonoMethod *monitor_exit_method)
878 static MonoMethod *fast_monitor_exit;
880 MonoMethodBuilder *mb;
881 int obj_null_branch, has_waiting_branch, has_syncp_branch, owned_branch, nested_branch;
882 int thread_tls_offset;
885 #ifdef HAVE_MOVING_COLLECTOR
889 thread_tls_offset = mono_thread_get_tls_offset ();
890 if (thread_tls_offset == -1)
893 if (fast_monitor_exit)
894 return fast_monitor_exit;
896 mb = mono_mb_new (mono_defaults.monitor_class, "FastMonitorExit", MONO_WRAPPER_UNKNOWN);
898 mb->method->slot = -1;
899 mb->method->flags = METHOD_ATTRIBUTE_PUBLIC | METHOD_ATTRIBUTE_STATIC |
900 METHOD_ATTRIBUTE_HIDE_BY_SIG | METHOD_ATTRIBUTE_FINAL;
902 syncp_loc = mono_mb_add_local (mb, &mono_defaults.int_class->byval_arg);
904 emit_obj_syncp_check (mb, syncp_loc, &obj_null_branch, &has_syncp_branch, TRUE);
910 mono_mb_emit_byte (mb, CEE_RET);
915 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
918 mono. tls thread_tls_offset owner threadp
919 ldc.i4 G_STRUCT_OFFSET(MonoThread, tid) owner threadp off
925 mono_mb_patch_short_branch (mb, has_syncp_branch);
926 mono_mb_emit_ldloc (mb, syncp_loc);
927 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
928 mono_mb_emit_byte (mb, CEE_ADD);
929 mono_mb_emit_byte (mb, CEE_LDIND_I);
930 mono_mb_emit_byte (mb, MONO_CUSTOM_PREFIX);
931 mono_mb_emit_byte (mb, CEE_MONO_TLS);
932 mono_mb_emit_i4 (mb, thread_tls_offset);
933 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThread, tid));
934 mono_mb_emit_byte (mb, CEE_ADD);
935 mono_mb_emit_byte (mb, CEE_LDIND_I);
936 owned_branch = mono_mb_emit_short_branch (mb, CEE_BEQ_S);
942 mono_mb_emit_byte (mb, CEE_RET);
947 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, nest) syncp off
952 ldc.i4 1 &nest nest nest 1
953 bgt.un.s nested &nest nest
956 mono_mb_patch_short_branch (mb, owned_branch);
957 mono_mb_emit_ldloc (mb, syncp_loc);
958 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, nest));
959 mono_mb_emit_byte (mb, CEE_ADD);
960 mono_mb_emit_byte (mb, CEE_DUP);
961 mono_mb_emit_byte (mb, CEE_LDIND_I4);
962 mono_mb_emit_byte (mb, CEE_DUP);
963 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
964 nested_branch = mono_mb_emit_short_branch (mb, CEE_BGT_UN_S);
970 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, entry_count) syncp off
976 mono_mb_emit_byte (mb, CEE_POP);
977 mono_mb_emit_byte (mb, CEE_POP);
978 mono_mb_emit_ldloc (mb, syncp_loc);
979 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, entry_count));
980 mono_mb_emit_byte (mb, CEE_ADD);
981 mono_mb_emit_byte (mb, CEE_LDIND_I4);
982 has_waiting_branch = mono_mb_emit_short_branch (mb, CEE_BRTRUE_S);
986 ldc.i4 G_STRUCT_OFFSET(MonoThreadsSync, owner) syncp off
993 mono_mb_emit_ldloc (mb, syncp_loc);
994 mono_mb_emit_icon (mb, G_STRUCT_OFFSET (MonoThreadsSync, owner));
995 mono_mb_emit_byte (mb, CEE_ADD);
996 mono_mb_emit_byte (mb, CEE_LDNULL);
997 mono_mb_emit_byte (mb, CEE_STIND_I);
998 mono_mb_emit_byte (mb, CEE_RET);
1002 ldc.i4 1 &nest nest 1
1008 mono_mb_patch_short_branch (mb, nested_branch);
1009 mono_mb_emit_byte (mb, CEE_LDC_I4_1);
1010 mono_mb_emit_byte (mb, CEE_SUB);
1011 mono_mb_emit_byte (mb, CEE_STIND_I4);
1012 mono_mb_emit_byte (mb, CEE_RET);
1015 obj_null, has_waiting:
1017 call System.Threading.Monitor.Exit
1021 mono_mb_patch_short_branch (mb, obj_null_branch);
1022 mono_mb_patch_short_branch (mb, has_waiting_branch);
1023 mono_mb_emit_byte (mb, CEE_LDARG_0);
1024 mono_mb_emit_managed_call (mb, monitor_exit_method, NULL);
1025 mono_mb_emit_byte (mb, CEE_RET);
1027 fast_monitor_exit = mono_mb_create_method (mb, mono_signature_no_pinvoke (monitor_exit_method), 5);
1030 return fast_monitor_exit;
1034 mono_monitor_get_fast_path (MonoMethod *enter_or_exit)
1036 if (strcmp (enter_or_exit->name, "Enter") == 0)
1037 return mono_monitor_get_fast_enter_method (enter_or_exit);
1038 if (strcmp (enter_or_exit->name, "Exit") == 0)
1039 return mono_monitor_get_fast_exit_method (enter_or_exit);
1040 g_assert_not_reached ();
1045 * mono_monitor_threads_sync_member_offset:
1046 * @owner_offset: returns size and offset of the "owner" member
1047 * @nest_offset: returns size and offset of the "nest" member
1048 * @entry_count_offset: returns size and offset of the "entry_count" member
1050 * Returns the offsets and sizes of three members of the
1051 * MonoThreadsSync struct. The Monitor ASM fastpaths need this.
1054 mono_monitor_threads_sync_members_offset (int *owner_offset, int *nest_offset, int *entry_count_offset)
1058 #define ENCODE_OFF_SIZE(o,s) (((o) << 8) | ((s) & 0xff))
1060 *owner_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, owner), sizeof (ts.owner));
1061 *nest_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, nest), sizeof (ts.nest));
1062 *entry_count_offset = ENCODE_OFF_SIZE (G_STRUCT_OFFSET (MonoThreadsSync, entry_count), sizeof (ts.entry_count));
1066 ves_icall_System_Threading_Monitor_Monitor_try_enter (MonoObject *obj, guint32 ms)
1071 res = mono_monitor_try_enter_internal (obj, ms, TRUE);
1073 mono_thread_interruption_checkpoint ();
1074 } while (res == -1);
1080 ves_icall_System_Threading_Monitor_Monitor_test_owner (MonoObject *obj)
1082 MonoThreadsSync *mon;
1084 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
1085 ": Testing if %p is owned by thread %d", obj, GetCurrentThreadId()));
1087 mon = obj->synchronisation;
1088 #ifdef HAVE_MOVING_COLLECTOR
1092 if (lw.lock_word & LOCK_WORD_THIN_HASH)
1094 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1102 if(mon->owner==GetCurrentThreadId ()) {
1110 ves_icall_System_Threading_Monitor_Monitor_test_synchronised (MonoObject *obj)
1112 MonoThreadsSync *mon;
1114 LOCK_DEBUG (g_message(G_GNUC_PRETTY_FUNCTION
1115 ": (%d) Testing if %p is owned by any thread", GetCurrentThreadId (), obj));
1117 mon = obj->synchronisation;
1118 #ifdef HAVE_MOVING_COLLECTOR
1122 if (lw.lock_word & LOCK_WORD_THIN_HASH)
1124 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1132 if (mon->owner != 0) {
1139 /* All wait list manipulation in the pulse, pulseall and wait
1140 * functions happens while the monitor lock is held, so we don't need
1141 * any extra struct locking
1145 ves_icall_System_Threading_Monitor_Monitor_pulse (MonoObject *obj)
1147 MonoThreadsSync *mon;
1149 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) Pulsing %p",
1150 GetCurrentThreadId (), obj));
1152 mon = obj->synchronisation;
1153 #ifdef HAVE_MOVING_COLLECTOR
1157 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1158 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1161 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1166 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1169 if (mon->owner != GetCurrentThreadId ()) {
1170 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1174 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) %d threads waiting",
1175 GetCurrentThreadId (), g_slist_length (mon->wait_list)));
1177 if (mon->wait_list != NULL) {
1178 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
1179 ": (%d) signalling and dequeuing handle %p",
1180 GetCurrentThreadId (), mon->wait_list->data));
1182 SetEvent (mon->wait_list->data);
1183 mon->wait_list = g_slist_remove (mon->wait_list, mon->wait_list->data);
1188 ves_icall_System_Threading_Monitor_Monitor_pulse_all (MonoObject *obj)
1190 MonoThreadsSync *mon;
1192 LOCK_DEBUG (g_message(G_GNUC_PRETTY_FUNCTION ": (%d) Pulsing all %p",
1193 GetCurrentThreadId (), obj));
1195 mon = obj->synchronisation;
1196 #ifdef HAVE_MOVING_COLLECTOR
1200 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1201 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1204 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1209 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1212 if (mon->owner != GetCurrentThreadId ()) {
1213 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1217 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) %d threads waiting",
1218 GetCurrentThreadId (), g_slist_length (mon->wait_list)));
1220 while (mon->wait_list != NULL) {
1221 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
1222 ": (%d) signalling and dequeuing handle %p",
1223 GetCurrentThreadId (), mon->wait_list->data));
1225 SetEvent (mon->wait_list->data);
1226 mon->wait_list = g_slist_remove (mon->wait_list, mon->wait_list->data);
1231 ves_icall_System_Threading_Monitor_Monitor_wait (MonoObject *obj, guint32 ms)
1233 MonoThreadsSync *mon;
1237 gboolean success = FALSE;
1239 MonoThread *thread = mono_thread_current ();
1241 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION
1242 ": (%d) Trying to wait for %p with timeout %dms",
1243 GetCurrentThreadId (), obj, ms));
1245 mon = obj->synchronisation;
1246 #ifdef HAVE_MOVING_COLLECTOR
1250 if (lw.lock_word & LOCK_WORD_THIN_HASH) {
1251 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1254 lw.lock_word &= ~LOCK_WORD_BITS_MASK;
1259 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked"));
1262 if (mon->owner != GetCurrentThreadId ()) {
1263 mono_raise_exception (mono_get_exception_synchronization_lock ("Not locked by this thread"));
1267 /* Do this WaitSleepJoin check before creating the event handle */
1268 mono_thread_current_check_pending_interrupt ();
1270 event = CreateEvent (NULL, FALSE, FALSE, NULL);
1271 if (event == NULL) {
1272 mono_raise_exception (mono_get_exception_synchronization_lock ("Failed to set up wait event"));
1276 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) queuing handle %p",
1277 GetCurrentThreadId (), event));
1279 mono_thread_current_check_pending_interrupt ();
1281 mono_thread_set_state (thread, ThreadState_WaitSleepJoin);
1283 mon->wait_list = g_slist_append (mon->wait_list, event);
1285 /* Save the nest count, and release the lock */
1288 mono_monitor_exit (obj);
1290 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) Unlocked %p lock %p",
1291 GetCurrentThreadId (), obj, mon));
1293 /* There's no race between unlocking mon and waiting for the
1294 * event, because auto reset events are sticky, and this event
1295 * is private to this thread. Therefore even if the event was
1296 * signalled before we wait, we still succeed.
1298 ret = WaitForSingleObjectEx (event, ms, TRUE);
1300 /* Reset the thread state fairly early, so we don't have to worry
1301 * about the monitor error checking
1303 mono_thread_clr_state (thread, ThreadState_WaitSleepJoin);
1305 if (mono_thread_interruption_requested ()) {
1306 CloseHandle (event);
1310 /* Regain the lock with the previous nest count */
1312 regain = mono_monitor_try_enter_internal (obj, INFINITE, TRUE);
1314 mono_thread_interruption_checkpoint ();
1315 } while (regain == -1);
1318 /* Something went wrong, so throw a
1319 * SynchronizationLockException
1321 CloseHandle (event);
1322 mono_raise_exception (mono_get_exception_synchronization_lock ("Failed to regain lock"));
1328 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) Regained %p lock %p",
1329 GetCurrentThreadId (), obj, mon));
1331 if (ret == WAIT_TIMEOUT) {
1332 /* Poll the event again, just in case it was signalled
1333 * while we were trying to regain the monitor lock
1335 ret = WaitForSingleObjectEx (event, 0, FALSE);
1338 /* Pulse will have popped our event from the queue if it signalled
1339 * us, so we only do it here if the wait timed out.
1341 * This avoids a race condition where the thread holding the
1342 * lock can Pulse several times before the WaitForSingleObject
1343 * returns. If we popped the queue here then this event might
1344 * be signalled more than once, thereby starving another
1348 if (ret == WAIT_OBJECT_0) {
1349 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) Success",
1350 GetCurrentThreadId ()));
1353 LOCK_DEBUG (g_message (G_GNUC_PRETTY_FUNCTION ": (%d) Wait failed, dequeuing handle %p",
1354 GetCurrentThreadId (), event));
1355 /* No pulse, so we have to remove ourself from the
1358 mon->wait_list = g_slist_remove (mon->wait_list, event);
1360 CloseHandle (event);