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Elliott Hughes5f791332011-09-15 17:45:30 -07001/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
Elliott Hughes54e7df12011-09-16 11:47:04 -070017#include "monitor.h"
Elliott Hughes5f791332011-09-15 17:45:30 -070018
19#include <errno.h>
20#include <fcntl.h>
21#include <pthread.h>
22#include <stdlib.h>
23#include <sys/time.h>
24#include <time.h>
25#include <unistd.h>
26
jeffhao33dc7712011-11-09 17:54:24 -080027#include "class_linker.h"
Elliott Hughes5f791332011-09-15 17:45:30 -070028#include "mutex.h"
29#include "object.h"
Ian Rogers6d4d9fc2011-11-30 16:24:48 -080030#include "object_utils.h"
Elliott Hughes88c5c352012-03-15 18:49:48 -070031#include "scoped_thread_list_lock.h"
Elliott Hughesc33a32b2011-10-11 18:18:07 -070032#include "stl_util.h"
Elliott Hughes5f791332011-09-15 17:45:30 -070033#include "thread.h"
Elliott Hughes8e4aac52011-09-26 17:03:36 -070034#include "thread_list.h"
Elliott Hughes5f791332011-09-15 17:45:30 -070035
36namespace art {
37
38/*
39 * Every Object has a monitor associated with it, but not every Object is
40 * actually locked. Even the ones that are locked do not need a
41 * full-fledged monitor until a) there is actual contention or b) wait()
42 * is called on the Object.
43 *
44 * For Android, we have implemented a scheme similar to the one described
45 * in Bacon et al.'s "Thin locks: featherweight synchronization for Java"
46 * (ACM 1998). Things are even easier for us, though, because we have
47 * a full 32 bits to work with.
48 *
49 * The two states of an Object's lock are referred to as "thin" and
50 * "fat". A lock may transition from the "thin" state to the "fat"
51 * state and this transition is referred to as inflation. Once a lock
52 * has been inflated it remains in the "fat" state indefinitely.
53 *
54 * The lock value itself is stored in Object.lock. The LSB of the
55 * lock encodes its state. When cleared, the lock is in the "thin"
56 * state and its bits are formatted as follows:
57 *
58 * [31 ---- 19] [18 ---- 3] [2 ---- 1] [0]
59 * lock count thread id hash state 0
60 *
61 * When set, the lock is in the "fat" state and its bits are formatted
62 * as follows:
63 *
64 * [31 ---- 3] [2 ---- 1] [0]
65 * pointer hash state 1
66 *
67 * For an in-depth description of the mechanics of thin-vs-fat locking,
68 * read the paper referred to above.
Elliott Hughes54e7df12011-09-16 11:47:04 -070069 *
Elliott Hughes5f791332011-09-15 17:45:30 -070070 * Monitors provide:
71 * - mutually exclusive access to resources
72 * - a way for multiple threads to wait for notification
73 *
74 * In effect, they fill the role of both mutexes and condition variables.
75 *
76 * Only one thread can own the monitor at any time. There may be several
77 * threads waiting on it (the wait call unlocks it). One or more waiting
78 * threads may be getting interrupted or notified at any given time.
79 *
80 * TODO: the various members of monitor are not SMP-safe.
81 */
Elliott Hughes54e7df12011-09-16 11:47:04 -070082
83
84/*
85 * Monitor accessor. Extracts a monitor structure pointer from a fat
86 * lock. Performs no error checking.
87 */
88#define LW_MONITOR(x) \
Elliott Hughes398f64b2012-03-26 18:05:48 -070089 (reinterpret_cast<Monitor*>((x) & ~((LW_HASH_STATE_MASK << LW_HASH_STATE_SHIFT) | LW_SHAPE_MASK)))
Elliott Hughes54e7df12011-09-16 11:47:04 -070090
91/*
92 * Lock recursion count field. Contains a count of the number of times
93 * a lock has been recursively acquired.
94 */
95#define LW_LOCK_COUNT_MASK 0x1fff
96#define LW_LOCK_COUNT_SHIFT 19
97#define LW_LOCK_COUNT(x) (((x) >> LW_LOCK_COUNT_SHIFT) & LW_LOCK_COUNT_MASK)
98
Elliott Hughesfc861622011-10-17 17:57:47 -070099bool (*Monitor::is_sensitive_thread_hook_)() = NULL;
Elliott Hughesfc861622011-10-17 17:57:47 -0700100uint32_t Monitor::lock_profiling_threshold_ = 0;
Elliott Hughes32d6e1e2011-10-11 14:47:44 -0700101
Elliott Hughesfc861622011-10-17 17:57:47 -0700102bool Monitor::IsSensitiveThread() {
103 if (is_sensitive_thread_hook_ != NULL) {
104 return (*is_sensitive_thread_hook_)();
105 }
106 return false;
107}
108
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800109void Monitor::Init(uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)()) {
Elliott Hughesfc861622011-10-17 17:57:47 -0700110 lock_profiling_threshold_ = lock_profiling_threshold;
111 is_sensitive_thread_hook_ = is_sensitive_thread_hook;
Elliott Hughes32d6e1e2011-10-11 14:47:44 -0700112}
113
Elliott Hughes5f791332011-09-15 17:45:30 -0700114Monitor::Monitor(Object* obj)
115 : owner_(NULL),
116 lock_count_(0),
117 obj_(obj),
118 wait_set_(NULL),
119 lock_("a monitor lock"),
jeffhao33dc7712011-11-09 17:54:24 -0800120 locking_method_(NULL),
121 locking_pc_(0) {
Elliott Hughes5f791332011-09-15 17:45:30 -0700122}
123
124Monitor::~Monitor() {
125 DCHECK(obj_ != NULL);
126 DCHECK_EQ(LW_SHAPE(*obj_->GetRawLockWordAddress()), LW_SHAPE_FAT);
Elliott Hughes5f791332011-09-15 17:45:30 -0700127}
128
129/*
130 * Links a thread into a monitor's wait set. The monitor lock must be
131 * held by the caller of this routine.
132 */
133void Monitor::AppendToWaitSet(Thread* thread) {
134 DCHECK(owner_ == Thread::Current());
135 DCHECK(thread != NULL);
Elliott Hughesdc33ad52011-09-16 19:46:51 -0700136 DCHECK(thread->wait_next_ == NULL) << thread->wait_next_;
Elliott Hughes5f791332011-09-15 17:45:30 -0700137 if (wait_set_ == NULL) {
138 wait_set_ = thread;
139 return;
140 }
141
142 // push_back.
143 Thread* t = wait_set_;
144 while (t->wait_next_ != NULL) {
145 t = t->wait_next_;
146 }
147 t->wait_next_ = thread;
148}
149
150/*
151 * Unlinks a thread from a monitor's wait set. The monitor lock must
152 * be held by the caller of this routine.
153 */
154void Monitor::RemoveFromWaitSet(Thread *thread) {
155 DCHECK(owner_ == Thread::Current());
156 DCHECK(thread != NULL);
157 if (wait_set_ == NULL) {
158 return;
159 }
160 if (wait_set_ == thread) {
161 wait_set_ = thread->wait_next_;
162 thread->wait_next_ = NULL;
163 return;
164 }
165
166 Thread* t = wait_set_;
167 while (t->wait_next_ != NULL) {
168 if (t->wait_next_ == thread) {
169 t->wait_next_ = thread->wait_next_;
170 thread->wait_next_ = NULL;
171 return;
172 }
173 t = t->wait_next_;
174 }
175}
176
Elliott Hughesc33a32b2011-10-11 18:18:07 -0700177Object* Monitor::GetObject() {
178 return obj_;
Elliott Hughes5f791332011-09-15 17:45:30 -0700179}
180
Elliott Hughes5f791332011-09-15 17:45:30 -0700181void Monitor::Lock(Thread* self) {
Elliott Hughes5f791332011-09-15 17:45:30 -0700182 if (owner_ == self) {
183 lock_count_++;
184 return;
185 }
Elliott Hughesfc861622011-10-17 17:57:47 -0700186
187 uint64_t waitStart, waitEnd;
Elliott Hughes5f791332011-09-15 17:45:30 -0700188 if (!lock_.TryLock()) {
Elliott Hughesfc861622011-10-17 17:57:47 -0700189 uint32_t wait_threshold = lock_profiling_threshold_;
jeffhao33dc7712011-11-09 17:54:24 -0800190 const Method* current_locking_method = NULL;
Elliott Hughese65a6c92012-01-18 23:48:31 -0800191 uintptr_t current_locking_pc = 0;
Elliott Hughes5f791332011-09-15 17:45:30 -0700192 {
193 ScopedThreadStateChange tsc(self, Thread::kBlocked);
Elliott Hughesfc861622011-10-17 17:57:47 -0700194 if (wait_threshold != 0) {
195 waitStart = NanoTime() / 1000;
196 }
jeffhao33dc7712011-11-09 17:54:24 -0800197 current_locking_method = locking_method_;
198 current_locking_pc = locking_pc_;
Elliott Hughes5f791332011-09-15 17:45:30 -0700199
200 lock_.Lock();
Elliott Hughesfc861622011-10-17 17:57:47 -0700201 if (wait_threshold != 0) {
202 waitEnd = NanoTime() / 1000;
203 }
Elliott Hughes5f791332011-09-15 17:45:30 -0700204 }
Elliott Hughesfc861622011-10-17 17:57:47 -0700205
206 if (wait_threshold != 0) {
207 uint64_t wait_ms = (waitEnd - waitStart) / 1000;
208 uint32_t sample_percent;
209 if (wait_ms >= wait_threshold) {
210 sample_percent = 100;
211 } else {
212 sample_percent = 100 * wait_ms / wait_threshold;
213 }
214 if (sample_percent != 0 && (static_cast<uint32_t>(rand() % 100) < sample_percent)) {
jeffhao33dc7712011-11-09 17:54:24 -0800215 const char* current_locking_filename;
216 uint32_t current_locking_line_number;
217 TranslateLocation(current_locking_method, current_locking_pc,
218 current_locking_filename, current_locking_line_number);
219 LogContentionEvent(self, wait_ms, sample_percent, current_locking_filename, current_locking_line_number);
Elliott Hughesfc861622011-10-17 17:57:47 -0700220 }
221 }
Elliott Hughes5f791332011-09-15 17:45:30 -0700222 }
223 owner_ = self;
224 DCHECK_EQ(lock_count_, 0);
225
226 // When debugging, save the current monitor holder for future
227 // acquisition failures to use in sampled logging.
Elliott Hughesfc861622011-10-17 17:57:47 -0700228 if (lock_profiling_threshold_ != 0) {
Elliott Hughesd07986f2011-12-06 18:27:45 -0800229 locking_method_ = self->GetCurrentMethod(&locking_pc_);
Elliott Hughesfc861622011-10-17 17:57:47 -0700230 }
Elliott Hughes5f791332011-09-15 17:45:30 -0700231}
232
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800233static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...)
234 __attribute__((format(printf, 1, 2)));
235
236static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...) {
237 va_list args;
238 va_start(args, fmt);
239 Thread::Current()->ThrowNewExceptionV("Ljava/lang/IllegalMonitorStateException;", fmt, args);
Brian Carlstrom64277f32012-03-26 23:53:34 -0700240 if (!Runtime::Current()->IsStarted()) {
241 std::ostringstream ss;
242 Thread::Current()->Dump(ss);
243 std::string str(ss.str());
244 LOG(ERROR) << "IllegalMonitorStateException: " << str;
245 }
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800246 va_end(args);
247}
248
Elliott Hughesd4237412012-02-21 11:24:45 -0800249static std::string ThreadToString(Thread* thread) {
250 if (thread == NULL) {
251 return "NULL";
252 }
253 std::ostringstream oss;
254 // TODO: alternatively, we could just return the thread's name.
255 oss << *thread;
256 return oss.str();
257}
258
Elliott Hughesffb465f2012-03-01 18:46:05 -0800259void Monitor::FailedUnlock(Object* o, Thread* expected_owner, Thread* found_owner,
260 Monitor* monitor) {
261 Thread* current_owner = NULL;
262 std::string current_owner_string;
263 std::string expected_owner_string;
264 std::string found_owner_string;
265 {
266 // TODO: isn't this too late to prevent threads from disappearing?
267 // Acquire thread list lock so threads won't disappear from under us.
268 ScopedThreadListLock thread_list_lock;
269 // Re-read owner now that we hold lock.
270 current_owner = (monitor != NULL) ? monitor->owner_ : NULL;
271 // Get short descriptions of the threads involved.
272 current_owner_string = ThreadToString(current_owner);
273 expected_owner_string = ThreadToString(expected_owner);
274 found_owner_string = ThreadToString(found_owner);
275 }
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800276 if (current_owner == NULL) {
277 if (found_owner == NULL) {
278 ThrowIllegalMonitorStateExceptionF("unlock of unowned monitor on object of type '%s'"
279 " on thread '%s'",
Elliott Hughesffb465f2012-03-01 18:46:05 -0800280 PrettyTypeOf(o).c_str(),
281 expected_owner_string.c_str());
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800282 } else {
283 // Race: the original read found an owner but now there is none
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800284 ThrowIllegalMonitorStateExceptionF("unlock of monitor owned by '%s' on object of type '%s'"
285 " (where now the monitor appears unowned) on thread '%s'",
Elliott Hughesffb465f2012-03-01 18:46:05 -0800286 found_owner_string.c_str(),
287 PrettyTypeOf(o).c_str(),
288 expected_owner_string.c_str());
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800289 }
290 } else {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800291 if (found_owner == NULL) {
292 // Race: originally there was no owner, there is now
293 ThrowIllegalMonitorStateExceptionF("unlock of monitor owned by '%s' on object of type '%s'"
294 " (originally believed to be unowned) on thread '%s'",
Elliott Hughesffb465f2012-03-01 18:46:05 -0800295 current_owner_string.c_str(),
296 PrettyTypeOf(o).c_str(),
297 expected_owner_string.c_str());
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800298 } else {
299 if (found_owner != current_owner) {
300 // Race: originally found and current owner have changed
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800301 ThrowIllegalMonitorStateExceptionF("unlock of monitor originally owned by '%s' (now"
302 " owned by '%s') on object of type '%s' on thread '%s'",
Elliott Hughesffb465f2012-03-01 18:46:05 -0800303 found_owner_string.c_str(),
304 current_owner_string.c_str(),
305 PrettyTypeOf(o).c_str(),
306 expected_owner_string.c_str());
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800307 } else {
308 ThrowIllegalMonitorStateExceptionF("unlock of monitor owned by '%s' on object of type '%s'"
309 " on thread '%s",
Elliott Hughesffb465f2012-03-01 18:46:05 -0800310 current_owner_string.c_str(),
311 PrettyTypeOf(o).c_str(),
312 expected_owner_string.c_str());
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800313 }
314 }
315 }
Elliott Hughes5f791332011-09-15 17:45:30 -0700316}
317
318bool Monitor::Unlock(Thread* self) {
319 DCHECK(self != NULL);
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800320 Thread* owner = owner_;
321 if (owner == self) {
Elliott Hughes5f791332011-09-15 17:45:30 -0700322 // We own the monitor, so nobody else can be in here.
323 if (lock_count_ == 0) {
324 owner_ = NULL;
jeffhao33dc7712011-11-09 17:54:24 -0800325 locking_method_ = NULL;
326 locking_pc_ = 0;
Elliott Hughes5f791332011-09-15 17:45:30 -0700327 lock_.Unlock();
328 } else {
329 --lock_count_;
330 }
331 } else {
332 // We don't own this, so we're not allowed to unlock it.
333 // The JNI spec says that we should throw IllegalMonitorStateException
334 // in this case.
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800335 FailedUnlock(obj_, self, owner, this);
Elliott Hughes5f791332011-09-15 17:45:30 -0700336 return false;
337 }
338 return true;
339}
340
341/*
342 * Converts the given relative waiting time into an absolute time.
343 */
Elliott Hughesb8d2eeb2012-02-29 16:44:41 -0800344static void ToAbsoluteTime(int64_t ms, int32_t ns, struct timespec *ts) {
Elliott Hughes5f791332011-09-15 17:45:30 -0700345 int64_t endSec;
346
347#ifdef HAVE_TIMEDWAIT_MONOTONIC
348 clock_gettime(CLOCK_MONOTONIC, ts);
349#else
350 {
351 struct timeval tv;
352 gettimeofday(&tv, NULL);
353 ts->tv_sec = tv.tv_sec;
354 ts->tv_nsec = tv.tv_usec * 1000;
355 }
356#endif
357 endSec = ts->tv_sec + ms / 1000;
358 if (endSec >= 0x7fffffff) {
359 LOG(INFO) << "Note: end time exceeds epoch";
360 endSec = 0x7ffffffe;
361 }
362 ts->tv_sec = endSec;
363 ts->tv_nsec = (ts->tv_nsec + (ms % 1000) * 1000000) + ns;
364
365 // Catch rollover.
366 if (ts->tv_nsec >= 1000000000L) {
367 ts->tv_sec++;
368 ts->tv_nsec -= 1000000000L;
369 }
370}
371
Elliott Hughes5f791332011-09-15 17:45:30 -0700372/*
373 * Wait on a monitor until timeout, interrupt, or notification. Used for
374 * Object.wait() and (somewhat indirectly) Thread.sleep() and Thread.join().
375 *
376 * If another thread calls Thread.interrupt(), we throw InterruptedException
377 * and return immediately if one of the following are true:
378 * - blocked in wait(), wait(long), or wait(long, int) methods of Object
379 * - blocked in join(), join(long), or join(long, int) methods of Thread
380 * - blocked in sleep(long), or sleep(long, int) methods of Thread
381 * Otherwise, we set the "interrupted" flag.
382 *
383 * Checks to make sure that "ns" is in the range 0-999999
384 * (i.e. fractions of a millisecond) and throws the appropriate
385 * exception if it isn't.
386 *
387 * The spec allows "spurious wakeups", and recommends that all code using
388 * Object.wait() do so in a loop. This appears to derive from concerns
389 * about pthread_cond_wait() on multiprocessor systems. Some commentary
390 * on the web casts doubt on whether these can/should occur.
391 *
392 * Since we're allowed to wake up "early", we clamp extremely long durations
393 * to return at the end of the 32-bit time epoch.
394 */
395void Monitor::Wait(Thread* self, int64_t ms, int32_t ns, bool interruptShouldThrow) {
396 DCHECK(self != NULL);
397
398 // Make sure that we hold the lock.
399 if (owner_ != self) {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800400 ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()");
Elliott Hughes5f791332011-09-15 17:45:30 -0700401 return;
402 }
403
404 // Enforce the timeout range.
405 if (ms < 0 || ns < 0 || ns > 999999) {
Elliott Hughes5cb5ad22011-10-02 12:13:39 -0700406 Thread::Current()->ThrowNewExceptionF("Ljava/lang/IllegalArgumentException;",
Elliott Hughes5f791332011-09-15 17:45:30 -0700407 "timeout arguments out of range: ms=%lld ns=%d", ms, ns);
408 return;
409 }
410
411 // Compute absolute wakeup time, if necessary.
412 struct timespec ts;
413 bool timed = false;
414 if (ms != 0 || ns != 0) {
415 ToAbsoluteTime(ms, ns, &ts);
416 timed = true;
417 }
418
419 /*
420 * Add ourselves to the set of threads waiting on this monitor, and
421 * release our hold. We need to let it go even if we're a few levels
422 * deep in a recursive lock, and we need to restore that later.
423 *
424 * We append to the wait set ahead of clearing the count and owner
425 * fields so the subroutine can check that the calling thread owns
426 * the monitor. Aside from that, the order of member updates is
427 * not order sensitive as we hold the pthread mutex.
428 */
429 AppendToWaitSet(self);
430 int prevLockCount = lock_count_;
431 lock_count_ = 0;
432 owner_ = NULL;
jeffhao33dc7712011-11-09 17:54:24 -0800433 const Method* savedMethod = locking_method_;
434 locking_method_ = NULL;
Elliott Hughese65a6c92012-01-18 23:48:31 -0800435 uintptr_t savedPc = locking_pc_;
jeffhao33dc7712011-11-09 17:54:24 -0800436 locking_pc_ = 0;
Elliott Hughes5f791332011-09-15 17:45:30 -0700437
438 /*
439 * Update thread status. If the GC wakes up, it'll ignore us, knowing
440 * that we won't touch any references in this state, and we'll check
441 * our suspend mode before we transition out.
442 */
443 if (timed) {
444 self->SetState(Thread::kTimedWaiting);
445 } else {
446 self->SetState(Thread::kWaiting);
447 }
448
Elliott Hughes85d15452011-09-16 17:33:01 -0700449 self->wait_mutex_->Lock();
Elliott Hughes5f791332011-09-15 17:45:30 -0700450
451 /*
452 * Set wait_monitor_ to the monitor object we will be waiting on.
453 * When wait_monitor_ is non-NULL a notifying or interrupting thread
454 * must signal the thread's wait_cond_ to wake it up.
455 */
456 DCHECK(self->wait_monitor_ == NULL);
457 self->wait_monitor_ = this;
458
459 /*
460 * Handle the case where the thread was interrupted before we called
461 * wait().
462 */
463 bool wasInterrupted = false;
464 if (self->interrupted_) {
465 wasInterrupted = true;
466 self->wait_monitor_ = NULL;
Elliott Hughes85d15452011-09-16 17:33:01 -0700467 self->wait_mutex_->Unlock();
Elliott Hughes5f791332011-09-15 17:45:30 -0700468 goto done;
469 }
470
471 /*
472 * Release the monitor lock and wait for a notification or
473 * a timeout to occur.
474 */
475 lock_.Unlock();
476
477 if (!timed) {
Elliott Hughes85d15452011-09-16 17:33:01 -0700478 self->wait_cond_->Wait(*self->wait_mutex_);
Elliott Hughes5f791332011-09-15 17:45:30 -0700479 } else {
Elliott Hughes85d15452011-09-16 17:33:01 -0700480 self->wait_cond_->TimedWait(*self->wait_mutex_, ts);
Elliott Hughes5f791332011-09-15 17:45:30 -0700481 }
482 if (self->interrupted_) {
483 wasInterrupted = true;
484 }
485
486 self->interrupted_ = false;
487 self->wait_monitor_ = NULL;
Elliott Hughes85d15452011-09-16 17:33:01 -0700488 self->wait_mutex_->Unlock();
Elliott Hughes5f791332011-09-15 17:45:30 -0700489
490 // Reacquire the monitor lock.
491 Lock(self);
492
493done:
494 /*
495 * We remove our thread from wait set after restoring the count
496 * and owner fields so the subroutine can check that the calling
497 * thread owns the monitor. Aside from that, the order of member
498 * updates is not order sensitive as we hold the pthread mutex.
499 */
500 owner_ = self;
501 lock_count_ = prevLockCount;
jeffhao33dc7712011-11-09 17:54:24 -0800502 locking_method_ = savedMethod;
503 locking_pc_ = savedPc;
Elliott Hughes5f791332011-09-15 17:45:30 -0700504 RemoveFromWaitSet(self);
505
506 /* set self->status back to Thread::kRunnable, and self-suspend if needed */
507 self->SetState(Thread::kRunnable);
508
509 if (wasInterrupted) {
510 /*
511 * We were interrupted while waiting, or somebody interrupted an
512 * un-interruptible thread earlier and we're bailing out immediately.
513 *
514 * The doc sayeth: "The interrupted status of the current thread is
515 * cleared when this exception is thrown."
516 */
517 self->interrupted_ = false;
518 if (interruptShouldThrow) {
Elliott Hughes5cb5ad22011-10-02 12:13:39 -0700519 Thread::Current()->ThrowNewException("Ljava/lang/InterruptedException;", NULL);
Elliott Hughes5f791332011-09-15 17:45:30 -0700520 }
521 }
522}
523
524void Monitor::Notify(Thread* self) {
525 DCHECK(self != NULL);
526
527 // Make sure that we hold the lock.
528 if (owner_ != self) {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800529 ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()");
Elliott Hughes5f791332011-09-15 17:45:30 -0700530 return;
531 }
532 // Signal the first waiting thread in the wait set.
533 while (wait_set_ != NULL) {
534 Thread* thread = wait_set_;
535 wait_set_ = thread->wait_next_;
536 thread->wait_next_ = NULL;
537
538 // Check to see if the thread is still waiting.
Elliott Hughes85d15452011-09-16 17:33:01 -0700539 MutexLock mu(*thread->wait_mutex_);
Elliott Hughes5f791332011-09-15 17:45:30 -0700540 if (thread->wait_monitor_ != NULL) {
Elliott Hughes85d15452011-09-16 17:33:01 -0700541 thread->wait_cond_->Signal();
Elliott Hughes5f791332011-09-15 17:45:30 -0700542 return;
543 }
544 }
545}
546
547void Monitor::NotifyAll(Thread* self) {
548 DCHECK(self != NULL);
549
550 // Make sure that we hold the lock.
551 if (owner_ != self) {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800552 ThrowIllegalMonitorStateExceptionF("object not locked by thread before notifyAll()");
Elliott Hughes5f791332011-09-15 17:45:30 -0700553 return;
554 }
555 // Signal all threads in the wait set.
556 while (wait_set_ != NULL) {
557 Thread* thread = wait_set_;
558 wait_set_ = thread->wait_next_;
559 thread->wait_next_ = NULL;
560 thread->Notify();
561 }
562}
563
564/*
565 * Changes the shape of a monitor from thin to fat, preserving the
566 * internal lock state. The calling thread must own the lock.
567 */
568void Monitor::Inflate(Thread* self, Object* obj) {
569 DCHECK(self != NULL);
570 DCHECK(obj != NULL);
571 DCHECK_EQ(LW_SHAPE(*obj->GetRawLockWordAddress()), LW_SHAPE_THIN);
Elliott Hughesf8e01272011-10-17 11:29:05 -0700572 DCHECK_EQ(LW_LOCK_OWNER(*obj->GetRawLockWordAddress()), static_cast<int32_t>(self->GetThinLockId()));
Elliott Hughes5f791332011-09-15 17:45:30 -0700573
574 // Allocate and acquire a new monitor.
575 Monitor* m = new Monitor(obj);
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800576 VLOG(monitor) << "monitor: thread " << self->GetThinLockId()
577 << " created monitor " << m << " for object " << obj;
Elliott Hughesc33a32b2011-10-11 18:18:07 -0700578 Runtime::Current()->GetMonitorList()->Add(m);
Elliott Hughes5f791332011-09-15 17:45:30 -0700579 m->Lock(self);
580 // Propagate the lock state.
581 uint32_t thin = *obj->GetRawLockWordAddress();
582 m->lock_count_ = LW_LOCK_COUNT(thin);
583 thin &= LW_HASH_STATE_MASK << LW_HASH_STATE_SHIFT;
584 thin |= reinterpret_cast<uint32_t>(m) | LW_SHAPE_FAT;
585 // Publish the updated lock word.
586 android_atomic_release_store(thin, obj->GetRawLockWordAddress());
587}
588
589void Monitor::MonitorEnter(Thread* self, Object* obj) {
590 volatile int32_t* thinp = obj->GetRawLockWordAddress();
591 struct timespec tm;
Elliott Hughes398f64b2012-03-26 18:05:48 -0700592 uint32_t sleepDelayNs;
593 uint32_t minSleepDelayNs = 1000000; /* 1 millisecond */
594 uint32_t maxSleepDelayNs = 1000000000; /* 1 second */
Elliott Hughesf8e01272011-10-17 11:29:05 -0700595 uint32_t thin, newThin;
Elliott Hughes5f791332011-09-15 17:45:30 -0700596
Elliott Hughes4681c802011-09-25 18:04:37 -0700597 DCHECK(self != NULL);
598 DCHECK(obj != NULL);
Elliott Hughesf8e01272011-10-17 11:29:05 -0700599 uint32_t threadId = self->GetThinLockId();
Elliott Hughes5f791332011-09-15 17:45:30 -0700600retry:
601 thin = *thinp;
602 if (LW_SHAPE(thin) == LW_SHAPE_THIN) {
603 /*
604 * The lock is a thin lock. The owner field is used to
605 * determine the acquire method, ordered by cost.
606 */
607 if (LW_LOCK_OWNER(thin) == threadId) {
608 /*
609 * The calling thread owns the lock. Increment the
610 * value of the recursion count field.
611 */
612 *thinp += 1 << LW_LOCK_COUNT_SHIFT;
613 if (LW_LOCK_COUNT(*thinp) == LW_LOCK_COUNT_MASK) {
614 /*
615 * The reacquisition limit has been reached. Inflate
616 * the lock so the next acquire will not overflow the
617 * recursion count field.
618 */
619 Inflate(self, obj);
620 }
621 } else if (LW_LOCK_OWNER(thin) == 0) {
Elliott Hughes81ff3182012-03-23 20:35:56 -0700622 // The lock is unowned. Install the thread id of the calling thread into the owner field.
623 // This is the common case: compiled code will have tried this before calling back into
624 // the runtime.
Elliott Hughes5f791332011-09-15 17:45:30 -0700625 newThin = thin | (threadId << LW_LOCK_OWNER_SHIFT);
626 if (android_atomic_acquire_cas(thin, newThin, thinp) != 0) {
627 // The acquire failed. Try again.
628 goto retry;
629 }
630 } else {
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800631 VLOG(monitor) << StringPrintf("monitor: thread %d spin on lock %p (a %s) owned by %d",
Elliott Hughes81ff3182012-03-23 20:35:56 -0700632 threadId, thinp, PrettyTypeOf(obj).c_str(), LW_LOCK_OWNER(thin));
633 // The lock is owned by another thread. Notify the runtime that we are about to wait.
Elliott Hughes8e4aac52011-09-26 17:03:36 -0700634 self->monitor_enter_object_ = obj;
Elliott Hughes5f791332011-09-15 17:45:30 -0700635 Thread::State oldStatus = self->SetState(Thread::kBlocked);
636 // Spin until the thin lock is released or inflated.
637 sleepDelayNs = 0;
638 for (;;) {
639 thin = *thinp;
640 // Check the shape of the lock word. Another thread
641 // may have inflated the lock while we were waiting.
642 if (LW_SHAPE(thin) == LW_SHAPE_THIN) {
643 if (LW_LOCK_OWNER(thin) == 0) {
644 // The lock has been released. Install the thread id of the
645 // calling thread into the owner field.
646 newThin = thin | (threadId << LW_LOCK_OWNER_SHIFT);
647 if (android_atomic_acquire_cas(thin, newThin, thinp) == 0) {
648 // The acquire succeed. Break out of the loop and proceed to inflate the lock.
649 break;
650 }
651 } else {
652 // The lock has not been released. Yield so the owning thread can run.
653 if (sleepDelayNs == 0) {
654 sched_yield();
655 sleepDelayNs = minSleepDelayNs;
656 } else {
657 tm.tv_sec = 0;
658 tm.tv_nsec = sleepDelayNs;
659 nanosleep(&tm, NULL);
660 // Prepare the next delay value. Wrap to avoid once a second polls for eternity.
661 if (sleepDelayNs < maxSleepDelayNs / 2) {
662 sleepDelayNs *= 2;
663 } else {
664 sleepDelayNs = minSleepDelayNs;
665 }
666 }
667 }
668 } else {
Elliott Hughes81ff3182012-03-23 20:35:56 -0700669 // The thin lock was inflated by another thread. Let the runtime know we are no longer
Elliott Hughes5f791332011-09-15 17:45:30 -0700670 // waiting and try again.
Elliott Hughes398f64b2012-03-26 18:05:48 -0700671 VLOG(monitor) << StringPrintf("monitor: thread %d found lock %p surprise-fattened by another thread", threadId, thinp);
Elliott Hughes8e4aac52011-09-26 17:03:36 -0700672 self->monitor_enter_object_ = NULL;
Elliott Hughes5f791332011-09-15 17:45:30 -0700673 self->SetState(oldStatus);
674 goto retry;
675 }
676 }
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800677 VLOG(monitor) << StringPrintf("monitor: thread %d spin on lock %p done", threadId, thinp);
Elliott Hughes81ff3182012-03-23 20:35:56 -0700678 // We have acquired the thin lock. Let the runtime know that we are no longer waiting.
Elliott Hughes8e4aac52011-09-26 17:03:36 -0700679 self->monitor_enter_object_ = NULL;
Elliott Hughes5f791332011-09-15 17:45:30 -0700680 self->SetState(oldStatus);
681 // Fatten the lock.
682 Inflate(self, obj);
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800683 VLOG(monitor) << StringPrintf("monitor: thread %d fattened lock %p", threadId, thinp);
Elliott Hughes5f791332011-09-15 17:45:30 -0700684 }
685 } else {
686 // The lock is a fat lock.
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800687 VLOG(monitor) << StringPrintf("monitor: thread %d locking fat lock %p (%p) %p on a %s",
Elliott Hughes398f64b2012-03-26 18:05:48 -0700688 threadId, thinp, LW_MONITOR(*thinp),
689 reinterpret_cast<void*>(*thinp), PrettyTypeOf(obj).c_str());
Elliott Hughes5f791332011-09-15 17:45:30 -0700690 DCHECK(LW_MONITOR(*thinp) != NULL);
691 LW_MONITOR(*thinp)->Lock(self);
692 }
693}
694
695bool Monitor::MonitorExit(Thread* self, Object* obj) {
696 volatile int32_t* thinp = obj->GetRawLockWordAddress();
697
698 DCHECK(self != NULL);
Elliott Hughes4681c802011-09-25 18:04:37 -0700699 //DCHECK_EQ(self->GetState(), Thread::kRunnable);
Elliott Hughes5f791332011-09-15 17:45:30 -0700700 DCHECK(obj != NULL);
701
702 /*
703 * Cache the lock word as its value can change while we are
704 * examining its state.
705 */
706 uint32_t thin = *thinp;
707 if (LW_SHAPE(thin) == LW_SHAPE_THIN) {
708 /*
709 * The lock is thin. We must ensure that the lock is owned
710 * by the given thread before unlocking it.
711 */
Elliott Hughesf8e01272011-10-17 11:29:05 -0700712 if (LW_LOCK_OWNER(thin) == self->GetThinLockId()) {
Elliott Hughes5f791332011-09-15 17:45:30 -0700713 /*
714 * We are the lock owner. It is safe to update the lock
715 * without CAS as lock ownership guards the lock itself.
716 */
717 if (LW_LOCK_COUNT(thin) == 0) {
718 /*
719 * The lock was not recursively acquired, the common
720 * case. Unlock by clearing all bits except for the
721 * hash state.
722 */
723 thin &= (LW_HASH_STATE_MASK << LW_HASH_STATE_SHIFT);
724 android_atomic_release_store(thin, thinp);
725 } else {
726 /*
727 * The object was recursively acquired. Decrement the
728 * lock recursion count field.
729 */
730 *thinp -= 1 << LW_LOCK_COUNT_SHIFT;
731 }
732 } else {
733 /*
734 * We do not own the lock. The JVM spec requires that we
735 * throw an exception in this case.
736 */
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800737 FailedUnlock(obj, self, NULL, NULL);
Elliott Hughes5f791332011-09-15 17:45:30 -0700738 return false;
739 }
740 } else {
741 /*
742 * The lock is fat. We must check to see if Unlock has
743 * raised any exceptions before continuing.
744 */
745 DCHECK(LW_MONITOR(*thinp) != NULL);
746 if (!LW_MONITOR(*thinp)->Unlock(self)) {
747 // An exception has been raised. Do not fall through.
748 return false;
749 }
750 }
751 return true;
752}
753
754/*
755 * Object.wait(). Also called for class init.
756 */
757void Monitor::Wait(Thread* self, Object *obj, int64_t ms, int32_t ns, bool interruptShouldThrow) {
758 volatile int32_t* thinp = obj->GetRawLockWordAddress();
759
760 // If the lock is still thin, we need to fatten it.
761 uint32_t thin = *thinp;
762 if (LW_SHAPE(thin) == LW_SHAPE_THIN) {
763 // Make sure that 'self' holds the lock.
Elliott Hughesf8e01272011-10-17 11:29:05 -0700764 if (LW_LOCK_OWNER(thin) != self->GetThinLockId()) {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800765 ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()");
Elliott Hughes5f791332011-09-15 17:45:30 -0700766 return;
767 }
768
769 /* This thread holds the lock. We need to fatten the lock
770 * so 'self' can block on it. Don't update the object lock
771 * field yet, because 'self' needs to acquire the lock before
772 * any other thread gets a chance.
773 */
774 Inflate(self, obj);
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800775 VLOG(monitor) << StringPrintf("monitor: thread %d fattened lock %p by wait()", self->GetThinLockId(), thinp);
Elliott Hughes5f791332011-09-15 17:45:30 -0700776 }
777 LW_MONITOR(*thinp)->Wait(self, ms, ns, interruptShouldThrow);
778}
779
780void Monitor::Notify(Thread* self, Object *obj) {
781 uint32_t thin = *obj->GetRawLockWordAddress();
782
783 // If the lock is still thin, there aren't any waiters;
784 // waiting on an object forces lock fattening.
785 if (LW_SHAPE(thin) == LW_SHAPE_THIN) {
786 // Make sure that 'self' holds the lock.
Elliott Hughesf8e01272011-10-17 11:29:05 -0700787 if (LW_LOCK_OWNER(thin) != self->GetThinLockId()) {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800788 ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()");
Elliott Hughes5f791332011-09-15 17:45:30 -0700789 return;
790 }
791 // no-op; there are no waiters to notify.
792 } else {
793 // It's a fat lock.
794 LW_MONITOR(thin)->Notify(self);
795 }
796}
797
798void Monitor::NotifyAll(Thread* self, Object *obj) {
799 uint32_t thin = *obj->GetRawLockWordAddress();
800
801 // If the lock is still thin, there aren't any waiters;
802 // waiting on an object forces lock fattening.
803 if (LW_SHAPE(thin) == LW_SHAPE_THIN) {
804 // Make sure that 'self' holds the lock.
Elliott Hughesf8e01272011-10-17 11:29:05 -0700805 if (LW_LOCK_OWNER(thin) != self->GetThinLockId()) {
Ian Rogers6d0b13e2012-02-07 09:25:29 -0800806 ThrowIllegalMonitorStateExceptionF("object not locked by thread before notifyAll()");
Elliott Hughes5f791332011-09-15 17:45:30 -0700807 return;
808 }
809 // no-op; there are no waiters to notify.
810 } else {
811 // It's a fat lock.
812 LW_MONITOR(thin)->NotifyAll(self);
813 }
814}
815
Brian Carlstrom24a3c2e2011-10-17 18:07:52 -0700816uint32_t Monitor::GetThinLockId(uint32_t raw_lock_word) {
Elliott Hughes5f791332011-09-15 17:45:30 -0700817 if (LW_SHAPE(raw_lock_word) == LW_SHAPE_THIN) {
818 return LW_LOCK_OWNER(raw_lock_word);
819 } else {
820 Thread* owner = LW_MONITOR(raw_lock_word)->owner_;
821 return owner ? owner->GetThinLockId() : 0;
822 }
823}
824
Elliott Hughes8e4aac52011-09-26 17:03:36 -0700825void Monitor::DescribeWait(std::ostream& os, const Thread* thread) {
826 Thread::State state = thread->GetState();
827
828 Object* object = NULL;
829 uint32_t lock_owner = ThreadList::kInvalidId;
830 if (state == Thread::kWaiting || state == Thread::kTimedWaiting) {
831 os << " - waiting on ";
832 Monitor* monitor = thread->wait_monitor_;
833 if (monitor != NULL) {
834 object = monitor->obj_;
835 }
836 lock_owner = Thread::LockOwnerFromThreadLock(object);
837 } else if (state == Thread::kBlocked) {
838 os << " - waiting to lock ";
839 object = thread->monitor_enter_object_;
840 if (object != NULL) {
Brian Carlstrom24a3c2e2011-10-17 18:07:52 -0700841 lock_owner = object->GetThinLockId();
Elliott Hughes8e4aac52011-09-26 17:03:36 -0700842 }
843 } else {
844 // We're not waiting on anything.
845 return;
846 }
847 os << "<" << object << ">";
848
849 // - waiting on <0x613f83d8> (a java.lang.ThreadLock) held by thread 5
850 // - waiting on <0x6008c468> (a java.lang.Class<java.lang.ref.ReferenceQueue>)
851 os << " (a " << PrettyTypeOf(object) << ")";
852
853 if (lock_owner != ThreadList::kInvalidId) {
854 os << " held by thread " << lock_owner;
855 }
856
857 os << "\n";
858}
859
jeffhao33dc7712011-11-09 17:54:24 -0800860void Monitor::TranslateLocation(const Method* method, uint32_t pc,
861 const char*& source_file, uint32_t& line_number) const {
862 // If method is null, location is unknown
863 if (method == NULL) {
Elliott Hughes12c51e32012-01-17 20:25:05 -0800864 source_file = "";
jeffhao33dc7712011-11-09 17:54:24 -0800865 line_number = 0;
866 return;
867 }
Ian Rogers6d4d9fc2011-11-30 16:24:48 -0800868 MethodHelper mh(method);
869 source_file = mh.GetDeclaringClassSourceFile();
Elliott Hughes12c51e32012-01-17 20:25:05 -0800870 if (source_file == NULL) {
871 source_file = "";
872 }
Ian Rogers6d4d9fc2011-11-30 16:24:48 -0800873 line_number = mh.GetLineNumFromNativePC(pc);
jeffhao33dc7712011-11-09 17:54:24 -0800874}
875
Elliott Hughesc33a32b2011-10-11 18:18:07 -0700876MonitorList::MonitorList() : lock_("MonitorList lock") {
877}
878
879MonitorList::~MonitorList() {
880 MutexLock mu(lock_);
881 STLDeleteElements(&list_);
882}
883
884void MonitorList::Add(Monitor* m) {
885 MutexLock mu(lock_);
886 list_.push_front(m);
887}
888
889void MonitorList::SweepMonitorList(Heap::IsMarkedTester is_marked, void* arg) {
890 MutexLock mu(lock_);
891 typedef std::list<Monitor*>::iterator It; // TODO: C++0x auto
892 It it = list_.begin();
893 while (it != list_.end()) {
894 Monitor* m = *it;
895 if (!is_marked(m->GetObject(), arg)) {
Elliott Hughes4dd9b4d2011-12-12 18:29:24 -0800896 VLOG(monitor) << "freeing monitor " << m << " belonging to unmarked object " << m->GetObject();
Elliott Hughesc33a32b2011-10-11 18:18:07 -0700897 delete m;
898 it = list_.erase(it);
899 } else {
900 ++it;
901 }
902 }
903}
904
Elliott Hughes5f791332011-09-15 17:45:30 -0700905} // namespace art