1 /*
2 * Copyright (C) 2011 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
17 #ifndef ART_RUNTIME_BASE_MUTEX_INL_H_
18 #define ART_RUNTIME_BASE_MUTEX_INL_H_
19
20 #include <inttypes.h>
21
22 #include "mutex.h"
23
24 #include "base/stringprintf.h"
25 #include "base/value_object.h"
26 #include "runtime.h"
27 #include "thread.h"
28 #include "utils.h"
29
30 #if ART_USE_FUTEXES
31 #include "linux/futex.h"
32 #include "sys/syscall.h"
33 #ifndef SYS_futex
34 #define SYS_futex __NR_futex
35 #endif
36 #endif // ART_USE_FUTEXES
37
38 #define CHECK_MUTEX_CALL(call, args) CHECK_PTHREAD_CALL(call, args, name_)
39
40 namespace art {
41
42 #if ART_USE_FUTEXES
futex(volatile int * uaddr,int op,int val,const struct timespec * timeout,volatile int * uaddr2,int val3)43 static inline int futex(volatile int *uaddr, int op, int val, const struct timespec *timeout,
44 volatile int *uaddr2, int val3) {
45 return syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
46 }
47 #endif // ART_USE_FUTEXES
48
SafeGetTid(const Thread * self)49 static inline uint64_t SafeGetTid(const Thread* self) {
50 if (self != nullptr) {
51 return static_cast<uint64_t>(self->GetTid());
52 } else {
53 return static_cast<uint64_t>(GetTid());
54 }
55 }
56
CheckUnattachedThread(LockLevel level)57 static inline void CheckUnattachedThread(LockLevel level) NO_THREAD_SAFETY_ANALYSIS {
58 // The check below enumerates the cases where we expect not to be able to sanity check locks
59 // on a thread. Lock checking is disabled to avoid deadlock when checking shutdown lock.
60 // TODO: tighten this check.
61 if (kDebugLocking) {
62 Runtime* runtime = Runtime::Current();
63 CHECK(runtime == nullptr || !runtime->IsStarted() || runtime->IsShuttingDownLocked() ||
64 // Used during thread creation to avoid races with runtime shutdown. Thread::Current not
65 // yet established.
66 level == kRuntimeShutdownLock ||
67 // Thread Ids are allocated/released before threads are established.
68 level == kAllocatedThreadIdsLock ||
69 // Thread LDT's are initialized without Thread::Current established.
70 level == kModifyLdtLock ||
71 // Threads are unregistered while holding the thread list lock, during this process they
72 // no longer exist and so we expect an unlock with no self.
73 level == kThreadListLock ||
74 // Ignore logging which may or may not have set up thread data structures.
75 level == kLoggingLock ||
76 // Avoid recursive death.
77 level == kAbortLock) << level;
78 }
79 }
80
RegisterAsLocked(Thread * self)81 inline void BaseMutex::RegisterAsLocked(Thread* self) {
82 if (UNLIKELY(self == nullptr)) {
83 CheckUnattachedThread(level_);
84 return;
85 }
86 if (kDebugLocking) {
87 // Check if a bad Mutex of this level or lower is held.
88 bool bad_mutexes_held = false;
89 for (int i = level_; i >= 0; --i) {
90 BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
91 if (UNLIKELY(held_mutex != nullptr)) {
92 LOG(ERROR) << "Lock level violation: holding \"" << held_mutex->name_ << "\" "
93 << "(level " << LockLevel(i) << " - " << i
94 << ") while locking \"" << name_ << "\" "
95 << "(level " << level_ << " - " << static_cast<int>(level_) << ")";
96 if (i > kAbortLock) {
97 // Only abort in the check below if this is more than abort level lock.
98 bad_mutexes_held = true;
99 }
100 }
101 }
102 if (gAborting == 0) { // Avoid recursive aborts.
103 CHECK(!bad_mutexes_held);
104 }
105 }
106 // Don't record monitors as they are outside the scope of analysis. They may be inspected off of
107 // the monitor list.
108 if (level_ != kMonitorLock) {
109 self->SetHeldMutex(level_, this);
110 }
111 }
112
RegisterAsUnlocked(Thread * self)113 inline void BaseMutex::RegisterAsUnlocked(Thread* self) {
114 if (UNLIKELY(self == nullptr)) {
115 CheckUnattachedThread(level_);
116 return;
117 }
118 if (level_ != kMonitorLock) {
119 if (kDebugLocking && gAborting == 0) { // Avoid recursive aborts.
120 CHECK(self->GetHeldMutex(level_) == this) << "Unlocking on unacquired mutex: " << name_;
121 }
122 self->SetHeldMutex(level_, nullptr);
123 }
124 }
125
SharedLock(Thread * self)126 inline void ReaderWriterMutex::SharedLock(Thread* self) {
127 DCHECK(self == nullptr || self == Thread::Current());
128 #if ART_USE_FUTEXES
129 bool done = false;
130 do {
131 int32_t cur_state = state_.LoadRelaxed();
132 if (LIKELY(cur_state >= 0)) {
133 // Add as an extra reader.
134 done = state_.CompareExchangeWeakAcquire(cur_state, cur_state + 1);
135 } else {
136 HandleSharedLockContention(self, cur_state);
137 }
138 } while (!done);
139 #else
140 CHECK_MUTEX_CALL(pthread_rwlock_rdlock, (&rwlock_));
141 #endif
142 DCHECK(exclusive_owner_ == 0U || exclusive_owner_ == -1U);
143 RegisterAsLocked(self);
144 AssertSharedHeld(self);
145 }
146
SharedUnlock(Thread * self)147 inline void ReaderWriterMutex::SharedUnlock(Thread* self) {
148 DCHECK(self == nullptr || self == Thread::Current());
149 DCHECK(exclusive_owner_ == 0U || exclusive_owner_ == -1U);
150 AssertSharedHeld(self);
151 RegisterAsUnlocked(self);
152 #if ART_USE_FUTEXES
153 bool done = false;
154 do {
155 int32_t cur_state = state_.LoadRelaxed();
156 if (LIKELY(cur_state > 0)) {
157 // Reduce state by 1 and impose lock release load/store ordering.
158 // Note, the relaxed loads below musn't reorder before the CompareExchange.
159 // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
160 // a status bit into the state on contention.
161 done = state_.CompareExchangeWeakSequentiallyConsistent(cur_state, cur_state - 1);
162 if (done && (cur_state - 1) == 0) { // Weak CAS may fail spuriously.
163 if (num_pending_writers_.LoadRelaxed() > 0 ||
164 num_pending_readers_.LoadRelaxed() > 0) {
165 // Wake any exclusive waiters as there are now no readers.
166 futex(state_.Address(), FUTEX_WAKE, -1, nullptr, nullptr, 0);
167 }
168 }
169 } else {
170 LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
171 }
172 } while (!done);
173 #else
174 CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
175 #endif
176 }
177
IsExclusiveHeld(const Thread * self)178 inline bool Mutex::IsExclusiveHeld(const Thread* self) const {
179 DCHECK(self == nullptr || self == Thread::Current());
180 bool result = (GetExclusiveOwnerTid() == SafeGetTid(self));
181 if (kDebugLocking) {
182 // Sanity debug check that if we think it is locked we have it in our held mutexes.
183 if (result && self != nullptr && level_ != kMonitorLock && !gAborting) {
184 CHECK_EQ(self->GetHeldMutex(level_), this);
185 }
186 }
187 return result;
188 }
189
GetExclusiveOwnerTid()190 inline uint64_t Mutex::GetExclusiveOwnerTid() const {
191 return exclusive_owner_;
192 }
193
IsExclusiveHeld(const Thread * self)194 inline bool ReaderWriterMutex::IsExclusiveHeld(const Thread* self) const {
195 DCHECK(self == nullptr || self == Thread::Current());
196 bool result = (GetExclusiveOwnerTid() == SafeGetTid(self));
197 if (kDebugLocking) {
198 // Sanity that if the pthread thinks we own the lock the Thread agrees.
199 if (self != nullptr && result) {
200 CHECK_EQ(self->GetHeldMutex(level_), this);
201 }
202 }
203 return result;
204 }
205
GetExclusiveOwnerTid()206 inline uint64_t ReaderWriterMutex::GetExclusiveOwnerTid() const {
207 #if ART_USE_FUTEXES
208 int32_t state = state_.LoadRelaxed();
209 if (state == 0) {
210 return 0; // No owner.
211 } else if (state > 0) {
212 return -1; // Shared.
213 } else {
214 return exclusive_owner_;
215 }
216 #else
217 return exclusive_owner_;
218 #endif
219 }
220
221 } // namespace art
222
223 #endif // ART_RUNTIME_BASE_MUTEX_INL_H_
224