1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <pthread.h> 30 31 #include <errno.h> 32 #include <limits.h> 33 #include <sys/mman.h> 34 #include <time.h> 35 #include <unistd.h> 36 37 #include "pthread_internal.h" 38 39 #include "private/bionic_atomic_inline.h" 40 #include "private/bionic_futex.h" 41 #include "private/bionic_time_conversions.h" 42 #include "private/bionic_tls.h" 43 44 // We use one bit in pthread_condattr_t (long) values as the 'shared' flag 45 // and one bit for the clock type (CLOCK_REALTIME is ((clockid_t) 1), and 46 // CLOCK_MONOTONIC is ((clockid_t) 0).). The rest of the bits are a counter. 47 // 48 // The 'value' field pthread_cond_t has the same layout. 49 50 #define COND_SHARED_MASK 0x0001 51 #define COND_CLOCK_MASK 0x0002 52 #define COND_COUNTER_STEP 0x0004 53 #define COND_FLAGS_MASK (COND_SHARED_MASK | COND_CLOCK_MASK) 54 #define COND_COUNTER_MASK (~COND_FLAGS_MASK) 55 56 #define COND_IS_SHARED(c) (((c) & COND_SHARED_MASK) != 0) 57 #define COND_GET_CLOCK(c) (((c) & COND_CLOCK_MASK) >> 1) 58 #define COND_SET_CLOCK(attr, c) ((attr) | (c << 1)) 59 60 61 int pthread_condattr_init(pthread_condattr_t* attr) { 62 *attr = 0; 63 *attr |= PTHREAD_PROCESS_PRIVATE; 64 *attr |= (CLOCK_REALTIME << 1); 65 return 0; 66 } 67 68 int pthread_condattr_getpshared(const pthread_condattr_t* attr, int* pshared) { 69 *pshared = static_cast<int>(COND_IS_SHARED(*attr)); 70 return 0; 71 } 72 73 int pthread_condattr_setpshared(pthread_condattr_t* attr, int pshared) { 74 if (pshared != PTHREAD_PROCESS_SHARED && pshared != PTHREAD_PROCESS_PRIVATE) { 75 return EINVAL; 76 } 77 78 *attr |= pshared; 79 return 0; 80 } 81 82 int pthread_condattr_getclock(const pthread_condattr_t* attr, clockid_t* clock) { 83 *clock = COND_GET_CLOCK(*attr); 84 return 0; 85 } 86 87 int pthread_condattr_setclock(pthread_condattr_t* attr, clockid_t clock) { 88 if (clock != CLOCK_MONOTONIC && clock != CLOCK_REALTIME) { 89 return EINVAL; 90 } 91 92 *attr = COND_SET_CLOCK(*attr, clock); 93 return 0; 94 } 95 96 int pthread_condattr_destroy(pthread_condattr_t* attr) { 97 *attr = 0xdeada11d; 98 return 0; 99 } 100 101 102 // XXX *technically* there is a race condition that could allow 103 // XXX a signal to be missed. If thread A is preempted in _wait() 104 // XXX after unlocking the mutex and before waiting, and if other 105 // XXX threads call signal or broadcast UINT_MAX/2 times (exactly), 106 // XXX before thread A is scheduled again and calls futex_wait(), 107 // XXX then the signal will be lost. 108 109 int pthread_cond_init(pthread_cond_t* cond, const pthread_condattr_t* attr) { 110 if (attr != NULL) { 111 cond->value = (*attr & COND_FLAGS_MASK); 112 } else { 113 cond->value = 0; 114 } 115 116 return 0; 117 } 118 119 int pthread_cond_destroy(pthread_cond_t* cond) { 120 cond->value = 0xdeadc04d; 121 return 0; 122 } 123 124 // This function is used by pthread_cond_broadcast and 125 // pthread_cond_signal to atomically decrement the counter 126 // then wake up 'counter' threads. 127 static int __pthread_cond_pulse(pthread_cond_t* cond, int counter) { 128 int flags = (cond->value & COND_FLAGS_MASK); 129 while (true) { 130 int old_value = cond->value; 131 int new_value = ((old_value - COND_COUNTER_STEP) & COND_COUNTER_MASK) | flags; 132 if (__bionic_cmpxchg(old_value, new_value, &cond->value) == 0) { 133 break; 134 } 135 } 136 137 // Ensure that all memory accesses previously made by this thread are 138 // visible to the woken thread(s). On the other side, the "wait" 139 // code will issue any necessary barriers when locking the mutex. 140 // 141 // This may not strictly be necessary -- if the caller follows 142 // recommended practice and holds the mutex before signaling the cond 143 // var, the mutex ops will provide correct semantics. If they don't 144 // hold the mutex, they're subject to race conditions anyway. 145 ANDROID_MEMBAR_FULL(); 146 147 __futex_wake_ex(&cond->value, COND_IS_SHARED(cond->value), counter); 148 return 0; 149 } 150 151 __LIBC_HIDDEN__ 152 int __pthread_cond_timedwait_relative(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* reltime) { 153 int old_value = cond->value; 154 155 pthread_mutex_unlock(mutex); 156 int status = __futex_wait_ex(&cond->value, COND_IS_SHARED(cond->value), old_value, reltime); 157 pthread_mutex_lock(mutex); 158 159 if (status == -ETIMEDOUT) { 160 return ETIMEDOUT; 161 } 162 return 0; 163 } 164 165 __LIBC_HIDDEN__ 166 int __pthread_cond_timedwait(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime, clockid_t clock) { 167 timespec ts; 168 timespec* tsp; 169 170 if (abstime != NULL) { 171 if (__timespec_from_absolute(&ts, abstime, clock) < 0) { 172 return ETIMEDOUT; 173 } 174 tsp = &ts; 175 } else { 176 tsp = NULL; 177 } 178 179 return __pthread_cond_timedwait_relative(cond, mutex, tsp); 180 } 181 182 int pthread_cond_broadcast(pthread_cond_t* cond) { 183 return __pthread_cond_pulse(cond, INT_MAX); 184 } 185 186 int pthread_cond_signal(pthread_cond_t* cond) { 187 return __pthread_cond_pulse(cond, 1); 188 } 189 190 int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex) { 191 return __pthread_cond_timedwait(cond, mutex, NULL, COND_GET_CLOCK(cond->value)); 192 } 193 194 int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t * mutex, const timespec *abstime) { 195 return __pthread_cond_timedwait(cond, mutex, abstime, COND_GET_CLOCK(cond->value)); 196 } 197 198 #if !defined(__LP64__) 199 // TODO: this exists only for backward binary compatibility on 32 bit platforms. 200 extern "C" int pthread_cond_timedwait_monotonic(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) { 201 return __pthread_cond_timedwait(cond, mutex, abstime, CLOCK_MONOTONIC); 202 } 203 204 extern "C" int pthread_cond_timedwait_monotonic_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) { 205 return __pthread_cond_timedwait(cond, mutex, abstime, CLOCK_MONOTONIC); 206 } 207 208 extern "C" int pthread_cond_timedwait_relative_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* reltime) { 209 return __pthread_cond_timedwait_relative(cond, mutex, reltime); 210 } 211 212 extern "C" int pthread_cond_timeout_np(pthread_cond_t* cond, pthread_mutex_t* mutex, unsigned ms) { 213 timespec ts; 214 timespec_from_ms(ts, ms); 215 return __pthread_cond_timedwait_relative(cond, mutex, &ts); 216 } 217 #endif // !defined(__LP64__) 218
