| /* |
| * Copyright (C) 2008 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include <pthread.h> |
| |
| #include <errno.h> |
| #include <limits.h> |
| #include <stdatomic.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/cdefs.h> |
| #include <sys/mman.h> |
| #include <unistd.h> |
| |
| #include "pthread_internal.h" |
| |
| #include "private/bionic_constants.h" |
| #include "private/bionic_fortify.h" |
| #include "private/bionic_futex.h" |
| #include "private/bionic_systrace.h" |
| #include "private/bionic_time_conversions.h" |
| #include "private/bionic_tls.h" |
| |
| /* a mutex attribute holds the following fields |
| * |
| * bits: name description |
| * 0-3 type type of mutex |
| * 4 shared process-shared flag |
| * 5 protocol whether it is a priority inherit mutex. |
| */ |
| #define MUTEXATTR_TYPE_MASK 0x000f |
| #define MUTEXATTR_SHARED_MASK 0x0010 |
| #define MUTEXATTR_PROTOCOL_MASK 0x0020 |
| |
| #define MUTEXATTR_PROTOCOL_SHIFT 5 |
| |
| int pthread_mutexattr_init(pthread_mutexattr_t *attr) |
| { |
| *attr = PTHREAD_MUTEX_DEFAULT; |
| return 0; |
| } |
| |
| int pthread_mutexattr_destroy(pthread_mutexattr_t *attr) |
| { |
| *attr = -1; |
| return 0; |
| } |
| |
| int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type_p) |
| { |
| int type = (*attr & MUTEXATTR_TYPE_MASK); |
| |
| if (type < PTHREAD_MUTEX_NORMAL || type > PTHREAD_MUTEX_ERRORCHECK) { |
| return EINVAL; |
| } |
| |
| *type_p = type; |
| return 0; |
| } |
| |
| int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type) |
| { |
| if (type < PTHREAD_MUTEX_NORMAL || type > PTHREAD_MUTEX_ERRORCHECK ) { |
| return EINVAL; |
| } |
| |
| *attr = (*attr & ~MUTEXATTR_TYPE_MASK) | type; |
| return 0; |
| } |
| |
| /* process-shared mutexes are not supported at the moment */ |
| |
| int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared) |
| { |
| switch (pshared) { |
| case PTHREAD_PROCESS_PRIVATE: |
| *attr &= ~MUTEXATTR_SHARED_MASK; |
| return 0; |
| |
| case PTHREAD_PROCESS_SHARED: |
| /* our current implementation of pthread actually supports shared |
| * mutexes but won't cleanup if a process dies with the mutex held. |
| * Nevertheless, it's better than nothing. Shared mutexes are used |
| * by surfaceflinger and audioflinger. |
| */ |
| *attr |= MUTEXATTR_SHARED_MASK; |
| return 0; |
| } |
| return EINVAL; |
| } |
| |
| int pthread_mutexattr_getpshared(const pthread_mutexattr_t* attr, int* pshared) { |
| *pshared = (*attr & MUTEXATTR_SHARED_MASK) ? PTHREAD_PROCESS_SHARED : PTHREAD_PROCESS_PRIVATE; |
| return 0; |
| } |
| |
| int pthread_mutexattr_setprotocol(pthread_mutexattr_t* attr, int protocol) { |
| if (protocol != PTHREAD_PRIO_NONE && protocol != PTHREAD_PRIO_INHERIT) { |
| return EINVAL; |
| } |
| *attr = (*attr & ~MUTEXATTR_PROTOCOL_MASK) | (protocol << MUTEXATTR_PROTOCOL_SHIFT); |
| return 0; |
| } |
| |
| int pthread_mutexattr_getprotocol(const pthread_mutexattr_t* attr, int* protocol) { |
| *protocol = (*attr & MUTEXATTR_PROTOCOL_MASK) >> MUTEXATTR_PROTOCOL_SHIFT; |
| return 0; |
| } |
| |
| // Priority Inheritance mutex implementation |
| struct PIMutex { |
| // mutex type, can be 0 (normal), 1 (recursive), 2 (errorcheck), constant during lifetime |
| uint8_t type; |
| // process-shared flag, constant during lifetime |
| bool shared; |
| // <number of times a thread holding a recursive PI mutex> - 1 |
| uint16_t counter; |
| // owner_tid is read/written by both userspace code and kernel code. It includes three fields: |
| // FUTEX_WAITERS, FUTEX_OWNER_DIED and FUTEX_TID_MASK. |
| atomic_int owner_tid; |
| }; |
| |
| static inline __always_inline int PIMutexTryLock(PIMutex& mutex) { |
| pid_t tid = __get_thread()->tid; |
| // Handle common case first. |
| int old_owner = 0; |
| if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex.owner_tid, |
| &old_owner, tid, |
| memory_order_acquire, |
| memory_order_relaxed))) { |
| return 0; |
| } |
| if (tid == (old_owner & FUTEX_TID_MASK)) { |
| // We already own this mutex. |
| if (mutex.type == PTHREAD_MUTEX_NORMAL) { |
| return EBUSY; |
| } |
| if (mutex.type == PTHREAD_MUTEX_ERRORCHECK) { |
| return EDEADLK; |
| } |
| if (mutex.counter == 0xffff) { |
| return EAGAIN; |
| } |
| mutex.counter++; |
| return 0; |
| } |
| return EBUSY; |
| } |
| |
| // Inlining this function in pthread_mutex_lock() adds the cost of stack frame instructions on |
| // ARM/ARM64, which increases at most 20 percent overhead. So make it noinline. |
| static int __attribute__((noinline)) PIMutexTimedLock(PIMutex& mutex, |
| bool use_realtime_clock, |
| const timespec* abs_timeout) { |
| int ret = PIMutexTryLock(mutex); |
| if (__predict_true(ret == 0)) { |
| return 0; |
| } |
| if (ret == EBUSY) { |
| ScopedTrace trace("Contending for pthread mutex"); |
| ret = -__futex_pi_lock_ex(&mutex.owner_tid, mutex.shared, use_realtime_clock, abs_timeout); |
| } |
| return ret; |
| } |
| |
| static int PIMutexUnlock(PIMutex& mutex) { |
| pid_t tid = __get_thread()->tid; |
| int old_owner = tid; |
| // Handle common case first. |
| if (__predict_true(mutex.type == PTHREAD_MUTEX_NORMAL)) { |
| if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex.owner_tid, |
| &old_owner, 0, |
| memory_order_release, |
| memory_order_relaxed))) { |
| return 0; |
| } |
| } else { |
| old_owner = atomic_load_explicit(&mutex.owner_tid, memory_order_relaxed); |
| } |
| |
| if (tid != (old_owner & FUTEX_TID_MASK)) { |
| // The mutex can only be unlocked by the thread who owns it. |
| return EPERM; |
| } |
| if (mutex.type == PTHREAD_MUTEX_RECURSIVE) { |
| if (mutex.counter != 0u) { |
| --mutex.counter; |
| return 0; |
| } |
| } |
| if (old_owner == tid) { |
| // No thread is waiting. |
| if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex.owner_tid, |
| &old_owner, 0, |
| memory_order_release, |
| memory_order_relaxed))) { |
| return 0; |
| } |
| } |
| return -__futex_pi_unlock(&mutex.owner_tid, mutex.shared); |
| } |
| |
| static int PIMutexDestroy(PIMutex& mutex) { |
| // The mutex should be in unlocked state (owner_tid == 0) when destroyed. |
| // Store 0xffffffff to make the mutex unusable. |
| int old_owner = 0; |
| if (atomic_compare_exchange_strong_explicit(&mutex.owner_tid, &old_owner, 0xffffffff, |
| memory_order_relaxed, memory_order_relaxed)) { |
| return 0; |
| } |
| return EBUSY; |
| } |
| |
| #if !defined(__LP64__) |
| |
| namespace PIMutexAllocator { |
| // pthread_mutex_t has only 4 bytes in 32-bit programs, which are not enough to hold PIMutex. |
| // So we use malloc to allocate PIMutexes and use 16-bit of pthread_mutex_t as indexes to find |
| // the allocated PIMutexes. This allows at most 65536 PI mutexes. |
| // When calling operations like pthread_mutex_lock/unlock, the 16-bit index is mapped to the |
| // corresponding PIMutex. To make the map operation fast, we use a lockless mapping method: |
| // Once a PIMutex is allocated, all the data used to map index to the PIMutex isn't changed until |
| // it is destroyed. |
| // Below are the data structures: |
| // // struct Node contains a PIMutex. |
| // typedef Node NodeArray[256]; |
| // typedef NodeArray* NodeArrayP; |
| // NodeArrayP nodes[256]; |
| // |
| // A 16-bit index is mapped to Node as below: |
| // (*nodes[index >> 8])[index & 0xff] |
| // |
| // Also use a free list to allow O(1) finding recycled PIMutexes. |
| |
| union Node { |
| PIMutex mutex; |
| int next_free_id; // If not -1, refer to the next node in the free PIMutex list. |
| }; |
| typedef Node NodeArray[256]; |
| typedef NodeArray* NodeArrayP; |
| |
| // lock_ protects below items. |
| static Lock lock; |
| static NodeArrayP* nodes; |
| static int next_to_alloc_id; |
| static int first_free_id = -1; // If not -1, refer to the first node in the free PIMutex list. |
| |
| static inline __always_inline Node& IdToNode(int id) { |
| return (*nodes[id >> 8])[id & 0xff]; |
| } |
| |
| static inline __always_inline PIMutex& IdToPIMutex(int id) { |
| return IdToNode(id).mutex; |
| } |
| |
| static int AllocIdLocked() { |
| if (first_free_id != -1) { |
| int result = first_free_id; |
| first_free_id = IdToNode(result).next_free_id; |
| return result; |
| } |
| if (next_to_alloc_id >= 0x10000) { |
| return -1; |
| } |
| int array_pos = next_to_alloc_id >> 8; |
| int node_pos = next_to_alloc_id & 0xff; |
| if (node_pos == 0) { |
| if (array_pos == 0) { |
| nodes = static_cast<NodeArray**>(calloc(256, sizeof(NodeArray*))); |
| if (nodes == nullptr) { |
| return -1; |
| } |
| } |
| nodes[array_pos] = static_cast<NodeArray*>(malloc(sizeof(NodeArray))); |
| if (nodes[array_pos] == nullptr) { |
| return -1; |
| } |
| } |
| return next_to_alloc_id++; |
| } |
| |
| // If succeed, return an id referring to a PIMutex, otherwise return -1. |
| // A valid id is in range [0, 0xffff]. |
| static int AllocId() { |
| lock.lock(); |
| int result = AllocIdLocked(); |
| lock.unlock(); |
| if (result != -1) { |
| memset(&IdToPIMutex(result), 0, sizeof(PIMutex)); |
| } |
| return result; |
| } |
| |
| static void FreeId(int id) { |
| lock.lock(); |
| IdToNode(id).next_free_id = first_free_id; |
| first_free_id = id; |
| lock.unlock(); |
| } |
| |
| } // namespace PIMutexAllocator |
| |
| #endif // !defined(__LP64__) |
| |
| |
| /* Convenience macro, creates a mask of 'bits' bits that starts from |
| * the 'shift'-th least significant bit in a 32-bit word. |
| * |
| * Examples: FIELD_MASK(0,4) -> 0xf |
| * FIELD_MASK(16,9) -> 0x1ff0000 |
| */ |
| #define FIELD_MASK(shift,bits) (((1 << (bits))-1) << (shift)) |
| |
| /* This one is used to create a bit pattern from a given field value */ |
| #define FIELD_TO_BITS(val,shift,bits) (((val) & ((1 << (bits))-1)) << (shift)) |
| |
| /* And this one does the opposite, i.e. extract a field's value from a bit pattern */ |
| #define FIELD_FROM_BITS(val,shift,bits) (((val) >> (shift)) & ((1 << (bits))-1)) |
| |
| /* Convenience macros. |
| * |
| * These are used to form or modify the bit pattern of a given mutex value |
| */ |
| |
| /* Mutex state: |
| * |
| * 0 for unlocked |
| * 1 for locked, no waiters |
| * 2 for locked, maybe waiters |
| */ |
| #define MUTEX_STATE_SHIFT 0 |
| #define MUTEX_STATE_LEN 2 |
| |
| #define MUTEX_STATE_MASK FIELD_MASK(MUTEX_STATE_SHIFT, MUTEX_STATE_LEN) |
| #define MUTEX_STATE_FROM_BITS(v) FIELD_FROM_BITS(v, MUTEX_STATE_SHIFT, MUTEX_STATE_LEN) |
| #define MUTEX_STATE_TO_BITS(v) FIELD_TO_BITS(v, MUTEX_STATE_SHIFT, MUTEX_STATE_LEN) |
| |
| #define MUTEX_STATE_UNLOCKED 0 /* must be 0 to match PTHREAD_MUTEX_INITIALIZER */ |
| #define MUTEX_STATE_LOCKED_UNCONTENDED 1 /* must be 1 due to atomic dec in unlock operation */ |
| #define MUTEX_STATE_LOCKED_CONTENDED 2 /* must be 1 + LOCKED_UNCONTENDED due to atomic dec */ |
| |
| #define MUTEX_STATE_BITS_UNLOCKED MUTEX_STATE_TO_BITS(MUTEX_STATE_UNLOCKED) |
| #define MUTEX_STATE_BITS_LOCKED_UNCONTENDED MUTEX_STATE_TO_BITS(MUTEX_STATE_LOCKED_UNCONTENDED) |
| #define MUTEX_STATE_BITS_LOCKED_CONTENDED MUTEX_STATE_TO_BITS(MUTEX_STATE_LOCKED_CONTENDED) |
| |
| // Return true iff the mutex is unlocked. |
| #define MUTEX_STATE_BITS_IS_UNLOCKED(v) (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_UNLOCKED) |
| |
| // Return true iff the mutex is locked with no waiters. |
| #define MUTEX_STATE_BITS_IS_LOCKED_UNCONTENDED(v) (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_LOCKED_UNCONTENDED) |
| |
| // return true iff the mutex is locked with maybe waiters. |
| #define MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(v) (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_LOCKED_CONTENDED) |
| |
| /* used to flip from LOCKED_UNCONTENDED to LOCKED_CONTENDED */ |
| #define MUTEX_STATE_BITS_FLIP_CONTENTION(v) ((v) ^ (MUTEX_STATE_BITS_LOCKED_CONTENDED ^ MUTEX_STATE_BITS_LOCKED_UNCONTENDED)) |
| |
| /* Mutex counter: |
| * |
| * We need to check for overflow before incrementing, and we also need to |
| * detect when the counter is 0 |
| */ |
| #define MUTEX_COUNTER_SHIFT 2 |
| #define MUTEX_COUNTER_LEN 11 |
| #define MUTEX_COUNTER_MASK FIELD_MASK(MUTEX_COUNTER_SHIFT, MUTEX_COUNTER_LEN) |
| |
| #define MUTEX_COUNTER_BITS_WILL_OVERFLOW(v) (((v) & MUTEX_COUNTER_MASK) == MUTEX_COUNTER_MASK) |
| #define MUTEX_COUNTER_BITS_IS_ZERO(v) (((v) & MUTEX_COUNTER_MASK) == 0) |
| |
| /* Used to increment the counter directly after overflow has been checked */ |
| #define MUTEX_COUNTER_BITS_ONE FIELD_TO_BITS(1, MUTEX_COUNTER_SHIFT,MUTEX_COUNTER_LEN) |
| |
| /* Mutex shared bit flag |
| * |
| * This flag is set to indicate that the mutex is shared among processes. |
| * This changes the futex opcode we use for futex wait/wake operations |
| * (non-shared operations are much faster). |
| */ |
| #define MUTEX_SHARED_SHIFT 13 |
| #define MUTEX_SHARED_MASK FIELD_MASK(MUTEX_SHARED_SHIFT,1) |
| |
| /* Mutex type: |
| * We support normal, recursive and errorcheck mutexes. |
| */ |
| #define MUTEX_TYPE_SHIFT 14 |
| #define MUTEX_TYPE_LEN 2 |
| #define MUTEX_TYPE_MASK FIELD_MASK(MUTEX_TYPE_SHIFT,MUTEX_TYPE_LEN) |
| |
| #define MUTEX_TYPE_TO_BITS(t) FIELD_TO_BITS(t, MUTEX_TYPE_SHIFT, MUTEX_TYPE_LEN) |
| |
| #define MUTEX_TYPE_BITS_NORMAL MUTEX_TYPE_TO_BITS(PTHREAD_MUTEX_NORMAL) |
| #define MUTEX_TYPE_BITS_RECURSIVE MUTEX_TYPE_TO_BITS(PTHREAD_MUTEX_RECURSIVE) |
| #define MUTEX_TYPE_BITS_ERRORCHECK MUTEX_TYPE_TO_BITS(PTHREAD_MUTEX_ERRORCHECK) |
| // Use a special mutex type to mark priority inheritance mutexes. |
| #define PI_MUTEX_STATE MUTEX_TYPE_TO_BITS(3) |
| |
| // For a PI mutex, it includes below fields: |
| // Atomic(uint16_t) state; |
| // PIMutex pi_mutex; // uint16_t pi_mutex_id in 32-bit programs |
| // |
| // state holds the following fields: |
| // |
| // bits: name description |
| // 15-14 type mutex type, should be 3 |
| // 13-0 padding should be 0 |
| // |
| // pi_mutex holds the state of a PI mutex. |
| // pi_mutex_id holds an integer to find the state of a PI mutex. |
| // |
| // For a Non-PI mutex, it includes below fields: |
| // Atomic(uint16_t) state; |
| // atomic_int owner_tid; // Atomic(uint16_t) in 32-bit programs |
| // |
| // state holds the following fields: |
| // |
| // bits: name description |
| // 15-14 type mutex type, can be 0 (normal), 1 (recursive), 2 (errorcheck) |
| // 13 shared process-shared flag |
| // 12-2 counter <number of times a thread holding a recursive Non-PI mutex> - 1 |
| // 1-0 state lock state (0, 1 or 2) |
| // |
| // bits 15-13 are constant during the lifetime of the mutex. |
| // |
| // owner_tid is used only in recursive and errorcheck Non-PI mutexes to hold the mutex owner |
| // thread id. |
| // |
| // PI mutexes and Non-PI mutexes are distinguished by checking type field in state. |
| #if defined(__LP64__) |
| struct pthread_mutex_internal_t { |
| _Atomic(uint16_t) state; |
| uint16_t __pad; |
| union { |
| atomic_int owner_tid; |
| PIMutex pi_mutex; |
| }; |
| char __reserved[28]; |
| |
| PIMutex& ToPIMutex() { |
| return pi_mutex; |
| } |
| |
| void FreePIMutex() { |
| } |
| } __attribute__((aligned(4))); |
| |
| #else |
| struct pthread_mutex_internal_t { |
| _Atomic(uint16_t) state; |
| union { |
| _Atomic(uint16_t) owner_tid; |
| uint16_t pi_mutex_id; |
| }; |
| |
| PIMutex& ToPIMutex() { |
| return PIMutexAllocator::IdToPIMutex(pi_mutex_id); |
| } |
| |
| void FreePIMutex() { |
| PIMutexAllocator::FreeId(pi_mutex_id); |
| } |
| } __attribute__((aligned(4))); |
| #endif |
| |
| static_assert(sizeof(pthread_mutex_t) == sizeof(pthread_mutex_internal_t), |
| "pthread_mutex_t should actually be pthread_mutex_internal_t in implementation."); |
| |
| // For binary compatibility with old version of pthread_mutex_t, we can't use more strict alignment |
| // than 4-byte alignment. |
| static_assert(alignof(pthread_mutex_t) == 4, |
| "pthread_mutex_t should fulfill the alignment of pthread_mutex_internal_t."); |
| |
| static inline pthread_mutex_internal_t* __get_internal_mutex(pthread_mutex_t* mutex_interface) { |
| return reinterpret_cast<pthread_mutex_internal_t*>(mutex_interface); |
| } |
| |
| int pthread_mutex_init(pthread_mutex_t* mutex_interface, const pthread_mutexattr_t* attr) { |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| |
| memset(mutex, 0, sizeof(pthread_mutex_internal_t)); |
| |
| if (__predict_true(attr == nullptr)) { |
| atomic_init(&mutex->state, MUTEX_TYPE_BITS_NORMAL); |
| return 0; |
| } |
| |
| uint16_t state = 0; |
| if ((*attr & MUTEXATTR_SHARED_MASK) != 0) { |
| state |= MUTEX_SHARED_MASK; |
| } |
| |
| switch (*attr & MUTEXATTR_TYPE_MASK) { |
| case PTHREAD_MUTEX_NORMAL: |
| state |= MUTEX_TYPE_BITS_NORMAL; |
| break; |
| case PTHREAD_MUTEX_RECURSIVE: |
| state |= MUTEX_TYPE_BITS_RECURSIVE; |
| break; |
| case PTHREAD_MUTEX_ERRORCHECK: |
| state |= MUTEX_TYPE_BITS_ERRORCHECK; |
| break; |
| default: |
| return EINVAL; |
| } |
| |
| if (((*attr & MUTEXATTR_PROTOCOL_MASK) >> MUTEXATTR_PROTOCOL_SHIFT) == PTHREAD_PRIO_INHERIT) { |
| #if !defined(__LP64__) |
| if (state & MUTEX_SHARED_MASK) { |
| return EINVAL; |
| } |
| int id = PIMutexAllocator::AllocId(); |
| if (id == -1) { |
| return ENOMEM; |
| } |
| mutex->pi_mutex_id = id; |
| #endif |
| atomic_init(&mutex->state, PI_MUTEX_STATE); |
| PIMutex& pi_mutex = mutex->ToPIMutex(); |
| pi_mutex.type = *attr & MUTEXATTR_TYPE_MASK; |
| pi_mutex.shared = (*attr & MUTEXATTR_SHARED_MASK) != 0; |
| } else { |
| atomic_init(&mutex->state, state); |
| atomic_init(&mutex->owner_tid, 0); |
| } |
| return 0; |
| } |
| |
| // namespace for Non-PI mutex routines. |
| namespace NonPI { |
| |
| static inline __always_inline int NormalMutexTryLock(pthread_mutex_internal_t* mutex, |
| uint16_t shared) { |
| const uint16_t unlocked = shared | MUTEX_STATE_BITS_UNLOCKED; |
| const uint16_t locked_uncontended = shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED; |
| |
| uint16_t old_state = unlocked; |
| if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex->state, &old_state, |
| locked_uncontended, memory_order_acquire, memory_order_relaxed))) { |
| return 0; |
| } |
| return EBUSY; |
| } |
| |
| /* |
| * Lock a normal Non-PI mutex. |
| * |
| * As noted above, there are three states: |
| * 0 (unlocked, no contention) |
| * 1 (locked, no contention) |
| * 2 (locked, contention) |
| * |
| * Non-recursive mutexes don't use the thread-id or counter fields, and the |
| * "type" value is zero, so the only bits that will be set are the ones in |
| * the lock state field. |
| */ |
| static inline __always_inline int NormalMutexLock(pthread_mutex_internal_t* mutex, |
| uint16_t shared, |
| bool use_realtime_clock, |
| const timespec* abs_timeout_or_null) { |
| if (__predict_true(NormalMutexTryLock(mutex, shared) == 0)) { |
| return 0; |
| } |
| int result = check_timespec(abs_timeout_or_null, true); |
| if (result != 0) { |
| return result; |
| } |
| |
| ScopedTrace trace("Contending for pthread mutex"); |
| |
| const uint16_t unlocked = shared | MUTEX_STATE_BITS_UNLOCKED; |
| const uint16_t locked_contended = shared | MUTEX_STATE_BITS_LOCKED_CONTENDED; |
| |
| // We want to go to sleep until the mutex is available, which requires |
| // promoting it to locked_contended. We need to swap in the new state |
| // and then wait until somebody wakes us up. |
| // An atomic_exchange is used to compete with other threads for the lock. |
| // If it returns unlocked, we have acquired the lock, otherwise another |
| // thread still holds the lock and we should wait again. |
| // If lock is acquired, an acquire fence is needed to make all memory accesses |
| // made by other threads visible to the current CPU. |
| while (atomic_exchange_explicit(&mutex->state, locked_contended, |
| memory_order_acquire) != unlocked) { |
| if (__futex_wait_ex(&mutex->state, shared, locked_contended, use_realtime_clock, |
| abs_timeout_or_null) == -ETIMEDOUT) { |
| return ETIMEDOUT; |
| } |
| } |
| return 0; |
| } |
| |
| /* |
| * Release a normal Non-PI mutex. The caller is responsible for determining |
| * that we are in fact the owner of this lock. |
| */ |
| static inline __always_inline void NormalMutexUnlock(pthread_mutex_internal_t* mutex, |
| uint16_t shared) { |
| const uint16_t unlocked = shared | MUTEX_STATE_BITS_UNLOCKED; |
| const uint16_t locked_contended = shared | MUTEX_STATE_BITS_LOCKED_CONTENDED; |
| |
| // We use an atomic_exchange to release the lock. If locked_contended state |
| // is returned, some threads is waiting for the lock and we need to wake up |
| // one of them. |
| // A release fence is required to make previous stores visible to next |
| // lock owner threads. |
| if (atomic_exchange_explicit(&mutex->state, unlocked, |
| memory_order_release) == locked_contended) { |
| // Wake up one waiting thread. We don't know which thread will be |
| // woken or when it'll start executing -- futexes make no guarantees |
| // here. There may not even be a thread waiting. |
| // |
| // The newly-woken thread will replace the unlocked state we just set above |
| // with locked_contended state, which means that when it eventually releases |
| // the mutex it will also call FUTEX_WAKE. This results in one extra wake |
| // call whenever a lock is contended, but let us avoid forgetting anyone |
| // without requiring us to track the number of sleepers. |
| // |
| // It's possible for another thread to sneak in and grab the lock between |
| // the exchange above and the wake call below. If the new thread is "slow" |
| // and holds the lock for a while, we'll wake up a sleeper, which will swap |
| // in locked_uncontended state and then go back to sleep since the lock is |
| // still held. If the new thread is "fast", running to completion before |
| // we call wake, the thread we eventually wake will find an unlocked mutex |
| // and will execute. Either way we have correct behavior and nobody is |
| // orphaned on the wait queue. |
| // |
| // The pthread_mutex_internal_t object may have been deallocated between the |
| // atomic exchange and the wake call. In that case, this wake call could |
| // target unmapped memory or memory used by an otherwise unrelated futex |
| // operation. Even if the kernel avoids spurious futex wakeups from its |
| // point of view, this wake call could trigger a spurious wakeup in any |
| // futex accessible from this process. References: |
| // - https://lkml.org/lkml/2014/11/27/472 |
| // - http://austingroupbugs.net/view.php?id=811#c2267 |
| __futex_wake_ex(&mutex->state, shared, 1); |
| } |
| } |
| |
| /* This common inlined function is used to increment the counter of a recursive Non-PI mutex. |
| * |
| * If the counter overflows, it will return EAGAIN. |
| * Otherwise, it atomically increments the counter and returns 0. |
| * |
| */ |
| static inline __always_inline int RecursiveIncrement(pthread_mutex_internal_t* mutex, |
| uint16_t old_state) { |
| // Detect recursive lock overflow and return EAGAIN. |
| // This is safe because only the owner thread can modify the |
| // counter bits in the mutex value. |
| if (MUTEX_COUNTER_BITS_WILL_OVERFLOW(old_state)) { |
| return EAGAIN; |
| } |
| |
| // Other threads are able to change the lower bits (e.g. promoting it to "contended"), |
| // but the mutex counter will not overflow. So we use atomic_fetch_add operation here. |
| // The mutex is already locked by current thread, so we don't need an acquire fence. |
| atomic_fetch_add_explicit(&mutex->state, MUTEX_COUNTER_BITS_ONE, memory_order_relaxed); |
| return 0; |
| } |
| |
| // Wait on a recursive or errorcheck Non-PI mutex. |
| static inline __always_inline int RecursiveOrErrorcheckMutexWait(pthread_mutex_internal_t* mutex, |
| uint16_t shared, |
| uint16_t old_state, |
| bool use_realtime_clock, |
| const timespec* abs_timeout) { |
| // __futex_wait always waits on a 32-bit value. But state is 16-bit. For a normal mutex, the owner_tid |
| // field in mutex is not used. On 64-bit devices, the __pad field in mutex is not used. |
| // But when a recursive or errorcheck mutex is used on 32-bit devices, we need to add the |
| // owner_tid value in the value argument for __futex_wait, otherwise we may always get EAGAIN error. |
| |
| #if defined(__LP64__) |
| return __futex_wait_ex(&mutex->state, shared, old_state, use_realtime_clock, abs_timeout); |
| |
| #else |
| // This implementation works only when the layout of pthread_mutex_internal_t matches below expectation. |
| // And it is based on the assumption that Android is always in little-endian devices. |
| static_assert(offsetof(pthread_mutex_internal_t, state) == 0, ""); |
| static_assert(offsetof(pthread_mutex_internal_t, owner_tid) == 2, ""); |
| |
| uint32_t owner_tid = atomic_load_explicit(&mutex->owner_tid, memory_order_relaxed); |
| return __futex_wait_ex(&mutex->state, shared, (owner_tid << 16) | old_state, |
| use_realtime_clock, abs_timeout); |
| #endif |
| } |
| |
| // Lock a Non-PI mutex. |
| static int MutexLockWithTimeout(pthread_mutex_internal_t* mutex, bool use_realtime_clock, |
| const timespec* abs_timeout_or_null) { |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| uint16_t mtype = (old_state & MUTEX_TYPE_MASK); |
| uint16_t shared = (old_state & MUTEX_SHARED_MASK); |
| |
| // Handle common case first. |
| if ( __predict_true(mtype == MUTEX_TYPE_BITS_NORMAL) ) { |
| return NormalMutexLock(mutex, shared, use_realtime_clock, abs_timeout_or_null); |
| } |
| |
| // Do we already own this recursive or error-check mutex? |
| pid_t tid = __get_thread()->tid; |
| if (tid == atomic_load_explicit(&mutex->owner_tid, memory_order_relaxed)) { |
| if (mtype == MUTEX_TYPE_BITS_ERRORCHECK) { |
| return EDEADLK; |
| } |
| return RecursiveIncrement(mutex, old_state); |
| } |
| |
| const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED; |
| const uint16_t locked_uncontended = mtype | shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED; |
| const uint16_t locked_contended = mtype | shared | MUTEX_STATE_BITS_LOCKED_CONTENDED; |
| |
| // First, if the mutex is unlocked, try to quickly acquire it. |
| // In the optimistic case where this works, set the state to locked_uncontended. |
| if (old_state == unlocked) { |
| // If exchanged successfully, an acquire fence is required to make |
| // all memory accesses made by other threads visible to the current CPU. |
| if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex->state, &old_state, |
| locked_uncontended, memory_order_acquire, memory_order_relaxed))) { |
| atomic_store_explicit(&mutex->owner_tid, tid, memory_order_relaxed); |
| return 0; |
| } |
| } |
| |
| ScopedTrace trace("Contending for pthread mutex"); |
| |
| while (true) { |
| if (old_state == unlocked) { |
| // NOTE: We put the state to locked_contended since we _know_ there |
| // is contention when we are in this loop. This ensures all waiters |
| // will be unlocked. |
| |
| // If exchanged successfully, an acquire fence is required to make |
| // all memory accesses made by other threads visible to the current CPU. |
| if (__predict_true(atomic_compare_exchange_weak_explicit(&mutex->state, |
| &old_state, locked_contended, |
| memory_order_acquire, |
| memory_order_relaxed))) { |
| atomic_store_explicit(&mutex->owner_tid, tid, memory_order_relaxed); |
| return 0; |
| } |
| continue; |
| } else if (MUTEX_STATE_BITS_IS_LOCKED_UNCONTENDED(old_state)) { |
| // We should set it to locked_contended beforing going to sleep. This can make |
| // sure waiters will be woken up eventually. |
| |
| int new_state = MUTEX_STATE_BITS_FLIP_CONTENTION(old_state); |
| if (__predict_false(!atomic_compare_exchange_weak_explicit(&mutex->state, |
| &old_state, new_state, |
| memory_order_relaxed, |
| memory_order_relaxed))) { |
| continue; |
| } |
| old_state = new_state; |
| } |
| |
| int result = check_timespec(abs_timeout_or_null, true); |
| if (result != 0) { |
| return result; |
| } |
| // We are in locked_contended state, sleep until someone wakes us up. |
| if (RecursiveOrErrorcheckMutexWait(mutex, shared, old_state, use_realtime_clock, |
| abs_timeout_or_null) == -ETIMEDOUT) { |
| return ETIMEDOUT; |
| } |
| old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| } |
| } |
| |
| } // namespace NonPI |
| |
| static inline __always_inline bool IsMutexDestroyed(uint16_t mutex_state) { |
| return mutex_state == 0xffff; |
| } |
| |
| // Inlining this function in pthread_mutex_lock() adds the cost of stack frame instructions on |
| // ARM64. So make it noinline. |
| static int __attribute__((noinline)) HandleUsingDestroyedMutex(pthread_mutex_t* mutex, |
| const char* function_name) { |
| if (android_get_application_target_sdk_version() >= __ANDROID_API_P__) { |
| __fortify_fatal("%s called on a destroyed mutex (%p)", function_name, mutex); |
| } |
| return EBUSY; |
| } |
| |
| int pthread_mutex_lock(pthread_mutex_t* mutex_interface) { |
| #if !defined(__LP64__) |
| // Some apps depend on being able to pass NULL as a mutex and get EINVAL |
| // back. Don't need to worry about it for LP64 since the ABI is brand new, |
| // but keep compatibility for LP32. http://b/19995172. |
| if (mutex_interface == nullptr) { |
| return EINVAL; |
| } |
| #endif |
| |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| uint16_t mtype = (old_state & MUTEX_TYPE_MASK); |
| // Avoid slowing down fast path of normal mutex lock operation. |
| if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) { |
| uint16_t shared = (old_state & MUTEX_SHARED_MASK); |
| if (__predict_true(NonPI::NormalMutexTryLock(mutex, shared) == 0)) { |
| return 0; |
| } |
| } |
| if (old_state == PI_MUTEX_STATE) { |
| PIMutex& m = mutex->ToPIMutex(); |
| // Handle common case first. |
| if (__predict_true(PIMutexTryLock(m) == 0)) { |
| return 0; |
| } |
| return PIMutexTimedLock(mutex->ToPIMutex(), false, nullptr); |
| } |
| if (__predict_false(IsMutexDestroyed(old_state))) { |
| return HandleUsingDestroyedMutex(mutex_interface, __FUNCTION__); |
| } |
| return NonPI::MutexLockWithTimeout(mutex, false, nullptr); |
| } |
| |
| int pthread_mutex_unlock(pthread_mutex_t* mutex_interface) { |
| #if !defined(__LP64__) |
| // Some apps depend on being able to pass NULL as a mutex and get EINVAL |
| // back. Don't need to worry about it for LP64 since the ABI is brand new, |
| // but keep compatibility for LP32. http://b/19995172. |
| if (mutex_interface == nullptr) { |
| return EINVAL; |
| } |
| #endif |
| |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| uint16_t mtype = (old_state & MUTEX_TYPE_MASK); |
| uint16_t shared = (old_state & MUTEX_SHARED_MASK); |
| |
| // Handle common case first. |
| if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) { |
| NonPI::NormalMutexUnlock(mutex, shared); |
| return 0; |
| } |
| if (old_state == PI_MUTEX_STATE) { |
| return PIMutexUnlock(mutex->ToPIMutex()); |
| } |
| if (__predict_false(IsMutexDestroyed(old_state))) { |
| return HandleUsingDestroyedMutex(mutex_interface, __FUNCTION__); |
| } |
| |
| // Do we already own this recursive or error-check mutex? |
| pid_t tid = __get_thread()->tid; |
| if ( tid != atomic_load_explicit(&mutex->owner_tid, memory_order_relaxed) ) { |
| return EPERM; |
| } |
| |
| // If the counter is > 0, we can simply decrement it atomically. |
| // Since other threads can mutate the lower state bits (and only the |
| // lower state bits), use a compare_exchange loop to do it. |
| if (!MUTEX_COUNTER_BITS_IS_ZERO(old_state)) { |
| // We still own the mutex, so a release fence is not needed. |
| atomic_fetch_sub_explicit(&mutex->state, MUTEX_COUNTER_BITS_ONE, memory_order_relaxed); |
| return 0; |
| } |
| |
| // The counter is 0, so we'are going to unlock the mutex by resetting its |
| // state to unlocked, we need to perform a atomic_exchange inorder to read |
| // the current state, which will be locked_contended if there may have waiters |
| // to awake. |
| // A release fence is required to make previous stores visible to next |
| // lock owner threads. |
| atomic_store_explicit(&mutex->owner_tid, 0, memory_order_relaxed); |
| const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED; |
| old_state = atomic_exchange_explicit(&mutex->state, unlocked, memory_order_release); |
| if (MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(old_state)) { |
| __futex_wake_ex(&mutex->state, shared, 1); |
| } |
| |
| return 0; |
| } |
| |
| int pthread_mutex_trylock(pthread_mutex_t* mutex_interface) { |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| uint16_t mtype = (old_state & MUTEX_TYPE_MASK); |
| |
| // Handle common case first. |
| if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) { |
| uint16_t shared = (old_state & MUTEX_SHARED_MASK); |
| return NonPI::NormalMutexTryLock(mutex, shared); |
| } |
| if (old_state == PI_MUTEX_STATE) { |
| return PIMutexTryLock(mutex->ToPIMutex()); |
| } |
| if (__predict_false(IsMutexDestroyed(old_state))) { |
| return HandleUsingDestroyedMutex(mutex_interface, __FUNCTION__); |
| } |
| |
| // Do we already own this recursive or error-check mutex? |
| pid_t tid = __get_thread()->tid; |
| if (tid == atomic_load_explicit(&mutex->owner_tid, memory_order_relaxed)) { |
| if (mtype == MUTEX_TYPE_BITS_ERRORCHECK) { |
| return EBUSY; |
| } |
| return NonPI::RecursiveIncrement(mutex, old_state); |
| } |
| |
| uint16_t shared = (old_state & MUTEX_SHARED_MASK); |
| const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED; |
| const uint16_t locked_uncontended = mtype | shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED; |
| |
| // Same as pthread_mutex_lock, except that we don't want to wait, and |
| // the only operation that can succeed is a single compare_exchange to acquire the |
| // lock if it is released / not owned by anyone. No need for a complex loop. |
| // If exchanged successfully, an acquire fence is required to make |
| // all memory accesses made by other threads visible to the current CPU. |
| old_state = unlocked; |
| if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex->state, &old_state, |
| locked_uncontended, |
| memory_order_acquire, |
| memory_order_relaxed))) { |
| atomic_store_explicit(&mutex->owner_tid, tid, memory_order_relaxed); |
| return 0; |
| } |
| return EBUSY; |
| } |
| |
| #if !defined(__LP64__) |
| extern "C" int pthread_mutex_lock_timeout_np(pthread_mutex_t* mutex_interface, unsigned ms) { |
| timespec ts; |
| timespec_from_ms(ts, ms); |
| timespec abs_timeout; |
| absolute_timespec_from_timespec(abs_timeout, ts, CLOCK_MONOTONIC); |
| int error = NonPI::MutexLockWithTimeout(__get_internal_mutex(mutex_interface), false, |
| &abs_timeout); |
| if (error == ETIMEDOUT) { |
| error = EBUSY; |
| } |
| return error; |
| } |
| #endif |
| |
| static int __pthread_mutex_timedlock(pthread_mutex_t* mutex_interface, bool use_realtime_clock, |
| const timespec* abs_timeout, const char* function) { |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| uint16_t mtype = (old_state & MUTEX_TYPE_MASK); |
| // Handle common case first. |
| if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) { |
| uint16_t shared = (old_state & MUTEX_SHARED_MASK); |
| if (__predict_true(NonPI::NormalMutexTryLock(mutex, shared) == 0)) { |
| return 0; |
| } |
| } |
| if (old_state == PI_MUTEX_STATE) { |
| return PIMutexTimedLock(mutex->ToPIMutex(), use_realtime_clock, abs_timeout); |
| } |
| if (__predict_false(IsMutexDestroyed(old_state))) { |
| return HandleUsingDestroyedMutex(mutex_interface, function); |
| } |
| return NonPI::MutexLockWithTimeout(mutex, use_realtime_clock, abs_timeout); |
| } |
| |
| int pthread_mutex_timedlock(pthread_mutex_t* mutex_interface, const struct timespec* abs_timeout) { |
| return __pthread_mutex_timedlock(mutex_interface, true, abs_timeout, __FUNCTION__); |
| } |
| |
| int pthread_mutex_timedlock_monotonic_np(pthread_mutex_t* mutex_interface, |
| const struct timespec* abs_timeout) { |
| return __pthread_mutex_timedlock(mutex_interface, false, abs_timeout, __FUNCTION__); |
| } |
| |
| int pthread_mutex_clocklock(pthread_mutex_t* mutex_interface, clockid_t clock, |
| const struct timespec* abs_timeout) { |
| switch (clock) { |
| case CLOCK_MONOTONIC: |
| return __pthread_mutex_timedlock(mutex_interface, false, abs_timeout, __FUNCTION__); |
| case CLOCK_REALTIME: |
| return __pthread_mutex_timedlock(mutex_interface, true, abs_timeout, __FUNCTION__); |
| default: { |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| if (IsMutexDestroyed(old_state)) { |
| return HandleUsingDestroyedMutex(mutex_interface, __FUNCTION__); |
| } |
| return EINVAL; |
| } |
| } |
| } |
| |
| int pthread_mutex_destroy(pthread_mutex_t* mutex_interface) { |
| pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface); |
| uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed); |
| if (__predict_false(IsMutexDestroyed(old_state))) { |
| return HandleUsingDestroyedMutex(mutex_interface, __FUNCTION__); |
| } |
| if (old_state == PI_MUTEX_STATE) { |
| int result = PIMutexDestroy(mutex->ToPIMutex()); |
| if (result == 0) { |
| mutex->FreePIMutex(); |
| atomic_store(&mutex->state, 0xffff); |
| } |
| return result; |
| } |
| // Store 0xffff to make the mutex unusable. Although POSIX standard says it is undefined |
| // behavior to destroy a locked mutex, we prefer not to change mutex->state in that situation. |
| if (MUTEX_STATE_BITS_IS_UNLOCKED(old_state) && |
| atomic_compare_exchange_strong_explicit(&mutex->state, &old_state, 0xffff, |
| memory_order_relaxed, memory_order_relaxed)) { |
| return 0; |
| } |
| return EBUSY; |
| } |