| /* |
| * Copyright 2015 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "SkSharedMutex.h" |
| |
| #include "SkAtomics.h" |
| #include "SkTypes.h" |
| #include "../private/SkSemaphore.h" |
| |
| #if defined(THREAD_SANITIZER) |
| |
| /* Report that a lock has been created at address "lock". */ |
| #define ANNOTATE_RWLOCK_CREATE(lock) \ |
| AnnotateRWLockCreate(__FILE__, __LINE__, lock) |
| |
| /* Report that the lock at address "lock" is about to be destroyed. */ |
| #define ANNOTATE_RWLOCK_DESTROY(lock) \ |
| AnnotateRWLockDestroy(__FILE__, __LINE__, lock) |
| |
| /* Report that the lock at address "lock" has been acquired. |
| is_w=1 for writer lock, is_w=0 for reader lock. */ |
| #define ANNOTATE_RWLOCK_ACQUIRED(lock, is_w) \ |
| AnnotateRWLockAcquired(__FILE__, __LINE__, lock, is_w) |
| |
| /* Report that the lock at address "lock" is about to be released. */ |
| #define ANNOTATE_RWLOCK_RELEASED(lock, is_w) \ |
| AnnotateRWLockReleased(__FILE__, __LINE__, lock, is_w) |
| |
| #ifdef DYNAMIC_ANNOTATIONS_WANT_ATTRIBUTE_WEAK |
| # ifdef __GNUC__ |
| # define DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK __attribute__((weak)) |
| # else |
| /* TODO(glider): for Windows support we may want to change this macro in order |
| to prepend __declspec(selectany) to the annotations' declarations. */ |
| # error weak annotations are not supported for your compiler |
| # endif |
| #else |
| # define DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK |
| #endif |
| |
| extern "C" { |
| void AnnotateRWLockCreate( |
| const char *file, int line, |
| const volatile void *lock) DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK; |
| void AnnotateRWLockDestroy( |
| const char *file, int line, |
| const volatile void *lock) DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK; |
| void AnnotateRWLockAcquired( |
| const char *file, int line, |
| const volatile void *lock, long is_w) DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK; |
| void AnnotateRWLockReleased( |
| const char *file, int line, |
| const volatile void *lock, long is_w) DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK; |
| } |
| |
| #else |
| |
| #define ANNOTATE_RWLOCK_CREATE(lock) |
| #define ANNOTATE_RWLOCK_DESTROY(lock) |
| #define ANNOTATE_RWLOCK_ACQUIRED(lock, is_w) |
| #define ANNOTATE_RWLOCK_RELEASED(lock, is_w) |
| |
| #endif |
| |
| #ifdef SK_DEBUG |
| |
| #include "SkTDArray.h" |
| #ifdef SK_BUILD_FOR_WIN |
| #include <windows.h> |
| static int64_t get_thread_id() { return GetCurrentThreadId(); } |
| #else |
| #include <pthread.h> |
| static int64_t get_thread_id() { return (int64_t)pthread_self(); } |
| #endif |
| |
| typedef int64_t ThreadID; |
| |
| class SkSharedMutex::ThreadIDSet { |
| public: |
| // Returns true if threadID is in the set. |
| bool find(ThreadID threadID) const { |
| for (auto& t : fThreadIDs) { |
| if (t == threadID) return true; |
| } |
| return false; |
| } |
| |
| // Returns true if did not already exist. |
| bool tryAdd(ThreadID threadID) { |
| for (auto& t : fThreadIDs) { |
| if (t == threadID) return false; |
| } |
| fThreadIDs.append(1, &threadID); |
| return true; |
| } |
| // Returns true if already exists in Set. |
| bool tryRemove(ThreadID threadID) { |
| for (int i = 0; i < fThreadIDs.count(); ++i) { |
| if (fThreadIDs[i] == threadID) { |
| fThreadIDs.remove(i); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| void swap(ThreadIDSet& other) { |
| fThreadIDs.swap(other.fThreadIDs); |
| } |
| |
| int count() const { |
| return fThreadIDs.count(); |
| } |
| |
| private: |
| SkTDArray<ThreadID> fThreadIDs; |
| }; |
| |
| SkSharedMutex::SkSharedMutex() |
| : fCurrentShared(new ThreadIDSet) |
| , fWaitingExclusive(new ThreadIDSet) |
| , fWaitingShared(new ThreadIDSet){ |
| ANNOTATE_RWLOCK_CREATE(this); |
| } |
| |
| SkSharedMutex::~SkSharedMutex() { ANNOTATE_RWLOCK_DESTROY(this); } |
| |
| void SkSharedMutex::acquire() { |
| ThreadID threadID(get_thread_id()); |
| int currentSharedCount; |
| int waitingExclusiveCount; |
| { |
| SkAutoMutexAcquire l(&fMu); |
| |
| if (!fWaitingExclusive->tryAdd(threadID)) { |
| SkDEBUGFAILF("Thread %lx already has an exclusive lock\n", threadID); |
| } |
| |
| currentSharedCount = fCurrentShared->count(); |
| waitingExclusiveCount = fWaitingExclusive->count(); |
| } |
| |
| if (currentSharedCount > 0 || waitingExclusiveCount > 1) { |
| fExclusiveQueue.wait(); |
| } |
| |
| ANNOTATE_RWLOCK_ACQUIRED(this, 1); |
| } |
| |
| // Implementation Detail: |
| // The shared threads need two seperate queues to keep the threads that were added after the |
| // exclusive lock separate from the threads added before. |
| void SkSharedMutex::release() { |
| ANNOTATE_RWLOCK_RELEASED(this, 1); |
| ThreadID threadID(get_thread_id()); |
| int sharedWaitingCount; |
| int exclusiveWaitingCount; |
| int sharedQueueSelect; |
| { |
| SkAutoMutexAcquire l(&fMu); |
| SkASSERT(0 == fCurrentShared->count()); |
| if (!fWaitingExclusive->tryRemove(threadID)) { |
| SkDEBUGFAILF("Thread %lx did not have the lock held.\n", threadID); |
| } |
| exclusiveWaitingCount = fWaitingExclusive->count(); |
| sharedWaitingCount = fWaitingShared->count(); |
| fWaitingShared.swap(fCurrentShared); |
| sharedQueueSelect = fSharedQueueSelect; |
| if (sharedWaitingCount > 0) { |
| fSharedQueueSelect = 1 - fSharedQueueSelect; |
| } |
| } |
| |
| if (sharedWaitingCount > 0) { |
| fSharedQueue[sharedQueueSelect].signal(sharedWaitingCount); |
| } else if (exclusiveWaitingCount > 0) { |
| fExclusiveQueue.signal(); |
| } |
| } |
| |
| void SkSharedMutex::assertHeld() const { |
| ThreadID threadID(get_thread_id()); |
| SkAutoMutexAcquire l(&fMu); |
| SkASSERT(0 == fCurrentShared->count()); |
| SkASSERT(fWaitingExclusive->find(threadID)); |
| } |
| |
| void SkSharedMutex::acquireShared() { |
| ThreadID threadID(get_thread_id()); |
| int exclusiveWaitingCount; |
| int sharedQueueSelect; |
| { |
| SkAutoMutexAcquire l(&fMu); |
| exclusiveWaitingCount = fWaitingExclusive->count(); |
| if (exclusiveWaitingCount > 0) { |
| if (!fWaitingShared->tryAdd(threadID)) { |
| SkDEBUGFAILF("Thread %lx was already waiting!\n", threadID); |
| } |
| } else { |
| if (!fCurrentShared->tryAdd(threadID)) { |
| SkDEBUGFAILF("Thread %lx already holds a shared lock!\n", threadID); |
| } |
| } |
| sharedQueueSelect = fSharedQueueSelect; |
| } |
| |
| if (exclusiveWaitingCount > 0) { |
| fSharedQueue[sharedQueueSelect].wait(); |
| } |
| |
| ANNOTATE_RWLOCK_ACQUIRED(this, 0); |
| } |
| |
| void SkSharedMutex::releaseShared() { |
| ANNOTATE_RWLOCK_RELEASED(this, 0); |
| ThreadID threadID(get_thread_id()); |
| |
| int currentSharedCount; |
| int waitingExclusiveCount; |
| { |
| SkAutoMutexAcquire l(&fMu); |
| if (!fCurrentShared->tryRemove(threadID)) { |
| SkDEBUGFAILF("Thread %lx does not hold a shared lock.\n", threadID); |
| } |
| currentSharedCount = fCurrentShared->count(); |
| waitingExclusiveCount = fWaitingExclusive->count(); |
| } |
| |
| if (0 == currentSharedCount && waitingExclusiveCount > 0) { |
| fExclusiveQueue.signal(); |
| } |
| } |
| |
| void SkSharedMutex::assertHeldShared() const { |
| ThreadID threadID(get_thread_id()); |
| SkAutoMutexAcquire l(&fMu); |
| SkASSERT(fCurrentShared->find(threadID)); |
| } |
| |
| #else |
| |
| // The fQueueCounts fields holds many counts in an int32_t in order to make managing them atomic. |
| // These three counts must be the same size, so each gets 10 bits. The 10 bits represent |
| // the log of the count which is 1024. |
| // |
| // The three counts held in fQueueCounts are: |
| // * Shared - the number of shared lock holders currently running. |
| // * WaitingExclusive - the number of threads waiting for an exclusive lock. |
| // * WaitingShared - the number of threads waiting to run while waiting for an exclusive thread |
| // to finish. |
| static const int kLogThreadCount = 10; |
| |
| enum { |
| kSharedOffset = (0 * kLogThreadCount), |
| kWaitingExlusiveOffset = (1 * kLogThreadCount), |
| kWaitingSharedOffset = (2 * kLogThreadCount), |
| kSharedMask = ((1 << kLogThreadCount) - 1) << kSharedOffset, |
| kWaitingExclusiveMask = ((1 << kLogThreadCount) - 1) << kWaitingExlusiveOffset, |
| kWaitingSharedMask = ((1 << kLogThreadCount) - 1) << kWaitingSharedOffset, |
| }; |
| |
| SkSharedMutex::SkSharedMutex() : fQueueCounts(0) { ANNOTATE_RWLOCK_CREATE(this); } |
| SkSharedMutex::~SkSharedMutex() { ANNOTATE_RWLOCK_DESTROY(this); } |
| void SkSharedMutex::acquire() { |
| // Increment the count of exclusive queue waiters. |
| int32_t oldQueueCounts = fQueueCounts.fetch_add(1 << kWaitingExlusiveOffset, |
| sk_memory_order_acquire); |
| |
| // If there are no other exclusive waiters and no shared threads are running then run |
| // else wait. |
| if ((oldQueueCounts & kWaitingExclusiveMask) > 0 || (oldQueueCounts & kSharedMask) > 0) { |
| fExclusiveQueue.wait(); |
| } |
| ANNOTATE_RWLOCK_ACQUIRED(this, 1); |
| } |
| |
| void SkSharedMutex::release() { |
| ANNOTATE_RWLOCK_RELEASED(this, 1); |
| |
| int32_t oldQueueCounts = fQueueCounts.load(sk_memory_order_relaxed); |
| int32_t waitingShared; |
| int32_t newQueueCounts; |
| do { |
| newQueueCounts = oldQueueCounts; |
| |
| // Decrement exclusive waiters. |
| newQueueCounts -= 1 << kWaitingExlusiveOffset; |
| |
| // The number of threads waiting to acquire a shared lock. |
| waitingShared = (oldQueueCounts & kWaitingSharedMask) >> kWaitingSharedOffset; |
| |
| // If there are any move the counts of all the shared waiters to actual shared. They are |
| // going to run next. |
| if (waitingShared > 0) { |
| |
| // Set waiting shared to zero. |
| newQueueCounts &= ~kWaitingSharedMask; |
| |
| // Because this is the exclusive release, then there are zero readers. So, the bits |
| // for shared locks should be zero. Since those bits are zero, we can just |= in the |
| // waitingShared count instead of clearing with an &= and then |= the count. |
| newQueueCounts |= waitingShared << kSharedOffset; |
| } |
| |
| } while (!fQueueCounts.compare_exchange(&oldQueueCounts, newQueueCounts, |
| sk_memory_order_release, sk_memory_order_relaxed)); |
| |
| if (waitingShared > 0) { |
| // Run all the shared. |
| fSharedQueue.signal(waitingShared); |
| } else if ((newQueueCounts & kWaitingExclusiveMask) > 0) { |
| // Run a single exclusive waiter. |
| fExclusiveQueue.signal(); |
| } |
| } |
| |
| void SkSharedMutex::acquireShared() { |
| int32_t oldQueueCounts = fQueueCounts.load(sk_memory_order_relaxed); |
| int32_t newQueueCounts; |
| do { |
| newQueueCounts = oldQueueCounts; |
| // If there are waiting exclusives then this shared lock waits else it runs. |
| if ((newQueueCounts & kWaitingExclusiveMask) > 0) { |
| newQueueCounts += 1 << kWaitingSharedOffset; |
| } else { |
| newQueueCounts += 1 << kSharedOffset; |
| } |
| } while (!fQueueCounts.compare_exchange(&oldQueueCounts, newQueueCounts, |
| sk_memory_order_acquire, sk_memory_order_relaxed)); |
| |
| // If there are waiting exclusives, then this shared waits until after it runs. |
| if ((newQueueCounts & kWaitingExclusiveMask) > 0) { |
| fSharedQueue.wait(); |
| } |
| ANNOTATE_RWLOCK_ACQUIRED(this, 0); |
| |
| } |
| |
| void SkSharedMutex::releaseShared() { |
| ANNOTATE_RWLOCK_RELEASED(this, 0); |
| |
| // Decrement the shared count. |
| int32_t oldQueueCounts = fQueueCounts.fetch_sub(1 << kSharedOffset, |
| sk_memory_order_release); |
| |
| // If shared count is going to zero (because the old count == 1) and there are exclusive |
| // waiters, then run a single exclusive waiter. |
| if (((oldQueueCounts & kSharedMask) >> kSharedOffset) == 1 |
| && (oldQueueCounts & kWaitingExclusiveMask) > 0) { |
| fExclusiveQueue.signal(); |
| } |
| } |
| |
| #endif |