| /* |
| * Copyright (C) 2005 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #define LOG_TAG "RefBase" |
| // #define LOG_NDEBUG 0 |
| |
| #include <memory> |
| |
| #include <android-base/macros.h> |
| |
| #include <log/log.h> |
| |
| #include <utils/RefBase.h> |
| |
| #include <utils/Mutex.h> |
| |
| #ifndef __unused |
| #define __unused __attribute__((__unused__)) |
| #endif |
| |
| // Compile with refcounting debugging enabled. |
| #define DEBUG_REFS 0 |
| |
| // The following three are ignored unless DEBUG_REFS is set. |
| |
| // whether ref-tracking is enabled by default, if not, trackMe(true, false) |
| // needs to be called explicitly |
| #define DEBUG_REFS_ENABLED_BY_DEFAULT 0 |
| |
| // whether callstack are collected (significantly slows things down) |
| #define DEBUG_REFS_CALLSTACK_ENABLED 1 |
| |
| // folder where stack traces are saved when DEBUG_REFS is enabled |
| // this folder needs to exist and be writable |
| #define DEBUG_REFS_CALLSTACK_PATH "/data/debug" |
| |
| // log all reference counting operations |
| #define PRINT_REFS 0 |
| |
| // Continue after logging a stack trace if ~RefBase discovers that reference |
| // count has never been incremented. Normally we conspicuously crash in that |
| // case. |
| #define DEBUG_REFBASE_DESTRUCTION 1 |
| |
| #if !defined(_WIN32) && !defined(__APPLE__) |
| // CallStack is only supported on linux type platforms. |
| #define CALLSTACK_ENABLED 1 |
| #else |
| #define CALLSTACK_ENABLED 0 |
| #endif |
| |
| #if CALLSTACK_ENABLED |
| #include <utils/CallStack.h> |
| #endif |
| |
| // --------------------------------------------------------------------------- |
| |
| namespace android { |
| |
| // Observations, invariants, etc: |
| |
| // By default, obects are destroyed when the last strong reference disappears |
| // or, if the object never had a strong reference, when the last weak reference |
| // disappears. |
| // |
| // OBJECT_LIFETIME_WEAK changes this behavior to retain the object |
| // unconditionally until the last reference of either kind disappears. The |
| // client ensures that the extendObjectLifetime call happens before the dec |
| // call that would otherwise have deallocated the object, or before an |
| // attemptIncStrong call that might rely on it. We do not worry about |
| // concurrent changes to the object lifetime. |
| // |
| // AttemptIncStrong will succeed if the object has a strong reference, or if it |
| // has a weak reference and has never had a strong reference. |
| // AttemptIncWeak really does succeed only if there is already a WEAK |
| // reference, and thus may fail when attemptIncStrong would succeed. |
| // |
| // mStrong is the strong reference count. mWeak is the weak reference count. |
| // Between calls, and ignoring memory ordering effects, mWeak includes strong |
| // references, and is thus >= mStrong. |
| // |
| // A weakref_impl holds all the information, including both reference counts, |
| // required to perform wp<> operations. Thus these can continue to be performed |
| // after the RefBase object has been destroyed. |
| // |
| // A weakref_impl is allocated as the value of mRefs in a RefBase object on |
| // construction. |
| // In the OBJECT_LIFETIME_STRONG case, it is normally deallocated in decWeak, |
| // and hence lives as long as the last weak reference. (It can also be |
| // deallocated in the RefBase destructor iff the strong reference count was |
| // never incremented and the weak count is zero, e.g. if the RefBase object is |
| // explicitly destroyed without decrementing the strong count. This should be |
| // avoided.) In this case, the RefBase destructor should be invoked from |
| // decStrong. |
| // In the OBJECT_LIFETIME_WEAK case, the weakref_impl is always deallocated in |
| // the RefBase destructor, which is always invoked by decWeak. DecStrong |
| // explicitly avoids the deletion in this case. |
| // |
| // Memory ordering: |
| // The client must ensure that every inc() call, together with all other |
| // accesses to the object, happens before the corresponding dec() call. |
| // |
| // We try to keep memory ordering constraints on atomics as weak as possible, |
| // since memory fences or ordered memory accesses are likely to be a major |
| // performance cost for this code. All accesses to mStrong, mWeak, and mFlags |
| // explicitly relax memory ordering in some way. |
| // |
| // The only operations that are not memory_order_relaxed are reference count |
| // decrements. All reference count decrements are release operations. In |
| // addition, the final decrement leading the deallocation is followed by an |
| // acquire fence, which we can view informally as also turning it into an |
| // acquire operation. (See 29.8p4 [atomics.fences] for details. We could |
| // alternatively use acq_rel operations for all decrements. This is probably |
| // slower on most current (2016) hardware, especially on ARMv7, but that may |
| // not be true indefinitely.) |
| // |
| // This convention ensures that the second-to-last decrement synchronizes with |
| // (in the language of 1.10 in the C++ standard) the final decrement of a |
| // reference count. Since reference counts are only updated using atomic |
| // read-modify-write operations, this also extends to any earlier decrements. |
| // (See "release sequence" in 1.10.) |
| // |
| // Since all operations on an object happen before the corresponding reference |
| // count decrement, and all reference count decrements happen before the final |
| // one, we are guaranteed that all other object accesses happen before the |
| // object is destroyed. |
| |
| |
| #define INITIAL_STRONG_VALUE (1<<28) |
| |
| #define MAX_COUNT 0xfffff |
| |
| // Test whether the argument is a clearly invalid strong reference count. |
| // Used only for error checking on the value before an atomic decrement. |
| // Intended to be very cheap. |
| // Note that we cannot just check for excess decrements by comparing to zero |
| // since the object would be deallocated before that. |
| #define BAD_STRONG(c) \ |
| ((c) == 0 || ((c) & (~(MAX_COUNT | INITIAL_STRONG_VALUE))) != 0) |
| |
| // Same for weak counts. |
| #define BAD_WEAK(c) ((c) == 0 || ((c) & (~MAX_COUNT)) != 0) |
| |
| // --------------------------------------------------------------------------- |
| |
| class RefBase::weakref_impl : public RefBase::weakref_type |
| { |
| public: |
| std::atomic<int32_t> mStrong; |
| std::atomic<int32_t> mWeak; |
| RefBase* const mBase; |
| std::atomic<int32_t> mFlags; |
| |
| #if !DEBUG_REFS |
| |
| explicit weakref_impl(RefBase* base) |
| : mStrong(INITIAL_STRONG_VALUE) |
| , mWeak(0) |
| , mBase(base) |
| , mFlags(OBJECT_LIFETIME_STRONG) |
| { |
| } |
| |
| void addStrongRef(const void* /*id*/) { } |
| void removeStrongRef(const void* /*id*/) { } |
| void renameStrongRefId(const void* /*old_id*/, const void* /*new_id*/) { } |
| void addWeakRef(const void* /*id*/) { } |
| void removeWeakRef(const void* /*id*/) { } |
| void renameWeakRefId(const void* /*old_id*/, const void* /*new_id*/) { } |
| void printRefs() const { } |
| void trackMe(bool, bool) { } |
| |
| #else |
| |
| weakref_impl(RefBase* base) |
| : mStrong(INITIAL_STRONG_VALUE) |
| , mWeak(0) |
| , mBase(base) |
| , mFlags(OBJECT_LIFETIME_STRONG) |
| , mStrongRefs(NULL) |
| , mWeakRefs(NULL) |
| , mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT) |
| , mRetain(false) |
| { |
| } |
| |
| ~weakref_impl() |
| { |
| bool dumpStack = false; |
| if (!mRetain && mStrongRefs != NULL) { |
| dumpStack = true; |
| ALOGE("Strong references remain:"); |
| ref_entry* refs = mStrongRefs; |
| while (refs) { |
| char inc = refs->ref >= 0 ? '+' : '-'; |
| ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref); |
| #if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED |
| CallStack::logStack(LOG_TAG, refs->stack.get()); |
| #endif |
| refs = refs->next; |
| } |
| } |
| |
| if (!mRetain && mWeakRefs != NULL) { |
| dumpStack = true; |
| ALOGE("Weak references remain!"); |
| ref_entry* refs = mWeakRefs; |
| while (refs) { |
| char inc = refs->ref >= 0 ? '+' : '-'; |
| ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref); |
| #if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED |
| CallStack::logStack(LOG_TAG, refs->stack.get()); |
| #endif |
| refs = refs->next; |
| } |
| } |
| if (dumpStack) { |
| ALOGE("above errors at:"); |
| #if CALLSTACK_ENABLED |
| CallStack::logStack(LOG_TAG); |
| #endif |
| } |
| } |
| |
| void addStrongRef(const void* id) { |
| //ALOGD_IF(mTrackEnabled, |
| // "addStrongRef: RefBase=%p, id=%p", mBase, id); |
| addRef(&mStrongRefs, id, mStrong.load(std::memory_order_relaxed)); |
| } |
| |
| void removeStrongRef(const void* id) { |
| //ALOGD_IF(mTrackEnabled, |
| // "removeStrongRef: RefBase=%p, id=%p", mBase, id); |
| if (!mRetain) { |
| removeRef(&mStrongRefs, id); |
| } else { |
| addRef(&mStrongRefs, id, -mStrong.load(std::memory_order_relaxed)); |
| } |
| } |
| |
| void renameStrongRefId(const void* old_id, const void* new_id) { |
| //ALOGD_IF(mTrackEnabled, |
| // "renameStrongRefId: RefBase=%p, oid=%p, nid=%p", |
| // mBase, old_id, new_id); |
| renameRefsId(mStrongRefs, old_id, new_id); |
| } |
| |
| void addWeakRef(const void* id) { |
| addRef(&mWeakRefs, id, mWeak.load(std::memory_order_relaxed)); |
| } |
| |
| void removeWeakRef(const void* id) { |
| if (!mRetain) { |
| removeRef(&mWeakRefs, id); |
| } else { |
| addRef(&mWeakRefs, id, -mWeak.load(std::memory_order_relaxed)); |
| } |
| } |
| |
| void renameWeakRefId(const void* old_id, const void* new_id) { |
| renameRefsId(mWeakRefs, old_id, new_id); |
| } |
| |
| void trackMe(bool track, bool retain) { |
| mTrackEnabled = track; |
| mRetain = retain; |
| } |
| |
| void printRefs() const |
| { |
| String8 text; |
| |
| { |
| Mutex::Autolock _l(mMutex); |
| char buf[128]; |
| snprintf(buf, sizeof(buf), |
| "Strong references on RefBase %p (weakref_type %p):\n", |
| mBase, this); |
| text.append(buf); |
| printRefsLocked(&text, mStrongRefs); |
| snprintf(buf, sizeof(buf), |
| "Weak references on RefBase %p (weakref_type %p):\n", |
| mBase, this); |
| text.append(buf); |
| printRefsLocked(&text, mWeakRefs); |
| } |
| |
| { |
| char name[100]; |
| snprintf(name, sizeof(name), DEBUG_REFS_CALLSTACK_PATH "/%p.stack", |
| this); |
| int rc = open(name, O_RDWR | O_CREAT | O_APPEND, 644); |
| if (rc >= 0) { |
| (void)write(rc, text.string(), text.length()); |
| close(rc); |
| ALOGD("STACK TRACE for %p saved in %s", this, name); |
| } |
| else ALOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this, |
| name, strerror(errno)); |
| } |
| } |
| |
| private: |
| struct ref_entry |
| { |
| ref_entry* next; |
| const void* id; |
| #if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED |
| CallStack::CallStackUPtr stack; |
| #endif |
| int32_t ref; |
| }; |
| |
| void addRef(ref_entry** refs, const void* id, int32_t mRef) |
| { |
| if (mTrackEnabled) { |
| AutoMutex _l(mMutex); |
| |
| ref_entry* ref = new ref_entry; |
| // Reference count at the time of the snapshot, but before the |
| // update. Positive value means we increment, negative--we |
| // decrement the reference count. |
| ref->ref = mRef; |
| ref->id = id; |
| #if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED |
| ref->stack = CallStack::getCurrent(2); |
| #endif |
| ref->next = *refs; |
| *refs = ref; |
| } |
| } |
| |
| void removeRef(ref_entry** refs, const void* id) |
| { |
| if (mTrackEnabled) { |
| AutoMutex _l(mMutex); |
| |
| ref_entry* const head = *refs; |
| ref_entry* ref = head; |
| while (ref != NULL) { |
| if (ref->id == id) { |
| *refs = ref->next; |
| delete ref; |
| return; |
| } |
| refs = &ref->next; |
| ref = *refs; |
| } |
| |
| ALOGE("RefBase: removing id %p on RefBase %p" |
| "(weakref_type %p) that doesn't exist!", |
| id, mBase, this); |
| |
| ref = head; |
| while (ref) { |
| char inc = ref->ref >= 0 ? '+' : '-'; |
| ALOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref); |
| ref = ref->next; |
| } |
| |
| #if CALLSTACK_ENABLED |
| CallStack::logStack(LOG_TAG); |
| #endif |
| } |
| } |
| |
| void renameRefsId(ref_entry* r, const void* old_id, const void* new_id) |
| { |
| if (mTrackEnabled) { |
| AutoMutex _l(mMutex); |
| ref_entry* ref = r; |
| while (ref != NULL) { |
| if (ref->id == old_id) { |
| ref->id = new_id; |
| } |
| ref = ref->next; |
| } |
| } |
| } |
| |
| void printRefsLocked(String8* out, const ref_entry* refs) const |
| { |
| char buf[128]; |
| while (refs) { |
| char inc = refs->ref >= 0 ? '+' : '-'; |
| snprintf(buf, sizeof(buf), "\t%c ID %p (ref %d):\n", |
| inc, refs->id, refs->ref); |
| out->append(buf); |
| #if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED |
| out->append(CallStack::stackToString("\t\t", refs->stack.get())); |
| #else |
| out->append("\t\t(call stacks disabled)"); |
| #endif |
| refs = refs->next; |
| } |
| } |
| |
| mutable Mutex mMutex; |
| ref_entry* mStrongRefs; |
| ref_entry* mWeakRefs; |
| |
| bool mTrackEnabled; |
| // Collect stack traces on addref and removeref, instead of deleting the stack references |
| // on removeref that match the address ones. |
| bool mRetain; |
| |
| #endif |
| }; |
| |
| // --------------------------------------------------------------------------- |
| |
| void RefBase::incStrong(const void* id) const |
| { |
| weakref_impl* const refs = mRefs; |
| refs->incWeak(id); |
| |
| refs->addStrongRef(id); |
| const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed); |
| ALOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs); |
| #if PRINT_REFS |
| ALOGD("incStrong of %p from %p: cnt=%d\n", this, id, c); |
| #endif |
| if (c != INITIAL_STRONG_VALUE) { |
| return; |
| } |
| |
| int32_t old __unused = refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE, std::memory_order_relaxed); |
| // A decStrong() must still happen after us. |
| ALOG_ASSERT(old > INITIAL_STRONG_VALUE, "0x%x too small", old); |
| refs->mBase->onFirstRef(); |
| } |
| |
| void RefBase::incStrongRequireStrong(const void* id) const { |
| weakref_impl* const refs = mRefs; |
| refs->incWeak(id); |
| |
| refs->addStrongRef(id); |
| const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed); |
| |
| LOG_ALWAYS_FATAL_IF(c <= 0 || c == INITIAL_STRONG_VALUE, |
| "incStrongRequireStrong() called on %p which isn't already owned", refs); |
| #if PRINT_REFS |
| ALOGD("incStrong (requiring strong) of %p from %p: cnt=%d\n", this, id, c); |
| #endif |
| } |
| |
| void RefBase::decStrong(const void* id) const |
| { |
| weakref_impl* const refs = mRefs; |
| refs->removeStrongRef(id); |
| const int32_t c = refs->mStrong.fetch_sub(1, std::memory_order_release); |
| #if PRINT_REFS |
| ALOGD("decStrong of %p from %p: cnt=%d\n", this, id, c); |
| #endif |
| LOG_ALWAYS_FATAL_IF(BAD_STRONG(c), "decStrong() called on %p too many times", |
| refs); |
| if (c == 1) { |
| std::atomic_thread_fence(std::memory_order_acquire); |
| refs->mBase->onLastStrongRef(id); |
| int32_t flags = refs->mFlags.load(std::memory_order_relaxed); |
| if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) { |
| delete this; |
| // The destructor does not delete refs in this case. |
| } |
| } |
| // Note that even with only strong reference operations, the thread |
| // deallocating this may not be the same as the thread deallocating refs. |
| // That's OK: all accesses to this happen before its deletion here, |
| // and all accesses to refs happen before its deletion in the final decWeak. |
| // The destructor can safely access mRefs because either it's deleting |
| // mRefs itself, or it's running entirely before the final mWeak decrement. |
| // |
| // Since we're doing atomic loads of `flags`, the static analyzer assumes |
| // they can change between `delete this;` and `refs->decWeak(id);`. This is |
| // not the case. The analyzer may become more okay with this patten when |
| // https://bugs.llvm.org/show_bug.cgi?id=34365 gets resolved. NOLINTNEXTLINE |
| refs->decWeak(id); |
| } |
| |
| void RefBase::forceIncStrong(const void* id) const |
| { |
| // Allows initial mStrong of 0 in addition to INITIAL_STRONG_VALUE. |
| // TODO: Better document assumptions. |
| weakref_impl* const refs = mRefs; |
| refs->incWeak(id); |
| |
| refs->addStrongRef(id); |
| const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed); |
| ALOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow", |
| refs); |
| #if PRINT_REFS |
| ALOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c); |
| #endif |
| |
| switch (c) { |
| case INITIAL_STRONG_VALUE: |
| refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE, |
| std::memory_order_relaxed); |
| FALLTHROUGH_INTENDED; |
| case 0: |
| refs->mBase->onFirstRef(); |
| } |
| } |
| |
| int32_t RefBase::getStrongCount() const |
| { |
| // Debugging only; No memory ordering guarantees. |
| return mRefs->mStrong.load(std::memory_order_relaxed); |
| } |
| |
| RefBase* RefBase::weakref_type::refBase() const |
| { |
| return static_cast<const weakref_impl*>(this)->mBase; |
| } |
| |
| void RefBase::weakref_type::incWeak(const void* id) |
| { |
| weakref_impl* const impl = static_cast<weakref_impl*>(this); |
| impl->addWeakRef(id); |
| const int32_t c __unused = impl->mWeak.fetch_add(1, |
| std::memory_order_relaxed); |
| ALOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this); |
| } |
| |
| void RefBase::weakref_type::incWeakRequireWeak(const void* id) |
| { |
| weakref_impl* const impl = static_cast<weakref_impl*>(this); |
| impl->addWeakRef(id); |
| const int32_t c __unused = impl->mWeak.fetch_add(1, |
| std::memory_order_relaxed); |
| LOG_ALWAYS_FATAL_IF(c <= 0, "incWeakRequireWeak called on %p which has no weak refs", this); |
| } |
| |
| void RefBase::weakref_type::decWeak(const void* id) |
| { |
| weakref_impl* const impl = static_cast<weakref_impl*>(this); |
| impl->removeWeakRef(id); |
| const int32_t c = impl->mWeak.fetch_sub(1, std::memory_order_release); |
| LOG_ALWAYS_FATAL_IF(BAD_WEAK(c), "decWeak called on %p too many times", |
| this); |
| if (c != 1) return; |
| atomic_thread_fence(std::memory_order_acquire); |
| |
| int32_t flags = impl->mFlags.load(std::memory_order_relaxed); |
| if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) { |
| // This is the regular lifetime case. The object is destroyed |
| // when the last strong reference goes away. Since weakref_impl |
| // outlives the object, it is not destroyed in the dtor, and |
| // we'll have to do it here. |
| if (impl->mStrong.load(std::memory_order_relaxed) |
| == INITIAL_STRONG_VALUE) { |
| // Decrementing a weak count to zero when object never had a strong |
| // reference. We assume it acquired a weak reference early, e.g. |
| // in the constructor, and will eventually be properly destroyed, |
| // usually via incrementing and decrementing the strong count. |
| // Thus we no longer do anything here. We log this case, since it |
| // seems to be extremely rare, and should not normally occur. We |
| // used to deallocate mBase here, so this may now indicate a leak. |
| ALOGW("RefBase: Object at %p lost last weak reference " |
| "before it had a strong reference", impl->mBase); |
| } else { |
| // ALOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase); |
| delete impl; |
| } |
| } else { |
| // This is the OBJECT_LIFETIME_WEAK case. The last weak-reference |
| // is gone, we can destroy the object. |
| impl->mBase->onLastWeakRef(id); |
| delete impl->mBase; |
| } |
| } |
| |
| bool RefBase::weakref_type::attemptIncStrong(const void* id) |
| { |
| incWeak(id); |
| |
| weakref_impl* const impl = static_cast<weakref_impl*>(this); |
| int32_t curCount = impl->mStrong.load(std::memory_order_relaxed); |
| |
| ALOG_ASSERT(curCount >= 0, |
| "attemptIncStrong called on %p after underflow", this); |
| |
| while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) { |
| // we're in the easy/common case of promoting a weak-reference |
| // from an existing strong reference. |
| if (impl->mStrong.compare_exchange_weak(curCount, curCount+1, |
| std::memory_order_relaxed)) { |
| break; |
| } |
| // the strong count has changed on us, we need to re-assert our |
| // situation. curCount was updated by compare_exchange_weak. |
| } |
| |
| if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) { |
| // we're now in the harder case of either: |
| // - there never was a strong reference on us |
| // - or, all strong references have been released |
| int32_t flags = impl->mFlags.load(std::memory_order_relaxed); |
| if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) { |
| // this object has a "normal" life-time, i.e.: it gets destroyed |
| // when the last strong reference goes away |
| if (curCount <= 0) { |
| // the last strong-reference got released, the object cannot |
| // be revived. |
| decWeak(id); |
| return false; |
| } |
| |
| // here, curCount == INITIAL_STRONG_VALUE, which means |
| // there never was a strong-reference, so we can try to |
| // promote this object; we need to do that atomically. |
| while (curCount > 0) { |
| if (impl->mStrong.compare_exchange_weak(curCount, curCount+1, |
| std::memory_order_relaxed)) { |
| break; |
| } |
| // the strong count has changed on us, we need to re-assert our |
| // situation (e.g.: another thread has inc/decStrong'ed us) |
| // curCount has been updated. |
| } |
| |
| if (curCount <= 0) { |
| // promote() failed, some other thread destroyed us in the |
| // meantime (i.e.: strong count reached zero). |
| decWeak(id); |
| return false; |
| } |
| } else { |
| // this object has an "extended" life-time, i.e.: it can be |
| // revived from a weak-reference only. |
| // Ask the object's implementation if it agrees to be revived |
| if (!impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id)) { |
| // it didn't so give-up. |
| decWeak(id); |
| return false; |
| } |
| // grab a strong-reference, which is always safe due to the |
| // extended life-time. |
| curCount = impl->mStrong.fetch_add(1, std::memory_order_relaxed); |
| // If the strong reference count has already been incremented by |
| // someone else, the implementor of onIncStrongAttempted() is holding |
| // an unneeded reference. So call onLastStrongRef() here to remove it. |
| // (No, this is not pretty.) Note that we MUST NOT do this if we |
| // are in fact acquiring the first reference. |
| if (curCount != 0 && curCount != INITIAL_STRONG_VALUE) { |
| impl->mBase->onLastStrongRef(id); |
| } |
| } |
| } |
| |
| impl->addStrongRef(id); |
| |
| #if PRINT_REFS |
| ALOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount); |
| #endif |
| |
| // curCount is the value of mStrong before we incremented it. |
| // Now we need to fix-up the count if it was INITIAL_STRONG_VALUE. |
| // This must be done safely, i.e.: handle the case where several threads |
| // were here in attemptIncStrong(). |
| // curCount > INITIAL_STRONG_VALUE is OK, and can happen if we're doing |
| // this in the middle of another incStrong. The subtraction is handled |
| // by the thread that started with INITIAL_STRONG_VALUE. |
| if (curCount == INITIAL_STRONG_VALUE) { |
| impl->mStrong.fetch_sub(INITIAL_STRONG_VALUE, |
| std::memory_order_relaxed); |
| } |
| |
| return true; |
| } |
| |
| bool RefBase::weakref_type::attemptIncWeak(const void* id) |
| { |
| weakref_impl* const impl = static_cast<weakref_impl*>(this); |
| |
| int32_t curCount = impl->mWeak.load(std::memory_order_relaxed); |
| ALOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow", |
| this); |
| while (curCount > 0) { |
| if (impl->mWeak.compare_exchange_weak(curCount, curCount+1, |
| std::memory_order_relaxed)) { |
| break; |
| } |
| // curCount has been updated. |
| } |
| |
| if (curCount > 0) { |
| impl->addWeakRef(id); |
| } |
| |
| return curCount > 0; |
| } |
| |
| int32_t RefBase::weakref_type::getWeakCount() const |
| { |
| // Debug only! |
| return static_cast<const weakref_impl*>(this)->mWeak |
| .load(std::memory_order_relaxed); |
| } |
| |
| void RefBase::weakref_type::printRefs() const |
| { |
| static_cast<const weakref_impl*>(this)->printRefs(); |
| } |
| |
| void RefBase::weakref_type::trackMe(bool enable, bool retain) |
| { |
| static_cast<weakref_impl*>(this)->trackMe(enable, retain); |
| } |
| |
| RefBase::weakref_type* RefBase::createWeak(const void* id) const |
| { |
| mRefs->incWeak(id); |
| return mRefs; |
| } |
| |
| RefBase::weakref_type* RefBase::getWeakRefs() const |
| { |
| return mRefs; |
| } |
| |
| RefBase::RefBase() |
| : mRefs(new weakref_impl(this)) |
| { |
| } |
| |
| RefBase::~RefBase() |
| { |
| int32_t flags = mRefs->mFlags.load(std::memory_order_relaxed); |
| // Life-time of this object is extended to WEAK, in |
| // which case weakref_impl doesn't out-live the object and we |
| // can free it now. |
| if ((flags & OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_WEAK) { |
| // It's possible that the weak count is not 0 if the object |
| // re-acquired a weak reference in its destructor |
| if (mRefs->mWeak.load(std::memory_order_relaxed) == 0) { |
| delete mRefs; |
| } |
| } else if (mRefs->mStrong.load(std::memory_order_relaxed) == INITIAL_STRONG_VALUE) { |
| // We never acquired a strong reference on this object. |
| #if DEBUG_REFBASE_DESTRUCTION |
| // Treating this as fatal is prone to causing boot loops. For debugging, it's |
| // better to treat as non-fatal. |
| ALOGD("RefBase: Explicit destruction, weak count = %d (in %p)", mRefs->mWeak.load(), this); |
| |
| #if CALLSTACK_ENABLED |
| CallStack::logStack(LOG_TAG); |
| #endif |
| #else |
| LOG_ALWAYS_FATAL("RefBase: Explicit destruction, weak count = %d", mRefs->mWeak.load()); |
| #endif |
| } |
| // For debugging purposes, clear mRefs. Ineffective against outstanding wp's. |
| const_cast<weakref_impl*&>(mRefs) = nullptr; |
| } |
| |
| void RefBase::extendObjectLifetime(int32_t mode) |
| { |
| // Must be happens-before ordered with respect to construction or any |
| // operation that could destroy the object. |
| mRefs->mFlags.fetch_or(mode, std::memory_order_relaxed); |
| } |
| |
| void RefBase::onFirstRef() |
| { |
| } |
| |
| void RefBase::onLastStrongRef(const void* /*id*/) |
| { |
| } |
| |
| bool RefBase::onIncStrongAttempted(uint32_t flags, const void* /*id*/) |
| { |
| return (flags&FIRST_INC_STRONG) ? true : false; |
| } |
| |
| void RefBase::onLastWeakRef(const void* /*id*/) |
| { |
| } |
| |
| // --------------------------------------------------------------------------- |
| |
| #if DEBUG_REFS |
| void RefBase::renameRefs(size_t n, const ReferenceRenamer& renamer) { |
| for (size_t i=0 ; i<n ; i++) { |
| renamer(i); |
| } |
| } |
| #else |
| void RefBase::renameRefs(size_t /*n*/, const ReferenceRenamer& /*renamer*/) { } |
| #endif |
| |
| void RefBase::renameRefId(weakref_type* ref, |
| const void* old_id, const void* new_id) { |
| weakref_impl* const impl = static_cast<weakref_impl*>(ref); |
| impl->renameStrongRefId(old_id, new_id); |
| impl->renameWeakRefId(old_id, new_id); |
| } |
| |
| void RefBase::renameRefId(RefBase* ref, |
| const void* old_id, const void* new_id) { |
| ref->mRefs->renameStrongRefId(old_id, new_id); |
| ref->mRefs->renameWeakRefId(old_id, new_id); |
| } |
| |
| }; // namespace android |