781 lines
27 KiB
C++
781 lines
27 KiB
C++
/*
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* Copyright (C) 2005 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "RefBase"
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// #define LOG_NDEBUG 0
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#include <memory>
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#include <android-base/macros.h>
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#include <utils/RefBase.h>
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#include <utils/CallStack.h>
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#include <utils/Mutex.h>
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#ifndef __unused
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#define __unused __attribute__((__unused__))
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#endif
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// Compile with refcounting debugging enabled.
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#define DEBUG_REFS 0
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// The following three are ignored unless DEBUG_REFS is set.
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// whether ref-tracking is enabled by default, if not, trackMe(true, false)
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// needs to be called explicitly
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#define DEBUG_REFS_ENABLED_BY_DEFAULT 0
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// whether callstack are collected (significantly slows things down)
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#define DEBUG_REFS_CALLSTACK_ENABLED 1
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// folder where stack traces are saved when DEBUG_REFS is enabled
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// this folder needs to exist and be writable
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#define DEBUG_REFS_CALLSTACK_PATH "/data/debug"
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// log all reference counting operations
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#define PRINT_REFS 0
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// Continue after logging a stack trace if ~RefBase discovers that reference
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// count has never been incremented. Normally we conspicuously crash in that
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// case.
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#define DEBUG_REFBASE_DESTRUCTION 1
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// ---------------------------------------------------------------------------
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namespace android {
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// Observations, invariants, etc:
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// By default, obects are destroyed when the last strong reference disappears
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// or, if the object never had a strong reference, when the last weak reference
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// disappears.
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//
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// OBJECT_LIFETIME_WEAK changes this behavior to retain the object
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// unconditionally until the last reference of either kind disappears. The
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// client ensures that the extendObjectLifetime call happens before the dec
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// call that would otherwise have deallocated the object, or before an
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// attemptIncStrong call that might rely on it. We do not worry about
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// concurrent changes to the object lifetime.
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//
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// AttemptIncStrong will succeed if the object has a strong reference, or if it
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// has a weak reference and has never had a strong reference.
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// AttemptIncWeak really does succeed only if there is already a WEAK
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// reference, and thus may fail when attemptIncStrong would succeed.
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//
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// mStrong is the strong reference count. mWeak is the weak reference count.
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// Between calls, and ignoring memory ordering effects, mWeak includes strong
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// references, and is thus >= mStrong.
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//
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// A weakref_impl holds all the information, including both reference counts,
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// required to perform wp<> operations. Thus these can continue to be performed
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// after the RefBase object has been destroyed.
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//
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// A weakref_impl is allocated as the value of mRefs in a RefBase object on
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// construction.
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// In the OBJECT_LIFETIME_STRONG case, it is normally deallocated in decWeak,
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// and hence lives as long as the last weak reference. (It can also be
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// deallocated in the RefBase destructor iff the strong reference count was
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// never incremented and the weak count is zero, e.g. if the RefBase object is
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// explicitly destroyed without decrementing the strong count. This should be
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// avoided.) In this case, the RefBase destructor should be invoked from
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// decStrong.
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// In the OBJECT_LIFETIME_WEAK case, the weakref_impl is always deallocated in
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// the RefBase destructor, which is always invoked by decWeak. DecStrong
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// explicitly avoids the deletion in this case.
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//
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// Memory ordering:
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// The client must ensure that every inc() call, together with all other
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// accesses to the object, happens before the corresponding dec() call.
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//
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// We try to keep memory ordering constraints on atomics as weak as possible,
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// since memory fences or ordered memory accesses are likely to be a major
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// performance cost for this code. All accesses to mStrong, mWeak, and mFlags
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// explicitly relax memory ordering in some way.
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//
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// The only operations that are not memory_order_relaxed are reference count
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// decrements. All reference count decrements are release operations. In
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// addition, the final decrement leading the deallocation is followed by an
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// acquire fence, which we can view informally as also turning it into an
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// acquire operation. (See 29.8p4 [atomics.fences] for details. We could
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// alternatively use acq_rel operations for all decrements. This is probably
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// slower on most current (2016) hardware, especially on ARMv7, but that may
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// not be true indefinitely.)
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//
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// This convention ensures that the second-to-last decrement synchronizes with
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// (in the language of 1.10 in the C++ standard) the final decrement of a
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// reference count. Since reference counts are only updated using atomic
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// read-modify-write operations, this also extends to any earlier decrements.
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// (See "release sequence" in 1.10.)
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//
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// Since all operations on an object happen before the corresponding reference
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// count decrement, and all reference count decrements happen before the final
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// one, we are guaranteed that all other object accesses happen before the
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// object is destroyed.
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#define INITIAL_STRONG_VALUE (1<<28)
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#define MAX_COUNT 0xfffff
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// Test whether the argument is a clearly invalid strong reference count.
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// Used only for error checking on the value before an atomic decrement.
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// Intended to be very cheap.
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// Note that we cannot just check for excess decrements by comparing to zero
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// since the object would be deallocated before that.
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#define BAD_STRONG(c) \
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((c) == 0 || ((c) & (~(MAX_COUNT | INITIAL_STRONG_VALUE))) != 0)
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// Same for weak counts.
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#define BAD_WEAK(c) ((c) == 0 || ((c) & (~MAX_COUNT)) != 0)
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// ---------------------------------------------------------------------------
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class RefBase::weakref_impl : public RefBase::weakref_type
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{
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public:
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std::atomic<int32_t> mStrong;
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std::atomic<int32_t> mWeak;
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RefBase* const mBase;
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std::atomic<int32_t> mFlags;
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#if !DEBUG_REFS
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explicit weakref_impl(RefBase* base)
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: mStrong(INITIAL_STRONG_VALUE)
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, mWeak(0)
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, mBase(base)
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, mFlags(0)
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{
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}
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void addStrongRef(const void* /*id*/) { }
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void removeStrongRef(const void* /*id*/) { }
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void renameStrongRefId(const void* /*old_id*/, const void* /*new_id*/) { }
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void addWeakRef(const void* /*id*/) { }
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void removeWeakRef(const void* /*id*/) { }
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void renameWeakRefId(const void* /*old_id*/, const void* /*new_id*/) { }
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void printRefs() const { }
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void trackMe(bool, bool) { }
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#else
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weakref_impl(RefBase* base)
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: mStrong(INITIAL_STRONG_VALUE)
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, mWeak(0)
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, mBase(base)
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, mFlags(0)
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, mStrongRefs(NULL)
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, mWeakRefs(NULL)
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, mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
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, mRetain(false)
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{
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}
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~weakref_impl()
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{
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bool dumpStack = false;
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if (!mRetain && mStrongRefs != NULL) {
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dumpStack = true;
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ALOGE("Strong references remain:");
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ref_entry* refs = mStrongRefs;
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while (refs) {
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char inc = refs->ref >= 0 ? '+' : '-';
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ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
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#if DEBUG_REFS_CALLSTACK_ENABLED
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CallStack::logStack(LOG_TAG, refs->stack.get());
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#endif
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refs = refs->next;
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}
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}
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if (!mRetain && mWeakRefs != NULL) {
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dumpStack = true;
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ALOGE("Weak references remain!");
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ref_entry* refs = mWeakRefs;
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while (refs) {
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char inc = refs->ref >= 0 ? '+' : '-';
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ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
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#if DEBUG_REFS_CALLSTACK_ENABLED
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CallStack::logStack(LOG_TAG, refs->stack.get());
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#endif
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refs = refs->next;
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}
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}
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if (dumpStack) {
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ALOGE("above errors at:");
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CallStack::logStack(LOG_TAG);
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}
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}
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void addStrongRef(const void* id) {
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//ALOGD_IF(mTrackEnabled,
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// "addStrongRef: RefBase=%p, id=%p", mBase, id);
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addRef(&mStrongRefs, id, mStrong.load(std::memory_order_relaxed));
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}
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void removeStrongRef(const void* id) {
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//ALOGD_IF(mTrackEnabled,
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// "removeStrongRef: RefBase=%p, id=%p", mBase, id);
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if (!mRetain) {
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removeRef(&mStrongRefs, id);
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} else {
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addRef(&mStrongRefs, id, -mStrong.load(std::memory_order_relaxed));
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}
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}
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void renameStrongRefId(const void* old_id, const void* new_id) {
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//ALOGD_IF(mTrackEnabled,
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// "renameStrongRefId: RefBase=%p, oid=%p, nid=%p",
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// mBase, old_id, new_id);
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renameRefsId(mStrongRefs, old_id, new_id);
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}
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void addWeakRef(const void* id) {
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addRef(&mWeakRefs, id, mWeak.load(std::memory_order_relaxed));
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}
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void removeWeakRef(const void* id) {
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if (!mRetain) {
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removeRef(&mWeakRefs, id);
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} else {
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addRef(&mWeakRefs, id, -mWeak.load(std::memory_order_relaxed));
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}
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}
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void renameWeakRefId(const void* old_id, const void* new_id) {
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renameRefsId(mWeakRefs, old_id, new_id);
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}
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void trackMe(bool track, bool retain)
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{
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mTrackEnabled = track;
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mRetain = retain;
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}
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void printRefs() const
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{
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String8 text;
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{
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Mutex::Autolock _l(mMutex);
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char buf[128];
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snprintf(buf, sizeof(buf),
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"Strong references on RefBase %p (weakref_type %p):\n",
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mBase, this);
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text.append(buf);
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printRefsLocked(&text, mStrongRefs);
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snprintf(buf, sizeof(buf),
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"Weak references on RefBase %p (weakref_type %p):\n",
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mBase, this);
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text.append(buf);
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printRefsLocked(&text, mWeakRefs);
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}
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{
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char name[100];
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snprintf(name, sizeof(name), DEBUG_REFS_CALLSTACK_PATH "/%p.stack",
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this);
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int rc = open(name, O_RDWR | O_CREAT | O_APPEND, 644);
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if (rc >= 0) {
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(void)write(rc, text.string(), text.length());
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close(rc);
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ALOGD("STACK TRACE for %p saved in %s", this, name);
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}
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else ALOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this,
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name, strerror(errno));
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}
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}
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private:
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struct ref_entry
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{
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ref_entry* next;
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const void* id;
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#if DEBUG_REFS_CALLSTACK_ENABLED
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CallStack::CallStackUPtr stack;
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#endif
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int32_t ref;
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};
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void addRef(ref_entry** refs, const void* id, int32_t mRef)
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{
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if (mTrackEnabled) {
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AutoMutex _l(mMutex);
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ref_entry* ref = new ref_entry;
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// Reference count at the time of the snapshot, but before the
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// update. Positive value means we increment, negative--we
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// decrement the reference count.
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ref->ref = mRef;
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ref->id = id;
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#if DEBUG_REFS_CALLSTACK_ENABLED
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ref->stack = CallStack::getCurrent(2);
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#endif
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ref->next = *refs;
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*refs = ref;
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}
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}
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void removeRef(ref_entry** refs, const void* id)
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{
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if (mTrackEnabled) {
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AutoMutex _l(mMutex);
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ref_entry* const head = *refs;
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ref_entry* ref = head;
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while (ref != NULL) {
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if (ref->id == id) {
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*refs = ref->next;
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delete ref;
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return;
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}
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refs = &ref->next;
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ref = *refs;
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}
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ALOGE("RefBase: removing id %p on RefBase %p"
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"(weakref_type %p) that doesn't exist!",
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id, mBase, this);
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ref = head;
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while (ref) {
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char inc = ref->ref >= 0 ? '+' : '-';
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ALOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref);
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ref = ref->next;
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}
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CallStack::logStack(LOG_TAG);
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}
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}
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void renameRefsId(ref_entry* r, const void* old_id, const void* new_id)
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{
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if (mTrackEnabled) {
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AutoMutex _l(mMutex);
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ref_entry* ref = r;
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while (ref != NULL) {
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if (ref->id == old_id) {
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ref->id = new_id;
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}
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ref = ref->next;
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}
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}
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}
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void printRefsLocked(String8* out, const ref_entry* refs) const
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{
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char buf[128];
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while (refs) {
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char inc = refs->ref >= 0 ? '+' : '-';
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snprintf(buf, sizeof(buf), "\t%c ID %p (ref %d):\n",
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inc, refs->id, refs->ref);
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out->append(buf);
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#if DEBUG_REFS_CALLSTACK_ENABLED
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out->append(CallStack::stackToString("\t\t", refs->stack.get()));
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#else
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out->append("\t\t(call stacks disabled)");
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#endif
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refs = refs->next;
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}
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}
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mutable Mutex mMutex;
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ref_entry* mStrongRefs;
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ref_entry* mWeakRefs;
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bool mTrackEnabled;
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// Collect stack traces on addref and removeref, instead of deleting the stack references
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// on removeref that match the address ones.
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bool mRetain;
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#endif
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};
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// ---------------------------------------------------------------------------
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void RefBase::incStrong(const void* id) const
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{
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weakref_impl* const refs = mRefs;
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refs->incWeak(id);
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refs->addStrongRef(id);
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const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed);
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ALOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
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#if PRINT_REFS
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ALOGD("incStrong of %p from %p: cnt=%d\n", this, id, c);
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#endif
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if (c != INITIAL_STRONG_VALUE) {
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return;
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}
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int32_t old __unused = refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE, std::memory_order_relaxed);
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// A decStrong() must still happen after us.
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ALOG_ASSERT(old > INITIAL_STRONG_VALUE, "0x%x too small", old);
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refs->mBase->onFirstRef();
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}
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void RefBase::decStrong(const void* id) const
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{
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weakref_impl* const refs = mRefs;
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refs->removeStrongRef(id);
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const int32_t c = refs->mStrong.fetch_sub(1, std::memory_order_release);
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#if PRINT_REFS
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ALOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
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#endif
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LOG_ALWAYS_FATAL_IF(BAD_STRONG(c), "decStrong() called on %p too many times",
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refs);
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if (c == 1) {
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std::atomic_thread_fence(std::memory_order_acquire);
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refs->mBase->onLastStrongRef(id);
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int32_t flags = refs->mFlags.load(std::memory_order_relaxed);
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if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
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delete this;
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// The destructor does not delete refs in this case.
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}
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}
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// Note that even with only strong reference operations, the thread
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// deallocating this may not be the same as the thread deallocating refs.
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// That's OK: all accesses to this happen before its deletion here,
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// and all accesses to refs happen before its deletion in the final decWeak.
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// The destructor can safely access mRefs because either it's deleting
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// mRefs itself, or it's running entirely before the final mWeak decrement.
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//
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// Since we're doing atomic loads of `flags`, the static analyzer assumes
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// they can change between `delete this;` and `refs->decWeak(id);`. This is
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// not the case. The analyzer may become more okay with this patten when
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// https://bugs.llvm.org/show_bug.cgi?id=34365 gets resolved. NOLINTNEXTLINE
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refs->decWeak(id);
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}
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void RefBase::forceIncStrong(const void* id) const
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{
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// Allows initial mStrong of 0 in addition to INITIAL_STRONG_VALUE.
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// TODO: Better document assumptions.
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weakref_impl* const refs = mRefs;
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refs->incWeak(id);
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refs->addStrongRef(id);
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const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed);
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ALOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
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refs);
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#if PRINT_REFS
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ALOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
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#endif
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switch (c) {
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case INITIAL_STRONG_VALUE:
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refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE,
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std::memory_order_relaxed);
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FALLTHROUGH_INTENDED;
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case 0:
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refs->mBase->onFirstRef();
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}
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}
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int32_t RefBase::getStrongCount() const
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{
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// Debugging only; No memory ordering guarantees.
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return mRefs->mStrong.load(std::memory_order_relaxed);
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}
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RefBase* RefBase::weakref_type::refBase() const
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|
{
|
|
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::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);
|
|
CallStack::logStack(LOG_TAG);
|
|
#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
|