534 lines
14 KiB
C++
534 lines
14 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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#include <utils/RefBase.h>
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#include <utils/Atomic.h>
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#include <utils/CallStack.h>
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#include <utils/KeyedVector.h>
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#include <utils/Log.h>
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#include <utils/threads.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <typeinfo>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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// compile with refcounting debugging enabled
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#define DEBUG_REFS 0
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#define DEBUG_REFS_ENABLED_BY_DEFAULT 1
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#define DEBUG_REFS_CALLSTACK_ENABLED 1
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// log all reference counting operations
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#define PRINT_REFS 0
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// ---------------------------------------------------------------------------
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namespace android {
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#define INITIAL_STRONG_VALUE (1<<28)
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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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volatile int32_t mStrong;
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volatile int32_t mWeak;
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RefBase* const mBase;
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volatile int32_t mFlags;
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#if !DEBUG_REFS
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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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{
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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 addWeakRef(const void* /*id*/) { }
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void removeWeakRef(const void* /*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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//LOGI("NEW weakref_impl %p for RefBase %p", this, base);
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}
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~weakref_impl()
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{
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LOG_ALWAYS_FATAL_IF(!mRetain && mStrongRefs != NULL, "Strong references remain!");
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LOG_ALWAYS_FATAL_IF(!mRetain && mWeakRefs != NULL, "Weak references remain!");
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}
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void addStrongRef(const void* id)
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{
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addRef(&mStrongRefs, id, mStrong);
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}
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void removeStrongRef(const void* id)
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{
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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);
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}
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void addWeakRef(const void* id)
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{
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addRef(&mWeakRefs, id, mWeak);
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}
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void removeWeakRef(const void* id)
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{
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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);
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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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AutoMutex _l(const_cast<weakref_impl*>(this)->mMutex);
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char buf[128];
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sprintf(buf, "Strong references on RefBase %p (weakref_type %p):\n", mBase, this);
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text.append(buf);
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printRefsLocked(&text, mStrongRefs);
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sprintf(buf, "Weak references on RefBase %p (weakref_type %p):\n", 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, 100, "/data/%p.stack", this);
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int rc = open(name, O_RDWR | O_CREAT | O_APPEND);
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if (rc >= 0) {
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write(rc, text.string(), text.length());
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close(rc);
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LOGD("STACK TRACE for %p saved in %s", this, name);
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}
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else LOGE("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 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.update(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* ref = *refs;
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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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LOG_ALWAYS_FATAL("RefBase: removing id %p on RefBase %p (weakref_type %p) that doesn't exist!",
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id, mBase, this);
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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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sprintf(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(refs->stack.toString("\t\t"));
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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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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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#if 0
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void addRef(KeyedVector<const void*, int32_t>* refs, const void* id)
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{
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AutoMutex _l(mMutex);
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ssize_t i = refs->indexOfKey(id);
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if (i >= 0) {
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++(refs->editValueAt(i));
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} else {
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i = refs->add(id, 1);
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}
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}
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void removeRef(KeyedVector<const void*, int32_t>* refs, const void* id)
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{
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AutoMutex _l(mMutex);
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ssize_t i = refs->indexOfKey(id);
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LOG_ALWAYS_FATAL_IF(i < 0, "RefBase: removing id %p that doesn't exist!", id);
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if (i >= 0) {
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int32_t val = --(refs->editValueAt(i));
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if (val == 0) {
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refs->removeItemsAt(i);
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}
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}
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}
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void printRefs(const KeyedVector<const void*, int32_t>& refs)
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{
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const size_t N=refs.size();
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for (size_t i=0; i<N; i++) {
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printf("\tID %p: %d remain\n", refs.keyAt(i), refs.valueAt(i));
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}
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}
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mutable Mutex mMutex;
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KeyedVector<const void*, int32_t> mStrongRefs;
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KeyedVector<const void*, int32_t> mWeakRefs;
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#endif
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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->addWeakRef(id);
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refs->incWeak(id);
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refs->addStrongRef(id);
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const int32_t c = android_atomic_inc(&refs->mStrong);
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LOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
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#if PRINT_REFS
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LOGD("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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android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
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const_cast<RefBase*>(this)->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 = android_atomic_dec(&refs->mStrong);
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#if PRINT_REFS
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LOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
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#endif
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LOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
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if (c == 1) {
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const_cast<RefBase*>(this)->onLastStrongRef(id);
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if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
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delete this;
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}
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}
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refs->removeWeakRef(id);
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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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weakref_impl* const refs = mRefs;
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refs->addWeakRef(id);
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refs->incWeak(id);
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refs->addStrongRef(id);
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const int32_t c = android_atomic_inc(&refs->mStrong);
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LOG_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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LOGD("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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android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
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// fall through...
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case 0:
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const_cast<RefBase*>(this)->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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return mRefs->mStrong;
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}
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RefBase* RefBase::weakref_type::refBase() const
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{
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return static_cast<const weakref_impl*>(this)->mBase;
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}
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void RefBase::weakref_type::incWeak(const void* id)
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{
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weakref_impl* const impl = static_cast<weakref_impl*>(this);
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impl->addWeakRef(id);
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const int32_t c = android_atomic_inc(&impl->mWeak);
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LOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
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}
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void RefBase::weakref_type::decWeak(const void* id)
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{
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weakref_impl* const impl = static_cast<weakref_impl*>(this);
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impl->removeWeakRef(id);
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const int32_t c = android_atomic_dec(&impl->mWeak);
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LOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
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if (c != 1) return;
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if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
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if (impl->mStrong == INITIAL_STRONG_VALUE)
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delete impl->mBase;
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else {
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// LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
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delete impl;
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}
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} else {
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impl->mBase->onLastWeakRef(id);
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if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
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delete impl->mBase;
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}
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}
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}
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bool RefBase::weakref_type::attemptIncStrong(const void* id)
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{
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incWeak(id);
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weakref_impl* const impl = static_cast<weakref_impl*>(this);
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int32_t curCount = impl->mStrong;
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LOG_ASSERT(curCount >= 0, "attemptIncStrong called on %p after underflow",
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this);
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while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
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if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
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break;
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}
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curCount = impl->mStrong;
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}
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if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
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bool allow;
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if (curCount == INITIAL_STRONG_VALUE) {
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// Attempting to acquire first strong reference... this is allowed
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// if the object does NOT have a longer lifetime (meaning the
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// implementation doesn't need to see this), or if the implementation
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// allows it to happen.
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allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK
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|| impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
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} else {
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// Attempting to revive the object... this is allowed
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// if the object DOES have a longer lifetime (so we can safely
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// call the object with only a weak ref) and the implementation
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// allows it to happen.
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allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_WEAK
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&& impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
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}
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if (!allow) {
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decWeak(id);
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return false;
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}
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curCount = android_atomic_inc(&impl->mStrong);
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// If the strong reference count has already been incremented by
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// someone else, the implementor of onIncStrongAttempted() is holding
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// an unneeded reference. So call onLastStrongRef() here to remove it.
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// (No, this is not pretty.) Note that we MUST NOT do this if we
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// are in fact acquiring the first reference.
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if (curCount > 0 && curCount < INITIAL_STRONG_VALUE) {
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impl->mBase->onLastStrongRef(id);
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}
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}
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impl->addWeakRef(id);
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impl->addStrongRef(id);
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#if PRINT_REFS
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LOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
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#endif
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if (curCount == INITIAL_STRONG_VALUE) {
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android_atomic_add(-INITIAL_STRONG_VALUE, &impl->mStrong);
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impl->mBase->onFirstRef();
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}
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return true;
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}
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bool RefBase::weakref_type::attemptIncWeak(const void* id)
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{
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weakref_impl* const impl = static_cast<weakref_impl*>(this);
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int32_t curCount = impl->mWeak;
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LOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
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this);
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while (curCount > 0) {
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if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mWeak) == 0) {
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break;
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}
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curCount = impl->mWeak;
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}
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if (curCount > 0) {
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impl->addWeakRef(id);
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}
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return curCount > 0;
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}
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int32_t RefBase::weakref_type::getWeakCount() const
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{
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return static_cast<const weakref_impl*>(this)->mWeak;
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}
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void RefBase::weakref_type::printRefs() const
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{
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static_cast<const weakref_impl*>(this)->printRefs();
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}
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void RefBase::weakref_type::trackMe(bool enable, bool retain)
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{
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static_cast<const weakref_impl*>(this)->trackMe(enable, retain);
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}
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RefBase::weakref_type* RefBase::createWeak(const void* id) const
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{
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mRefs->incWeak(id);
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return mRefs;
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}
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RefBase::weakref_type* RefBase::getWeakRefs() const
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{
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return mRefs;
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}
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RefBase::RefBase()
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: mRefs(new weakref_impl(this))
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{
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// LOGV("Creating refs %p with RefBase %p\n", mRefs, this);
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}
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RefBase::~RefBase()
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{
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// LOGV("Destroying RefBase %p (refs %p)\n", this, mRefs);
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if (mRefs->mWeak == 0) {
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// LOGV("Freeing refs %p of old RefBase %p\n", mRefs, this);
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delete mRefs;
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}
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}
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void RefBase::extendObjectLifetime(int32_t mode)
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{
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android_atomic_or(mode, &mRefs->mFlags);
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}
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void RefBase::onFirstRef()
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{
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}
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void RefBase::onLastStrongRef(const void* /*id*/)
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{
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}
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bool RefBase::onIncStrongAttempted(uint32_t flags, const void* id)
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{
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return (flags&FIRST_INC_STRONG) ? true : false;
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}
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void RefBase::onLastWeakRef(const void* /*id*/)
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{
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}
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}; // namespace android
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