/*
* 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"
#include <utils/RefBase.h>
#include <utils/Atomic.h>
#include <utils/CallStack.h>
#include <utils/KeyedVector.h>
#include <utils/Log.h>
#include <utils/threads.h>
#include <stdlib.h>
#include <stdio.h>
#include <typeinfo>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
// compile with refcounting debugging enabled
#define DEBUG_REFS 0
#define DEBUG_REFS_ENABLED_BY_DEFAULT 1
#define DEBUG_REFS_CALLSTACK_ENABLED 1
// log all reference counting operations
#define PRINT_REFS 0
// ---------------------------------------------------------------------------
namespace android {
#define INITIAL_STRONG_VALUE (1<<28)
// ---------------------------------------------------------------------------
class RefBase::weakref_impl : public RefBase::weakref_type
{
public:
volatile int32_t mStrong;
volatile int32_t mWeak;
RefBase* const mBase;
volatile int32_t mFlags;
#if !DEBUG_REFS
weakref_impl(RefBase* base)
: mStrong(INITIAL_STRONG_VALUE)
, mWeak(0)
, mBase(base)
, mFlags(0)
{
}
void addStrongRef(const void* /*id*/) { }
void removeStrongRef(const void* /*id*/) { }
void addWeakRef(const void* /*id*/) { }
void removeWeakRef(const void* /*id*/) { }
void printRefs() const { }
void trackMe(bool, bool) { }
#else
weakref_impl(RefBase* base)
: mStrong(INITIAL_STRONG_VALUE)
, mWeak(0)
, mBase(base)
, mFlags(0)
, mStrongRefs(NULL)
, mWeakRefs(NULL)
, mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
, mRetain(false)
{
//LOGI("NEW weakref_impl %p for RefBase %p", this, base);
}
~weakref_impl()
{
LOG_ALWAYS_FATAL_IF(!mRetain && mStrongRefs != NULL, "Strong references remain!");
LOG_ALWAYS_FATAL_IF(!mRetain && mWeakRefs != NULL, "Weak references remain!");
}
void addStrongRef(const void* id)
{
addRef(&mStrongRefs, id, mStrong);
}
void removeStrongRef(const void* id)
{
if (!mRetain)
removeRef(&mStrongRefs, id);
else
addRef(&mStrongRefs, id, -mStrong);
}
void addWeakRef(const void* id)
{
addRef(&mWeakRefs, id, mWeak);
}
void removeWeakRef(const void* id)
{
if (!mRetain)
removeRef(&mWeakRefs, id);
else
addRef(&mWeakRefs, id, -mWeak);
}
void trackMe(bool track, bool retain)
{
mTrackEnabled = track;
mRetain = retain;
}
void printRefs() const
{
String8 text;
{
AutoMutex _l(const_cast<weakref_impl*>(this)->mMutex);
char buf[128];
sprintf(buf, "Strong references on RefBase %p (weakref_type %p):\n", mBase, this);
text.append(buf);
printRefsLocked(&text, mStrongRefs);
sprintf(buf, "Weak references on RefBase %p (weakref_type %p):\n", mBase, this);
text.append(buf);
printRefsLocked(&text, mWeakRefs);
}
{
char name[100];
snprintf(name, 100, "/data/%p.stack", this);
int rc = open(name, O_RDWR | O_CREAT | O_APPEND);
if (rc >= 0) {
write(rc, text.string(), text.length());
close(rc);
LOGD("STACK TRACE for %p saved in %s", this, name);
}
else LOGE("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 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
ref->stack.update(2);
#endif
ref->next = *refs;
*refs = ref;
}
}
void removeRef(ref_entry** refs, const void* id)
{
if (mTrackEnabled) {
AutoMutex _l(mMutex);
ref_entry* ref = *refs;
while (ref != NULL) {
if (ref->id == id) {
*refs = ref->next;
delete ref;
return;
}
refs = &ref->next;
ref = *refs;
}
LOG_ALWAYS_FATAL("RefBase: removing id %p on RefBase %p (weakref_type %p) that doesn't exist!",
id, mBase, this);
}
}
void printRefsLocked(String8* out, const ref_entry* refs) const
{
char buf[128];
while (refs) {
char inc = refs->ref >= 0 ? '+' : '-';
sprintf(buf, "\t%c ID %p (ref %d):\n",
inc, refs->id, refs->ref);
out->append(buf);
#if DEBUG_REFS_CALLSTACK_ENABLED
out->append(refs->stack.toString("\t\t"));
#else
out->append("\t\t(call stacks disabled)");
#endif
refs = refs->next;
}
}
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;
#if 0
void addRef(KeyedVector<const void*, int32_t>* refs, const void* id)
{
AutoMutex _l(mMutex);
ssize_t i = refs->indexOfKey(id);
if (i >= 0) {
++(refs->editValueAt(i));
} else {
i = refs->add(id, 1);
}
}
void removeRef(KeyedVector<const void*, int32_t>* refs, const void* id)
{
AutoMutex _l(mMutex);
ssize_t i = refs->indexOfKey(id);
LOG_ALWAYS_FATAL_IF(i < 0, "RefBase: removing id %p that doesn't exist!", id);
if (i >= 0) {
int32_t val = --(refs->editValueAt(i));
if (val == 0) {
refs->removeItemsAt(i);
}
}
}
void printRefs(const KeyedVector<const void*, int32_t>& refs)
{
const size_t N=refs.size();
for (size_t i=0; i<N; i++) {
printf("\tID %p: %d remain\n", refs.keyAt(i), refs.valueAt(i));
}
}
mutable Mutex mMutex;
KeyedVector<const void*, int32_t> mStrongRefs;
KeyedVector<const void*, int32_t> mWeakRefs;
#endif
#endif
};
// ---------------------------------------------------------------------------
void RefBase::incStrong(const void* id) const
{
weakref_impl* const refs = mRefs;
refs->addWeakRef(id);
refs->incWeak(id);
refs->addStrongRef(id);
const int32_t c = android_atomic_inc(&refs->mStrong);
LOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
#if PRINT_REFS
LOGD("incStrong of %p from %p: cnt=%d\n", this, id, c);
#endif
if (c != INITIAL_STRONG_VALUE) {
return;
}
android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
const_cast<RefBase*>(this)->onFirstRef();
}
void RefBase::decStrong(const void* id) const
{
weakref_impl* const refs = mRefs;
refs->removeStrongRef(id);
const int32_t c = android_atomic_dec(&refs->mStrong);
#if PRINT_REFS
LOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
#endif
LOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
if (c == 1) {
const_cast<RefBase*>(this)->onLastStrongRef(id);
if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
delete this;
}
}
refs->removeWeakRef(id);
refs->decWeak(id);
}
void RefBase::forceIncStrong(const void* id) const
{
weakref_impl* const refs = mRefs;
refs->addWeakRef(id);
refs->incWeak(id);
refs->addStrongRef(id);
const int32_t c = android_atomic_inc(&refs->mStrong);
LOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
refs);
#if PRINT_REFS
LOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
#endif
switch (c) {
case INITIAL_STRONG_VALUE:
android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
// fall through...
case 0:
const_cast<RefBase*>(this)->onFirstRef();
}
}
int32_t RefBase::getStrongCount() const
{
return mRefs->mStrong;
}
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 = android_atomic_inc(&impl->mWeak);
LOG_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 = android_atomic_dec(&impl->mWeak);
LOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
if (c != 1) return;
if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
if (impl->mStrong == INITIAL_STRONG_VALUE)
delete impl->mBase;
else {
// LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
delete impl;
}
} else {
impl->mBase->onLastWeakRef(id);
if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
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;
LOG_ASSERT(curCount >= 0, "attemptIncStrong called on %p after underflow",
this);
while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
break;
}
curCount = impl->mStrong;
}
if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
bool allow;
if (curCount == INITIAL_STRONG_VALUE) {
// Attempting to acquire first strong reference... this is allowed
// if the object does NOT have a longer lifetime (meaning the
// implementation doesn't need to see this), or if the implementation
// allows it to happen.
allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK
|| impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
} else {
// Attempting to revive the object... this is allowed
// if the object DOES have a longer lifetime (so we can safely
// call the object with only a weak ref) and the implementation
// allows it to happen.
allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_WEAK
&& impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
}
if (!allow) {
decWeak(id);
return false;
}
curCount = android_atomic_inc(&impl->mStrong);
// 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->addWeakRef(id);
impl->addStrongRef(id);
#if PRINT_REFS
LOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
#endif
if (curCount == INITIAL_STRONG_VALUE) {
android_atomic_add(-INITIAL_STRONG_VALUE, &impl->mStrong);
impl->mBase->onFirstRef();
}
return true;
}
bool RefBase::weakref_type::attemptIncWeak(const void* id)
{
weakref_impl* const impl = static_cast<weakref_impl*>(this);
int32_t curCount = impl->mWeak;
LOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
this);
while (curCount > 0) {
if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mWeak) == 0) {
break;
}
curCount = impl->mWeak;
}
if (curCount > 0) {
impl->addWeakRef(id);
}
return curCount > 0;
}
int32_t RefBase::weakref_type::getWeakCount() const
{
return static_cast<const weakref_impl*>(this)->mWeak;
}
void RefBase::weakref_type::printRefs() const
{
static_cast<const weakref_impl*>(this)->printRefs();
}
void RefBase::weakref_type::trackMe(bool enable, bool retain)
{
static_cast<const 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))
{
// LOGV("Creating refs %p with RefBase %p\n", mRefs, this);
}
RefBase::~RefBase()
{
// LOGV("Destroying RefBase %p (refs %p)\n", this, mRefs);
if (mRefs->mWeak == 0) {
// LOGV("Freeing refs %p of old RefBase %p\n", mRefs, this);
delete mRefs;
}
}
void RefBase::extendObjectLifetime(int32_t mode)
{
android_atomic_or(mode, &mRefs->mFlags);
}
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*/)
{
}
}; // namespace android