e1731a4f2e
Fixes -Wzero-as-null-pointer-constant warning. Test: m Bug: 68236239 Change-Id: I5e89ec8c42151875439d2656475a8739ab9cb7dc
767 lines
26 KiB
C++
767 lines
26 KiB
C++
/*
|
|
* Copyright (C) 2005 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
#define LOG_TAG "RefBase"
|
|
// #define LOG_NDEBUG 0
|
|
|
|
#include <utils/RefBase.h>
|
|
|
|
#include <utils/CallStack.h>
|
|
|
|
#ifndef __unused
|
|
#define __unused __attribute__((__unused__))
|
|
#endif
|
|
|
|
// compile with refcounting debugging enabled
|
|
#define DEBUG_REFS 0
|
|
|
|
// whether ref-tracking is enabled by default, if not, trackMe(true, false)
|
|
// needs to be called explicitly
|
|
#define DEBUG_REFS_ENABLED_BY_DEFAULT 0
|
|
|
|
// whether callstack are collected (significantly slows things down)
|
|
#define DEBUG_REFS_CALLSTACK_ENABLED 1
|
|
|
|
// folder where stack traces are saved when DEBUG_REFS is enabled
|
|
// this folder needs to exist and be writable
|
|
#define DEBUG_REFS_CALLSTACK_PATH "/data/debug"
|
|
|
|
// log all reference counting operations
|
|
#define PRINT_REFS 0
|
|
|
|
// ---------------------------------------------------------------------------
|
|
|
|
namespace android {
|
|
|
|
// Observations, invariants, etc:
|
|
|
|
// By default, obects are destroyed when the last strong reference disappears
|
|
// or, if the object never had a strong reference, when the last weak reference
|
|
// disappears.
|
|
//
|
|
// OBJECT_LIFETIME_WEAK changes this behavior to retain the object
|
|
// unconditionally until the last reference of either kind disappears. The
|
|
// client ensures that the extendObjectLifetime call happens before the dec
|
|
// call that would otherwise have deallocated the object, or before an
|
|
// attemptIncStrong call that might rely on it. We do not worry about
|
|
// concurrent changes to the object lifetime.
|
|
//
|
|
// AttemptIncStrong will succeed if the object has a strong reference, or if it
|
|
// has a weak reference and has never had a strong reference.
|
|
// AttemptIncWeak really does succeed only if there is already a WEAK
|
|
// reference, and thus may fail when attemptIncStrong would succeed.
|
|
//
|
|
// mStrong is the strong reference count. mWeak is the weak reference count.
|
|
// Between calls, and ignoring memory ordering effects, mWeak includes strong
|
|
// references, and is thus >= mStrong.
|
|
//
|
|
// A weakref_impl holds all the information, including both reference counts,
|
|
// required to perform wp<> operations. Thus these can continue to be performed
|
|
// after the RefBase object has been destroyed.
|
|
//
|
|
// A weakref_impl is allocated as the value of mRefs in a RefBase object on
|
|
// construction.
|
|
// In the OBJECT_LIFETIME_STRONG case, it is normally deallocated in decWeak,
|
|
// and hence lives as long as the last weak reference. (It can also be
|
|
// deallocated in the RefBase destructor iff the strong reference count was
|
|
// never incremented and the weak count is zero, e.g. if the RefBase object is
|
|
// explicitly destroyed without decrementing the strong count. This should be
|
|
// avoided.) In this case, the RefBase destructor should be invoked from
|
|
// decStrong.
|
|
// In the OBJECT_LIFETIME_WEAK case, the weakref_impl is always deallocated in
|
|
// the RefBase destructor, which is always invoked by decWeak. DecStrong
|
|
// explicitly avoids the deletion in this case.
|
|
//
|
|
// Memory ordering:
|
|
// The client must ensure that every inc() call, together with all other
|
|
// accesses to the object, happens before the corresponding dec() call.
|
|
//
|
|
// We try to keep memory ordering constraints on atomics as weak as possible,
|
|
// since memory fences or ordered memory accesses are likely to be a major
|
|
// performance cost for this code. All accesses to mStrong, mWeak, and mFlags
|
|
// explicitly relax memory ordering in some way.
|
|
//
|
|
// The only operations that are not memory_order_relaxed are reference count
|
|
// decrements. All reference count decrements are release operations. In
|
|
// addition, the final decrement leading the deallocation is followed by an
|
|
// acquire fence, which we can view informally as also turning it into an
|
|
// acquire operation. (See 29.8p4 [atomics.fences] for details. We could
|
|
// alternatively use acq_rel operations for all decrements. This is probably
|
|
// slower on most current (2016) hardware, especially on ARMv7, but that may
|
|
// not be true indefinitely.)
|
|
//
|
|
// This convention ensures that the second-to-last decrement synchronizes with
|
|
// (in the language of 1.10 in the C++ standard) the final decrement of a
|
|
// reference count. Since reference counts are only updated using atomic
|
|
// read-modify-write operations, this also extends to any earlier decrements.
|
|
// (See "release sequence" in 1.10.)
|
|
//
|
|
// Since all operations on an object happen before the corresponding reference
|
|
// count decrement, and all reference count decrements happen before the final
|
|
// one, we are guaranteed that all other object accesses happen before the
|
|
// object is destroyed.
|
|
|
|
|
|
#define INITIAL_STRONG_VALUE (1<<28)
|
|
|
|
#define MAX_COUNT 0xfffff
|
|
|
|
// Test whether the argument is a clearly invalid strong reference count.
|
|
// Used only for error checking on the value before an atomic decrement.
|
|
// Intended to be very cheap.
|
|
// Note that we cannot just check for excess decrements by comparing to zero
|
|
// since the object would be deallocated before that.
|
|
#define BAD_STRONG(c) \
|
|
((c) == 0 || ((c) & (~(MAX_COUNT | INITIAL_STRONG_VALUE))) != 0)
|
|
|
|
// Same for weak counts.
|
|
#define BAD_WEAK(c) ((c) == 0 || ((c) & (~MAX_COUNT)) != 0)
|
|
|
|
// ---------------------------------------------------------------------------
|
|
|
|
class RefBase::weakref_impl : public RefBase::weakref_type
|
|
{
|
|
public:
|
|
std::atomic<int32_t> mStrong;
|
|
std::atomic<int32_t> mWeak;
|
|
RefBase* const mBase;
|
|
std::atomic<int32_t> mFlags;
|
|
|
|
#if !DEBUG_REFS
|
|
|
|
explicit weakref_impl(RefBase* base)
|
|
: mStrong(INITIAL_STRONG_VALUE)
|
|
, mWeak(0)
|
|
, mBase(base)
|
|
, mFlags(0)
|
|
{
|
|
}
|
|
|
|
void addStrongRef(const void* /*id*/) { }
|
|
void removeStrongRef(const void* /*id*/) { }
|
|
void renameStrongRefId(const void* /*old_id*/, const void* /*new_id*/) { }
|
|
void addWeakRef(const void* /*id*/) { }
|
|
void removeWeakRef(const void* /*id*/) { }
|
|
void renameWeakRefId(const void* /*old_id*/, const void* /*new_id*/) { }
|
|
void printRefs() const { }
|
|
void trackMe(bool, bool) { }
|
|
|
|
#else
|
|
|
|
weakref_impl(RefBase* base)
|
|
: mStrong(INITIAL_STRONG_VALUE)
|
|
, mWeak(0)
|
|
, mBase(base)
|
|
, mFlags(0)
|
|
, mStrongRefs(NULL)
|
|
, mWeakRefs(NULL)
|
|
, mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
|
|
, mRetain(false)
|
|
{
|
|
}
|
|
|
|
~weakref_impl()
|
|
{
|
|
bool dumpStack = false;
|
|
if (!mRetain && mStrongRefs != NULL) {
|
|
dumpStack = true;
|
|
ALOGE("Strong references remain:");
|
|
ref_entry* refs = mStrongRefs;
|
|
while (refs) {
|
|
char inc = refs->ref >= 0 ? '+' : '-';
|
|
ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
|
|
#if DEBUG_REFS_CALLSTACK_ENABLED
|
|
refs->stack.log(LOG_TAG);
|
|
#endif
|
|
refs = refs->next;
|
|
}
|
|
}
|
|
|
|
if (!mRetain && mWeakRefs != NULL) {
|
|
dumpStack = true;
|
|
ALOGE("Weak references remain!");
|
|
ref_entry* refs = mWeakRefs;
|
|
while (refs) {
|
|
char inc = refs->ref >= 0 ? '+' : '-';
|
|
ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
|
|
#if DEBUG_REFS_CALLSTACK_ENABLED
|
|
refs->stack.log(LOG_TAG);
|
|
#endif
|
|
refs = refs->next;
|
|
}
|
|
}
|
|
if (dumpStack) {
|
|
ALOGE("above errors at:");
|
|
CallStack stack(LOG_TAG);
|
|
}
|
|
}
|
|
|
|
void addStrongRef(const void* id) {
|
|
//ALOGD_IF(mTrackEnabled,
|
|
// "addStrongRef: RefBase=%p, id=%p", mBase, id);
|
|
addRef(&mStrongRefs, id, mStrong.load(std::memory_order_relaxed));
|
|
}
|
|
|
|
void removeStrongRef(const void* id) {
|
|
//ALOGD_IF(mTrackEnabled,
|
|
// "removeStrongRef: RefBase=%p, id=%p", mBase, id);
|
|
if (!mRetain) {
|
|
removeRef(&mStrongRefs, id);
|
|
} else {
|
|
addRef(&mStrongRefs, id, -mStrong.load(std::memory_order_relaxed));
|
|
}
|
|
}
|
|
|
|
void renameStrongRefId(const void* old_id, const void* new_id) {
|
|
//ALOGD_IF(mTrackEnabled,
|
|
// "renameStrongRefId: RefBase=%p, oid=%p, nid=%p",
|
|
// mBase, old_id, new_id);
|
|
renameRefsId(mStrongRefs, old_id, new_id);
|
|
}
|
|
|
|
void addWeakRef(const void* id) {
|
|
addRef(&mWeakRefs, id, mWeak.load(std::memory_order_relaxed));
|
|
}
|
|
|
|
void removeWeakRef(const void* id) {
|
|
if (!mRetain) {
|
|
removeRef(&mWeakRefs, id);
|
|
} else {
|
|
addRef(&mWeakRefs, id, -mWeak.load(std::memory_order_relaxed));
|
|
}
|
|
}
|
|
|
|
void renameWeakRefId(const void* old_id, const void* new_id) {
|
|
renameRefsId(mWeakRefs, old_id, new_id);
|
|
}
|
|
|
|
void trackMe(bool track, bool retain)
|
|
{
|
|
mTrackEnabled = track;
|
|
mRetain = retain;
|
|
}
|
|
|
|
void printRefs() const
|
|
{
|
|
String8 text;
|
|
|
|
{
|
|
Mutex::Autolock _l(mMutex);
|
|
char buf[128];
|
|
snprintf(buf, sizeof(buf),
|
|
"Strong references on RefBase %p (weakref_type %p):\n",
|
|
mBase, this);
|
|
text.append(buf);
|
|
printRefsLocked(&text, mStrongRefs);
|
|
snprintf(buf, sizeof(buf),
|
|
"Weak references on RefBase %p (weakref_type %p):\n",
|
|
mBase, this);
|
|
text.append(buf);
|
|
printRefsLocked(&text, mWeakRefs);
|
|
}
|
|
|
|
{
|
|
char name[100];
|
|
snprintf(name, sizeof(name), DEBUG_REFS_CALLSTACK_PATH "/%p.stack",
|
|
this);
|
|
int rc = open(name, O_RDWR | O_CREAT | O_APPEND, 644);
|
|
if (rc >= 0) {
|
|
write(rc, text.string(), text.length());
|
|
close(rc);
|
|
ALOGD("STACK TRACE for %p saved in %s", this, name);
|
|
}
|
|
else ALOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this,
|
|
name, strerror(errno));
|
|
}
|
|
}
|
|
|
|
private:
|
|
struct ref_entry
|
|
{
|
|
ref_entry* next;
|
|
const void* id;
|
|
#if DEBUG_REFS_CALLSTACK_ENABLED
|
|
CallStack 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* const head = *refs;
|
|
ref_entry* ref = head;
|
|
while (ref != NULL) {
|
|
if (ref->id == id) {
|
|
*refs = ref->next;
|
|
delete ref;
|
|
return;
|
|
}
|
|
refs = &ref->next;
|
|
ref = *refs;
|
|
}
|
|
|
|
ALOGE("RefBase: removing id %p on RefBase %p"
|
|
"(weakref_type %p) that doesn't exist!",
|
|
id, mBase, this);
|
|
|
|
ref = head;
|
|
while (ref) {
|
|
char inc = ref->ref >= 0 ? '+' : '-';
|
|
ALOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref);
|
|
ref = ref->next;
|
|
}
|
|
|
|
CallStack stack(LOG_TAG);
|
|
}
|
|
}
|
|
|
|
void renameRefsId(ref_entry* r, const void* old_id, const void* new_id)
|
|
{
|
|
if (mTrackEnabled) {
|
|
AutoMutex _l(mMutex);
|
|
ref_entry* ref = r;
|
|
while (ref != NULL) {
|
|
if (ref->id == old_id) {
|
|
ref->id = new_id;
|
|
}
|
|
ref = ref->next;
|
|
}
|
|
}
|
|
}
|
|
|
|
void printRefsLocked(String8* out, const ref_entry* refs) const
|
|
{
|
|
char buf[128];
|
|
while (refs) {
|
|
char inc = refs->ref >= 0 ? '+' : '-';
|
|
snprintf(buf, sizeof(buf), "\t%c ID %p (ref %d):\n",
|
|
inc, refs->id, refs->ref);
|
|
out->append(buf);
|
|
#if DEBUG_REFS_CALLSTACK_ENABLED
|
|
out->append(refs->stack.toString("\t\t"));
|
|
#else
|
|
out->append("\t\t(call stacks disabled)");
|
|
#endif
|
|
refs = refs->next;
|
|
}
|
|
}
|
|
|
|
mutable Mutex mMutex;
|
|
ref_entry* mStrongRefs;
|
|
ref_entry* mWeakRefs;
|
|
|
|
bool mTrackEnabled;
|
|
// Collect stack traces on addref and removeref, instead of deleting the stack references
|
|
// on removeref that match the address ones.
|
|
bool mRetain;
|
|
|
|
#endif
|
|
};
|
|
|
|
// ---------------------------------------------------------------------------
|
|
|
|
void RefBase::incStrong(const void* id) const
|
|
{
|
|
weakref_impl* const refs = mRefs;
|
|
refs->incWeak(id);
|
|
|
|
refs->addStrongRef(id);
|
|
const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed);
|
|
ALOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
|
|
#if PRINT_REFS
|
|
ALOGD("incStrong of %p from %p: cnt=%d\n", this, id, c);
|
|
#endif
|
|
if (c != INITIAL_STRONG_VALUE) {
|
|
return;
|
|
}
|
|
|
|
int32_t old __unused = refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE, std::memory_order_relaxed);
|
|
// A decStrong() must still happen after us.
|
|
ALOG_ASSERT(old > INITIAL_STRONG_VALUE, "0x%x too small", old);
|
|
refs->mBase->onFirstRef();
|
|
}
|
|
|
|
void RefBase::decStrong(const void* id) const
|
|
{
|
|
weakref_impl* const refs = mRefs;
|
|
refs->removeStrongRef(id);
|
|
const int32_t c = refs->mStrong.fetch_sub(1, std::memory_order_release);
|
|
#if PRINT_REFS
|
|
ALOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
|
|
#endif
|
|
LOG_ALWAYS_FATAL_IF(BAD_STRONG(c), "decStrong() called on %p too many times",
|
|
refs);
|
|
if (c == 1) {
|
|
std::atomic_thread_fence(std::memory_order_acquire);
|
|
refs->mBase->onLastStrongRef(id);
|
|
int32_t flags = refs->mFlags.load(std::memory_order_relaxed);
|
|
if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
|
|
delete this;
|
|
// The destructor does not delete refs in this case.
|
|
}
|
|
}
|
|
// Note that even with only strong reference operations, the thread
|
|
// deallocating this may not be the same as the thread deallocating refs.
|
|
// That's OK: all accesses to this happen before its deletion here,
|
|
// and all accesses to refs happen before its deletion in the final decWeak.
|
|
// The destructor can safely access mRefs because either it's deleting
|
|
// mRefs itself, or it's running entirely before the final mWeak decrement.
|
|
//
|
|
// Since we're doing atomic loads of `flags`, the static analyzer assumes
|
|
// they can change between `delete this;` and `refs->decWeak(id);`. This is
|
|
// not the case. The analyzer may become more okay with this patten when
|
|
// https://bugs.llvm.org/show_bug.cgi?id=34365 gets resolved. NOLINTNEXTLINE
|
|
refs->decWeak(id);
|
|
}
|
|
|
|
void RefBase::forceIncStrong(const void* id) const
|
|
{
|
|
// Allows initial mStrong of 0 in addition to INITIAL_STRONG_VALUE.
|
|
// TODO: Better document assumptions.
|
|
weakref_impl* const refs = mRefs;
|
|
refs->incWeak(id);
|
|
|
|
refs->addStrongRef(id);
|
|
const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed);
|
|
ALOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
|
|
refs);
|
|
#if PRINT_REFS
|
|
ALOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
|
|
#endif
|
|
|
|
switch (c) {
|
|
case INITIAL_STRONG_VALUE:
|
|
refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE,
|
|
std::memory_order_relaxed);
|
|
// fall through...
|
|
case 0:
|
|
refs->mBase->onFirstRef();
|
|
}
|
|
}
|
|
|
|
int32_t RefBase::getStrongCount() const
|
|
{
|
|
// Debugging only; No memory ordering guarantees.
|
|
return mRefs->mStrong.load(std::memory_order_relaxed);
|
|
}
|
|
|
|
RefBase* RefBase::weakref_type::refBase() const
|
|
{
|
|
return static_cast<const weakref_impl*>(this)->mBase;
|
|
}
|
|
|
|
void RefBase::weakref_type::incWeak(const void* id)
|
|
{
|
|
weakref_impl* const impl = static_cast<weakref_impl*>(this);
|
|
impl->addWeakRef(id);
|
|
const int32_t c __unused = impl->mWeak.fetch_add(1,
|
|
std::memory_order_relaxed);
|
|
ALOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
|
|
}
|
|
|
|
|
|
void RefBase::weakref_type::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.
|
|
LOG_ALWAYS_FATAL_IF(mRefs->mWeak.load() != 0,
|
|
"RefBase: Explicit destruction with non-zero weak "
|
|
"reference count");
|
|
// TODO: Always report if we get here. Currently MediaMetadataRetriever
|
|
// C++ objects are inconsistently managed and sometimes get here.
|
|
// There may be other cases, but we believe they should all be fixed.
|
|
delete mRefs;
|
|
}
|
|
// 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
|