libutils: split out libutils_binder
Dependencies of libbinder, so we can build
a core libbinder library, libbinder_sdk.
This is preparing the way to move this part of libbinder
together with binder code into a single project.
Bug: 302720583
Change-Id: Icff078ac6e36c7f2b91cf815d5b9ed19b2e706e1
diff --git a/libutils/binder/RefBase.cpp b/libutils/binder/RefBase.cpp
new file mode 100644
index 0000000..c7055fb
--- /dev/null
+++ b/libutils/binder/RefBase.cpp
@@ -0,0 +1,856 @@
+/*
+ * Copyright (C) 2005 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "RefBase"
+// #define LOG_NDEBUG 0
+
+#include <memory>
+#include <mutex>
+
+#include <android-base/macros.h>
+
+#include <fcntl.h>
+#include <log/log.h>
+
+#include <utils/RefBase.h>
+#include <utils/String8.h>
+
+#ifndef __unused
+#define __unused __attribute__((__unused__))
+#endif
+
+// Compile with refcounting debugging enabled.
+#ifndef DEBUG_REFS
+#define DEBUG_REFS 0
+#endif
+
+// The following three are ignored unless DEBUG_REFS is set.
+
+// whether ref-tracking is enabled by default, if not, trackMe(true, false)
+// needs to be called explicitly
+#define DEBUG_REFS_ENABLED_BY_DEFAULT 0
+
+// whether callstack are collected (significantly slows things down)
+#define DEBUG_REFS_CALLSTACK_ENABLED 1
+
+// folder where stack traces are saved when DEBUG_REFS is enabled
+// this folder needs to exist and be writable
+#ifdef __ANDROID__
+#define DEBUG_REFS_CALLSTACK_PATH "/data/debug"
+#else
+#define DEBUG_REFS_CALLSTACK_PATH "."
+#endif
+
+// log all reference counting operations
+#define PRINT_REFS 0
+
+#if defined(__linux__)
+// CallStack is only supported on linux type platforms.
+#define CALLSTACK_ENABLED 1
+#else
+#define CALLSTACK_ENABLED 0
+#endif
+
+#if CALLSTACK_ENABLED
+#include <utils/CallStack.h>
+#endif
+
+// ---------------------------------------------------------------------------
+
+namespace android {
+
+// Observations, invariants, etc:
+
+// By default, obects are destroyed when the last strong reference disappears
+// or, if the object never had a strong reference, when the last weak reference
+// disappears.
+//
+// OBJECT_LIFETIME_WEAK changes this behavior to retain the object
+// unconditionally until the last reference of either kind disappears. The
+// client ensures that the extendObjectLifetime call happens before the dec
+// call that would otherwise have deallocated the object, or before an
+// attemptIncStrong call that might rely on it. We do not worry about
+// concurrent changes to the object lifetime.
+//
+// AttemptIncStrong will succeed if the object has a strong reference, or if it
+// has a weak reference and has never had a strong reference.
+// AttemptIncWeak really does succeed only if there is already a WEAK
+// reference, and thus may fail when attemptIncStrong would succeed.
+//
+// mStrong is the strong reference count. mWeak is the weak reference count.
+// Between calls, and ignoring memory ordering effects, mWeak includes strong
+// references, and is thus >= mStrong.
+//
+// A weakref_impl holds all the information, including both reference counts,
+// required to perform wp<> operations. Thus these can continue to be performed
+// after the RefBase object has been destroyed.
+//
+// A weakref_impl is allocated as the value of mRefs in a RefBase object on
+// construction.
+// In the OBJECT_LIFETIME_STRONG case, it is normally deallocated in decWeak,
+// and hence lives as long as the last weak reference. (It can also be
+// deallocated in the RefBase destructor iff the strong reference count was
+// never incremented and the weak count is zero, e.g. if the RefBase object is
+// explicitly destroyed without decrementing the strong count. This should be
+// avoided.) In this case, the RefBase destructor should be invoked from
+// decStrong.
+// In the OBJECT_LIFETIME_WEAK case, the weakref_impl is always deallocated in
+// the RefBase destructor, which is always invoked by decWeak. DecStrong
+// explicitly avoids the deletion in this case.
+//
+// Memory ordering:
+// The client must ensure that every inc() call, together with all other
+// accesses to the object, happens before the corresponding dec() call.
+//
+// We try to keep memory ordering constraints on atomics as weak as possible,
+// since memory fences or ordered memory accesses are likely to be a major
+// performance cost for this code. All accesses to mStrong, mWeak, and mFlags
+// explicitly relax memory ordering in some way.
+//
+// The only operations that are not memory_order_relaxed are reference count
+// decrements. All reference count decrements are release operations. In
+// addition, the final decrement leading the deallocation is followed by an
+// acquire fence, which we can view informally as also turning it into an
+// acquire operation. (See 29.8p4 [atomics.fences] for details. We could
+// alternatively use acq_rel operations for all decrements. This is probably
+// slower on most current (2016) hardware, especially on ARMv7, but that may
+// not be true indefinitely.)
+//
+// This convention ensures that the second-to-last decrement synchronizes with
+// (in the language of 1.10 in the C++ standard) the final decrement of a
+// reference count. Since reference counts are only updated using atomic
+// read-modify-write operations, this also extends to any earlier decrements.
+// (See "release sequence" in 1.10.)
+//
+// Since all operations on an object happen before the corresponding reference
+// count decrement, and all reference count decrements happen before the final
+// one, we are guaranteed that all other object accesses happen before the
+// object is destroyed.
+
+
+#define INITIAL_STRONG_VALUE (1<<28)
+
+#define MAX_COUNT 0xfffff
+
+// Test whether the argument is a clearly invalid strong reference count.
+// Used only for error checking on the value before an atomic decrement.
+// Intended to be very cheap.
+// Note that we cannot just check for excess decrements by comparing to zero
+// since the object would be deallocated before that.
+#define BAD_STRONG(c) \
+ ((c) == 0 || ((c) & (~(MAX_COUNT | INITIAL_STRONG_VALUE))) != 0)
+
+// Same for weak counts.
+#define BAD_WEAK(c) ((c) == 0 || ((c) & (~MAX_COUNT)) != 0)
+
+// name kept because prebuilts used to use it from inlining sp<> code
+void sp_report_stack_pointer() { LOG_ALWAYS_FATAL("RefBase used with stack pointer argument"); }
+
+// Check whether address is definitely on the calling stack. We actually check whether it is on
+// the same 4K page as the frame pointer.
+//
+// Assumptions:
+// - Pages are never smaller than 4K (MIN_PAGE_SIZE)
+// - Malloced memory never shares a page with a stack.
+//
+// It does not appear safe to broaden this check to include adjacent pages; apparently this code
+// is used in environments where there may not be a guard page below (at higher addresses than)
+// the bottom of the stack.
+static void check_not_on_stack(const void* ptr) {
+ static constexpr int MIN_PAGE_SIZE = 0x1000; // 4K. Safer than including sys/user.h.
+ static constexpr uintptr_t MIN_PAGE_MASK = ~static_cast<uintptr_t>(MIN_PAGE_SIZE - 1);
+ uintptr_t my_frame_address =
+ reinterpret_cast<uintptr_t>(__builtin_frame_address(0 /* this frame */));
+ if (((reinterpret_cast<uintptr_t>(ptr) ^ my_frame_address) & MIN_PAGE_MASK) == 0) {
+ sp_report_stack_pointer();
+ }
+}
+
+// ---------------------------------------------------------------------------
+
+class RefBase::weakref_impl : public RefBase::weakref_type
+{
+public:
+ std::atomic<int32_t> mStrong;
+ std::atomic<int32_t> mWeak;
+ RefBase* const mBase;
+ std::atomic<int32_t> mFlags;
+
+#if !DEBUG_REFS
+
+ explicit weakref_impl(RefBase* base)
+ : mStrong(INITIAL_STRONG_VALUE)
+ , mWeak(0)
+ , mBase(base)
+ , mFlags(OBJECT_LIFETIME_STRONG)
+ {
+ }
+
+ void addStrongRef(const void* /*id*/) { }
+ void removeStrongRef(const void* /*id*/) { }
+ void renameStrongRefId(const void* /*old_id*/, const void* /*new_id*/) { }
+ void addWeakRef(const void* /*id*/) { }
+ void removeWeakRef(const void* /*id*/) { }
+ void renameWeakRefId(const void* /*old_id*/, const void* /*new_id*/) { }
+ void printRefs() const { }
+ void trackMe(bool, bool) { }
+
+#else
+
+ weakref_impl(RefBase* base)
+ : mStrong(INITIAL_STRONG_VALUE)
+ , mWeak(0)
+ , mBase(base)
+ , mFlags(OBJECT_LIFETIME_STRONG)
+ , mStrongRefs(NULL)
+ , mWeakRefs(NULL)
+ , mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
+ , mRetain(false)
+ {
+ }
+
+ ~weakref_impl()
+ {
+ bool dumpStack = false;
+ if (!mRetain && mStrongRefs != NULL) {
+ dumpStack = true;
+ ALOGE("Strong references remain:");
+ ref_entry* refs = mStrongRefs;
+ while (refs) {
+ char inc = refs->ref >= 0 ? '+' : '-';
+ ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
+#if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED
+ CallStack::logStack(LOG_TAG, refs->stack.get());
+#endif
+ refs = refs->next;
+ }
+ }
+
+ if (!mRetain && mWeakRefs != NULL) {
+ dumpStack = true;
+ ALOGE("Weak references remain!");
+ ref_entry* refs = mWeakRefs;
+ while (refs) {
+ char inc = refs->ref >= 0 ? '+' : '-';
+ ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
+#if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED
+ CallStack::logStack(LOG_TAG, refs->stack.get());
+#endif
+ refs = refs->next;
+ }
+ }
+ if (dumpStack) {
+ ALOGE("above errors at:");
+#if CALLSTACK_ENABLED
+ CallStack::logStack(LOG_TAG);
+#endif
+ }
+ }
+
+ void addStrongRef(const void* id) {
+ //ALOGD_IF(mTrackEnabled,
+ // "addStrongRef: RefBase=%p, id=%p", mBase, id);
+ addRef(&mStrongRefs, id, mStrong.load(std::memory_order_relaxed));
+ }
+
+ void removeStrongRef(const void* id) {
+ //ALOGD_IF(mTrackEnabled,
+ // "removeStrongRef: RefBase=%p, id=%p", mBase, id);
+ if (!mRetain) {
+ removeRef(&mStrongRefs, id);
+ } else {
+ addRef(&mStrongRefs, id, -mStrong.load(std::memory_order_relaxed));
+ }
+ }
+
+ void renameStrongRefId(const void* old_id, const void* new_id) {
+ //ALOGD_IF(mTrackEnabled,
+ // "renameStrongRefId: RefBase=%p, oid=%p, nid=%p",
+ // mBase, old_id, new_id);
+ renameRefsId(mStrongRefs, old_id, new_id);
+ }
+
+ void addWeakRef(const void* id) {
+ addRef(&mWeakRefs, id, mWeak.load(std::memory_order_relaxed));
+ }
+
+ void removeWeakRef(const void* id) {
+ if (!mRetain) {
+ removeRef(&mWeakRefs, id);
+ } else {
+ addRef(&mWeakRefs, id, -mWeak.load(std::memory_order_relaxed));
+ }
+ }
+
+ void renameWeakRefId(const void* old_id, const void* new_id) {
+ renameRefsId(mWeakRefs, old_id, new_id);
+ }
+
+ void trackMe(bool track, bool retain) {
+ mTrackEnabled = track;
+ mRetain = retain;
+ }
+
+ void printRefs() const
+ {
+ String8 text;
+
+ {
+ std::lock_guard<std::mutex> _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, 0644);
+ if (rc >= 0) {
+ (void)write(rc, text.c_str(), text.length());
+ close(rc);
+ ALOGI("STACK TRACE for %p saved in %s", this, name);
+ }
+ else ALOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this,
+ name, strerror(errno));
+ }
+ }
+
+private:
+ struct ref_entry
+ {
+ ref_entry* next;
+ const void* id;
+#if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED
+ CallStack::CallStackUPtr stack;
+#endif
+ int32_t ref;
+ };
+
+ void addRef(ref_entry** refs, const void* id, int32_t mRef)
+ {
+ if (mTrackEnabled) {
+ std::lock_guard<std::mutex> _l(mMutex);
+
+ ref_entry* ref = new ref_entry;
+ // Reference count at the time of the snapshot, but before the
+ // update. Positive value means we increment, negative--we
+ // decrement the reference count.
+ ref->ref = mRef;
+ ref->id = id;
+#if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED
+ ref->stack = CallStack::getCurrent(2);
+#endif
+ ref->next = *refs;
+ *refs = ref;
+ }
+ }
+
+ void removeRef(ref_entry** refs, const void* id)
+ {
+ if (mTrackEnabled) {
+ std::lock_guard<std::mutex> _l(mMutex);
+
+ ref_entry* const head = *refs;
+ ref_entry* ref = head;
+ while (ref != NULL) {
+ if (ref->id == id) {
+ *refs = ref->next;
+ delete ref;
+ return;
+ }
+ refs = &ref->next;
+ ref = *refs;
+ }
+
+ ALOGE("RefBase: removing id %p on RefBase %p"
+ "(weakref_type %p) that doesn't exist!",
+ id, mBase, this);
+
+ ref = head;
+ while (ref) {
+ char inc = ref->ref >= 0 ? '+' : '-';
+ ALOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref);
+ ref = ref->next;
+ }
+
+#if CALLSTACK_ENABLED
+ CallStack::logStack(LOG_TAG);
+#endif
+ }
+ }
+
+ void renameRefsId(ref_entry* r, const void* old_id, const void* new_id)
+ {
+ if (mTrackEnabled) {
+ std::lock_guard<std::mutex> _l(mMutex);
+ ref_entry* ref = r;
+ while (ref != NULL) {
+ if (ref->id == old_id) {
+ ref->id = new_id;
+ }
+ ref = ref->next;
+ }
+ }
+ }
+
+ void printRefsLocked(String8* out, const ref_entry* refs) const
+ {
+ char buf[128];
+ while (refs) {
+ char inc = refs->ref >= 0 ? '+' : '-';
+ snprintf(buf, sizeof(buf), "\t%c ID %p (ref %d):\n",
+ inc, refs->id, refs->ref);
+ out->append(buf);
+#if DEBUG_REFS_CALLSTACK_ENABLED && CALLSTACK_ENABLED
+ out->append(CallStack::stackToString("\t\t", refs->stack.get()));
+#else
+ out->append("\t\t(call stacks disabled)");
+#endif
+ refs = refs->next;
+ }
+ }
+
+ mutable std::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;
+ }
+
+ check_not_on_stack(this);
+
+ int32_t old __unused = refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE, std::memory_order_relaxed);
+ // A decStrong() must still happen after us.
+ ALOG_ASSERT(old > INITIAL_STRONG_VALUE, "0x%x too small", old);
+ refs->mBase->onFirstRef();
+}
+
+void RefBase::incStrongRequireStrong(const void* id) const {
+ weakref_impl* const refs = mRefs;
+ refs->incWeak(id);
+
+ refs->addStrongRef(id);
+ const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed);
+
+ LOG_ALWAYS_FATAL_IF(c <= 0 || c == INITIAL_STRONG_VALUE,
+ "incStrongRequireStrong() called on %p which isn't already owned", refs);
+#if PRINT_REFS
+ ALOGD("incStrong (requiring strong) of %p from %p: cnt=%d\n", this, id, c);
+#endif
+}
+
+void RefBase::decStrong(const void* id) const
+{
+ weakref_impl* const refs = mRefs;
+ refs->removeStrongRef(id);
+ const int32_t c = refs->mStrong.fetch_sub(1, std::memory_order_release);
+#if PRINT_REFS
+ ALOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
+#endif
+ LOG_ALWAYS_FATAL_IF(BAD_STRONG(c), "decStrong() called on %p too many times",
+ refs);
+ if (c == 1) {
+ std::atomic_thread_fence(std::memory_order_acquire);
+ refs->mBase->onLastStrongRef(id);
+ int32_t flags = refs->mFlags.load(std::memory_order_relaxed);
+ if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
+ delete this;
+ // The destructor does not delete refs in this case.
+ }
+ }
+ // Note that even with only strong reference operations, the thread
+ // deallocating this may not be the same as the thread deallocating refs.
+ // That's OK: all accesses to this happen before its deletion here,
+ // and all accesses to refs happen before its deletion in the final decWeak.
+ // The destructor can safely access mRefs because either it's deleting
+ // mRefs itself, or it's running entirely before the final mWeak decrement.
+ //
+ // Since we're doing atomic loads of `flags`, the static analyzer assumes
+ // they can change between `delete this;` and `refs->decWeak(id);`. This is
+ // not the case. The analyzer may become more okay with this patten when
+ // https://bugs.llvm.org/show_bug.cgi?id=34365 gets resolved. NOLINTNEXTLINE
+ refs->decWeak(id);
+}
+
+void RefBase::forceIncStrong(const void* id) const
+{
+ // Allows initial mStrong of 0 in addition to INITIAL_STRONG_VALUE.
+ // TODO: Better document assumptions.
+ weakref_impl* const refs = mRefs;
+ refs->incWeak(id);
+
+ refs->addStrongRef(id);
+ const int32_t c = refs->mStrong.fetch_add(1, std::memory_order_relaxed);
+ ALOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
+ refs);
+#if PRINT_REFS
+ ALOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
+#endif
+
+ switch (c) {
+ case INITIAL_STRONG_VALUE:
+ refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE,
+ std::memory_order_relaxed);
+ FALLTHROUGH_INTENDED;
+ case 0:
+ refs->mBase->onFirstRef();
+ }
+}
+
+int32_t RefBase::getStrongCount() const
+{
+ // Debugging only; No memory ordering guarantees.
+ return mRefs->mStrong.load(std::memory_order_relaxed);
+}
+
+RefBase* RefBase::weakref_type::refBase() const
+{
+ return static_cast<const weakref_impl*>(this)->mBase;
+}
+
+void RefBase::weakref_type::incWeak(const void* id)
+{
+ weakref_impl* const impl = static_cast<weakref_impl*>(this);
+ impl->addWeakRef(id);
+ const int32_t c __unused = impl->mWeak.fetch_add(1,
+ std::memory_order_relaxed);
+ ALOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
+}
+
+void RefBase::weakref_type::incWeakRequireWeak(const void* id)
+{
+ weakref_impl* const impl = static_cast<weakref_impl*>(this);
+ impl->addWeakRef(id);
+ const int32_t c __unused = impl->mWeak.fetch_add(1,
+ std::memory_order_relaxed);
+ LOG_ALWAYS_FATAL_IF(c <= 0, "incWeakRequireWeak called on %p which has no weak refs", this);
+}
+
+void RefBase::weakref_type::decWeak(const void* id)
+{
+ weakref_impl* const impl = static_cast<weakref_impl*>(this);
+ impl->removeWeakRef(id);
+ const int32_t c = impl->mWeak.fetch_sub(1, std::memory_order_release);
+ LOG_ALWAYS_FATAL_IF(BAD_WEAK(c), "decWeak called on %p too many times",
+ this);
+ if (c != 1) return;
+ atomic_thread_fence(std::memory_order_acquire);
+
+ int32_t flags = impl->mFlags.load(std::memory_order_relaxed);
+ if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
+ // This is the regular lifetime case. The object is destroyed
+ // when the last strong reference goes away. Since weakref_impl
+ // outlives the object, it is not destroyed in the dtor, and
+ // we'll have to do it here.
+ if (impl->mStrong.load(std::memory_order_relaxed)
+ == INITIAL_STRONG_VALUE) {
+ // Decrementing a weak count to zero when object never had a strong
+ // reference. We assume it acquired a weak reference early, e.g.
+ // in the constructor, and will eventually be properly destroyed,
+ // usually via incrementing and decrementing the strong count.
+ // Thus we no longer do anything here. We log this case, since it
+ // seems to be extremely rare, and should not normally occur. We
+ // used to deallocate mBase here, so this may now indicate a leak.
+ ALOGW("RefBase: Object at %p lost last weak reference "
+ "before it had a strong reference", impl->mBase);
+ } else {
+ // ALOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
+ delete impl;
+ }
+ } else {
+ // This is the OBJECT_LIFETIME_WEAK case. The last weak-reference
+ // is gone, we can destroy the object.
+ impl->mBase->onLastWeakRef(id);
+ delete impl->mBase;
+ }
+}
+
+bool RefBase::weakref_type::attemptIncStrong(const void* id)
+{
+ incWeak(id);
+
+ weakref_impl* const impl = static_cast<weakref_impl*>(this);
+ int32_t curCount = impl->mStrong.load(std::memory_order_relaxed);
+
+ ALOG_ASSERT(curCount >= 0,
+ "attemptIncStrong called on %p after underflow", this);
+
+ while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
+ // we're in the easy/common case of promoting a weak-reference
+ // from an existing strong reference.
+ if (impl->mStrong.compare_exchange_weak(curCount, curCount+1,
+ std::memory_order_relaxed)) {
+ break;
+ }
+ // the strong count has changed on us, we need to re-assert our
+ // situation. curCount was updated by compare_exchange_weak.
+ }
+
+ if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
+ // we're now in the harder case of either:
+ // - there never was a strong reference on us
+ // - or, all strong references have been released
+ int32_t flags = impl->mFlags.load(std::memory_order_relaxed);
+ if ((flags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
+ // this object has a "normal" life-time, i.e.: it gets destroyed
+ // when the last strong reference goes away
+ if (curCount <= 0) {
+ // the last strong-reference got released, the object cannot
+ // be revived.
+ decWeak(id);
+ return false;
+ }
+
+ // here, curCount == INITIAL_STRONG_VALUE, which means
+ // there never was a strong-reference, so we can try to
+ // promote this object; we need to do that atomically.
+ while (curCount > 0) {
+ if (impl->mStrong.compare_exchange_weak(curCount, curCount+1,
+ std::memory_order_relaxed)) {
+ break;
+ }
+ // the strong count has changed on us, we need to re-assert our
+ // situation (e.g.: another thread has inc/decStrong'ed us)
+ // curCount has been updated.
+ }
+
+ if (curCount <= 0) {
+ // promote() failed, some other thread destroyed us in the
+ // meantime (i.e.: strong count reached zero).
+ decWeak(id);
+ return false;
+ }
+ } else {
+ // this object has an "extended" life-time, i.e.: it can be
+ // revived from a weak-reference only.
+ // Ask the object's implementation if it agrees to be revived
+ if (!impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id)) {
+ // it didn't so give-up.
+ decWeak(id);
+ return false;
+ }
+ // grab a strong-reference, which is always safe due to the
+ // extended life-time.
+ curCount = impl->mStrong.fetch_add(1, std::memory_order_relaxed);
+ // If the strong reference count has already been incremented by
+ // someone else, the implementor of onIncStrongAttempted() is holding
+ // an unneeded reference. So call onLastStrongRef() here to remove it.
+ // (No, this is not pretty.) Note that we MUST NOT do this if we
+ // are in fact acquiring the first reference.
+ if (curCount != 0 && curCount != INITIAL_STRONG_VALUE) {
+ impl->mBase->onLastStrongRef(id);
+ }
+ }
+ }
+
+ impl->addStrongRef(id);
+
+#if PRINT_REFS
+ ALOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
+#endif
+
+ // curCount is the value of mStrong before we incremented it.
+ // Now we need to fix-up the count if it was INITIAL_STRONG_VALUE.
+ // This must be done safely, i.e.: handle the case where several threads
+ // were here in attemptIncStrong().
+ // curCount > INITIAL_STRONG_VALUE is OK, and can happen if we're doing
+ // this in the middle of another incStrong. The subtraction is handled
+ // by the thread that started with INITIAL_STRONG_VALUE.
+ if (curCount == INITIAL_STRONG_VALUE) {
+ impl->mStrong.fetch_sub(INITIAL_STRONG_VALUE,
+ std::memory_order_relaxed);
+ }
+
+ return true;
+}
+
+bool RefBase::weakref_type::attemptIncWeak(const void* id)
+{
+ weakref_impl* const impl = static_cast<weakref_impl*>(this);
+
+ int32_t curCount = impl->mWeak.load(std::memory_order_relaxed);
+ ALOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
+ this);
+ while (curCount > 0) {
+ if (impl->mWeak.compare_exchange_weak(curCount, curCount+1,
+ std::memory_order_relaxed)) {
+ break;
+ }
+ // curCount has been updated.
+ }
+
+ if (curCount > 0) {
+ impl->addWeakRef(id);
+ }
+
+ return curCount > 0;
+}
+
+int32_t RefBase::weakref_type::getWeakCount() const
+{
+ // Debug only!
+ return static_cast<const weakref_impl*>(this)->mWeak
+ .load(std::memory_order_relaxed);
+}
+
+void RefBase::weakref_type::printRefs() const
+{
+ static_cast<const weakref_impl*>(this)->printRefs();
+}
+
+void RefBase::weakref_type::trackMe(bool enable, bool retain)
+{
+ static_cast<weakref_impl*>(this)->trackMe(enable, retain);
+}
+
+RefBase::weakref_type* RefBase::createWeak(const void* id) const
+{
+ mRefs->incWeak(id);
+ return mRefs;
+}
+
+RefBase::weakref_type* RefBase::getWeakRefs() const
+{
+ return mRefs;
+}
+
+RefBase::RefBase()
+ : mRefs(new weakref_impl(this))
+{
+}
+
+RefBase::~RefBase()
+{
+ int32_t flags = mRefs->mFlags.load(std::memory_order_relaxed);
+ // Life-time of this object is extended to WEAK, in
+ // which case weakref_impl doesn't out-live the object and we
+ // can free it now.
+ if ((flags & OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_WEAK) {
+ // It's possible that the weak count is not 0 if the object
+ // re-acquired a weak reference in its destructor
+ if (mRefs->mWeak.load(std::memory_order_relaxed) == 0) {
+ delete mRefs;
+ }
+ } else {
+ int32_t strongs = mRefs->mStrong.load(std::memory_order_relaxed);
+
+ if (strongs == INITIAL_STRONG_VALUE) {
+ // We never acquired a strong reference on this object.
+
+ // It would be nice to make this fatal, but many places use RefBase on the stack.
+ // However, this is dangerous because it's also common for code to use the
+ // sp<T>(T*) constructor, assuming that if the object is around, it is already
+ // owned by an sp<>.
+ ALOGW("RefBase: Explicit destruction, weak count = %d (in %p). Use sp<> to manage this "
+ "object.",
+ mRefs->mWeak.load(), this);
+
+#if CALLSTACK_ENABLED
+ CallStack::logStack(LOG_TAG);
+#endif
+ } else if (strongs != 0) {
+ LOG_ALWAYS_FATAL("RefBase: object %p with strong count %d deleted. Double owned?", this,
+ strongs);
+ }
+ }
+ // For debugging purposes, clear mRefs. Ineffective against outstanding wp's.
+ const_cast<weakref_impl*&>(mRefs) = nullptr;
+}
+
+void RefBase::extendObjectLifetime(int32_t mode)
+{
+ check_not_on_stack(this);
+
+ // 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