RefBase.cpp revision 1b2c2a9ea0108cd182a56c47997ec68ee8de02b3 
1/*
2 * Copyright (C) 2005 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#define LOG_TAG "RefBase"
18
19#include <utils/RefBase.h>
20
21#include <utils/Atomic.h>
22#include <utils/CallStack.h>
23#include <utils/Log.h>
24#include <utils/threads.h>
25#include <utils/TextOutput.h>
26
27#include <stdlib.h>
28#include <stdio.h>
29#include <typeinfo>
30#include <sys/types.h>
31#include <sys/stat.h>
32#include <fcntl.h>
33#include <unistd.h>
34
35// compile with refcounting debugging enabled
36#define DEBUG_REFS                      0
37#define DEBUG_REFS_FATAL_SANITY_CHECKS  0
38#define DEBUG_REFS_ENABLED_BY_DEFAULT   1
39#define DEBUG_REFS_CALLSTACK_ENABLED    1
40
41// log all reference counting operations
42#define PRINT_REFS                      0
43
44// ---------------------------------------------------------------------------
45
46namespace android {
47
48#define INITIAL_STRONG_VALUE (1<<28)
49
50// ---------------------------------------------------------------------------
51
52class RefBase::weakref_impl : public RefBase::weakref_type
53{
54public:
55    volatile int32_t    mStrong;
56    volatile int32_t    mWeak;
57    RefBase* const      mBase;
58    volatile int32_t    mFlags;
59
60
61#if !DEBUG_REFS
62
63    weakref_impl(RefBase* base)
64        : mStrong(INITIAL_STRONG_VALUE)
65        , mWeak(0)
66        , mBase(base)
67        , mFlags(0)
68    {
69    }
70
71    void addStrongRef(const void* /*id*/) { }
72    void removeStrongRef(const void* /*id*/) { }
73    void renameStrongRefId(const void* /*old_id*/, const void* /*new_id*/) { }
74    void addWeakRef(const void* /*id*/) { }
75    void removeWeakRef(const void* /*id*/) { }
76    void renameWeakRefId(const void* /*old_id*/, const void* /*new_id*/) { }
77    void printRefs() const { }
78    void trackMe(bool, bool) { }
79
80#else
81
82    weakref_impl(RefBase* base)
83        : mStrong(INITIAL_STRONG_VALUE)
84        , mWeak(0)
85        , mBase(base)
86        , mFlags(0)
87        , mStrongRefs(NULL)
88        , mWeakRefs(NULL)
89        , mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
90        , mRetain(false)
91    {
92    }
93
94    ~weakref_impl()
95    {
96        bool dumpStack = false;
97        if (!mRetain && mStrongRefs != NULL) {
98            dumpStack = true;
99#if DEBUG_REFS_FATAL_SANITY_CHECKS
100            LOG_ALWAYS_FATAL("Strong references remain!");
101#else
102            LOGE("Strong references remain:");
103#endif
104            ref_entry* refs = mStrongRefs;
105            while (refs) {
106                char inc = refs->ref >= 0 ? '+' : '-';
107                LOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
108#if DEBUG_REFS_CALLSTACK_ENABLED
109                refs->stack.dump();
110#endif;
111                refs = refs->next;
112            }
113        }
114
115        if (!mRetain && mWeakRefs != NULL) {
116            dumpStack = true;
117#if DEBUG_REFS_FATAL_SANITY_CHECKS
118            LOG_ALWAYS_FATAL("Weak references remain:");
119#else
120            LOGE("Weak references remain!");
121#endif
122            ref_entry* refs = mWeakRefs;
123            while (refs) {
124                char inc = refs->ref >= 0 ? '+' : '-';
125                LOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
126#if DEBUG_REFS_CALLSTACK_ENABLED
127                refs->stack.dump();
128#endif;
129                refs = refs->next;
130            }
131        }
132        if (dumpStack) {
133            LOGE("above errors at:");
134            CallStack stack;
135            stack.update();
136            stack.dump();
137        }
138    }
139
140    void addStrongRef(const void* id) {
141        //LOGD_IF(mTrackEnabled,
142        //        "addStrongRef: RefBase=%p, id=%p", mBase, id);
143        addRef(&mStrongRefs, id, mStrong);
144    }
145
146    void removeStrongRef(const void* id) {
147        //LOGD_IF(mTrackEnabled,
148        //        "removeStrongRef: RefBase=%p, id=%p", mBase, id);
149        if (!mRetain) {
150            removeRef(&mStrongRefs, id);
151        } else {
152            addRef(&mStrongRefs, id, -mStrong);
153        }
154    }
155
156    void renameStrongRefId(const void* old_id, const void* new_id) {
157        //LOGD_IF(mTrackEnabled,
158        //        "renameStrongRefId: RefBase=%p, oid=%p, nid=%p",
159        //        mBase, old_id, new_id);
160        renameRefsId(mStrongRefs, old_id, new_id);
161    }
162
163    void addWeakRef(const void* id) {
164        addRef(&mWeakRefs, id, mWeak);
165    }
166
167    void removeWeakRef(const void* id) {
168        if (!mRetain) {
169            removeRef(&mWeakRefs, id);
170        } else {
171            addRef(&mWeakRefs, id, -mWeak);
172        }
173    }
174
175    void renameWeakRefId(const void* old_id, const void* new_id) {
176        renameRefsId(mWeakRefs, old_id, new_id);
177    }
178
179    void trackMe(bool track, bool retain)
180    {
181        mTrackEnabled = track;
182        mRetain = retain;
183    }
184
185    void printRefs() const
186    {
187        String8 text;
188
189        {
190            Mutex::Autolock _l(const_cast<weakref_impl*>(this)->mMutex);
191            char buf[128];
192            sprintf(buf, "Strong references on RefBase %p (weakref_type %p):\n", mBase, this);
193            text.append(buf);
194            printRefsLocked(&text, mStrongRefs);
195            sprintf(buf, "Weak references on RefBase %p (weakref_type %p):\n", mBase, this);
196            text.append(buf);
197            printRefsLocked(&text, mWeakRefs);
198        }
199
200        {
201            char name[100];
202            snprintf(name, 100, "/data/%p.stack", this);
203            int rc = open(name, O_RDWR | O_CREAT | O_APPEND);
204            if (rc >= 0) {
205                write(rc, text.string(), text.length());
206                close(rc);
207                LOGD("STACK TRACE for %p saved in %s", this, name);
208            }
209            else LOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this,
210                      name, strerror(errno));
211        }
212    }
213
214private:
215    struct ref_entry
216    {
217        ref_entry* next;
218        const void* id;
219#if DEBUG_REFS_CALLSTACK_ENABLED
220        CallStack stack;
221#endif
222        int32_t ref;
223    };
224
225    void addRef(ref_entry** refs, const void* id, int32_t mRef)
226    {
227        if (mTrackEnabled) {
228            AutoMutex _l(mMutex);
229
230            ref_entry* ref = new ref_entry;
231            // Reference count at the time of the snapshot, but before the
232            // update.  Positive value means we increment, negative--we
233            // decrement the reference count.
234            ref->ref = mRef;
235            ref->id = id;
236#if DEBUG_REFS_CALLSTACK_ENABLED
237            ref->stack.update(2);
238#endif
239            ref->next = *refs;
240            *refs = ref;
241        }
242    }
243
244    void removeRef(ref_entry** refs, const void* id)
245    {
246        if (mTrackEnabled) {
247            AutoMutex _l(mMutex);
248
249            ref_entry* const head = *refs;
250            ref_entry* ref = head;
251            while (ref != NULL) {
252                if (ref->id == id) {
253                    *refs = ref->next;
254                    delete ref;
255                    return;
256                }
257                refs = &ref->next;
258                ref = *refs;
259            }
260
261#if DEBUG_REFS_FATAL_SANITY_CHECKS
262            LOG_ALWAYS_FATAL("RefBase: removing id %p on RefBase %p"
263                    "(weakref_type %p) that doesn't exist!",
264                    id, mBase, this);
265#endif
266
267            LOGE("RefBase: removing id %p on RefBase %p"
268                    "(weakref_type %p) that doesn't exist!",
269                    id, mBase, this);
270
271            ref = head;
272            while (ref) {
273                char inc = ref->ref >= 0 ? '+' : '-';
274                LOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref);
275                ref = ref->next;
276            }
277
278            CallStack stack;
279            stack.update();
280            stack.dump();
281        }
282    }
283
284    void renameRefsId(ref_entry* r, const void* old_id, const void* new_id)
285    {
286        if (mTrackEnabled) {
287            AutoMutex _l(mMutex);
288            ref_entry* ref = r;
289            while (ref != NULL) {
290                if (ref->id == old_id) {
291                    ref->id = new_id;
292                }
293                ref = ref->next;
294            }
295        }
296    }
297
298    void printRefsLocked(String8* out, const ref_entry* refs) const
299    {
300        char buf[128];
301        while (refs) {
302            char inc = refs->ref >= 0 ? '+' : '-';
303            sprintf(buf, "\t%c ID %p (ref %d):\n",
304                    inc, refs->id, refs->ref);
305            out->append(buf);
306#if DEBUG_REFS_CALLSTACK_ENABLED
307            out->append(refs->stack.toString("\t\t"));
308#else
309            out->append("\t\t(call stacks disabled)");
310#endif
311            refs = refs->next;
312        }
313    }
314
315    Mutex mMutex;
316    ref_entry* mStrongRefs;
317    ref_entry* mWeakRefs;
318
319    bool mTrackEnabled;
320    // Collect stack traces on addref and removeref, instead of deleting the stack references
321    // on removeref that match the address ones.
322    bool mRetain;
323
324#endif
325};
326
327// ---------------------------------------------------------------------------
328
329void RefBase::incStrong(const void* id) const
330{
331    weakref_impl* const refs = mRefs;
332    refs->incWeak(id);
333
334    refs->addStrongRef(id);
335    const int32_t c = android_atomic_inc(&refs->mStrong);
336    LOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
337#if PRINT_REFS
338    LOGD("incStrong of %p from %p: cnt=%d\n", this, id, c);
339#endif
340    if (c != INITIAL_STRONG_VALUE)  {
341        return;
342    }
343
344    android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
345    const_cast<RefBase*>(this)->onFirstRef();
346}
347
348void RefBase::decStrong(const void* id) const
349{
350    weakref_impl* const refs = mRefs;
351    refs->removeStrongRef(id);
352    const int32_t c = android_atomic_dec(&refs->mStrong);
353#if PRINT_REFS
354    LOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
355#endif
356    LOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
357    if (c == 1) {
358        const_cast<RefBase*>(this)->onLastStrongRef(id);
359        if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
360            delete this;
361        }
362    }
363    refs->decWeak(id);
364}
365
366void RefBase::forceIncStrong(const void* id) const
367{
368    weakref_impl* const refs = mRefs;
369    refs->incWeak(id);
370
371    refs->addStrongRef(id);
372    const int32_t c = android_atomic_inc(&refs->mStrong);
373    LOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
374               refs);
375#if PRINT_REFS
376    LOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
377#endif
378
379    switch (c) {
380    case INITIAL_STRONG_VALUE:
381        android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
382        // fall through...
383    case 0:
384        const_cast<RefBase*>(this)->onFirstRef();
385    }
386}
387
388int32_t RefBase::getStrongCount() const
389{
390    return mRefs->mStrong;
391}
392
393
394
395RefBase* RefBase::weakref_type::refBase() const
396{
397    return static_cast<const weakref_impl*>(this)->mBase;
398}
399
400void RefBase::weakref_type::incWeak(const void* id)
401{
402    weakref_impl* const impl = static_cast<weakref_impl*>(this);
403    impl->addWeakRef(id);
404    const int32_t c = android_atomic_inc(&impl->mWeak);
405    LOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
406}
407
408void RefBase::weakref_type::decWeak(const void* id)
409{
410    weakref_impl* const impl = static_cast<weakref_impl*>(this);
411    impl->removeWeakRef(id);
412    const int32_t c = android_atomic_dec(&impl->mWeak);
413    LOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
414    if (c != 1) return;
415
416    if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
417        if (impl->mStrong == INITIAL_STRONG_VALUE)
418            delete impl->mBase;
419        else {
420            // LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
421            delete impl;
422        }
423    } else {
424        impl->mBase->onLastWeakRef(id);
425        if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
426            delete impl->mBase;
427        }
428    }
429}
430
431bool RefBase::weakref_type::attemptIncStrong(const void* id)
432{
433    incWeak(id);
434
435    weakref_impl* const impl = static_cast<weakref_impl*>(this);
436
437    int32_t curCount = impl->mStrong;
438    LOG_ASSERT(curCount >= 0, "attemptIncStrong called on %p after underflow",
439               this);
440    while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
441        if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
442            break;
443        }
444        curCount = impl->mStrong;
445    }
446
447    if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
448        bool allow;
449        if (curCount == INITIAL_STRONG_VALUE) {
450            // Attempting to acquire first strong reference...  this is allowed
451            // if the object does NOT have a longer lifetime (meaning the
452            // implementation doesn't need to see this), or if the implementation
453            // allows it to happen.
454            allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK
455                  || impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
456        } else {
457            // Attempting to revive the object...  this is allowed
458            // if the object DOES have a longer lifetime (so we can safely
459            // call the object with only a weak ref) and the implementation
460            // allows it to happen.
461            allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_WEAK
462                  && impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
463        }
464        if (!allow) {
465            decWeak(id);
466            return false;
467        }
468        curCount = android_atomic_inc(&impl->mStrong);
469
470        // If the strong reference count has already been incremented by
471        // someone else, the implementor of onIncStrongAttempted() is holding
472        // an unneeded reference.  So call onLastStrongRef() here to remove it.
473        // (No, this is not pretty.)  Note that we MUST NOT do this if we
474        // are in fact acquiring the first reference.
475        if (curCount > 0 && curCount < INITIAL_STRONG_VALUE) {
476            impl->mBase->onLastStrongRef(id);
477        }
478    }
479
480    impl->addStrongRef(id);
481
482#if PRINT_REFS
483    LOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
484#endif
485
486    if (curCount == INITIAL_STRONG_VALUE) {
487        android_atomic_add(-INITIAL_STRONG_VALUE, &impl->mStrong);
488        impl->mBase->onFirstRef();
489    }
490
491    return true;
492}
493
494bool RefBase::weakref_type::attemptIncWeak(const void* id)
495{
496    weakref_impl* const impl = static_cast<weakref_impl*>(this);
497
498    int32_t curCount = impl->mWeak;
499    LOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
500               this);
501    while (curCount > 0) {
502        if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mWeak) == 0) {
503            break;
504        }
505        curCount = impl->mWeak;
506    }
507
508    if (curCount > 0) {
509        impl->addWeakRef(id);
510    }
511
512    return curCount > 0;
513}
514
515int32_t RefBase::weakref_type::getWeakCount() const
516{
517    return static_cast<const weakref_impl*>(this)->mWeak;
518}
519
520void RefBase::weakref_type::printRefs() const
521{
522    static_cast<const weakref_impl*>(this)->printRefs();
523}
524
525void RefBase::weakref_type::trackMe(bool enable, bool retain)
526{
527    static_cast<const weakref_impl*>(this)->trackMe(enable, retain);
528}
529
530RefBase::weakref_type* RefBase::createWeak(const void* id) const
531{
532    mRefs->incWeak(id);
533    return mRefs;
534}
535
536RefBase::weakref_type* RefBase::getWeakRefs() const
537{
538    return mRefs;
539}
540
541RefBase::RefBase()
542    : mRefs(new weakref_impl(this))
543{
544}
545
546RefBase::~RefBase()
547{
548    if (mRefs->mWeak == 0) {
549        delete mRefs;
550    }
551}
552
553void RefBase::extendObjectLifetime(int32_t mode)
554{
555    android_atomic_or(mode, &mRefs->mFlags);
556}
557
558void RefBase::onFirstRef()
559{
560}
561
562void RefBase::onLastStrongRef(const void* /*id*/)
563{
564}
565
566bool RefBase::onIncStrongAttempted(uint32_t flags, const void* id)
567{
568    return (flags&FIRST_INC_STRONG) ? true : false;
569}
570
571void RefBase::onLastWeakRef(const void* /*id*/)
572{
573}
574
575// ---------------------------------------------------------------------------
576
577void RefBase::moveReferences(void* dst, void const* src, size_t n,
578        const ReferenceConverterBase& caster)
579{
580#if DEBUG_REFS
581    const size_t itemSize = caster.getReferenceTypeSize();
582    for (size_t i=0 ; i<n ; i++) {
583        void*       d = reinterpret_cast<void      *>(intptr_t(dst) + i*itemSize);
584        void const* s = reinterpret_cast<void const*>(intptr_t(src) + i*itemSize);
585        RefBase* ref(reinterpret_cast<RefBase*>(caster.getReferenceBase(d)));
586        ref->mRefs->renameStrongRefId(s, d);
587        ref->mRefs->renameWeakRefId(s, d);
588    }
589#endif
590}
591
592// ---------------------------------------------------------------------------
593
594TextOutput& printStrongPointer(TextOutput& to, const void* val)
595{
596    to << "sp<>(" << val << ")";
597    return to;
598}
599
600TextOutput& printWeakPointer(TextOutput& to, const void* val)
601{
602    to << "wp<>(" << val << ")";
603    return to;
604}
605
606
607}; // namespace android
608