RefBase.cpp revision f3d939c5e5c2fa9b1ffea817fde3eece869e2bec 
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::destroy() const {
349    delete this;
350}
351
352void RefBase::decStrong(const void* id) const
353{
354    weakref_impl* const refs = mRefs;
355    refs->removeStrongRef(id);
356    const int32_t c = android_atomic_dec(&refs->mStrong);
357#if PRINT_REFS
358    LOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
359#endif
360    LOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
361    if (c == 1) {
362        const_cast<RefBase*>(this)->onLastStrongRef(id);
363        if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
364            destroy();
365        }
366    }
367    refs->decWeak(id);
368}
369
370void RefBase::forceIncStrong(const void* id) const
371{
372    weakref_impl* const refs = mRefs;
373    refs->incWeak(id);
374
375    refs->addStrongRef(id);
376    const int32_t c = android_atomic_inc(&refs->mStrong);
377    LOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
378               refs);
379#if PRINT_REFS
380    LOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
381#endif
382
383    switch (c) {
384    case INITIAL_STRONG_VALUE:
385        android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
386        // fall through...
387    case 0:
388        const_cast<RefBase*>(this)->onFirstRef();
389    }
390}
391
392int32_t RefBase::getStrongCount() const
393{
394    return mRefs->mStrong;
395}
396
397
398
399RefBase* RefBase::weakref_type::refBase() const
400{
401    return static_cast<const weakref_impl*>(this)->mBase;
402}
403
404void RefBase::weakref_type::incWeak(const void* id)
405{
406    weakref_impl* const impl = static_cast<weakref_impl*>(this);
407    impl->addWeakRef(id);
408    const int32_t c = android_atomic_inc(&impl->mWeak);
409    LOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
410}
411
412void RefBase::weakref_type::decWeak(const void* id)
413{
414    weakref_impl* const impl = static_cast<weakref_impl*>(this);
415    impl->removeWeakRef(id);
416    const int32_t c = android_atomic_dec(&impl->mWeak);
417    LOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
418    if (c != 1) return;
419
420    if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
421        if (impl->mStrong == INITIAL_STRONG_VALUE)
422            if (impl->mBase)
423                impl->mBase->destroy();
424        else {
425            // LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
426            delete impl;
427        }
428    } else {
429        impl->mBase->onLastWeakRef(id);
430        if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
431            if (impl->mBase)
432                impl->mBase->destroy();
433        }
434    }
435}
436
437bool RefBase::weakref_type::attemptIncStrong(const void* id)
438{
439    incWeak(id);
440
441    weakref_impl* const impl = static_cast<weakref_impl*>(this);
442
443    int32_t curCount = impl->mStrong;
444    LOG_ASSERT(curCount >= 0, "attemptIncStrong called on %p after underflow",
445               this);
446    while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
447        if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
448            break;
449        }
450        curCount = impl->mStrong;
451    }
452
453    if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
454        bool allow;
455        if (curCount == INITIAL_STRONG_VALUE) {
456            // Attempting to acquire first strong reference...  this is allowed
457            // if the object does NOT have a longer lifetime (meaning the
458            // implementation doesn't need to see this), or if the implementation
459            // allows it to happen.
460            allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK
461                  || impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
462        } else {
463            // Attempting to revive the object...  this is allowed
464            // if the object DOES have a longer lifetime (so we can safely
465            // call the object with only a weak ref) and the implementation
466            // allows it to happen.
467            allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_WEAK
468                  && impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
469        }
470        if (!allow) {
471            decWeak(id);
472            return false;
473        }
474        curCount = android_atomic_inc(&impl->mStrong);
475
476        // If the strong reference count has already been incremented by
477        // someone else, the implementor of onIncStrongAttempted() is holding
478        // an unneeded reference.  So call onLastStrongRef() here to remove it.
479        // (No, this is not pretty.)  Note that we MUST NOT do this if we
480        // are in fact acquiring the first reference.
481        if (curCount > 0 && curCount < INITIAL_STRONG_VALUE) {
482            impl->mBase->onLastStrongRef(id);
483        }
484    }
485
486    impl->addStrongRef(id);
487
488#if PRINT_REFS
489    LOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
490#endif
491
492    if (curCount == INITIAL_STRONG_VALUE) {
493        android_atomic_add(-INITIAL_STRONG_VALUE, &impl->mStrong);
494        impl->mBase->onFirstRef();
495    }
496
497    return true;
498}
499
500bool RefBase::weakref_type::attemptIncWeak(const void* id)
501{
502    weakref_impl* const impl = static_cast<weakref_impl*>(this);
503
504    int32_t curCount = impl->mWeak;
505    LOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
506               this);
507    while (curCount > 0) {
508        if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mWeak) == 0) {
509            break;
510        }
511        curCount = impl->mWeak;
512    }
513
514    if (curCount > 0) {
515        impl->addWeakRef(id);
516    }
517
518    return curCount > 0;
519}
520
521int32_t RefBase::weakref_type::getWeakCount() const
522{
523    return static_cast<const weakref_impl*>(this)->mWeak;
524}
525
526void RefBase::weakref_type::printRefs() const
527{
528    static_cast<const weakref_impl*>(this)->printRefs();
529}
530
531void RefBase::weakref_type::trackMe(bool enable, bool retain)
532{
533    static_cast<const weakref_impl*>(this)->trackMe(enable, retain);
534}
535
536RefBase::weakref_type* RefBase::createWeak(const void* id) const
537{
538    mRefs->incWeak(id);
539    return mRefs;
540}
541
542RefBase::weakref_type* RefBase::getWeakRefs() const
543{
544    return mRefs;
545}
546
547RefBase::RefBase()
548    : mRefs(new weakref_impl(this))
549{
550}
551
552RefBase::~RefBase()
553{
554    if (mRefs->mWeak == 0) {
555        delete mRefs;
556    }
557}
558
559void RefBase::extendObjectLifetime(int32_t mode)
560{
561    android_atomic_or(mode, &mRefs->mFlags);
562}
563
564void RefBase::onFirstRef()
565{
566}
567
568void RefBase::onLastStrongRef(const void* /*id*/)
569{
570}
571
572bool RefBase::onIncStrongAttempted(uint32_t flags, const void* id)
573{
574    return (flags&FIRST_INC_STRONG) ? true : false;
575}
576
577void RefBase::onLastWeakRef(const void* /*id*/)
578{
579}
580
581// ---------------------------------------------------------------------------
582
583void RefBase::moveReferences(void* dst, void const* src, size_t n,
584        const ReferenceConverterBase& caster)
585{
586#if DEBUG_REFS
587    const size_t itemSize = caster.getReferenceTypeSize();
588    for (size_t i=0 ; i<n ; i++) {
589        void*       d = reinterpret_cast<void      *>(intptr_t(dst) + i*itemSize);
590        void const* s = reinterpret_cast<void const*>(intptr_t(src) + i*itemSize);
591        RefBase* ref(reinterpret_cast<RefBase*>(caster.getReferenceBase(d)));
592        ref->mRefs->renameStrongRefId(s, d);
593        ref->mRefs->renameWeakRefId(s, d);
594    }
595#endif
596}
597
598// ---------------------------------------------------------------------------
599
600TextOutput& printStrongPointer(TextOutput& to, const void* val)
601{
602    to << "sp<>(" << val << ")";
603    return to;
604}
605
606TextOutput& printWeakPointer(TextOutput& to, const void* val)
607{
608    to << "wp<>(" << val << ")";
609    return to;
610}
611
612
613}; // namespace android
614