1
2/*
3 * Copyright 2006 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#ifndef SkThread_platform_DEFINED
11#define SkThread_platform_DEFINED
12
13#if defined(SK_BUILD_FOR_ANDROID)
14
15#if !defined(SK_BUILD_FOR_ANDROID_FRAMEWORK)
16
17#include <stdint.h>
18
19/* Just use the GCC atomic intrinsics. They're supported by the NDK toolchain,
20 * have reasonable performance, and provide full memory barriers
21 */
22static inline __attribute__((always_inline)) int32_t sk_atomic_inc(int32_t *addr) {
23    return __sync_fetch_and_add(addr, 1);
24}
25
26static inline __attribute__((always_inline)) int32_t sk_atomic_add(int32_t *addr, int32_t inc) {
27    return __sync_fetch_and_add(addr, inc);
28}
29
30static inline __attribute__((always_inline)) int32_t sk_atomic_dec(int32_t *addr) {
31    return __sync_fetch_and_add(addr, -1);
32}
33static inline __attribute__((always_inline)) void sk_membar_aquire__after_atomic_dec() { }
34
35static inline __attribute__((always_inline)) int32_t sk_atomic_conditional_inc(int32_t* addr) {
36    int32_t value = *addr;
37
38    while (true) {
39        if (value == 0) {
40            return 0;
41        }
42
43        int32_t before = __sync_val_compare_and_swap(addr, value, value + 1);
44
45        if (before == value) {
46            return value;
47        } else {
48            value = before;
49        }
50    }
51}
52static inline __attribute__((always_inline)) void sk_membar_aquire__after_atomic_conditional_inc() { }
53
54#else // SK_BUILD_FOR_ANDROID_FRAMEWORK
55
56/* The platform atomics operations are slightly more efficient than the
57 * GCC built-ins, so use them.
58 */
59#include <utils/Atomic.h>
60
61#define sk_atomic_inc(addr)         android_atomic_inc(addr)
62#define sk_atomic_add(addr, inc)    android_atomic_add(inc, addr)
63#define sk_atomic_dec(addr)         android_atomic_dec(addr)
64
65static inline __attribute__((always_inline)) void sk_membar_aquire__after_atomic_dec() {
66    //HACK: Android is actually using full memory barriers.
67    //      Should this change, uncomment below.
68    //int dummy;
69    //android_atomic_aquire_store(0, &dummy);
70}
71static inline __attribute__((always_inline)) int32_t sk_atomic_conditional_inc(int32_t* addr) {
72    while (true) {
73        int32_t value = *addr;
74        if (value == 0) {
75            return 0;
76        }
77        if (0 == android_atomic_release_cas(value, value + 1, addr)) {
78            return value;
79        }
80    }
81}
82static inline __attribute__((always_inline)) void sk_membar_aquire__after_atomic_conditional_inc() {
83    //HACK: Android is actually using full memory barriers.
84    //      Should this change, uncomment below.
85    //int dummy;
86    //android_atomic_aquire_store(0, &dummy);
87}
88
89#endif // SK_BUILD_FOR_ANDROID_FRAMEWORK
90
91#else  // !SK_BUILD_FOR_ANDROID
92
93/** Implemented by the porting layer, this function adds one to the int
94    specified by the address (in a thread-safe manner), and returns the
95    previous value.
96    No additional memory barrier is required.
97    This must act as a compiler barrier.
98*/
99SK_API int32_t sk_atomic_inc(int32_t* addr);
100
101/** Implemented by the porting layer, this function adds inc to the int
102    specified by the address (in a thread-safe manner), and returns the
103    previous value.
104    No additional memory barrier is required.
105    This must act as a compiler barrier.
106 */
107SK_API int32_t sk_atomic_add(int32_t* addr, int32_t inc);
108
109/** Implemented by the porting layer, this function subtracts one from the int
110    specified by the address (in a thread-safe manner), and returns the
111    previous value.
112    Expected to act as a release (SL/S) memory barrier and a compiler barrier.
113*/
114SK_API int32_t sk_atomic_dec(int32_t* addr);
115/** If sk_atomic_dec does not act as an aquire (L/SL) barrier, this is expected
116    to act as an aquire (L/SL) memory barrier and as a compiler barrier.
117*/
118SK_API void sk_membar_aquire__after_atomic_dec();
119
120/** Implemented by the porting layer, this function adds one to the int
121    specified by the address iff the int specified by the address is not zero
122    (in a thread-safe manner), and returns the previous value.
123    No additional memory barrier is required.
124    This must act as a compiler barrier.
125*/
126SK_API int32_t sk_atomic_conditional_inc(int32_t*);
127/** If sk_atomic_conditional_inc does not act as an aquire (L/SL) barrier, this
128    is expected to act as an aquire (L/SL) memory barrier and as a compiler
129    barrier.
130*/
131SK_API void sk_membar_aquire__after_atomic_conditional_inc();
132
133#endif // !SK_BUILD_FOR_ANDROID
134
135#ifdef SK_USE_POSIX_THREADS
136
137#include <pthread.h>
138
139// A SkBaseMutex is a POD structure that can be directly initialized
140// at declaration time with SK_DECLARE_STATIC/GLOBAL_MUTEX. This avoids the
141// generation of a static initializer in the final machine code (and
142// a corresponding static finalizer).
143//
144struct SkBaseMutex {
145    void    acquire() { pthread_mutex_lock(&fMutex); }
146    void    release() { pthread_mutex_unlock(&fMutex); }
147    pthread_mutex_t  fMutex;
148};
149
150// Using POD-style initialization prevents the generation of a static initializer
151// and keeps the acquire() implementation small and fast.
152#define SK_DECLARE_STATIC_MUTEX(name)   static SkBaseMutex  name = { PTHREAD_MUTEX_INITIALIZER }
153
154// Special case used when the static mutex must be available globally.
155#define SK_DECLARE_GLOBAL_MUTEX(name)   SkBaseMutex  name = { PTHREAD_MUTEX_INITIALIZER }
156
157// A normal mutex that requires to be initialized through normal C++ construction,
158// i.e. when it's a member of another class, or allocated on the heap.
159class SK_API SkMutex : public SkBaseMutex, SkNoncopyable {
160public:
161    SkMutex();
162    ~SkMutex();
163};
164
165#else // !SK_USE_POSIX_THREADS
166
167// In the generic case, SkBaseMutex and SkMutex are the same thing, and we
168// can't easily get rid of static initializers.
169//
170class SK_API SkMutex : SkNoncopyable {
171public:
172    SkMutex();
173    ~SkMutex();
174
175    void    acquire();
176    void    release();
177
178private:
179    bool fIsGlobal;
180    enum {
181        kStorageIntCount = 64
182    };
183    uint32_t    fStorage[kStorageIntCount];
184};
185
186typedef SkMutex SkBaseMutex;
187
188#define SK_DECLARE_STATIC_MUTEX(name)           static SkBaseMutex  name
189#define SK_DECLARE_GLOBAL_MUTEX(name)           SkBaseMutex  name
190
191#endif // !SK_USE_POSIX_THREADS
192
193
194#endif
195