1/*
2 * Copyright 2013 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkMutex_pthread_DEFINED
9#define SkMutex_pthread_DEFINED
10
11/** Posix pthread_mutex based mutex. */
12
13#include <errno.h>
14#include <pthread.h>
15
16// This isn't technically portable, but on Linux and Android pthread_t is some sort of int, and
17// on Darwin it's a pointer.  So assuming pthread_self() never returns 0, it works as a sentinel.
18SkDEBUGCODE(static const pthread_t kNoOwner = 0;)
19
20// A SkBaseMutex is a POD structure that can be directly initialized
21// at declaration time with SK_DECLARE_STATIC/GLOBAL_MUTEX. This avoids the
22// generation of a static initializer in the final machine code (and
23// a corresponding static finalizer).
24struct SkBaseMutex {
25    void acquire() {
26        SkASSERT(0 == pthread_equal(fOwner, pthread_self()));  // SkMutex is not re-entrant
27        pthread_mutex_lock(&fMutex);
28        SkDEBUGCODE(fOwner = pthread_self();)
29    }
30    void release() {
31        this->assertHeld();
32        SkDEBUGCODE(fOwner = kNoOwner;)
33        pthread_mutex_unlock(&fMutex);
34    }
35    void assertHeld() {
36        SkASSERT(0 != pthread_equal(fOwner, pthread_self()));
37    }
38
39    pthread_mutex_t fMutex;
40    SkDEBUGCODE(pthread_t fOwner;)
41};
42
43// A normal mutex that requires to be initialized through normal C++ construction,
44// i.e. when it's a member of another class, or allocated on the heap.
45class SkMutex : public SkBaseMutex {
46public:
47    SkMutex() {
48        SkDEBUGCODE(int status = )pthread_mutex_init(&fMutex, NULL);
49        SkDEBUGCODE(
50            if (status != 0) {
51                print_pthread_error(status);
52                SkASSERT(0 == status);
53            }
54            fOwner = kNoOwner;
55        )
56    }
57
58    ~SkMutex() {
59        SkDEBUGCODE(int status = )pthread_mutex_destroy(&fMutex);
60        SkDEBUGCODE(
61            if (status != 0) {
62                print_pthread_error(status);
63                SkASSERT(0 == status);
64            }
65        )
66    }
67
68private:
69    SkMutex(const SkMutex&);
70    SkMutex& operator=(const SkMutex&);
71
72    static void print_pthread_error(int status) {
73        switch (status) {
74        case 0: // success
75            break;
76        case EINVAL:
77            SkDebugf("pthread error [%d] EINVAL\n", status);
78            break;
79        case EBUSY:
80            SkDebugf("pthread error [%d] EBUSY\n", status);
81            break;
82        default:
83            SkDebugf("pthread error [%d] unknown\n", status);
84            break;
85        }
86    }
87};
88
89#define SK_BASE_MUTEX_INIT { PTHREAD_MUTEX_INITIALIZER, SkDEBUGCODE(0) }
90
91// Using POD-style initialization prevents the generation of a static initializer.
92//
93// Without magic statics there are no thread safety guarantees on initialization
94// of local statics (even POD). As a result, it is illegal to use
95// SK_DECLARE_STATIC_MUTEX in a function.
96//
97// Because SkBaseMutex is not a primitive, a static SkBaseMutex cannot be
98// initialized in a class with this macro.
99#define SK_DECLARE_STATIC_MUTEX(name) namespace {} static SkBaseMutex name = SK_BASE_MUTEX_INIT
100
101#endif
102