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/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMutex_pthread_DEFINED
#define SkMutex_pthread_DEFINED
/** Posix pthread_mutex based mutex. */
#include <errno.h>
#include <pthread.h>
// This isn't technically portable, but on Linux and Android pthread_t is some sort of int, and
// on Darwin it's a pointer. So assuming pthread_self() never returns 0, it works as a sentinel.
SkDEBUGCODE(static const pthread_t kNoOwner = 0;)
// A SkBaseMutex is a POD structure that can be directly initialized
// at declaration time with SK_DECLARE_STATIC/GLOBAL_MUTEX. This avoids the
// generation of a static initializer in the final machine code (and
// a corresponding static finalizer).
struct SkBaseMutex {
void acquire() {
SkASSERT(0 == pthread_equal(fOwner, pthread_self())); // SkMutex is not re-entrant
pthread_mutex_lock(&fMutex);
SkDEBUGCODE(fOwner = pthread_self();)
}
void release() {
this->assertHeld();
SkDEBUGCODE(fOwner = kNoOwner;)
pthread_mutex_unlock(&fMutex);
}
void assertHeld() {
SkASSERT(0 != pthread_equal(fOwner, pthread_self()));
}
pthread_mutex_t fMutex;
SkDEBUGCODE(pthread_t fOwner;)
};
// A normal mutex that requires to be initialized through normal C++ construction,
// i.e. when it's a member of another class, or allocated on the heap.
class SkMutex : public SkBaseMutex {
public:
SkMutex() {
SkDEBUGCODE(int status = )pthread_mutex_init(&fMutex, NULL);
SkDEBUGCODE(
if (status != 0) {
print_pthread_error(status);
SkASSERT(0 == status);
}
fOwner = kNoOwner;
)
}
~SkMutex() {
SkDEBUGCODE(int status = )pthread_mutex_destroy(&fMutex);
SkDEBUGCODE(
if (status != 0) {
print_pthread_error(status);
SkASSERT(0 == status);
}
)
}
private:
SkMutex(const SkMutex&);
SkMutex& operator=(const SkMutex&);
static void print_pthread_error(int status) {
switch (status) {
case 0: // success
break;
case EINVAL:
SkDebugf("pthread error [%d] EINVAL\n", status);
break;
case EBUSY:
SkDebugf("pthread error [%d] EBUSY\n", status);
break;
default:
SkDebugf("pthread error [%d] unknown\n", status);
break;
}
}
};
#define SK_BASE_MUTEX_INIT { PTHREAD_MUTEX_INITIALIZER, SkDEBUGCODE(0) }
// Using POD-style initialization prevents the generation of a static initializer.
//
// Without magic statics there are no thread safety guarantees on initialization
// of local statics (even POD). As a result, it is illegal to use
// SK_DECLARE_STATIC_MUTEX in a function.
//
// Because SkBaseMutex is not a primitive, a static SkBaseMutex cannot be
// initialized in a class with this macro.
#define SK_DECLARE_STATIC_MUTEX(name) namespace {} static SkBaseMutex name = SK_BASE_MUTEX_INIT
#endif
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