1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
|
/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* $Source: src/include/util/lockfree/atomic_construct.H $ */
/* */
/* OpenPOWER HostBoot Project */
/* */
/* COPYRIGHT International Business Machines Corp. 2011,2014 */
/* */
/* Licensed under the Apache License, Version 2.0 (the "License"); */
/* you may not use this file except in compliance with the License. */
/* You may obtain a copy of the License at */
/* */
/* http://www.apache.org/licenses/LICENSE-2.0 */
/* */
/* Unless required by applicable law or agreed to in writing, software */
/* distributed under the License is distributed on an "AS IS" BASIS, */
/* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or */
/* implied. See the License for the specific language governing */
/* permissions and limitations under the License. */
/* */
/* IBM_PROLOG_END_TAG */
#ifndef __UTIL_LOCKFREE_ATOMIC_CONSTRUCT_H
#define __UTIL_LOCKFREE_ATOMIC_CONSTRUCT_H
namespace Util
{
namespace Lockfree
{
/** @brief Atomically construct an object and assign it to a pointer.
*
* This function will check if a pointer is still NULL and
* construct an object, atomically, if needed. If the pointer is
* not NULL, the current instance will be left alone.
*
* @param[in] ptr - Pointer-pointer to the object.
*
* Example:
* Foo* iv_foo; //<--- instance variable in class.
* atomic_construct(&iv_foo);
*
* @note It is possible for multiple instances to temporarily exist,
* if this code is called from multiple CPUs, but only the one
* instance will exist outside the lifetime of this function.
*/
template<typename _T>
void atomic_construct(_T** ptr)
{
if (__sync_bool_compare_and_swap(ptr, NULL, NULL))
{
_T* instance = new _T();
if (!__sync_bool_compare_and_swap(ptr, NULL, instance))
{
delete instance;
}
}
}
};
};
#endif
|
