1/*
2 Copyright 2005-2013 Intel Corporation. All Rights Reserved.
3
4 This file is part of Threading Building Blocks.
5
6 Threading Building Blocks is free software; you can redistribute it
7 and/or modify it under the terms of the GNU General Public License
8 version 2 as published by the Free Software Foundation.
9
10 Threading Building Blocks is distributed in the hope that it will be
11 useful, but WITHOUT ANY WARRANTY; without even the implied warranty
12 of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with Threading Building Blocks; if not, write to the Free Software
17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18
19 As a special exception, you may use this file as part of a free software
20 library without restriction. Specifically, if other files instantiate
21 templates or use macros or inline functions from this file, or you compile
22 this file and link it with other files to produce an executable, this
23 file does not by itself cause the resulting executable to be covered by
24 the GNU General Public License. This exception does not however
25 invalidate any other reasons why the executable file might be covered by
26 the GNU General Public License.
27*/
28
29#ifndef __TBB_mutex_padding_H
30#define __TBB_mutex_padding_H
31
32// wrapper for padding mutexes to be alone on a cache line, without requiring they be allocated
33// from a pool. Because we allow them to be defined anywhere they must be two cache lines in size.
34
35namespace tbb {
36namespace interface7 {
37namespace internal {
38
39static const size_t cache_line_size = 64;
40
41// Pad a mutex to occupy a number of full cache lines sufficient to avoid false sharing
42// with other data; space overhead is up to 2*cache_line_size-1.
43template<typename Mutex>
44class padded_mutex {
45 typedef long pad_type;
46 pad_type my_pad[((sizeof(Mutex)+cache_line_size-1)/cache_line_size+1)*cache_line_size/sizeof(pad_type)];
47
48 Mutex *impl() { return (Mutex *)((uintptr_t(this)|(cache_line_size-1))+1);}
49
50public:
51 static const bool is_rw_mutex = Mutex::is_rw_mutex;
52 static const bool is_recursive_mutex = Mutex::is_recursive_mutex;
53 static const bool is_fair_mutex = Mutex::is_fair_mutex;
54
55 padded_mutex() { new(impl()) Mutex(); }
56 ~padded_mutex() { impl()->~Mutex(); }
57
58 //! Represents acquisition of a mutex.
59 class scoped_lock : tbb::internal::no_copy {
60 typename Mutex::scoped_lock my_scoped_lock;
61 public:
62 scoped_lock() : my_scoped_lock() {}
63 scoped_lock( padded_mutex& m ) : my_scoped_lock(*m.impl()) { }
64 ~scoped_lock() { }
65
66 void acquire( padded_mutex& m ) { my_scoped_lock.acquire(*m.impl()); }
67 bool try_acquire( padded_mutex& m ) { return my_scoped_lock.try_acquire(*m.impl()); }
68 void release() { my_scoped_lock.release(); }
69 };
70};
71
72} // namespace internal
73} // namespace interface7
74} // namespace tbb
75
76#endif /* __TBB_mutex_padding_H */
77