1 /* -*- mode: C; c-basic-offset: 3; indent-tabs-mode: nil; -*- */
2 /*
3 This file is part of drd, a thread error detector.
4
5 Copyright (C) 2006-2011 Bart Van Assche <bvanassche@acm.org>.
6
7 This program is free software; you can redistribute it and/or
8 modify it under the terms of the GNU General Public License as
9 published by the Free Software Foundation; either version 2 of the
10 License, or (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
20 02111-1307, USA.
21
22 The GNU General Public License is contained in the file COPYING.
23 */
24
25
26 #ifndef __DRD_VC_H
27 #define __DRD_VC_H
28
29
30 /*
31 * DRD vector clock implementation:
32 * - One counter per thread.
33 * - A vector clock is implemented as multiple pairs of (thread id, counter).
34 * - Pairs are stored in an array sorted by thread id.
35 *
36 * Semantics:
37 * - Each time a thread performs an action that implies an ordering between
38 * intra-thread events, the counter of that thread is incremented.
39 * - Vector clocks are compared by comparing all counters of all threads.
40 * - When a thread synchronization action is performed that guarantees that
41 * new actions of the current thread are executed after the actions of the
42 * other thread, the vector clock of the synchronization object and the
43 * current thread are combined (by taking the component-wise maximum).
44 * - A vector clock is incremented during actions such as
45 * pthread_create(), pthread_mutex_unlock(), sem_post(). (Actions where
46 * an inter-thread ordering "arrow" starts).
47 */
48
49
50 #include "pub_tool_basics.h" /* Addr, SizeT */
51 #include "drd_basics.h" /* DrdThreadId */
52 #include "pub_tool_libcassert.h" /* tl_assert() */
53
54
55 #define VC_PREALLOCATED 8
56
57
58 /** Vector clock element. */
59 typedef struct
60 {
61 DrdThreadId threadid;
62 UInt count;
63 } VCElem;
64
65 typedef struct
66 {
67 unsigned capacity; /**< number of elements allocated for array vc. */
68 unsigned size; /**< number of elements used of array vc. */
69 VCElem* vc; /**< vector clock elements. */
70 VCElem preallocated[VC_PREALLOCATED];
71 } VectorClock;
72
73
74 void DRD_(vc_init)(VectorClock* const vc,
75 const VCElem* const vcelem,
76 const unsigned size);
77 void DRD_(vc_cleanup)(VectorClock* const vc);
78 void DRD_(vc_copy)(VectorClock* const new, const VectorClock* const rhs);
79 void DRD_(vc_assign)(VectorClock* const lhs, const VectorClock* const rhs);
80 void DRD_(vc_increment)(VectorClock* const vc, DrdThreadId const tid);
81 static __inline__
82 Bool DRD_(vc_lte)(const VectorClock* const vc1,
83 const VectorClock* const vc2);
84 Bool DRD_(vc_ordered)(const VectorClock* const vc1,
85 const VectorClock* const vc2);
86 void DRD_(vc_min)(VectorClock* const result,
87 const VectorClock* const rhs);
88 void DRD_(vc_combine)(VectorClock* const result,
89 const VectorClock* const rhs);
90 void DRD_(vc_print)(const VectorClock* const vc);
91 char* DRD_(vc_aprint)(const VectorClock* const vc);
92 void DRD_(vc_check)(const VectorClock* const vc);
93 void DRD_(vc_test)(void);
94
95
96
97 /**
98 * @return True if all thread id's that are present in vc1 also exist in
99 * vc2, and if additionally all corresponding counters in v2 are higher or
100 * equal.
101 */
102 static __inline__
DRD_(vc_lte)103 Bool DRD_(vc_lte)(const VectorClock* const vc1, const VectorClock* const vc2)
104 {
105 unsigned i;
106 unsigned j = 0;
107
108 for (i = 0; i < vc1->size; i++)
109 {
110 while (j < vc2->size && vc2->vc[j].threadid < vc1->vc[i].threadid)
111 j++;
112 if (j >= vc2->size || vc2->vc[j].threadid > vc1->vc[i].threadid)
113 return False;
114 #ifdef ENABLE_DRD_CONSISTENCY_CHECKS
115 /*
116 * This assert statement has been commented out because of performance
117 * reasons.
118 */
119 tl_assert(j < vc2->size && vc2->vc[j].threadid == vc1->vc[i].threadid);
120 #endif
121 if (vc1->vc[i].count > vc2->vc[j].count)
122 return False;
123 }
124 return True;
125 }
126
127
128 #endif /* __DRD_VC_H */
129