1/*
2  This file is part of drd, a thread error detector.
3
4  Copyright (C) 2006-2012 Bart Van Assche <bvanassche@acm.org>.
5
6  This program is free software; you can redistribute it and/or
7  modify it under the terms of the GNU General Public License as
8  published by the Free Software Foundation; either version 2 of the
9  License, or (at your option) any later version.
10
11  This program is distributed in the hope that it will be useful, but
12  WITHOUT ANY WARRANTY; without even the implied warranty of
13  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14  General Public License for more details.
15
16  You should have received a copy of the GNU General Public License
17  along with this program; if not, write to the Free Software
18  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19  02111-1307, USA.
20
21  The GNU General Public License is contained in the file COPYING.
22*/
23
24
25#ifndef __DRD_VC_H
26#define __DRD_VC_H
27
28
29/*
30 * DRD vector clock implementation:
31 * - One counter per thread.
32 * - A vector clock is implemented as multiple pairs of (thread id, counter).
33 * - Pairs are stored in an array sorted by thread id.
34 *
35 * Semantics:
36 * - Each time a thread performs an action that implies an ordering between
37 *   intra-thread events, the counter of that thread is incremented.
38 * - Vector clocks are compared by comparing all counters of all threads.
39 * - When a thread synchronization action is performed that guarantees that
40 *   new actions of the current thread are executed after the actions of the
41 *   other thread, the vector clock of the synchronization object and the
42 *   current thread are combined (by taking the component-wise maximum).
43 * - A vector clock is incremented during actions such as
44 *   pthread_create(), pthread_mutex_unlock(), sem_post(). (Actions where
45 *   an inter-thread ordering "arrow" starts).
46 */
47
48
49#include "pub_tool_basics.h"     /* Addr, SizeT */
50#include "drd_basics.h"          /* DrdThreadId */
51#include "pub_tool_libcassert.h" /* tl_assert() */
52
53
54#define VC_PREALLOCATED 8
55
56
57/** Vector clock element. */
58typedef struct
59{
60   DrdThreadId threadid;
61   UInt        count;
62} VCElem;
63
64typedef struct
65{
66   unsigned capacity; /**< number of elements allocated for array vc. */
67   unsigned size;     /**< number of elements used of array vc. */
68   VCElem*  vc;       /**< vector clock elements. */
69   VCElem   preallocated[VC_PREALLOCATED];
70} VectorClock;
71
72
73void DRD_(vc_init)(VectorClock* const vc,
74                   const VCElem* const vcelem,
75                   const unsigned size);
76void DRD_(vc_cleanup)(VectorClock* const vc);
77void DRD_(vc_copy)(VectorClock* const new, const VectorClock* const rhs);
78void DRD_(vc_assign)(VectorClock* const lhs, const VectorClock* const rhs);
79void DRD_(vc_increment)(VectorClock* const vc, DrdThreadId const tid);
80static __inline__
81Bool DRD_(vc_lte)(const VectorClock* const vc1,
82                  const VectorClock* const vc2);
83Bool DRD_(vc_ordered)(const VectorClock* const vc1,
84                      const VectorClock* const vc2);
85void DRD_(vc_min)(VectorClock* const result,
86                  const VectorClock* const rhs);
87void DRD_(vc_combine)(VectorClock* const result,
88                      const VectorClock* const rhs);
89void DRD_(vc_print)(const VectorClock* const vc);
90char* DRD_(vc_aprint)(const VectorClock* const vc);
91void DRD_(vc_check)(const VectorClock* const vc);
92void DRD_(vc_test)(void);
93
94
95
96/**
97 * @return True if all thread id's that are present in vc1 also exist in
98 *    vc2, and if additionally all corresponding counters in v2 are higher or
99 *    equal.
100 */
101static __inline__
102Bool DRD_(vc_lte)(const VectorClock* const vc1, const VectorClock* const vc2)
103{
104   unsigned i;
105   unsigned j = 0;
106
107   for (i = 0; i < vc1->size; i++)
108   {
109      while (j < vc2->size && vc2->vc[j].threadid < vc1->vc[i].threadid)
110         j++;
111      if (j >= vc2->size || vc2->vc[j].threadid > vc1->vc[i].threadid)
112         return False;
113#ifdef ENABLE_DRD_CONSISTENCY_CHECKS
114      /*
115       * This assert statement has been commented out because of performance
116       * reasons.
117       */
118      tl_assert(j < vc2->size && vc2->vc[j].threadid == vc1->vc[i].threadid);
119#endif
120      if (vc1->vc[i].count > vc2->vc[j].count)
121         return False;
122   }
123   return True;
124}
125
126
127#endif /* __DRD_VC_H */
128