1 /*
2   This file is part of drd, a thread error detector.
3 
4   Copyright (C) 2006-2017 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 #include "drd_error.h"
26 #include "drd_segment.h"
27 #include "drd_thread.h"
28 #include "pub_tool_basics.h"      // Addr, SizeT
29 #include "pub_tool_libcassert.h"  // tl_assert()
30 #include "pub_tool_libcbase.h"    // VG_(strlen)()
31 #include "pub_tool_libcprint.h"   // VG_(printf)()
32 #include "pub_tool_machine.h"     // VG_(get_SP)()
33 #include "pub_tool_mallocfree.h"  // VG_(malloc)(), VG_(free)()
34 #include "pub_tool_threadstate.h" // VG_INVALID_THREADID
35 
36 
37 /* Global variables. */
38 
39 Segment* DRD_(g_sg_list);
40 
41 
42 /* Local variables. */
43 
44 static ULong s_segment_merge_count;
45 static ULong s_segments_created_count;
46 static ULong s_segments_alive_count;
47 static ULong s_max_segments_alive_count;
48 static Bool s_trace_segment;
49 
50 
51 /* Function definitions. */
52 
53 /**
54  * Initialize the memory 'sg' points at.
55  *
56  * @note The creator and created thread ID's may be equal.
57  * @note This function copies the vector clock of thread 'creator', a technique
58  *   also known as clock snooping. This will only work reliably if the thread
59  *   that called pthread_create() waits until the created thread has copied
60  *   the vector clock.
61  */
sg_init(Segment * const sg,const DrdThreadId creator,const DrdThreadId created)62 static void sg_init(Segment* const sg,
63                     const DrdThreadId creator,
64                     const DrdThreadId created)
65 {
66    Segment* creator_sg;
67    ThreadId vg_created = DRD_(DrdThreadIdToVgThreadId)(created);
68 
69    tl_assert(sg);
70    tl_assert(creator == DRD_INVALID_THREADID
71              || DRD_(IsValidDrdThreadId)(creator));
72 
73    creator_sg = (creator != DRD_INVALID_THREADID
74                  ? DRD_(thread_get_segment)(creator) : 0);
75 
76    sg->g_next = NULL;
77    sg->g_prev = NULL;
78    sg->thr_next = NULL;
79    sg->thr_prev = NULL;
80    sg->tid = created;
81    sg->refcnt = 1;
82 
83    if (vg_created != VG_INVALID_THREADID && VG_(get_SP)(vg_created) != 0)
84       sg->stacktrace = VG_(record_ExeContext)(vg_created, 0);
85    else
86       sg->stacktrace = 0;
87 
88    if (creator_sg)
89       DRD_(vc_copy)(&sg->vc, &creator_sg->vc);
90    else
91       DRD_(vc_init)(&sg->vc, 0, 0);
92    DRD_(vc_increment)(&sg->vc, created);
93    DRD_(bm_init)(&sg->bm);
94 
95    if (s_trace_segment)
96    {
97       HChar* vc;
98 
99       vc = DRD_(vc_aprint)(&sg->vc);
100       VG_(message)(Vg_DebugMsg, "New segment for thread %u with vc %s\n",
101                    created, vc);
102       VG_(free)(vc);
103    }
104 }
105 
106 /** Deallocate the memory that was allocated by sg_init(). */
DRD_(sg_cleanup)107 static void DRD_(sg_cleanup)(Segment* const sg)
108 {
109    tl_assert(sg);
110    tl_assert(sg->refcnt == 0);
111 
112    DRD_(vc_cleanup)(&sg->vc);
113    DRD_(bm_cleanup)(&sg->bm);
114 }
115 
116 /** Allocate and initialize a new segment. */
DRD_(sg_new)117 Segment* DRD_(sg_new)(const DrdThreadId creator, const DrdThreadId created)
118 {
119    Segment* sg;
120 
121    s_segments_created_count++;
122    s_segments_alive_count++;
123    if (s_max_segments_alive_count < s_segments_alive_count)
124       s_max_segments_alive_count = s_segments_alive_count;
125 
126    sg = VG_(malloc)("drd.segment.sn.1", sizeof(*sg));
127    sg_init(sg, creator, created);
128    if (DRD_(g_sg_list)) {
129       DRD_(g_sg_list)->g_prev = sg;
130       sg->g_next = DRD_(g_sg_list);
131    }
132    DRD_(g_sg_list) = sg;
133    return sg;
134 }
135 
DRD_(sg_delete)136 static void DRD_(sg_delete)(Segment* const sg)
137 {
138    if (DRD_(sg_get_trace)())
139    {
140       HChar* vc;
141 
142       vc = DRD_(vc_aprint)(&sg->vc);
143       VG_(message)(Vg_DebugMsg, "Discarding the segment with vector clock %s\n",
144                    vc);
145       VG_(free)(vc);
146    }
147 
148    s_segments_alive_count--;
149 
150    tl_assert(sg);
151    if (sg->g_next)
152       sg->g_next->g_prev = sg->g_prev;
153    if (sg->g_prev)
154       sg->g_prev->g_next = sg->g_next;
155    else
156       DRD_(g_sg_list) = sg->g_next;
157    DRD_(sg_cleanup)(sg);
158    VG_(free)(sg);
159 }
160 
161 /** Increment the reference count of the specified segment. */
DRD_(sg_get)162 Segment* DRD_(sg_get)(Segment* const sg)
163 {
164    tl_assert(sg);
165 
166    sg->refcnt++;
167    return sg;
168 }
169 
170 /**
171  * Decrement the reference count of the specified segment and deallocate the
172  * segment if the reference count became zero.
173  */
DRD_(sg_put)174 void DRD_(sg_put)(Segment* const sg)
175 {
176    if (sg == 0)
177       return;
178 
179    if (s_trace_segment)
180    {
181       HChar* vc;
182 
183       vc = DRD_(vc_aprint)(&sg->vc);
184       VG_(message)(Vg_DebugMsg,
185                    "Decrementing segment reference count %d -> %d with vc %s\n",
186                    sg->refcnt, sg->refcnt - 1, vc);
187       VG_(free)(vc);
188    }
189 
190    tl_assert(sg->refcnt >= 1);
191 
192    if (--sg->refcnt == 0)
193    {
194       DRD_(sg_delete)(sg);
195    }
196 }
197 
198 /** Merge sg1 and sg2 into sg1. */
DRD_(sg_merge)199 void DRD_(sg_merge)(Segment* const sg1, Segment* const sg2)
200 {
201    tl_assert(sg1);
202    tl_assert(sg1->refcnt == 1);
203    tl_assert(sg2);
204    tl_assert(sg2->refcnt == 1);
205 
206    if (s_trace_segment)
207    {
208       HChar *vc1, *vc2;
209 
210       vc1 = DRD_(vc_aprint)(&sg1->vc);
211       vc2 = DRD_(vc_aprint)(&sg2->vc);
212 
213       VG_(message)(Vg_DebugMsg,
214 		   "Merging segments with vector clocks %s and %s\n", vc1, vc2);
215       VG_(free)(vc1);
216       VG_(free)(vc2);
217    }
218 
219    s_segment_merge_count++;
220 
221    // Keep sg1->stacktrace.
222    // Keep sg1->vc.
223    // Merge sg2->bm into sg1->bm.
224    DRD_(bm_merge2)(&sg1->bm, &sg2->bm);
225 }
226 
227 /** Print the vector clock and the bitmap of the specified segment. */
DRD_(sg_print)228 void DRD_(sg_print)(Segment* const sg)
229 {
230    tl_assert(sg);
231    VG_(printf)("vc: ");
232    DRD_(vc_print)(&sg->vc);
233    VG_(printf)("\n");
234    DRD_(bm_print)(&sg->bm);
235 }
236 
237 /** Query whether segment tracing has been enabled. */
DRD_(sg_get_trace)238 Bool DRD_(sg_get_trace)(void)
239 {
240    return s_trace_segment;
241 }
242 
243 /** Enable or disable segment tracing. */
DRD_(sg_set_trace)244 void DRD_(sg_set_trace)(Bool const trace_segment)
245 {
246    tl_assert(trace_segment == False || trace_segment == True);
247    s_trace_segment = trace_segment;
248 }
249 
DRD_(sg_get_segments_created_count)250 ULong DRD_(sg_get_segments_created_count)(void)
251 {
252    return s_segments_created_count;
253 }
254 
DRD_(sg_get_segments_alive_count)255 ULong DRD_(sg_get_segments_alive_count)(void)
256 {
257    return s_segments_alive_count;
258 }
259 
DRD_(sg_get_max_segments_alive_count)260 ULong DRD_(sg_get_max_segments_alive_count)(void)
261 {
262    return s_max_segments_alive_count;
263 }
264 
DRD_(sg_get_segment_merge_count)265 ULong DRD_(sg_get_segment_merge_count)(void)
266 {
267    return s_segment_merge_count;
268 }
269