1//===-- sanitizer_deadlock_detector2.cpp ----------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Deadlock detector implementation based on adjacency lists.
10//
11//===----------------------------------------------------------------------===//
12
13#include "sanitizer_deadlock_detector_interface.h"
14#include "sanitizer_common.h"
15#include "sanitizer_allocator_internal.h"
16#include "sanitizer_placement_new.h"
17#include "sanitizer_mutex.h"
18
19#if SANITIZER_DEADLOCK_DETECTOR_VERSION == 2
20
21namespace __sanitizer {
22
23const int kMaxNesting = 64;
24const u32 kNoId = -1;
25const u32 kEndId = -2;
26const int kMaxLink = 8;
27const int kL1Size = 1024;
28const int kL2Size = 1024;
29const int kMaxMutex = kL1Size * kL2Size;
30
31struct Id {
32  u32 id;
33  u32 seq;
34
35  explicit Id(u32 id = 0, u32 seq = 0)
36      : id(id)
37      , seq(seq) {
38  }
39};
40
41struct Link {
42  u32 id;
43  u32 seq;
44  u32 tid;
45  u32 stk0;
46  u32 stk1;
47
48  explicit Link(u32 id = 0, u32 seq = 0, u32 tid = 0, u32 s0 = 0, u32 s1 = 0)
49      : id(id)
50      , seq(seq)
51      , tid(tid)
52      , stk0(s0)
53      , stk1(s1) {
54  }
55};
56
57struct DDPhysicalThread {
58  DDReport rep;
59  bool report_pending;
60  bool visited[kMaxMutex];
61  Link pending[kMaxMutex];
62  Link path[kMaxMutex];
63};
64
65struct ThreadMutex {
66  u32 id;
67  u32 stk;
68};
69
70struct DDLogicalThread {
71  u64         ctx;
72  ThreadMutex locked[kMaxNesting];
73  int         nlocked;
74};
75
76struct MutexState {
77  StaticSpinMutex mtx;
78  u32 seq;
79  int nlink;
80  Link link[kMaxLink];
81};
82
83struct DD final : public DDetector {
84  explicit DD(const DDFlags *flags);
85
86  DDPhysicalThread* CreatePhysicalThread();
87  void DestroyPhysicalThread(DDPhysicalThread *pt);
88
89  DDLogicalThread* CreateLogicalThread(u64 ctx);
90  void DestroyLogicalThread(DDLogicalThread *lt);
91
92  void MutexInit(DDCallback *cb, DDMutex *m);
93  void MutexBeforeLock(DDCallback *cb, DDMutex *m, bool wlock);
94  void MutexAfterLock(DDCallback *cb, DDMutex *m, bool wlock,
95      bool trylock);
96  void MutexBeforeUnlock(DDCallback *cb, DDMutex *m, bool wlock);
97  void MutexDestroy(DDCallback *cb, DDMutex *m);
98
99  DDReport *GetReport(DDCallback *cb);
100
101  void CycleCheck(DDPhysicalThread *pt, DDLogicalThread *lt, DDMutex *mtx);
102  void Report(DDPhysicalThread *pt, DDLogicalThread *lt, int npath);
103  u32 allocateId(DDCallback *cb);
104  MutexState *getMutex(u32 id);
105  u32 getMutexId(MutexState *m);
106
107  DDFlags flags;
108
109  MutexState *mutex[kL1Size];
110
111  SpinMutex mtx;
112  InternalMmapVector<u32> free_id;
113  int id_gen = 0;
114};
115
116DDetector *DDetector::Create(const DDFlags *flags) {
117  (void)flags;
118  void *mem = MmapOrDie(sizeof(DD), "deadlock detector");
119  return new(mem) DD(flags);
120}
121
122DD::DD(const DDFlags *flags) : flags(*flags) { free_id.reserve(1024); }
123
124DDPhysicalThread* DD::CreatePhysicalThread() {
125  DDPhysicalThread *pt = (DDPhysicalThread*)MmapOrDie(sizeof(DDPhysicalThread),
126      "deadlock detector (physical thread)");
127  return pt;
128}
129
130void DD::DestroyPhysicalThread(DDPhysicalThread *pt) {
131  pt->~DDPhysicalThread();
132  UnmapOrDie(pt, sizeof(DDPhysicalThread));
133}
134
135DDLogicalThread* DD::CreateLogicalThread(u64 ctx) {
136  DDLogicalThread *lt = (DDLogicalThread*)InternalAlloc(
137      sizeof(DDLogicalThread));
138  lt->ctx = ctx;
139  lt->nlocked = 0;
140  return lt;
141}
142
143void DD::DestroyLogicalThread(DDLogicalThread *lt) {
144  lt->~DDLogicalThread();
145  InternalFree(lt);
146}
147
148void DD::MutexInit(DDCallback *cb, DDMutex *m) {
149  VPrintf(2, "#%llu: DD::MutexInit(%p)\n", cb->lt->ctx, m);
150  m->id = kNoId;
151  m->recursion = 0;
152  atomic_store(&m->owner, 0, memory_order_relaxed);
153}
154
155MutexState *DD::getMutex(u32 id) { return &mutex[id / kL2Size][id % kL2Size]; }
156
157u32 DD::getMutexId(MutexState *m) {
158  for (int i = 0; i < kL1Size; i++) {
159    MutexState *tab = mutex[i];
160    if (tab == 0)
161      break;
162    if (m >= tab && m < tab + kL2Size)
163      return i * kL2Size + (m - tab);
164  }
165  return -1;
166}
167
168u32 DD::allocateId(DDCallback *cb) {
169  u32 id = -1;
170  SpinMutexLock l(&mtx);
171  if (free_id.size() > 0) {
172    id = free_id.back();
173    free_id.pop_back();
174  } else {
175    CHECK_LT(id_gen, kMaxMutex);
176    if ((id_gen % kL2Size) == 0) {
177      mutex[id_gen / kL2Size] = (MutexState *)MmapOrDie(
178          kL2Size * sizeof(MutexState), "deadlock detector (mutex table)");
179    }
180    id = id_gen++;
181  }
182  CHECK_LE(id, kMaxMutex);
183  VPrintf(3, "#%llu: DD::allocateId assign id %d\n", cb->lt->ctx, id);
184  return id;
185}
186
187void DD::MutexBeforeLock(DDCallback *cb, DDMutex *m, bool wlock) {
188  VPrintf(2, "#%llu: DD::MutexBeforeLock(%p, wlock=%d) nlocked=%d\n",
189      cb->lt->ctx, m, wlock, cb->lt->nlocked);
190  DDPhysicalThread *pt = cb->pt;
191  DDLogicalThread *lt = cb->lt;
192
193  uptr owner = atomic_load(&m->owner, memory_order_relaxed);
194  if (owner == (uptr)cb->lt) {
195    VPrintf(3, "#%llu: DD::MutexBeforeLock recursive\n",
196        cb->lt->ctx);
197    return;
198  }
199
200  CHECK_LE(lt->nlocked, kMaxNesting);
201
202  // FIXME(dvyukov): don't allocate id if lt->nlocked == 0?
203  if (m->id == kNoId)
204    m->id = allocateId(cb);
205
206  ThreadMutex *tm = &lt->locked[lt->nlocked++];
207  tm->id = m->id;
208  if (flags.second_deadlock_stack)
209    tm->stk = cb->Unwind();
210  if (lt->nlocked == 1) {
211    VPrintf(3, "#%llu: DD::MutexBeforeLock first mutex\n",
212        cb->lt->ctx);
213    return;
214  }
215
216  bool added = false;
217  MutexState *mtx = getMutex(m->id);
218  for (int i = 0; i < lt->nlocked - 1; i++) {
219    u32 id1 = lt->locked[i].id;
220    u32 stk1 = lt->locked[i].stk;
221    MutexState *mtx1 = getMutex(id1);
222    SpinMutexLock l(&mtx1->mtx);
223    if (mtx1->nlink == kMaxLink) {
224      // FIXME(dvyukov): check stale links
225      continue;
226    }
227    int li = 0;
228    for (; li < mtx1->nlink; li++) {
229      Link *link = &mtx1->link[li];
230      if (link->id == m->id) {
231        if (link->seq != mtx->seq) {
232          link->seq = mtx->seq;
233          link->tid = lt->ctx;
234          link->stk0 = stk1;
235          link->stk1 = cb->Unwind();
236          added = true;
237          VPrintf(3, "#%llu: DD::MutexBeforeLock added %d->%d link\n",
238              cb->lt->ctx, getMutexId(mtx1), m->id);
239        }
240        break;
241      }
242    }
243    if (li == mtx1->nlink) {
244      // FIXME(dvyukov): check stale links
245      Link *link = &mtx1->link[mtx1->nlink++];
246      link->id = m->id;
247      link->seq = mtx->seq;
248      link->tid = lt->ctx;
249      link->stk0 = stk1;
250      link->stk1 = cb->Unwind();
251      added = true;
252      VPrintf(3, "#%llu: DD::MutexBeforeLock added %d->%d link\n",
253          cb->lt->ctx, getMutexId(mtx1), m->id);
254    }
255  }
256
257  if (!added || mtx->nlink == 0) {
258    VPrintf(3, "#%llu: DD::MutexBeforeLock don't check\n",
259        cb->lt->ctx);
260    return;
261  }
262
263  CycleCheck(pt, lt, m);
264}
265
266void DD::MutexAfterLock(DDCallback *cb, DDMutex *m, bool wlock,
267    bool trylock) {
268  VPrintf(2, "#%llu: DD::MutexAfterLock(%p, wlock=%d, try=%d) nlocked=%d\n",
269      cb->lt->ctx, m, wlock, trylock, cb->lt->nlocked);
270  DDLogicalThread *lt = cb->lt;
271
272  uptr owner = atomic_load(&m->owner, memory_order_relaxed);
273  if (owner == (uptr)cb->lt) {
274    VPrintf(3, "#%llu: DD::MutexAfterLock recursive\n", cb->lt->ctx);
275    CHECK(wlock);
276    m->recursion++;
277    return;
278  }
279  CHECK_EQ(owner, 0);
280  if (wlock) {
281    VPrintf(3, "#%llu: DD::MutexAfterLock set owner\n", cb->lt->ctx);
282    CHECK_EQ(m->recursion, 0);
283    m->recursion = 1;
284    atomic_store(&m->owner, (uptr)cb->lt, memory_order_relaxed);
285  }
286
287  if (!trylock)
288    return;
289
290  CHECK_LE(lt->nlocked, kMaxNesting);
291  if (m->id == kNoId)
292    m->id = allocateId(cb);
293  ThreadMutex *tm = &lt->locked[lt->nlocked++];
294  tm->id = m->id;
295  if (flags.second_deadlock_stack)
296    tm->stk = cb->Unwind();
297}
298
299void DD::MutexBeforeUnlock(DDCallback *cb, DDMutex *m, bool wlock) {
300  VPrintf(2, "#%llu: DD::MutexBeforeUnlock(%p, wlock=%d) nlocked=%d\n",
301      cb->lt->ctx, m, wlock, cb->lt->nlocked);
302  DDLogicalThread *lt = cb->lt;
303
304  uptr owner = atomic_load(&m->owner, memory_order_relaxed);
305  if (owner == (uptr)cb->lt) {
306    VPrintf(3, "#%llu: DD::MutexBeforeUnlock recursive\n", cb->lt->ctx);
307    if (--m->recursion > 0)
308      return;
309    VPrintf(3, "#%llu: DD::MutexBeforeUnlock reset owner\n", cb->lt->ctx);
310    atomic_store(&m->owner, 0, memory_order_relaxed);
311  }
312  CHECK_NE(m->id, kNoId);
313  int last = lt->nlocked - 1;
314  for (int i = last; i >= 0; i--) {
315    if (cb->lt->locked[i].id == m->id) {
316      lt->locked[i] = lt->locked[last];
317      lt->nlocked--;
318      break;
319    }
320  }
321}
322
323void DD::MutexDestroy(DDCallback *cb, DDMutex *m) {
324  VPrintf(2, "#%llu: DD::MutexDestroy(%p)\n",
325      cb->lt->ctx, m);
326  DDLogicalThread *lt = cb->lt;
327
328  if (m->id == kNoId)
329    return;
330
331  // Remove the mutex from lt->locked if there.
332  int last = lt->nlocked - 1;
333  for (int i = last; i >= 0; i--) {
334    if (lt->locked[i].id == m->id) {
335      lt->locked[i] = lt->locked[last];
336      lt->nlocked--;
337      break;
338    }
339  }
340
341  // Clear and invalidate the mutex descriptor.
342  {
343    MutexState *mtx = getMutex(m->id);
344    SpinMutexLock l(&mtx->mtx);
345    mtx->seq++;
346    mtx->nlink = 0;
347  }
348
349  // Return id to cache.
350  {
351    SpinMutexLock l(&mtx);
352    free_id.push_back(m->id);
353  }
354}
355
356void DD::CycleCheck(DDPhysicalThread *pt, DDLogicalThread *lt,
357    DDMutex *m) {
358  internal_memset(pt->visited, 0, sizeof(pt->visited));
359  int npath = 0;
360  int npending = 0;
361  {
362    MutexState *mtx = getMutex(m->id);
363    SpinMutexLock l(&mtx->mtx);
364    for (int li = 0; li < mtx->nlink; li++)
365      pt->pending[npending++] = mtx->link[li];
366  }
367  while (npending > 0) {
368    Link link = pt->pending[--npending];
369    if (link.id == kEndId) {
370      npath--;
371      continue;
372    }
373    if (pt->visited[link.id])
374      continue;
375    MutexState *mtx1 = getMutex(link.id);
376    SpinMutexLock l(&mtx1->mtx);
377    if (mtx1->seq != link.seq)
378      continue;
379    pt->visited[link.id] = true;
380    if (mtx1->nlink == 0)
381      continue;
382    pt->path[npath++] = link;
383    pt->pending[npending++] = Link(kEndId);
384    if (link.id == m->id)
385      return Report(pt, lt, npath);  // Bingo!
386    for (int li = 0; li < mtx1->nlink; li++) {
387      Link *link1 = &mtx1->link[li];
388      // MutexState *mtx2 = getMutex(link->id);
389      // FIXME(dvyukov): fast seq check
390      // FIXME(dvyukov): fast nlink != 0 check
391      // FIXME(dvyukov): fast pending check?
392      // FIXME(dvyukov): npending can be larger than kMaxMutex
393      pt->pending[npending++] = *link1;
394    }
395  }
396}
397
398void DD::Report(DDPhysicalThread *pt, DDLogicalThread *lt, int npath) {
399  DDReport *rep = &pt->rep;
400  rep->n = npath;
401  for (int i = 0; i < npath; i++) {
402    Link *link = &pt->path[i];
403    Link *link0 = &pt->path[i ? i - 1 : npath - 1];
404    rep->loop[i].thr_ctx = link->tid;
405    rep->loop[i].mtx_ctx0 = link0->id;
406    rep->loop[i].mtx_ctx1 = link->id;
407    rep->loop[i].stk[0] = flags.second_deadlock_stack ? link->stk0 : 0;
408    rep->loop[i].stk[1] = link->stk1;
409  }
410  pt->report_pending = true;
411}
412
413DDReport *DD::GetReport(DDCallback *cb) {
414  if (!cb->pt->report_pending)
415    return 0;
416  cb->pt->report_pending = false;
417  return &cb->pt->rep;
418}
419
420}  // namespace __sanitizer
421#endif  // #if SANITIZER_DEADLOCK_DETECTOR_VERSION == 2
422