folly/test/DeterministicSchedule.cpp

   1 /*
   2  * Copyright 2016 Facebook, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *   http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <folly/test/DeterministicSchedule.h>
  18 #include <algorithm>
  19 #include <list>
  20 #include <mutex>
  21 #include <random>
  22 #include <utility>
  23 #include <unordered_map>
  24 #include <assert.h>
  25
  26 namespace folly {
  27 namespace test {
  28
  29 FOLLY_TLS sem_t* DeterministicSchedule::tls_sem;
  30 FOLLY_TLS DeterministicSchedule* DeterministicSchedule::tls_sched;
  31 FOLLY_TLS unsigned DeterministicSchedule::tls_threadId;
  32
  33 // access is protected by futexLock
  34 static std::unordered_map<detail::Futex<DeterministicAtomic>*,
  35                           std::list<std::pair<uint32_t, bool*>>> futexQueues;
  36
  37 static std::mutex futexLock;
  38
  39 DeterministicSchedule::DeterministicSchedule(
  40     const std::function<int(int)>& scheduler)
  41     : scheduler_(scheduler), nextThreadId_(1) {
  42   assert(tls_sem == nullptr);
  43   assert(tls_sched == nullptr);
  44
  45   tls_sem = new sem_t;
  46   sem_init(tls_sem, 0, 1);
  47   sems_.push_back(tls_sem);
  48
  49   tls_sched = this;
  50 }
  51
  52 DeterministicSchedule::~DeterministicSchedule() {
  53   assert(tls_sched == this);
  54   assert(sems_.size() == 1);
  55   assert(sems_[0] == tls_sem);
  56   beforeThreadExit();
  57 }
  58
  59 std::function<int(int)> DeterministicSchedule::uniform(long seed) {
  60   auto rand = std::make_shared<std::ranlux48>(seed);
  61   return [rand](size_t numActive) {
  62     auto dist = std::uniform_int_distribution<int>(0, numActive - 1);
  63     return dist(*rand);
  64   };
  65 }
  66
  67 struct UniformSubset {
  68   UniformSubset(long seed, int subsetSize, int stepsBetweenSelect)
  69       : uniform_(DeterministicSchedule::uniform(seed)),
  70         subsetSize_(subsetSize),
  71         stepsBetweenSelect_(stepsBetweenSelect),
  72         stepsLeft_(0) {}
  73
  74   size_t operator()(size_t numActive) {
  75     adjustPermSize(numActive);
  76     if (stepsLeft_-- == 0) {
  77       stepsLeft_ = stepsBetweenSelect_ - 1;
  78       shufflePrefix();
  79     }
  80     return perm_[uniform_(std::min(numActive, subsetSize_))];
  81   }
  82
  83  private:
  84   std::function<int(int)> uniform_;
  85   const size_t subsetSize_;
  86   const int stepsBetweenSelect_;
  87
  88   int stepsLeft_;
  89   // only the first subsetSize_ is properly randomized
  90   std::vector<int> perm_;
  91
  92   void adjustPermSize(size_t numActive) {
  93     if (perm_.size() > numActive) {
  94       perm_.erase(std::remove_if(perm_.begin(), perm_.end(), [=](size_t x) {
  95         return x >= numActive;
  96       }), perm_.end());
  97     } else {
  98       while (perm_.size() < numActive) {
  99         perm_.push_back(perm_.size());
 100       }
 101     }
 102     assert(perm_.size() == numActive);
 103   }
 104
 105   void shufflePrefix() {
 106     for (size_t i = 0; i < std::min(perm_.size() - 1, subsetSize_); ++i) {
 107       int j = uniform_(perm_.size() - i) + i;
 108       std::swap(perm_[i], perm_[j]);
 109     }
 110   }
 111 };
 112
 113 std::function<int(int)> DeterministicSchedule::uniformSubset(long seed,
 114                                                              int n,
 115                                                              int m) {
 116   auto gen = std::make_shared<UniformSubset>(seed, n, m);
 117   return [=](size_t numActive) { return (*gen)(numActive); };
 118 }
 119
 120 void DeterministicSchedule::beforeSharedAccess() {
 121   if (tls_sem) {
 122     sem_wait(tls_sem);
 123   }
 124 }
 125
 126 void DeterministicSchedule::afterSharedAccess() {
 127   auto sched = tls_sched;
 128   if (!sched) {
 129     return;
 130   }
 131
 132   sem_post(sched->sems_[sched->scheduler_(sched->sems_.size())]);
 133 }
 134
 135 int DeterministicSchedule::getRandNumber(int n) {
 136   if (tls_sched) {
 137     return tls_sched->scheduler_(n);
 138   }
 139   return std::rand() % n;
 140 }
 141
 142 int DeterministicSchedule::getcpu(unsigned* cpu,
 143                                   unsigned* node,
 144                                   void* /* unused */) {
 145   if (!tls_threadId && tls_sched) {
 146     beforeSharedAccess();
 147     tls_threadId = tls_sched->nextThreadId_++;
 148     afterSharedAccess();
 149   }
 150   if (cpu) {
 151     *cpu = tls_threadId;
 152   }
 153   if (node) {
 154     *node = tls_threadId;
 155   }
 156   return 0;
 157 }
 158
 159 sem_t* DeterministicSchedule::beforeThreadCreate() {
 160   sem_t* s = new sem_t;
 161   sem_init(s, 0, 0);
 162   beforeSharedAccess();
 163   sems_.push_back(s);
 164   afterSharedAccess();
 165   return s;
 166 }
 167
 168 void DeterministicSchedule::afterThreadCreate(sem_t* sem) {
 169   assert(tls_sem == nullptr);
 170   assert(tls_sched == nullptr);
 171   tls_sem = sem;
 172   tls_sched = this;
 173   bool started = false;
 174   while (!started) {
 175     beforeSharedAccess();
 176     if (active_.count(std::this_thread::get_id()) == 1) {
 177       started = true;
 178     }
 179     afterSharedAccess();
 180   }
 181 }
 182
 183 void DeterministicSchedule::beforeThreadExit() {
 184   assert(tls_sched == this);
 185   beforeSharedAccess();
 186   sems_.erase(std::find(sems_.begin(), sems_.end(), tls_sem));
 187   active_.erase(std::this_thread::get_id());
 188   if (sems_.size() > 0) {
 189     FOLLY_TEST_DSCHED_VLOG("exiting");
 190     afterSharedAccess();
 191   }
 192   sem_destroy(tls_sem);
 193   delete tls_sem;
 194   tls_sem = nullptr;
 195   tls_sched = nullptr;
 196 }
 197
 198 void DeterministicSchedule::join(std::thread& child) {
 199   auto sched = tls_sched;
 200   if (sched) {
 201     bool done = false;
 202     while (!done) {
 203       beforeSharedAccess();
 204       done = !sched->active_.count(child.get_id());
 205       if (done) {
 206         FOLLY_TEST_DSCHED_VLOG("joined " << std::hex << child.get_id());
 207       }
 208       afterSharedAccess();
 209     }
 210   }
 211   child.join();
 212 }
 213
 214 void DeterministicSchedule::post(sem_t* sem) {
 215   beforeSharedAccess();
 216   sem_post(sem);
 217   FOLLY_TEST_DSCHED_VLOG("sem_post(" << sem << ")");
 218   afterSharedAccess();
 219 }
 220
 221 bool DeterministicSchedule::tryWait(sem_t* sem) {
 222   beforeSharedAccess();
 223   int rv = sem_trywait(sem);
 224   int e = rv == 0 ? 0 : errno;
 225   FOLLY_TEST_DSCHED_VLOG("sem_trywait(" << sem << ") = " << rv
 226                                         << " errno=" << e);
 227   afterSharedAccess();
 228   if (rv == 0) {
 229     return true;
 230   } else {
 231     assert(e == EAGAIN);
 232     return false;
 233   }
 234 }
 235
 236 void DeterministicSchedule::wait(sem_t* sem) {
 237   while (!tryWait(sem)) {
 238     // we're not busy waiting because this is a deterministic schedule
 239   }
 240 }
 241 }
 242 }
 243
 244 namespace folly {
 245 namespace detail {
 246
 247 using namespace test;
 248 using namespace std::chrono;
 249
 250 template <>
 251 FutexResult Futex<DeterministicAtomic>::futexWaitImpl(
 252     uint32_t expected,
 253     time_point<system_clock>* absSystemTimeout,
 254     time_point<steady_clock>* absSteadyTimeout,
 255     uint32_t waitMask) {
 256   bool hasTimeout = absSystemTimeout != nullptr || absSteadyTimeout != nullptr;
 257   bool awoken = false;
 258   FutexResult result = FutexResult::AWOKEN;
 259
 260   DeterministicSchedule::beforeSharedAccess();
 261   FOLLY_TEST_DSCHED_VLOG(this << ".futexWait(" << std::hex << expected
 262                               << ", .., " << std::hex << waitMask
 263                               << ") beginning..");
 264   futexLock.lock();
 265   if (data == expected) {
 266     auto& queue = futexQueues[this];
 267     queue.emplace_back(waitMask, &awoken);
 268     auto ours = queue.end();
 269     ours--;
 270     while (!awoken) {
 271       futexLock.unlock();
 272       DeterministicSchedule::afterSharedAccess();
 273       DeterministicSchedule::beforeSharedAccess();
 274       futexLock.lock();
 275
 276       // Simulate spurious wake-ups, timeouts each time with
 277       // a 10% probability if we haven't been woken up already
 278       if (!awoken && hasTimeout &&
 279           DeterministicSchedule::getRandNumber(100) < 10) {
 280         assert(futexQueues.count(this) != 0 && &futexQueues[this] == &queue);
 281         queue.erase(ours);
 282         if (queue.empty()) {
 283           futexQueues.erase(this);
 284         }
 285         // Simulate ETIMEDOUT 90% of the time and other failures
 286         // remaining time
 287         result = DeterministicSchedule::getRandNumber(100) >= 10
 288                      ? FutexResult::TIMEDOUT
 289                      : FutexResult::INTERRUPTED;
 290         break;
 291       }
 292     }
 293   } else {
 294     result = FutexResult::VALUE_CHANGED;
 295   }
 296   futexLock.unlock();
 297
 298   char const* resultStr = "?";
 299   switch (result) {
 300   case FutexResult::AWOKEN:
 301     resultStr = "AWOKEN";
 302     break;
 303   case FutexResult::TIMEDOUT:
 304     resultStr = "TIMEDOUT";
 305     break;
 306   case FutexResult::INTERRUPTED:
 307     resultStr = "INTERRUPTED";
 308     break;
 309   case FutexResult::VALUE_CHANGED:
 310     resultStr = "VALUE_CHANGED";
 311     break;
 312   }
 313   FOLLY_TEST_DSCHED_VLOG(this << ".futexWait(" << std::hex << expected
 314                               << ", .., " << std::hex << waitMask << ") -> "
 315                               << resultStr);
 316   DeterministicSchedule::afterSharedAccess();
 317   return result;
 318 }
 319
 320 template <>
 321 int Futex<DeterministicAtomic>::futexWake(int count, uint32_t wakeMask) {
 322   int rv = 0;
 323   DeterministicSchedule::beforeSharedAccess();
 324   futexLock.lock();
 325   if (futexQueues.count(this) > 0) {
 326     auto& queue = futexQueues[this];
 327     auto iter = queue.begin();
 328     while (iter != queue.end() && rv < count) {
 329       auto cur = iter++;
 330       if ((cur->first & wakeMask) != 0) {
 331         *(cur->second) = true;
 332         rv++;
 333         queue.erase(cur);
 334       }
 335     }
 336     if (queue.empty()) {
 337       futexQueues.erase(this);
 338     }
 339   }
 340   futexLock.unlock();
 341   FOLLY_TEST_DSCHED_VLOG(this << ".futexWake(" << count << ", " << std::hex
 342                               << wakeMask << ") -> " << rv);
 343   DeterministicSchedule::afterSharedAccess();
 344   return rv;
 345 }
 346
 347 template <>
 348 CacheLocality const& CacheLocality::system<test::DeterministicAtomic>() {
 349   static CacheLocality cache(CacheLocality::uniform(16));
 350   return cache;
 351 }
 352
 353 template <>
 354 const AccessSpreader<test::DeterministicAtomic>
 355     AccessSpreader<test::DeterministicAtomic>::stripeByCore(
 356         CacheLocality::system<>().numCachesByLevel.front());
 357
 358 template <>
 359 const AccessSpreader<test::DeterministicAtomic>
 360     AccessSpreader<test::DeterministicAtomic>::stripeByChip(
 361         CacheLocality::system<>().numCachesByLevel.back());
 362
 363 template <>
 364 AccessSpreaderArray<test::DeterministicAtomic, 128>
 365     AccessSpreaderArray<test::DeterministicAtomic, 128>::sharedInstance = {};
 366
 367 template <>
 368 Getcpu::Func AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(
 369     size_t /* numStripes */) {
 370   return &DeterministicSchedule::getcpu;
 371 }
 372 }
 373 }