folly/test/DeterministicSchedule.cpp

   1 /*
   2  * Copyright 2015 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, unsigned* node, void* unused) {
 143   if (!tls_threadId && tls_sched) {
 144     beforeSharedAccess();
 145     tls_threadId = tls_sched->nextThreadId_++;
 146     afterSharedAccess();
 147   }
 148   if (cpu) {
 149     *cpu = tls_threadId;
 150   }
 151   if (node) {
 152     *node = tls_threadId;
 153   }
 154   return 0;
 155 }
 156
 157 sem_t* DeterministicSchedule::beforeThreadCreate() {
 158   sem_t* s = new sem_t;
 159   sem_init(s, 0, 0);
 160   beforeSharedAccess();
 161   sems_.push_back(s);
 162   afterSharedAccess();
 163   return s;
 164 }
 165
 166 void DeterministicSchedule::afterThreadCreate(sem_t* sem) {
 167   assert(tls_sem == nullptr);
 168   assert(tls_sched == nullptr);
 169   tls_sem = sem;
 170   tls_sched = this;
 171   bool started = false;
 172   while (!started) {
 173     beforeSharedAccess();
 174     if (active_.count(std::this_thread::get_id()) == 1) {
 175       started = true;
 176     }
 177     afterSharedAccess();
 178   }
 179 }
 180
 181 void DeterministicSchedule::beforeThreadExit() {
 182   assert(tls_sched == this);
 183   beforeSharedAccess();
 184   sems_.erase(std::find(sems_.begin(), sems_.end(), tls_sem));
 185   active_.erase(std::this_thread::get_id());
 186   if (sems_.size() > 0) {
 187     FOLLY_TEST_DSCHED_VLOG("exiting");
 188     afterSharedAccess();
 189   }
 190   sem_destroy(tls_sem);
 191   delete tls_sem;
 192   tls_sem = nullptr;
 193   tls_sched = nullptr;
 194 }
 195
 196 void DeterministicSchedule::join(std::thread& child) {
 197   auto sched = tls_sched;
 198   if (sched) {
 199     bool done = false;
 200     while (!done) {
 201       beforeSharedAccess();
 202       done = !sched->active_.count(child.get_id());
 203       if (done) {
 204         FOLLY_TEST_DSCHED_VLOG("joined " << std::hex << child.get_id());
 205       }
 206       afterSharedAccess();
 207     }
 208   }
 209   child.join();
 210 }
 211
 212 void DeterministicSchedule::post(sem_t* sem) {
 213   beforeSharedAccess();
 214   sem_post(sem);
 215   FOLLY_TEST_DSCHED_VLOG("sem_post(" << sem << ")");
 216   afterSharedAccess();
 217 }
 218
 219 bool DeterministicSchedule::tryWait(sem_t* sem) {
 220   beforeSharedAccess();
 221   int rv = sem_trywait(sem);
 222   int e = rv == 0 ? 0 : errno;
 223   FOLLY_TEST_DSCHED_VLOG("sem_trywait(" << sem << ") = " << rv
 224                                         << " errno=" << e);
 225   afterSharedAccess();
 226   if (rv == 0) {
 227     return true;
 228   } else {
 229     assert(e == EAGAIN);
 230     return false;
 231   }
 232 }
 233
 234 void DeterministicSchedule::wait(sem_t* sem) {
 235   while (!tryWait(sem)) {
 236     // we're not busy waiting because this is a deterministic schedule
 237   }
 238 }
 239 }
 240 }
 241
 242 namespace folly {
 243 namespace detail {
 244
 245 using namespace test;
 246 using namespace std::chrono;
 247
 248 template <>
 249 FutexResult Futex<DeterministicAtomic>::futexWaitImpl(
 250     uint32_t expected,
 251     time_point<system_clock>* absSystemTimeout,
 252     time_point<steady_clock>* absSteadyTimeout,
 253     uint32_t waitMask) {
 254   bool hasTimeout = absSystemTimeout != nullptr || absSteadyTimeout != nullptr;
 255   bool awoken = false;
 256   FutexResult result = FutexResult::AWOKEN;
 257
 258   DeterministicSchedule::beforeSharedAccess();
 259   FOLLY_TEST_DSCHED_VLOG(this << ".futexWait(" << std::hex << expected
 260                               << ", .., " << std::hex << waitMask
 261                               << ") beginning..");
 262   futexLock.lock();
 263   if (data == expected) {
 264     auto& queue = futexQueues[this];
 265     queue.emplace_back(waitMask, &awoken);
 266     auto ours = queue.end();
 267     ours--;
 268     while (!awoken) {
 269       futexLock.unlock();
 270       DeterministicSchedule::afterSharedAccess();
 271       DeterministicSchedule::beforeSharedAccess();
 272       futexLock.lock();
 273
 274       // Simulate spurious wake-ups, timeouts each time with
 275       // a 10% probability if we haven't been woken up already
 276       if (!awoken && hasTimeout &&
 277           DeterministicSchedule::getRandNumber(100) < 10) {
 278         assert(futexQueues.count(this) != 0 && &futexQueues[this] == &queue);
 279         queue.erase(ours);
 280         if (queue.empty()) {
 281           futexQueues.erase(this);
 282         }
 283         // Simulate ETIMEDOUT 90% of the time and other failures
 284         // remaining time
 285         result = DeterministicSchedule::getRandNumber(100) >= 10
 286                      ? FutexResult::TIMEDOUT
 287                      : FutexResult::INTERRUPTED;
 288         break;
 289       }
 290     }
 291   } else {
 292     result = FutexResult::VALUE_CHANGED;
 293   }
 294   futexLock.unlock();
 295
 296   char const* resultStr = "?";
 297   switch (result) {
 298   case FutexResult::AWOKEN:
 299     resultStr = "AWOKEN";
 300     break;
 301   case FutexResult::TIMEDOUT:
 302     resultStr = "TIMEDOUT";
 303     break;
 304   case FutexResult::INTERRUPTED:
 305     resultStr = "INTERRUPTED";
 306     break;
 307   case FutexResult::VALUE_CHANGED:
 308     resultStr = "VALUE_CHANGED";
 309     break;
 310   }
 311   FOLLY_TEST_DSCHED_VLOG(this << ".futexWait(" << std::hex << expected
 312                               << ", .., " << std::hex << waitMask << ") -> "
 313                               << resultStr);
 314   DeterministicSchedule::afterSharedAccess();
 315   return result;
 316 }
 317
 318 template <>
 319 int Futex<DeterministicAtomic>::futexWake(int count, uint32_t wakeMask) {
 320   int rv = 0;
 321   DeterministicSchedule::beforeSharedAccess();
 322   futexLock.lock();
 323   if (futexQueues.count(this) > 0) {
 324     auto& queue = futexQueues[this];
 325     auto iter = queue.begin();
 326     while (iter != queue.end() && rv < count) {
 327       auto cur = iter++;
 328       if ((cur->first & wakeMask) != 0) {
 329         *(cur->second) = true;
 330         rv++;
 331         queue.erase(cur);
 332       }
 333     }
 334     if (queue.empty()) {
 335       futexQueues.erase(this);
 336     }
 337   }
 338   futexLock.unlock();
 339   FOLLY_TEST_DSCHED_VLOG(this << ".futexWake(" << count << ", " << std::hex
 340                               << wakeMask << ") -> " << rv);
 341   DeterministicSchedule::afterSharedAccess();
 342   return rv;
 343 }
 344
 345 template <>
 346 CacheLocality const& CacheLocality::system<test::DeterministicAtomic>() {
 347   static CacheLocality cache(CacheLocality::uniform(16));
 348   return cache;
 349 }
 350
 351 template <>
 352 const AccessSpreader<test::DeterministicAtomic>
 353     AccessSpreader<test::DeterministicAtomic>::stripeByCore(
 354         CacheLocality::system<>().numCachesByLevel.front());
 355
 356 template <>
 357 const AccessSpreader<test::DeterministicAtomic>
 358     AccessSpreader<test::DeterministicAtomic>::stripeByChip(
 359         CacheLocality::system<>().numCachesByLevel.back());
 360
 361 template <>
 362 AccessSpreaderArray<test::DeterministicAtomic, 128>
 363     AccessSpreaderArray<test::DeterministicAtomic, 128>::sharedInstance = {};
 364
 365 template <>
 366 Getcpu::Func AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(
 367     size_t numStripes) {
 368   return &DeterministicSchedule::getcpu;
 369 }
 370 }
 371 }