improvements to DeterministicSchedule

Summary: This diff isolates the CacheLocality back end for DeterministicSchedule
from one invocation to the next (the last one was deterministic
across the entire program but not per-DeterministicSchedule instance),
and makes it easy to do extensive tracing of memory accesses during
a deterministic test.  These changes were made while tracking down a
bug, but don't fix any bugs on their own (and in fact don't affect any
production code at all).

Reviewed By: @yfeldblum

Differential Revision: D1842390

folly/test/DeterministicSchedule.cpp

@@ -23,21 +23,22 @@
 #include <unordered_map>
 #include <assert.h>
 
-namespace folly { namespace test {
+namespace folly {
+namespace test {
 
 FOLLY_TLS sem_t* DeterministicSchedule::tls_sem;
 FOLLY_TLS DeterministicSchedule* DeterministicSchedule::tls_sched;
+FOLLY_TLS unsigned DeterministicSchedule::tls_threadId;
 
 // access is protected by futexLock
 static std::unordered_map<detail::Futex<DeterministicAtomic>*,
-                          std::list<std::pair<uint32_t,bool*>>> futexQueues;
+                          std::list<std::pair<uint32_t, bool*>>> futexQueues;
 
 static std::mutex futexLock;
 
 DeterministicSchedule::DeterministicSchedule(
     const std::function<int(int)>& scheduler)
-  : scheduler_(scheduler)
-{
+    : scheduler_(scheduler), nextThreadId_(1) {
   assert(tls_sem == nullptr);
   assert(tls_sched == nullptr);
 
@@ -55,8 +56,7 @@ DeterministicSchedule::~DeterministicSchedule() {
   beforeThreadExit();
 }
 
-std::function<int(int)>
-DeterministicSchedule::uniform(long seed) {
+std::function<int(int)> DeterministicSchedule::uniform(long seed) {
   auto rand = std::make_shared<std::ranlux48>(seed);
   return [rand](size_t numActive) {
     auto dist = std::uniform_int_distribution<int>(0, numActive - 1);
@@ -66,12 +66,10 @@ DeterministicSchedule::uniform(long seed) {
 
 struct UniformSubset {
   UniformSubset(long seed, int subsetSize, int stepsBetweenSelect)
-    : uniform_(DeterministicSchedule::uniform(seed))
-    , subsetSize_(subsetSize)
-    , stepsBetweenSelect_(stepsBetweenSelect)
-    , stepsLeft_(0)
-  {
-  }
+      : uniform_(DeterministicSchedule::uniform(seed)),
+        subsetSize_(subsetSize),
+        stepsBetweenSelect_(stepsBetweenSelect),
+        stepsLeft_(0) {}
 
   size_t operator()(size_t numActive) {
     adjustPermSize(numActive);
@@ -93,8 +91,9 @@ struct UniformSubset {
 
   void adjustPermSize(size_t numActive) {
     if (perm_.size() > numActive) {
-      perm_.erase(std::remove_if(perm_.begin(), perm_.end(),
-              [=](size_t x){ return x >= numActive; }), perm_.end());
+      perm_.erase(std::remove_if(perm_.begin(), perm_.end(), [=](size_t x) {
+        return x >= numActive;
+      }), perm_.end());
     } else {
       while (perm_.size() < numActive) {
         perm_.push_back(perm_.size());
@@ -111,21 +110,20 @@ struct UniformSubset {
   }
 };
 
-std::function<int(int)>
-DeterministicSchedule::uniformSubset(long seed, int n, int m) {
+std::function<int(int)> DeterministicSchedule::uniformSubset(long seed,
+                                                             int n,
+                                                             int m) {
   auto gen = std::make_shared<UniformSubset>(seed, n, m);
   return [=](size_t numActive) { return (*gen)(numActive); };
 }
 
-void
-DeterministicSchedule::beforeSharedAccess() {
+void DeterministicSchedule::beforeSharedAccess() {
   if (tls_sem) {
     sem_wait(tls_sem);
   }
 }
 
-void
-DeterministicSchedule::afterSharedAccess() {
+void DeterministicSchedule::afterSharedAccess() {
   auto sched = tls_sched;
   if (!sched) {
     return;
@@ -134,16 +132,29 @@ DeterministicSchedule::afterSharedAccess() {
   sem_post(sched->sems_[sched->scheduler_(sched->sems_.size())]);
 }
 
-int
-DeterministicSchedule::getRandNumber(int n) {
+int DeterministicSchedule::getRandNumber(int n) {
   if (tls_sched) {
     return tls_sched->scheduler_(n);
   }
   return std::rand() % n;
 }
 
-sem_t*
-DeterministicSchedule::beforeThreadCreate() {
+int DeterministicSchedule::getcpu(unsigned* cpu, unsigned* node, void* unused) {
+  if (!tls_threadId && tls_sched) {
+    beforeSharedAccess();
+    tls_threadId = tls_sched->nextThreadId_++;
+    afterSharedAccess();
+  }
+  if (cpu) {
+    *cpu = tls_threadId;
+  }
+  if (node) {
+    *node = tls_threadId;
+  }
+  return 0;
+}
+
+sem_t* DeterministicSchedule::beforeThreadCreate() {
   sem_t* s = new sem_t;
   sem_init(s, 0, 0);
   beforeSharedAccess();
@@ -152,8 +163,7 @@ DeterministicSchedule::beforeThreadCreate() {
   return s;
 }
 
-void
-DeterministicSchedule::afterThreadCreate(sem_t* sem) {
+void DeterministicSchedule::afterThreadCreate(sem_t* sem) {
   assert(tls_sem == nullptr);
   assert(tls_sched == nullptr);
   tls_sem = sem;
@@ -168,13 +178,13 @@ DeterministicSchedule::afterThreadCreate(sem_t* sem) {
   }
 }
 
-void
-DeterministicSchedule::beforeThreadExit() {
+void DeterministicSchedule::beforeThreadExit() {
   assert(tls_sched == this);
   beforeSharedAccess();
   sems_.erase(std::find(sems_.begin(), sems_.end(), tls_sem));
   active_.erase(std::this_thread::get_id());
   if (sems_.size() > 0) {
+    FOLLY_TEST_DSCHED_VLOG("exiting");
     afterSharedAccess();
   }
   sem_destroy(tls_sem);
@@ -183,57 +193,60 @@ DeterministicSchedule::beforeThreadExit() {
   tls_sched = nullptr;
 }
 
-void
-DeterministicSchedule::join(std::thread& child) {
+void DeterministicSchedule::join(std::thread& child) {
   auto sched = tls_sched;
   if (sched) {
     bool done = false;
     while (!done) {
       beforeSharedAccess();
       done = !sched->active_.count(child.get_id());
+      if (done) {
+        FOLLY_TEST_DSCHED_VLOG("joined " << std::hex << child.get_id());
+      }
       afterSharedAccess();
     }
   }
   child.join();
 }
 
-void
-DeterministicSchedule::post(sem_t* sem) {
+void DeterministicSchedule::post(sem_t* sem) {
   beforeSharedAccess();
   sem_post(sem);
+  FOLLY_TEST_DSCHED_VLOG("sem_post(" << sem << ")");
   afterSharedAccess();
 }
 
-bool
-DeterministicSchedule::tryWait(sem_t* sem) {
+bool DeterministicSchedule::tryWait(sem_t* sem) {
   beforeSharedAccess();
   int rv = sem_trywait(sem);
+  int e = rv == 0 ? 0 : errno;
+  FOLLY_TEST_DSCHED_VLOG("sem_trywait(" << sem << ") = " << rv
+                                        << " errno=" << e);
   afterSharedAccess();
   if (rv == 0) {
     return true;
   } else {
-    assert(errno == EAGAIN);
+    assert(e == EAGAIN);
     return false;
   }
 }
 
-void
-DeterministicSchedule::wait(sem_t* sem) {
+void DeterministicSchedule::wait(sem_t* sem) {
   while (!tryWait(sem)) {
     // we're not busy waiting because this is a deterministic schedule
   }
 }
+}
+}
 
-}}
-
-namespace folly { namespace detail {
+namespace folly {
+namespace detail {
 
 using namespace test;
 using namespace std::chrono;
 
 template <>
-FutexResult
-Futex<DeterministicAtomic>::futexWaitImpl(
+FutexResult Futex<DeterministicAtomic>::futexWaitImpl(
     uint32_t expected,
     time_point<system_clock>* absSystemTimeout,
     time_point<steady_clock>* absSteadyTimeout,
@@ -244,6 +257,9 @@ Futex<DeterministicAtomic>::futexWaitImpl(
   int futexErrno = 0;
 
   DeterministicSchedule::beforeSharedAccess();
+  FOLLY_TEST_DSCHED_VLOG(this << ".futexWait(" << std::hex << expected
+                              << ", .., " << std::hex << waitMask
+                              << ") beginning..");
   futexLock.lock();
   if (data == expected) {
     auto& queue = futexQueues[this];
@@ -260,17 +276,16 @@ Futex<DeterministicAtomic>::futexWaitImpl(
       // a 10% probability if we haven't been woken up already
       if (!awoken && hasTimeout &&
           DeterministicSchedule::getRandNumber(100) < 10) {
-        assert(futexQueues.count(this) != 0 &&
-               &futexQueues[this] == &queue);
+        assert(futexQueues.count(this) != 0 && &futexQueues[this] == &queue);
         queue.erase(ours);
         if (queue.empty()) {
           futexQueues.erase(this);
         }
         // Simulate ETIMEDOUT 90% of the time and other failures
         // remaining time
-        result =
-          DeterministicSchedule::getRandNumber(100) >= 10
-              ? FutexResult::TIMEDOUT : FutexResult::INTERRUPTED;
+        result = DeterministicSchedule::getRandNumber(100) >= 10
+                     ? FutexResult::TIMEDOUT
+                     : FutexResult::INTERRUPTED;
         break;
       }
     }
@@ -278,13 +293,31 @@ Futex<DeterministicAtomic>::futexWaitImpl(
     result = FutexResult::VALUE_CHANGED;
   }
   futexLock.unlock();
+
+  char const* resultStr = "?";
+  switch (result) {
+  case FutexResult::AWOKEN:
+    resultStr = "AWOKEN";
+    break;
+  case FutexResult::TIMEDOUT:
+    resultStr = "TIMEDOUT";
+    break;
+  case FutexResult::INTERRUPTED:
+    resultStr = "INTERRUPTED";
+    break;
+  case FutexResult::VALUE_CHANGED:
+    resultStr = "VALUE_CHANGED";
+    break;
+  }
+  FOLLY_TEST_DSCHED_VLOG(this << ".futexWait(" << std::hex << expected
+                              << ", .., " << std::hex << waitMask << ") -> "
+                              << resultStr);
   DeterministicSchedule::afterSharedAccess();
   return result;
 }
 
-template<>
-int
-Futex<DeterministicAtomic>::futexWake(int count, uint32_t wakeMask) {
+template <>
+int Futex<DeterministicAtomic>::futexWake(int count, uint32_t wakeMask) {
   int rv = 0;
   DeterministicSchedule::beforeSharedAccess();
   futexLock.lock();
@@ -304,44 +337,36 @@ Futex<DeterministicAtomic>::futexWake(int count, uint32_t wakeMask) {
     }
   }
   futexLock.unlock();
+  FOLLY_TEST_DSCHED_VLOG(this << ".futexWake(" << count << ", " << std::hex
+                              << wakeMask << ") -> " << rv);
   DeterministicSchedule::afterSharedAccess();
   return rv;
 }
 
-
-template<>
+template <>
 CacheLocality const& CacheLocality::system<test::DeterministicAtomic>() {
   static CacheLocality cache(CacheLocality::uniform(16));
   return cache;
 }
 
-template<>
-test::DeterministicAtomic<size_t>
-    SequentialThreadId<test::DeterministicAtomic>::prevId(0);
-
-template<>
-FOLLY_TLS size_t
-    SequentialThreadId<test::DeterministicAtomic>::currentId(0);
-
-template<>
+template <>
 const AccessSpreader<test::DeterministicAtomic>
-AccessSpreader<test::DeterministicAtomic>::stripeByCore(
+    AccessSpreader<test::DeterministicAtomic>::stripeByCore(
         CacheLocality::system<>().numCachesByLevel.front());
 
-template<>
+template <>
 const AccessSpreader<test::DeterministicAtomic>
-AccessSpreader<test::DeterministicAtomic>::stripeByChip(
+    AccessSpreader<test::DeterministicAtomic>::stripeByChip(
         CacheLocality::system<>().numCachesByLevel.back());
 
-template<>
-AccessSpreaderArray<test::DeterministicAtomic,128>
-AccessSpreaderArray<test::DeterministicAtomic,128>::sharedInstance = {};
-
+template <>
+AccessSpreaderArray<test::DeterministicAtomic, 128>
+    AccessSpreaderArray<test::DeterministicAtomic, 128>::sharedInstance = {};
 
-template<>
-Getcpu::Func
-AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(size_t numStripes) {
-  return &SequentialThreadId<test::DeterministicAtomic>::getcpu;
+template <>
+Getcpu::Func AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(
+    size_t numStripes) {
+  return &DeterministicSchedule::getcpu;
+}
+}
 }
-
-}}

folly/test/DeterministicSchedule.h

@@ -25,12 +25,23 @@
 #include <semaphore.h>
 #include <errno.h>
 #include <assert.h>
+#include <glog/logging.h>
 
 #include <folly/ScopeGuard.h>
 #include <folly/detail/CacheLocality.h>
 #include <folly/detail/Futex.h>
 
-namespace folly { namespace test {
+namespace folly {
+namespace test {
+
+// This is ugly, but better perf for DeterministicAtomic translates
+// directly to more states explored and tested
+#define FOLLY_TEST_DSCHED_VLOG(msg...)                                  \
+  do {                                                                  \
+    if (false) {                                                        \
+      VLOG(2) << std::hex << std::this_thread::get_id() << ": " << msg; \
+    }                                                                   \
+  } while (false)
 
 /**
  * DeterministicSchedule coordinates the inter-thread communication of a
@@ -80,7 +91,8 @@ class DeterministicSchedule : boost::noncopyable {
    * runnable thread.  The subset is chosen with size n, and the choice
    * is made every m steps.
    */
-  static std::function<int(int)> uniformSubset(long seed, int n = 2,
+  static std::function<int(int)> uniformSubset(long seed,
+                                               int n = 2,
                                                int m = 64);
 
   /** Obtains permission for the current thread to perform inter-thread
@@ -99,13 +111,23 @@ class DeterministicSchedule : boost::noncopyable {
     auto sched = tls_sched;
     auto sem = sched ? sched->beforeThreadCreate() : nullptr;
     auto child = std::thread([=](Args... a) {
-      if (sched) sched->afterThreadCreate(sem);
-      SCOPE_EXIT { if (sched) sched->beforeThreadExit(); };
+      if (sched) {
+        sched->afterThreadCreate(sem);
+        beforeSharedAccess();
+        FOLLY_TEST_DSCHED_VLOG("running");
+        afterSharedAccess();
+      }
+      SCOPE_EXIT {
+        if (sched) {
+          sched->beforeThreadExit();
+        }
+      };
       func(a...);
     }, args...);
     if (sched) {
       beforeSharedAccess();
       sched->active_.insert(child.get_id());
+      FOLLY_TEST_DSCHED_VLOG("forked " << std::hex << child.get_id());
       afterSharedAccess();
     }
     return child;
@@ -128,20 +150,24 @@ class DeterministicSchedule : boost::noncopyable {
    *  not set-up it falls back to std::rand() */
   static int getRandNumber(int n);
 
+  /** Deterministic implemencation of getcpu */
+  static int getcpu(unsigned* cpu, unsigned* node, void* unused);
+
  private:
   static FOLLY_TLS sem_t* tls_sem;
   static FOLLY_TLS DeterministicSchedule* tls_sched;
+  static FOLLY_TLS unsigned tls_threadId;
 
   std::function<int(int)> scheduler_;
   std::vector<sem_t*> sems_;
   std::unordered_set<std::thread::id> active_;
+  unsigned nextThreadId_;
 
   sem_t* beforeThreadCreate();
   void afterThreadCreate(sem_t*);
   void beforeThreadExit();
 };
 
-
 /**
  * DeterministicAtomic<T> is a drop-in replacement std::atomic<T> that
  * cooperates with DeterministicSchedule.
@@ -152,29 +178,33 @@ struct DeterministicAtomic {
 
   DeterministicAtomic() = default;
   ~DeterministicAtomic() = default;
-  DeterministicAtomic(DeterministicAtomic<T> const &) = delete;
-  DeterministicAtomic<T>& operator= (DeterministicAtomic<T> const &) = delete;
+  DeterministicAtomic(DeterministicAtomic<T> const&) = delete;
+  DeterministicAtomic<T>& operator=(DeterministicAtomic<T> const&) = delete;
 
   constexpr /* implicit */ DeterministicAtomic(T v) noexcept : data(v) {}
 
-  bool is_lock_free() const noexcept {
-    return data.is_lock_free();
-  }
+  bool is_lock_free() const noexcept { return data.is_lock_free(); }
 
   bool compare_exchange_strong(
-          T& v0, T v1,
-          std::memory_order mo = std::memory_order_seq_cst) noexcept {
+      T& v0, T v1, std::memory_order mo = std::memory_order_seq_cst) noexcept {
     DeterministicSchedule::beforeSharedAccess();
+    auto orig = v0;
     bool rv = data.compare_exchange_strong(v0, v1, mo);
+    FOLLY_TEST_DSCHED_VLOG(this << ".compare_exchange_strong(" << std::hex
+                                << orig << ", " << std::hex << v1 << ") -> "
+                                << rv << "," << std::hex << v0);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
   bool compare_exchange_weak(
-          T& v0, T v1,
-          std::memory_order mo = std::memory_order_seq_cst) noexcept {
+      T& v0, T v1, std::memory_order mo = std::memory_order_seq_cst) noexcept {
     DeterministicSchedule::beforeSharedAccess();
+    auto orig = v0;
     bool rv = data.compare_exchange_weak(v0, v1, mo);
+    FOLLY_TEST_DSCHED_VLOG(this << ".compare_exchange_weak(" << std::hex << orig
+                                << ", " << std::hex << v1 << ") -> " << rv
+                                << "," << std::hex << v0);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -182,13 +212,16 @@ struct DeterministicAtomic {
   T exchange(T v, std::memory_order mo = std::memory_order_seq_cst) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data.exchange(v, mo);
+    FOLLY_TEST_DSCHED_VLOG(this << ".exchange(" << std::hex << v << ") -> "
+                                << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  /* implicit */ operator T () const noexcept {
+  /* implicit */ operator T() const noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data;
+    FOLLY_TEST_DSCHED_VLOG(this << "() -> " << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -196,13 +229,15 @@ struct DeterministicAtomic {
   T load(std::memory_order mo = std::memory_order_seq_cst) const noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data.load(mo);
+    FOLLY_TEST_DSCHED_VLOG(this << ".load() -> " << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator= (T v) noexcept {
+  T operator=(T v) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = (data = v);
+    FOLLY_TEST_DSCHED_VLOG(this << " = " << std::hex << v);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -210,40 +245,47 @@ struct DeterministicAtomic {
   void store(T v, std::memory_order mo = std::memory_order_seq_cst) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     data.store(v, mo);
+    FOLLY_TEST_DSCHED_VLOG(this << ".store(" << std::hex << v << ")");
     DeterministicSchedule::afterSharedAccess();
   }
 
-  T operator++ () noexcept {
+  T operator++() noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = ++data;
+    FOLLY_TEST_DSCHED_VLOG(this << " pre++ -> " << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator++ (int postDummy) noexcept {
+  T operator++(int postDummy) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data++;
+    FOLLY_TEST_DSCHED_VLOG(this << " post++ -> " << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator-- () noexcept {
+  T operator--() noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = --data;
+    FOLLY_TEST_DSCHED_VLOG(this << " pre-- -> " << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator-- (int postDummy) noexcept {
+  T operator--(int postDummy) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data--;
+    FOLLY_TEST_DSCHED_VLOG(this << " post-- -> " << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator+= (T v) noexcept {
+  T operator+=(T v) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = (data += v);
+    FOLLY_TEST_DSCHED_VLOG(this << " += " << std::hex << v << " -> " << std::hex
+                                << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -252,13 +294,17 @@ struct DeterministicAtomic {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data;
     data += v;
+    FOLLY_TEST_DSCHED_VLOG(this << ".fetch_add(" << std::hex << v << ") -> "
+                                << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator-= (T v) noexcept {
+  T operator-=(T v) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = (data -= v);
+    FOLLY_TEST_DSCHED_VLOG(this << " -= " << std::hex << v << " -> " << std::hex
+                                << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -267,13 +313,17 @@ struct DeterministicAtomic {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data;
     data -= v;
+    FOLLY_TEST_DSCHED_VLOG(this << ".fetch_sub(" << std::hex << v << ") -> "
+                                << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator&= (T v) noexcept {
+  T operator&=(T v) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = (data &= v);
+    FOLLY_TEST_DSCHED_VLOG(this << " &= " << std::hex << v << " -> " << std::hex
+                                << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -282,13 +332,17 @@ struct DeterministicAtomic {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data;
     data &= v;
+    FOLLY_TEST_DSCHED_VLOG(this << ".fetch_and(" << std::hex << v << ") -> "
+                                << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator|= (T v) noexcept {
+  T operator|=(T v) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = (data |= v);
+    FOLLY_TEST_DSCHED_VLOG(this << " |= " << std::hex << v << " -> " << std::hex
+                                << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -297,13 +351,17 @@ struct DeterministicAtomic {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data;
     data |= v;
+    FOLLY_TEST_DSCHED_VLOG(this << ".fetch_or(" << std::hex << v << ") -> "
+                                << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 
-  T operator^= (T v) noexcept {
+  T operator^=(T v) noexcept {
     DeterministicSchedule::beforeSharedAccess();
     T rv = (data ^= v);
+    FOLLY_TEST_DSCHED_VLOG(this << " ^= " << std::hex << v << " -> " << std::hex
+                                << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
@@ -312,29 +370,32 @@ struct DeterministicAtomic {
     DeterministicSchedule::beforeSharedAccess();
     T rv = data;
     data ^= v;
+    FOLLY_TEST_DSCHED_VLOG(this << ".fetch_xor(" << std::hex << v << ") -> "
+                                << std::hex << rv);
     DeterministicSchedule::afterSharedAccess();
     return rv;
   }
 };
-
-}} // namespace folly::test
+}
+} // namespace folly::test
 
 /* Specialization declarations */
 
-namespace folly { namespace detail {
+namespace folly {
+namespace detail {
 
-template<>
+template <>
 int Futex<test::DeterministicAtomic>::futexWake(int count, uint32_t wakeMask);
 
-template<>
+template <>
 FutexResult Futex<test::DeterministicAtomic>::futexWaitImpl(
     uint32_t expected,
     std::chrono::time_point<std::chrono::system_clock>* absSystemTime,
     std::chrono::time_point<std::chrono::steady_clock>* absSteadyTime,
     uint32_t waitMask);
 
-template<>
-Getcpu::Func
-AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(size_t numStripes);
-
-}} // namespace folly::detail
+template <>
+Getcpu::Func AccessSpreader<test::DeterministicAtomic>::pickGetcpuFunc(
+    size_t numStripes);
+}
+} // namespace folly::detail