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Diffstat (limited to 'third_party/abseil_cpp/absl/synchronization/mutex.cc')
-rw-r--r--third_party/abseil_cpp/absl/synchronization/mutex.cc112
1 files changed, 63 insertions, 49 deletions
diff --git a/third_party/abseil_cpp/absl/synchronization/mutex.cc b/third_party/abseil_cpp/absl/synchronization/mutex.cc
index 1f8a696e08ee..9e01393ca4df 100644
--- a/third_party/abseil_cpp/absl/synchronization/mutex.cc
+++ b/third_party/abseil_cpp/absl/synchronization/mutex.cc
@@ -39,6 +39,7 @@
 #include <thread>  // NOLINT(build/c++11)
 
 #include "absl/base/attributes.h"
+#include "absl/base/call_once.h"
 #include "absl/base/config.h"
 #include "absl/base/dynamic_annotations.h"
 #include "absl/base/internal/atomic_hook.h"
@@ -49,6 +50,7 @@
 #include "absl/base/internal/spinlock.h"
 #include "absl/base/internal/sysinfo.h"
 #include "absl/base/internal/thread_identity.h"
+#include "absl/base/internal/tsan_mutex_interface.h"
 #include "absl/base/port.h"
 #include "absl/debugging/stacktrace.h"
 #include "absl/debugging/symbolize.h"
@@ -58,6 +60,7 @@
 
 using absl::base_internal::CurrentThreadIdentityIfPresent;
 using absl::base_internal::PerThreadSynch;
+using absl::base_internal::SchedulingGuard;
 using absl::base_internal::ThreadIdentity;
 using absl::synchronization_internal::GetOrCreateCurrentThreadIdentity;
 using absl::synchronization_internal::GraphCycles;
@@ -75,7 +78,7 @@ ABSL_NAMESPACE_BEGIN
 
 namespace {
 
-#if defined(THREAD_SANITIZER)
+#if defined(ABSL_HAVE_THREAD_SANITIZER)
 constexpr OnDeadlockCycle kDeadlockDetectionDefault = OnDeadlockCycle::kIgnore;
 #else
 constexpr OnDeadlockCycle kDeadlockDetectionDefault = OnDeadlockCycle::kAbort;
@@ -85,31 +88,9 @@ ABSL_CONST_INIT std::atomic<OnDeadlockCycle> synch_deadlock_detection(
     kDeadlockDetectionDefault);
 ABSL_CONST_INIT std::atomic<bool> synch_check_invariants(false);
 
-// ------------------------------------------ spinlock support
-
-// Make sure read-only globals used in the Mutex code are contained on the
-// same cacheline and cacheline aligned to eliminate any false sharing with
-// other globals from this and other modules.
-static struct MutexGlobals {
-  MutexGlobals() {
-    // Find machine-specific data needed for Delay() and
-    // TryAcquireWithSpinning(). This runs in the global constructor
-    // sequence, and before that zeros are safe values.
-    num_cpus = absl::base_internal::NumCPUs();
-    spinloop_iterations = num_cpus > 1 ? 1500 : 0;
-  }
-  int num_cpus;
-  int spinloop_iterations;
-  // Pad this struct to a full cacheline to prevent false sharing.
-  char padding[ABSL_CACHELINE_SIZE - 2 * sizeof(int)];
-} ABSL_CACHELINE_ALIGNED mutex_globals;
-static_assert(
-    sizeof(MutexGlobals) == ABSL_CACHELINE_SIZE,
-    "MutexGlobals must occupy an entire cacheline to prevent false sharing");
-
 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
-    absl::base_internal::AtomicHook<void (*)(int64_t wait_cycles)>
-        submit_profile_data;
+absl::base_internal::AtomicHook<void (*)(int64_t wait_cycles)>
+    submit_profile_data;
 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<void (*)(
     const char *msg, const void *obj, int64_t wait_cycles)>
     mutex_tracer;
@@ -143,33 +124,55 @@ void RegisterSymbolizer(bool (*fn)(const void *pc, char *out, int out_size)) {
   symbolizer.Store(fn);
 }
 
-// spinlock delay on iteration c.  Returns new c.
+struct ABSL_CACHELINE_ALIGNED MutexGlobals {
+  absl::once_flag once;
+  int num_cpus = 0;
+  int spinloop_iterations = 0;
+};
+
+static const MutexGlobals& GetMutexGlobals() {
+  ABSL_CONST_INIT static MutexGlobals data;
+  absl::base_internal::LowLevelCallOnce(&data.once, [&]() {
+    data.num_cpus = absl::base_internal::NumCPUs();
+    data.spinloop_iterations = data.num_cpus > 1 ? 1500 : 0;
+  });
+  return data;
+}
+
+// Spinlock delay on iteration c.  Returns new c.
 namespace {
   enum DelayMode { AGGRESSIVE, GENTLE };
 };
-static int Delay(int32_t c, DelayMode mode) {
+
+namespace synchronization_internal {
+int MutexDelay(int32_t c, int mode) {
   // If this a uniprocessor, only yield/sleep.  Otherwise, if the mode is
   // aggressive then spin many times before yielding.  If the mode is
   // gentle then spin only a few times before yielding.  Aggressive spinning is
   // used to ensure that an Unlock() call, which  must get the spin lock for
   // any thread to make progress gets it without undue delay.
-  int32_t limit = (mutex_globals.num_cpus > 1) ?
-      ((mode == AGGRESSIVE) ? 5000 : 250) : 0;
+  const int32_t limit =
+      GetMutexGlobals().num_cpus > 1 ? (mode == AGGRESSIVE ? 5000 : 250) : 0;
   if (c < limit) {
-    c++;               // spin
+    // Spin.
+    c++;
   } else {
+    SchedulingGuard::ScopedEnable enable_rescheduling;
     ABSL_TSAN_MUTEX_PRE_DIVERT(nullptr, 0);
-    if (c == limit) {  // yield once
+    if (c == limit) {
+      // Yield once.
       AbslInternalMutexYield();
       c++;
-    } else {           // then wait
+    } else {
+      // Then wait.
       absl::SleepFor(absl::Microseconds(10));
       c = 0;
     }
     ABSL_TSAN_MUTEX_POST_DIVERT(nullptr, 0);
   }
-  return (c);
+  return c;
 }
+}  // namespace synchronization_internal
 
 // --------------------------Generic atomic ops
 // Ensure that "(*pv & bits) == bits" by doing an atomic update of "*pv" to
@@ -489,7 +492,7 @@ struct SynchWaitParams {
   std::atomic<intptr_t> *cv_word;
 
   int64_t contention_start_cycles;  // Time (in cycles) when this thread started
-                                  // to contend for the mutex.
+                                    // to contend for the mutex.
 };
 
 struct SynchLocksHeld {
@@ -703,7 +706,7 @@ static constexpr bool kDebugMode = false;
 static constexpr bool kDebugMode = true;
 #endif
 
-#ifdef THREAD_SANITIZER
+#ifdef ABSL_INTERNAL_HAVE_TSAN_INTERFACE
 static unsigned TsanFlags(Mutex::MuHow how) {
   return how == kShared ? __tsan_mutex_read_lock : 0;
 }
@@ -1054,6 +1057,7 @@ static PerThreadSynch *DequeueAllWakeable(PerThreadSynch *head,
 // Try to remove thread s from the list of waiters on this mutex.
 // Does nothing if s is not on the waiter list.
 void Mutex::TryRemove(PerThreadSynch *s) {
+  SchedulingGuard::ScopedDisable disable_rescheduling;
   intptr_t v = mu_.load(std::memory_order_relaxed);
   // acquire spinlock & lock
   if ((v & (kMuWait | kMuSpin | kMuWriter | kMuReader)) == kMuWait &&
@@ -1118,7 +1122,7 @@ ABSL_XRAY_LOG_ARGS(1) void Mutex::Block(PerThreadSynch *s) {
       this->TryRemove(s);
       int c = 0;
       while (s->next != nullptr) {
-        c = Delay(c, GENTLE);
+        c = synchronization_internal::MutexDelay(c, GENTLE);
         this->TryRemove(s);
       }
       if (kDebugMode) {
@@ -1437,7 +1441,7 @@ void Mutex::AssertNotHeld() const {
 // Attempt to acquire *mu, and return whether successful.  The implementation
 // may spin for a short while if the lock cannot be acquired immediately.
 static bool TryAcquireWithSpinning(std::atomic<intptr_t>* mu) {
-  int c = mutex_globals.spinloop_iterations;
+  int c = GetMutexGlobals().spinloop_iterations;
   do {  // do/while somewhat faster on AMD
     intptr_t v = mu->load(std::memory_order_relaxed);
     if ((v & (kMuReader|kMuEvent)) != 0) {
@@ -1764,7 +1768,7 @@ static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
   // All memory accesses are ignored inside of mutex operations + for unlock
   // operation tsan considers that we've already released the mutex.
   bool res = false;
-#ifdef THREAD_SANITIZER
+#ifdef ABSL_INTERNAL_HAVE_TSAN_INTERFACE
   const int flags = read_lock ? __tsan_mutex_read_lock : 0;
   const int tryflags = flags | (trylock ? __tsan_mutex_try_lock : 0);
 #endif
@@ -1814,9 +1818,9 @@ static inline bool EvalConditionIgnored(Mutex *mu, const Condition *cond) {
   // So we "divert" (which un-ignores both memory accesses and synchronization)
   // and then separately turn on ignores of memory accesses.
   ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
-  ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN();
+  ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN();
   bool res = cond->Eval();
-  ANNOTATE_IGNORE_READS_AND_WRITES_END();
+  ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_END();
   ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
   static_cast<void>(mu);  // Prevent unused param warning in non-TSAN builds.
   return res;
@@ -1897,6 +1901,7 @@ static void CheckForMutexCorruption(intptr_t v, const char* label) {
 }
 
 void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
+  SchedulingGuard::ScopedDisable disable_rescheduling;
   int c = 0;
   intptr_t v = mu_.load(std::memory_order_relaxed);
   if ((v & kMuEvent) != 0) {
@@ -1998,7 +2003,8 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
     ABSL_RAW_CHECK(
         waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
         "detected illegal recursion into Mutex code");
-    c = Delay(c, GENTLE);          // delay, then try again
+    // delay, then try again
+    c = synchronization_internal::MutexDelay(c, GENTLE);
   }
   ABSL_RAW_CHECK(
       waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
@@ -2016,6 +2022,7 @@ void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
 // or it is in the process of blocking on a condition variable; it must requeue
 // itself on the mutex/condvar to wait for its condition to become true.
 ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
+  SchedulingGuard::ScopedDisable disable_rescheduling;
   intptr_t v = mu_.load(std::memory_order_relaxed);
   this->AssertReaderHeld();
   CheckForMutexCorruption(v, "Unlock");
@@ -2292,7 +2299,8 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
       mu_.store(nv, std::memory_order_release);
       break;  // out of for(;;)-loop
     }
-    c = Delay(c, AGGRESSIVE);  // aggressive here; no one can proceed till we do
+    // aggressive here; no one can proceed till we do
+    c = synchronization_internal::MutexDelay(c, AGGRESSIVE);
   }                            // end of for(;;)-loop
 
   if (wake_list != kPerThreadSynchNull) {
@@ -2304,7 +2312,8 @@ ABSL_ATTRIBUTE_NOINLINE void Mutex::UnlockSlow(SynchWaitParams *waitp) {
     if (!cond_waiter) {
       // Sample lock contention events only if the (first) waiter was trying to
       // acquire the lock, not waiting on a condition variable or Condition.
-      int64_t wait_cycles = base_internal::CycleClock::Now() - enqueue_timestamp;
+      int64_t wait_cycles =
+          base_internal::CycleClock::Now() - enqueue_timestamp;
       mutex_tracer("slow release", this, wait_cycles);
       ABSL_TSAN_MUTEX_PRE_DIVERT(this, 0);
       submit_profile_data(enqueue_timestamp);
@@ -2331,6 +2340,7 @@ void Mutex::Trans(MuHow how) {
 // It will later acquire the mutex with high probability.  Otherwise, we
 // enqueue thread w on this mutex.
 void Mutex::Fer(PerThreadSynch *w) {
+  SchedulingGuard::ScopedDisable disable_rescheduling;
   int c = 0;
   ABSL_RAW_CHECK(w->waitp->cond == nullptr,
                  "Mutex::Fer while waiting on Condition");
@@ -2380,7 +2390,7 @@ void Mutex::Fer(PerThreadSynch *w) {
         return;
       }
     }
-    c = Delay(c, GENTLE);
+    c = synchronization_internal::MutexDelay(c, GENTLE);
   }
 }
 
@@ -2429,6 +2439,7 @@ CondVar::~CondVar() {
 
 // Remove thread s from the list of waiters on this condition variable.
 void CondVar::Remove(PerThreadSynch *s) {
+  SchedulingGuard::ScopedDisable disable_rescheduling;
   intptr_t v;
   int c = 0;
   for (v = cv_.load(std::memory_order_relaxed);;
@@ -2457,7 +2468,8 @@ void CondVar::Remove(PerThreadSynch *s) {
                 std::memory_order_release);
       return;
     } else {
-      c = Delay(c, GENTLE);            // try again after a delay
+      // try again after a delay
+      c = synchronization_internal::MutexDelay(c, GENTLE);
     }
   }
 }
@@ -2490,7 +2502,7 @@ static void CondVarEnqueue(SynchWaitParams *waitp) {
          !cv_word->compare_exchange_weak(v, v | kCvSpin,
                                          std::memory_order_acquire,
                                          std::memory_order_relaxed)) {
-    c = Delay(c, GENTLE);
+    c = synchronization_internal::MutexDelay(c, GENTLE);
     v = cv_word->load(std::memory_order_relaxed);
   }
   ABSL_RAW_CHECK(waitp->thread->waitp == nullptr, "waiting when shouldn't be");
@@ -2589,6 +2601,7 @@ void CondVar::Wakeup(PerThreadSynch *w) {
 }
 
 void CondVar::Signal() {
+  SchedulingGuard::ScopedDisable disable_rescheduling;
   ABSL_TSAN_MUTEX_PRE_SIGNAL(nullptr, 0);
   intptr_t v;
   int c = 0;
@@ -2621,7 +2634,7 @@ void CondVar::Signal() {
       ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
       return;
     } else {
-      c = Delay(c, GENTLE);
+      c = synchronization_internal::MutexDelay(c, GENTLE);
     }
   }
   ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
@@ -2658,7 +2671,8 @@ void CondVar::SignalAll () {
       ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
       return;
     } else {
-      c = Delay(c, GENTLE);           // try again after a delay
+      // try again after a delay
+      c = synchronization_internal::MutexDelay(c, GENTLE);
     }
   }
   ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
@@ -2671,7 +2685,7 @@ void ReleasableMutexLock::Release() {
   this->mu_ = nullptr;
 }
 
-#ifdef THREAD_SANITIZER
+#ifdef ABSL_HAVE_THREAD_SANITIZER
 extern "C" void __tsan_read1(void *addr);
 #else
 #define __tsan_read1(addr)  // do nothing if TSan not enabled