diff options
Diffstat (limited to 'third_party/abseil_cpp/absl/synchronization/mutex.cc')
| -rw-r--r-- | third_party/abseil_cpp/absl/synchronization/mutex.cc | 112 |
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 |