274 lines
7.3 KiB
C++
274 lines
7.3 KiB
C++
//===-- tsan_mutex.cc -----------------------------------------------------===//
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of ThreadSanitizer (TSan), a race detector.
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//
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//===----------------------------------------------------------------------===//
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#include "sanitizer_common/sanitizer_libc.h"
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#include "tsan_mutex.h"
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#include "tsan_platform.h"
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#include "tsan_rtl.h"
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namespace __tsan {
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// Simple reader-writer spin-mutex. Optimized for not-so-contended case.
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// Readers have preference, can possibly starvate writers.
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// The table fixes what mutexes can be locked under what mutexes.
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// E.g. if the row for MutexTypeThreads contains MutexTypeReport,
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// then Report mutex can be locked while under Threads mutex.
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// The leaf mutexes can be locked under any other mutexes.
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// Recursive locking is not supported.
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#if TSAN_DEBUG && !TSAN_GO
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const MutexType MutexTypeLeaf = (MutexType)-1;
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static MutexType CanLockTab[MutexTypeCount][MutexTypeCount] = {
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/*0 MutexTypeInvalid*/ {},
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/*1 MutexTypeTrace*/ {MutexTypeLeaf},
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/*2 MutexTypeThreads*/ {MutexTypeReport},
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/*3 MutexTypeReport*/ {MutexTypeSyncTab, MutexTypeSyncVar,
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MutexTypeMBlock, MutexTypeJavaMBlock},
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/*4 MutexTypeSyncVar*/ {MutexTypeDDetector},
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/*5 MutexTypeSyncTab*/ {MutexTypeSyncVar},
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/*6 MutexTypeSlab*/ {MutexTypeLeaf},
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/*7 MutexTypeAnnotations*/ {},
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/*8 MutexTypeAtExit*/ {MutexTypeSyncTab},
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/*9 MutexTypeMBlock*/ {MutexTypeSyncVar},
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/*10 MutexTypeJavaMBlock*/ {MutexTypeSyncVar},
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/*11 MutexTypeDDetector*/ {},
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};
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static bool CanLockAdj[MutexTypeCount][MutexTypeCount];
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#endif
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void InitializeMutex() {
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#if TSAN_DEBUG && !TSAN_GO
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// Build the "can lock" adjacency matrix.
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// If [i][j]==true, then one can lock mutex j while under mutex i.
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const int N = MutexTypeCount;
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int cnt[N] = {};
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bool leaf[N] = {};
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for (int i = 1; i < N; i++) {
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for (int j = 0; j < N; j++) {
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MutexType z = CanLockTab[i][j];
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if (z == MutexTypeInvalid)
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continue;
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if (z == MutexTypeLeaf) {
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CHECK(!leaf[i]);
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leaf[i] = true;
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continue;
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}
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CHECK(!CanLockAdj[i][(int)z]);
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CanLockAdj[i][(int)z] = true;
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cnt[i]++;
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}
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}
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for (int i = 0; i < N; i++) {
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CHECK(!leaf[i] || cnt[i] == 0);
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}
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// Add leaf mutexes.
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for (int i = 0; i < N; i++) {
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if (!leaf[i])
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continue;
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for (int j = 0; j < N; j++) {
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if (i == j || leaf[j] || j == MutexTypeInvalid)
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continue;
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CHECK(!CanLockAdj[j][i]);
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CanLockAdj[j][i] = true;
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}
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}
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// Build the transitive closure.
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bool CanLockAdj2[MutexTypeCount][MutexTypeCount];
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for (int i = 0; i < N; i++) {
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for (int j = 0; j < N; j++) {
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CanLockAdj2[i][j] = CanLockAdj[i][j];
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}
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}
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for (int k = 0; k < N; k++) {
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for (int i = 0; i < N; i++) {
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for (int j = 0; j < N; j++) {
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if (CanLockAdj2[i][k] && CanLockAdj2[k][j]) {
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CanLockAdj2[i][j] = true;
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}
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}
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}
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}
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#if 0
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Printf("Can lock graph:\n");
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for (int i = 0; i < N; i++) {
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for (int j = 0; j < N; j++) {
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Printf("%d ", CanLockAdj[i][j]);
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}
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Printf("\n");
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}
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Printf("Can lock graph closure:\n");
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for (int i = 0; i < N; i++) {
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for (int j = 0; j < N; j++) {
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Printf("%d ", CanLockAdj2[i][j]);
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}
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Printf("\n");
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}
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#endif
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// Verify that the graph is acyclic.
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for (int i = 0; i < N; i++) {
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if (CanLockAdj2[i][i]) {
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Printf("Mutex %d participates in a cycle\n", i);
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Die();
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}
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}
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#endif
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}
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InternalDeadlockDetector::InternalDeadlockDetector() {
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// Rely on zero initialization because some mutexes can be locked before ctor.
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}
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#if TSAN_DEBUG && !TSAN_GO
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void InternalDeadlockDetector::Lock(MutexType t) {
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// Printf("LOCK %d @%zu\n", t, seq_ + 1);
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CHECK_GT(t, MutexTypeInvalid);
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CHECK_LT(t, MutexTypeCount);
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u64 max_seq = 0;
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u64 max_idx = MutexTypeInvalid;
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for (int i = 0; i != MutexTypeCount; i++) {
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if (locked_[i] == 0)
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continue;
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CHECK_NE(locked_[i], max_seq);
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if (max_seq < locked_[i]) {
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max_seq = locked_[i];
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max_idx = i;
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}
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}
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locked_[t] = ++seq_;
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if (max_idx == MutexTypeInvalid)
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return;
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// Printf(" last %d @%zu\n", max_idx, max_seq);
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if (!CanLockAdj[max_idx][t]) {
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Printf("ThreadSanitizer: internal deadlock detected\n");
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Printf("ThreadSanitizer: can't lock %d while under %zu\n",
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t, (uptr)max_idx);
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CHECK(0);
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}
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}
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void InternalDeadlockDetector::Unlock(MutexType t) {
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// Printf("UNLO %d @%zu #%zu\n", t, seq_, locked_[t]);
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CHECK(locked_[t]);
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locked_[t] = 0;
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}
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#endif
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const uptr kUnlocked = 0;
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const uptr kWriteLock = 1;
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const uptr kReadLock = 2;
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class Backoff {
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public:
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Backoff()
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: iter_() {
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}
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bool Do() {
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if (iter_++ < kActiveSpinIters)
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proc_yield(kActiveSpinCnt);
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else
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internal_sched_yield();
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return true;
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}
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u64 Contention() const {
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u64 active = iter_ % kActiveSpinIters;
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u64 passive = iter_ - active;
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return active + 10 * passive;
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}
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private:
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int iter_;
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static const int kActiveSpinIters = 10;
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static const int kActiveSpinCnt = 20;
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};
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Mutex::Mutex(MutexType type, StatType stat_type) {
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CHECK_GT(type, MutexTypeInvalid);
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CHECK_LT(type, MutexTypeCount);
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#if TSAN_DEBUG
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type_ = type;
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#endif
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#if TSAN_COLLECT_STATS
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stat_type_ = stat_type;
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#endif
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atomic_store(&state_, kUnlocked, memory_order_relaxed);
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}
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Mutex::~Mutex() {
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CHECK_EQ(atomic_load(&state_, memory_order_relaxed), kUnlocked);
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}
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void Mutex::Lock() {
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#if TSAN_DEBUG && !TSAN_GO
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cur_thread()->internal_deadlock_detector.Lock(type_);
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#endif
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uptr cmp = kUnlocked;
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if (atomic_compare_exchange_strong(&state_, &cmp, kWriteLock,
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memory_order_acquire))
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return;
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for (Backoff backoff; backoff.Do();) {
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if (atomic_load(&state_, memory_order_relaxed) == kUnlocked) {
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cmp = kUnlocked;
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if (atomic_compare_exchange_weak(&state_, &cmp, kWriteLock,
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memory_order_acquire)) {
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#if TSAN_COLLECT_STATS
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StatInc(cur_thread(), stat_type_, backoff.Contention());
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#endif
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return;
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}
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}
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}
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}
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void Mutex::Unlock() {
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uptr prev = atomic_fetch_sub(&state_, kWriteLock, memory_order_release);
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(void)prev;
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DCHECK_NE(prev & kWriteLock, 0);
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#if TSAN_DEBUG && !TSAN_GO
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cur_thread()->internal_deadlock_detector.Unlock(type_);
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#endif
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}
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void Mutex::ReadLock() {
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#if TSAN_DEBUG && !TSAN_GO
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cur_thread()->internal_deadlock_detector.Lock(type_);
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#endif
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uptr prev = atomic_fetch_add(&state_, kReadLock, memory_order_acquire);
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if ((prev & kWriteLock) == 0)
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return;
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for (Backoff backoff; backoff.Do();) {
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prev = atomic_load(&state_, memory_order_acquire);
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if ((prev & kWriteLock) == 0) {
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#if TSAN_COLLECT_STATS
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StatInc(cur_thread(), stat_type_, backoff.Contention());
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#endif
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return;
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}
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}
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}
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void Mutex::ReadUnlock() {
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uptr prev = atomic_fetch_sub(&state_, kReadLock, memory_order_release);
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(void)prev;
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DCHECK_EQ(prev & kWriteLock, 0);
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DCHECK_GT(prev & ~kWriteLock, 0);
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#if TSAN_DEBUG && !TSAN_GO
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cur_thread()->internal_deadlock_detector.Unlock(type_);
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#endif
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}
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void Mutex::CheckLocked() {
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CHECK_NE(atomic_load(&state_, memory_order_relaxed), 0);
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}
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} // namespace __tsan
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