Retro68/gcc/libsanitizer/tsan/tsan_mutex.cc
2014-09-21 19:33:12 +02:00

273 lines
7.2 KiB
C++

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