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| //===-- sanitizer_mutex.h ---------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is a part of ThreadSanitizer/AddressSanitizer runtime.
//
//===----------------------------------------------------------------------===//
#ifndef SANITIZER_MUTEX_H
#define SANITIZER_MUTEX_H
#include "sanitizer_atomic.h"
#include "sanitizer_internal_defs.h"
#include "sanitizer_libc.h"
namespace __sanitizer {
class StaticSpinMutex {
public:
void Init() {
atomic_store(&state_, 0, memory_order_relaxed);
}
void Lock() {
if (TryLock())
return;
LockSlow();
}
bool TryLock() {
return atomic_exchange(&state_, 1, memory_order_acquire) == 0;
}
void Unlock() {
atomic_store(&state_, 0, memory_order_release);
}
void CheckLocked() {
CHECK_EQ(atomic_load(&state_, memory_order_relaxed), 1);
}
private:
atomic_uint8_t state_;
void NOINLINE LockSlow() {
for (int i = 0;; i++) {
if (i < 10)
proc_yield(10);
else
internal_sched_yield();
if (atomic_load(&state_, memory_order_relaxed) == 0
&& atomic_exchange(&state_, 1, memory_order_acquire) == 0)
return;
}
}
};
class SpinMutex : public StaticSpinMutex {
public:
SpinMutex() {
Init();
}
private:
SpinMutex(const SpinMutex&);
void operator=(const SpinMutex&);
};
class BlockingMutex {
public:
explicit constexpr BlockingMutex(LinkerInitialized)
: opaque_storage_ {0, }, owner_ {0} {}
BlockingMutex();
void Lock();
void Unlock();
// This function does not guarantee an explicit check that the calling thread
// is the thread which owns the mutex. This behavior, while more strictly
// correct, causes problems in cases like StopTheWorld, where a parent thread
// owns the mutex but a child checks that it is locked. Rather than
// maintaining complex state to work around those situations, the check only
// checks that the mutex is owned, and assumes callers to be generally
// well-behaved.
void CheckLocked();
private:
// Solaris mutex_t has a member that requires 64-bit alignment.
ALIGNED(8) uptr opaque_storage_[10];
uptr owner_; // for debugging
};
// Reader-writer spin mutex.
class RWMutex {
public:
RWMutex() {
atomic_store(&state_, kUnlocked, memory_order_relaxed);
}
~RWMutex() {
CHECK_EQ(atomic_load(&state_, memory_order_relaxed), kUnlocked);
}
void Lock() {
u32 cmp = kUnlocked;
if (atomic_compare_exchange_strong(&state_, &cmp, kWriteLock,
memory_order_acquire))
return;
LockSlow();
}
void Unlock() {
u32 prev = atomic_fetch_sub(&state_, kWriteLock, memory_order_release);
DCHECK_NE(prev & kWriteLock, 0);
(void)prev;
}
void ReadLock() {
u32 prev = atomic_fetch_add(&state_, kReadLock, memory_order_acquire);
if ((prev & kWriteLock) == 0)
return;
ReadLockSlow();
}
void ReadUnlock() {
u32 prev = atomic_fetch_sub(&state_, kReadLock, memory_order_release);
DCHECK_EQ(prev & kWriteLock, 0);
DCHECK_GT(prev & ~kWriteLock, 0);
(void)prev;
}
void CheckLocked() {
CHECK_NE(atomic_load(&state_, memory_order_relaxed), kUnlocked);
}
private:
atomic_uint32_t state_;
enum {
kUnlocked = 0,
kWriteLock = 1,
kReadLock = 2
};
void NOINLINE LockSlow() {
for (int i = 0;; i++) {
if (i < 10)
proc_yield(10);
else
internal_sched_yield();
u32 cmp = atomic_load(&state_, memory_order_relaxed);
if (cmp == kUnlocked &&
atomic_compare_exchange_weak(&state_, &cmp, kWriteLock,
memory_order_acquire))
return;
}
}
void NOINLINE ReadLockSlow() {
for (int i = 0;; i++) {
if (i < 10)
proc_yield(10);
else
internal_sched_yield();
u32 prev = atomic_load(&state_, memory_order_acquire);
if ((prev & kWriteLock) == 0)
return;
}
}
RWMutex(const RWMutex&);
void operator = (const RWMutex&);
};
template<typename MutexType>
class GenericScopedLock {
public:
explicit GenericScopedLock(MutexType *mu)
: mu_(mu) {
mu_->Lock();
}
~GenericScopedLock() {
mu_->Unlock();
}
private:
MutexType *mu_;
GenericScopedLock(const GenericScopedLock&);
void operator=(const GenericScopedLock&);
};
template<typename MutexType>
class GenericScopedReadLock {
public:
explicit GenericScopedReadLock(MutexType *mu)
: mu_(mu) {
mu_->ReadLock();
}
~GenericScopedReadLock() {
mu_->ReadUnlock();
}
private:
MutexType *mu_;
GenericScopedReadLock(const GenericScopedReadLock&);
void operator=(const GenericScopedReadLock&);
};
typedef GenericScopedLock<StaticSpinMutex> SpinMutexLock;
typedef GenericScopedLock<BlockingMutex> BlockingMutexLock;
typedef GenericScopedLock<RWMutex> RWMutexLock;
typedef GenericScopedReadLock<RWMutex> RWMutexReadLock;
} // namespace __sanitizer
#endif // SANITIZER_MUTEX_H
|