mirror of
https://github.com/topjohnwu/Magisk.git
synced 2024-12-23 08:27:40 +00:00
80 lines
2.9 KiB
C++
80 lines
2.9 KiB
C++
/*
|
|
* Copyright (C) 2015 The Android Open Source Project
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* * Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* * Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
|
|
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
|
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
|
|
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
#ifndef _BIONIC_LOCK_H
|
|
#define _BIONIC_LOCK_H
|
|
|
|
#include "stdatomic.h"
|
|
#include "bionic_futex.h"
|
|
#include "bionic_macros.h"
|
|
|
|
// Lock is used in places like pthread_rwlock_t, which can be initialized without calling
|
|
// an initialization function. So make sure Lock can be initialized by setting its memory to 0.
|
|
class Lock {
|
|
private:
|
|
enum LockState {
|
|
Unlocked = 0,
|
|
LockedWithoutWaiter,
|
|
LockedWithWaiter,
|
|
};
|
|
_Atomic(LockState) state;
|
|
bool process_shared;
|
|
|
|
public:
|
|
void init(bool process_shared) {
|
|
atomic_init(&state, Unlocked);
|
|
this->process_shared = process_shared;
|
|
}
|
|
|
|
bool trylock() {
|
|
LockState old_state = Unlocked;
|
|
return __predict_true(atomic_compare_exchange_strong_explicit(&state, &old_state,
|
|
LockedWithoutWaiter, memory_order_acquire, memory_order_relaxed));
|
|
}
|
|
|
|
void lock() {
|
|
LockState old_state = Unlocked;
|
|
if (__predict_true(atomic_compare_exchange_strong_explicit(&state, &old_state,
|
|
LockedWithoutWaiter, memory_order_acquire, memory_order_relaxed))) {
|
|
return;
|
|
}
|
|
while (atomic_exchange_explicit(&state, LockedWithWaiter, memory_order_acquire) != Unlocked) {
|
|
// TODO: As the critical section is brief, it is a better choice to spin a few times befor sleeping.
|
|
__futex_wait_ex(&state, process_shared, LockedWithWaiter, false, nullptr);
|
|
}
|
|
return;
|
|
}
|
|
|
|
void unlock() {
|
|
if (atomic_exchange_explicit(&state, Unlocked, memory_order_release) == LockedWithWaiter) {
|
|
__futex_wake_ex(&state, process_shared, 1);
|
|
}
|
|
}
|
|
};
|
|
|
|
#endif // _BIONIC_LOCK_H
|