1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
|
#pragma once
#include "Assertions.h"
#include "Types.h"
#include "i386.h"
#include <Kernel/Scheduler.h>
class Process;
extern Process* current;
#ifndef KERNEL
#error This thing is kernel-only right now.
#endif
namespace AK {
static inline dword CAS(volatile dword* mem, dword newval, dword oldval)
{
dword ret;
asm volatile(
"cmpxchgl %2, %1"
:"=a"(ret), "+m"(*mem)
:"r"(newval), "0"(oldval)
:"cc", "memory");
return ret;
}
class Lock {
public:
Lock(const char* name = nullptr) : m_name(name) { }
~Lock() { }
void lock();
void unlock();
const char* name() const { return m_name; }
private:
volatile dword m_lock { 0 };
dword m_level { 0 };
Process* m_holder { nullptr };
const char* m_name { nullptr };
};
class Locker {
public:
ALWAYS_INLINE explicit Locker(Lock& l) : m_lock(l) { lock(); }
ALWAYS_INLINE ~Locker() { unlock(); }
ALWAYS_INLINE void unlock() { m_lock.unlock(); }
ALWAYS_INLINE void lock() { m_lock.lock(); }
private:
Lock& m_lock;
};
inline void Lock::lock()
{
ASSERT_INTERRUPTS_ENABLED();
ASSERT(!Scheduler::is_active());
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
if (!m_holder || m_holder == current) {
m_holder = current;
++m_level;
memory_barrier();
m_lock = 0;
return;
}
m_lock = 0;
}
Scheduler::donate_to(m_holder, m_name);
}
}
inline void Lock::unlock()
{
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
ASSERT(m_holder == current);
ASSERT(m_level);
--m_level;
if (m_level) {
memory_barrier();
m_lock = 0;
return;
}
m_holder = nullptr;
memory_barrier();
m_lock = 0;
return;
}
Scheduler::donate_to(m_holder, m_name);
}
}
#define LOCKER(lock) Locker locker(lock)
template<typename T>
class Lockable {
public:
Lockable() { }
Lockable(T&& resource) : m_resource(move(resource)) { }
Lock& lock() { return m_lock; }
T& resource() { return m_resource; }
T lock_and_copy()
{
LOCKER(m_lock);
return m_resource;
}
private:
T m_resource;
Lock m_lock;
};
}
using AK::Lock;
using AK::Locker;
using AK::Lockable;
|
