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#pragma once
#include "Assertions.h"
#include "Types.h"
#include "i386.h"
int sched_yield();
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() { }
~Lock() { }
void lock();
void unlock();
private:
volatile dword m_lock { 0 };
dword m_level { 0 };
Process* m_holder { 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()
{
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;
}
sched_yield();
}
}
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;
}
sched_yield();
}
}
#define LOCKER(lock) Locker locker(lock)
}
using AK::Lock;
using AK::Locker;
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