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#pragma once
#include <AK/Assertions.h>
#include <AK/Types.h>
#include <unistd.h>
#define memory_barrier() asm volatile ("" ::: "memory")
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 GLock {
public:
GLock() { }
~GLock() { }
void lock();
void unlock();
private:
volatile dword m_lock { 0 };
dword m_level { 0 };
int m_holder { -1 };
};
class GLocker {
public:
[[gnu::always_inline]] inline explicit GLocker(GLock& l) : m_lock(l) { lock(); }
[[gnu::always_inline]] inline ~GLocker() { unlock(); }
[[gnu::always_inline]] inline void unlock() { m_lock.unlock(); }
[[gnu::always_inline]] inline void lock() { m_lock.lock(); }
private:
GLock& m_lock;
};
[[gnu::always_inline]] inline void GLock::lock()
{
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
if (m_holder == -1 || m_holder == gettid()) {
m_holder = gettid();
++m_level;
memory_barrier();
m_lock = 0;
return;
}
m_lock = 0;
}
donate(m_holder);
}
}
inline void GLock::unlock()
{
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
ASSERT(m_holder == gettid());
ASSERT(m_level);
--m_level;
if (m_level) {
memory_barrier();
m_lock = 0;
return;
}
m_holder = -1;
memory_barrier();
m_lock = 0;
return;
}
donate(m_holder);
}
}
#define LOCKER(lock) GLocker locker(lock)
template<typename T>
class GLockable {
public:
GLockable() { }
GLockable(T&& resource) : m_resource(move(resource)) { }
GLock& lock() { return m_lock; }
T& resource() { return m_resource; }
T lock_and_copy()
{
LOCKER(m_lock);
return m_resource;
}
private:
T m_resource;
GLock m_lock;
};
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