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#pragma once
#include <AK/Assertions.h>
#include <AK/Types.h>
#include <Kernel/KSyms.h>
#include <Kernel/Scheduler.h>
#include <Kernel/i386.h>
class Thread;
extern Thread* current;
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();
bool unlock_if_locked();
const char* name() const { return m_name; }
private:
volatile dword m_lock { 0 };
dword m_level { 0 };
Thread* m_holder { nullptr };
const char* m_name { nullptr };
};
class Locker {
public:
[[gnu::always_inline]] inline explicit Locker(Lock& l)
: m_lock(l)
{
lock();
}
[[gnu::always_inline]] inline ~Locker() { unlock(); }
[[gnu::always_inline]] inline void unlock() { m_lock.unlock(); }
[[gnu::always_inline]] inline void lock() { m_lock.lock(); }
private:
Lock& m_lock;
};
[[gnu::always_inline]] inline void Lock::lock()
{
if (!are_interrupts_enabled()) {
kprintf("Interrupts disabled when trying to take Lock{%s}\n", m_name);
dump_backtrace();
hang();
}
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);
}
}
inline bool Lock::unlock_if_locked()
{
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
if (m_level == 0) {
memory_barrier();
m_lock = 0;
return false;
}
ASSERT(m_holder == current);
ASSERT(m_level);
--m_level;
if (m_level) {
memory_barrier();
m_lock = 0;
return false;
}
m_holder = nullptr;
memory_barrier();
m_lock = 0;
return true;
}
}
}
#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;
};
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