ladybird/Kernel/Lock.cpp
2019-07-29 12:00:14 +02:00

71 lines
1.6 KiB
C++

#include <Kernel/Lock.h>
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);
}
}
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);
}
}
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;
}
}
}