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AK: Add Atomic.h

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Use gcc built-in atomics
This commit is contained in:
Tom 2019-10-12 11:17:34 -06:00 • committed by Andreas Kling
parent 2530378f59
commit b0773a8ea6
6 changed files with 606 additions and 53 deletions
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30
Kernel/Lock.cpp
View file

@ -9,15 +9,15 @@ void Lock::lock()
hang();
}
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
bool expected = false;
if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
if (!m_holder || m_holder == current) {
m_holder = current;
++m_level;
memory_barrier();
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return;
}
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
}
Scheduler::donate_to(m_holder, m_name);
}
@ -26,18 +26,17 @@ void Lock::lock()
void Lock::unlock()
{
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
bool expected = false;
if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
ASSERT(m_holder == current);
ASSERT(m_level);
--m_level;
if (m_level) {
memory_barrier();
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return;
}
m_holder = nullptr;
memory_barrier();
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return;
}
Scheduler::donate_to(m_holder, m_name);
@ -47,25 +46,24 @@ void Lock::unlock()
bool Lock::unlock_if_locked()
{
for (;;) {
if (CAS(&m_lock, 1, 0) == 0) {
bool expected = false;
if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
if (m_level == 0) {
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return false;
}
if (m_holder != current) {
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return false;
}
ASSERT(m_level);
--m_level;
if (m_level) {
memory_barrier();
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return false;
}
m_holder = nullptr;
memory_barrier();
m_lock = 0;
m_lock.store(false, AK::memory_order_release);
return true;
}
}

14
Kernel/Lock.h
View file

@ -2,6 +2,7 @@
#include <AK/Assertions.h>
#include <AK/Types.h>
#include <AK/Atomic.h>
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/KSyms.h>
#include <Kernel/Scheduler.h>
@ -9,17 +10,6 @@
class Thread;
extern Thread* current;
static inline u32 CAS(volatile u32* mem, u32 newval, u32 oldval)
{
u32 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)
@ -35,7 +25,7 @@ public:
const char* name() const { return m_name; }
private:
volatile u32 m_lock { 0 };
Atomic<bool> m_lock { false };
u32 m_level { 0 };
Thread* m_holder { nullptr };
const char* m_name { nullptr };