Atmosphere/libraries/libmesosphere/include/mesosphere/kern_k_light_lock.hpp
2022-03-23 09:10:50 -07:00

68 lines
2.5 KiB
C++

/*
* Copyright (c) Atmosphère-NX
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include <mesosphere/kern_common.hpp>
#include <mesosphere/kern_select_cpu.hpp>
#include <mesosphere/kern_k_current_context.hpp>
#include <mesosphere/kern_k_scoped_lock.hpp>
namespace ams::kern {
class KLightLock {
private:
util::Atomic<uintptr_t> m_tag;
public:
constexpr ALWAYS_INLINE KLightLock() : m_tag(0) { /* ... */ }
void Lock() {
MESOSPHERE_ASSERT_THIS();
const uintptr_t cur_thread = reinterpret_cast<uintptr_t>(GetCurrentThreadPointer());
while (true) {
uintptr_t old_tag = m_tag.Load<std::memory_order_relaxed>();
while (!m_tag.CompareExchangeWeak<std::memory_order_acquire>(old_tag, (old_tag == 0) ? cur_thread : (old_tag | 1))) {
/* ... */
}
if (old_tag == 0 || this->LockSlowPath(old_tag | 1, cur_thread)) {
break;
}
}
}
ALWAYS_INLINE void Unlock() {
MESOSPHERE_ASSERT_THIS();
const uintptr_t cur_thread = reinterpret_cast<uintptr_t>(GetCurrentThreadPointer());
uintptr_t expected = cur_thread;
if (!m_tag.CompareExchangeStrong<std::memory_order_release>(expected, 0)) {
this->UnlockSlowPath(cur_thread);
}
}
NOINLINE bool LockSlowPath(uintptr_t owner, uintptr_t cur_thread);
NOINLINE void UnlockSlowPath(uintptr_t cur_thread);
ALWAYS_INLINE bool IsLocked() const { return m_tag.Load() != 0; }
ALWAYS_INLINE bool IsLockedByCurrentThread() const { return (m_tag.Load() | 0x1ul) == (reinterpret_cast<uintptr_t>(GetCurrentThreadPointer()) | 0x1ul); }
};
using KScopedLightLock = KScopedLock<KLightLock>;
}