Atmosphere/libraries/libmesosphere/include/mesosphere/kern_k_scheduler_lock.hpp

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/*
* Copyright (c) Atmosphère-NX
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*
* 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_k_spin_lock.hpp>
#include <mesosphere/kern_k_current_context.hpp>
#include <mesosphere/kern_k_scoped_lock.hpp>
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namespace ams::kern {
class KThread;
template<typename T>
concept KSchedulerLockable = !std::is_reference<T>::value && requires(T) {
{ T::DisableScheduling() } -> std::same_as<void>;
{ T::EnableScheduling(std::declval<u64>()) } -> std::same_as<void>;
{ T::UpdateHighestPriorityThreads() } -> std::convertible_to<u64>;
};
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template<typename SchedulerType> requires KSchedulerLockable<SchedulerType>
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class KAbstractSchedulerLock {
private:
KAlignedSpinLock m_spin_lock;
s32 m_lock_count;
KThread *m_owner_thread;
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public:
constexpr ALWAYS_INLINE KAbstractSchedulerLock() : m_spin_lock(), m_lock_count(0), m_owner_thread(nullptr) { MESOSPHERE_ASSERT_THIS(); }
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ALWAYS_INLINE bool IsLockedByCurrentThread() const {
MESOSPHERE_ASSERT_THIS();
return m_owner_thread == GetCurrentThreadPointer();
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}
NOINLINE void Lock() {
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MESOSPHERE_ASSERT_THIS();
if (this->IsLockedByCurrentThread()) {
/* If we already own the lock, we can just increment the count. */
MESOSPHERE_ASSERT(m_lock_count > 0);
m_lock_count++;
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} else {
/* Otherwise, we want to disable scheduling and acquire the spinlock. */
SchedulerType::DisableScheduling();
m_spin_lock.Lock();
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/* For debug, ensure that our state is valid. */
MESOSPHERE_ASSERT(m_lock_count == 0);
MESOSPHERE_ASSERT(m_owner_thread == nullptr);
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/* Increment count, take ownership. */
m_lock_count = 1;
m_owner_thread = GetCurrentThreadPointer();
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}
}
NOINLINE void Unlock() {
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MESOSPHERE_ASSERT_THIS();
MESOSPHERE_ASSERT(this->IsLockedByCurrentThread());
MESOSPHERE_ASSERT(m_lock_count > 0);
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/* Release an instance of the lock. */
if ((--m_lock_count) == 0) {
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/* Perform a memory barrier here. */
cpu::DataMemoryBarrierInnerShareable();
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/* We're no longer going to hold the lock. Take note of what cores need scheduling. */
const u64 cores_needing_scheduling = SchedulerType::UpdateHighestPriorityThreads();
/* Note that we no longer hold the lock, and unlock the spinlock. */
m_owner_thread = nullptr;
m_spin_lock.Unlock();
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/* Enable scheduling, and perform a rescheduling operation. */
SchedulerType::EnableScheduling(cores_needing_scheduling);
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}
}
};
}