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https://github.com/Atmosphere-NX/Atmosphere.git
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96 lines
3.4 KiB
C++
96 lines
3.4 KiB
C++
/*
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* Copyright (c) Atmosphère-NX
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <mesosphere.hpp>
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namespace ams::kern {
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namespace {
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class ThreadQueueImplForKLightLock final : public KThreadQueue {
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public:
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constexpr ThreadQueueImplForKLightLock() : KThreadQueue() { /* ... */ }
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virtual void CancelWait(KThread *waiting_thread, Result wait_result, bool cancel_timer_task) override {
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/* Do nothing, waiting to acquire a light lock cannot be canceled. */
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MESOSPHERE_UNUSED(waiting_thread, wait_result, cancel_timer_task);
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}
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};
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}
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bool KLightLock::LockSlowPath(uintptr_t _owner, uintptr_t _cur_thread) {
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KThread *cur_thread = reinterpret_cast<KThread *>(_cur_thread);
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ThreadQueueImplForKLightLock wait_queue;
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/* Pend the current thread waiting on the owner thread. */
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{
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KScopedSchedulerLock sl;
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/* Ensure we actually have locking to do. */
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if (m_tag.Load<std::memory_order_relaxed>() != _owner) {
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return false;
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}
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/* Add the current thread as a waiter on the owner. */
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KThread *owner_thread = reinterpret_cast<KThread *>(_owner & ~1ul);
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cur_thread->SetAddressKey(reinterpret_cast<uintptr_t>(std::addressof(m_tag)));
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owner_thread->AddWaiter(cur_thread);
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/* Begin waiting to hold the lock. */
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cur_thread->BeginWait(std::addressof(wait_queue));
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if (owner_thread->IsSuspended()) {
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owner_thread->ContinueIfHasKernelWaiters();
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}
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}
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return true;
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}
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void KLightLock::UnlockSlowPath(uintptr_t _cur_thread) {
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KThread *owner_thread = reinterpret_cast<KThread *>(_cur_thread);
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/* Unlock. */
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{
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KScopedSchedulerLock sl;
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/* Get the next owner. */
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bool has_waiters;
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KThread *next_owner = owner_thread->RemoveWaiterByKey(std::addressof(has_waiters), reinterpret_cast<uintptr_t>(std::addressof(m_tag)));
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/* Pass the lock to the next owner. */
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uintptr_t next_tag = 0;
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if (next_owner != nullptr) {
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next_tag = reinterpret_cast<uintptr_t>(next_owner) | static_cast<uintptr_t>(has_waiters);
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next_owner->EndWait(ResultSuccess());
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if (next_owner->IsSuspended()) {
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next_owner->ContinueIfHasKernelWaiters();
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}
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}
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/* We may have unsuspended in the process of acquiring the lock, so we'll re-suspend now if so. */
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if (owner_thread->IsSuspended()) {
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owner_thread->TrySuspend();
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}
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/* Write the new tag value. */
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m_tag.Store<std::memory_order_release>(next_tag);
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}
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}
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}
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