126 lines
3.0 KiB
C++
126 lines
3.0 KiB
C++
/*
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* Semaphore (SM)
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*
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* Copyright (C) 2009-2011 Udo Steinberg <udo@hypervisor.org>
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* Economic rights: Technische Universitaet Dresden (Germany)
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*
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* Copyright (C) 2012-2013 Udo Steinberg, Intel Corporation.
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* Copyright (C) 2014 Udo Steinberg, FireEye, Inc.
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* Copyright (C) 2019-2023 Udo Steinberg, BedRock Systems, Inc.
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*
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* This file is part of the NOVA microhypervisor.
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*
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* NOVA is free software: you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* NOVA is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License version 2 for more details.
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*/
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#pragma once
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#include "ec.hpp"
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class Sm final : public Kobject, private Queue<Ec>
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{
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private:
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uint64_t counter { 0 };
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unsigned const id { 0 };
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Spinlock lock;
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static Slab_cache cache;
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Sm (uint64_t, unsigned);
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public:
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[[nodiscard]] static Sm *create (Status &s, uint64_t c, unsigned i)
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{
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auto const sm { new (cache) Sm (c, i) };
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if (EXPECT_FALSE (!sm))
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s = Status::MEM_OBJ;
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return sm;
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}
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void destroy()
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{
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this->~Sm();
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operator delete (this, cache);
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}
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auto get_id() const { return id; }
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void dn (Ec *const self, bool zero, uint64_t t)
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{
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{ Lock_guard <Spinlock> guard { lock };
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if (counter) {
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counter = zero ? 0 : counter - 1;
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return;
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}
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// The EC can no longer be activated
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self->block();
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enqueue_tail (self);
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}
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// At this point remote cores can unblock the EC
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if (self->block_sc()) {
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if (t)
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self->set_timeout (t, this);
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Scheduler::schedule (true);
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}
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}
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bool up()
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{
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Ec *ec;
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{ Lock_guard <Spinlock> guard { lock };
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if (!(ec = dequeue_head())) {
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if (counter == ~0ULL)
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return false;
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counter++;
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return true;
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}
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// The EC can now be activated again
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ec->unblock (Ec::sys_finish<Status::SUCCESS, true>, false);
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}
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ec->unblock_sc();
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return true;
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}
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NONNULL
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void timeout (Ec *const ec)
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{
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{ Lock_guard <Spinlock> guard { lock };
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if (!ec->blocked())
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return;
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dequeue (ec);
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// The EC can now be activated again
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ec->unblock (Ec::sys_finish<Status::TIMEOUT>, true);
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}
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ec->unblock_sc();
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}
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};
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