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48f7c28a5c
Suggested by Sergey. The currently running Thread and Process are now Thread::current and Process::current respectively. :^)
90 lines
3.0 KiB
C++
90 lines
3.0 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <Kernel/KSyms.h>
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#include <Kernel/Lock.h>
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#include <Kernel/Thread.h>
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namespace Kernel {
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void Lock::lock()
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{
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ASSERT(!Scheduler::is_active());
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if (!are_interrupts_enabled()) {
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kprintf("Interrupts disabled when trying to take Lock{%s}\n", m_name);
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dump_backtrace();
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hang();
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}
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for (;;) {
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bool expected = false;
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if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
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if (!m_holder || m_holder == Thread::current) {
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m_holder = Thread::current;
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++m_level;
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m_lock.store(false, AK::memory_order_release);
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return;
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}
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Thread::current->wait_on(m_queue, &m_lock, m_holder, m_name);
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}
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}
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}
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void Lock::unlock()
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{
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for (;;) {
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bool expected = false;
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if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
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ASSERT(m_holder == Thread::current);
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ASSERT(m_level);
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--m_level;
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if (m_level) {
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m_lock.store(false, AK::memory_order_release);
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return;
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}
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m_holder = nullptr;
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m_queue.wake_one(&m_lock);
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return;
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}
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// I don't know *who* is using "m_lock", so just yield.
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Scheduler::yield();
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}
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}
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bool Lock::force_unlock_if_locked()
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{
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InterruptDisabler disabler;
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if (m_holder != Thread::current)
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return false;
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ASSERT(m_level == 1);
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ASSERT(m_holder == Thread::current);
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m_holder = nullptr;
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--m_level;
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m_queue.wake_one();
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return true;
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}
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}
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