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5d180d1f99
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED) Since all of these checks are done in release builds as well, let's rename them to VERIFY to prevent confusion, as everyone is used to assertions being compiled out in release. We can introduce a new ASSERT macro that is specifically for debug checks, but I'm doing this wholesale conversion first since we've accumulated thousands of these already, and it's not immediately obvious which ones are suitable for ASSERT.
359 lines
14 KiB
C++
359 lines
14 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 <AK/TemporaryChange.h>
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#include <Kernel/Debug.h>
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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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#if LOCK_DEBUG
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void Lock::lock(Mode mode)
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{
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lock("unknown", 0, mode);
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}
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void Lock::lock(const char* file, int line, Mode mode)
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#else
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void Lock::lock(Mode mode)
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#endif
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{
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// NOTE: This may be called from an interrupt handler (not an IRQ handler)
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// and also from within critical sections!
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VERIFY(!Processor::current().in_irq());
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VERIFY(mode != Mode::Unlocked);
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auto current_thread = Thread::current();
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ScopedCritical critical; // in case we're not in a critical section already
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for (;;) {
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if (m_lock.exchange(true, AK::memory_order_acq_rel) != false) {
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// I don't know *who* is using "m_lock", so just yield.
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Scheduler::yield_from_critical();
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continue;
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}
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// FIXME: Do not add new readers if writers are queued.
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Mode current_mode = m_mode;
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switch (current_mode) {
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case Mode::Unlocked: {
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dbgln_if(LOCK_TRACE_DEBUG, "Lock::lock @ ({}) {}: acquire {}, currently unlocked", this, m_name, mode_to_string(mode));
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m_mode = mode;
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VERIFY(!m_holder);
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VERIFY(m_shared_holders.is_empty());
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if (mode == Mode::Exclusive) {
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m_holder = current_thread;
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} else {
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VERIFY(mode == Mode::Shared);
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m_shared_holders.set(current_thread, 1);
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}
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VERIFY(m_times_locked == 0);
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m_times_locked++;
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#if LOCK_DEBUG
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current_thread->holding_lock(*this, 1, file, line);
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#endif
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m_queue.should_block(true);
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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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case Mode::Exclusive: {
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VERIFY(m_holder);
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if (m_holder != current_thread)
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break;
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VERIFY(m_shared_holders.is_empty());
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if constexpr (LOCK_TRACE_DEBUG) {
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if (mode == Mode::Exclusive)
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dbgln("Lock::lock @ {} ({}): acquire {}, currently exclusive, holding: {}", this, m_name, mode_to_string(mode), m_times_locked);
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else
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dbgln("Lock::lock @ {} ({}): acquire exclusive (requested {}), currently exclusive, holding: {}", this, m_name, mode_to_string(mode), m_times_locked);
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}
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VERIFY(mode == Mode::Exclusive || mode == Mode::Shared);
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VERIFY(m_times_locked > 0);
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m_times_locked++;
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#if LOCK_DEBUG
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current_thread->holding_lock(*this, 1, file, line);
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#endif
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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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case Mode::Shared: {
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VERIFY(!m_holder);
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if (mode != Mode::Shared)
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break;
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dbgln_if(LOCK_TRACE_DEBUG, "Lock::lock @ {} ({}): acquire {}, currently shared, locks held {}", this, m_name, mode_to_string(mode), m_times_locked);
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VERIFY(m_times_locked > 0);
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m_times_locked++;
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VERIFY(!m_shared_holders.is_empty());
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auto it = m_shared_holders.find(current_thread);
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if (it != m_shared_holders.end())
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it->value++;
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else
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m_shared_holders.set(current_thread, 1);
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#if LOCK_DEBUG
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current_thread->holding_lock(*this, 1, file, line);
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#endif
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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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default:
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VERIFY_NOT_REACHED();
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}
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m_lock.store(false, AK::memory_order_release);
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dbgln_if(LOCK_TRACE_DEBUG, "Lock::lock @ {} ({}) waiting...", this, m_name);
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m_queue.wait_forever(m_name);
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dbgln_if(LOCK_TRACE_DEBUG, "Lock::lock @ {} ({}) waited", this, m_name);
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}
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}
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void Lock::unlock()
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{
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// NOTE: This may be called from an interrupt handler (not an IRQ handler)
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// and also from within critical sections!
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VERIFY(!Processor::current().in_irq());
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auto current_thread = Thread::current();
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ScopedCritical critical; // in case we're not in a critical section already
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for (;;) {
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if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
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Mode current_mode = m_mode;
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if constexpr (LOCK_TRACE_DEBUG) {
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if (current_mode == Mode::Shared)
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dbgln("Lock::unlock @ {} ({}): release {}, locks held: {}", this, m_name, mode_to_string(current_mode), m_times_locked);
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else
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dbgln("Lock::unlock @ {} ({}): release {}, holding: {}", this, m_name, mode_to_string(current_mode), m_times_locked);
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}
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VERIFY(current_mode != Mode::Unlocked);
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VERIFY(m_times_locked > 0);
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m_times_locked--;
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switch (current_mode) {
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case Mode::Exclusive:
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VERIFY(m_holder == current_thread);
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VERIFY(m_shared_holders.is_empty());
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if (m_times_locked == 0)
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m_holder = nullptr;
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break;
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case Mode::Shared: {
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VERIFY(!m_holder);
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auto it = m_shared_holders.find(current_thread);
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VERIFY(it != m_shared_holders.end());
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if (it->value > 1) {
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it->value--;
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} else {
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VERIFY(it->value > 0);
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m_shared_holders.remove(it);
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}
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break;
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}
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default:
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VERIFY_NOT_REACHED();
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}
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bool unlocked_last = (m_times_locked == 0);
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if (unlocked_last) {
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VERIFY(current_mode == Mode::Exclusive ? !m_holder : m_shared_holders.is_empty());
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m_mode = Mode::Unlocked;
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m_queue.should_block(false);
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}
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#if LOCK_DEBUG
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current_thread->holding_lock(*this, -1);
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#endif
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m_lock.store(false, AK::memory_order_release);
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if (unlocked_last) {
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u32 did_wake = m_queue.wake_one();
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dbgln_if(LOCK_TRACE_DEBUG, "Lock::unlock @ {} ({}) wake one ({})", this, m_name, did_wake);
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}
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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_from_critical();
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}
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}
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auto Lock::force_unlock_if_locked(u32& lock_count_to_restore) -> Mode
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{
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// NOTE: This may be called from an interrupt handler (not an IRQ handler)
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// and also from within critical sections!
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VERIFY(!Processor::current().in_irq());
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auto current_thread = Thread::current();
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ScopedCritical critical; // in case we're not in a critical section already
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for (;;) {
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if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
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Mode previous_mode;
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auto current_mode = m_mode.load(AK::MemoryOrder::memory_order_relaxed);
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switch (current_mode) {
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case Mode::Exclusive: {
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if (m_holder != current_thread) {
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m_lock.store(false, AK::MemoryOrder::memory_order_release);
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lock_count_to_restore = 0;
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return Mode::Unlocked;
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}
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dbgln_if(LOCK_RESTORE_DEBUG, "Lock::force_unlock_if_locked @ {}: unlocking exclusive with lock count: {}", this, m_times_locked);
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#if LOCK_DEBUG
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m_holder->holding_lock(*this, -(int)lock_count_to_restore);
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#endif
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m_holder = nullptr;
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VERIFY(m_times_locked > 0);
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lock_count_to_restore = m_times_locked;
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m_times_locked = 0;
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m_mode = Mode::Unlocked;
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m_queue.should_block(false);
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m_lock.store(false, AK::memory_order_release);
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previous_mode = Mode::Exclusive;
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break;
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}
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case Mode::Shared: {
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VERIFY(!m_holder);
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auto it = m_shared_holders.find(current_thread);
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if (it == m_shared_holders.end()) {
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m_lock.store(false, AK::MemoryOrder::memory_order_release);
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lock_count_to_restore = 0;
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return Mode::Unlocked;
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}
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dbgln_if(LOCK_RESTORE_DEBUG, "Lock::force_unlock_if_locked @ {}: unlocking exclusive with lock count: {}, total locks: {}",
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this, it->value, m_times_locked);
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VERIFY(it->value > 0);
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lock_count_to_restore = it->value;
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VERIFY(lock_count_to_restore > 0);
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#if LOCK_DEBUG
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m_holder->holding_lock(*this, -(int)lock_count_to_restore);
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#endif
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m_shared_holders.remove(it);
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VERIFY(m_times_locked >= lock_count_to_restore);
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m_times_locked -= lock_count_to_restore;
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if (m_times_locked == 0) {
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m_mode = Mode::Unlocked;
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m_queue.should_block(false);
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}
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m_lock.store(false, AK::memory_order_release);
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previous_mode = Mode::Shared;
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break;
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}
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case Mode::Unlocked: {
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m_lock.store(false, AK::memory_order_relaxed);
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lock_count_to_restore = 0;
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previous_mode = Mode::Unlocked;
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break;
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}
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default:
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VERIFY_NOT_REACHED();
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}
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m_queue.wake_one();
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return previous_mode;
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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_from_critical();
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}
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}
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#if LOCK_DEBUG
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void Lock::restore_lock(Mode mode, u32 lock_count)
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{
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return restore_lock("unknown", 0, mode, lock_count);
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}
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void Lock::restore_lock(const char* file, int line, Mode mode, u32 lock_count)
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#else
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void Lock::restore_lock(Mode mode, u32 lock_count)
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#endif
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{
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VERIFY(mode != Mode::Unlocked);
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VERIFY(lock_count > 0);
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VERIFY(!Processor::current().in_irq());
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auto current_thread = Thread::current();
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ScopedCritical critical; // in case we're not in a critical section already
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for (;;) {
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if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
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switch (mode) {
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case Mode::Exclusive: {
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auto expected_mode = Mode::Unlocked;
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if (!m_mode.compare_exchange_strong(expected_mode, Mode::Exclusive))
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break;
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dbgln_if(LOCK_RESTORE_DEBUG, "Lock::restore_lock @ {}: restoring {} with lock count {}, was unlocked", this, mode_to_string(mode), lock_count);
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VERIFY(m_times_locked == 0);
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m_times_locked = lock_count;
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VERIFY(!m_holder);
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VERIFY(m_shared_holders.is_empty());
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m_holder = current_thread;
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m_queue.should_block(true);
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m_lock.store(false, AK::memory_order_release);
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#if LOCK_DEBUG
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m_holder->holding_lock(*this, (int)lock_count, file, line);
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#endif
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return;
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}
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case Mode::Shared: {
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auto expected_mode = Mode::Unlocked;
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if (!m_mode.compare_exchange_strong(expected_mode, Mode::Shared) && expected_mode != Mode::Shared)
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break;
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dbgln_if(LOCK_RESTORE_DEBUG, "Lock::restore_lock @ {}: restoring {} with lock count {}, was {}",
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this, mode_to_string(mode), lock_count, mode_to_string(expected_mode));
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VERIFY(expected_mode == Mode::Shared || m_times_locked == 0);
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m_times_locked += lock_count;
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VERIFY(!m_holder);
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VERIFY((expected_mode == Mode::Unlocked) == m_shared_holders.is_empty());
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auto set_result = m_shared_holders.set(current_thread, lock_count);
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// There may be other shared lock holders already, but we should not have an entry yet
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VERIFY(set_result == AK::HashSetResult::InsertedNewEntry);
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m_queue.should_block(true);
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m_lock.store(false, AK::memory_order_release);
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#if LOCK_DEBUG
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m_holder->holding_lock(*this, (int)lock_count, file, line);
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#endif
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return;
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}
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default:
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VERIFY_NOT_REACHED();
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}
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m_lock.store(false, AK::memory_order_relaxed);
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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_from_critical();
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}
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}
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void Lock::clear_waiters()
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{
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VERIFY(m_mode != Mode::Shared);
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m_queue.wake_all();
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}
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}
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