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Kernel: Specify default memory order for some non-synchronizing Atomics

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Tom 2021-01-03 16:58:50 -07:00 • committed by Andreas Kling
parent fb84f0ec9c
commit 901ef3f1c8
12 changed files with 44 additions and 43 deletions
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18
Kernel/Lock.cpp
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@ -55,13 +55,13 @@ void Lock::lock(Mode mode)
if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
do {
// FIXME: Do not add new readers if writers are queued.
auto current_mode = m_mode.load(AK::MemoryOrder::memory_order_relaxed);
Mode current_mode = m_mode;
switch (current_mode) {
case Mode::Unlocked: {
#ifdef LOCK_TRACE_DEBUG
dbg() << "Lock::lock @ " << this << ": acquire " << mode_to_string(mode) << ", currently unlocked";
#endif
m_mode.store(mode, AK::MemoryOrder::memory_order_relaxed);
m_mode = mode;
ASSERT(!m_holder);
ASSERT(m_shared_holders.is_empty());
if (mode == Mode::Exclusive) {
@ -140,7 +140,7 @@ void Lock::unlock()
ScopedCritical critical; // in case we're not in a critical section already
for (;;) {
if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
auto current_mode = m_mode.load(AK::MemoryOrder::memory_order_relaxed);
Mode current_mode = m_mode;
#ifdef LOCK_TRACE_DEBUG
if (current_mode == Mode::Shared)
dbg() << "Lock::unlock @ " << this << ": release " << mode_to_string(current_mode) << ", locks held: " << m_times_locked;
@ -177,7 +177,7 @@ void Lock::unlock()
if (m_times_locked == 0) {
ASSERT(current_mode == Mode::Exclusive ? !m_holder : m_shared_holders.is_empty());
m_mode.store(Mode::Unlocked, AK::MemoryOrder::memory_order_relaxed);
m_mode = Mode::Unlocked;
}
#ifdef LOCK_DEBUG
@ -218,7 +218,7 @@ auto Lock::force_unlock_if_locked(u32& lock_count_to_restore) -> Mode
ASSERT(m_times_locked > 0);
lock_count_to_restore = m_times_locked;
m_times_locked = 0;
m_mode.store(Mode::Unlocked, AK::MemoryOrder::memory_order_relaxed);
m_mode = Mode::Unlocked;
m_lock.store(false, AK::memory_order_release);
#ifdef LOCK_DEBUG
m_holder->holding_lock(*this, -(int)lock_count_to_restore);
@ -247,7 +247,7 @@ auto Lock::force_unlock_if_locked(u32& lock_count_to_restore) -> Mode
ASSERT(m_times_locked >= lock_count_to_restore);
m_times_locked -= lock_count_to_restore;
if (m_times_locked == 0)
m_mode.store(Mode::Unlocked, AK::MemoryOrder::memory_order_relaxed);
m_mode = Mode::Unlocked;
m_lock.store(false, AK::memory_order_release);
previous_mode = Mode::Shared;
break;
@ -290,7 +290,7 @@ void Lock::restore_lock(Mode mode, u32 lock_count)
switch (mode) {
case Mode::Exclusive: {
auto expected_mode = Mode::Unlocked;
if (!m_mode.compare_exchange_strong(expected_mode, Mode::Exclusive, AK::MemoryOrder::memory_order_relaxed))
if (!m_mode.compare_exchange_strong(expected_mode, Mode::Exclusive))
break;
#ifdef LOCK_RESTORE_DEBUG
dbg() << "Lock::restore_lock @ " << this << ": restoring " << mode_to_string(mode) << " with lock count " << lock_count << ", was unlocked";
@ -308,7 +308,7 @@ void Lock::restore_lock(Mode mode, u32 lock_count)
}
case Mode::Shared: {
auto expected_mode = Mode::Unlocked;
if (!m_mode.compare_exchange_strong(expected_mode, Mode::Shared, AK::MemoryOrder::memory_order_relaxed) && expected_mode != Mode::Shared)
if (!m_mode.compare_exchange_strong(expected_mode, Mode::Shared) && expected_mode != Mode::Shared)
break;
#ifdef LOCK_RESTORE_DEBUG
dbg() << "Lock::restore_lock @ " << this << ": restoring " << mode_to_string(mode) << " with lock count " << lock_count << ", was " << mode_to_string(expected_mode);
@ -339,7 +339,7 @@ void Lock::restore_lock(Mode mode, u32 lock_count)
void Lock::clear_waiters()
{
ASSERT(m_mode.load(AK::MemoryOrder::memory_order_relaxed) != Mode::Shared);
ASSERT(m_mode != Mode::Shared);
m_queue.wake_all();
}