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https://github.com/SerenityOS/serenity
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Kernel: Protect Mutex's thread lists with a spinlock
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8296dd9955
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b28beb691e
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@ -206,16 +206,21 @@ void Mutex::block(Thread& current_thread, Mode mode, SpinlockLocker<Spinlock>& l
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{
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if constexpr (LOCK_IN_CRITICAL_DEBUG)
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VERIFY_INTERRUPTS_ENABLED();
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auto& blocked_thread_list = thread_list_for_mode(mode);
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VERIFY(!blocked_thread_list.contains(current_thread));
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blocked_thread_list.append(current_thread);
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m_blocked_thread_lists.with([&](auto& lists) {
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auto& list = lists.list_for_mode(mode);
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VERIFY(!list.contains(current_thread));
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list.append(current_thread);
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});
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dbgln_if(LOCK_TRACE_DEBUG, "Mutex::lock @ {} ({}) waiting...", this, m_name);
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current_thread.block(*this, lock, requested_locks);
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dbgln_if(LOCK_TRACE_DEBUG, "Mutex::lock @ {} ({}) waited", this, m_name);
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VERIFY(blocked_thread_list.contains(current_thread));
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blocked_thread_list.remove(current_thread);
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m_blocked_thread_lists.with([&](auto& lists) {
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auto& list = lists.list_for_mode(mode);
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VERIFY(list.contains(current_thread));
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list.remove(current_thread);
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});
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}
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void Mutex::unblock_waiters(Mode previous_mode)
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@ -223,41 +228,43 @@ void Mutex::unblock_waiters(Mode previous_mode)
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VERIFY(m_times_locked == 0);
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VERIFY(m_mode == Mode::Unlocked);
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if (m_blocked_threads_list_exclusive.is_empty() && m_blocked_threads_list_shared.is_empty())
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return;
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m_blocked_thread_lists.with([&](auto& lists) {
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if (lists.exclusive.is_empty() && lists.shared.is_empty())
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return;
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auto unblock_shared = [&]() {
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if (m_blocked_threads_list_shared.is_empty())
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return false;
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m_mode = Mode::Shared;
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for (auto& thread : m_blocked_threads_list_shared) {
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auto requested_locks = thread.unblock_from_mutex(*this);
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m_shared_holders += requested_locks;
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auto unblock_shared = [&]() {
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if (lists.shared.is_empty())
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return false;
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m_mode = Mode::Shared;
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for (auto& thread : lists.shared) {
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auto requested_locks = thread.unblock_from_mutex(*this);
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m_shared_holders += requested_locks;
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#if LOCK_SHARED_UPGRADE_DEBUG
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auto set_result = m_shared_holders_map.set(&thread, requested_locks);
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VERIFY(set_result == AK::HashSetResult::InsertedNewEntry);
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auto set_result = m_shared_holders_map.set(&thread, requested_locks);
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VERIFY(set_result == AK::HashSetResult::InsertedNewEntry);
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#endif
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m_times_locked += requested_locks;
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}
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return true;
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};
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auto unblock_exclusive = [&]() {
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if (auto* next_exclusive_thread = m_blocked_threads_list_exclusive.first()) {
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m_mode = Mode::Exclusive;
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m_times_locked = next_exclusive_thread->unblock_from_mutex(*this);
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m_holder = next_exclusive_thread;
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m_times_locked += requested_locks;
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}
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return true;
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}
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return false;
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};
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};
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auto unblock_exclusive = [&]() {
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if (auto* next_exclusive_thread = lists.exclusive.first()) {
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m_mode = Mode::Exclusive;
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m_times_locked = next_exclusive_thread->unblock_from_mutex(*this);
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m_holder = next_exclusive_thread;
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return true;
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}
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return false;
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};
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if (previous_mode == Mode::Exclusive) {
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if (!unblock_shared())
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unblock_exclusive();
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} else {
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if (!unblock_exclusive())
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unblock_shared();
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}
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if (previous_mode == Mode::Exclusive) {
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if (!unblock_shared())
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unblock_exclusive();
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} else {
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if (!unblock_exclusive())
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unblock_shared();
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}
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});
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}
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auto Mutex::force_unlock_exclusive_if_locked(u32& lock_count_to_restore) -> Mode
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@ -72,12 +72,6 @@ public:
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private:
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using BlockedThreadList = IntrusiveList<&Thread::m_blocked_threads_list_node>;
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ALWAYS_INLINE BlockedThreadList& thread_list_for_mode(Mode mode)
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{
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VERIFY(mode == Mode::Exclusive || mode == Mode::Shared);
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return mode == Mode::Exclusive ? m_blocked_threads_list_exclusive : m_blocked_threads_list_shared;
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}
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void block(Thread&, Mode, SpinlockLocker<Spinlock>&, u32);
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void unblock_waiters(Mode);
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@ -96,8 +90,17 @@ private:
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RefPtr<Thread> m_holder;
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size_t m_shared_holders { 0 };
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BlockedThreadList m_blocked_threads_list_exclusive;
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BlockedThreadList m_blocked_threads_list_shared;
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struct BlockedThreadLists {
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BlockedThreadList exclusive;
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BlockedThreadList shared;
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ALWAYS_INLINE BlockedThreadList& list_for_mode(Mode mode)
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{
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VERIFY(mode == Mode::Exclusive || mode == Mode::Shared);
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return mode == Mode::Exclusive ? exclusive : shared;
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}
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};
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SpinlockProtected<BlockedThreadLists> m_blocked_thread_lists;
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mutable Spinlock m_lock;
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