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Kernel: Allow Lock to block from BlockCondition

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This enables the Lock class to block a thread even while the thread is
working on a BlockCondition. A thread can still only be either blocked
by a Lock or a BlockCondition.

This also establishes a linked list of threads that are blocked by a
Lock and unblocking directly unlocks threads and wakes them directly.
This commit is contained in:
Tom 2021-07-10 10:23:16 -06:00 • committed by Andreas Kling
parent d9fb93c5ce
commit 026ffa343d
8 changed files with 442 additions and 267 deletions
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23
Kernel/Lock.h
View file

@ -17,6 +17,8 @@
namespace Kernel {
class Lock {
friend class Thread;
AK_MAKE_NONCOPYABLE(Lock);
AK_MAKE_NONMOVABLE(Lock);
@ -40,7 +42,6 @@ public:
void unlock();
[[nodiscard]] Mode force_unlock_if_locked(u32&);
[[nodiscard]] bool is_locked() const { return m_mode != Mode::Unlocked; }
void clear_waiters();
[[nodiscard]] const char* name() const { return m_name; }
@ -59,10 +60,19 @@ public:
}
private:
Atomic<bool> m_lock { false };
typedef IntrusiveList<Thread, RawPtr<Thread>, &Thread::m_blocked_threads_list_node> BlockedThreadList;
ALWAYS_INLINE BlockedThreadList& thread_list_for_mode(Mode mode)
{
VERIFY(mode == Mode::Exclusive || mode == Mode::Shared);
return mode == Mode::Exclusive ? m_blocked_threads_list_exclusive : m_blocked_threads_list_shared;
}
void block(Thread&, Mode, ScopedSpinLock<SpinLock<u8>>&, u32);
void unblock_waiters(Mode);
const char* m_name { nullptr };
WaitQueue m_queue;
Atomic<Mode, AK::MemoryOrder::memory_order_relaxed> m_mode { Mode::Unlocked };
Mode m_mode { Mode::Unlocked };
// When locked exclusively, only the thread already holding the lock can
// lock it again. When locked in shared mode, any thread can do that.
@ -75,6 +85,11 @@ private:
// lock.
RefPtr<Thread> m_holder;
HashMap<Thread*, u32> m_shared_holders;
BlockedThreadList m_blocked_threads_list_exclusive;
BlockedThreadList m_blocked_threads_list_shared;
SpinLock<u8> m_lock;
};
class Locker {