Kernel: Rewrite the whole scheduler and re-architecture SMP handling

Change Semaphore -> ThreadBlocker
  This was not a semaphore, I just named it one because I didn't know
  what semaphore was. I have meant to change this sooner, but it was in
  no way urgent :D

Implement SMP events. Processors can now be sent SMP events through
IPIs. SMP events can be sent either to a single processor or broadcasted
to every processor.

PageTable::{map_page,map_range,unmap_page,unmap_range}() now send SMP
event to invalidate TLB caches for the changed pages.

Scheduler no longer uses a global run queue. Each processor has its own
scheduler that keeps track of the load on the processor. Once every
second schedulers do load balancing. Schedulers have no access to other
processors' schedulers, they just see approximate loads. If scheduler
decides that it has too much load, it will send a thread to another
processor through a SMP event.

Schedulers are currently run using the timer interrupt on BSB. This
should be not the case, and each processor should use its LAPIC timer
for interrupts. There is no reason to broadcast SMP event to all
processors when BSB gets timer interrupt.

Old scheduler only achieved 20% idle load on qemu. That was probably a
very inefficient implementation. This new scheduler seems to average
around 1% idle load. This is much closer to what I would expect. On my
own laptop idle load seems to be only around 0.5% on each processor.

kernel/include/kernel/Networking/ARPTable.h

@@ -5,7 +5,7 @@
 #include <BAN/UniqPtr.h>
 #include <kernel/Networking/NetworkInterface.h>
 #include <kernel/Process.h>
-#include <kernel/Semaphore.h>
+#include <kernel/ThreadBlocker.h>
 
 namespace Kernel
 {
@@ -58,7 +58,7 @@ namespace Kernel
 
 		Process*									m_process = nullptr;
 		BAN::CircularQueue<PendingArpPacket, 128>	m_pending_packets;
-		Semaphore									m_pending_semaphore;
+		ThreadBlocker									m_pending_thread_blocker;
 
 		friend class BAN::UniqPtr<ARPTable>;
 	};

kernel/include/kernel/Networking/IPv4Layer.h

@@ -77,7 +77,7 @@ namespace Kernel
 		static constexpr size_t pending_packet_buffer_size = 128 * PAGE_SIZE;
 		BAN::UniqPtr<VirtualRange>					m_pending_packet_buffer;
 		BAN::CircularQueue<PendingIPv4Packet, 128>	m_pending_packets;
-		Semaphore									m_pending_semaphore;
+		ThreadBlocker									m_pending_thread_blocker;
 		SpinLock									m_pending_lock;
 		size_t										m_pending_total_size { 0 };
 

kernel/include/kernel/Networking/TCPSocket.h

@@ -7,7 +7,7 @@
 #include <kernel/Networking/NetworkInterface.h>
 #include <kernel/Networking/NetworkSocket.h>
 #include <kernel/Process.h>
-#include <kernel/Semaphore.h>
+#include <kernel/ThreadBlocker.h>
 
 namespace Kernel
 {
@@ -161,7 +161,7 @@ namespace Kernel
 
 		uint64_t m_time_wait_start_ms { 0 };
 
-		Semaphore m_semaphore;
+		ThreadBlocker m_thread_blocker;
 
 		RecvWindowInfo m_recv_window;
 		SendWindowInfo m_send_window;

kernel/include/kernel/Networking/UDPSocket.h

@@ -6,7 +6,7 @@
 #include <kernel/Memory/VirtualRange.h>
 #include <kernel/Networking/NetworkInterface.h>
 #include <kernel/Networking/NetworkSocket.h>
-#include <kernel/Semaphore.h>
+#include <kernel/ThreadBlocker.h>
 
 namespace Kernel
 {
@@ -57,7 +57,7 @@ namespace Kernel
 		BAN::CircularQueue<PacketInfo, 32>	m_packets;
 		size_t								m_packet_total_size { 0 };
 		SpinLock							m_packet_lock;
-		Semaphore							m_packet_semaphore;
+		ThreadBlocker							m_packet_thread_blocker;
 
 		friend class BAN::RefPtr<UDPSocket>;
 	};

kernel/include/kernel/Networking/UNIX/Socket.h

@@ -48,7 +48,7 @@ namespace Kernel
 			mutable BAN::Atomic<bool>					target_closed { false };
 			BAN::WeakPtr<UnixDomainSocket>				connection;
 			BAN::Queue<BAN::RefPtr<UnixDomainSocket>>	pending_connections;
-			Semaphore									pending_semaphore;
+			ThreadBlocker									pending_thread_blocker;
 			SpinLock									pending_lock;
 		};
 
@@ -67,7 +67,7 @@ namespace Kernel
 		size_t							m_packet_size_total { 0 };
 		BAN::UniqPtr<VirtualRange>		m_packet_buffer;
 		SpinLock						m_packet_lock;
-		Semaphore						m_packet_semaphore;
+		ThreadBlocker						m_packet_thread_blocker;
 
 		friend class BAN::RefPtr<UnixDomainSocket>;
 	};