Kernel: Make m_halt_requested an atomic variable

We need to make sure the change to this variable is visible to all
processors instantly.

Kernel/Arch/i386/CPU.cpp

@@ -1819,11 +1819,11 @@ bool Processor::smp_process_pending_messages()
  }
  }
 
- if (m_halt_requested)
+ if (m_halt_requested.load(AK::MemoryOrder::memory_order_relaxed))
  halt_this();
  }
  did_process = true;
- } else if (m_halt_requested) {
+ } else if (m_halt_requested.load(AK::MemoryOrder::memory_order_relaxed)) {
  halt_this();
  }
 
@@ -1876,7 +1876,7 @@ void Processor::smp_broadcast_message(ProcessorMessage& msg, bool async)
  // We need to check here if another processor may have requested
  // us to halt before this message could be delivered. Otherwise
  // we're just spinning the CPU because msg.refs will never drop to 0.
- if (cur_proc.m_halt_requested)
+ if (cur_proc.m_halt_requested.load(AK::MemoryOrder::memory_order_relaxed))
  halt_this();
  }
 
@@ -1918,7 +1918,7 @@ void Processor::smp_broadcast_halt()
  // by being out of memory and we might not be able to get a message
  for_each(
  [&](Processor& proc) -> IterationDecision {
- proc.m_halt_requested = true;
+ proc.m_halt_requested.store(true, AK::MemoryOrder::memory_order_release);
  return IterationDecision::Continue;
  });
 

Kernel/Arch/i386/CPU.h

@@ -724,7 +724,7 @@ class Processor {
 
  bool m_invoke_scheduler_async;
  bool m_scheduler_initialized;
- bool m_halt_requested;
+ Atomic<bool> m_halt_requested;
 
  DeferredCallEntry* m_pending_deferred_calls; // in reverse order
  DeferredCallEntry* m_free_deferred_call_pool_entry;