ExecutionContext.cc

/*
 * Copyright (c) 2026, Pedigree Developers
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted.
 */
 
#include "pedigree/kernel/Log.h"
#include "pedigree/kernel/process/ExecutionContext.h"
#include "pedigree/kernel/process/Thread.h"
#include "pedigree/kernel/processor/Processor.h"
#include "pedigree/kernel/processor/ProcessorInformation.h"
 
ExecutionContextGuard::ExecutionContextGuard(ExecutionContext context)
    : m_Thread(nullptr), m_StateLevel(0), m_Previous(ExecutionContext::AtomicThread), m_Cleanup() {
  Thread* thread = Processor::information().getCurrentThread();
  if (!thread) {
    return;
  }
 
  const bool interruptsWereEnabled = Processor::getInterrupts();
  Processor::setInterrupts(false);
 
  m_StateLevel = __atomic_load_n(&thread->m_nStateLevel, __ATOMIC_ACQUIRE);
  m_Previous = thread->m_StateLevels[m_StateLevel].m_ExecutionContext.current();
 
  // Publish abandonment cleanup before changing the classification. A
  // nested fault can therefore never leave a reused Thread state labelled
  // as an IRQ context.
  thread->armAtomicStateCleanup(m_Cleanup, abandon, this);
  m_Thread = thread;
  thread->m_StateLevels[m_StateLevel].m_ExecutionContext.enter(context);
 
  Processor::setInterrupts(interruptsWereEnabled);
}
 
ExecutionContextGuard::~ExecutionContextGuard() {
  Thread* thread = m_Thread;
  if (!thread) {
    return;
  }
 
  const bool interruptsWereEnabled = Processor::getInterrupts();
  Processor::setInterrupts(false);
  restore();
  thread->disarmAtomicStateCleanup(m_Cleanup);
  Processor::setInterrupts(interruptsWereEnabled);
}
 
void ExecutionContextGuard::abandon(void* context) {
  ExecutionContextGuard* guard = reinterpret_cast<ExecutionContextGuard*>(context);
  if (guard) {
    guard->restore();
  }
}
 
void ExecutionContextGuard::restore() {
  if (!m_Thread) {
    return;
  }
 
  if (m_StateLevel >= MAX_NESTED_EVENTS) {
    FATAL_NOLOCK("Execution-context cleanup recorded an invalid state level");
    return;
  }
 
  m_Thread->m_StateLevels[m_StateLevel].m_ExecutionContext.restore(m_Previous);
  m_Thread = nullptr;
}