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Kernel/SMP: Make entering/leaving critical sections multi-processor safe
By making these functions static we close a window where we could get preempted after calling Processor::current() and move to another processor. Co-authored-by: Tom <tomut@yahoo.com>
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369e3da6a2
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11 changed files with 82 additions and 53 deletions
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@ -613,7 +613,7 @@ void Processor::exit_trap(TrapFrame& trap)
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// to trigger a context switch while we're executing this function
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// See the comment at the end of the function why we don't use
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// ScopedCritical here.
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m_in_critical++;
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m_in_critical = m_in_critical + 1;
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VERIFY(m_in_irq >= trap.prev_irq_level);
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m_in_irq = trap.prev_irq_level;
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@ -646,11 +646,13 @@ void Processor::exit_trap(TrapFrame& trap)
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current_thread->update_time_scheduled(Scheduler::current_time(), true, false);
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}
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VERIFY_INTERRUPTS_DISABLED();
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// Leave the critical section without actually enabling interrupts.
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// We don't want context switches to happen until we're explicitly
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// triggering a switch in check_invoke_scheduler.
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auto new_critical = m_in_critical.fetch_sub(1) - 1;
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if (!m_in_irq && !new_critical)
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m_in_critical = m_in_critical - 1;
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if (!m_in_irq && !m_in_critical)
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check_invoke_scheduler();
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}
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@ -730,7 +732,7 @@ ProcessorMessage& Processor::smp_get_from_pool()
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u32 Processor::smp_wake_n_idle_processors(u32 wake_count)
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{
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VERIFY(Processor::current().in_critical());
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VERIFY(Processor::in_critical());
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VERIFY(wake_count > 0);
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if (!s_smp_enabled)
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return 0;
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@ -1311,7 +1313,7 @@ void Processor::assume_context(Thread& thread, FlatPtr flags)
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Scheduler::prepare_after_exec();
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// in_critical() should be 2 here. The critical section in Process::exec
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// and then the scheduler lock
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VERIFY(Processor::current().in_critical() == 2);
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VERIFY(Processor::in_critical() == 2);
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do_assume_context(&thread, flags);
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