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Kernel/SMP: Change critical sections to not disable interrupts

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Leave interrupts enabled so that we can still process IRQs. Critical
sections should only prevent preemption by another thread.

Co-authored-by: Tom <tomut@yahoo.com>
This commit is contained in:
Andreas Kling 2021-08-10 01:56:21 +02:00
parent 364134ad4b
commit 0a02496f04
6 changed files with 42 additions and 60 deletions
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41
Kernel/Arch/x86/Processor.h
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@ -339,17 +339,13 @@ public:
write_gs_ptr(__builtin_offsetof(Processor, m_in_critical), critical);
}
ALWAYS_INLINE static void enter_critical(u32& prev_flags)
ALWAYS_INLINE static void enter_critical()
{
prev_flags = cpu_flags();
cli();
// NOTE: Up until this point we *could* have been preempted.
// Now interrupts are disabled, so calling current() is safe.
AK::atomic_fetch_add(&current().m_in_critical, 1u, AK::MemoryOrder::memory_order_relaxed);
write_gs_ptr(__builtin_offsetof(Processor, m_in_critical), in_critical() + 1);
}
private:
ALWAYS_INLINE void do_leave_critical(u32 prev_flags)
ALWAYS_INLINE void do_leave_critical()
{
VERIFY(m_in_critical > 0);
if (m_in_critical == 1) {
@ -363,52 +359,31 @@ private:
} else {
m_in_critical = m_in_critical - 1;
}
if (prev_flags & 0x200)
sti();
else
cli();
}
public:
ALWAYS_INLINE static void leave_critical(u32 prev_flags)
ALWAYS_INLINE static void leave_critical()
{
cli(); // Need to prevent IRQs from interrupting us here!
// NOTE: Up until this point we *could* have been preempted!
// Now interrupts are disabled, so calling current() is safe
current().do_leave_critical(prev_flags);
current().do_leave_critical();
}
ALWAYS_INLINE static u32 clear_critical(u32& prev_flags, bool enable_interrupts)
ALWAYS_INLINE static u32 clear_critical()
{
cli();
// NOTE: Up until this point we *could* have been preempted!
// Now interrupts are disabled, so calling current() is safe
// This doesn't have to be atomic, and it's also fine if we
// were to be preempted in between these steps (which should
// not happen due to the cli call), but if we moved to another
// processors m_in_critical would move along with us
auto prev_critical = read_gs_ptr(__builtin_offsetof(Processor, m_in_critical));
auto prev_critical = in_critical();
write_gs_ptr(__builtin_offsetof(Processor, m_in_critical), 0);
auto& proc = current();
if (!proc.m_in_irq)
proc.check_invoke_scheduler();
if (enable_interrupts || (prev_flags & 0x200))
sti();
return prev_critical;
}
ALWAYS_INLINE static void restore_critical(u32 prev_critical, u32 prev_flags)
ALWAYS_INLINE static void restore_critical(u32 prev_critical)
{
// NOTE: This doesn't have to be atomic, and it's also fine if we
// get preempted in between these steps. If we move to another
// processors m_in_critical will move along with us. And if we
// are preempted, we would resume with the same flags.
write_gs_ptr(__builtin_offsetof(Processor, m_in_critical), prev_critical);
VERIFY(!prev_critical || !(prev_flags & 0x200));
if (prev_flags & 0x200)
sti();
else
cli();
}
ALWAYS_INLINE static u32 in_critical()