riscv/src/critical_section.rs

use critical_section::{set_impl, Impl, RawRestoreState};

use crate::interrupt;
use crate::register::mstatus;

struct SingleHartCriticalSection;
set_impl!(SingleHartCriticalSection);

unsafe impl Impl for SingleHartCriticalSection {
    unsafe fn acquire() -> RawRestoreState {
        let mut mstatus: usize;
        core::arch::asm!("csrrci {}, 0x300, 0b100", out(reg) mstatus);
        core::mem::transmute::<_, mstatus::Mstatus>(mstatus).mie()
    }

    unsafe fn release(was_active: RawRestoreState) {
        // Only re-enable interrupts if they were enabled before the critical section.
        if was_active {
            interrupt::enable()
        }
    }
}