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Fix both the preempt count atomicity and the CPU-local init problem

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This commit is contained in:
Zhang Junyang
2024-07-19 13:23:28 +00:00
committed by Tate, Hongliang Tian
parent 00b9bf9610
commit 3ae884081f
6 changed files with 173 additions and 49 deletions
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45
ostd/src/cpu/cpu_local.rs
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@ -21,7 +21,7 @@
use core::ops::Deref;
use crate::{
cpu::{get_cpu_local_base, set_cpu_local_base},
arch,
trap::{disable_local, DisabledLocalIrqGuard},
};
@ -82,6 +82,13 @@ impl<T> !Clone for CpuLocal<T> {}
// other tasks as they should live on other CPUs to make sending useful.
impl<T> !Send for CpuLocal<T> {}
// A check to ensure that the CPU-local object is never accessed before the
// initialization for all CPUs.
#[cfg(debug_assertions)]
use core::sync::atomic::{AtomicBool, Ordering};
#[cfg(debug_assertions)]
static IS_INITIALIZED: AtomicBool = AtomicBool::new(false);
impl<T> CpuLocal<T> {
/// Initialize a CPU-local object.
///
@ -115,6 +122,11 @@ impl<T> CpuLocal<T> {
/// This function calculates the virtual address of the CPU-local object based on the per-
/// cpu base address and the offset in the BSP.
fn get(&self) -> *const T {
// CPU-local objects should be initialized before being accessed. It should be ensured
// by the implementation of OSTD initialization.
#[cfg(debug_assertions)]
debug_assert!(IS_INITIALIZED.load(Ordering::Relaxed));
let offset = {
let bsp_va = self as *const _ as usize;
let bsp_base = __cpu_local_start as usize;
@ -124,7 +136,7 @@ impl<T> CpuLocal<T> {
bsp_va - bsp_base as usize
};
let local_base = get_cpu_local_base() as usize;
let local_base = arch::cpu::local::get_base() as usize;
let local_va = local_base + offset;
// A sanity check about the alignment.
@ -170,6 +182,24 @@ impl<T> Deref for CpuLocalDerefGuard<'_, T> {
}
}
/// Sets the base address of the CPU-local storage for the bootstrap processor.
///
/// It should be called early to let [`crate::task::disable_preempt`] work,
/// which needs to update a CPU-local preempt lock count. Otherwise it may
/// panic when calling [`crate::task::disable_preempt`].
///
/// # Safety
///
/// It should be called only once and only on the BSP.
pub(crate) unsafe fn early_init_bsp_local_base() {
let start_base_va = __cpu_local_start as usize as u64;
// SAFETY: The base to be set is the start of the `.cpu_local` section,
// where accessing the CPU-local objects have defined behaviors.
unsafe {
arch::cpu::local::set_base(start_base_va);
}
}
/// Initializes the CPU local data for the bootstrap processor (BSP).
///
/// # Safety
@ -179,9 +209,14 @@ impl<T> Deref for CpuLocalDerefGuard<'_, T> {
/// It must be guaranteed that the BSP will not access local data before
/// this function being called, otherwise copying non-constant values
/// will result in pretty bad undefined behavior.
pub unsafe fn init_on_bsp() {
let start_base_va = __cpu_local_start as usize as u64;
set_cpu_local_base(start_base_va);
pub(crate) unsafe fn init_on_bsp() {
// TODO: allocate the pages for application processors and copy the
// CPU-local objects to the allocated pages.
#[cfg(debug_assertions)]
{
IS_INITIALIZED.store(true, Ordering::Relaxed);
}
}
// These symbols are provided by the linker script.