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Remove the activation lock and use RCU to protect PT removal

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This commit is contained in:
Zhang Junyang
2025-03-23 21:15:18 +08:00
committed by Tate, Hongliang Tian
parent d873e121ff
commit 5b7637eac3
6 changed files with 71 additions and 161 deletions
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20
ostd/src/mm/page_table/mod.rs
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@ -14,6 +14,8 @@ use super::{
};
use crate::{
arch::mm::{PageTableEntry, PagingConsts},
cpu::PinCurrentCpu,
task::disable_preempt,
util::marker::SameSizeAs,
Pod,
};
@ -99,22 +101,20 @@ impl PageTable<UserMode> {
}
/// Clear the page table.
///
/// # Safety
///
/// The caller must ensure that:
/// 1. No other cursors are accessing the page table.
/// 2. No other CPUs activates the page table.
pub(in crate::mm) unsafe fn clear(&self) {
let _guard = crate::task::disable_preempt();
pub(super) fn clear<G: PinCurrentCpu>(&self, flusher: &mut super::tlb::TlbFlusher<'_, G>) {
let _guard = disable_preempt();
let mut root_node = self.root.lock();
const NR_PTES_PER_NODE: usize = nr_subpage_per_huge::<PagingConsts>();
for i in 0..NR_PTES_PER_NODE / 2 {
let mut root_entry = root_node.entry(i);
if !root_entry.is_none() {
let old = root_entry.replace(Child::None);
// Since no others are accessing the old child, dropping it is fine.
drop(old);
if let Child::PageTable(pt) = old {
flusher
.issue_tlb_flush_with(crate::mm::tlb::TlbFlushOp::All, pt.clone().into());
// There may be other cursors accessing the old child, delay it with RCU.
let _ = crate::sync::RcuDrop::new(pt);
}
}
}
}