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fix(procfs): drop stale /proc/<pid> entries after reap #1819

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fix(procfs): drop stale /proc/<pid> entries after reap #1819

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4 changes: 4 additions & 0 deletions kernel/src/filesystem/procfs/pid/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,10 @@ impl DirOps for PidDirOps {
Some((cred.euid.data(), cred.egid.data()))
}

fn validate_child(&self, _child: &dyn IndexNode) -> bool {
ProcessManager::find(self.pid).is_some()
}

fn lookup_child(
&self,
dir: &ProcDir<Self>,
Expand Down
39 changes: 23 additions & 16 deletions kernel/src/filesystem/procfs/root.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,22 +85,20 @@ impl DirOps for RootDirOps {
) -> Result<Arc<dyn IndexNode>, SystemError> {
// 首先检查是否是 PID 目录
if let Ok(pid) = name.parse::<RawPid>() {
// 检查进程是否存在
if ProcessManager::find(pid).is_some() {
let mut cached_children = dir.cached_children().write();

// 检查缓存中是否已存在
if let Some(child) = cached_children.get(name) {
return Ok(child.clone());
}

// 创建新的 PID 目录（只传递 PID，不传递进程引用）
let inode = PidDirOps::new_inode(pid, dir.self_ref_weak().clone());
cached_children.insert(name.to_string(), inode.clone());
return Ok(inode);
} else {
let mut cached_children = dir.cached_children().write();

if ProcessManager::find(pid).is_none() {
cached_children.remove(name);
return Err(SystemError::ENOENT);
Comment on lines +90 to 92
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@chatgpt-codex-connector chatgpt-codex-connector bot Mar 17, 2026

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P1 Badge Validate cached /proc/ entries before returning them

ProcDir::find returns a cached child immediately unless validate_child rejects it (see template/dir.rs), but RootDirOps still uses the default validator, so cached /proc/<pid> entries bypass this new existence check entirely. In practice, if a PID directory was cached before reap, later lookups can still resolve that stale inode without entering this lookup_child path, so /proc/<pid> may remain visible until a separate readdir triggers cache pruning.

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}

if let Some(child) = cached_children.get(name) {
return Ok(child.clone());
}

let inode = PidDirOps::new_inode(pid, dir.self_ref_weak().clone());
cached_children.insert(name.to_string(), inode.clone());
return Ok(inode);
}

// 查找静态条目
Expand Down Expand Up @@ -132,8 +130,17 @@ impl DirOps for RootDirOps {
// 获取缓存写锁并填充
let mut cached_children = dir.cached_children().write();

// 填充进程目录（只传递 PID）
for pid in pid_list {
// 先删除已经失效的 PID 目录缓存
cached_children.retain(|name, _| {
if let Ok(pid) = name.parse::<RawPid>() {
pid_list.contains(&pid)
Comment on lines +134 to +136
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@chatgpt-codex-connector chatgpt-codex-connector bot Mar 17, 2026

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P2 Badge Avoid quadratic PID cache pruning in /proc readdir

This cache cleanup performs pid_list.contains(&pid) inside retain, making populate_children() O(number_of_cached_entries × number_of_pids). On systems with many tasks, each /proc directory listing can become disproportionately expensive while holding the cache write lock, causing avoidable latency spikes; converting pid_list to a set before retain would keep pruning linear.

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} else {
true
}
});

// 再填充当前仍存在的 PID 目录
for pid in pid_list.iter().copied() {
cached_children
.entry(pid.to_string())
.or_insert_with(|| PidDirOps::new_inode(pid, dir.self_ref_weak().clone()));
Expand Down
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