diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3c15efd3b..06c73bc6c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -5,12 +5,41 @@ on:
     - main
 concurrency: dev-${{ github.ref }}
 jobs:
-  windows:
+  build-windows:
     name: Build
     uses: ./.github/workflows/ci-windows.yml
-  linux:
+  build-linux:
     name: Build
     uses: ./.github/workflows/ci-linux.yml
-  mac:
+  build-mac:
     name: Build
     uses: ./.github/workflows/ci-mac.yml
+  housekeep:
+    name: Housekeep
+    runs-on: ubuntu-latest
+    steps:
+    - name: Update PRs
+      run: |
+        import { Octokit } from 'octokit';
+
+        const octokit = new Octokit({ auth: '${{ secrets.GITHUB_TOKEN }}' });
+        const owner = '${{ github.event.repository.owner.login }}';
+        const repo = '${{ github.event.repository.name }}';
+        const resp = await octokit.request('GET /repos/{owner}/{repo}/pulls', {
+          owner,
+          repo,
+          base: '${{ github.ref_name }}',
+          sort: 'updated',
+          direction: 'desc',
+          per_page: 100,
+        });
+
+        for (const pull of resp.data) {
+          await octokit.request('POST /repos/{owner}/{repo}/issues/{issue_number}/labels', {
+            owner,
+            repo,
+            issue_number: pull.number,
+            labels: ['B-out-of-date'],
+          });
+        }
+      shell: node --input-type=module {0}
diff --git a/src/kernel/src/errno.rs b/src/kernel/src/errno.rs
index c569feb12..87d404f65 100644
--- a/src/kernel/src/errno.rs
+++ b/src/kernel/src/errno.rs
@@ -14,7 +14,7 @@ macro_rules! error_numbers {
             };
         )*
 
-        pub fn strerror_impl(num: NonZeroI32) -> &'static str {
+        fn strerror_impl(num: NonZeroI32) -> &'static str {
             match num {
                 $( $name => $desc, )*
                 _ => todo!("strerror {num}", num = num.get()),
diff --git a/src/kernel/src/signal/mod.rs b/src/kernel/src/signal/mod.rs
index 5fc06c878..9b32b2a04 100644
--- a/src/kernel/src/signal/mod.rs
+++ b/src/kernel/src/signal/mod.rs
@@ -11,7 +11,7 @@ mod set;
 pub struct Signal(NonZeroI32);
 
 impl Signal {
-    pub fn new(raw: i32) -> Option<Self> {
+    pub const fn new(raw: i32) -> Option<Self> {
         match raw {
             1..=SIG_MAXSIG => Some(Signal(unsafe { NonZeroI32::new_unchecked(raw) })),
             _ => None,
@@ -27,13 +27,13 @@ macro_rules! signals {
     ($($name:ident($num:expr),)*) => {
         $(
             #[allow(dead_code)]
-            pub const $name: Signal = Signal(unsafe {
-                assert!($num > 0 && $num <= SIG_MAXSIG);
-                NonZeroI32::new_unchecked($num)
-            });
+            pub const $name: Signal = match Signal::new($num) {
+                Some(sig) => sig,
+                None => panic!(),
+            };
         )*
 
-        pub fn strsignal_impl(sig: Signal) -> Cow<'static, str> {
+        fn strsignal_impl(sig: Signal) -> Cow<'static, str> {
             match sig.0.get() {
                 $( $num => Cow::Borrowed(stringify!($name)), )*
                 _ => format!("{sig}", sig = sig.get()).into(),
@@ -43,8 +43,8 @@ macro_rules! signals {
 }
 
 // List of PS4 signals. The value must be the same as PS4 kernel.
-#[rustfmt::skip]
-signals!(
+
+signals! {
     SIGHUP(1),
     SIGINT(2),
     SIGQUIT(3),
@@ -78,7 +78,7 @@ signals!(
     SIGUSR2(31),
     SIGTHR(32),
     SIGNONE(128),
-);
+}
 
 pub fn strsignal(sig: Signal) -> Cow<'static, str> {
     // This function is generated inside the macro `signals!`.
@@ -109,10 +109,9 @@ impl Iterator for SignalIter {
     type Item = Signal;
 
     fn next(&mut self) -> Option<Self::Item> {
-        if self.current <= SIG_MAXSIG {
-            let signal = Signal(unsafe { NonZeroI32::new_unchecked(self.current) });
+        if let Some(sig) = Signal::new(self.current) {
             self.current += 1;
-            Some(signal)
+            Some(sig)
         } else {
             None
         }
diff --git a/src/kernel/src/signal/set.rs b/src/kernel/src/signal/set.rs
index e9bef9cb8..0d52a2266 100644
--- a/src/kernel/src/signal/set.rs
+++ b/src/kernel/src/signal/set.rs
@@ -33,7 +33,7 @@ impl SignalSet {
     /// An implementation of `_SIG_WORD`.
     fn word(s: Signal) -> usize {
         // This is safe because `Signal` is guaranteed to be non-negative.
-        unsafe { (Self::idx(s) >> 5).try_into().unwrap_unchecked() }
+        unsafe { (Self::idx(s) >> 5).try_into().unwrap() }
     }
 
     /// An implementation of `_SIG_BIT`.