diff --git a/kernel/aster-nix/src/process/clone.rs b/kernel/aster-nix/src/process/clone.rs
index cf7a93e48..62de1bf53 100644
--- a/kernel/aster-nix/src/process/clone.rs
+++ b/kernel/aster-nix/src/process/clone.rs
@@ -175,8 +175,10 @@ fn clone_child_thread(parent_context: &UserContext, clone_args: CloneArgs) -> Re
     let sig_mask = {
         let current_thread = current_thread!();
         let current_posix_thread = current_thread.as_posix_thread().unwrap();
-        let sigmask = current_posix_thread.sig_mask().lock();
-        *sigmask
+        current_posix_thread
+            .sig_mask()
+            .load(Ordering::Relaxed)
+            .into()
     };
 
     let child_tid = allocate_tid();
@@ -258,8 +260,7 @@ fn clone_child_process(
     let child_sig_mask = {
         let current_thread = current_thread!();
         let posix_thread = current_thread.as_posix_thread().unwrap();
-        let sigmask = posix_thread.sig_mask().lock();
-        *sigmask
+        posix_thread.sig_mask().load(Ordering::Relaxed).into()
     };
 
     // inherit parent's nice value
diff --git a/kernel/aster-nix/src/process/posix_thread/builder.rs b/kernel/aster-nix/src/process/posix_thread/builder.rs
index cbce48e35..54002ab1c 100644
--- a/kernel/aster-nix/src/process/posix_thread/builder.rs
+++ b/kernel/aster-nix/src/process/posix_thread/builder.rs
@@ -9,7 +9,7 @@ use crate::{
     prelude::*,
     process::{
         posix_thread::name::ThreadName,
-        signal::{sig_mask::SigMask, sig_queues::SigQueues},
+        signal::{sig_mask::AtomicSigMask, sig_queues::SigQueues},
         Credentials, Process,
     },
     thread::{status::ThreadStatus, task, thread_table, Thread, Tid},
@@ -28,7 +28,7 @@ pub struct PosixThreadBuilder {
     thread_name: Option<ThreadName>,
     set_child_tid: Vaddr,
     clear_child_tid: Vaddr,
-    sig_mask: SigMask,
+    sig_mask: AtomicSigMask,
     sig_queues: SigQueues,
 }
 
@@ -42,7 +42,7 @@ impl PosixThreadBuilder {
             thread_name: None,
             set_child_tid: 0,
             clear_child_tid: 0,
-            sig_mask: SigMask::new_empty(),
+            sig_mask: AtomicSigMask::new_empty(),
             sig_queues: SigQueues::new(),
         }
     }
@@ -67,7 +67,7 @@ impl PosixThreadBuilder {
         self
     }
 
-    pub fn sig_mask(mut self, sig_mask: SigMask) -> Self {
+    pub fn sig_mask(mut self, sig_mask: AtomicSigMask) -> Self {
         self.sig_mask = sig_mask;
         self
     }
@@ -99,7 +99,7 @@ impl PosixThreadBuilder {
                 set_child_tid: Mutex::new(set_child_tid),
                 clear_child_tid: Mutex::new(clear_child_tid),
                 credentials,
-                sig_mask: Mutex::new(sig_mask),
+                sig_mask,
                 sig_queues,
                 sig_context: Mutex::new(None),
                 sig_stack: Mutex::new(None),
diff --git a/kernel/aster-nix/src/process/posix_thread/mod.rs b/kernel/aster-nix/src/process/posix_thread/mod.rs
index 4af180e55..32b52e299 100644
--- a/kernel/aster-nix/src/process/posix_thread/mod.rs
+++ b/kernel/aster-nix/src/process/posix_thread/mod.rs
@@ -2,12 +2,14 @@
 
 #![allow(dead_code)]
 
+use core::sync::atomic::Ordering;
+
 use aster_rights::{ReadOp, WriteOp};
 
 use super::{
     kill::SignalSenderIds,
     signal::{
-        sig_mask::{SigMask, SigSet},
+        sig_mask::{AtomicSigMask, SigMask, SigSet},
         sig_num::SigNum,
         sig_queues::SigQueues,
         signals::Signal,
@@ -55,7 +57,7 @@ pub struct PosixThread {
 
     // Signal
     /// Blocked signals
-    sig_mask: Mutex<SigMask>,
+    sig_mask: AtomicSigMask,
     /// Thread-directed sigqueue
     sig_queues: SigQueues,
     /// Signal handler ucontext address
@@ -90,7 +92,12 @@ impl PosixThread {
         &self.clear_child_tid
     }
 
-    pub fn sig_mask(&self) -> &Mutex<SigMask> {
+    /// Get the reference to the signal mask of the thread.
+    ///
+    /// Note that while this function offers mutable access to the signal mask,
+    /// it is not sound for callers other than the current thread to modify the
+    /// signal mask. They may only read the signal mask.
+    pub fn sig_mask(&self) -> &AtomicSigMask {
         &self.sig_mask
     }
 
@@ -101,14 +108,13 @@ impl PosixThread {
     /// Returns whether the thread has some pending signals
     /// that are not blocked.
     pub fn has_pending(&self) -> bool {
-        let blocked = *self.sig_mask().lock();
+        let blocked = self.sig_mask().load(Ordering::Relaxed);
         self.sig_queues.has_pending(blocked)
     }
 
     /// Returns whether the signal is blocked by the thread.
     pub(in crate::process) fn has_signal_blocked(&self, signal: &dyn Signal) -> bool {
-        let mask = self.sig_mask.lock();
-        mask.contains(signal.num())
+        self.sig_mask.contains(signal.num(), Ordering::Relaxed)
     }
 
     /// Checks whether the signal can be delivered to the thread.
diff --git a/kernel/aster-nix/src/process/process/mod.rs b/kernel/aster-nix/src/process/process/mod.rs
index 54b594287..362d52df9 100644
--- a/kernel/aster-nix/src/process/process/mod.rs
+++ b/kernel/aster-nix/src/process/process/mod.rs
@@ -9,7 +9,6 @@ use super::{
     signal::{
         constants::SIGCHLD,
         sig_disposition::SigDispositions,
-        sig_mask::SigMask,
         sig_num::{AtomicSigNum, SigNum},
         signals::Signal,
         Pauser,
@@ -120,12 +119,9 @@ impl Process {
         nice: Nice,
         sig_dispositions: Arc<Mutex<SigDispositions>>,
     ) -> Arc<Self> {
-        let children_pauser = {
-            // SIGCHID does not interrupt pauser. Child process will
-            // resume paused parent when doing exit.
-            let sigmask = SigMask::from(SIGCHLD);
-            Pauser::new_with_mask(sigmask)
-        };
+        // SIGCHID does not interrupt pauser. Child process will
+        // resume paused parent when doing exit.
+        let children_pauser = Pauser::new_with_mask(SIGCHLD.into());
 
         let prof_clock = ProfClock::new();
 
diff --git a/kernel/aster-nix/src/process/signal/mod.rs b/kernel/aster-nix/src/process/signal/mod.rs
index 400ba3632..a53dcf201 100644
--- a/kernel/aster-nix/src/process/signal/mod.rs
+++ b/kernel/aster-nix/src/process/signal/mod.rs
@@ -49,7 +49,7 @@ pub fn handle_pending_signal(
     // We first deal with signal in current thread, then signal in current process.
     let posix_thread = current_thread.as_posix_thread().unwrap();
     let signal = {
-        let sig_mask = *posix_thread.sig_mask().lock();
+        let sig_mask = posix_thread.sig_mask().load(Ordering::Relaxed);
         if let Some(signal) = posix_thread.dequeue_signal(&sig_mask) {
             signal
         } else {
@@ -136,13 +136,15 @@ pub fn handle_user_signal(
     }
     if !flags.contains(SigActionFlags::SA_NODEFER) {
         // add current signal to mask
-        let current_mask = SigMask::from(sig_num);
-        mask.block(current_mask.as_u64());
+        mask += sig_num;
     }
     let current_thread = current_thread!();
     let posix_thread = current_thread.as_posix_thread().unwrap();
     // block signals in sigmask when running signal handler
-    posix_thread.sig_mask().lock().block(mask.as_u64());
+    let old_mask = posix_thread.sig_mask().load(Ordering::Relaxed);
+    posix_thread
+        .sig_mask()
+        .store(old_mask + mask, Ordering::Relaxed);
 
     // Set up signal stack.
     let mut stack_pointer = if let Some(sp) = use_alternate_signal_stack(posix_thread) {
@@ -163,7 +165,7 @@ pub fn handle_user_signal(
     // 2. write ucontext_t.
     stack_pointer = alloc_aligned_in_user_stack(stack_pointer, mem::size_of::<ucontext_t>(), 16)?;
     let mut ucontext = ucontext_t {
-        uc_sigmask: mask.as_u64(),
+        uc_sigmask: mask.into(),
         ..Default::default()
     };
     ucontext
diff --git a/kernel/aster-nix/src/process/signal/pauser.rs b/kernel/aster-nix/src/process/signal/pauser.rs
index 015f1e904..c200dc465 100644
--- a/kernel/aster-nix/src/process/signal/pauser.rs
+++ b/kernel/aster-nix/src/process/signal/pauser.rs
@@ -185,13 +185,9 @@ impl<'a> SigObserverRegistrar<'a> {
 
         // Block `sig_mask`.
         let (old_mask, filter) = {
-            let mut locked_mask = thread.sig_mask().lock();
-
-            let old_mask = *locked_mask;
-            let new_mask = {
-                locked_mask.block(sig_mask.as_u64());
-                *locked_mask
-            };
+            let old_mask = thread.sig_mask().load(Ordering::Relaxed);
+            let new_mask = old_mask + sig_mask;
+            thread.sig_mask().store(new_mask, Ordering::Relaxed);
 
             (old_mask, SigEventsFilter::new(new_mask))
         };
@@ -234,7 +230,7 @@ impl<'a> Drop for SigObserverRegistrar<'a> {
         // Restore the state, assuming no one else can modify the current thread's signal mask
         // during the pause.
         thread.unregiser_sigqueue_observer(&(Arc::downgrade(observer) as _));
-        thread.sig_mask().lock().set(old_mask.as_u64());
+        thread.sig_mask().store(*old_mask, Ordering::Relaxed);
     }
 }
 
diff --git a/kernel/aster-nix/src/process/signal/sig_action.rs b/kernel/aster-nix/src/process/signal/sig_action.rs
index 6301cb386..52293ce41 100644
--- a/kernel/aster-nix/src/process/signal/sig_action.rs
+++ b/kernel/aster-nix/src/process/signal/sig_action.rs
@@ -28,7 +28,7 @@ impl TryFrom<sigaction_t> for SigAction {
             SIG_IGN => SigAction::Ign,
             _ => {
                 let flags = SigActionFlags::from_bits_truncate(input.flags);
-                let mask = SigMask::from(input.mask);
+                let mask = input.mask.into();
                 SigAction::User {
                     handler_addr: input.handler_ptr,
                     flags,
@@ -65,7 +65,7 @@ impl SigAction {
                 handler_ptr: *handler_addr,
                 flags: flags.as_u32(),
                 restorer_ptr: *restorer_addr,
-                mask: mask.as_u64(),
+                mask: (*mask).into(),
             },
         }
     }
diff --git a/kernel/aster-nix/src/process/signal/sig_mask.rs b/kernel/aster-nix/src/process/signal/sig_mask.rs
index b82ebc0f7..f3b84be6f 100644
--- a/kernel/aster-nix/src/process/signal/sig_mask.rs
+++ b/kernel/aster-nix/src/process/signal/sig_mask.rs
@@ -1,84 +1,220 @@
 // SPDX-License-Identifier: MPL-2.0
 
+//! Signal sets and atomic masks.
+//!
+//! A signal set is a bit-set of signals. A signal mask is a set of signals
+//! that are blocked from delivery to a thread. An atomic signal mask
+//! implementation is provided for shared access to signal masks.
+
+use core::{
+    fmt::LowerHex,
+    ops,
+    sync::atomic::{AtomicU64, Ordering},
+};
+
 use super::{constants::MIN_STD_SIG_NUM, sig_num::SigNum};
 use crate::prelude::*;
 
 /// A signal mask.
+///
+/// This is an alias to the [`SigSet`]. All the signal in the set are blocked
+/// from the delivery to a thread.
 pub type SigMask = SigSet;
 
+/// A bit-set of signals.
+///
+/// Because that all the signal numbers are in the range of 1 to 64, casting
+/// a signal set from `u64` to `SigSet` will always succeed.
 #[derive(Debug, Copy, Clone, Default, PartialEq, Eq, Pod)]
 #[repr(C)]
 pub struct SigSet {
     bits: u64,
 }
 
-impl From<u64> for SigMask {
+impl From<SigNum> for SigSet {
+    fn from(signum: SigNum) -> Self {
+        let idx = signum.as_u8() - MIN_STD_SIG_NUM;
+        Self { bits: 1_u64 << idx }
+    }
+}
+
+impl From<u64> for SigSet {
     fn from(bits: u64) -> Self {
-        SigMask { bits }
+        SigSet { bits }
     }
 }
 
-impl From<SigNum> for SigMask {
-    fn from(sig_num: SigNum) -> Self {
-        let idx = SigMask::num_to_idx(sig_num);
-        let bits = 1u64 << idx;
-        SigMask { bits }
+impl From<SigSet> for u64 {
+    fn from(set: SigSet) -> u64 {
+        set.bits
     }
 }
 
-impl SigMask {
+impl<T: Into<SigSet>> ops::BitAnd<T> for SigSet {
+    type Output = Self;
+
+    fn bitand(self, rhs: T) -> Self {
+        SigSet {
+            bits: self.bits & rhs.into().bits,
+        }
+    }
+}
+
+impl<T: Into<SigSet>> ops::BitAndAssign<T> for SigSet {
+    fn bitand_assign(&mut self, rhs: T) {
+        self.bits &= rhs.into().bits;
+    }
+}
+
+impl<T: Into<SigSet>> ops::BitOr<T> for SigSet {
+    type Output = Self;
+
+    fn bitor(self, rhs: T) -> Self {
+        SigSet {
+            bits: self.bits | rhs.into().bits,
+        }
+    }
+}
+
+impl<T: Into<SigSet>> ops::BitOrAssign<T> for SigSet {
+    fn bitor_assign(&mut self, rhs: T) {
+        self.bits |= rhs.into().bits;
+    }
+}
+
+#[allow(clippy::suspicious_arithmetic_impl)]
+impl<T: Into<SigSet>> ops::Add<T> for SigSet {
+    type Output = Self;
+
+    fn add(self, rhs: T) -> Self {
+        SigSet {
+            bits: self.bits | rhs.into().bits,
+        }
+    }
+}
+
+#[allow(clippy::suspicious_op_assign_impl)]
+impl<T: Into<SigSet>> ops::AddAssign<T> for SigSet {
+    fn add_assign(&mut self, rhs: T) {
+        self.bits |= rhs.into().bits;
+    }
+}
+
+impl<T: Into<SigSet>> ops::Sub<T> for SigSet {
+    type Output = Self;
+
+    fn sub(self, rhs: T) -> Self {
+        SigSet {
+            bits: self.bits & !rhs.into().bits,
+        }
+    }
+}
+
+impl<T: Into<SigSet>> ops::SubAssign<T> for SigSet {
+    fn sub_assign(&mut self, rhs: T) {
+        self.bits &= !rhs.into().bits;
+    }
+}
+
+impl SigSet {
     pub fn new_empty() -> Self {
-        SigMask::from(0u64)
+        SigSet { bits: 0 }
     }
 
     pub fn new_full() -> Self {
-        SigMask::from(!0u64)
+        SigSet { bits: !0 }
     }
 
-    pub const fn as_u64(&self) -> u64 {
-        self.bits
-    }
-
-    pub const fn empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.bits == 0
     }
 
-    pub const fn full(&self) -> bool {
+    pub const fn is_full(&self) -> bool {
         self.bits == !0
     }
 
-    pub fn block(&mut self, block_sets: u64) {
-        self.bits |= block_sets;
-    }
-
-    pub fn unblock(&mut self, unblock_sets: u64) {
-        self.bits &= !unblock_sets;
-    }
-
-    pub fn set(&mut self, new_set: u64) {
-        self.bits = new_set;
-    }
-
     pub fn count(&self) -> usize {
         self.bits.count_ones() as usize
     }
 
-    pub fn contains(&self, signum: SigNum) -> bool {
-        let idx = Self::num_to_idx(signum);
-        (self.bits & (1_u64 << idx)) != 0
-    }
-
-    fn num_to_idx(num: SigNum) -> usize {
-        (num.as_u8() - MIN_STD_SIG_NUM) as usize
-    }
-
-    pub fn remove_signal(&mut self, signum: SigNum) {
-        let idx = Self::num_to_idx(signum);
-        self.bits &= !(1_u64 << idx);
-    }
-
-    pub fn add_signal(&mut self, signum: SigNum) {
-        let idx = Self::num_to_idx(signum);
-        self.bits |= 1_u64 << idx;
+    pub fn contains(&self, set: impl Into<Self>) -> bool {
+        let set = set.into();
+        self.bits & set.bits == set.bits
+    }
+}
+
+// This is to allow hexadecimally formatting a `SigSet` when debug printing it.
+impl LowerHex for SigSet {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        LowerHex::fmt(&self.bits, f) // delegate to u64's implementation
+    }
+}
+
+/// An atomic signal mask.
+///
+/// This is an alias to the [`AtomicSigSet`]. All the signal in the set are
+/// blocked from the delivery to a thread.
+///
+/// [`Relaxed`]: core::sync::atomic::Ordering::Relaxed
+pub type AtomicSigMask = AtomicSigSet;
+
+/// An atomic signal set.
+pub struct AtomicSigSet(AtomicU64);
+
+impl From<SigSet> for AtomicSigSet {
+    fn from(set: SigSet) -> Self {
+        AtomicSigSet(AtomicU64::new(set.bits))
+    }
+}
+
+impl AtomicSigSet {
+    pub fn new_empty() -> Self {
+        AtomicSigSet(AtomicU64::new(0))
+    }
+
+    pub fn new_full() -> Self {
+        AtomicSigSet(AtomicU64::new(!0))
+    }
+
+    pub fn load(&self, ordering: Ordering) -> SigSet {
+        SigSet {
+            bits: self.0.load(ordering),
+        }
+    }
+
+    pub fn store(&self, new_mask: impl Into<SigMask>, ordering: Ordering) {
+        self.0.store(new_mask.into().bits, ordering);
+    }
+
+    pub fn contains(&self, signals: impl Into<SigSet>, ordering: Ordering) -> bool {
+        SigSet {
+            bits: self.0.load(ordering),
+        }
+        .contains(signals.into())
+    }
+
+    /// Applies an update to the signal set.
+    ///
+    /// This is the same as [`AtomicU64::fetch_update`], but the closure `f`
+    /// operates on a [`SigMask`] instead of a `u64`.
+    ///
+    /// It would be a bit slow since it would check if the value is written by
+    /// another thread while evaluating the closure `f`. If you are confident
+    /// that there's no such race, don't use this method.
+    pub fn fetch_update<F>(
+        &self,
+        set_order: Ordering,
+        fetch_order: Ordering,
+        mut f: F,
+    ) -> core::result::Result<SigMask, SigMask>
+    where
+        F: FnMut(SigMask) -> Option<SigMask>,
+    {
+        self.0
+            .fetch_update(set_order, fetch_order, |bits| {
+                f(SigMask { bits }).map(|set| set.bits)
+            })
+            .map(SigMask::from)
+            .map_err(SigMask::from)
     }
 }
diff --git a/kernel/aster-nix/src/process/signal/sig_queues.rs b/kernel/aster-nix/src/process/signal/sig_queues.rs
index d48dad44e..692c7c6dd 100644
--- a/kernel/aster-nix/src/process/signal/sig_queues.rs
+++ b/kernel/aster-nix/src/process/signal/sig_queues.rs
@@ -222,14 +222,14 @@ impl Queues {
         // Process standard signal queues
         for (idx, signal) in self.std_queues.iter().enumerate() {
             if signal.is_some() {
-                pending.add_signal(SigNum::from_u8(idx as u8 + MIN_STD_SIG_NUM));
+                pending += SigNum::from_u8(idx as u8 + MIN_STD_SIG_NUM);
             }
         }
 
         // Process real-time signal queues
         for (idx, signals) in self.rt_queues.iter().enumerate() {
             if !signals.is_empty() {
-                pending.add_signal(SigNum::from_u8(idx as u8 + MIN_RT_SIG_NUM));
+                pending += SigNum::from_u8(idx as u8 + MIN_RT_SIG_NUM);
             }
         }
 
diff --git a/kernel/aster-nix/src/syscall/epoll.rs b/kernel/aster-nix/src/syscall/epoll.rs
index 39868a9a8..f3fb8aca6 100644
--- a/kernel/aster-nix/src/syscall/epoll.rs
+++ b/kernel/aster-nix/src/syscall/epoll.rs
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use core::time::Duration;
+use core::{sync::atomic::Ordering, time::Duration};
 
 use super::SyscallReturn;
 use crate::{
@@ -11,7 +11,7 @@ use crate::{
         utils::CreationFlags,
     },
     prelude::*,
-    process::posix_thread::PosixThreadExt,
+    process::{posix_thread::PosixThreadExt, signal::sig_mask::SigMask},
     util::{read_val_from_user, write_val_to_user},
 };
 
@@ -148,32 +148,31 @@ pub fn sys_epoll_wait(
     Ok(SyscallReturn::Return(epoll_events.len() as _))
 }
 
-fn set_signal_mask(set_ptr: Vaddr) -> Result<u64> {
-    let new_set: Option<u64> = if set_ptr != 0 {
-        Some(read_val_from_user::<u64>(set_ptr)?)
+fn set_signal_mask(set_ptr: Vaddr) -> Result<SigMask> {
+    let new_mask: Option<SigMask> = if set_ptr != 0 {
+        Some(read_val_from_user::<u64>(set_ptr)?.into())
     } else {
         None
     };
 
     let current_thread = current_thread!();
     let posix_thread = current_thread.as_posix_thread().unwrap();
-    let mut sig_mask = posix_thread.sig_mask().lock();
 
-    let old_sig_mask_value = sig_mask.as_u64();
+    let old_sig_mask_value = posix_thread.sig_mask().load(Ordering::Relaxed);
 
-    if let Some(new_set) = new_set {
-        sig_mask.set(new_set);
+    if let Some(new_mask) = new_mask {
+        posix_thread.sig_mask().store(new_mask, Ordering::Relaxed);
     }
 
     Ok(old_sig_mask_value)
 }
 
-fn restore_signal_mask(sig_mask_val: u64) {
+fn restore_signal_mask(sig_mask_val: SigMask) {
     let current_thread = current_thread!();
     let posix_thread = current_thread.as_posix_thread().unwrap();
-    let mut sig_mask = posix_thread.sig_mask().lock();
-
-    sig_mask.set(sig_mask_val);
+    posix_thread
+        .sig_mask()
+        .store(sig_mask_val, Ordering::Relaxed);
 }
 
 pub fn sys_epoll_pwait(
diff --git a/kernel/aster-nix/src/syscall/rt_sigpending.rs b/kernel/aster-nix/src/syscall/rt_sigpending.rs
index e19af003d..d6f2f929e 100644
--- a/kernel/aster-nix/src/syscall/rt_sigpending.rs
+++ b/kernel/aster-nix/src/syscall/rt_sigpending.rs
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
-#![allow(unused_variables)]
+use core::sync::atomic::Ordering;
 
 use super::SyscallReturn;
 use crate::{prelude::*, process::posix_thread::PosixThreadExt, util::write_val_to_user};
@@ -13,20 +13,20 @@ pub fn sys_rt_sigpending(u_set_ptr: Vaddr, sigset_size: usize) -> Result<Syscall
     if sigset_size != 8 {
         return_errno_with_message!(Errno::EINVAL, "sigset size is not equal to 8")
     }
-    do_rt_sigpending(u_set_ptr, sigset_size)?;
+    do_rt_sigpending(u_set_ptr)?;
     Ok(SyscallReturn::Return(0))
 }
 
-fn do_rt_sigpending(set_ptr: Vaddr, sigset_size: usize) -> Result<()> {
+fn do_rt_sigpending(set_ptr: Vaddr) -> Result<()> {
     let current_thread = current_thread!();
     let posix_thread = current_thread.as_posix_thread().unwrap();
 
     let combined_signals = {
-        let sig_mask_value = posix_thread.sig_mask().lock().as_u64();
-        let sig_pending_value = posix_thread.sig_pending().as_u64();
+        let sig_mask_value = posix_thread.sig_mask().load(Ordering::Relaxed);
+        let sig_pending_value = posix_thread.sig_pending();
         sig_mask_value & sig_pending_value
     };
 
-    write_val_to_user(set_ptr, &combined_signals)?;
+    write_val_to_user(set_ptr, &u64::from(combined_signals))?;
     Ok(())
 }
diff --git a/kernel/aster-nix/src/syscall/rt_sigprocmask.rs b/kernel/aster-nix/src/syscall/rt_sigprocmask.rs
index 45c723a70..81f429940 100644
--- a/kernel/aster-nix/src/syscall/rt_sigprocmask.rs
+++ b/kernel/aster-nix/src/syscall/rt_sigprocmask.rs
@@ -1,8 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
-#![allow(unused_variables)]
-
-use ostd::mm::VmIo;
+use core::sync::atomic::Ordering;
 
 use super::SyscallReturn;
 use crate::{
@@ -14,6 +12,7 @@ use crate::{
             sig_mask::SigMask,
         },
     },
+    util::{read_val_from_user, write_val_to_user},
 };
 
 pub fn sys_rt_sigprocmask(
@@ -30,42 +29,38 @@ pub fn sys_rt_sigprocmask(
     if sigset_size != 8 {
         error!("sigset size is not equal to 8");
     }
-    do_rt_sigprocmask(mask_op, set_ptr, oldset_ptr, sigset_size).unwrap();
+    do_rt_sigprocmask(mask_op, set_ptr, oldset_ptr).unwrap();
     Ok(SyscallReturn::Return(0))
 }
 
-fn do_rt_sigprocmask(
-    mask_op: MaskOp,
-    set_ptr: Vaddr,
-    oldset_ptr: Vaddr,
-    sigset_size: usize,
-) -> Result<()> {
-    let current = current!();
+fn do_rt_sigprocmask(mask_op: MaskOp, set_ptr: Vaddr, oldset_ptr: Vaddr) -> Result<()> {
     let current_thread = current_thread!();
     let posix_thread = current_thread.as_posix_thread().unwrap();
-    let root_vmar = current.root_vmar();
-    let mut sig_mask = posix_thread.sig_mask().lock();
-    let old_sig_mask_value = sig_mask.as_u64();
+
+    let old_sig_mask_value = posix_thread.sig_mask().load(Ordering::Relaxed);
     debug!("old sig mask value: 0x{:x}", old_sig_mask_value);
     if oldset_ptr != 0 {
-        root_vmar.write_val(oldset_ptr, &old_sig_mask_value)?;
+        write_val_to_user(oldset_ptr, &old_sig_mask_value)?;
     }
+
+    let sig_mask_ref = posix_thread.sig_mask();
     if set_ptr != 0 {
-        let new_set = root_vmar.read_val::<u64>(set_ptr)?;
+        let mut read_mask = read_val_from_user::<SigMask>(set_ptr)?;
         match mask_op {
             MaskOp::Block => {
-                let mut new_sig_mask = SigMask::from(new_set);
                 // According to man pages, "it is not possible to block SIGKILL or SIGSTOP.
                 // Attempts to do so are silently ignored."
-                new_sig_mask.remove_signal(SIGKILL);
-                new_sig_mask.remove_signal(SIGSTOP);
-                sig_mask.block(new_sig_mask.as_u64());
+                read_mask -= SIGKILL;
+                read_mask -= SIGSTOP;
+                sig_mask_ref.store(old_sig_mask_value + read_mask, Ordering::Relaxed);
             }
-            MaskOp::Unblock => sig_mask.unblock(new_set),
-            MaskOp::SetMask => sig_mask.set(new_set),
+            MaskOp::Unblock => {
+                sig_mask_ref.store(old_sig_mask_value - read_mask, Ordering::Relaxed)
+            }
+            MaskOp::SetMask => sig_mask_ref.store(read_mask, Ordering::Relaxed),
         }
     }
-    debug!("new set = {:x?}", &sig_mask);
+    debug!("new set = {:x?}", sig_mask_ref.load(Ordering::Relaxed));
 
     Ok(())
 }
diff --git a/kernel/aster-nix/src/syscall/rt_sigreturn.rs b/kernel/aster-nix/src/syscall/rt_sigreturn.rs
index bd45365f9..a4233826e 100644
--- a/kernel/aster-nix/src/syscall/rt_sigreturn.rs
+++ b/kernel/aster-nix/src/syscall/rt_sigreturn.rs
@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 
+use core::sync::atomic::Ordering;
+
 use ostd::{cpu::UserContext, user::UserContextApi};
 
 use super::SyscallReturn;
@@ -45,7 +47,10 @@ pub fn sys_rt_sigreturn(context: &mut UserContext) -> Result<SyscallReturn> {
         .copy_to_raw(context.general_regs_mut());
     // unblock sig mask
     let sig_mask = ucontext.uc_sigmask;
-    posix_thread.sig_mask().lock().unblock(sig_mask);
+    let old_mask = posix_thread.sig_mask().load(Ordering::Relaxed);
+    posix_thread
+        .sig_mask()
+        .store(old_mask - sig_mask, Ordering::Relaxed);
 
     Ok(SyscallReturn::NoReturn)
 }
diff --git a/kernel/aster-nix/src/syscall/rt_sigsuspend.rs b/kernel/aster-nix/src/syscall/rt_sigsuspend.rs
index 13e7da74d..5804d74a4 100644
--- a/kernel/aster-nix/src/syscall/rt_sigsuspend.rs
+++ b/kernel/aster-nix/src/syscall/rt_sigsuspend.rs
@@ -26,8 +26,8 @@ pub fn sys_rt_sigsuspend(sigmask_addr: Vaddr, sigmask_size: usize) -> Result<Sys
         let mut mask: SigMask = read_val_from_user(sigmask_addr)?;
         // It is not possible to block SIGKILL or SIGSTOP,
         // specifying these signals in mask has no effect.
-        mask.remove_signal(SIGKILL);
-        mask.remove_signal(SIGSTOP);
+        mask -= SIGKILL;
+        mask -= SIGSTOP;
         mask
     };