diff --git a/src/libos/src/interrupt/mod.rs b/src/libos/src/interrupt/mod.rs
index 7e3bd374..2f1fdfa4 100644
--- a/src/libos/src/interrupt/mod.rs
+++ b/src/libos/src/interrupt/mod.rs
@@ -38,8 +38,8 @@ pub fn broadcast_interrupts() -> Result<usize> {
     let should_interrupt_thread = |thread: &&ThreadRef| -> bool {
         // TODO: check Thread::sig_mask to reduce false positives
         thread.process().is_forced_to_exit()
-            || !thread.sig_queues().lock().unwrap().empty()
-            || !thread.process().sig_queues().lock().unwrap().empty()
+            || !thread.sig_queues().read().unwrap().empty()
+            || !thread.process().sig_queues().read().unwrap().empty()
     };
 
     let num_signaled_threads = crate::process::table::get_all_threads()
diff --git a/src/libos/src/prelude.rs b/src/libos/src/prelude.rs
index 69b5b139..42f207f5 100644
--- a/src/libos/src/prelude.rs
+++ b/src/libos/src/prelude.rs
@@ -17,6 +17,7 @@ pub use crate::error::Result;
 pub use crate::error::*;
 pub use crate::fs::{File, FileDesc, FileRef};
 pub use crate::process::{pid_t, uid_t};
+pub use crate::util::sync::RwLock;
 
 macro_rules! debug_trace {
     () => {
diff --git a/src/libos/src/process/do_exit.rs b/src/libos/src/process/do_exit.rs
index 2bebbc38..34c0c22c 100644
--- a/src/libos/src/process/do_exit.rs
+++ b/src/libos/src/process/do_exit.rs
@@ -130,6 +130,6 @@ fn exit_process(thread: &ThreadRef, term_status: TermStatus) {
 
 fn send_sigchld_to(parent: &Arc<Process>) {
     let signal = Box::new(KernelSignal::new(SigNum::from(SIGCHLD)));
-    let mut sig_queues = parent.sig_queues().lock().unwrap();
+    let mut sig_queues = parent.sig_queues().write().unwrap();
     sig_queues.enqueue(signal);
 }
diff --git a/src/libos/src/process/process/builder.rs b/src/libos/src/process/process/builder.rs
index 2dc446d4..23ff162a 100644
--- a/src/libos/src/process/process/builder.rs
+++ b/src/libos/src/process/process/builder.rs
@@ -100,7 +100,7 @@ impl ProcessBuilder {
             let parent = self.parent.take().map(|parent| SgxRwLock::new(parent));
             let inner = SgxMutex::new(ProcessInner::new());
             let sig_dispositions = SgxRwLock::new(SigDispositions::new());
-            let sig_queues = SgxMutex::new(SigQueues::new());
+            let sig_queues = RwLock::new(SigQueues::new());
             let forced_exit_status = ForcedExitStatus::new();
             Arc::new(Process {
                 pid,
diff --git a/src/libos/src/process/process/mod.rs b/src/libos/src/process/process/mod.rs
index 64ffab2d..46bf94a1 100644
--- a/src/libos/src/process/process/mod.rs
+++ b/src/libos/src/process/process/mod.rs
@@ -20,7 +20,7 @@ pub struct Process {
     inner: SgxMutex<ProcessInner>,
     // Signal
     sig_dispositions: SgxRwLock<SigDispositions>,
-    sig_queues: SgxMutex<SigQueues>,
+    sig_queues: RwLock<SigQueues>,
     forced_exit_status: ForcedExitStatus,
 }
 
@@ -100,7 +100,7 @@ impl Process {
     }
 
     /// Get the signal queues for process-directed signals.
-    pub fn sig_queues(&self) -> &SgxMutex<SigQueues> {
+    pub fn sig_queues(&self) -> &RwLock<SigQueues> {
         &self.sig_queues
     }
 
diff --git a/src/libos/src/process/thread/builder.rs b/src/libos/src/process/thread/builder.rs
index 6cea5863..a10ddc29 100644
--- a/src/libos/src/process/thread/builder.rs
+++ b/src/libos/src/process/thread/builder.rs
@@ -107,7 +107,7 @@ impl ThreadBuilder {
         let sched = self.sched.unwrap_or_default();
         let rlimits = self.rlimits.unwrap_or_default();
         let name = SgxRwLock::new(self.name.unwrap_or_default());
-        let sig_queues = SgxMutex::new(SigQueues::new());
+        let sig_queues = RwLock::new(SigQueues::new());
         let sig_mask = SgxRwLock::new(SigSet::new_empty());
         let sig_tmp_mask = SgxRwLock::new(SigSet::new_empty());
         let sig_stack = SgxMutex::new(None);
diff --git a/src/libos/src/process/thread/mod.rs b/src/libos/src/process/thread/mod.rs
index b613b74b..ee79029a 100644
--- a/src/libos/src/process/thread/mod.rs
+++ b/src/libos/src/process/thread/mod.rs
@@ -36,7 +36,7 @@ pub struct Thread {
     sched: SchedAgentRef,
     rlimits: ResourceLimitsRef,
     // Signal
-    sig_queues: SgxMutex<SigQueues>,
+    sig_queues: RwLock<SigQueues>,
     sig_mask: SgxRwLock<SigSet>,
     sig_tmp_mask: SgxRwLock<SigSet>,
     sig_stack: SgxMutex<Option<SigStack>>,
@@ -81,7 +81,7 @@ impl Thread {
     }
 
     /// Get the signal queues for thread-directed signals.
-    pub fn sig_queues(&self) -> &SgxMutex<SigQueues> {
+    pub fn sig_queues(&self) -> &RwLock<SigQueues> {
         &self.sig_queues
     }
 
diff --git a/src/libos/src/signal/do_kill.rs b/src/libos/src/signal/do_kill.rs
index 3b7b0c4e..39cbdf5a 100644
--- a/src/libos/src/signal/do_kill.rs
+++ b/src/libos/src/signal/do_kill.rs
@@ -16,7 +16,7 @@ pub fn do_kill(filter: ProcessFilter, signum: SigNum) -> Result<()> {
         }
 
         let signal = Box::new(UserSignal::new(signum, UserSignalKind::Kill, pid, uid));
-        let mut sig_queues = process.sig_queues().lock().unwrap();
+        let mut sig_queues = process.sig_queues().write().unwrap();
         sig_queues.enqueue(signal);
     }
     Ok(())
@@ -42,7 +42,7 @@ pub fn do_kill_from_outside_enclave(filter: ProcessFilter, signum: SigNum) -> Re
             continue;
         }
 
-        let mut sig_queues = process.sig_queues().lock().unwrap();
+        let mut sig_queues = process.sig_queues().write().unwrap();
         sig_queues.enqueue(signal.clone());
     }
     Ok(())
@@ -97,7 +97,7 @@ pub fn do_tgkill(pid: Option<pid_t>, tid: pid_t, signum: SigNum) -> Result<()> {
             src_uid,
         ))
     };
-    let mut sig_queues = thread.sig_queues().lock().unwrap();
+    let mut sig_queues = thread.sig_queues().write().unwrap();
     sig_queues.enqueue(signal);
     Ok(())
 }
diff --git a/src/libos/src/signal/do_sigpending.rs b/src/libos/src/signal/do_sigpending.rs
index e82a1d4a..843935f5 100644
--- a/src/libos/src/signal/do_sigpending.rs
+++ b/src/libos/src/signal/do_sigpending.rs
@@ -6,8 +6,8 @@ pub fn do_sigpending() -> Result<SigSet> {
 
     let thread = current!();
     let process = thread.process();
-    let pending = (thread.sig_queues().lock().unwrap().pending()
-        | process.sig_queues().lock().unwrap().pending())
+    let pending = (thread.sig_queues().read().unwrap().pending()
+        | process.sig_queues().read().unwrap().pending())
         & *thread.sig_mask().read().unwrap();
     Ok(pending)
 }
diff --git a/src/libos/src/signal/do_sigreturn.rs b/src/libos/src/signal/do_sigreturn.rs
index 3f0ece3d..6a0118d2 100644
--- a/src/libos/src/signal/do_sigreturn.rs
+++ b/src/libos/src/signal/do_sigreturn.rs
@@ -66,12 +66,23 @@ pub fn deliver_signal(cpu_context: &mut CpuContext) {
 
 fn do_deliver_signal(thread: &ThreadRef, process: &ProcessRef, cpu_context: &mut CpuContext) {
     loop {
-        // Dequeue a signal, respecting the signal mask and tmp mask
-        let sig_mask = *thread.sig_mask().read().unwrap() | *thread.sig_tmp_mask().read().unwrap();
+        if process.sig_queues().read().unwrap().empty()
+            && thread.sig_queues().read().unwrap().empty()
+        {
+            return;
+        }
+
         let signal = {
-            #[rustfmt::skip]
-            let signal_opt = process.sig_queues().lock().unwrap().dequeue(&sig_mask)
-                .or_else(|| thread.sig_queues().lock().unwrap().dequeue(&sig_mask));
+            // Dequeue a signal, respecting the signal mask and tmp mask
+            let sig_mask =
+                *thread.sig_mask().read().unwrap() | *thread.sig_tmp_mask().read().unwrap();
+
+            let signal_opt = process
+                .sig_queues()
+                .write()
+                .unwrap()
+                .dequeue(&sig_mask)
+                .or_else(|| thread.sig_queues().write().unwrap().dequeue(&sig_mask));
             if signal_opt.is_none() {
                 return;
             }
diff --git a/src/libos/src/signal/sig_queues.rs b/src/libos/src/signal/sig_queues.rs
index 5422b42f..eb9c73be 100644
--- a/src/libos/src/signal/sig_queues.rs
+++ b/src/libos/src/signal/sig_queues.rs
@@ -7,7 +7,6 @@ use crate::prelude::*;
 
 pub struct SigQueues {
     count: usize,
-    has_kill: bool,
     std_queues: Vec<Option<Box<dyn Signal>>>,
     rt_queues: Vec<VecDeque<Box<dyn Signal>>>,
 }
@@ -15,12 +14,10 @@ pub struct SigQueues {
 impl SigQueues {
     pub fn new() -> Self {
         let count = 0;
-        let has_kill = false;
         let std_queues = (0..COUNT_STD_SIGS).map(|_| None).collect();
         let rt_queues = (0..COUNT_RT_SIGS).map(|_| Default::default()).collect();
         SigQueues {
             count,
-            has_kill,
             std_queues,
             rt_queues,
         }