diff --git a/easy-fs-fuse/Cargo.toml b/easy-fs-fuse/Cargo.toml
index 5c5e68d5..3470de93 100644
--- a/easy-fs-fuse/Cargo.toml
+++ b/easy-fs-fuse/Cargo.toml
@@ -9,6 +9,7 @@ edition = "2018"
 [dependencies]
 clap = "2.33.3"
 easy-fs = { path = "../easy-fs" }
+ksync = { path = "../ksync" }
 rand = "0.8.0"
 
 # [features]
diff --git a/easy-fs-fuse/src/main.rs b/easy-fs-fuse/src/main.rs
index bb9ff761..4f0da2e9 100644
--- a/easy-fs-fuse/src/main.rs
+++ b/easy-fs-fuse/src/main.rs
@@ -153,3 +153,16 @@ fn efs_test() -> std::io::Result<()> {
 
     Ok(())
 }
+
+// extern "C" {
+//     fn swap_and_disable_intr() -> bool;
+//     fn enable_intr();
+// }
+
+#[no_mangle]
+extern "C" fn swap_and_disable_intr() -> bool {
+    false
+}
+
+#[no_mangle]
+extern "C" fn enable_intr() {}
\ No newline at end of file
diff --git a/easy-fs/Cargo.toml b/easy-fs/Cargo.toml
index 7a2f38ed..a2d79abc 100644
--- a/easy-fs/Cargo.toml
+++ b/easy-fs/Cargo.toml
@@ -7,7 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-spin = "0.7.0"
+ksync = { path = "../ksync" }
 lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
 
 [profile.release]
diff --git a/easy-fs/src/bitmap.rs b/easy-fs/src/bitmap.rs
index 2cea613e..6cf5c61b 100644
--- a/easy-fs/src/bitmap.rs
+++ b/easy-fs/src/bitmap.rs
@@ -31,7 +31,7 @@ impl Bitmap {
                 block_id + self.start_block_id as usize,
                 Arc::clone(block_device),
             )
-            .lock()
+            .exclusive_access()
             .modify(0, |bitmap_block: &mut BitmapBlock| {
                 if let Some((bits64_pos, inner_pos)) = bitmap_block
                     .iter()
@@ -56,7 +56,7 @@ impl Bitmap {
     pub fn dealloc(&self, block_device: &Arc<dyn BlockDevice>, bit: usize) {
         let (block_pos, bits64_pos, inner_pos) = decomposition(bit);
         get_block_cache(block_pos + self.start_block_id, Arc::clone(block_device))
-            .lock()
+            .exclusive_access()
             .modify(0, |bitmap_block: &mut BitmapBlock| {
                 assert!(bitmap_block[bits64_pos] & (1u64 << inner_pos) > 0);
                 bitmap_block[bits64_pos] -= 1u64 << inner_pos;
diff --git a/easy-fs/src/block_cache.rs b/easy-fs/src/block_cache.rs
index 1b3b9697..0eae543a 100644
--- a/easy-fs/src/block_cache.rs
+++ b/easy-fs/src/block_cache.rs
@@ -4,7 +4,7 @@ use alloc::sync::Arc;
 use alloc::vec;
 use alloc::vec::Vec;
 use lazy_static::*;
-use spin::Mutex;
+use ksync::UPIntrFreeCell;
 
 pub struct BlockCache {
     cache: Vec<u8>,
@@ -77,7 +77,7 @@ impl Drop for BlockCache {
 const BLOCK_CACHE_SIZE: usize = 16;
 
 pub struct BlockCacheManager {
-    queue: VecDeque<(usize, Arc<Mutex<BlockCache>>)>,
+    queue: VecDeque<(usize, Arc<UPIntrFreeCell<BlockCache>>)>,
 }
 
 impl BlockCacheManager {
@@ -91,7 +91,7 @@ impl BlockCacheManager {
         &mut self,
         block_id: usize,
         block_device: Arc<dyn BlockDevice>,
-    ) -> Arc<Mutex<BlockCache>> {
+    ) -> Arc<UPIntrFreeCell<BlockCache>> {
         if let Some(pair) = self.queue.iter().find(|pair| pair.0 == block_id) {
             Arc::clone(&pair.1)
         } else {
@@ -110,10 +110,10 @@ impl BlockCacheManager {
                 }
             }
             // load block into mem and push back
-            let block_cache = Arc::new(Mutex::new(BlockCache::new(
+            let block_cache = Arc::new(unsafe { UPIntrFreeCell::new(BlockCache::new(
                 block_id,
                 Arc::clone(&block_device),
-            )));
+            ))});
             self.queue.push_back((block_id, Arc::clone(&block_cache)));
             block_cache
         }
@@ -121,22 +121,22 @@ impl BlockCacheManager {
 }
 
 lazy_static! {
-    pub static ref BLOCK_CACHE_MANAGER: Mutex<BlockCacheManager> =
-        Mutex::new(BlockCacheManager::new());
+    pub static ref BLOCK_CACHE_MANAGER: UPIntrFreeCell<BlockCacheManager> =
+        unsafe { UPIntrFreeCell::new(BlockCacheManager::new()) };
 }
 
 pub fn get_block_cache(
     block_id: usize,
     block_device: Arc<dyn BlockDevice>,
-) -> Arc<Mutex<BlockCache>> {
+) -> Arc<UPIntrFreeCell<BlockCache>> {
     BLOCK_CACHE_MANAGER
-        .lock()
+        .exclusive_access()
         .get_block_cache(block_id, block_device)
 }
 
 pub fn block_cache_sync_all() {
-    let manager = BLOCK_CACHE_MANAGER.lock();
+    let manager = BLOCK_CACHE_MANAGER.exclusive_access();
     for (_, cache) in manager.queue.iter() {
-        cache.lock().sync();
+        cache.exclusive_access().sync();
     }
 }
diff --git a/easy-fs/src/efs.rs b/easy-fs/src/efs.rs
index 82e95ae0..0382a1cb 100644
--- a/easy-fs/src/efs.rs
+++ b/easy-fs/src/efs.rs
@@ -4,7 +4,7 @@ use super::{
 };
 use crate::BLOCK_SZ;
 use alloc::sync::Arc;
-use spin::Mutex;
+use ksync::UPIntrFreeCell;
 
 pub struct EasyFileSystem {
     pub block_device: Arc<dyn BlockDevice>,
@@ -21,7 +21,7 @@ impl EasyFileSystem {
         block_device: Arc<dyn BlockDevice>,
         total_blocks: u32,
         inode_bitmap_blocks: u32,
-    ) -> Arc<Mutex<Self>> {
+    ) -> Arc<UPIntrFreeCell<Self>> {
         // calculate block size of areas & create bitmaps
         let inode_bitmap = Bitmap::new(1, inode_bitmap_blocks as usize);
         let inode_num = inode_bitmap.maximum();
@@ -45,7 +45,7 @@ impl EasyFileSystem {
         // clear all blocks
         for i in 0..total_blocks {
             get_block_cache(i as usize, Arc::clone(&block_device))
-                .lock()
+                .exclusive_access()
                 .modify(0, |data_block: &mut DataBlock| {
                     for byte in data_block.iter_mut() {
                         *byte = 0;
@@ -53,7 +53,7 @@ impl EasyFileSystem {
                 });
         }
         // initialize SuperBlock
-        get_block_cache(0, Arc::clone(&block_device)).lock().modify(
+        get_block_cache(0, Arc::clone(&block_device)).exclusive_access().modify(
             0,
             |super_block: &mut SuperBlock| {
                 super_block.initialize(
@@ -70,18 +70,18 @@ impl EasyFileSystem {
         assert_eq!(efs.alloc_inode(), 0);
         let (root_inode_block_id, root_inode_offset) = efs.get_disk_inode_pos(0);
         get_block_cache(root_inode_block_id as usize, Arc::clone(&block_device))
-            .lock()
+            .exclusive_access()
             .modify(root_inode_offset, |disk_inode: &mut DiskInode| {
                 disk_inode.initialize(DiskInodeType::Directory);
             });
         block_cache_sync_all();
-        Arc::new(Mutex::new(efs))
+        Arc::new(unsafe { UPIntrFreeCell::new(efs) })
     }
 
-    pub fn open(block_device: Arc<dyn BlockDevice>) -> Arc<Mutex<Self>> {
+    pub fn open(block_device: Arc<dyn BlockDevice>) -> Arc<UPIntrFreeCell<Self>> {
         // read SuperBlock
         get_block_cache(0, Arc::clone(&block_device))
-            .lock()
+            .exclusive_access()
             .read(0, |super_block: &SuperBlock| {
                 assert!(super_block.is_valid(), "Error loading EFS!");
                 let inode_total_blocks =
@@ -96,14 +96,14 @@ impl EasyFileSystem {
                     inode_area_start_block: 1 + super_block.inode_bitmap_blocks,
                     data_area_start_block: 1 + inode_total_blocks + super_block.data_bitmap_blocks,
                 };
-                Arc::new(Mutex::new(efs))
+                Arc::new(unsafe { UPIntrFreeCell::new(efs) })
             })
     }
 
-    pub fn root_inode(efs: &Arc<Mutex<Self>>) -> Inode {
-        let block_device = Arc::clone(&efs.lock().block_device);
+    pub fn root_inode(efs: &Arc<UPIntrFreeCell<Self>>) -> Inode {
+        let block_device = Arc::clone(&efs.exclusive_access().block_device);
         // acquire efs lock temporarily
-        let (block_id, block_offset) = efs.lock().get_disk_inode_pos(0);
+        let (block_id, block_offset) = efs.exclusive_access().get_disk_inode_pos(0);
         // release efs lock
         Inode::new(block_id, block_offset, Arc::clone(efs), block_device)
     }
@@ -133,7 +133,7 @@ impl EasyFileSystem {
 
     pub fn dealloc_data(&mut self, block_id: u32) {
         get_block_cache(block_id as usize, Arc::clone(&self.block_device))
-            .lock()
+            .exclusive_access()
             .modify(0, |data_block: &mut DataBlock| {
                 data_block.iter_mut().for_each(|p| {
                     *p = 0;
diff --git a/easy-fs/src/layout.rs b/easy-fs/src/layout.rs
index 618484cf..5cad9832 100644
--- a/easy-fs/src/layout.rs
+++ b/easy-fs/src/layout.rs
@@ -126,19 +126,19 @@ impl DiskInode {
             self.direct[inner_id]
         } else if inner_id < INDIRECT1_BOUND {
             get_block_cache(self.indirect1 as usize, Arc::clone(block_device))
-                .lock()
+                .exclusive_access()
                 .read(0, |indirect_block: &IndirectBlock| {
                     indirect_block[inner_id - INODE_DIRECT_COUNT]
                 })
         } else {
             let last = inner_id - INDIRECT1_BOUND;
             let indirect1 = get_block_cache(self.indirect2 as usize, Arc::clone(block_device))
-                .lock()
+                .exclusive_access()
                 .read(0, |indirect2: &IndirectBlock| {
                     indirect2[last / INODE_INDIRECT1_COUNT]
                 });
             get_block_cache(indirect1 as usize, Arc::clone(block_device))
-                .lock()
+                .exclusive_access()
                 .read(0, |indirect1: &IndirectBlock| {
                     indirect1[last % INODE_INDIRECT1_COUNT]
                 })
@@ -171,7 +171,7 @@ impl DiskInode {
         }
         // fill indirect1
         get_block_cache(self.indirect1 as usize, Arc::clone(block_device))
-            .lock()
+            .exclusive_access()
             .modify(0, |indirect1: &mut IndirectBlock| {
                 while current_blocks < total_blocks.min(INODE_INDIRECT1_COUNT as u32) {
                     indirect1[current_blocks as usize] = new_blocks.next().unwrap();
@@ -195,7 +195,7 @@ impl DiskInode {
         let b1 = total_blocks as usize % INODE_INDIRECT1_COUNT;
         // alloc low-level indirect1
         get_block_cache(self.indirect2 as usize, Arc::clone(block_device))
-            .lock()
+            .exclusive_access()
             .modify(0, |indirect2: &mut IndirectBlock| {
                 while (a0 < a1) || (a0 == a1 && b0 < b1) {
                     if b0 == 0 {
@@ -203,7 +203,7 @@ impl DiskInode {
                     }
                     // fill current
                     get_block_cache(indirect2[a0] as usize, Arc::clone(block_device))
-                        .lock()
+                        .exclusive_access()
                         .modify(0, |indirect1: &mut IndirectBlock| {
                             indirect1[b0] = new_blocks.next().unwrap();
                         });
@@ -241,7 +241,7 @@ impl DiskInode {
         }
         // indirect1
         get_block_cache(self.indirect1 as usize, Arc::clone(block_device))
-            .lock()
+            .exclusive_access()
             .modify(0, |indirect1: &mut IndirectBlock| {
                 while current_blocks < data_blocks.min(INODE_INDIRECT1_COUNT) {
                     v.push(indirect1[current_blocks]);
@@ -262,13 +262,13 @@ impl DiskInode {
         let a1 = data_blocks / INODE_INDIRECT1_COUNT;
         let b1 = data_blocks % INODE_INDIRECT1_COUNT;
         get_block_cache(self.indirect2 as usize, Arc::clone(block_device))
-            .lock()
+            .exclusive_access()
             .modify(0, |indirect2: &mut IndirectBlock| {
                 // full indirect1 blocks
                 for entry in indirect2.iter_mut().take(a1) {
                     v.push(*entry);
                     get_block_cache(*entry as usize, Arc::clone(block_device))
-                        .lock()
+                        .exclusive_access()
                         .modify(0, |indirect1: &mut IndirectBlock| {
                             for entry in indirect1.iter() {
                                 v.push(*entry);
@@ -279,7 +279,7 @@ impl DiskInode {
                 if b1 > 0 {
                     v.push(indirect2[a1]);
                     get_block_cache(indirect2[a1] as usize, Arc::clone(block_device))
-                        .lock()
+                        .exclusive_access()
                         .modify(0, |indirect1: &mut IndirectBlock| {
                             for entry in indirect1.iter().take(b1) {
                                 v.push(*entry);
@@ -315,7 +315,7 @@ impl DiskInode {
                 self.get_block_id(start_block as u32, block_device) as usize,
                 Arc::clone(block_device),
             )
-            .lock()
+            .exclusive_access()
             .read(0, |data_block: &DataBlock| {
                 let src = &data_block[start % BLOCK_SZ..start % BLOCK_SZ + block_read_size];
                 dst.copy_from_slice(src);
@@ -352,7 +352,7 @@ impl DiskInode {
                 self.get_block_id(start_block as u32, block_device) as usize,
                 Arc::clone(block_device),
             )
-            .lock()
+            .exclusive_access()
             .modify(0, |data_block: &mut DataBlock| {
                 let src = &buf[write_size..write_size + block_write_size];
                 let dst = &mut data_block[start % BLOCK_SZ..start % BLOCK_SZ + block_write_size];
diff --git a/easy-fs/src/vfs.rs b/easy-fs/src/vfs.rs
index 7290fa47..242789ad 100644
--- a/easy-fs/src/vfs.rs
+++ b/easy-fs/src/vfs.rs
@@ -5,12 +5,12 @@ use super::{
 use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
-use spin::{Mutex, MutexGuard};
+use ksync::{UPIntrFreeCell, UPIntrRefMut};
 
 pub struct Inode {
     block_id: usize,
     block_offset: usize,
-    fs: Arc<Mutex<EasyFileSystem>>,
+    fs: Arc<UPIntrFreeCell<EasyFileSystem>>,
     block_device: Arc<dyn BlockDevice>,
 }
 
@@ -19,7 +19,7 @@ impl Inode {
     pub fn new(
         block_id: u32,
         block_offset: usize,
-        fs: Arc<Mutex<EasyFileSystem>>,
+        fs: Arc<UPIntrFreeCell<EasyFileSystem>>,
         block_device: Arc<dyn BlockDevice>,
     ) -> Self {
         Self {
@@ -32,13 +32,13 @@ impl Inode {
 
     fn read_disk_inode<V>(&self, f: impl FnOnce(&DiskInode) -> V) -> V {
         get_block_cache(self.block_id, Arc::clone(&self.block_device))
-            .lock()
+            .exclusive_access()
             .read(self.block_offset, f)
     }
 
     fn modify_disk_inode<V>(&self, f: impl FnOnce(&mut DiskInode) -> V) -> V {
         get_block_cache(self.block_id, Arc::clone(&self.block_device))
-            .lock()
+            .exclusive_access()
             .modify(self.block_offset, f)
     }
 
@@ -60,7 +60,7 @@ impl Inode {
     }
 
     pub fn find(&self, name: &str) -> Option<Arc<Inode>> {
-        let fs = self.fs.lock();
+        let fs = self.fs.exclusive_access();
         self.read_disk_inode(|disk_inode| {
             self.find_inode_id(name, disk_inode).map(|inode_id| {
                 let (block_id, block_offset) = fs.get_disk_inode_pos(inode_id);
@@ -78,7 +78,7 @@ impl Inode {
         &self,
         new_size: u32,
         disk_inode: &mut DiskInode,
-        fs: &mut MutexGuard<EasyFileSystem>,
+        fs: &mut UPIntrRefMut<EasyFileSystem>,
     ) {
         if new_size < disk_inode.size {
             return;
@@ -92,7 +92,7 @@ impl Inode {
     }
 
     pub fn create(&self, name: &str) -> Option<Arc<Inode>> {
-        let mut fs = self.fs.lock();
+        let mut fs = self.fs.exclusive_access();
         let op = |root_inode: &mut DiskInode| {
             // assert it is a directory
             assert!(root_inode.is_dir());
@@ -108,7 +108,7 @@ impl Inode {
         // initialize inode
         let (new_inode_block_id, new_inode_block_offset) = fs.get_disk_inode_pos(new_inode_id);
         get_block_cache(new_inode_block_id as usize, Arc::clone(&self.block_device))
-            .lock()
+            .exclusive_access()
             .modify(new_inode_block_offset, |new_inode: &mut DiskInode| {
                 new_inode.initialize(DiskInodeType::File);
             });
@@ -140,7 +140,7 @@ impl Inode {
     }
 
     pub fn ls(&self) -> Vec<String> {
-        let _fs = self.fs.lock();
+        let _fs = self.fs.exclusive_access();
         self.read_disk_inode(|disk_inode| {
             let file_count = (disk_inode.size as usize) / DIRENT_SZ;
             let mut v: Vec<String> = Vec::new();
@@ -157,12 +157,12 @@ impl Inode {
     }
 
     pub fn read_at(&self, offset: usize, buf: &mut [u8]) -> usize {
-        let _fs = self.fs.lock();
+        let _fs = self.fs.exclusive_access();
         self.read_disk_inode(|disk_inode| disk_inode.read_at(offset, buf, &self.block_device))
     }
 
     pub fn write_at(&self, offset: usize, buf: &[u8]) -> usize {
-        let mut fs = self.fs.lock();
+        let mut fs = self.fs.exclusive_access();
         let size = self.modify_disk_inode(|disk_inode| {
             self.increase_size((offset + buf.len()) as u32, disk_inode, &mut fs);
             disk_inode.write_at(offset, buf, &self.block_device)
@@ -172,7 +172,7 @@ impl Inode {
     }
 
     pub fn clear(&self) {
-        let mut fs = self.fs.lock();
+        let mut fs = self.fs.exclusive_access();
         self.modify_disk_inode(|disk_inode| {
             let size = disk_inode.size;
             let data_blocks_dealloc = disk_inode.clear_size(&self.block_device);
diff --git a/ksync/Cargo.toml b/ksync/Cargo.toml
new file mode 100644
index 00000000..3596ffa0
--- /dev/null
+++ b/ksync/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "ksync"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
\ No newline at end of file
diff --git a/ksync/src/lib.rs b/ksync/src/lib.rs
new file mode 100644
index 00000000..eaafe749
--- /dev/null
+++ b/ksync/src/lib.rs
@@ -0,0 +1,143 @@
+#![no_std]
+
+use core::cell::{RefCell, RefMut, UnsafeCell};
+use core::ops::{Deref, DerefMut};
+use lazy_static::*;
+
+/// Wrap a static data structure inside it so that we are
+/// able to access it without any `unsafe`.
+///
+/// We should only use it in uniprocessor.
+///
+/// In order to get mutable reference of inner data, call
+/// `exclusive_access`.
+pub struct UPSafeCell<T> {
+    /// inner data
+    inner: RefCell<T>,
+}
+
+unsafe impl<T> Sync for UPSafeCell<T> {}
+
+impl<T> UPSafeCell<T> {
+    /// User is responsible to guarantee that inner struct is only used in
+    /// uniprocessor.
+    pub unsafe fn new(value: T) -> Self {
+        Self {
+            inner: RefCell::new(value),
+        }
+    }
+    /// Panic if the data has been borrowed.
+    pub fn exclusive_access(&self) -> RefMut<'_, T> {
+        self.inner.borrow_mut()
+    }
+}
+
+extern "C" {
+    fn swap_and_disable_intr() -> bool;
+    fn enable_intr();
+}
+
+pub struct UPSafeCellRaw<T> {
+    inner: UnsafeCell<T>,
+}
+
+unsafe impl<T> Sync for UPSafeCellRaw<T> {}
+
+impl<T> UPSafeCellRaw<T> {
+    pub unsafe fn new(value: T) -> Self {
+        Self {
+            inner: UnsafeCell::new(value),
+        }
+    }
+    pub fn get_mut(&self) -> &mut T {
+        unsafe { &mut (*self.inner.get()) }
+    }
+}
+
+struct IntrMaskingInfo {
+    nested_level: usize,
+    intr_enable_before_masking: bool,
+}
+
+lazy_static! {
+    static ref INTR_MASKING_INFO: UPSafeCellRaw<IntrMaskingInfo> =
+        unsafe { UPSafeCellRaw::new(IntrMaskingInfo::new()) };
+}
+
+impl IntrMaskingInfo {
+    pub fn new() -> Self {
+        Self {
+            nested_level: 0,
+            intr_enable_before_masking: false,
+        }
+    }
+
+    pub fn enter(&mut self) {
+        let prev_enable = unsafe {
+            swap_and_disable_intr() 
+        };
+        if self.nested_level == 0 {
+            self.intr_enable_before_masking = prev_enable;
+        }
+        self.nested_level += 1;
+    }
+
+    pub fn exit(&mut self) {
+        self.nested_level -= 1;
+        if self.nested_level == 0 && self.intr_enable_before_masking {
+            unsafe {
+                enable_intr();
+            }
+        }
+    }
+}
+
+pub struct UPIntrFreeCell<T> {
+    /// inner data
+    inner: RefCell<T>,
+}
+
+unsafe impl<T> Sync for UPIntrFreeCell<T> {}
+
+pub struct UPIntrRefMut<'a, T>(Option<RefMut<'a, T>>);
+
+impl<T> UPIntrFreeCell<T> {
+    pub unsafe fn new(value: T) -> Self {
+        Self {
+            inner: RefCell::new(value),
+        }
+    }
+
+    /// Panic if the data has been borrowed.
+    pub fn exclusive_access(&self) -> UPIntrRefMut<'_, T> {
+        INTR_MASKING_INFO.get_mut().enter();
+        UPIntrRefMut(Some(self.inner.borrow_mut()))
+    }
+
+    pub fn exclusive_session<F, V>(&self, f: F) -> V
+    where
+        F: FnOnce(&mut T) -> V,
+    {
+        let mut inner = self.exclusive_access();
+        f(inner.deref_mut())
+    }
+}
+
+impl<'a, T> Drop for UPIntrRefMut<'a, T> {
+    fn drop(&mut self) {
+        self.0 = None;
+        INTR_MASKING_INFO.get_mut().exit();
+    }
+}
+
+impl<'a, T> Deref for UPIntrRefMut<'a, T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        self.0.as_ref().unwrap().deref()
+    }
+}
+impl<'a, T> DerefMut for UPIntrRefMut<'a, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.0.as_mut().unwrap().deref_mut()
+    }
+}
diff --git a/os/Cargo.toml b/os/Cargo.toml
index e23fe161..419e4373 100644
--- a/os/Cargo.toml
+++ b/os/Cargo.toml
@@ -18,6 +18,7 @@ lose-net-stack = { git = "https://github.com/yfblock/lose-net-stack", rev = "3f4
 easy-fs = { path = "../easy-fs" }
 embedded-graphics = "0.7.1"
 tinybmp = "0.3.1"
+ksync = { path = "../ksync" }
 
 [profile.release]
 debug = true
diff --git a/os/src/fs/inode.rs b/os/src/fs/inode.rs
index 321338d4..47f4a88b 100644
--- a/os/src/fs/inode.rs
+++ b/os/src/fs/inode.rs
@@ -83,9 +83,11 @@ impl OpenFlags {
 }
 
 pub fn open_file(name: &str, flags: OpenFlags) -> Option<Arc<OSInode>> {
+    println!("open_file :1");
     let (readable, writable) = flags.read_write();
     if flags.contains(OpenFlags::CREATE) {
         if let Some(inode) = ROOT_INODE.find(name) {
+            println!("open_file :2");
             // clear size
             inode.clear();
             Some(Arc::new(OSInode::new(readable, writable, inode)))
diff --git a/os/src/sync/up.rs b/os/src/sync/up.rs
index 6c7a0f4a..14cb81bf 100644
--- a/os/src/sync/up.rs
+++ b/os/src/sync/up.rs
@@ -1,140 +1,23 @@
-use core::cell::{RefCell, RefMut, UnsafeCell};
-use core::ops::{Deref, DerefMut};
-use lazy_static::*;
+pub use ksync::{UPIntrFreeCell, UPIntrRefMut};
 use riscv::register::sstatus;
 
-/*
-/// Wrap a static data structure inside it so that we are
-/// able to access it without any `unsafe`.
-///
-/// We should only use it in uniprocessor.
-///
-/// In order to get mutable reference of inner data, call
-/// `exclusive_access`.
-pub struct UPSafeCell<T> {
-    /// inner data
-    inner: RefCell<T>,
+// extern "C" {
+//     fn swap_and_disable_intr() -> bool;
+//     fn enable_intr();
+// }
+
+#[no_mangle]
+extern "C" fn swap_and_disable_intr() -> bool {
+    let sie = sstatus::read().sie();
+    unsafe {
+        sstatus::clear_sie();
+    }
+    sie
 }
 
-unsafe impl<T> Sync for UPSafeCell<T> {}
-
-impl<T> UPSafeCell<T> {
-    /// User is responsible to guarantee that inner struct is only used in
-    /// uniprocessor.
-    pub unsafe fn new(value: T) -> Self {
-        Self {
-            inner: RefCell::new(value),
-        }
+#[no_mangle]
+extern "C" fn enable_intr() {
+    unsafe {
+        sstatus::set_sie();
     }
-    /// Panic if the data has been borrowed.
-    pub fn exclusive_access(&self) -> RefMut<'_, T> {
-        self.inner.borrow_mut()
-    }
-}
-*/
-
-pub struct UPSafeCellRaw<T> {
-    inner: UnsafeCell<T>,
-}
-
-unsafe impl<T> Sync for UPSafeCellRaw<T> {}
-
-impl<T> UPSafeCellRaw<T> {
-    pub unsafe fn new(value: T) -> Self {
-        Self {
-            inner: UnsafeCell::new(value),
-        }
-    }
-    pub fn get_mut(&self) -> &mut T {
-        unsafe { &mut (*self.inner.get()) }
-    }
-}
-
-pub struct IntrMaskingInfo {
-    nested_level: usize,
-    sie_before_masking: bool,
-}
-
-lazy_static! {
-    static ref INTR_MASKING_INFO: UPSafeCellRaw<IntrMaskingInfo> =
-        unsafe { UPSafeCellRaw::new(IntrMaskingInfo::new()) };
-}
-
-impl IntrMaskingInfo {
-    pub fn new() -> Self {
-        Self {
-            nested_level: 0,
-            sie_before_masking: false,
-        }
-    }
-
-    pub fn enter(&mut self) {
-        let sie = sstatus::read().sie();
-        unsafe {
-            sstatus::clear_sie();
-        }
-        if self.nested_level == 0 {
-            self.sie_before_masking = sie;
-        }
-        self.nested_level += 1;
-    }
-
-    pub fn exit(&mut self) {
-        self.nested_level -= 1;
-        if self.nested_level == 0 && self.sie_before_masking {
-            unsafe {
-                sstatus::set_sie();
-            }
-        }
-    }
-}
-
-pub struct UPIntrFreeCell<T> {
-    /// inner data
-    inner: RefCell<T>,
-}
-
-unsafe impl<T> Sync for UPIntrFreeCell<T> {}
-
-pub struct UPIntrRefMut<'a, T>(Option<RefMut<'a, T>>);
-
-impl<T> UPIntrFreeCell<T> {
-    pub unsafe fn new(value: T) -> Self {
-        Self {
-            inner: RefCell::new(value),
-        }
-    }
-
-    /// Panic if the data has been borrowed.
-    pub fn exclusive_access(&self) -> UPIntrRefMut<'_, T> {
-        INTR_MASKING_INFO.get_mut().enter();
-        UPIntrRefMut(Some(self.inner.borrow_mut()))
-    }
-
-    pub fn exclusive_session<F, V>(&self, f: F) -> V
-    where
-        F: FnOnce(&mut T) -> V,
-    {
-        let mut inner = self.exclusive_access();
-        f(inner.deref_mut())
-    }
-}
-
-impl<'a, T> Drop for UPIntrRefMut<'a, T> {
-    fn drop(&mut self) {
-        self.0 = None;
-        INTR_MASKING_INFO.get_mut().exit();
-    }
-}
-
-impl<'a, T> Deref for UPIntrRefMut<'a, T> {
-    type Target = T;
-    fn deref(&self) -> &Self::Target {
-        self.0.as_ref().unwrap().deref()
-    }
-}
-impl<'a, T> DerefMut for UPIntrRefMut<'a, T> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        self.0.as_mut().unwrap().deref_mut()
-    }
-}
+}
\ No newline at end of file
diff --git a/os/src/syscall/process.rs b/os/src/syscall/process.rs
index 7d5b67ab..3c3dafdb 100644
--- a/os/src/syscall/process.rs
+++ b/os/src/syscall/process.rs
@@ -55,8 +55,11 @@ pub fn sys_exec(path: *const u8, mut args: *const usize) -> isize {
             args = args.add(1);
         }
     }
+    println!("sys_exec :1");
     if let Some(app_inode) = open_file(path.as_str(), OpenFlags::RDONLY) {
+        println!("sys_exec :2");
         let all_data = app_inode.read_all();
+        println!("sys_exec :3");
         let process = current_process();
         let argc = args_vec.len();
         process.exec(all_data.as_slice(), args_vec);
diff --git a/user/src/bin/usertests2.rs b/user/src/bin/usertests2.rs
new file mode 100644
index 00000000..b9ee9dfc
--- /dev/null
+++ b/user/src/bin/usertests2.rs
@@ -0,0 +1,55 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+
+const TESTS: &[&str] = &[
+    "hello_world\0",
+    "yield\0",
+    "exit\0",
+    "forktest_simple\0",
+    "forktest\0",
+    "forktest2\0",
+    "forktree\0",
+    "filetest_simple\0",
+    "cat\0",
+    "pipetest\0",
+    "mpsc_sem\0",
+    "phil_din_mutex\0",
+    "adder_mutex_spin\0",
+    "condsync_sem\0",
+    "condsync_condvar\0",
+    "threads\0",
+    "threads_arg\0",
+];
+
+const TEST_NUM: usize = TESTS.len();
+
+use user_lib::{exec, fork, waitpid};
+
+#[no_mangle]
+pub fn main() -> i32 {
+    let mut pids = [0; TEST_NUM];
+    for (i, &test) in TESTS.iter().enumerate() {
+        println!("Usertests: Running {}", test);
+        let pid = fork();
+        if pid == 0 {
+            exec(&*test, &[core::ptr::null::<u8>()]);
+            panic!("unreachable!");
+        } else {
+            pids[i] = pid;
+        }
+    }
+    let mut xstate: i32 = Default::default();
+    for (i, &test) in TESTS.iter().enumerate() {
+        let wait_pid = waitpid(pids[i] as usize, &mut xstate);
+        assert_eq!(pids[i], wait_pid);
+        println!(
+            "\x1b[32mUsertests: Test {} in Process {} exited with code {}\x1b[0m",
+            test, pids[i], xstate
+        );
+    }
+    println!("Basic usertests passed!");
+    0
+}