Refactor sleeplock to remove raw pointers

kernel/bio.c

@@ -106,8 +106,6 @@ bread(uint dev, uint blockno)
 void
 bwrite(struct buf *b)
 {
-  if(!holdingsleep(&b->lock))
-    panic("bwrite");
   virtio_disk_rw(b, 1);
 }
 
@@ -116,9 +114,6 @@ bwrite(struct buf *b)
 void
 brelse(struct buf *b)
 {
-  if(!holdingsleep(&b->lock))
-    panic("brelse");
-
   releasesleep(&b->lock);
 
   acquire(&bcache.lock);

kernel/defs.h

@@ -125,8 +125,7 @@ void            pop_off(void);
 
 // sleeplock.c
 void            acquiresleep(struct sleeplock*);
-void            releasesleep(struct sleeplock*);
-int             holdingsleep(struct sleeplock*);
+void releasesleep(struct sleeplock *);
 void            initsleeplock(struct sleeplock*, char*);
 
 // string.c

kernel/fs.c

@@ -317,10 +317,11 @@ ilock(struct inode *ip)
 }
 
 // Unlock the given inode.
+// Caller should hold ip->lock
 void
 iunlock(struct inode *ip)
 {
-  if(ip == 0 || !holdingsleep(&ip->lock) || ip->ref < 1)
+  if (ip == 0 || ip->ref < 1)
     panic("iunlock");
 
   releasesleep(&ip->lock);

kernel/ramdisk.c

@@ -16,11 +16,10 @@ void ramdiskinit(void);
 
 // If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.
 // Else if B_VALID is not set, read buf from disk, set B_VALID.
+// Caller should hold b->lock
 void
 ramdiskrw(struct buf *b)
 {
-  if(!holdingsleep(&b->lock))
-    panic("ramdiskrw: buf not locked");
   if((b->flags & (B_VALID|B_DIRTY)) == B_VALID)
     panic("ramdiskrw: nothing to do");
 

kernel/rustkernel/src/proc.rs

@@ -391,6 +391,21 @@ pub unsafe fn sleep_mutex<T>(chan: *mut c_void, mutex: &mut SpinMutexGuard<T>) {
     core::mem::forget(guard);
 }
 
+/// Sleep until `wakeup(chan)` is called somewhere else.
+pub unsafe fn sleep(chan: *mut c_void) {
+    let p = myproc();
+    let _guard = (*p).lock.lock();
+
+    // Go to sleep.
+    (*p).chan = chan;
+    (*p).state = ProcState::Sleeping;
+
+    sched();
+
+    // Tidy up.
+    (*p).chan = null_mut();
+}
+
 /// Kill the process with the given pid.
 /// The victim won't exit until it tries to return
 /// to user space (see usertrap() in trap.c).

kernel/rustkernel/src/sync/sleeplock.rs

@@ -1,53 +1,27 @@
-use crate::{
-    proc::{myproc, sleep_lock, wakeup},
-    sync::spinlock::Spinlock,
-};
+use crate::proc::{wakeup, sleep};
 use core::{
     ffi::c_char,
-    ptr::{addr_of, null_mut},
+    ptr::addr_of,
+    sync::atomic::{AtomicBool, Ordering},
 };
 
 #[repr(C)]
+#[derive(Default)]
 pub struct Sleeplock {
-    pub locked: u32,
-    pub inner: Spinlock,
-    pub name: *mut c_char,
-    pub pid: i32,
+    pub locked: AtomicBool,
 }
 impl Sleeplock {
-    pub const unsafe fn uninitialized() -> Sleeplock {
+    pub const fn new() -> Sleeplock {
         Sleeplock {
-            locked: 0,
-            inner: Spinlock::new(),
-            name: null_mut(),
-            pid: 0,
+            locked: AtomicBool::new(false),
         }
     }
-    /// Initializes a `Sleeplock`.
-    pub const fn new(name: *mut c_char) -> Sleeplock {
-        Sleeplock {
-            locked: 0,
-            inner: Spinlock::new(),
-            name,
-            pid: 0,
-        }
-    }
-    /// Check whether this proc is holding the lock.
-    pub fn held_by_current_proc(&self) -> bool {
-        self.locked > 0 && self.pid == unsafe { (*myproc()).pid }
-    }
     #[allow(clippy::while_immutable_condition)]
     pub unsafe fn lock_unguarded(&self) {
-        let _guard = self.inner.lock();
-        while self.locked > 0 {
-            sleep_lock(
-                addr_of!(*self).cast_mut().cast(),
-                addr_of!(self.inner).cast_mut().cast(),
-            );
+        while self.locked.swap(true, Ordering::Acquire) {
+            // Put the process to sleep until it gets released.
+            sleep(addr_of!(*self).cast_mut().cast());
         }
-        let this: &mut Self = &mut *addr_of!(*self).cast_mut();
-        this.locked = 1;
-        this.pid = (*myproc()).pid;
     }
     pub fn lock(&self) -> SleeplockGuard<'_> {
         unsafe {
@@ -56,10 +30,7 @@ impl Sleeplock {
         SleeplockGuard { lock: self }
     }
     pub unsafe fn unlock(&self) {
-        let _guard = self.inner.lock();
-        let this: &mut Self = &mut *addr_of!(*self).cast_mut();
-        this.locked = 0;
-        this.pid = 0;
+        self.locked.store(false, Ordering::Release);
         wakeup(addr_of!(*self).cast_mut().cast());
     }
 }
@@ -74,8 +45,8 @@ impl<'l> Drop for SleeplockGuard<'l> {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn initsleeplock(lock: *mut Sleeplock, name: *mut c_char) {
-    (*lock) = Sleeplock::new(name);
+pub unsafe extern "C" fn initsleeplock(lock: *mut Sleeplock, _name: *mut c_char) {
+    (*lock) = Sleeplock::new();
 }
 
 #[no_mangle]
@@ -87,12 +58,3 @@ pub unsafe extern "C" fn acquiresleep(lock: *mut Sleeplock) {
 pub unsafe extern "C" fn releasesleep(lock: *mut Sleeplock) {
     (*lock).unlock();
 }
-
-#[no_mangle]
-pub unsafe extern "C" fn holdingsleep(lock: *mut Sleeplock) -> i32 {
-    if (*lock).held_by_current_proc() {
-        1
-    } else {
-        0
-    }
-}

kernel/sleeplock.h

@@ -4,11 +4,7 @@
 
 // Long-term locks for processes
 struct sleeplock {
-  uint locked;       // Is the lock held?
-  struct spinlock lk; // spinlock protecting this sleep lock
-  
-  // For debugging:
-  char *name;        // Name of lock.
-  int pid;           // Process holding lock
+  // Is the lock held?
+  uint8 locked;
 };