Revert "Split wait queue mutex"

src/sync/wait_queue.rs

@@ -2,7 +2,7 @@ use alloc::collections::VecDeque;
 use syscall::{EAGAIN, EINTR};
 
 use crate::{
-    sync::{CleanLockToken, LockToken, Mutex, MutexGuard, WaitCondition, L1, L2, L3},
+    sync::{CleanLockToken, LockToken, Mutex, WaitCondition, L1, L2},
     syscall::{
         error::{Error, Result, EINVAL},
         usercopy::UserSliceWo,
@@ -11,24 +11,20 @@ use crate::{
 
 #[derive(Debug)]
 pub struct WaitQueue<T> {
-    incoming: Mutex<L3, VecDeque<T>>,
-    outgoing: Mutex<L2, VecDeque<T>>,
+    inner: Mutex<L2, VecDeque<T>>,
     pub condition: WaitCondition,
 }
 
 impl<T> WaitQueue<T> {
     pub const fn new() -> WaitQueue<T> {
         WaitQueue {
-            incoming: Mutex::new(VecDeque::new()),
-            outgoing: Mutex::new(VecDeque::new()),
+            inner: Mutex::new(VecDeque::new()),
             condition: WaitCondition::new(),
         }
     }
-
     pub fn is_currently_empty(&self, token: &mut CleanLockToken) -> bool {
-        self.incoming.lock(token.token()).is_empty() && self.outgoing.lock(token.token()).is_empty()
+        self.inner.lock(token.token()).is_empty()
     }
-
     pub fn receive_into_user(
         &self,
         buf: UserSliceWo,
@@ -36,42 +32,17 @@ impl<T> WaitQueue<T> {
         reason: &'static str,
         token: &mut CleanLockToken,
     ) -> Result<usize> {
-        let mut out_guard = self.outgoing.lock(token.token());
         loop {
-            let (mut outgoing, mut token) = out_guard.into_split();
-            if !outgoing.is_empty() {
-                let (s1, s2) = outgoing.as_slices();
-                let s1_bytes = unsafe {
-                    core::slice::from_raw_parts(s1.as_ptr().cast::<u8>(), size_of_val(s1))
-                };
-                let s2_bytes = unsafe {
-                    core::slice::from_raw_parts(s2.as_ptr().cast::<u8>(), size_of_val(s2))
-                };
+            let inner = self.inner.lock(token.token());
+            let (mut inner, mut token) = inner.into_split();
 
-                let mut bytes_copied = buf.copy_common_bytes_from_slice(s1_bytes)?;
-
-                if let Some(buf_for_s2) = buf.advance(s1_bytes.len()) {
-                    bytes_copied += buf_for_s2.copy_common_bytes_from_slice(s2_bytes)?;
-                }
-
-                let _ = outgoing.drain(..bytes_copied / size_of::<T>());
-                return Ok(bytes_copied);
-            }
-
-            let mut incoming = self.incoming.lock(token.token());
-
-            if incoming.is_empty() {
+            if inner.is_empty() {
                 if block {
-                    drop(incoming);
                     // SAFETY: Uses wait_inner because this inner is L2. It's guaranteed there's no other
                     // lock held at this point because clean token is provided from caller.
-                    if !self
-                        .condition
-                        .wait_inner(outgoing, reason, &mut token.token())
-                    {
+                    if !self.condition.wait_inner(inner, reason, &mut token) {
                         return Err(Error::new(EINTR));
                     }
-                    out_guard = unsafe { self.outgoing.relock(token) };
                     continue;
                 } else if buf.is_empty() {
                     return Ok(0);
@@ -83,10 +54,21 @@ impl<T> WaitQueue<T> {
                 }
             }
 
-            core::mem::swap(&mut *incoming, &mut outgoing);
-            drop(incoming);
+            let (s1, s2) = inner.as_slices();
+            let s1_bytes =
+                unsafe { core::slice::from_raw_parts(s1.as_ptr().cast::<u8>(), size_of_val(s1)) };
+            let s2_bytes =
+                unsafe { core::slice::from_raw_parts(s2.as_ptr().cast::<u8>(), size_of_val(s2)) };
 
-            out_guard = MutexGuard::from_split(outgoing, token);
+            let mut bytes_copied = buf.copy_common_bytes_from_slice(s1_bytes)?;
+
+            if let Some(buf_for_s2) = buf.advance(s1_bytes.len()) {
+                bytes_copied += buf_for_s2.copy_common_bytes_from_slice(s2_bytes)?;
+            }
+
+            let _ = inner.drain(..bytes_copied / size_of::<T>());
+
+            return Ok(bytes_copied);
         }
     }
 
@@ -96,7 +78,7 @@ impl<T> WaitQueue<T> {
 
     pub fn send_locked(&self, value: T, mut token: LockToken<'_, L1>) -> usize {
         let len = {
-            let mut inner = self.incoming.lock(token.token());
+            let mut inner = self.inner.lock(token.token());
             inner.push_back(value);
             inner.len()
         };