1 files changed, 88 insertions, 22 deletions

diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index f65e19d5a37c15..0c3671caffeb2f 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -6,8 +6,18 @@
 //! variable.
 
 use super::{lock::Backend, lock::Guard, LockClassKey};
-use crate::{bindings, init::PinInit, pin_init, str::CStr, types::Opaque};
+use crate::{
+    bindings,
+    init::PinInit,
+    pin_init,
+    str::CStr,
+    task::{MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNINTERRUPTIBLE},
+    time::Jiffies,
+    types::Opaque,
+};
+use core::ffi::{c_int, c_long};
 use core::marker::PhantomPinned;
+use core::ptr;
 use macros::pin_data;
 
 /// Creates a [`CondVar`] initialiser with the given name and a newly-created lock class.
@@ -17,6 +27,7 @@ macro_rules! new_condvar {
         $crate::sync::CondVar::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
     };
 }
+pub use new_condvar;
 
 /// A conditional variable.
 ///
@@ -34,8 +45,7 @@ macro_rules! new_condvar {
 /// The following is an example of using a condvar with a mutex:
 ///
 /// ```
-/// use kernel::sync::{CondVar, Mutex};
-/// use kernel::{new_condvar, new_mutex};
+/// use kernel::sync::{new_condvar, new_mutex, CondVar, Mutex};
 ///
 /// #[pin_data]
 /// pub struct Example {
@@ -73,10 +83,12 @@ macro_rules! new_condvar {
 #[pin_data]
 pub struct CondVar {
     #[pin]
-    pub(crate) wait_list: Opaque<bindings::wait_queue_head>,
+    pub(crate) wait_queue_head: Opaque<bindings::wait_queue_head>,
 
     /// A condvar needs to be pinned because it contains a [`struct list_head`] that is
     /// self-referential, so it cannot be safely moved once it is initialised.
+    ///
+    /// [`struct list_head`]: srctree/include/linux/types.h
     #[pin]
     _pin: PhantomPinned,
 }
@@ -96,28 +108,35 @@ impl CondVar {
             _pin: PhantomPinned,
             // SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
             // static lifetimes so they live indefinitely.
-            wait_list <- Opaque::ffi_init(|slot| unsafe {
+            wait_queue_head <- Opaque::ffi_init(|slot| unsafe {
                 bindings::__init_waitqueue_head(slot, name.as_char_ptr(), key.as_ptr())
             }),
         })
     }
 
-    fn wait_internal<T: ?Sized, B: Backend>(&self, wait_state: u32, guard: &mut Guard<'_, T, B>) {
+    fn wait_internal<T: ?Sized, B: Backend>(
+        &self,
+        wait_state: c_int,
+        guard: &mut Guard<'_, T, B>,
+        timeout_in_jiffies: c_long,
+    ) -> c_long {
         let wait = Opaque::<bindings::wait_queue_entry>::uninit();
 
         // SAFETY: `wait` points to valid memory.
         unsafe { bindings::init_wait(wait.get()) };
 
-        // SAFETY: Both `wait` and `wait_list` point to valid memory.
+        // SAFETY: Both `wait` and `wait_queue_head` point to valid memory.
         unsafe {
-            bindings::prepare_to_wait_exclusive(self.wait_list.get(), wait.get(), wait_state as _)
+            bindings::prepare_to_wait_exclusive(self.wait_queue_head.get(), wait.get(), wait_state)
         };
 
-        // SAFETY: No arguments, switches to another thread.
-        guard.do_unlocked(|| unsafe { bindings::schedule() });
+        // SAFETY: Switches to another thread. The timeout can be any number.
+        let ret = guard.do_unlocked(|| unsafe { bindings::schedule_timeout(timeout_in_jiffies) });
+
+        // SAFETY: Both `wait` and `wait_queue_head` point to valid memory.
+        unsafe { bindings::finish_wait(self.wait_queue_head.get(), wait.get()) };
 
-        // SAFETY: Both `wait` and `wait_list` point to valid memory.
-        unsafe { bindings::finish_wait(self.wait_list.get(), wait.get()) };
+        ret
     }
 
     /// Releases the lock and waits for a notification in uninterruptible mode.
@@ -127,7 +146,7 @@ impl CondVar {
     /// [`CondVar::notify_one`] or [`CondVar::notify_all`]. Note that it may also wake up
     /// spuriously.
     pub fn wait<T: ?Sized, B: Backend>(&self, guard: &mut Guard<'_, T, B>) {
-        self.wait_internal(bindings::TASK_UNINTERRUPTIBLE, guard);
+        self.wait_internal(TASK_UNINTERRUPTIBLE, guard, MAX_SCHEDULE_TIMEOUT);
     }
 
     /// Releases the lock and waits for a notification in interruptible mode.
@@ -138,29 +157,60 @@ impl CondVar {
     /// Returns whether there is a signal pending.
     #[must_use = "wait_interruptible returns if a signal is pending, so the caller must check the return value"]
     pub fn wait_interruptible<T: ?Sized, B: Backend>(&self, guard: &mut Guard<'_, T, B>) -> bool {
-        self.wait_internal(bindings::TASK_INTERRUPTIBLE, guard);
+        self.wait_internal(TASK_INTERRUPTIBLE, guard, MAX_SCHEDULE_TIMEOUT);
         crate::current!().signal_pending()
     }
 
-    /// Calls the kernel function to notify the appropriate number of threads with the given flags.
-    fn notify(&self, count: i32, flags: u32) {
-        // SAFETY: `wait_list` points to valid memory.
+    /// Releases the lock and waits for a notification in interruptible mode.
+    ///
+    /// Atomically releases the given lock (whose ownership is proven by the guard) and puts the
+    /// thread to sleep. It wakes up when notified by [`CondVar::notify_one`] or
+    /// [`CondVar::notify_all`], or when a timeout occurs, or when the thread receives a signal.
+    #[must_use = "wait_interruptible_timeout returns if a signal is pending, so the caller must check the return value"]
+    pub fn wait_interruptible_timeout<T: ?Sized, B: Backend>(
+        &self,
+        guard: &mut Guard<'_, T, B>,
+        jiffies: Jiffies,
+    ) -> CondVarTimeoutResult {
+        let jiffies = jiffies.try_into().unwrap_or(MAX_SCHEDULE_TIMEOUT);
+        let res = self.wait_internal(TASK_INTERRUPTIBLE, guard, jiffies);
+
+        match (res as Jiffies, crate::current!().signal_pending()) {
+            (jiffies, true) => CondVarTimeoutResult::Signal { jiffies },
+            (0, false) => CondVarTimeoutResult::Timeout,
+            (jiffies, false) => CondVarTimeoutResult::Woken { jiffies },
+        }
+    }
+
+    /// Calls the kernel function to notify the appropriate number of threads.
+    fn notify(&self, count: c_int) {
+        // SAFETY: `wait_queue_head` points to valid memory.
         unsafe {
             bindings::__wake_up(
-                self.wait_list.get(),
-                bindings::TASK_NORMAL,
+                self.wait_queue_head.get(),
+                TASK_NORMAL,
                 count,
-                flags as _,
+                ptr::null_mut(),
             )
         };
     }
 
+    /// Calls the kernel function to notify one thread synchronously.
+    ///
+    /// This method behaves like `notify_one`, except that it hints to the scheduler that the
+    /// current thread is about to go to sleep, so it should schedule the target thread on the same
+    /// CPU.
+    pub fn notify_sync(&self) {
+        // SAFETY: `wait_queue_head` points to valid memory.
+        unsafe { bindings::__wake_up_sync(self.wait_queue_head.get(), TASK_NORMAL) };
+    }
+
     /// Wakes a single waiter up, if any.
     ///
     /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
     /// completely (as opposed to automatically waking up the next waiter).
     pub fn notify_one(&self) {
-        self.notify(1, 0);
+        self.notify(1);
     }
 
     /// Wakes all waiters up, if any.
@@ -168,6 +218,22 @@ impl CondVar {
     /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
     /// completely (as opposed to automatically waking up the next waiter).
     pub fn notify_all(&self) {
-        self.notify(0, 0);
+        self.notify(0);
     }
 }
+
+/// The return type of `wait_timeout`.
+pub enum CondVarTimeoutResult {
+    /// The timeout was reached.
+    Timeout,
+    /// Somebody woke us up.
+    Woken {
+        /// Remaining sleep duration.
+        jiffies: Jiffies,
+    },
+    /// A signal occurred.
+    Signal {
+        /// Remaining sleep duration.
+        jiffies: Jiffies,
+    },
+}