[PATCH v2 2/4] rust: sync: use Delta for CondVar timeout API

[FUJITA Tomonori <tomo@flapping.org>]

From: FUJITA Tomonori <fujita.tomonori@gmail.com>

wait_interruptible_timeout() and CondVarTimeoutResult take/return a
raw jiffies count (a plain c_ulong alias with no type safety). Callers
have to know on their own that the value meant jiffies and convert
to/from it themselves, which is easy to get wrong (e.g. passing a
millisecond value where a jiffies value is expected).

Switch to Delta, the duration type already used elsewhere, so the unit
is part of the type instead of a caller convention.

Use as_jiffies_ceil() rather than a plain truncating conversion: a
caller that passes a nonzero Delta expects the call to actually sleep
for roughly that long (or return earlier via a wakeup or signal).

Update binder's ioctl_freeze(), the only caller, accordingly.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 drivers/android/binder/process.rs | 12 ++++++------
 rust/kernel/sync/condvar.rs       | 20 ++++++++++++--------
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index 96b8440ceac6..cc693484489a 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -1468,25 +1468,25 @@ pub(crate) fn ioctl_freeze(&self, info: &BinderFreezeInfo) -> Result {
         inner.is_frozen = IsFrozen::InProgress;
 
         if info.timeout_ms > 0 {
-            let mut jiffies = kernel::time::msecs_to_jiffies(info.timeout_ms);
-            while jiffies > 0 {
+            let mut delta = kernel::time::Delta::from_millis(info.timeout_ms.into());
+            while !delta.is_zero() {
                 if inner.outstanding_txns == 0 {
                     break;
                 }
 
                 match self
                     .freeze_wait
-                    .wait_interruptible_timeout(&mut inner, jiffies)
+                    .wait_interruptible_timeout(&mut inner, delta)
                 {
                     CondVarTimeoutResult::Signal { .. } => {
                         inner.is_frozen = IsFrozen::No;
                         return Err(ERESTARTSYS);
                     }
-                    CondVarTimeoutResult::Woken { jiffies: remaining } => {
-                        jiffies = remaining;
+                    CondVarTimeoutResult::Woken { delta: remaining } => {
+                        delta = remaining;
                     }
                     CondVarTimeoutResult::Timeout => {
-                        jiffies = 0;
+                        delta = kernel::time::Delta::ZERO;
                     }
                 }
             }
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index 69d58dfbad7b..c94ae83a583f 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -12,7 +12,7 @@
     task::{
         MAX_SCHEDULE_TIMEOUT, TASK_FREEZABLE, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNINTERRUPTIBLE,
     },
-    time::Jiffies,
+    time::Delta,
     types::Opaque,
 };
 use core::{marker::PhantomPinned, pin::Pin, ptr};
@@ -186,15 +186,19 @@ pub fn wait_interruptible_freezable<T: ?Sized, B: Backend>(
     pub fn wait_interruptible_timeout<T: ?Sized, B: Backend>(
         &self,
         guard: &mut Guard<'_, T, B>,
-        jiffies: Jiffies,
+        delta: Delta,
     ) -> CondVarTimeoutResult {
-        let jiffies = jiffies.try_into().unwrap_or(MAX_SCHEDULE_TIMEOUT);
+        let jiffies = c_long::try_from(delta.as_jiffies_ceil()).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 },
+        match (res, crate::current!().signal_pending()) {
+            (jiffies, true) => CondVarTimeoutResult::Signal {
+                delta: Delta::from_jiffies(jiffies as u64),
+            },
             (0, false) => CondVarTimeoutResult::Timeout,
-            (jiffies, false) => CondVarTimeoutResult::Woken { jiffies },
+            (jiffies, false) => CondVarTimeoutResult::Woken {
+                delta: Delta::from_jiffies(jiffies as u64),
+            },
         }
     }
 
@@ -248,11 +252,11 @@ pub enum CondVarTimeoutResult {
     /// Somebody woke us up.
     Woken {
         /// Remaining sleep duration.
-        jiffies: Jiffies,
+        delta: Delta,
     },
     /// A signal occurred.
     Signal {
         /// Remaining sleep duration.
-        jiffies: Jiffies,
+        delta: Delta,
     },
 }
-- 
2.43.0