[PATCH v4 02/17] rust: sync: completion: add wait_for_completion_timeout()

[John Hubbard <jhubbard@nvidia.com>]

From: Joel Fernandes <joelagnelf@nvidia.com>

A driver that runs an interrupt self-test during probe waits for the
handler to fire. wait_for_completion() has no timeout, so a broken
interrupt path stalls probe indefinitely. Add a timeout variant of
wait_for_completion().

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
[jhubbard: return the remaining jiffies]
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 rust/kernel/sync/completion.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/sync/completion.rs b/rust/kernel/sync/completion.rs
index 35ff049ff078..7e8b3c1c880e 100644
--- a/rust/kernel/sync/completion.rs
+++ b/rust/kernel/sync/completion.rs
@@ -6,7 +6,12 @@
 //!
 //! C header: [`include/linux/completion.h`](srctree/include/linux/completion.h)
 
-use crate::{bindings, prelude::*, types::Opaque};
+use crate::{
+    bindings,
+    prelude::*,
+    time::Jiffies,
+    types::Opaque, //
+};
 
 /// Synchronization primitive to signal when a certain task has been completed.
 ///
@@ -111,4 +116,20 @@ pub fn wait_for_completion(&self) {
         // SAFETY: `self.as_raw()` is a pointer to a valid `struct completion`.
         unsafe { bindings::wait_for_completion(self.as_raw()) };
     }
+
+    /// Wait for completion of a task, with a timeout.
+    ///
+    /// This method waits for the completion of a task, or until `timeout` elapses. It is not
+    /// interruptible. Returns the number of jiffies left when the task completed, or [`None`] if
+    /// `timeout` elapsed first.
+    ///
+    /// See also [`Completion::complete_all`].
+    #[inline]
+    pub fn wait_for_completion_timeout(&self, timeout: Jiffies) -> Option<Jiffies> {
+        // SAFETY: `self.as_raw()` is a pointer to a valid `struct completion`.
+        match unsafe { bindings::wait_for_completion_timeout(self.as_raw(), timeout) } {
+            0 => None,
+            remaining => Some(remaining),
+        }
+    }
 }
-- 
2.55.0