linux-kernel - Re: [PATCH v3 2/2] rust: task: Add Rust version of might

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Message-Id: <20250617.214207.1883960660906763456.fujita.tomonori@gmail.com>
Date: Tue, 17 Jun 2025 21:42:07 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: miguel.ojeda.sandonis@...il.com, boqun.feng@...il.com
Cc: fujita.tomonori@...il.com, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org, ojeda@...nel.org, alex.gaynor@...il.com,
 gary@...yguo.net, bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
 a.hindborg@...sung.com, aliceryhl@...gle.com, tmgross@...ch.edu,
 dakr@...nel.org, mingo@...hat.com, peterz@...radead.org,
 juri.lelli@...hat.com, vincent.guittot@...aro.org,
 dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, vschneid@...hat.com, pmladek@...e.com, mingo@...nel.org
Subject: Re: [PATCH v3 2/2] rust: task: Add Rust version of might_sleep()

On Tue, 17 Jun 2025 10:02:22 +0200
Miguel Ojeda <miguel.ojeda.sandonis@...il.com> wrote:

> On Tue, Jun 17, 2025 at 5:05 AM FUJITA Tomonori
> <fujita.tomonori@...il.com> wrote:
>>
>> How about adding a link to the header file where the might_sleep macro
>> is defined, like this?
> 
> Sounds good to me. Though, for APIs that have rendered docs, we
> typically point to those instead:
> 
>     https://docs.kernel.org/driver-api/basics.html#c.might_sleep

Ah, somehow, I overlooked that. Thanks!

Boqun, here is the revised version.

diff --git a/rust/helpers/task.c b/rust/helpers/task.c
index 31c33ea2dce6..2c85bbc2727e 100644
--- a/rust/helpers/task.c
+++ b/rust/helpers/task.c
@@ -1,7 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <linux/kernel.h>
 #include <linux/sched/task.h>
 
+void rust_helper_might_resched(void)
+{
+	might_resched();
+}
+
 struct task_struct *rust_helper_get_current(void)
 {
 	return current;
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 834368313088..b79d19deb02e 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -400,3 +400,27 @@ fn eq(&self, other: &Kuid) -> bool {
 }
 
 impl Eq for Kuid {}
+
+/// Annotation for functions that can sleep.
+///
+/// Equivalent to the C side [`might_sleep`] macro, this function serves as
+/// a debugging aid and a potential scheduling point.
+///
+/// This function can only be used in a nonatomic context.
+///
+/// [`might_sleep`]: https://docs.kernel.org/driver-api/basics.html#c.might_sleep
+#[track_caller]
+#[inline]
+pub fn might_sleep() {
+    #[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)]
+    {
+        let loc = core::panic::Location::caller();
+        let file = kernel::file_from_location(loc);
+
+        // SAFETY: `file.as_ptr()` is valid for reading and guaranteed to be nul-terminated.
+        unsafe { crate::bindings::__might_sleep(file.as_ptr().cast(), loc.line() as i32) }
+    }
+
+    // SAFETY: Always safe to call.
+    unsafe { crate::bindings::might_resched() }
+}