[tip: sched/core] rust: task: Add Rust version of might_sleep()

["tip-bot2 for FUJITA Tomonori" <tip-bot2@linutronix.de>]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     7e611710acf966df1e14bcf4e067385e38e549a1
Gitweb:        https://git.kernel.org/tip/7e611710acf966df1e14bcf4e067385e38e549a1
Author:        FUJITA Tomonori <fujita.tomonori@gmail.com>
AuthorDate:    Fri, 11 Apr 2025 07:56:23 +09:00
Committer:     Boqun Feng <boqun.feng@gmail.com>
CommitterDate: Tue, 24 Jun 2025 15:53:50 -07:00

rust: task: Add Rust version of might_sleep()

Add a helper function equivalent to the C's might_sleep(), which
serves as a debugging aid and a potential scheduling point.

Note that this function can only be used in a nonatomic context.

This will be used by Rust version of read_poll_timeout().

[boqun: Use file_from_location() to get a C string instead of changing
__might_sleep()]

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20250619151007.61767-3-boqun.feng@gmail.com
---
 rust/helpers/task.c |  6 ++++++
 rust/kernel/task.rs | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/rust/helpers/task.c b/rust/helpers/task.c
index 31c33ea..2c85bbc 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 8343683..7d0935b 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -400,3 +400,27 @@ impl PartialEq for Kuid {
 }
 
 impl Eq for Kuid {}
+
+/// Annotation for functions that can sleep.
+///
+/// Equivalent to the C side [`might_sleep()`], 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() }
+}