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

@@ -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;

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() }
+}