From: Viresh Kumar <viresh.kumar@linaro.org>
Date: Mon, 9 Jun 2025 11:14:16 +0000 (+0530)
Subject: rust: cpu: Add CpuId::current() to retrieve current CPU ID
X-Git-Tag: v6.16-rc2~11^2~2^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c7f005f70d22cd5613cac30bf6d34867189e36a9;p=thirdparty%2Fkernel%2Flinux.git

rust: cpu: Add CpuId::current() to retrieve current CPU ID

Introduce `CpuId::current()`, a constructor that wraps the C function
`raw_smp_processor_id()` to retrieve the current CPU identifier without
guaranteeing stability.

This function should be used only when the caller can ensure that
the CPU ID won't change unexpectedly due to preemption or migration.

Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
---

diff --git a/MAINTAINERS b/MAINTAINERS
index a92290fffa16..4255186784c4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6254,6 +6254,7 @@ F:	include/linux/cpuhotplug.h
 F:	include/linux/smpboot.h
 F:	kernel/cpu.c
 F:	kernel/smpboot.*
+F:	rust/helper/cpu.c
 F:	rust/kernel/cpu.rs
 
 CPU IDLE TIME MANAGEMENT FRAMEWORK
diff --git a/rust/helpers/cpu.c b/rust/helpers/cpu.c
new file mode 100644
index 000000000000..824e0adb19d4
--- /dev/null
+++ b/rust/helpers/cpu.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/smp.h>
+
+unsigned int rust_helper_raw_smp_processor_id(void)
+{
+	return raw_smp_processor_id();
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 0f1b5d115985..16fa9bca5949 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -13,6 +13,7 @@
 #include "build_assert.c"
 #include "build_bug.c"
 #include "clk.c"
+#include "cpu.c"
 #include "cpufreq.c"
 #include "cpumask.c"
 #include "cred.c"
diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs
index abc780d7a8ec..b75403b0eb56 100644
--- a/rust/kernel/cpu.rs
+++ b/rust/kernel/cpu.rs
@@ -102,6 +102,17 @@ impl CpuId {
     pub fn as_u32(&self) -> u32 {
         self.0
     }
+
+    /// Returns the ID of the CPU the code is currently running on.
+    ///
+    /// The returned value is considered unstable because it may change
+    /// unexpectedly due to preemption or CPU migration. It should only be
+    /// used when the context ensures that the task remains on the same CPU
+    /// or the users could use a stale (yet valid) CPU ID.
+    pub fn current() -> Self {
+        // SAFETY: raw_smp_processor_id() always returns a valid CPU ID.
+        unsafe { Self::from_u32_unchecked(bindings::raw_smp_processor_id()) }
+    }
 }
 
 impl From<CpuId> for u32 {