[GIT PULL] [PATCH 1/4] Rust atomics & locking changes for v6.19

[GIT PULL] [PATCH 1/4] Rust atomics & locking changes for v6.19

[Boqun Feng]

Hi Peter & Ingo,

Please pull this Rust atomics + locking changes for v6.19, it's fairly
simple and small for this cycle ;-)

The following changes since commit b94d45b6bbb42571ec225d3be0e7457c8765a5b4:

  seqlock: Allow KASAN to fail optimizing (2025-10-28 09:58:57 +0100)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git tags/rust-locking.2025.11.13

for you to fetch changes up to 3572e2edc7b611d0b564c487bafda04b5dbb5134:

  locking/mutex: Redo __mutex_init() (2025-11-12 08:56:42 -0800)

Regards,
Boqun

----------------------------------------------------------------
Rust atomic changes for v6.19:

- Replace Rust native atomics with LKMM atomics in debugfs

Locking changes for v6.19:

- Redo __mutex_init() to allow compiler removing unused parameters
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----------------------------------------------------------------
Boqun Feng (3):
      rust: sync: atomic: Make Atomic*Ops pub(crate)
      rust: sync: atomic: Implement Debug for Atomic<Debug>
      rust: debugfs: Replace the usage of Rust native atomics

Sebastian Andrzej Siewior (1):
      locking/mutex: Redo __mutex_init()

 include/linux/mutex.h               | 45 ++++++++++++++++++++++++-------
 kernel/locking/mutex.c              | 22 ++++++++++-----
 kernel/locking/rtmutex_api.c        | 19 ++++++++++---
 rust/kernel/debugfs/traits.rs       | 53 ++++++++++++-------------------------
 rust/kernel/sync/atomic.rs          | 12 ++++++++-
 samples/rust/rust_debugfs.rs        | 12 ++++-----
 samples/rust/rust_debugfs_scoped.rs |  6 ++---
 7 files changed, 102 insertions(+), 67 deletions(-)

[PATCH 1/4] rust: sync: atomic: Make Atomic*Ops pub(crate)

[Boqun Feng]

In order to write code over a generate Atomic<T> we need to make
Atomic*Ops public so that functions like `.load()` and `.store()` are
available. Make these pub(crate) at the beginning so the usage in kernel
crate is supported.

Tested-by: David Gow <davidgow@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251022035324.70785-2-boqun.feng@gmail.com
---
 rust/kernel/sync/atomic.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
index 016a6bcaf080..0bc6e7b04d67 100644
--- a/rust/kernel/sync/atomic.rs
+++ b/rust/kernel/sync/atomic.rs
@@ -22,9 +22,10 @@
 
 pub use internal::AtomicImpl;
 pub use ordering::{Acquire, Full, Relaxed, Release};
+pub(crate) use internal::{AtomicArithmeticOps, AtomicBasicOps, AtomicExchangeOps};
 
 use crate::build_error;
-use internal::{AtomicArithmeticOps, AtomicBasicOps, AtomicExchangeOps, AtomicRepr};
+use internal::AtomicRepr;
 use ordering::OrderingType;
 
 /// A memory location which can be safely modified from multiple execution contexts.
-- 
2.50.1 (Apple Git-155)

[PATCH 2/4] rust: sync: atomic: Implement Debug for Atomic<Debug>

[Boqun Feng]

If `Atomic<T>` is `Debug` then it's a `debugfs::Writer`, therefore make
it so since 1) debugfs needs to support `Atomic<T>` and 2) it's rather
trivial to implement `Debug` for `Atomic<Debug>`.

Tested-by: David Gow <davidgow@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251022035324.70785-3-boqun.feng@gmail.com
---
 rust/kernel/sync/atomic.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
index 0bc6e7b04d67..3afc376be42d 100644
--- a/rust/kernel/sync/atomic.rs
+++ b/rust/kernel/sync/atomic.rs
@@ -307,6 +307,15 @@ pub fn store<Ordering: ordering::ReleaseOrRelaxed>(&self, v: T, _: Ordering) {
     }
 }
 
+impl<T: AtomicType + core::fmt::Debug> core::fmt::Debug for Atomic<T>
+where
+    T::Repr: AtomicBasicOps,
+{
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        core::fmt::Debug::fmt(&self.load(Relaxed), f)
+    }
+}
+
 impl<T: AtomicType> Atomic<T>
 where
     T::Repr: AtomicExchangeOps,
-- 
2.50.1 (Apple Git-155)

[PATCH 3/4] rust: debugfs: Replace the usage of Rust native atomics

[Boqun Feng]

Rust native atomics are not allowed to use in kernel due to the mismatch
of memory model with Linux kernel memory model, hence remove the usage
of Rust native atomics in debufs.

Reviewed-by: Matthew Maurer <mmaurer@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Tested-by: David Gow <davidgow@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251022035324.70785-4-boqun.feng@gmail.com
---
 rust/kernel/debugfs/traits.rs       | 53 +++++++++--------------------
 samples/rust/rust_debugfs.rs        | 12 +++----
 samples/rust/rust_debugfs_scoped.rs |  6 ++--
 3 files changed, 25 insertions(+), 46 deletions(-)

diff --git a/rust/kernel/debugfs/traits.rs b/rust/kernel/debugfs/traits.rs
index ba7ec5a900b8..92054fed2136 100644
--- a/rust/kernel/debugfs/traits.rs
+++ b/rust/kernel/debugfs/traits.rs
@@ -4,14 +4,11 @@
 //! Traits for rendering or updating values exported to DebugFS.
 
 use crate::prelude::*;
+use crate::sync::atomic::{Atomic, AtomicBasicOps, AtomicType, Relaxed};
 use crate::sync::Mutex;
 use crate::uaccess::UserSliceReader;
 use core::fmt::{self, Debug, Formatter};
 use core::str::FromStr;
-use core::sync::atomic::{
-    AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU64,
-    AtomicU8, AtomicUsize, Ordering,
-};
 
 /// A trait for types that can be written into a string.
 ///
@@ -66,37 +63,21 @@ fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
     }
 }
 
-macro_rules! impl_reader_for_atomic {
-    ($(($atomic_type:ty, $int_type:ty)),*) => {
-        $(
-            impl Reader for $atomic_type {
-                fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
-                    let mut buf = [0u8; 21]; // Enough for a 64-bit number.
-                    if reader.len() > buf.len() {
-                        return Err(EINVAL);
-                    }
-                    let n = reader.len();
-                    reader.read_slice(&mut buf[..n])?;
+impl<T: AtomicType + FromStr> Reader for Atomic<T>
+where
+    T::Repr: AtomicBasicOps,
+{
+    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
+        let mut buf = [0u8; 21]; // Enough for a 64-bit number.
+        if reader.len() > buf.len() {
+            return Err(EINVAL);
+        }
+        let n = reader.len();
+        reader.read_slice(&mut buf[..n])?;
 
-                    let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
-                    let val = s.trim().parse::<$int_type>().map_err(|_| EINVAL)?;
-                    self.store(val, Ordering::Relaxed);
-                    Ok(())
-                }
-            }
-        )*
-    };
+        let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
+        let val = s.trim().parse::<T>().map_err(|_| EINVAL)?;
+        self.store(val, Relaxed);
+        Ok(())
+    }
 }
-
-impl_reader_for_atomic!(
-    (AtomicI16, i16),
-    (AtomicI32, i32),
-    (AtomicI64, i64),
-    (AtomicI8, i8),
-    (AtomicIsize, isize),
-    (AtomicU16, u16),
-    (AtomicU32, u32),
-    (AtomicU64, u64),
-    (AtomicU8, u8),
-    (AtomicUsize, usize)
-);
diff --git a/samples/rust/rust_debugfs.rs b/samples/rust/rust_debugfs.rs
index 82b61a15a34b..711faa07bece 100644
--- a/samples/rust/rust_debugfs.rs
+++ b/samples/rust/rust_debugfs.rs
@@ -32,14 +32,12 @@
 //! ```
 
 use core::str::FromStr;
-use core::sync::atomic::AtomicUsize;
-use core::sync::atomic::Ordering;
 use kernel::c_str;
 use kernel::debugfs::{Dir, File};
 use kernel::new_mutex;
 use kernel::prelude::*;
+use kernel::sync::atomic::{Atomic, Relaxed};
 use kernel::sync::Mutex;
-
 use kernel::{acpi, device::Core, of, platform, str::CString, types::ARef};
 
 kernel::module_platform_driver! {
@@ -59,7 +57,7 @@ struct RustDebugFs {
     #[pin]
     _compatible: File<CString>,
     #[pin]
-    counter: File<AtomicUsize>,
+    counter: File<Atomic<usize>>,
     #[pin]
     inner: File<Mutex<Inner>>,
 }
@@ -109,7 +107,7 @@ fn probe(
     ) -> Result<Pin<KBox<Self>>> {
         let result = KBox::try_pin_init(RustDebugFs::new(pdev), GFP_KERNEL)?;
         // We can still mutate fields through the files which are atomic or mutexed:
-        result.counter.store(91, Ordering::Relaxed);
+        result.counter.store(91, Relaxed);
         {
             let mut guard = result.inner.lock();
             guard.x = guard.y;
@@ -120,8 +118,8 @@ fn probe(
 }
 
 impl RustDebugFs {
-    fn build_counter(dir: &Dir) -> impl PinInit<File<AtomicUsize>> + '_ {
-        dir.read_write_file(c_str!("counter"), AtomicUsize::new(0))
+    fn build_counter(dir: &Dir) -> impl PinInit<File<Atomic<usize>>> + '_ {
+        dir.read_write_file(c_str!("counter"), Atomic::<usize>::new(0))
     }
 
     fn build_inner(dir: &Dir) -> impl PinInit<File<Mutex<Inner>>> + '_ {
diff --git a/samples/rust/rust_debugfs_scoped.rs b/samples/rust/rust_debugfs_scoped.rs
index b0c4e76b123e..9f0ec5f24cda 100644
--- a/samples/rust/rust_debugfs_scoped.rs
+++ b/samples/rust/rust_debugfs_scoped.rs
@@ -6,9 +6,9 @@
 //! `Scope::dir` to create a variety of files without the need to separately
 //! track them all.
 
-use core::sync::atomic::AtomicUsize;
 use kernel::debugfs::{Dir, Scope};
 use kernel::prelude::*;
+use kernel::sync::atomic::Atomic;
 use kernel::sync::Mutex;
 use kernel::{c_str, new_mutex, str::CString};
 
@@ -62,7 +62,7 @@ fn create_file_write(
     let file_name = CString::try_from_fmt(fmt!("{name_str}"))?;
     for sub in items {
         nums.push(
-            AtomicUsize::new(sub.parse().map_err(|_| EINVAL)?),
+            Atomic::<usize>::new(sub.parse().map_err(|_| EINVAL)?),
             GFP_KERNEL,
         )?;
     }
@@ -109,7 +109,7 @@ fn init(device_dir: Dir) -> impl PinInit<Self> {
 
 struct DeviceData {
     name: CString,
-    nums: KVec<AtomicUsize>,
+    nums: KVec<Atomic<usize>>,
 }
 
 fn init_control(base_dir: &Dir, dyn_dirs: Dir) -> impl PinInit<Scope<ModuleData>> + '_ {
-- 
2.50.1 (Apple Git-155)

[PATCH 4/4] locking/mutex: Redo __mutex_init()

[Boqun Feng]

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

mutex_init() invokes __mutex_init() providing the name of the lock and
a pointer to a the lock class. With LOCKDEP enabled this information is
useful but without LOCKDEP it not used at all. Passing the pointer
information of the lock class might be considered negligible but the
name of the lock is passed as well and the string is stored. This
information is wasting storage.

Split __mutex_init() into a _genereic() variant doing the initialisation
of the lock and a _lockdep() version which does _genereic() plus the
lockdep bits. Restrict the lockdep version to lockdep enabled builds
allowing the compiler to remove the unused parameter.

This results in the following size reduction:

      text     data       bss        dec  filename
| 30237599  8161430   1176624   39575653  vmlinux.defconfig
| 30233269  8149142   1176560   39558971  vmlinux.defconfig.patched
   -4.2KiB   -12KiB

| 32455099  8471098  12934684   53860881  vmlinux.defconfig.lockdep
| 32455100  8471098  12934684   53860882  vmlinux.defconfig.patched.lockdep

| 27152407  7191822   2068040   36412269  vmlinux.defconfig.preempt_rt
| 27145937  7183630   2067976   36397543  vmlinux.defconfig.patched.preempt_rt
   -6.3KiB    -8KiB

| 29382020  7505742  13784608   50672370  vmlinux.defconfig.preempt_rt.lockdep
| 29376229  7505742  13784544   50666515  vmlinux.defconfig.patched.preempt_rt.lockdep
   -5.6KiB

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251105142350.Tfeevs2N@linutronix.de
---
 include/linux/mutex.h        | 45 ++++++++++++++++++++++++++++--------
 kernel/locking/mutex.c       | 22 +++++++++++++-----
 kernel/locking/rtmutex_api.c | 19 +++++++++++----
 3 files changed, 66 insertions(+), 20 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 847b81ca6436..bf535f0118bb 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -86,8 +86,23 @@ do {									\
 #define DEFINE_MUTEX(mutexname) \
 	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 
-extern void __mutex_init(struct mutex *lock, const char *name,
-			 struct lock_class_key *key);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+void mutex_init_lockep(struct mutex *lock, const char *name, struct lock_class_key *key);
+
+static inline void __mutex_init(struct mutex *lock, const char *name,
+				struct lock_class_key *key)
+{
+	mutex_init_lockep(lock, name, key);
+}
+#else
+extern void mutex_init_generic(struct mutex *lock);
+
+static inline void __mutex_init(struct mutex *lock, const char *name,
+				struct lock_class_key *key)
+{
+	mutex_init_generic(lock);
+}
+#endif /* !CONFIG_DEBUG_LOCK_ALLOC */
 
 /**
  * mutex_is_locked - is the mutex locked
@@ -111,17 +126,27 @@ extern bool mutex_is_locked(struct mutex *lock);
 #define DEFINE_MUTEX(mutexname)						\
 	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 
-extern void __mutex_rt_init(struct mutex *lock, const char *name,
-			    struct lock_class_key *key);
-
 #define mutex_is_locked(l)	rt_mutex_base_is_locked(&(l)->rtmutex)
 
-#define __mutex_init(mutex, name, key)			\
-do {							\
-	rt_mutex_base_init(&(mutex)->rtmutex);		\
-	__mutex_rt_init((mutex), name, key);		\
-} while (0)
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+extern void mutex_rt_init_lockdep(struct mutex *mutex, const char *name,
+			     struct lock_class_key *key);
+
+static inline void __mutex_init(struct mutex *lock, const char *name,
+				struct lock_class_key *key)
+{
+	mutex_rt_init_lockdep(lock, name, key);
+}
 
+#else
+extern void mutex_rt_init_generic(struct mutex *mutex);
+
+static inline void __mutex_init(struct mutex *lock, const char *name,
+				struct lock_class_key *key)
+{
+	mutex_rt_init_generic(lock);
+}
+#endif /* !CONFIG_LOCKDEP */
 #endif /* CONFIG_PREEMPT_RT */
 
 #ifdef CONFIG_DEBUG_MUTEXES
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index de7d6702cd96..f3bb352a368d 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -43,8 +43,7 @@
 # define MUTEX_WARN_ON(cond)
 #endif
 
-void
-__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
+static void __mutex_init_generic(struct mutex *lock)
 {
 	atomic_long_set(&lock->owner, 0);
 	raw_spin_lock_init(&lock->wait_lock);
@@ -52,10 +51,7 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 	osq_lock_init(&lock->osq);
 #endif
-
-	debug_mutex_init(lock, name, key);
 }
-EXPORT_SYMBOL(__mutex_init);
 
 static inline struct task_struct *__owner_task(unsigned long owner)
 {
@@ -142,6 +138,11 @@ static inline bool __mutex_trylock(struct mutex *lock)
  * There is nothing that would stop spreading the lockdep annotations outwards
  * except more code.
  */
+void mutex_init_generic(struct mutex *lock)
+{
+	__mutex_init_generic(lock);
+}
+EXPORT_SYMBOL(mutex_init_generic);
 
 /*
  * Optimistic trylock that only works in the uncontended case. Make sure to
@@ -166,7 +167,16 @@ static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
 
 	return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);
 }
-#endif
+
+#else /* !CONFIG_DEBUG_LOCK_ALLOC */
+
+void mutex_init_lockep(struct mutex *lock, const char *name, struct lock_class_key *key)
+{
+	__mutex_init_generic(lock);
+	debug_mutex_init(lock, name, key);
+}
+EXPORT_SYMBOL(mutex_init_lockep);
+#endif /* !CONFIG_DEBUG_LOCK_ALLOC */
 
 static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
 {
diff --git a/kernel/locking/rtmutex_api.c b/kernel/locking/rtmutex_api.c
index bafd5af98eae..59dbd29cb219 100644
--- a/kernel/locking/rtmutex_api.c
+++ b/kernel/locking/rtmutex_api.c
@@ -515,13 +515,11 @@ void rt_mutex_debug_task_free(struct task_struct *task)
 
 #ifdef CONFIG_PREEMPT_RT
 /* Mutexes */
-void __mutex_rt_init(struct mutex *mutex, const char *name,
-		     struct lock_class_key *key)
+static void __mutex_rt_init_generic(struct mutex *mutex)
 {
+	rt_mutex_base_init(&mutex->rtmutex);
 	debug_check_no_locks_freed((void *)mutex, sizeof(*mutex));
-	lockdep_init_map_wait(&mutex->dep_map, name, key, 0, LD_WAIT_SLEEP);
 }
-EXPORT_SYMBOL(__mutex_rt_init);
 
 static __always_inline int __mutex_lock_common(struct mutex *lock,
 					       unsigned int state,
@@ -542,6 +540,13 @@ static __always_inline int __mutex_lock_common(struct mutex *lock,
 }
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
+void mutex_rt_init_lockdep(struct mutex *mutex, const char *name, struct lock_class_key *key)
+{
+	__mutex_rt_init_generic(mutex);
+	lockdep_init_map_wait(&mutex->dep_map, name, key, 0, LD_WAIT_SLEEP);
+}
+EXPORT_SYMBOL(mutex_rt_init_lockdep);
+
 void __sched mutex_lock_nested(struct mutex *lock, unsigned int subclass)
 {
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
@@ -598,6 +603,12 @@ int __sched _mutex_trylock_nest_lock(struct mutex *lock,
 EXPORT_SYMBOL_GPL(_mutex_trylock_nest_lock);
 #else /* CONFIG_DEBUG_LOCK_ALLOC */
 
+void mutex_rt_init_generic(struct mutex *mutex)
+{
+	__mutex_rt_init_generic(mutex);
+}
+EXPORT_SYMBOL(mutex_rt_init_generic);
+
 void __sched mutex_lock(struct mutex *lock)
 {
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
-- 
2.50.1 (Apple Git-155)

Re: [GIT PULL] [PATCH 1/4] Rust atomics & locking changes for v6.19

[Peter Zijlstra]

On Thu, Nov 13, 2025 at 10:01:56PM -0800, Boqun Feng wrote:

> Boqun Feng (3):
>       rust: sync: atomic: Make Atomic*Ops pub(crate)
>       rust: sync: atomic: Implement Debug for Atomic<Debug>
>       rust: debugfs: Replace the usage of Rust native atomics
> 
> Sebastian Andrzej Siewior (1):
>       locking/mutex: Redo __mutex_init()

Done, thanks!