linux-kernel - [GIT PULL] locking fixes

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Message-ID: <Z9Pxl-ItRBaAUd9Y@gmail.com>
Date: Fri, 14 Mar 2025 10:06:31 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Will Deacon <will@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>
Subject: [GIT PULL] locking fixes

Linus,

Please pull the latest locking/urgent Git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-2025-03-14

   # HEAD: 85b2b9c16d053364e2004883140538e73b333cdb locking/semaphore: Use wake_q to wake up processes outside lock critical section

Miscellaneous fixes:

 - Restrict the Rust runtime from unintended access
   to dynamically allocated LockClassKeys

 - KernelDoc annotation fix

 - Fix a lock ordering bug in semaphore::up(), related
   to trying to printk() and wake up the console
   within critical sections

 Thanks,

	Ingo

------------------>
Mitchell Levy (1):
      rust: lockdep: Remove support for dynamically allocated LockClassKeys

Randy Dunlap (1):
      locking/rtmutex: Use the 'struct' keyword in kernel-doc comment

Waiman Long (1):
      locking/semaphore: Use wake_q to wake up processes outside lock critical section


 kernel/locking/rtmutex_common.h |  4 ++--
 kernel/locking/semaphore.c      | 13 +++++++++----
 rust/kernel/sync.rs             | 16 ++++------------
 3 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index c38a2d2d4a7e..78dd3d8c6554 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -59,8 +59,8 @@ struct rt_mutex_waiter {
 };
 
 /**
- * rt_wake_q_head - Wrapper around regular wake_q_head to support
- *		    "sleeping" spinlocks on RT
+ * struct rt_wake_q_head - Wrapper around regular wake_q_head to support
+ *			   "sleeping" spinlocks on RT
  * @head:		The regular wake_q_head for sleeping lock variants
  * @rtlock_task:	Task pointer for RT lock (spin/rwlock) wakeups
  */
diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c
index 34bfae72f295..de9117c0e671 100644
--- a/kernel/locking/semaphore.c
+++ b/kernel/locking/semaphore.c
@@ -29,6 +29,7 @@
 #include <linux/export.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
+#include <linux/sched/wake_q.h>
 #include <linux/semaphore.h>
 #include <linux/spinlock.h>
 #include <linux/ftrace.h>
@@ -38,7 +39,7 @@ static noinline void __down(struct semaphore *sem);
 static noinline int __down_interruptible(struct semaphore *sem);
 static noinline int __down_killable(struct semaphore *sem);
 static noinline int __down_timeout(struct semaphore *sem, long timeout);
-static noinline void __up(struct semaphore *sem);
+static noinline void __up(struct semaphore *sem, struct wake_q_head *wake_q);
 
 /**
  * down - acquire the semaphore
@@ -183,13 +184,16 @@ EXPORT_SYMBOL(down_timeout);
 void __sched up(struct semaphore *sem)
 {
 	unsigned long flags;
+	DEFINE_WAKE_Q(wake_q);
 
 	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(list_empty(&sem->wait_list)))
 		sem->count++;
 	else
-		__up(sem);
+		__up(sem, &wake_q);
 	raw_spin_unlock_irqrestore(&sem->lock, flags);
+	if (!wake_q_empty(&wake_q))
+		wake_up_q(&wake_q);
 }
 EXPORT_SYMBOL(up);
 
@@ -269,11 +273,12 @@ static noinline int __sched __down_timeout(struct semaphore *sem, long timeout)
 	return __down_common(sem, TASK_UNINTERRUPTIBLE, timeout);
 }
 
-static noinline void __sched __up(struct semaphore *sem)
+static noinline void __sched __up(struct semaphore *sem,
+				  struct wake_q_head *wake_q)
 {
 	struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
 						struct semaphore_waiter, list);
 	list_del(&waiter->list);
 	waiter->up = true;
-	wake_up_process(waiter->task);
+	wake_q_add(wake_q, waiter->task);
 }
diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 3498fb344dc9..16eab9138b2b 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -30,28 +30,20 @@
 unsafe impl Sync for LockClassKey {}
 
 impl LockClassKey {
-    /// Creates a new lock class key.
-    pub const fn new() -> Self {
-        Self(Opaque::uninit())
-    }
-
     pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
         self.0.get()
     }
 }
 
-impl Default for LockClassKey {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 /// Defines a new static lock class and returns a pointer to it.
 #[doc(hidden)]
 #[macro_export]
 macro_rules! static_lock_class {
     () => {{
-        static CLASS: $crate::sync::LockClassKey = $crate::sync::LockClassKey::new();
+        static CLASS: $crate::sync::LockClassKey =
+            // SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated
+            // lock_class_key
+            unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
         &CLASS
     }};
 }