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Message-ID: <9933aa75-9c7f-4ae3-b580-5c68a63615ba@redhat.com>
Date: Sat, 28 Jun 2025 15:06:03 -0400
From: Waiman Long <llong@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev
Cc: tglx@...utronix.de, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
 Boqun Feng <boqun.feng@...il.com>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [PATCH v2 1/1] local_lock: Move this_cpu_ptr() notation from
 internal to main header.

On 6/10/25 7:02 AM, Sebastian Andrzej Siewior wrote:
> The local_lock.h is the main entry for the local_lock_t type and
> provides wrappers around internal functions prefixed with __ in
> local_lock_internal.h.
>
> Move the this_cpu_ptr() dereference of the variable from the internal to
> the main header. Since it is all macro implemented, this_cpu_ptr() will
> still happen within the preempt/ IRQ disabled section.
> This will free the internal implementation (__) to be used on
> local_lock_t types which are local variables and must not be accessed
> via this_cpu_ptr().
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>   include/linux/local_lock.h          | 20 +++++++++----------
>   include/linux/local_lock_internal.h | 30 ++++++++++++++---------------
>   2 files changed, 25 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/local_lock.h b/include/linux/local_lock.h
> index 16a2ee4f8310b..2ba8464195244 100644
> --- a/include/linux/local_lock.h
> +++ b/include/linux/local_lock.h
> @@ -13,13 +13,13 @@
>    * local_lock - Acquire a per CPU local lock
>    * @lock:	The lock variable
>    */
> -#define local_lock(lock)		__local_lock(lock)
> +#define local_lock(lock)		__local_lock(this_cpu_ptr(lock))
>   
>   /**
>    * local_lock_irq - Acquire a per CPU local lock and disable interrupts
>    * @lock:	The lock variable
>    */
> -#define local_lock_irq(lock)		__local_lock_irq(lock)
> +#define local_lock_irq(lock)		__local_lock_irq(this_cpu_ptr(lock))
>   
>   /**
>    * local_lock_irqsave - Acquire a per CPU local lock, save and disable
> @@ -28,19 +28,19 @@
>    * @flags:	Storage for interrupt flags
>    */
>   #define local_lock_irqsave(lock, flags)				\
> -	__local_lock_irqsave(lock, flags)
> +	__local_lock_irqsave(this_cpu_ptr(lock), flags)
>   
>   /**
>    * local_unlock - Release a per CPU local lock
>    * @lock:	The lock variable
>    */
> -#define local_unlock(lock)		__local_unlock(lock)
> +#define local_unlock(lock)		__local_unlock(this_cpu_ptr(lock))
>   
>   /**
>    * local_unlock_irq - Release a per CPU local lock and enable interrupts
>    * @lock:	The lock variable
>    */
> -#define local_unlock_irq(lock)		__local_unlock_irq(lock)
> +#define local_unlock_irq(lock)		__local_unlock_irq(this_cpu_ptr(lock))
>   
>   /**
>    * local_unlock_irqrestore - Release a per CPU local lock and restore
> @@ -49,7 +49,7 @@
>    * @flags:      Interrupt flags to restore
>    */
>   #define local_unlock_irqrestore(lock, flags)			\
> -	__local_unlock_irqrestore(lock, flags)
> +	__local_unlock_irqrestore(this_cpu_ptr(lock), flags)
>   
>   /**
>    * local_lock_init - Runtime initialize a lock instance
> @@ -64,7 +64,7 @@
>    * locking constrains it will _always_ fail to acquire the lock in NMI or
>    * HARDIRQ context on PREEMPT_RT.
>    */
> -#define local_trylock(lock)		__local_trylock(lock)
> +#define local_trylock(lock)		__local_trylock(this_cpu_ptr(lock))
>   
>   /**
>    * local_trylock_irqsave - Try to acquire a per CPU local lock, save and disable
> @@ -77,7 +77,7 @@
>    * HARDIRQ context on PREEMPT_RT.
>    */
>   #define local_trylock_irqsave(lock, flags)			\
> -	__local_trylock_irqsave(lock, flags)
> +	__local_trylock_irqsave(this_cpu_ptr(lock), flags)
>   
>   DEFINE_GUARD(local_lock, local_lock_t __percpu*,
>   	     local_lock(_T),
> @@ -91,10 +91,10 @@ DEFINE_LOCK_GUARD_1(local_lock_irqsave, local_lock_t __percpu,
>   		    unsigned long flags)
>   
>   #define local_lock_nested_bh(_lock)				\
> -	__local_lock_nested_bh(_lock)
> +	__local_lock_nested_bh(this_cpu_ptr(_lock))
>   
>   #define local_unlock_nested_bh(_lock)				\
> -	__local_unlock_nested_bh(_lock)
> +	__local_unlock_nested_bh(this_cpu_ptr(_lock))
>   
>   DEFINE_GUARD(local_lock_nested_bh, local_lock_t __percpu*,
>   	     local_lock_nested_bh(_T),
> diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h
> index 8d5ac16a9b179..b4d7b24882835 100644
> --- a/include/linux/local_lock_internal.h
> +++ b/include/linux/local_lock_internal.h
> @@ -99,14 +99,14 @@ do {								\
>   		local_trylock_t *tl;					\
>   		local_lock_t *l;					\
>   									\
> -		l = (local_lock_t *)this_cpu_ptr(lock);			\
> +		l = (local_lock_t *)(lock);			\
>   		tl = (local_trylock_t *)l;				\
>   		_Generic((lock),					\
> -			__percpu local_trylock_t *: ({			\
> +			local_trylock_t *: ({			\
>   				lockdep_assert(tl->acquired == 0);	\
>   				WRITE_ONCE(tl->acquired, 1);		\
>   			}),						\
> -			__percpu local_lock_t *: (void)0);		\
> +			local_lock_t *: (void)0);		\
>   		local_lock_acquire(l);					\
>   	} while (0)
>   
> @@ -133,7 +133,7 @@ do {								\
>   		local_trylock_t *tl;				\
>   								\
>   		preempt_disable();				\
> -		tl = this_cpu_ptr(lock);			\
> +		tl = (lock);					\
>   		if (READ_ONCE(tl->acquired)) {			\
>   			preempt_enable();			\
>   			tl = NULL;				\
> @@ -150,7 +150,7 @@ do {								\
>   		local_trylock_t *tl;				\
>   								\
>   		local_irq_save(flags);				\
> -		tl = this_cpu_ptr(lock);			\
> +		tl = (lock);					\
>   		if (READ_ONCE(tl->acquired)) {			\
>   			local_irq_restore(flags);		\
>   			tl = NULL;				\
> @@ -167,15 +167,15 @@ do {								\
>   		local_trylock_t *tl;					\
>   		local_lock_t *l;					\
>   									\
> -		l = (local_lock_t *)this_cpu_ptr(lock);			\
> +		l = (local_lock_t *)(lock);				\
>   		tl = (local_trylock_t *)l;				\
>   		local_lock_release(l);					\
>   		_Generic((lock),					\
> -			__percpu local_trylock_t *: ({			\
> +			local_trylock_t *: ({			\
>   				lockdep_assert(tl->acquired == 1);	\
>   				WRITE_ONCE(tl->acquired, 0);		\
>   			}),						\
> -			__percpu local_lock_t *: (void)0);		\
> +			local_lock_t *: (void)0);		\
>   	} while (0)
>   
>   #define __local_unlock(lock)					\
> @@ -199,11 +199,11 @@ do {								\
>   #define __local_lock_nested_bh(lock)				\
>   	do {							\
>   		lockdep_assert_in_softirq();			\
> -		local_lock_acquire(this_cpu_ptr(lock));	\
> +		local_lock_acquire((lock));			\
>   	} while (0)
>   
>   #define __local_unlock_nested_bh(lock)				\
> -	local_lock_release(this_cpu_ptr(lock))
> +	local_lock_release((lock))
>   
>   #else /* !CONFIG_PREEMPT_RT */
>   
> @@ -227,7 +227,7 @@ typedef spinlock_t local_trylock_t;
>   #define __local_lock(__lock)					\
>   	do {							\
>   		migrate_disable();				\
> -		spin_lock(this_cpu_ptr((__lock)));		\
> +		spin_lock((__lock));				\
>   	} while (0)
>   
>   #define __local_lock_irq(lock)			__local_lock(lock)
> @@ -241,7 +241,7 @@ typedef spinlock_t local_trylock_t;
>   
>   #define __local_unlock(__lock)					\
>   	do {							\
> -		spin_unlock(this_cpu_ptr((__lock)));		\
> +		spin_unlock((__lock));				\
>   		migrate_enable();				\
>   	} while (0)
>   
> @@ -252,12 +252,12 @@ typedef spinlock_t local_trylock_t;
>   #define __local_lock_nested_bh(lock)				\
>   do {								\
>   	lockdep_assert_in_softirq_func();			\
> -	spin_lock(this_cpu_ptr(lock));				\
> +	spin_lock((lock));					\
>   } while (0)
>   
>   #define __local_unlock_nested_bh(lock)				\
>   do {								\
> -	spin_unlock(this_cpu_ptr((lock)));			\
> +	spin_unlock((lock));					\
>   } while (0)
>   
>   #define __local_trylock(lock)					\
> @@ -268,7 +268,7 @@ do {								\
>   			__locked = 0;				\
>   		} else {					\
>   			migrate_disable();			\
> -			__locked = spin_trylock(this_cpu_ptr((lock)));	\
> +			__locked = spin_trylock((lock));	\
>   			if (!__locked)				\
>   				migrate_enable();		\
>   		}						\

It looks better if the trailing '\' of multi-line macros can be made 
aligned on the right side. Other than that, it looks good to me.

Acked-by: Waiman Long <longman@...hat.com>


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