linux-kernel - Re: [PATCH 1/9] percpu_ref: relocate percpu_ref

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Date:	Tue, 23 Sep 2014 14:01:26 -0700
From:	Kent Overstreet <kmo@...erainc.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, axboe@...nel.dk, hch@...radead.org,
	hannes@...xchg.org
Subject: Re: [PATCH 1/9] percpu_ref: relocate percpu_ref_reinit()

On Tue, Sep 23, 2014 at 01:55:10AM -0400, Tejun Heo wrote:
> percpu_ref is gonna go through restructuring.  Move
> percpu_ref_reinit() after percpu_ref_kill_and_confirm().  This will
> make later changes easier to follow and result in cleaner
> organization.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Kent Overstreet <kmo@...erainc.com>

Reviewed-by: Kent Overstreet <kmo@...erainc.com>

> ---
>  include/linux/percpu-refcount.h |  2 +-
>  lib/percpu-refcount.c           | 70 ++++++++++++++++++++---------------------
>  2 files changed, 36 insertions(+), 36 deletions(-)
> 
> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
> index 5df6784..f015f13 100644
> --- a/include/linux/percpu-refcount.h
> +++ b/include/linux/percpu-refcount.h
> @@ -68,10 +68,10 @@ struct percpu_ref {
>  
>  int __must_check percpu_ref_init(struct percpu_ref *ref,
>  				 percpu_ref_func_t *release, gfp_t gfp);
> -void percpu_ref_reinit(struct percpu_ref *ref);
>  void percpu_ref_exit(struct percpu_ref *ref);
>  void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
>  				 percpu_ref_func_t *confirm_kill);
> +void percpu_ref_reinit(struct percpu_ref *ref);
>  
>  /**
>   * percpu_ref_kill - drop the initial ref
> diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
> index 559ee0b..070dab5 100644
> --- a/lib/percpu-refcount.c
> +++ b/lib/percpu-refcount.c
> @@ -63,41 +63,6 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release,
>  EXPORT_SYMBOL_GPL(percpu_ref_init);
>  
>  /**
> - * percpu_ref_reinit - re-initialize a percpu refcount
> - * @ref: perpcu_ref to re-initialize
> - *
> - * Re-initialize @ref so that it's in the same state as when it finished
> - * percpu_ref_init().  @ref must have been initialized successfully, killed
> - * and reached 0 but not exited.
> - *
> - * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while
> - * this function is in progress.
> - */
> -void percpu_ref_reinit(struct percpu_ref *ref)
> -{
> -	unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> -	int cpu;
> -
> -	BUG_ON(!pcpu_count);
> -	WARN_ON(!percpu_ref_is_zero(ref));
> -
> -	atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);
> -
> -	/*
> -	 * Restore per-cpu operation.  smp_store_release() is paired with
> -	 * smp_read_barrier_depends() in __pcpu_ref_alive() and guarantees
> -	 * that the zeroing is visible to all percpu accesses which can see
> -	 * the following PCPU_REF_DEAD clearing.
> -	 */
> -	for_each_possible_cpu(cpu)
> -		*per_cpu_ptr(pcpu_count, cpu) = 0;
> -
> -	smp_store_release(&ref->pcpu_count_ptr,
> -			  ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
> -}
> -EXPORT_SYMBOL_GPL(percpu_ref_reinit);
> -
> -/**
>   * percpu_ref_exit - undo percpu_ref_init()
>   * @ref: percpu_ref to exit
>   *
> @@ -189,3 +154,38 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
>  	call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
>  }
>  EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
> +
> +/**
> + * percpu_ref_reinit - re-initialize a percpu refcount
> + * @ref: perpcu_ref to re-initialize
> + *
> + * Re-initialize @ref so that it's in the same state as when it finished
> + * percpu_ref_init().  @ref must have been initialized successfully, killed
> + * and reached 0 but not exited.
> + *
> + * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while
> + * this function is in progress.
> + */
> +void percpu_ref_reinit(struct percpu_ref *ref)
> +{
> +	unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> +	int cpu;
> +
> +	BUG_ON(!pcpu_count);
> +	WARN_ON(!percpu_ref_is_zero(ref));
> +
> +	atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);
> +
> +	/*
> +	 * Restore per-cpu operation.  smp_store_release() is paired with
> +	 * smp_read_barrier_depends() in __pcpu_ref_alive() and guarantees
> +	 * that the zeroing is visible to all percpu accesses which can see
> +	 * the following PCPU_REF_DEAD clearing.
> +	 */
> +	for_each_possible_cpu(cpu)
> +		*per_cpu_ptr(pcpu_count, cpu) = 0;
> +
> +	smp_store_release(&ref->pcpu_count_ptr,
> +			  ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
> +}
> +EXPORT_SYMBOL_GPL(percpu_ref_reinit);
> -- 
> 1.9.3
> 
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