linux-kernel - Re: [v2 PATCH] padata: Replace delayed timer with immediate workqueue in padata

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Date:   Fri, 19 Jul 2019 10:37:21 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-arch@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mathias Krause <minipli@...glemail.com>
Subject: Re: [v2 PATCH] padata: Replace delayed timer with immediate
 workqueue in padata_reorder

On Thu, Jul 18, 2019 at 11:01:46PM +0800, Herbert Xu wrote:
> @@ -376,9 +325,8 @@ void padata_do_serial(struct padata_priv *padata)
>  
>  	cpu = get_cpu();
>  
> -	/* We need to run on the same CPU padata_do_parallel(.., padata, ..)
> -	 * was called on -- or, at least, enqueue the padata object into the
> -	 * correct per-cpu queue.
> +	/* We need to enqueue the padata object into the correct
> +	 * per-cpu queue.
>  	 */
>  	if (cpu != padata->cpu) {
>  		reorder_via_wq = 1;
> @@ -388,12 +336,12 @@ void padata_do_serial(struct padata_priv *padata)
>  	pqueue = per_cpu_ptr(pd->pqueue, cpu);
>  
>  	spin_lock(&pqueue->reorder.lock);
> -	atomic_inc(&pd->reorder_objects);
>  	list_add_tail(&padata->list, &pqueue->reorder.list);
> +	atomic_inc(&pd->reorder_objects);
>  	spin_unlock(&pqueue->reorder.lock);
>  
>  	/*
> -	 * Ensure the atomic_inc of reorder_objects above is ordered correctly
> +	 * Ensure the addition to the reorder list is ordered correctly
>  	 * with the trylock of pd->lock in padata_reorder.  Pairs with smp_mb
>  	 * in padata_reorder.
>  	 */
> @@ -401,13 +349,7 @@ void padata_do_serial(struct padata_priv *padata)
>  
>  	put_cpu();
>  
> -	/* If we're running on the wrong CPU, call padata_reorder() via a
> -	 * kernel worker.
> -	 */
> -	if (reorder_via_wq)
> -		queue_work_on(cpu, pd->pinst->wq, &pqueue->reorder_work);
> -	else
> -		padata_reorder(pd);
> +	padata_reorder(pd);
>  }
>  EXPORT_SYMBOL(padata_do_serial);

If I'm not missing anything, still looks like get_cpu() and reorder_via_wq no
longer have an effect with this patch and can be removed.