netdev - Re: [PATCH net v2 1/3] s390/ism: Fix locking for forwarding of IRQs and events to clients

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Date: Fri, 07 Jul 2023 16:08:58 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Alexandra Winter <wintera@...ux.ibm.com>, Paolo Abeni
 <pabeni@...hat.com>,
        Wenjia Zhang <wenjia@...ux.ibm.com>, Jan Karcher
 <jaka@...ux.ibm.com>,
        Stefan Raspl <raspl@...ux.ibm.com>,
        "David S.
 Miller" <davem@...emloft.net>
Cc: linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2 1/3] s390/ism: Fix locking for forwarding of IRQs
 and events to clients

On Fri, 2023-07-07 at 15:37 +0200, Alexandra Winter wrote:
> 
> On 07.07.23 12:56, Niklas Schnelle wrote:
> [...]
> > Instead of expanding the use of the clients_lock further add a separate
> > array in struct ism_dev which references clients subscribed to the
> > device's events and IRQs. This array is protected by ism->lock which is
> > already taken in ism_handle_irq() and can be taken outside the IRQ
> > handler when adding/removing subscribers or the accessing
> 
> 				typo? s/the accessing/accessing the/g
> 
> > ism->sba_client_arr[]. This also means that the clients_lock is no
> > longer taken in IRQ context.
> > 
> 
> [...]
> 
> > @@ -554,6 +577,7 @@ static void ism_dev_add_work_func(struct work_struct *work)
> >  						 add_work);
> >  
> >  	client->add(client->tgt_ism);
> > +	ism_setup_forwarding(client, client->tgt_ism);
> >  	atomic_dec(&client->tgt_ism->add_dev_cnt);
> >  	wake_up(&client->tgt_ism->waitq);
> >  }
> > @@ -691,7 +715,11 @@ static void ism_dev_remove_work_func(struct work_struct *work)
> >  {
> >  	struct ism_client *client = container_of(work, struct ism_client,
> >  						 remove_work);
> > +	unsigned long flags;
> >  
> > +	spin_lock_irqsave(&client->tgt_ism->lock, flags);
> > +	client->tgt_ism->subs[client->id] = NULL;
> > +	spin_unlock_irqrestore(&client->tgt_ism->lock, flags);
> >  	client->remove(client->tgt_ism);
> >  	atomic_dec(&client->tgt_ism->free_clients_cnt);
> >  	wake_up(&client->tgt_ism->waitq);
> 
> I am not sure I like the new split. here you fix ism_dev_add_work_func() and ism_dev_remove_work_func(),
> that you remove in the next patch. But looks functionally ok to me.
> 
> 
> Reviewed-by: Alexandra Winter <wintera@...ux.ibm.com>

Thanks for your review. Yeah it's the price we pay for working
intermediate states. I think if you hadn't already invested the time to
look at the conmbined patch it might still be easier to review the
split patches.