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

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Date: Mon, 10 Jul 2023 08:35:09 +0200
From: Alexandra Winter <wintera@...ux.ibm.com>
To: Simon Horman <simon.horman@...igine.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Paolo Abeni <pabeni@...hat.com>, Wenjia Zhang <wenjia@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        "David S. Miller"
 <davem@...emloft.net>,
        Stefan Raspl <raspl@...ux.ibm.com>, Jan Karcher <jaka@...ux.ibm.com>,
        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 08.07.23 15:36, Simon Horman wrote:
> On Fri, Jul 07, 2023 at 12:43:57PM +0200, Niklas Schnelle wrote:
[...]
>> @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client)
>>  		max_client--;
>>  	spin_unlock_irqrestore(&clients_lock, flags);
>>  	list_for_each_entry(ism, &ism_dev_list.list, list) {
>> +		spin_lock_irqsave(&ism->lock, flags);
> 
> Hi Niklas,
> 
> The lock is taken here.
> 
>> +		/* Stop forwarding IRQs and events */
>> +		ism->subs[client->id] = NULL;
>>  		for (int i = 0; i < ISM_NR_DMBS; ++i) {
>>  			if (ism->sba_client_arr[i] == client->id) {
>>  				pr_err("%s: attempt to unregister client '%s'"
>> @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client)
>>  				goto out;
> 
> But it does not appear to be released
> (by the call to spin_unlock_irqrestore() below)
> if goto out is called here.
> 
>>  			}
>>  		}
>> +		spin_unlock_irqrestore(&ism->lock, flags);
>>  	}
>>  out:
>>  	mutex_unlock(&ism_dev_list.mutex);
> 

Great catch, Simon.
@Niklas, the missing unlock accidentially got moved to "[PATCH net v2 3/3] s390/ism: Do not unregister clients with registered DMBs"