Re: [PATCH] irda: Fix RCU lock pairing on error path

[Samuel Ortiz]

Hi Paul, hi Josh,

Paul E. McKenney wrote :
> On Wed, Jun 28, 2006 at 05:56:41PM -0700, Josh Triplett wrote:
>> irlan_client_discovery_indication calls rcu_read_lock and
>> rcu_read_unlock, but
>> returns without unlocking in an error case.  Fix that by replacing the
>> return
>> with a goto so that the rcu_read_unlock always gets executed.
>
> Good catch!!!  Looks good from an RCU viewpoint, in fact, looks absolutely
> necessary to permit IRDA to work in debug mode, particularly in either
> a CONFIG_PREEMPT or a -rt kernel.
Indeed, nice catch.

> One question below, but up to the maintainer.  ;-)
Yes, definitely, IRDA_ASSERT_LABEL(out:) makes sense.
I will forward the patch to davem's netdev tree, thanks.

Cheers,
Samuel.


> 							Thanx, Paul
>
> Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>> Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxx>
>>
>> ---
>>
>>  net/irda/irlan/irlan_client.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> e20ab96944814489277c3bfd4e69133854ab01e9
>> diff --git a/net/irda/irlan/irlan_client.c
>> b/net/irda/irlan/irlan_client.c
>> index f8e6cb0..5ce7d2e 100644
>> --- a/net/irda/irlan/irlan_client.c
>> +++ b/net/irda/irlan/irlan_client.c
>> @@ -173,13 +173,14 @@ void irlan_client_discovery_indication(d
>>  	rcu_read_lock();
>>  	self = irlan_get_any();
>>  	if (self) {
>> -		IRDA_ASSERT(self->magic == IRLAN_MAGIC, return;);
>> +		IRDA_ASSERT(self->magic == IRLAN_MAGIC, goto out;);
>>
>>  		IRDA_DEBUG(1, "%s(), Found instance (%08x)!\n", __FUNCTION__ ,
>>  		      daddr);
>>
>>  		irlan_client_wakeup(self, saddr, daddr);
>>  	}
>> +out:
>
> Should the above label instead be as follows?
>
> 	IRDA_ASSERT_LABEL(out:)
>
> Just in case some variant of gcc, sparse, or whatever complains about
> labels that don't have a corresponding goto (in CONFIG_IRDA_DEBUG=n
> builds).
>
>>  	rcu_read_unlock();
>>  }
>>
>>
>>
>

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