Subject: Re: socreate()
To: Elad Efrat <>
From: Jason Thorpe <>
List: tech-kern
Date: 10/25/2006 14:59:50
On Oct 25, 2006, at 2:54 PM, Elad Efrat wrote:

> Jason Thorpe wrote:
>> On Oct 25, 2006, at 2:41 PM, Elad Efrat wrote:
>>> hi,
>>> can socreate() sleep? (I want to add a kauth(9) call in there to
>>> implement socket policies in one place)
>>         s = splsoftnet();
>>         so = pool_get(&socket_pool, PR_WAITOK);
>>> I *think* someone mentioned something about that in some thread in  
>>> the
>>> past; looking at the code it seems that if_gre.c:gre_kick(),  
>>> called at
>>> IPL_NET, can call socreate().
>> socreate() must never be called from interrupt context.
> okay then I perhaps don't understand the code.
> if_gre.c:gre_kick() says it "Must be called at IPL_NET" (and it is,  
> from
> gre_ioctl(), right after splnet() was called). gre_kick() in turn  
> calls
> kthread_create1() with 'func' being gre_thread(). in turn, that calls
> gre_thread1(), which can call gre_socreate1(), which can call
> socreate().

Perhaps it needs to be called at IPL_NET for other reasons, but so  
long as it is never called from INTERRUPT context, it should be fine  
(if suboptimal -- sigh, all of this spl baggage to wade through on the  
way to a real MP kernel...)

> granted, I'm not familiar with neither the gre(4) code nor kernel
> threads, but is there any guarantee that the above won't result in at
> least some cases where socreate() is called at IPL_NET?

Being called at IPL_NET via an spl call is not the same as being  
called from an IPL_NET interrupt handler.

> -e.
> -- 
> Elad Efrat

-- thorpej