contextual attributes

contextual attributes

[Yoann Padioleau]

Hi, 

Is it possible by using the __attribute((context(x,y)) sparse
attribute to enforce statically that all the callers of 
certain functions do certain actions such as disabling interrupts ?

I would like an attribute like __assume_disabled_interrupt and 
have such programs:


int __assume_disabled_interrupt    
startpoint() 
{
	return 1;
}


int f1ok()
{
	spin_lock_irq();
	startpoint();
	spin_unlock_irq();
}


int f1bad()
{
	startpoint();
}

Re: contextual attributes

[Johannes Berg]

On Mon, 2008-11-17 at 15:47 -0600, Yoann Padioleau wrote:

> Is it possible by using the __attribute((context(x,y)) sparse
> attribute to enforce statically that all the callers of 
> certain functions do certain actions such as disabling interrupts ?

In theory yes, but only half my patches got merged so no. If you search
the list you'll find a set of patches from myself that allow you to do
this, see below.

I have asked that those patches that got merged are reverted for the
time being until we can work on a decent implementation, but that hasn't
happen either so the current sparse git tree is fairly broken wrt.
context attributes...

> int __assume_disabled_interrupt    
> startpoint() 
> {
> 	return 1;
> }
> 
> 
> int f1ok()
> {
> 	spin_lock_irq();
> 	startpoint();
> 	spin_unlock_irq();
> }
> 
> 
> int f1bad()
> {
> 	startpoint();
> }

You'd have to annotate startpoint() with
__attribute__((context(irqsoff,1,1)))

and spin_lock_irq() with __attribute__((context(irqsoff,0,1))) and 1,0
for unlock, in addition to the regular locks.

[or something like that, the syntax isn't firm in my mind right now]

johannes