Re: [patch 3/5] [PREEMPT_RT] Changing interrupt handlers from running in thread to hardirq and back runtime.

[Esben Nielsen <nielsen.esben@googlemail.com>]

On Sat, 3 Jun 2006, Steven Rostedt wrote:

> On Fri, 2006-06-02 at 23:23 +0100, Esben Nielsen wrote:
> > Makes it possible for the e100 ethernet driver to have it's interrupt handler
> > in both hard-irq and threaded context under PREEMPT_RT.
> >
> > Index: linux-2.6.16-rt23.spin_mutex/drivers/net/e100.c
> > ===================================================================
> > --- linux-2.6.16-rt23.spin_mutex.orig/drivers/net/e100.c
> > +++ linux-2.6.16-rt23.spin_mutex/drivers/net/e100.c
> > @@ -530,7 +530,7 @@ struct nic {
> >   	enum ru_state ru_running;
> >
> >   	spinlock_t cb_lock			____cacheline_aligned;
> > -	spinlock_t cmd_lock;
> > +	spin_mutex_t cmd_lock;
> >   	struct csr __iomem *csr;
> >   	enum scb_cmd_lo cuc_cmd;
> >   	unsigned int cbs_avail;
> > @@ -1950,6 +1950,30 @@ static int e100_rx_alloc_list(struct nic
> >   	return 0;
> >   }
> >
> > +static int e100_change_context(int irq, void *dev_id,
> > +			       enum change_context_cmd cmd)
> > +{
> > +	struct net_device *netdev = dev_id;
> > +	struct nic *nic = netdev_priv(netdev);
> > +
> > +	switch(cmd)
> > +	{
> > +	case IRQ_TO_HARDIRQ:
> > +		if(!spin_mutexes_can_spin())
> > +			return -ENOSYS;
> > +
> > +		spin_mutex_to_spin(&nic->cmd_lock);
> > +		break;
> > +	case IRQ_CAN_THREAD:
> > +		/* Ok - return 0 */
> > +		break;
>
> Why even bother with the IRQ_CAN_THREAD.  If this would be anything
> other than OK, then we shouldn't be using that request_irq2 (yuck!) call
> in the first place.
Just for the sake of generality. Nothing else. It would be very unlikely, 
as you say, that it wouldn't return 0.

> -- Steve

Esben

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