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

[Steven Rostedt]

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.

-- Steve

> +	case IRQ_TO_THREADED:
> +		spin_mutex_to_mutex(&nic->cmd_lock);
> +		break;
> +	}
> +	return 0; /* Ok */
> +}
> +
>   static irqreturn_t e100_intr(int irq, void *dev_id, struct pt_regs *regs)
>   {
>   	struct net_device *netdev = dev_id;
> @@ -2064,9 +2088,12 @@ static int e100_up(struct nic *nic)
>   	e100_set_multicast_list(nic->netdev);
>   	e100_start_receiver(nic, NULL);
>   	mod_timer(&nic->watchdog, jiffies);
> -	if((err = request_irq(nic->pdev->irq, e100_intr, SA_SHIRQ,
> -		nic->netdev->name, nic->netdev)))
> +	if((err = request_irq2(nic->pdev->irq, e100_intr,
> +			       SA_SHIRQ|SA_MUST_THREAD_RT,
> +			       nic->netdev->name, nic->netdev,
> +			       e100_change_context)))
>   		goto err_no_irq;
> +
>   	netif_wake_queue(nic->netdev);
>   	netif_poll_enable(nic->netdev);
>   	/* enable ints _after_ enabling poll, preventing a race between
> 


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