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



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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