fix to prevent use of rt interrupt with shared interrupt

diff --git a/comedi/rt.c b/comedi/rt.c
index 470cbe216130f167bdf8d6b44cddf724d90a2aa0..b481a52c97c71fbc8a81237518737af21f4375c1 100644 (file)
--- a/comedi/rt.c
+++ b/comedi/rt.c
@@ -90,13 +90,25 @@ int comedi_request_irq(unsigned irq,void (*handler)(int, void *,struct pt_regs *
        it->handler=handler;
        it->irq=irq;
        it->dev_id=dev_id;
-       it->flags=flags;
        it->device=device;
 
-       ret=request_irq(irq,handler,flags,device,dev_id);
+       /* null shared interrupt flag, since rt interrupt handlers do not
+        * support it, and this version of comedi_request_irq() is only
+        * called for kernels with rt support */
+       it->flags = flags & ~SA_SHIRQ;
+
+       ret=request_irq(irq,handler,it->flags,device,dev_id);
        if(ret<0){
-               kfree(it);
-               return ret;
+               // we failed, so fall back on allowing shared interrupt
+               if(flags & SA_SHIRQ)
+               {
+                       it->flags = flags;
+                       ret=request_irq(irq,handler,it->flags,device,dev_id);
+               }
+               if(ret<0){
+                       kfree(it);
+                       return ret;
+               }
        }
 
        comedi_irqs[irq]=it;
@@ -127,9 +139,16 @@ void comedi_switch_to_rt(comedi_device *dev)
 {
        struct comedi_irq_struct *it=comedi_irqs[dev->irq];
 
+       // this prevents crashes with comedi_rt_timer
        if(it == NULL)
                return;
 
+       // rt interrupts and shared interrupts don't mix
+       if(it->flags & SA_SHIRQ){
+               rt_printk("comedi: cannot switch shared interrupt to real time priority\n");
+               return;
+       }
+
        spin_lock_irq(&dev->spinlock);
        RT_protect();
        sti();
@@ -147,9 +166,14 @@ void comedi_switch_to_non_rt(comedi_device *dev)
 {
        struct comedi_irq_struct *it=comedi_irqs[dev->irq];
 
+       // this prevents crashes with comedi_rt_timer
        if(it == NULL)
                return;
 
+       // rt interrupts and shared interrupts don't mix
+       if(it->flags & SA_SHIRQ)
+               return;
+
        RT_spin_lock_irq(&dev->spinlock);
 
        dev->rt--;