fixed race between conversions and fifo overflow check

diff --git a/comedi/drivers/das800.c b/comedi/drivers/das800.c
index 424122c2253d5367cf21cb44b5d35397148e8c26..f8b075a9447fbb79f4b19e82cae05f9be65ff4cb 100644 (file)
--- a/comedi/drivers/das800.c
+++ b/comedi/drivers/das800.c
@@ -345,12 +345,13 @@ static void das800_interrupt(int irq, void *d, struct pt_regs *regs)
                return;
        }
 
-  /* read 16 bits from dev->iobase and dev->iobase + 1 */
-       dataPoint = inb(dev->iobase + DAS800_LSB);
-       dataPoint += inb(dev->iobase + DAS800_MSB) << 8;
        /* loop while card's fifo is not empty (and make sure loop terminates by limiting to 256 iterations) */
-       for(i = 0; (dataPoint & FIFO_EMPTY) == 0 && i < max_loops; i++)
+       for(i = 0; i < max_loops; i++)
        {
+               /* read 16 bits from dev->iobase and dev->iobase + 1 */
+               dataPoint = inb(dev->iobase + DAS800_LSB);
+               dataPoint += inb(dev->iobase + DAS800_MSB) << 8;
+               if(dataPoint & FIFO_EMPTY) break;
                if( dataPoint & FIFO_OVF )
                {
                        comedi_spin_unlock_irqrestore(&dev->spinlock, irq_flags);
@@ -380,23 +381,12 @@ static void das800_interrupt(int irq, void *d, struct pt_regs *regs)
                        async->buf_int_ptr += sizeof(sampl_t);
                        if(devpriv->count > 0) devpriv->count--;
                }
-               /* read 16 bits from dev->iobase and dev->iobase + 1 */
-               dataPoint = inb(dev->iobase + DAS800_LSB);
-               dataPoint += inb(dev->iobase + DAS800_MSB) << 8;
        }
        /* we can release spinlock now since we dont case if hardware conversions are enabled anymore */
        comedi_spin_unlock_irqrestore(&dev->spinlock, irq_flags);
        if(i == max_loops)
                comedi_error(dev, "possible problem with loop in interrupt handler");
 
-       /* check for overflow on last data point */
-       if( dataPoint & FIFO_OVF )
-       {
-               comedi_error(dev, "DAS800 FIFO overflow");
-               das800_cancel(dev, dev->subdevices + 0);
-               comedi_error_done(dev, s);
-               return;
-       }
        comedi_bufcheck(dev,s);
        if(devpriv->count > 0 || devpriv->forever == 1)
        {
@@ -408,6 +398,17 @@ static void das800_interrupt(int irq, void *d, struct pt_regs *regs)
        /* otherwise, stop taking data */
        } else
        {
+               /* read 16 bits from dev->iobase and dev->iobase + 1 */
+               dataPoint = inb(dev->iobase + DAS800_LSB);
+               dataPoint += inb(dev->iobase + DAS800_MSB) << 8;
+               /* check for overflow on last data point */
+               if( dataPoint & FIFO_OVF )
+               {
+                       comedi_error(dev, "DAS800 FIFO overflow");
+                       das800_cancel(dev, dev->subdevices + 0);
+                       comedi_error_done(dev, s);
+                       return;
+               }
                disable_das800(dev);            /* diable hardware triggered conversions */
                comedi_done(dev, s);
        }