On Tue, 1 Mar 2011, Pratheesh Gangadhar wrote:

+
+static spinlock_t lock;

static DEFINE_SPINLOCK(lock);

+static struct clk *pruss_clk;
+static struct uio_info *info;
+static dma_addr_t sram_paddr, ddr_paddr;
+static void *prussio_vaddr, *sram_vaddr, *ddr_vaddr;
+
+static irqreturn_t pruss_handler(int irq, struct uio_info *dev_info)
+{
+	unsigned long flags;
+	int val, intr_mask = (1 << (irq - 1));
+	void __iomem *base = dev_info->mem[0].internal_addr;
+	void __iomem *intren_reg = base + PINTC_HIER;
+	void __iomem *intrstat_reg = base + PINTC_HIPIR + ((irq - 1) << 2);
+
+	spin_lock_irqsave(&lock, flags);

spin_lock() is enough as we run handlers with interrupts disabled.

+	val = ioread32(intren_reg);
+	/* Is interrupt enabled and active ? */
+	if (!(val & intr_mask) && (ioread32(intrstat_reg) & HIPIR_NOPEND)) {
+		spin_unlock_irqrestore(&lock, flags);
+		return IRQ_NONE;
+	}
+
+	/* Disable interrupt */
+	iowrite32((val & ~intr_mask), intren_reg);
+	spin_unlock_irqrestore(&lock, flags);
+	return IRQ_HANDLED;
+}

So now you still have not solved the problem of user space enabling an
interrupt again. That's racy as well and you can solve it by providing
an uio->irq_control function which handles the interrupt enable
register under the lock as well.

Thanks,

	tglx