#include <linux/poll.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/smp_lock.h>
 #include <asm/sn/io.h>
 #include <asm/sn/sn_sal.h>
 #include <asm/sn/module.h>
        file->private_data = sd;
 
        /* hook this subchannel up to the system controller interrupt */
+       lock_kernel();
        rv = request_irq(SGI_UART_VECTOR, scdrv_interrupt,
                         IRQF_SHARED | IRQF_DISABLED,
                         SYSCTL_BASENAME, sd);
                ia64_sn_irtr_close(sd->sd_nasid, sd->sd_subch);
                kfree(sd);
                printk("%s: irq request failed (%d)\n", __func__, rv);
+               unlock_kernel();
                return -EBUSY;
        }
-
+       unlock_kernel();
        return 0;
 }