Asynchronous Control for UNIX READ and WRITE System Commands
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
The UNIX* READ and WRITE System Commands are synchronous operations which as a rule do not return to the user until the command is completed. By adding asynchronous control, in accordance with the following described method, the user may do other processing while waiting for the read or write operation to complete. A system daemon must be started and open the device issuing an Input-Output Control (IOCTL) system call. This call will retain control within the kernel which sleeps for a wakeup from the interrupt handler. Since the communications between UNIX and the Virtual Resource Manager (VRM) is a queued system, the READ and WRITE commands are queued to the VRM and control is returned to UNIX. (The Process ID (PID) of the user issuing the call will need to be contained in the COMMAND Control Block (CCB) going to VRM.