STREAMS/UX for the HP 9000 Reference Manual

STREAMS/UX Multiprocessor Support

Running Modules and Drivers in Uniprocessor Emulation Mode

emulation driver, the I/O system acquires the spl lock. Then if the interrupt

handler calls put, putnext, or streams_put, STREAMS/UX usually executes

the put routine on the ICS with the spl lock. Note that the STREAMS/UX

utilities do not acquire the spl lock. An MP scalable interrupt handler may

not be able to safely call put, putnext, or streams_put to enter a UP

emulation stream.

STREAMS/UX protects the various callback functions in different ways.

STREAMS/UX does not have to acquire the I/O semaphore or spl lock to

run esballoc free routines in UP emulation mode. The free routine will

automatically run in the same mode as the module which calls freeb. Also,

the HP-UX I/O system protects timeout callback routines by obtaining the

spl lock before running the routine.

Bufcall and weld callback functions are always run under UP emulation.

The STREAMS/UX memory and weld daemons always obtain the I/O

semaphore before running UP emulation or MP scalable callback routines.

This should not hurt the performance of MP scalable modules because weldq

and bufcall are not called very often.

Configuring Modules and Drivers for UP Emulation

Modules and drivers run in UP emulation mode by default. To conﬁgure a

module or driver to run in UP emulation mode, do not specify any MP ﬂags.

The examples below show how to conﬁgure UP emulation modules and

drivers by creating a master ﬁle $DEVICE table entry or a module or driver

install function. See Chapter 5 for more information about conﬁguring

modules and drivers.