STREAMS/UX for the HP 9000 Reference Manual

Differences Between STREAMS/UX and System V Release 4 STREAMS

HP-UX Modiﬁcations to STREAMS/UX Utilities

instead of acquiring a spinlock. Whether the caller will block or spin if the

lock cannot be obtained is implementation deﬁned. The HP-UX

implementation spins.

LOCK_ALLOC

The STREAMS/UX LOCK_ALLOC calls the native HP-UX alloc_spinlock

primitive. There are some small differences between the STREAMS/UX

LOCK_ALLOC and the SVR4 MP utility. LOCK_ALLOC has a ﬂag

parameter which indicates if the caller is willing to block while waiting for

memory to be allocated. HP-UX only allows this ﬂag to be set to

KM_SLEEP, and returns zero if it is set to KM_NOSLEEP. The

STREAMS/UX LOCK_ALLOC accepts the following hierarchy parameter

values which are reserved for STREAMS/UX modules and drivers in

/usr/include/sys/semglobal.h and /usr/conf/h/semglobal.h:

STREAMS_USR1_LOCK_ORDER, STREAMS_USR2_LOCK_ORDER,

and STREAMS_USR3_LOCK_ORDER. The compiler options to turn on

deadlock checking for HP-UX are different than those documented in the

SVR4.2 Driver manual. The entire HP-UX kernel and the module or driver

must be compiled with SEMAPHORE_DEBUG to enable deadlock

checking. According to the SVR4.2 Driver manual, the min_pl parameter

can be ignored by implementations which do not need to raise the priority

level. The HP-UX STREAMS LOCK_ALLOC ignores it.

putctl2

STREAMS/UX also provides the additional utility called putctl2. This

utility can be used to send a control message with a two-byte parameter to a

queue. For example, putctl2 can send the new style of an M_ERROR

message, which is two bytes long, to a queue.

int putctl2(q, type, p1, p2);

queue_t * q;

int type;

int p1;

int p2;

The q parameter is the queue to which the message is sent. The type

parameter is the message type. The p1 and p2 parameters are the two bytes

of data in the message. The putctl2 utility ensures that the type is not a data

type. The utility also allocates a message block, ﬁlls in the data, and calls