illumos: manual page: getq.9f

GETQ(9F) Kernel Functions for Drivers GETQ(9F)

NAME

getq - get the next message from a queue

SYNOPSIS

#include <sys/stream.h>

mblk_t *getq(queue_t *q);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

PARAMETERS

q
Pointer to the queue from which the message is to be retrieved.

DESCRIPTION

The getq() function is used by a service ( srv(9E)) routine to retrieve
its enqueued messages.

A module or driver may include a service routine to process enqueued
messages. Once the STREAMS scheduler calls srv() it must process all
enqueued messages, unless prevented by flow control. getq() obtains the
next available message from the top of the queue pointed to by q. It
should be called in a while loop that is exited only when there are no
more messages or flow control prevents further processing.

If an attempt was made to write to the queue while it was blocked by flow
control, getq() back-enables (restarts) the service routine once it falls
below the low water mark.

RETURN VALUES

If there is a message to retrieve, getq() returns a pointer to it. If no
message is queued, getq() returns a NULL pointer.

CONTEXT

The getq() function can be called from user, interrupt, or kernel
context.

EXAMPLES

See dupb(9F).