Tribblix: manual page: putbq.9f

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

NAME

putbq - place a message at the head of a queue

SYNOPSIS

#include <sys/stream.h>

int putbq(queue_t *q, mblk_t *bp);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

PARAMETERS

q
Pointer to the queue.

bp
Pointer to the message block.

DESCRIPTION

The putbq() function places a message at the beginning of the
appropriate section of the message queue. There are always sections
for high priority and ordinary messages. If other priority bands are
used, each will have its own section of the queue, in priority band
order, after high priority messages and before ordinary messages.
putbq() can be used for ordinary, priority band, and high priority
messages. However, unless precautions are taken, using putbq() with a
high priority message is likely to lead to an infinite loop of
putting the message back on the queue, being rescheduled, pulling it
off, and putting it back on.

This function is usually called when bcanput(9F) or canput(9F)
determines that the message cannot be passed on to the next stream
component. The flow control parameters are updated to reflect the
change in the queue's status. If QNOENB is not set, the service
routine is enabled.

RETURN VALUES

The putbq() function returns 1 upon success and 0 upon failure.

Upon failure, the caller should call freemsg(9F) to free the pointer
to the message block.

CONTEXT

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

EXAMPLES

See the bufcall(9F) function page for an example of putbq().