SVR5 and SCO OpenServer 5

putbq(D3str)

putbq -- place a message at the head of a queue

Synopsis

   #include <sys/stream.h>
   #include <sys/ddi.h>
   
   int putbq(queue_t *q, mblk_t *bp);

Description

putbq puts a message back at the head of a queue. If messages of a higher priority are on the queue, then bp is placed at the head of its corresponding priority band. See srv(D2str) for more information about message priorities.

All flow control parameters are updated. The queue's service routine is scheduled if it has not been disabled by a previous call to noenable(D3str).

Arguments

q: Pointer to the queue.
bp: Pointer to the message.

Return values

putbq returns 1 on success and 0 on failure.

Usage

putbq is usually called when bcanput(D3str) or canput(D3str) or, for DDI multithreaded drivers, bcanputnext(D3str) or canputnext(D3str) determines that the message cannot be passed on to the next stream component.

putbq can fail if there is not enough memory to allocate the accounting data structures used with messages whose priority bands are greater than zero.

High priority messages should never be put back on a queue from within a service routine.

Context

Base or Interrupt.

Synchronization constraints

Does not block.

Driver-defined basic locks, read/write locks, and sleep locks may be held across calls to this function.

The caller cannot have the stream frozen (see freezestr(D3str)) when calling this function.

Examples

See bufcall(D3str) for an example of putbq.

Hardware applicability

All

Version applicability

ddi: 1, 2, 3, 4, 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp
oddi: 1, 2, 2mp, 3, 3mp, 4, 4mp, 5, 5mp, 6, 6mp

References

bcanput(D3str), bcanputnext(D3str), canput(D3str), canputnext(D3str), getq(D3str), insq(D3str), msgb(D4str), putq(D3str), queue(D4str), rmvq(D3str), srv(D2str)