linux man page for flushq

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

NAME

       flushq - remove messages from a queue

SYNOPSIS

       #include <sys/stream.h>

       void flushq(queue_t *q, int flag);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       q	Pointer to the queue to be flushed.

       flag	Valid flag values are:

       FLUSHDATA       Flush only data messages (types M_DATA M_DELAY M_PROTO and M_PCPROTO).

       FLUSHALL        Flush all messages.

DESCRIPTION

       flushq()  frees	messages  and their associated data structures by calling freemsg(9F). If the queue's count falls below the low water mark
       and the queue was blocking an upstream service procedure, the nearest upstream service procedure is enabled.

CONTEXT

       flushq() can be called from user or interrupt context.

EXAMPLES

       Example 1: Using flushq()

       This example depicts the canonical flushing code for STREAMS modules. The module has a write service procedure and potentially has messages
       on  the	queue.	If  it	receives an M_FLUSH message, and if the FLUSHR bit is on in the first byte of the message (line 10), then the read
       queue is flushed (line 11). If the FLUSHW bit is on (line 12), then the write queue is flushed (line 13). Then the message is passed  along
       to the next entity in the stream (line 14). See the example for qreply(9F) for the canonical flushing code for drivers.

	     1	/*
	     2	 * Module write-side put procedure.
	     3	 */
	     4	xxxwput(q, mp)
	     5	    queue_t *q;
	     6	    mblk_t *mp;
	     7	{
	     8	 switch(mp->b_datap->db_type) {
	     9	    case M_FLUSH:
	    10	      if (*mp->b_rptr & FLUSHR)
	    11		   flushq(RD(q), FLUSHALL);
	    12	      if (*mp->b_rptr & FLUSHW)
	    13		   flushq(q, FLUSHALL);
	    14	      putnext(q, mp);
	    15	      break;
		      . . .
	    16	 }
	    17	}

SEE ALSO

       flushband(9F), freemsg(9F), putq(9F), qreply(9F)

       Writing Device Drivers STREAMS Programming Guide

SunOS 5.10							    11 Apr 1991 							flushq(9F)