QWRITER(9F)QWRITER(9F)NAMEqwriter - asynchronous STREAMS perimeter upgrade
SYNOPSIS
#include <sys/stream.h>
#include <sys/ddi.h>
void qwriter(queue_t *qp, mblk_t *mp, void (*func)(), int perimeter);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI).
PARAMETERS
qp
Pointer to the queue.
mp
Pointer to a message that will be passed in to the call‐
back function.
func
A function that will be called when exclusive (writer)
access has been acquired at the specified perimeter.
perimeter
Either PERIM_INNER or PERIM_OUTER.
DESCRIPTIONqwriter() is used to upgrade the access at either the inner or the
outer perimeter from shared to exclusive and call the specified call‐
back function when the upgrade has succeeded. See mt-streams(9F). The
callback function is called as:
(*func)(queue_t *qp, mblk_t *mp);
qwriter() will acquire exclusive access immediately if possible, in
which case the specified callback function will be executed before
qwriter() returns. If this is not possible, qwriter() will defer the
upgrade until later and return before the callback function has been
executed. Modules should not assume that the callback function has been
executed when qwriter() returns. One way to avoid dependencies on the
execution of the callback function is to immediately return after call‐
ing qwriter() and let the callback function finish the processing of
the message.
When qwriter() defers calling the callback function, the STREAMS frame‐
work will prevent other messages from entering the inner perimeter
associated with the queue until the upgrade has completed and the call‐
back function has finished executing.
CONTEXTqwriter() can only be called from an put(9E) or srv(9E) routine, or
from a qwriter(), qtimeout(9F), or qbufcall(9F) callback function.
SEE ALSOput(9E), srv(9E), mt-streams(9F), qbufcall(9F), qtimeout(9F)
STREAMS Programming Guide
Writing Device Drivers
Mar 1, 1993 QWRITER(9F)
