1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25 /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
26 /* All Rights Reserved */
27
28
29
30 /*
31 * Pseudo Terminal Slave Driver.
32 *
33 * The pseudo-tty subsystem simulates a terminal connection, where the master
34 * side represents the terminal and the slave represents the user process's
35 * special device end point. The master device is set up as a cloned device
36 * where its major device number is the major for the clone device and its minor
37 * device number is the major for the ptm driver. There are no nodes in the file
38 * system for master devices. The master pseudo driver is opened using the
39 * open(2) system call with /dev/ptmx as the device parameter. The clone open
40 * finds the next available minor device for the ptm major device.
41 *
42 * A master device is available only if it and its corresponding slave device
43 * are not already open. When the master device is opened, the corresponding
44 * slave device is automatically locked out. Only one open is allowed on a
45 * master device. Multiple opens are allowed on the slave device. After both
46 * the master and slave have been opened, the user has two file descriptors
47 * which are the end points of a full duplex connection composed of two streams
48 * which are automatically connected at the master and slave drivers. The user
49 * may then push modules onto either side of the stream pair.
50 *
51 * The master and slave drivers pass all messages to their adjacent queues.
52 * Only the M_FLUSH needs some processing. Because the read queue of one side
53 * is connected to the write queue of the other, the FLUSHR flag is changed to
54 * the FLUSHW flag and vice versa. When the master device is closed an M_HANGUP
55 * message is sent to the slave device which will render the device
56 * unusable. The process on the slave side gets the EIO when attempting to write
57 * on that stream but it will be able to read any data remaining on the stream
58 * head read queue. When all the data has been read, read() returns 0
59 * indicating that the stream can no longer be used. On the last close of the
60 * slave device, a 0-length message is sent to the master device. When the
61 * application on the master side issues a read() or getmsg() and 0 is returned,
62 * the user of the master device decides whether to issue a close() that
63 * dismantles the pseudo-terminal subsystem. If the master device is not closed,
64 * the pseudo-tty subsystem will be available to another user to open the slave
65 * device.
66 *
67 * Synchronization:
68 *
69 * All global data synchronization between ptm/pts is done via global
70 * ptms_lock mutex which is initialized at system boot time from
71 * ptms_initspace (called from space.c).
72 *
73 * Individual fields of pt_ttys structure (except ptm_rdq, pts_rdq and
74 * pt_nullmsg) are protected by pt_ttys.pt_lock mutex.
75 *
76 * PT_ENTER_READ/PT_ENTER_WRITE are reference counter based read-write locks
77 * which allow reader locks to be reacquired by the same thread (usual
78 * reader/writer locks can't be used for that purpose since it is illegal for
79 * a thread to acquire a lock it already holds, even as a reader). The sole
80 * purpose of these macros is to guarantee that the peer queue will not
81 * disappear (due to closing peer) while it is used. It is safe to use
82 * PT_ENTER_READ/PT_EXIT_READ brackets across calls like putq/putnext (since
83 * they are not real locks but reference counts).
84 *
85 * PT_ENTER_WRITE/PT_EXIT_WRITE brackets are used ONLY in master/slave
86 * open/close paths to modify ptm_rdq and pts_rdq fields. These fields should
87 * be set to appropriate queues *after* qprocson() is called during open (to
88 * prevent peer from accessing the queue with incomplete plumbing) and set to
89 * NULL before qprocsoff() is called during close.
90 *
91 * The pt_nullmsg field is only used in open/close routines and it is also
92 * protected by PT_ENTER_WRITE/PT_EXIT_WRITE brackets to avoid extra mutex
93 * holds.
94 *
95 * Lock Ordering:
96 *
97 * If both ptms_lock and per-pty lock should be held, ptms_lock should always
98 * be entered first, followed by per-pty lock.
99 *
100 * See ptms.h, ptm.c and ptms_conf.c fore more information.
101 *
102 */
103
104 #include <sys/types.h>
105 #include <sys/param.h>
106 #include <sys/sysmacros.h>
107 #include <sys/stream.h>
108 #include <sys/stropts.h>
109 #include <sys/stat.h>
110 #include <sys/errno.h>
111 #include <sys/debug.h>
112 #include <sys/cmn_err.h>
113 #include <sys/ptms.h>
114 #include <sys/systm.h>
115 #include <sys/modctl.h>
116 #include <sys/conf.h>
117 #include <sys/ddi.h>
118 #include <sys/sunddi.h>
119 #include <sys/cred.h>
120 #include <sys/zone.h>
121
122 #ifdef DEBUG
123 int pts_debug = 0;
124 #define DBG(a) if (pts_debug) cmn_err(CE_NOTE, a)
125 #else
126 #define DBG(a)
127 #endif
128
129 static int ptsopen(queue_t *, dev_t *, int, int, cred_t *);
130 static int ptsclose(queue_t *, int, cred_t *);
131 static void ptswput(queue_t *, mblk_t *);
132 static void ptsrsrv(queue_t *);
133 static void ptswsrv(queue_t *);
134
135 /*
136 * Slave Stream Pseudo Terminal Module: stream data structure definitions
137 */
138 static struct module_info pts_info = {
139 0xface,
140 "pts",
141 0,
142 512,
143 512,
144 128
145 };
146
147 static struct qinit ptsrint = {
148 NULL,
149 (int (*)()) ptsrsrv,
150 ptsopen,
151 ptsclose,
152 NULL,
153 &pts_info,
154 NULL
155 };
156
157 static struct qinit ptswint = {
158 (int (*)()) ptswput,
159 (int (*)()) ptswsrv,
160 NULL,
161 NULL,
162 NULL,
163 &pts_info,
164 NULL
165 };
166
167 static struct streamtab ptsinfo = {
168 &ptsrint,
169 &ptswint,
170 NULL,
171 NULL
172 };
173
174 static int pts_devinfo(dev_info_t *, ddi_info_cmd_t, void *, void **);
175 static int pts_attach(dev_info_t *, ddi_attach_cmd_t);
176 static int pts_detach(dev_info_t *, ddi_detach_cmd_t);
177
178 #define PTS_CONF_FLAG (D_NEW | D_MP)
179
180 /*
181 * this will define (struct cb_ops cb_pts_ops) and (struct dev_ops pts_ops)
182 */
183 DDI_DEFINE_STREAM_OPS(pts_ops, nulldev, nulldev, \
184 pts_attach, pts_detach, nodev, \
185 pts_devinfo, PTS_CONF_FLAG, &ptsinfo, ddi_quiesce_not_supported);
186
187 /*
188 * Module linkage information for the kernel.
189 */
190
191 static struct modldrv modldrv = {
192 &mod_driverops, /* Type of module. This one is a pseudo driver */
193 "Slave Stream Pseudo Terminal driver 'pts'",
194 &pts_ops, /* driver ops */
195 };
196
197 static struct modlinkage modlinkage = {
198 MODREV_1,
199 &modldrv,
200 NULL
201 };
202
203 int
_init(void)204 _init(void)
205 {
206 int rc;
207
208 if ((rc = mod_install(&modlinkage)) == 0)
209 ptms_init();
210 return (rc);
211 }
212
213
214 int
_fini(void)215 _fini(void)
216 {
217 return (mod_remove(&modlinkage));
218 }
219
220 int
_info(struct modinfo * modinfop)221 _info(struct modinfo *modinfop)
222 {
223 return (mod_info(&modlinkage, modinfop));
224 }
225
226 static int
pts_attach(dev_info_t * devi,ddi_attach_cmd_t cmd)227 pts_attach(dev_info_t *devi, ddi_attach_cmd_t cmd)
228 {
229 if (cmd != DDI_ATTACH)
230 return (DDI_FAILURE);
231
232 mutex_enter(&ptms_lock);
233 pts_dip = devi;
234 mutex_exit(&ptms_lock);
235
236 return (DDI_SUCCESS);
237 }
238
239 /*ARGSUSED*/
240 static int
pts_detach(dev_info_t * devi,ddi_detach_cmd_t cmd)241 pts_detach(dev_info_t *devi, ddi_detach_cmd_t cmd)
242 {
243 if (cmd != DDI_DETACH)
244 return (DDI_FAILURE);
245
246 /*
247 * For now, pts cannot be detached.
248 */
249 return (DDI_FAILURE);
250 }
251
252 /*ARGSUSED*/
253 static int
pts_devinfo(dev_info_t * dip,ddi_info_cmd_t infocmd,void * arg,void ** result)254 pts_devinfo(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg,
255 void **result)
256 {
257 int error;
258
259 switch (infocmd) {
260 case DDI_INFO_DEVT2DEVINFO:
261 if (pts_dip == NULL) {
262 error = DDI_FAILURE;
263 } else {
264 *result = (void *)pts_dip;
265 error = DDI_SUCCESS;
266 }
267 break;
268 case DDI_INFO_DEVT2INSTANCE:
269 *result = (void *)0;
270 error = DDI_SUCCESS;
271 break;
272 default:
273 error = DDI_FAILURE;
274 }
275 return (error);
276 }
277
278 /* ARGSUSED */
279 /*
280 * Open the slave device. Reject a clone open and do not allow the
281 * driver to be pushed. If the slave/master pair is locked or if
282 * the master is not open, return EACCESS.
283 * Upon success, store the write queue pointer in private data and
284 * set the PTSOPEN bit in the pt_state field.
285 */
286 static int
ptsopen(queue_t * rqp,dev_t * devp,int oflag,int sflag,cred_t * credp)287 ptsopen(
288 queue_t *rqp, /* pointer to the read side queue */
289 dev_t *devp, /* pointer to stream tail's dev */
290 int oflag, /* the user open(2) supplied flags */
291 int sflag, /* open state flag */
292 cred_t *credp) /* credentials */
293 {
294 struct pt_ttys *ptsp;
295 mblk_t *mp;
296 mblk_t *mop; /* ptr to a setopts message block */
297 minor_t dminor = getminor(*devp);
298 struct stroptions *sop;
299
300 DDBG("entering ptsopen(%d)", dminor);
301
302 if (sflag != 0) {
303 return (EINVAL);
304 }
305
306 mutex_enter(&ptms_lock);
307 ptsp = ptms_minor2ptty(dminor);
308
309 if (ptsp == NULL) {
310 mutex_exit(&ptms_lock);
311 return (ENXIO);
312 }
313 mutex_enter(&ptsp->pt_lock);
314
315 /*
316 * Prevent opens from zones other than the one blessed by ptm. We
317 * can't even allow the global zone to open all pts's, as it would
318 * otherwise inproperly be able to claim pts's already opened by zones.
319 */
320 if (ptsp->pt_zoneid != getzoneid()) {
321 mutex_exit(&ptsp->pt_lock);
322 mutex_exit(&ptms_lock);
323 return (EPERM);
324 }
325
326 /*
327 * Allow reopen of this device.
328 */
329 if (rqp->q_ptr != NULL) {
330 ASSERT(rqp->q_ptr == ptsp);
331 ASSERT(ptsp->pts_rdq == rqp);
332 mutex_exit(&ptsp->pt_lock);
333 mutex_exit(&ptms_lock);
334 return (0);
335 }
336
337 DDBGP("ptsopen: p = %p\n", (uintptr_t)ptsp);
338 DDBG("ptsopen: state = %x\n", ptsp->pt_state);
339
340
341 ASSERT(ptsp->pt_minor == dminor);
342
343 if ((ptsp->pt_state & PTLOCK) || !(ptsp->pt_state & PTMOPEN)) {
344 mutex_exit(&ptsp->pt_lock);
345 mutex_exit(&ptms_lock);
346 return (EAGAIN);
347 }
348
349 /*
350 * if already, open simply return...
351 */
352 if (ptsp->pt_state & PTSOPEN) {
353 ASSERT(rqp->q_ptr == ptsp);
354 ASSERT(ptsp->pts_rdq == rqp);
355 mutex_exit(&ptsp->pt_lock);
356 mutex_exit(&ptms_lock);
357 return (0);
358 }
359
360 /*
361 * Allocate message block for setting stream head options.
362 */
363 if ((mop = allocb(sizeof (struct stroptions), BPRI_MED)) == NULL) {
364 mutex_exit(&ptsp->pt_lock);
365 mutex_exit(&ptms_lock);
366 return (ENOMEM);
367 }
368
369 /*
370 * Slave should send zero-length message to a master when it is
371 * closing. If memory is low at that time, master will not detect slave
372 * closes, this pty will not be deallocated. So, preallocate this
373 * zero-length message block early.
374 */
375 if ((mp = allocb(0, BPRI_MED)) == NULL) {
376 mutex_exit(&ptsp->pt_lock);
377 mutex_exit(&ptms_lock);
378 freemsg(mop);
379 return (ENOMEM);
380 }
381
382 ptsp->pt_state |= PTSOPEN;
383
384 WR(rqp)->q_ptr = rqp->q_ptr = ptsp;
385
386 mutex_exit(&ptsp->pt_lock);
387 mutex_exit(&ptms_lock);
388
389 qprocson(rqp);
390
391 /*
392 * After qprocson pts driver is fully plumbed into the stream and can
393 * send/receive messages. Setting pts_rdq will allow master side to send
394 * messages to the slave. This setting can't occur before qprocson() is
395 * finished because slave is not ready to process them.
396 */
397 PT_ENTER_WRITE(ptsp);
398 ptsp->pts_rdq = rqp;
399 ASSERT(ptsp->pt_nullmsg == NULL);
400 ptsp->pt_nullmsg = mp;
401 PT_EXIT_WRITE(ptsp);
402
403 /*
404 * set up hi/lo water marks on stream head read queue
405 * and add controlling tty if not set
406 */
407
408 mop->b_datap->db_type = M_SETOPTS;
409 mop->b_wptr += sizeof (struct stroptions);
410 sop = (struct stroptions *)mop->b_rptr;
411 sop->so_flags = SO_HIWAT | SO_LOWAT | SO_ISTTY;
412 sop->so_hiwat = 512;
413 sop->so_lowat = 256;
414 putnext(rqp, mop);
415
416 return (0);
417 }
418
419
420
421 /*
422 * Find the address to private data identifying the slave's write
423 * queue. Send a 0-length msg up the slave's read queue to designate
424 * the master is closing. Uattach the master from the slave by nulling
425 * out master's write queue field in private data.
426 */
427 /*ARGSUSED1*/
428 static int
ptsclose(queue_t * rqp,int flag,cred_t * credp)429 ptsclose(queue_t *rqp, int flag, cred_t *credp)
430 {
431 struct pt_ttys *ptsp;
432 queue_t *wqp;
433 mblk_t *mp;
434 mblk_t *bp;
435
436 /*
437 * q_ptr should never be NULL in the close routine and it is checked in
438 * DEBUG kernel by ASSERT. For non-DEBUG kernel the attempt is made to
439 * behave gracefully.
440 */
441 ASSERT(rqp->q_ptr != NULL);
442 if (rqp->q_ptr == NULL) {
443 qprocsoff(rqp);
444 return (0);
445 }
446
447 ptsp = (struct pt_ttys *)rqp->q_ptr;
448
449 /*
450 * Slave is going to close and doesn't want any new messages coming
451 * from the master side, so set pts_rdq to NULL. This should be done
452 * before call to qprocsoff() since slave can't process additional
453 * messages from the master after qprocsoff is called.
454 */
455 PT_ENTER_WRITE(ptsp);
456 mp = ptsp->pt_nullmsg;
457 ptsp->pt_nullmsg = NULL;
458 ptsp->pts_rdq = NULL;
459 PT_EXIT_WRITE(ptsp);
460
461 /*
462 * Drain the ouput
463 */
464 wqp = WR(rqp);
465 PT_ENTER_READ(ptsp);
466 while ((bp = getq(wqp)) != NULL) {
467 if (ptsp->ptm_rdq) {
468 putnext(ptsp->ptm_rdq, bp);
469 } else if (bp->b_datap->db_type == M_IOCTL) {
470 bp->b_datap->db_type = M_IOCNAK;
471 freemsg(bp->b_cont);
472 bp->b_cont = NULL;
473 qreply(wqp, bp);
474 } else {
475 freemsg(bp);
476 }
477 }
478 /*
479 * qenable master side write queue so that it can flush
480 * its messages as slaves's read queue is going away
481 */
482 if (ptsp->ptm_rdq) {
483 if (mp)
484 putnext(ptsp->ptm_rdq, mp);
485 else
486 qenable(WR(ptsp->ptm_rdq));
487 } else
488 freemsg(mp);
489 PT_EXIT_READ(ptsp);
490
491 qprocsoff(rqp);
492
493 rqp->q_ptr = NULL;
494 WR(rqp)->q_ptr = NULL;
495
496 ptms_close(ptsp, PTSOPEN | PTSTTY);
497
498 return (0);
499 }
500
501
502 /*
503 * The wput procedure will only handle flush messages.
504 * All other messages are queued and the write side
505 * service procedure sends them off to the master side.
506 */
507 static void
ptswput(queue_t * qp,mblk_t * mp)508 ptswput(queue_t *qp, mblk_t *mp)
509 {
510 struct pt_ttys *ptsp;
511 struct iocblk *iocp;
512 unsigned char type = mp->b_datap->db_type;
513
514 DBG(("entering ptswput\n"));
515 ASSERT(qp->q_ptr);
516
517 ptsp = (struct pt_ttys *)qp->q_ptr;
518 PT_ENTER_READ(ptsp);
519 if (ptsp->ptm_rdq == NULL) {
520 DBG(("in write put proc but no master\n"));
521 /*
522 * NAK ioctl as slave side read queue is gone.
523 * Or else free the message.
524 */
525 if (mp->b_datap->db_type == M_IOCTL) {
526 mp->b_datap->db_type = M_IOCNAK;
527 freemsg(mp->b_cont);
528 mp->b_cont = NULL;
529 qreply(qp, mp);
530 } else
531 freemsg(mp);
532 PT_EXIT_READ(ptsp);
533 return;
534 }
535
536 if (type >= QPCTL) {
537 switch (type) {
538
539 /*
540 * if write queue request, flush slave's write
541 * queue and send FLUSHR to ptm. If read queue
542 * request, send FLUSHR to ptm.
543 */
544 case M_FLUSH:
545 DBG(("pts got flush request\n"));
546 if (*mp->b_rptr & FLUSHW) {
547
548 DBG(("got FLUSHW, flush pts write Q\n"));
549 if (*mp->b_rptr & FLUSHBAND)
550 /*
551 * if it is a FLUSHBAND, do flushband.
552 */
553 flushband(qp, *(mp->b_rptr + 1), FLUSHDATA);
554 else
555 flushq(qp, FLUSHDATA);
556
557 *mp->b_rptr &= ~FLUSHW;
558 if ((*mp->b_rptr & FLUSHR) == 0) {
559 /*
560 * FLUSHW only. Change to FLUSHR and putnext
561 * to ptm, then we are done.
562 */
563 *mp->b_rptr |= FLUSHR;
564 if (ptsp->ptm_rdq)
565 putnext(ptsp->ptm_rdq, mp);
566 break;
567 } else {
568 mblk_t *nmp;
569
570 /* It is a FLUSHRW. Duplicate the mblk */
571 nmp = copyb(mp);
572 if (nmp) {
573 /*
574 * Change FLUSHW to FLUSHR before
575 * putnext to ptm.
576 */
577 DBG(("putnext nmp(FLUSHR) to ptm\n"));
578 *nmp->b_rptr |= FLUSHR;
579 if (ptsp->ptm_rdq)
580 putnext(ptsp->ptm_rdq, nmp);
581 }
582 }
583 }
584 /*
585 * Since the packet module will toss any
586 * M_FLUSHES sent to the master's stream head
587 * read queue, we simply turn it around here.
588 */
589 if (*mp->b_rptr & FLUSHR) {
590 ASSERT(RD(qp)->q_first == NULL);
591 DBG(("qreply(qp) turning FLUSHR around\n"));
592 qreply(qp, mp);
593 } else {
594 freemsg(mp);
595 }
596 break;
597
598 case M_READ:
599 /* Caused by ldterm - can not pass to master */
600 freemsg(mp);
601 break;
602
603 default:
604 if (ptsp->ptm_rdq)
605 putnext(ptsp->ptm_rdq, mp);
606 break;
607 }
608 PT_EXIT_READ(ptsp);
609 return;
610 }
611
612 switch (type) {
613
614 case M_IOCTL:
615 /*
616 * For case PTSSTTY set the flag PTSTTY and ACK
617 * the ioctl so that the user program can push
618 * the associated modules to get tty semantics.
619 * See bugid 4025044
620 */
621 iocp = (struct iocblk *)mp->b_rptr;
622 switch (iocp->ioc_cmd) {
623 default:
624 break;
625
626 case PTSSTTY:
627 if (ptsp->pt_state & PTSTTY) {
628 mp->b_datap->db_type = M_IOCNAK;
629 iocp->ioc_error = EEXIST;
630 } else {
631 mp->b_datap->db_type = M_IOCACK;
632 mutex_enter(&ptsp->pt_lock);
633 ptsp->pt_state |= PTSTTY;
634 mutex_exit(&ptsp->pt_lock);
635 iocp->ioc_error = 0;
636 }
637 iocp->ioc_count = 0;
638 qreply(qp, mp);
639 PT_EXIT_READ(ptsp);
640 return;
641 }
642
643 default:
644 /*
645 * send other messages to the master
646 */
647 DBG(("put msg on slave's write queue\n"));
648 (void) putq(qp, mp);
649 break;
650 }
651
652 PT_EXIT_READ(ptsp);
653 DBG(("return from ptswput()\n"));
654 }
655
656
657 /*
658 * enable the write side of the master. This triggers the
659 * master to send any messages queued on its write side to
660 * the read side of this slave.
661 */
662 static void
ptsrsrv(queue_t * qp)663 ptsrsrv(queue_t *qp)
664 {
665 struct pt_ttys *ptsp;
666
667 DBG(("entering ptsrsrv\n"));
668 ASSERT(qp->q_ptr);
669
670 ptsp = (struct pt_ttys *)qp->q_ptr;
671 PT_ENTER_READ(ptsp);
672 if (ptsp->ptm_rdq == NULL) {
673 DBG(("in read srv proc but no master\n"));
674 PT_EXIT_READ(ptsp);
675 return;
676 }
677 qenable(WR(ptsp->ptm_rdq));
678 PT_EXIT_READ(ptsp);
679 DBG(("leaving ptsrsrv\n"));
680 }
681
682 /*
683 * If there are messages on this queue that can be sent to
684 * master, send them via putnext(). Else, if queued messages
685 * cannot be sent, leave them on this queue. If priority
686 * messages on this queue, send them to master no matter what.
687 */
688 static void
ptswsrv(queue_t * qp)689 ptswsrv(queue_t *qp)
690 {
691 struct pt_ttys *ptsp;
692 queue_t *ptm_rdq;
693 mblk_t *mp;
694
695 DBG(("entering ptswsrv\n"));
696 ASSERT(qp->q_ptr);
697
698 ptsp = (struct pt_ttys *)qp->q_ptr;
699 PT_ENTER_READ(ptsp);
700 if (ptsp->ptm_rdq == NULL) {
701 DBG(("in write srv proc but no master\n"));
702 /*
703 * Free messages on the write queue and send
704 * NAK for any M_IOCTL type messages to wakeup
705 * the user process waiting for ACK/NAK from
706 * the ioctl invocation
707 */
708 while ((mp = getq(qp)) != NULL) {
709 if (mp->b_datap->db_type == M_IOCTL) {
710 mp->b_datap->db_type = M_IOCNAK;
711 freemsg(mp->b_cont);
712 mp->b_cont = NULL;
713 qreply(qp, mp);
714 } else
715 freemsg(mp);
716 }
717 PT_EXIT_READ(ptsp);
718 return;
719 } else {
720 ptm_rdq = ptsp->ptm_rdq;
721 }
722
723 /*
724 * while there are messages on this write queue...
725 */
726 while ((mp = getq(qp)) != NULL) {
727 /*
728 * if don't have control message and cannot put
729 * msg. on master's read queue, put it back on
730 * this queue.
731 */
732 if (mp->b_datap->db_type <= QPCTL &&
733 !bcanputnext(ptm_rdq, mp->b_band)) {
734 DBG(("put msg. back on Q\n"));
735 (void) putbq(qp, mp);
736 break;
737 }
738 /*
739 * else send the message up master's stream
740 */
741 DBG(("send message to master\n"));
742 putnext(ptm_rdq, mp);
743 }
744 DBG(("leaving ptswsrv\n"));
745 PT_EXIT_READ(ptsp);
746 }
747