pipe - fix UP build error.
[dragonfly.git] / sys / kern / sys_pipe.c
1 /*
2  * Copyright (c) 1996 John S. Dyson
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice immediately at the beginning of the file, without modification,
10  *    this list of conditions, and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. Absolutely no warranty of function or purpose is made by the author
15  *    John S. Dyson.
16  * 4. Modifications may be freely made to this file if the above conditions
17  *    are met.
18  *
19  * $FreeBSD: src/sys/kern/sys_pipe.c,v 1.60.2.13 2002/08/05 15:05:15 des Exp $
20  * $DragonFly: src/sys/kern/sys_pipe.c,v 1.50 2008/09/09 04:06:13 dillon Exp $
21  */
22
23 /*
24  * This file contains a high-performance replacement for the socket-based
25  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
26  * all features of sockets, but does do everything that pipes normally
27  * do.
28  */
29 #include <sys/param.h>
30 #include <sys/systm.h>
31 #include <sys/kernel.h>
32 #include <sys/proc.h>
33 #include <sys/fcntl.h>
34 #include <sys/file.h>
35 #include <sys/filedesc.h>
36 #include <sys/filio.h>
37 #include <sys/ttycom.h>
38 #include <sys/stat.h>
39 #include <sys/poll.h>
40 #include <sys/select.h>
41 #include <sys/signalvar.h>
42 #include <sys/sysproto.h>
43 #include <sys/pipe.h>
44 #include <sys/vnode.h>
45 #include <sys/uio.h>
46 #include <sys/event.h>
47 #include <sys/globaldata.h>
48 #include <sys/module.h>
49 #include <sys/malloc.h>
50 #include <sys/sysctl.h>
51 #include <sys/socket.h>
52
53 #include <vm/vm.h>
54 #include <vm/vm_param.h>
55 #include <sys/lock.h>
56 #include <vm/vm_object.h>
57 #include <vm/vm_kern.h>
58 #include <vm/vm_extern.h>
59 #include <vm/pmap.h>
60 #include <vm/vm_map.h>
61 #include <vm/vm_page.h>
62 #include <vm/vm_zone.h>
63
64 #include <sys/file2.h>
65
66 #include <machine/cpufunc.h>
67
68 /*
69  * interfaces to the outside world
70  */
71 static int pipe_read (struct file *fp, struct uio *uio, 
72                 struct ucred *cred, int flags);
73 static int pipe_write (struct file *fp, struct uio *uio, 
74                 struct ucred *cred, int flags);
75 static int pipe_close (struct file *fp);
76 static int pipe_shutdown (struct file *fp, int how);
77 static int pipe_poll (struct file *fp, int events, struct ucred *cred);
78 static int pipe_kqfilter (struct file *fp, struct knote *kn);
79 static int pipe_stat (struct file *fp, struct stat *sb, struct ucred *cred);
80 static int pipe_ioctl (struct file *fp, u_long cmd, caddr_t data, struct ucred *cred);
81
82 static struct fileops pipeops = {
83         .fo_read = pipe_read, 
84         .fo_write = pipe_write,
85         .fo_ioctl = pipe_ioctl,
86         .fo_poll = pipe_poll,
87         .fo_kqfilter = pipe_kqfilter,
88         .fo_stat = pipe_stat,
89         .fo_close = pipe_close,
90         .fo_shutdown = pipe_shutdown
91 };
92
93 static void     filt_pipedetach(struct knote *kn);
94 static int      filt_piperead(struct knote *kn, long hint);
95 static int      filt_pipewrite(struct knote *kn, long hint);
96
97 static struct filterops pipe_rfiltops =
98         { 1, NULL, filt_pipedetach, filt_piperead };
99 static struct filterops pipe_wfiltops =
100         { 1, NULL, filt_pipedetach, filt_pipewrite };
101
102 MALLOC_DEFINE(M_PIPE, "pipe", "pipe structures");
103
104 /*
105  * Default pipe buffer size(s), this can be kind-of large now because pipe
106  * space is pageable.  The pipe code will try to maintain locality of
107  * reference for performance reasons, so small amounts of outstanding I/O
108  * will not wipe the cache.
109  */
110 #define MINPIPESIZE (PIPE_SIZE/3)
111 #define MAXPIPESIZE (2*PIPE_SIZE/3)
112
113 /*
114  * Limit the number of "big" pipes
115  */
116 #define LIMITBIGPIPES   64
117 #define PIPEQ_MAX_CACHE 16      /* per-cpu pipe structure cache */
118
119 static int pipe_maxbig = LIMITBIGPIPES;
120 static int pipe_maxcache = PIPEQ_MAX_CACHE;
121 static int pipe_bigcount;
122 static int pipe_nbig;
123 static int pipe_bcache_alloc;
124 static int pipe_bkmem_alloc;
125 static int pipe_rblocked_count;
126 static int pipe_wblocked_count;
127
128 SYSCTL_NODE(_kern, OID_AUTO, pipe, CTLFLAG_RW, 0, "Pipe operation");
129 SYSCTL_INT(_kern_pipe, OID_AUTO, nbig,
130         CTLFLAG_RD, &pipe_nbig, 0, "numer of big pipes allocated");
131 SYSCTL_INT(_kern_pipe, OID_AUTO, bigcount,
132         CTLFLAG_RW, &pipe_bigcount, 0, "number of times pipe expanded");
133 SYSCTL_INT(_kern_pipe, OID_AUTO, rblocked,
134         CTLFLAG_RW, &pipe_rblocked_count, 0, "number of times pipe expanded");
135 SYSCTL_INT(_kern_pipe, OID_AUTO, wblocked,
136         CTLFLAG_RW, &pipe_wblocked_count, 0, "number of times pipe expanded");
137 SYSCTL_INT(_kern_pipe, OID_AUTO, maxcache,
138         CTLFLAG_RW, &pipe_maxcache, 0, "max pipes cached per-cpu");
139 SYSCTL_INT(_kern_pipe, OID_AUTO, maxbig,
140         CTLFLAG_RW, &pipe_maxbig, 0, "max number of big pipes");
141 #ifdef SMP
142 static int pipe_delay = 5000;   /* 5uS default */
143 SYSCTL_INT(_kern_pipe, OID_AUTO, delay,
144         CTLFLAG_RW, &pipe_delay, 0, "SMP delay optimization in ns");
145 static int pipe_mpsafe = 0;
146 SYSCTL_INT(_kern_pipe, OID_AUTO, mpsafe,
147         CTLFLAG_RW, &pipe_mpsafe, 0, "");
148 #endif
149 #if !defined(NO_PIPE_SYSCTL_STATS)
150 SYSCTL_INT(_kern_pipe, OID_AUTO, bcache_alloc,
151         CTLFLAG_RW, &pipe_bcache_alloc, 0, "pipe buffer from pcpu cache");
152 SYSCTL_INT(_kern_pipe, OID_AUTO, bkmem_alloc,
153         CTLFLAG_RW, &pipe_bkmem_alloc, 0, "pipe buffer from kmem");
154 #endif
155
156 static void pipeclose (struct pipe *cpipe);
157 static void pipe_free_kmem (struct pipe *cpipe);
158 static int pipe_create (struct pipe **cpipep);
159 static __inline void pipeselwakeup (struct pipe *cpipe);
160 static int pipespace (struct pipe *cpipe, int size);
161
162 static __inline void
163 pipeselwakeup(struct pipe *cpipe)
164 {
165         if (cpipe->pipe_state & PIPE_SEL) {
166                 get_mplock();
167                 cpipe->pipe_state &= ~PIPE_SEL;
168                 selwakeup(&cpipe->pipe_sel);
169                 rel_mplock();
170         }
171         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio) {
172                 get_mplock();
173                 pgsigio(cpipe->pipe_sigio, SIGIO, 0);
174                 rel_mplock();
175         }
176         if (SLIST_FIRST(&cpipe->pipe_sel.si_note)) {
177                 get_mplock();
178                 KNOTE(&cpipe->pipe_sel.si_note, 0);
179                 rel_mplock();
180         }
181 }
182
183 /*
184  * These routines are called before and after a UIO.  The UIO
185  * may block, causing our held tokens to be lost temporarily.
186  *
187  * We use these routines to serialize reads against other reads
188  * and writes against other writes.
189  *
190  * The read token is held on entry so *ipp does not race.
191  */
192 static __inline int
193 pipe_start_uio(struct pipe *cpipe, u_int *ipp)
194 {
195         int error;
196
197         while (*ipp) {
198                 *ipp = -1;
199                 error = tsleep(ipp, PCATCH, "pipexx", 0);
200                 if (error)
201                         return (error);
202         }
203         *ipp = 1;
204         return (0);
205 }
206
207 static __inline void
208 pipe_end_uio(struct pipe *cpipe, u_int *ipp)
209 {
210         if (*ipp < 0) {
211                 *ipp = 0;
212                 wakeup(ipp);
213         } else {
214                 *ipp = 0;
215         }
216 }
217
218 static __inline void
219 pipe_get_mplock(int *save)
220 {
221 #ifdef SMP
222         if (pipe_mpsafe == 0) {
223                 get_mplock();
224                 *save = 1;
225         } else
226 #endif
227         {
228                 *save = 0;
229         }
230 }
231
232 static __inline void
233 pipe_rel_mplock(int *save)
234 {
235 #ifdef SMP
236         if (*save)
237                 rel_mplock();
238 #endif
239 }
240
241
242 /*
243  * The pipe system call for the DTYPE_PIPE type of pipes
244  *
245  * pipe_ARgs(int dummy)
246  */
247
248 /* ARGSUSED */
249 int
250 sys_pipe(struct pipe_args *uap)
251 {
252         struct thread *td = curthread;
253         struct proc *p = td->td_proc;
254         struct file *rf, *wf;
255         struct pipe *rpipe, *wpipe;
256         int fd1, fd2, error;
257
258         KKASSERT(p);
259
260         rpipe = wpipe = NULL;
261         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
262                 pipeclose(rpipe); 
263                 pipeclose(wpipe); 
264                 return (ENFILE);
265         }
266         
267         error = falloc(p, &rf, &fd1);
268         if (error) {
269                 pipeclose(rpipe);
270                 pipeclose(wpipe);
271                 return (error);
272         }
273         uap->sysmsg_fds[0] = fd1;
274
275         /*
276          * Warning: once we've gotten past allocation of the fd for the
277          * read-side, we can only drop the read side via fdrop() in order
278          * to avoid races against processes which manage to dup() the read
279          * side while we are blocked trying to allocate the write side.
280          */
281         rf->f_type = DTYPE_PIPE;
282         rf->f_flag = FREAD | FWRITE;
283         rf->f_ops = &pipeops;
284         rf->f_data = rpipe;
285         error = falloc(p, &wf, &fd2);
286         if (error) {
287                 fsetfd(p, NULL, fd1);
288                 fdrop(rf);
289                 /* rpipe has been closed by fdrop(). */
290                 pipeclose(wpipe);
291                 return (error);
292         }
293         wf->f_type = DTYPE_PIPE;
294         wf->f_flag = FREAD | FWRITE;
295         wf->f_ops = &pipeops;
296         wf->f_data = wpipe;
297         uap->sysmsg_fds[1] = fd2;
298
299         rpipe->pipe_slock = kmalloc(sizeof(struct lock),
300                                     M_PIPE, M_WAITOK|M_ZERO);
301         wpipe->pipe_slock = rpipe->pipe_slock;
302         rpipe->pipe_peer = wpipe;
303         wpipe->pipe_peer = rpipe;
304         lockinit(rpipe->pipe_slock, "pipecl", 0, 0);
305
306         /*
307          * Once activated the peer relationship remains valid until
308          * both sides are closed.
309          */
310         fsetfd(p, rf, fd1);
311         fsetfd(p, wf, fd2);
312         fdrop(rf);
313         fdrop(wf);
314
315         return (0);
316 }
317
318 /*
319  * Allocate kva for pipe circular buffer, the space is pageable
320  * This routine will 'realloc' the size of a pipe safely, if it fails
321  * it will retain the old buffer.
322  * If it fails it will return ENOMEM.
323  */
324 static int
325 pipespace(struct pipe *cpipe, int size)
326 {
327         struct vm_object *object;
328         caddr_t buffer;
329         int npages, error;
330
331         npages = round_page(size) / PAGE_SIZE;
332         object = cpipe->pipe_buffer.object;
333
334         /*
335          * [re]create the object if necessary and reserve space for it
336          * in the kernel_map.  The object and memory are pageable.  On
337          * success, free the old resources before assigning the new
338          * ones.
339          */
340         if (object == NULL || object->size != npages) {
341                 get_mplock();
342                 object = vm_object_allocate(OBJT_DEFAULT, npages);
343                 buffer = (caddr_t)vm_map_min(&kernel_map);
344
345                 error = vm_map_find(&kernel_map, object, 0,
346                                     (vm_offset_t *)&buffer, size,
347                                     1,
348                                     VM_MAPTYPE_NORMAL,
349                                     VM_PROT_ALL, VM_PROT_ALL,
350                                     0);
351
352                 if (error != KERN_SUCCESS) {
353                         vm_object_deallocate(object);
354                         rel_mplock();
355                         return (ENOMEM);
356                 }
357                 pipe_free_kmem(cpipe);
358                 rel_mplock();
359                 cpipe->pipe_buffer.object = object;
360                 cpipe->pipe_buffer.buffer = buffer;
361                 cpipe->pipe_buffer.size = size;
362                 ++pipe_bkmem_alloc;
363         } else {
364                 ++pipe_bcache_alloc;
365         }
366         cpipe->pipe_buffer.rindex = 0;
367         cpipe->pipe_buffer.windex = 0;
368         return (0);
369 }
370
371 /*
372  * Initialize and allocate VM and memory for pipe, pulling the pipe from
373  * our per-cpu cache if possible.  For now make sure it is sized for the
374  * smaller PIPE_SIZE default.
375  */
376 static int
377 pipe_create(struct pipe **cpipep)
378 {
379         globaldata_t gd = mycpu;
380         struct pipe *cpipe;
381         int error;
382
383         if ((cpipe = gd->gd_pipeq) != NULL) {
384                 gd->gd_pipeq = cpipe->pipe_peer;
385                 --gd->gd_pipeqcount;
386                 cpipe->pipe_peer = NULL;
387                 cpipe->pipe_wantwcnt = 0;
388         } else {
389                 cpipe = kmalloc(sizeof(struct pipe), M_PIPE, M_WAITOK|M_ZERO);
390         }
391         *cpipep = cpipe;
392         if ((error = pipespace(cpipe, PIPE_SIZE)) != 0)
393                 return (error);
394         vfs_timestamp(&cpipe->pipe_ctime);
395         cpipe->pipe_atime = cpipe->pipe_ctime;
396         cpipe->pipe_mtime = cpipe->pipe_ctime;
397         lwkt_token_init(&cpipe->pipe_rlock);
398         lwkt_token_init(&cpipe->pipe_wlock);
399         return (0);
400 }
401
402 /*
403  * MPALMOSTSAFE (acquires mplock)
404  */
405 static int
406 pipe_read(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
407 {
408         struct pipe *rpipe;
409         int error;
410         int orig_resid;
411         int nread = 0;
412         int nbio;
413         u_int size;     /* total bytes available */
414         u_int nsize;    /* total bytes to read */
415         u_int rindex;   /* contiguous bytes available */
416         int notify_writer;
417         lwkt_tokref rlock;
418         lwkt_tokref wlock;
419         int mpsave;
420
421         /*
422          * Degenerate case
423          */
424         orig_resid = uio->uio_resid;
425         if (orig_resid == 0)
426                 return(0);
427
428         /*
429          * Setup locks, calculate nbio
430          */
431         pipe_get_mplock(&mpsave);
432         rpipe = (struct pipe *)fp->f_data;
433         lwkt_gettoken(&rlock, &rpipe->pipe_rlock);
434
435         if (fflags & O_FBLOCKING)
436                 nbio = 0;
437         else if (fflags & O_FNONBLOCKING)
438                 nbio = 1;
439         else if (fp->f_flag & O_NONBLOCK)
440                 nbio = 1;
441         else
442                 nbio = 0;
443
444         /*
445          * Reads are serialized.  Note howeverthat pipe_buffer.buffer and
446          * pipe_buffer.size can change out from under us when the number
447          * of bytes in the buffer are zero due to the write-side doing a
448          * pipespace().
449          */
450         error = pipe_start_uio(rpipe, &rpipe->pipe_rip);
451         if (error) {
452                 pipe_rel_mplock(&mpsave);
453                 lwkt_reltoken(&rlock);
454                 return (error);
455         }
456         notify_writer = 0;
457         while (uio->uio_resid) {
458                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
459                 cpu_lfence();
460                 if (size) {
461                         rindex = rpipe->pipe_buffer.rindex &
462                                  (rpipe->pipe_buffer.size - 1);
463                         nsize = size;
464                         if (nsize > rpipe->pipe_buffer.size - rindex)
465                                 nsize = rpipe->pipe_buffer.size - rindex;
466                         if (nsize > (u_int)uio->uio_resid)
467                                 nsize = (u_int)uio->uio_resid;
468
469                         error = uiomove(&rpipe->pipe_buffer.buffer[rindex],
470                                         nsize, uio);
471                         if (error)
472                                 break;
473                         cpu_mfence();
474                         rpipe->pipe_buffer.rindex += nsize;
475                         nread += nsize;
476
477                         /*
478                          * If the FIFO is still over half full just continue
479                          * and do not try to notify the writer yet.
480                          */
481                         if (size - nsize >= (rpipe->pipe_buffer.size >> 1)) {
482                                 notify_writer = 0;
483                                 continue;
484                         }
485
486                         /*
487                          * When the FIFO is less then half full notify any
488                          * waiting writer.  WANTW can be checked while
489                          * holding just the rlock.
490                          */
491                         notify_writer = 1;
492                         if ((rpipe->pipe_state & PIPE_WANTW) == 0)
493                                 continue;
494                 }
495
496                 /*
497                  * If the "write-side" was blocked we wake it up.  This code
498                  * is reached either when the buffer is completely emptied
499                  * or if it becomes more then half-empty.
500                  *
501                  * Pipe_state can only be modified if both the rlock and
502                  * wlock are held.
503                  */
504                 if (rpipe->pipe_state & PIPE_WANTW) {
505                         lwkt_gettoken(&wlock, &rpipe->pipe_wlock);
506                         if (rpipe->pipe_state & PIPE_WANTW) {
507                                 notify_writer = 0;
508                                 rpipe->pipe_state &= ~PIPE_WANTW;
509                                 lwkt_reltoken(&wlock);
510                                 wakeup(rpipe);
511                         } else {
512                                 lwkt_reltoken(&wlock);
513                         }
514                 }
515
516                 /*
517                  * Pick up our copy loop again if the writer sent data to
518                  * us while we were messing around.
519                  *
520                  * On a SMP box poll up to pipe_delay nanoseconds for new
521                  * data.  Typically a value of 2000 to 4000 is sufficient
522                  * to eradicate most IPIs/tsleeps/wakeups when a pipe
523                  * is used for synchronous communications with small packets,
524                  * and 8000 or so (8uS) will pipeline large buffer xfers
525                  * between cpus over a pipe.
526                  *
527                  * For synchronous communications a hit means doing a
528                  * full Awrite-Bread-Bwrite-Aread cycle in less then 2uS,
529                  * where as miss requiring a tsleep/wakeup sequence
530                  * will take 7uS or more.
531                  */
532                 if (rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex)
533                         continue;
534
535 #if defined(SMP) && defined(_RDTSC_SUPPORTED_)
536                 if (pipe_delay) {
537                         int64_t tsc_target;
538                         int good = 0;
539
540                         tsc_target = tsc_get_target(pipe_delay);
541                         while (tsc_test_target(tsc_target) == 0) {
542                                 if (rpipe->pipe_buffer.windex !=
543                                     rpipe->pipe_buffer.rindex) {
544                                         good = 1;
545                                         break;
546                                 }
547                         }
548                         if (good)
549                                 continue;
550                 }
551 #endif
552
553                 /*
554                  * Detect EOF condition, do not set error.
555                  */
556                 if (rpipe->pipe_state & PIPE_REOF)
557                         break;
558
559                 /*
560                  * Break if some data was read, or if this was a non-blocking
561                  * read.
562                  */
563                 if (nread > 0)
564                         break;
565
566                 if (nbio) {
567                         error = EAGAIN;
568                         break;
569                 }
570
571                 /*
572                  * Last chance, interlock with WANTR.
573                  */
574                 lwkt_gettoken(&wlock, &rpipe->pipe_wlock);
575                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
576                 if (size) {
577                         lwkt_reltoken(&wlock);
578                         continue;
579                 }
580
581                 /*
582                  * If there is no more to read in the pipe, reset its
583                  * pointers to the beginning.  This improves cache hit
584                  * stats.
585                  *
586                  * We need both locks to modify both pointers, and there
587                  * must also not be a write in progress or the uiomove()
588                  * in the write might block and temporarily release
589                  * its wlock, then reacquire and update windex.  We are
590                  * only serialized against reads, not writes.
591                  *
592                  * XXX should we even bother resetting the indices?  It
593                  *     might actually be more cache efficient not to.
594                  */
595                 if (rpipe->pipe_buffer.rindex == rpipe->pipe_buffer.windex &&
596                     rpipe->pipe_wip == 0) {
597                         rpipe->pipe_buffer.rindex = 0;
598                         rpipe->pipe_buffer.windex = 0;
599                 }
600
601                 /*
602                  * Wait for more data.
603                  *
604                  * Pipe_state can only be set if both the rlock and wlock
605                  * are held.
606                  */
607                 rpipe->pipe_state |= PIPE_WANTR;
608                 tsleep_interlock(rpipe);
609                 lwkt_reltoken(&wlock);
610                 error = tsleep(rpipe, PCATCH, "piperd", 0);
611                 ++pipe_rblocked_count;
612                 if (error)
613                         break;
614         }
615         pipe_end_uio(rpipe, &rpipe->pipe_rip);
616
617         /*
618          * Uptime last access time
619          */
620         if (error == 0 && nread)
621                 vfs_timestamp(&rpipe->pipe_atime);
622
623         /*
624          * If we drained the FIFO more then half way then handle
625          * write blocking hysteresis.
626          *
627          * Note that PIPE_WANTW cannot be set by the writer without
628          * it holding both rlock and wlock, so we can test it
629          * while holding just rlock.
630          */
631         if (notify_writer) {
632                 if (rpipe->pipe_state & PIPE_WANTW) {
633                         lwkt_gettoken(&wlock, &rpipe->pipe_wlock);
634                         if (rpipe->pipe_state & PIPE_WANTW) {
635                                 rpipe->pipe_state &= ~PIPE_WANTW;
636                                 lwkt_reltoken(&wlock);
637                                 wakeup(rpipe);
638                         } else {
639                                 lwkt_reltoken(&wlock);
640                         }
641                 }
642         }
643         size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
644         lwkt_reltoken(&rlock);
645
646         /*
647          * If enough space is available in buffer then wakeup sel writers?
648          */
649         if ((rpipe->pipe_buffer.size - size) >= PIPE_BUF)
650                 pipeselwakeup(rpipe);
651         pipe_rel_mplock(&mpsave);
652         return (error);
653 }
654
655 /*
656  * MPALMOSTSAFE - acquires mplock
657  */
658 static int
659 pipe_write(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
660 {
661         int error;
662         int orig_resid;
663         int nbio;
664         struct pipe *wpipe, *rpipe;
665         lwkt_tokref rlock;
666         lwkt_tokref wlock;
667         u_int windex;
668         u_int space;
669         u_int wcount;
670         int mpsave;
671
672         pipe_get_mplock(&mpsave);
673
674         /*
675          * Writes go to the peer.  The peer will always exist.
676          */
677         rpipe = (struct pipe *) fp->f_data;
678         wpipe = rpipe->pipe_peer;
679         lwkt_gettoken(&wlock, &wpipe->pipe_wlock);
680         if (wpipe->pipe_state & PIPE_WEOF) {
681                 pipe_rel_mplock(&mpsave);
682                 lwkt_reltoken(&wlock);
683                 return (EPIPE);
684         }
685
686         /*
687          * Degenerate case (EPIPE takes prec)
688          */
689         if (uio->uio_resid == 0) {
690                 pipe_rel_mplock(&mpsave);
691                 lwkt_reltoken(&wlock);
692                 return(0);
693         }
694
695         /*
696          * Writes are serialized (start_uio must be called with wlock)
697          */
698         error = pipe_start_uio(wpipe, &wpipe->pipe_wip);
699         if (error) {
700                 pipe_rel_mplock(&mpsave);
701                 lwkt_reltoken(&wlock);
702                 return (error);
703         }
704
705         if (fflags & O_FBLOCKING)
706                 nbio = 0;
707         else if (fflags & O_FNONBLOCKING)
708                 nbio = 1;
709         else if (fp->f_flag & O_NONBLOCK)
710                 nbio = 1;
711         else
712                 nbio = 0;
713
714         /*
715          * If it is advantageous to resize the pipe buffer, do
716          * so.  We are write-serialized so we can block safely.
717          */
718         if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
719             (pipe_nbig < pipe_maxbig) &&
720             wpipe->pipe_wantwcnt > 4 &&
721             (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
722                 /* 
723                  * Recheck after lock.
724                  */
725                 lwkt_gettoken(&rlock, &wpipe->pipe_rlock);
726                 if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
727                     (pipe_nbig < pipe_maxbig) &&
728                     (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
729                         atomic_add_int(&pipe_nbig, 1);
730                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
731                                 ++pipe_bigcount;
732                         else
733                                 atomic_subtract_int(&pipe_nbig, 1);
734                 }
735                 lwkt_reltoken(&rlock);
736         }
737
738         orig_resid = uio->uio_resid;
739         wcount = 0;
740
741         while (uio->uio_resid) {
742                 if (wpipe->pipe_state & PIPE_WEOF) {
743                         error = EPIPE;
744                         break;
745                 }
746
747                 windex = wpipe->pipe_buffer.windex &
748                          (wpipe->pipe_buffer.size - 1);
749                 space = wpipe->pipe_buffer.size -
750                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
751                 cpu_lfence();
752
753                 /* Writes of size <= PIPE_BUF must be atomic. */
754                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
755                         space = 0;
756
757                 /* 
758                  * Write to fill, read size handles write hysteresis.  Also
759                  * additional restrictions can cause select-based non-blocking
760                  * writes to spin.
761                  */
762                 if (space > 0) {
763                         u_int segsize;
764
765                         /*
766                          * Transfer size is minimum of uio transfer
767                          * and free space in pipe buffer.
768                          *
769                          * Limit each uiocopy to no more then PIPE_SIZE
770                          * so we can keep the gravy train going on a
771                          * SMP box.  This doubles the performance for
772                          * write sizes > 16K.  Otherwise large writes
773                          * wind up doing an inefficient synchronous
774                          * ping-pong.
775                          */
776                         if (space > (u_int)uio->uio_resid)
777                                 space = (u_int)uio->uio_resid;
778                         if (space > PIPE_SIZE)
779                                 space = PIPE_SIZE;
780
781                         /*
782                          * First segment to transfer is minimum of
783                          * transfer size and contiguous space in
784                          * pipe buffer.  If first segment to transfer
785                          * is less than the transfer size, we've got
786                          * a wraparound in the buffer.
787                          */
788                         segsize = wpipe->pipe_buffer.size - windex;
789                         if (segsize > space)
790                                 segsize = space;
791
792 #ifdef SMP
793                         /*
794                          * If this is the first loop and the reader is
795                          * blocked, do a preemptive wakeup of the reader.
796                          *
797                          * On SMP the IPI latency plus the wlock interlock
798                          * on the reader side is the fastest way to get the
799                          * reader going.  (The scheduler will hard loop on
800                          * lock tokens).
801                          *
802                          * NOTE: We can't clear WANTR here without acquiring
803                          * the rlock, which we don't want to do here!
804                          */
805                         if ((wpipe->pipe_state & PIPE_WANTR) && pipe_mpsafe > 1)
806                                 wakeup(wpipe);
807 #endif
808
809                         /*
810                          * Transfer segment, which may include a wrap-around.
811                          * Update windex to account for both all in one go
812                          * so the reader can read() the data atomically.
813                          */
814                         error = uiomove(&wpipe->pipe_buffer.buffer[windex],
815                                         segsize, uio);
816                         if (error == 0 && segsize < space) {
817                                 segsize = space - segsize;
818                                 error = uiomove(&wpipe->pipe_buffer.buffer[0],
819                                                 segsize, uio);
820                         }
821                         if (error)
822                                 break;
823                         cpu_mfence();
824                         wpipe->pipe_buffer.windex += space;
825                         wcount += space;
826                         continue;
827                 }
828
829                 /*
830                  * We need both the rlock and the wlock to interlock against
831                  * the EOF, WANTW, and size checks, and to modify pipe_state.
832                  *
833                  * These are token locks so we do not have to worry about
834                  * deadlocks.
835                  */
836                 lwkt_gettoken(&rlock, &wpipe->pipe_rlock);
837
838                 /*
839                  * If the "read-side" has been blocked, wake it up now
840                  * and yield to let it drain synchronously rather
841                  * then block.
842                  */
843                 if (wpipe->pipe_state & PIPE_WANTR) {
844                         wpipe->pipe_state &= ~PIPE_WANTR;
845                         wakeup(wpipe);
846                 }
847
848                 /*
849                  * don't block on non-blocking I/O
850                  */
851                 if (nbio) {
852                         lwkt_reltoken(&rlock);
853                         error = EAGAIN;
854                         break;
855                 }
856
857                 /*
858                  * re-test whether we have to block in the writer after
859                  * acquiring both locks, in case the reader opened up
860                  * some space.
861                  */
862                 space = wpipe->pipe_buffer.size -
863                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
864                 cpu_lfence();
865                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
866                         space = 0;
867
868                 /*
869                  * We have no more space and have something to offer,
870                  * wake up select/poll.
871                  */
872                 if (space == 0) {
873                         pipeselwakeup(wpipe);
874                         ++wpipe->pipe_wantwcnt;
875                         wpipe->pipe_state |= PIPE_WANTW;
876                         error = tsleep(wpipe, PCATCH, "pipewr", 0);
877                         ++pipe_wblocked_count;
878                 }
879                 lwkt_reltoken(&rlock);
880
881                 /*
882                  * Break out if we errored or the read side wants us to go
883                  * away.
884                  */
885                 if (error)
886                         break;
887                 if (wpipe->pipe_state & PIPE_WEOF) {
888                         error = EPIPE;
889                         break;
890                 }
891         }
892         pipe_end_uio(wpipe, &wpipe->pipe_wip);
893
894         /*
895          * If we have put any characters in the buffer, we wake up
896          * the reader.
897          *
898          * Both rlock and wlock are required to be able to modify pipe_state.
899          */
900         if (wpipe->pipe_buffer.windex != wpipe->pipe_buffer.rindex) {
901                 if (wpipe->pipe_state & PIPE_WANTR) {
902                         lwkt_gettoken(&rlock, &wpipe->pipe_rlock);
903                         if (wpipe->pipe_state & PIPE_WANTR) {
904                                 wpipe->pipe_state &= ~PIPE_WANTR;
905                                 lwkt_reltoken(&rlock);
906                                 wakeup(wpipe);
907                         } else {
908                                 lwkt_reltoken(&rlock);
909                         }
910                 }
911         }
912
913         /*
914          * Don't return EPIPE if I/O was successful
915          */
916         if ((wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex) &&
917             (uio->uio_resid == 0) &&
918             (error == EPIPE)) {
919                 error = 0;
920         }
921
922         if (error == 0)
923                 vfs_timestamp(&wpipe->pipe_mtime);
924
925         /*
926          * We have something to offer,
927          * wake up select/poll.
928          */
929         space = wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex;
930         lwkt_reltoken(&wlock);
931         if (space)
932                 pipeselwakeup(wpipe);
933         pipe_rel_mplock(&mpsave);
934         return (error);
935 }
936
937 /*
938  * MPALMOSTSAFE - acquires mplock
939  *
940  * we implement a very minimal set of ioctls for compatibility with sockets.
941  */
942 int
943 pipe_ioctl(struct file *fp, u_long cmd, caddr_t data, struct ucred *cred)
944 {
945         struct pipe *mpipe;
946         lwkt_tokref rlock;
947         lwkt_tokref wlock;
948         int error;
949         int mpsave;
950
951         pipe_get_mplock(&mpsave);
952         mpipe = (struct pipe *)fp->f_data;
953
954         lwkt_gettoken(&rlock, &mpipe->pipe_rlock);
955         lwkt_gettoken(&wlock, &mpipe->pipe_wlock);
956
957         switch (cmd) {
958         case FIOASYNC:
959                 if (*(int *)data) {
960                         mpipe->pipe_state |= PIPE_ASYNC;
961                 } else {
962                         mpipe->pipe_state &= ~PIPE_ASYNC;
963                 }
964                 error = 0;
965                 break;
966         case FIONREAD:
967                 *(int *)data = mpipe->pipe_buffer.windex -
968                                 mpipe->pipe_buffer.rindex;
969                 error = 0;
970                 break;
971         case FIOSETOWN:
972                 get_mplock();
973                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
974                 rel_mplock();
975                 break;
976         case FIOGETOWN:
977                 *(int *)data = fgetown(mpipe->pipe_sigio);
978                 error = 0;
979                 break;
980         case TIOCSPGRP:
981                 /* This is deprecated, FIOSETOWN should be used instead. */
982                 get_mplock();
983                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
984                 rel_mplock();
985                 break;
986
987         case TIOCGPGRP:
988                 /* This is deprecated, FIOGETOWN should be used instead. */
989                 *(int *)data = -fgetown(mpipe->pipe_sigio);
990                 error = 0;
991                 break;
992         default:
993                 error = ENOTTY;
994                 break;
995         }
996         lwkt_reltoken(&rlock);
997         lwkt_reltoken(&wlock);
998         pipe_rel_mplock(&mpsave);
999
1000         return (error);
1001 }
1002
1003 /*
1004  * MPALMOSTSAFE - acquires mplock
1005  */
1006 int
1007 pipe_poll(struct file *fp, int events, struct ucred *cred)
1008 {
1009         struct pipe *rpipe;
1010         struct pipe *wpipe;
1011         int revents = 0;
1012         u_int space;
1013         int mpsave;
1014
1015         pipe_get_mplock(&mpsave);
1016         rpipe = (struct pipe *)fp->f_data;
1017         wpipe = rpipe->pipe_peer;
1018         if (events & (POLLIN | POLLRDNORM)) {
1019                 if ((rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex) ||
1020                     (rpipe->pipe_state & PIPE_REOF)) {
1021                         revents |= events & (POLLIN | POLLRDNORM);
1022                 }
1023         }
1024
1025         if (events & (POLLOUT | POLLWRNORM)) {
1026                 if (wpipe == NULL || (wpipe->pipe_state & PIPE_WEOF)) {
1027                         revents |= events & (POLLOUT | POLLWRNORM);
1028                 } else {
1029                         space = wpipe->pipe_buffer.windex -
1030                                 wpipe->pipe_buffer.rindex;
1031                         space = wpipe->pipe_buffer.size - space;
1032                         if (space >= PIPE_BUF)
1033                                 revents |= events & (POLLOUT | POLLWRNORM);
1034                 }
1035         }
1036
1037         if ((rpipe->pipe_state & PIPE_REOF) ||
1038             (wpipe == NULL) ||
1039             (wpipe->pipe_state & PIPE_WEOF))
1040                 revents |= POLLHUP;
1041
1042         if (revents == 0) {
1043                 if (events & (POLLIN | POLLRDNORM)) {
1044                         selrecord(curthread, &rpipe->pipe_sel);
1045                         rpipe->pipe_state |= PIPE_SEL;
1046                 }
1047
1048                 if (events & (POLLOUT | POLLWRNORM)) {
1049                         selrecord(curthread, &wpipe->pipe_sel);
1050                         wpipe->pipe_state |= PIPE_SEL;
1051                 }
1052         }
1053         pipe_rel_mplock(&mpsave);
1054         return (revents);
1055 }
1056
1057 /*
1058  * MPALMOSTSAFE - acquires mplock
1059  */
1060 static int
1061 pipe_stat(struct file *fp, struct stat *ub, struct ucred *cred)
1062 {
1063         struct pipe *pipe;
1064         int mpsave;
1065
1066         pipe_get_mplock(&mpsave);
1067         pipe = (struct pipe *)fp->f_data;
1068
1069         bzero((caddr_t)ub, sizeof(*ub));
1070         ub->st_mode = S_IFIFO;
1071         ub->st_blksize = pipe->pipe_buffer.size;
1072         ub->st_size = pipe->pipe_buffer.windex - pipe->pipe_buffer.rindex;
1073         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
1074         ub->st_atimespec = pipe->pipe_atime;
1075         ub->st_mtimespec = pipe->pipe_mtime;
1076         ub->st_ctimespec = pipe->pipe_ctime;
1077         /*
1078          * Left as 0: st_dev, st_ino, st_nlink, st_uid, st_gid, st_rdev,
1079          * st_flags, st_gen.
1080          * XXX (st_dev, st_ino) should be unique.
1081          */
1082         pipe_rel_mplock(&mpsave);
1083         return (0);
1084 }
1085
1086 /*
1087  * MPALMOSTSAFE - acquires mplock
1088  */
1089 static int
1090 pipe_close(struct file *fp)
1091 {
1092         struct pipe *cpipe;
1093
1094         get_mplock();
1095         cpipe = (struct pipe *)fp->f_data;
1096         fp->f_ops = &badfileops;
1097         fp->f_data = NULL;
1098         funsetown(cpipe->pipe_sigio);
1099         pipeclose(cpipe);
1100         rel_mplock();
1101         return (0);
1102 }
1103
1104 /*
1105  * Shutdown one or both directions of a full-duplex pipe.
1106  *
1107  * MPALMOSTSAFE - acquires mplock
1108  */
1109 static int
1110 pipe_shutdown(struct file *fp, int how)
1111 {
1112         struct pipe *rpipe;
1113         struct pipe *wpipe;
1114         int error = EPIPE;
1115         lwkt_tokref rpipe_rlock;
1116         lwkt_tokref rpipe_wlock;
1117         lwkt_tokref wpipe_rlock;
1118         lwkt_tokref wpipe_wlock;
1119         int mpsave;
1120
1121         pipe_get_mplock(&mpsave);
1122         rpipe = (struct pipe *)fp->f_data;
1123         wpipe = rpipe->pipe_peer;
1124
1125         /*
1126          * We modify pipe_state on both pipes, which means we need
1127          * all four tokens!
1128          */
1129         lwkt_gettoken(&rpipe_rlock, &rpipe->pipe_rlock);
1130         lwkt_gettoken(&rpipe_wlock, &rpipe->pipe_wlock);
1131         lwkt_gettoken(&wpipe_rlock, &wpipe->pipe_rlock);
1132         lwkt_gettoken(&wpipe_wlock, &wpipe->pipe_wlock);
1133
1134         switch(how) {
1135         case SHUT_RDWR:
1136         case SHUT_RD:
1137                 rpipe->pipe_state |= PIPE_REOF;
1138                 wpipe->pipe_state |= PIPE_WEOF;
1139                 if (rpipe->pipe_state & PIPE_WANTR) {
1140                         rpipe->pipe_state &= ~PIPE_WANTR;
1141                         wakeup(rpipe);
1142                 }
1143                 if (wpipe->pipe_state & PIPE_WANTW) {
1144                         wpipe->pipe_state &= ~PIPE_WANTW;
1145                         wakeup(wpipe);
1146                 }
1147                 pipeselwakeup(rpipe);
1148                 error = 0;
1149                 if (how == SHUT_RD)
1150                         break;
1151                 /* fall through */
1152         case SHUT_WR:
1153                 wpipe->pipe_state |= PIPE_WEOF;
1154                 rpipe->pipe_state |= PIPE_REOF;
1155                 if (wpipe->pipe_state & PIPE_WANTW) {
1156                         wpipe->pipe_state &= ~PIPE_WANTW;
1157                         wakeup(wpipe);
1158                 }
1159                 if (rpipe->pipe_state & PIPE_WANTR) {
1160                         rpipe->pipe_state &= ~PIPE_WANTR;
1161                         wakeup(rpipe);
1162                 }
1163                 pipeselwakeup(wpipe);
1164                 error = 0;
1165                 break;
1166         }
1167
1168         lwkt_reltoken(&rpipe_rlock);
1169         lwkt_reltoken(&rpipe_wlock);
1170         lwkt_reltoken(&wpipe_rlock);
1171         lwkt_reltoken(&wpipe_wlock);
1172
1173         pipe_rel_mplock(&mpsave);
1174         return (error);
1175 }
1176
1177 static void
1178 pipe_free_kmem(struct pipe *cpipe)
1179 {
1180         if (cpipe->pipe_buffer.buffer != NULL) {
1181                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
1182                         atomic_subtract_int(&pipe_nbig, 1);
1183                 kmem_free(&kernel_map,
1184                         (vm_offset_t)cpipe->pipe_buffer.buffer,
1185                         cpipe->pipe_buffer.size);
1186                 cpipe->pipe_buffer.buffer = NULL;
1187                 cpipe->pipe_buffer.object = NULL;
1188         }
1189 }
1190
1191 /*
1192  * Close the pipe.  The slock must be held to interlock against simultanious
1193  * closes.  The rlock and wlock must be held to adjust the pipe_state.
1194  */
1195 static void
1196 pipeclose(struct pipe *cpipe)
1197 {
1198         globaldata_t gd;
1199         struct pipe *ppipe;
1200         lwkt_tokref cpipe_rlock;
1201         lwkt_tokref cpipe_wlock;
1202         lwkt_tokref ppipe_rlock;
1203         lwkt_tokref ppipe_wlock;
1204
1205         if (cpipe == NULL)
1206                 return;
1207
1208         /*
1209          * The slock may not have been allocated yet (close during
1210          * initialization)
1211          *
1212          * We need both the read and write tokens to modify pipe_state.
1213          */
1214         if (cpipe->pipe_slock)
1215                 lockmgr(cpipe->pipe_slock, LK_EXCLUSIVE);
1216         lwkt_gettoken(&cpipe_rlock, &cpipe->pipe_rlock);
1217         lwkt_gettoken(&cpipe_wlock, &cpipe->pipe_wlock);
1218
1219         /*
1220          * Set our state, wakeup anyone waiting in select, and
1221          * wakeup anyone blocked on our pipe.
1222          */
1223         cpipe->pipe_state |= PIPE_CLOSED | PIPE_REOF | PIPE_WEOF;
1224         pipeselwakeup(cpipe);
1225         if (cpipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1226                 cpipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1227                 wakeup(cpipe);
1228         }
1229
1230         /*
1231          * Disconnect from peer
1232          */
1233         if ((ppipe = cpipe->pipe_peer) != NULL) {
1234                 lwkt_gettoken(&ppipe_rlock, &ppipe->pipe_rlock);
1235                 lwkt_gettoken(&ppipe_wlock, &ppipe->pipe_wlock);
1236                 ppipe->pipe_state |= PIPE_REOF;
1237                 pipeselwakeup(ppipe);
1238                 if (ppipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1239                         ppipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1240                         wakeup(ppipe);
1241                 }
1242                 if (SLIST_FIRST(&ppipe->pipe_sel.si_note)) {
1243                         get_mplock();
1244                         KNOTE(&ppipe->pipe_sel.si_note, 0);
1245                         rel_mplock();
1246                 }
1247                 lwkt_reltoken(&ppipe_rlock);
1248                 lwkt_reltoken(&ppipe_wlock);
1249         }
1250
1251         /*
1252          * If the peer is also closed we can free resources for both
1253          * sides, otherwise we leave our side intact to deal with any
1254          * races (since we only have the slock).
1255          */
1256         if (ppipe && (ppipe->pipe_state & PIPE_CLOSED)) {
1257                 cpipe->pipe_peer = NULL;
1258                 ppipe->pipe_peer = NULL;
1259                 ppipe->pipe_slock = NULL;       /* we will free the slock */
1260                 pipeclose(ppipe);
1261                 ppipe = NULL;
1262         }
1263
1264         lwkt_reltoken(&cpipe_rlock);
1265         lwkt_reltoken(&cpipe_wlock);
1266         if (cpipe->pipe_slock)
1267                 lockmgr(cpipe->pipe_slock, LK_RELEASE);
1268
1269         /*
1270          * If we disassociated from our peer we can free resources
1271          */
1272         if (ppipe == NULL) {
1273                 gd = mycpu;
1274                 if (cpipe->pipe_slock) {
1275                         kfree(cpipe->pipe_slock, M_PIPE);
1276                         cpipe->pipe_slock = NULL;
1277                 }
1278                 if (gd->gd_pipeqcount >= pipe_maxcache ||
1279                     cpipe->pipe_buffer.size != PIPE_SIZE
1280                 ) {
1281                         pipe_free_kmem(cpipe);
1282                         kfree(cpipe, M_PIPE);
1283                 } else {
1284                         cpipe->pipe_state = 0;
1285                         cpipe->pipe_peer = gd->gd_pipeq;
1286                         gd->gd_pipeq = cpipe;
1287                         ++gd->gd_pipeqcount;
1288                 }
1289         }
1290 }
1291
1292 /*
1293  * MPALMOSTSAFE - acquires mplock
1294  */
1295 static int
1296 pipe_kqfilter(struct file *fp, struct knote *kn)
1297 {
1298         struct pipe *cpipe;
1299
1300         get_mplock();
1301         cpipe = (struct pipe *)kn->kn_fp->f_data;
1302
1303         switch (kn->kn_filter) {
1304         case EVFILT_READ:
1305                 kn->kn_fop = &pipe_rfiltops;
1306                 break;
1307         case EVFILT_WRITE:
1308                 kn->kn_fop = &pipe_wfiltops;
1309                 cpipe = cpipe->pipe_peer;
1310                 if (cpipe == NULL) {
1311                         /* other end of pipe has been closed */
1312                         rel_mplock();
1313                         return (EPIPE);
1314                 }
1315                 break;
1316         default:
1317                 return (1);
1318         }
1319         kn->kn_hook = (caddr_t)cpipe;
1320
1321         SLIST_INSERT_HEAD(&cpipe->pipe_sel.si_note, kn, kn_selnext);
1322         rel_mplock();
1323         return (0);
1324 }
1325
1326 static void
1327 filt_pipedetach(struct knote *kn)
1328 {
1329         struct pipe *cpipe = (struct pipe *)kn->kn_hook;
1330
1331         SLIST_REMOVE(&cpipe->pipe_sel.si_note, kn, knote, kn_selnext);
1332 }
1333
1334 /*ARGSUSED*/
1335 static int
1336 filt_piperead(struct knote *kn, long hint)
1337 {
1338         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1339
1340         kn->kn_data = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
1341
1342         /* XXX RACE */
1343         if (rpipe->pipe_state & PIPE_REOF) {
1344                 kn->kn_flags |= EV_EOF; 
1345                 return (1);
1346         }
1347         return (kn->kn_data > 0);
1348 }
1349
1350 /*ARGSUSED*/
1351 static int
1352 filt_pipewrite(struct knote *kn, long hint)
1353 {
1354         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1355         struct pipe *wpipe = rpipe->pipe_peer;
1356         u_int32_t space;
1357
1358         /* XXX RACE */
1359         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_WEOF)) {
1360                 kn->kn_data = 0;
1361                 kn->kn_flags |= EV_EOF; 
1362                 return (1);
1363         }
1364         space = wpipe->pipe_buffer.windex -
1365                 wpipe->pipe_buffer.rindex;
1366         space = wpipe->pipe_buffer.size - space;
1367         kn->kn_data = space;
1368         return (kn->kn_data >= PIPE_BUF);
1369 }