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  */
  21
  22 /*
  23  * This file contains a high-performance replacement for the socket-based
  24  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
  25  * all features of sockets, but does do everything that pipes normally
  26  * do.
  27  */
  28 #include <sys/param.h>
  29 #include <sys/systm.h>
  30 #include <sys/kernel.h>
  31 #include <sys/proc.h>
  32 #include <sys/fcntl.h>
  33 #include <sys/file.h>
  34 #include <sys/filedesc.h>
  35 #include <sys/filio.h>
  36 #include <sys/ttycom.h>
  37 #include <sys/stat.h>
  38 #include <sys/signalvar.h>
  39 #include <sys/sysproto.h>
  40 #include <sys/pipe.h>
  41 #include <sys/vnode.h>
  42 #include <sys/uio.h>
  43 #include <sys/event.h>
  44 #include <sys/globaldata.h>
  45 #include <sys/module.h>
  46 #include <sys/malloc.h>
  47 #include <sys/sysctl.h>
  48 #include <sys/socket.h>
  49
  50 #include <vm/vm.h>
  51 #include <vm/vm_param.h>
  52 #include <sys/lock.h>
  53 #include <vm/vm_object.h>
  54 #include <vm/vm_kern.h>
  55 #include <vm/vm_extern.h>
  56 #include <vm/pmap.h>
  57 #include <vm/vm_map.h>
  58 #include <vm/vm_page.h>
  59 #include <vm/vm_zone.h>
  60
  61 #include <sys/file2.h>
  62 #include <sys/signal2.h>
  63
  64 #include <machine/cpufunc.h>
  65
  66 /*
  67  * interfaces to the outside world
  68  */
  69 static int pipe_read (struct file *fp, struct uio *uio,
  70                 struct ucred *cred, int flags);
  71 static int pipe_write (struct file *fp, struct uio *uio,
  72                 struct ucred *cred, int flags);
  73 static int pipe_close (struct file *fp);
  74 static int pipe_shutdown (struct file *fp, int how);
  75 static int pipe_kqfilter (struct file *fp, struct knote *kn);
  76 static int pipe_stat (struct file *fp, struct stat *sb, struct ucred *cred);
  77 static int pipe_ioctl (struct file *fp, u_long cmd, caddr_t data,
  78                 struct ucred *cred, struct sysmsg *msg);
  79
  80 static struct fileops pipeops = {
  81         .fo_read = pipe_read,
  82         .fo_write = pipe_write,
  83         .fo_ioctl = pipe_ioctl,
  84         .fo_kqfilter = pipe_kqfilter,
  85         .fo_stat = pipe_stat,
  86         .fo_close = pipe_close,
  87         .fo_shutdown = pipe_shutdown
  88 };
  89
  90 static void     filt_pipedetach(struct knote *kn);
  91 static int      filt_piperead(struct knote *kn, long hint);
  92 static int      filt_pipewrite(struct knote *kn, long hint);
  93
  94 static struct filterops pipe_rfiltops =
  95         { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_pipedetach, filt_piperead };
  96 static struct filterops pipe_wfiltops =
  97         { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_pipedetach, filt_pipewrite };
  98
  99 MALLOC_DEFINE(M_PIPE, "pipe", "pipe structures");
 100
 101 /*
 102  * Default pipe buffer size(s), this can be kind-of large now because pipe
 103  * space is pageable.  The pipe code will try to maintain locality of
 104  * reference for performance reasons, so small amounts of outstanding I/O
 105  * will not wipe the cache.
 106  */
 107 #define MINPIPESIZE (PIPE_SIZE/3)
 108 #define MAXPIPESIZE (2*PIPE_SIZE/3)
 109
 110 /*
 111  * Limit the number of "big" pipes
 112  */
 113 #define LIMITBIGPIPES   64
 114 #define PIPEQ_MAX_CACHE 16      /* per-cpu pipe structure cache */
 115
 116 static int pipe_maxbig = LIMITBIGPIPES;
 117 static int pipe_maxcache = PIPEQ_MAX_CACHE;
 118 static int pipe_bigcount;
 119 static int pipe_nbig;
 120 static int pipe_bcache_alloc;
 121 static int pipe_bkmem_alloc;
 122 static int pipe_rblocked_count;
 123 static int pipe_wblocked_count;
 124
 125 SYSCTL_NODE(_kern, OID_AUTO, pipe, CTLFLAG_RW, 0, "Pipe operation");
 126 SYSCTL_INT(_kern_pipe, OID_AUTO, nbig,
 127         CTLFLAG_RD, &pipe_nbig, 0, "number of big pipes allocated");
 128 SYSCTL_INT(_kern_pipe, OID_AUTO, bigcount,
 129         CTLFLAG_RW, &pipe_bigcount, 0, "number of times pipe expanded");
 130 SYSCTL_INT(_kern_pipe, OID_AUTO, rblocked,
 131         CTLFLAG_RW, &pipe_rblocked_count, 0, "number of times pipe expanded");
 132 SYSCTL_INT(_kern_pipe, OID_AUTO, wblocked,
 133         CTLFLAG_RW, &pipe_wblocked_count, 0, "number of times pipe expanded");
 134 SYSCTL_INT(_kern_pipe, OID_AUTO, maxcache,
 135         CTLFLAG_RW, &pipe_maxcache, 0, "max pipes cached per-cpu");
 136 SYSCTL_INT(_kern_pipe, OID_AUTO, maxbig,
 137         CTLFLAG_RW, &pipe_maxbig, 0, "max number of big pipes");
 138 static int pipe_delay = 5000;   /* 5uS default */
 139 SYSCTL_INT(_kern_pipe, OID_AUTO, delay,
 140         CTLFLAG_RW, &pipe_delay, 0, "SMP delay optimization in ns");
 141 #if !defined(NO_PIPE_SYSCTL_STATS)
 142 SYSCTL_INT(_kern_pipe, OID_AUTO, bcache_alloc,
 143         CTLFLAG_RW, &pipe_bcache_alloc, 0, "pipe buffer from pcpu cache");
 144 SYSCTL_INT(_kern_pipe, OID_AUTO, bkmem_alloc,
 145         CTLFLAG_RW, &pipe_bkmem_alloc, 0, "pipe buffer from kmem");
 146 #endif
 147
 148 /*
 149  * Auto-size pipe cache to reduce kmem allocations and frees.
 150  */
 151 static
 152 void
 153 pipeinit(void *dummy)
 154 {
 155         size_t mbytes = kmem_lim_size();
 156
 157         if (pipe_maxbig == LIMITBIGPIPES) {
 158                 if (mbytes >= 7 * 1024)
 159                         pipe_maxbig *= 2;
 160                 if (mbytes >= 15 * 1024)
 161                         pipe_maxbig *= 2;
 162         }
 163         if (pipe_maxcache == PIPEQ_MAX_CACHE) {
 164                 if (mbytes >= 7 * 1024)
 165                         pipe_maxcache *= 2;
 166                 if (mbytes >= 15 * 1024)
 167                         pipe_maxcache *= 2;
 168         }
 169 }
 170 SYSINIT(kmem, SI_BOOT2_MACHDEP, SI_ORDER_ANY, pipeinit, NULL)
 171
 172 static void pipeclose (struct pipe *cpipe);
 173 static void pipe_free_kmem (struct pipe *cpipe);
 174 static int pipe_create (struct pipe **cpipep);
 175 static int pipespace (struct pipe *cpipe, int size);
 176
 177 static __inline void
 178 pipewakeup(struct pipe *cpipe, int dosigio)
 179 {
 180         if (dosigio && (cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio) {
 181                 lwkt_gettoken(&sigio_token);
 182                 pgsigio(cpipe->pipe_sigio, SIGIO, 0);
 183                 lwkt_reltoken(&sigio_token);
 184         }
 185         KNOTE(&cpipe->pipe_kq.ki_note, 0);
 186 }
 187
 188 /*
 189  * These routines are called before and after a UIO.  The UIO
 190  * may block, causing our held tokens to be lost temporarily.
 191  *
 192  * We use these routines to serialize reads against other reads
 193  * and writes against other writes.
 194  *
 195  * The read token is held on entry so *ipp does not race.
 196  */
 197 static __inline int
 198 pipe_start_uio(struct pipe *cpipe, int *ipp)
 199 {
 200         int error;
 201
 202         while (*ipp) {
 203                 *ipp = -1;
 204                 error = tsleep(ipp, PCATCH, "pipexx", 0);
 205                 if (error)
 206                         return (error);
 207         }
 208         *ipp = 1;
 209         return (0);
 210 }
 211
 212 static __inline void
 213 pipe_end_uio(struct pipe *cpipe, int *ipp)
 214 {
 215         if (*ipp < 0) {
 216                 *ipp = 0;
 217                 wakeup(ipp);
 218         } else {
 219                 KKASSERT(*ipp > 0);
 220                 *ipp = 0;
 221         }
 222 }
 223
 224 /*
 225  * The pipe system call for the DTYPE_PIPE type of pipes
 226  *
 227  * pipe_args(int dummy)
 228  *
 229  * MPSAFE
 230  */
 231 int
 232 sys_pipe(struct pipe_args *uap)
 233 {
 234         struct thread *td = curthread;
 235         struct filedesc *fdp = td->td_proc->p_fd;
 236         struct file *rf, *wf;
 237         struct pipe *rpipe, *wpipe;
 238         int fd1, fd2, error;
 239
 240         rpipe = wpipe = NULL;
 241         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
 242                 pipeclose(rpipe);
 243                 pipeclose(wpipe);
 244                 return (ENFILE);
 245         }
 246
 247         error = falloc(td->td_lwp, &rf, &fd1);
 248         if (error) {
 249                 pipeclose(rpipe);
 250                 pipeclose(wpipe);
 251                 return (error);
 252         }
 253         uap->sysmsg_fds[0] = fd1;
 254
 255         /*
 256          * Warning: once we've gotten past allocation of the fd for the
 257          * read-side, we can only drop the read side via fdrop() in order
 258          * to avoid races against processes which manage to dup() the read
 259          * side while we are blocked trying to allocate the write side.
 260          */
 261         rf->f_type = DTYPE_PIPE;
 262         rf->f_flag = FREAD | FWRITE;
 263         rf->f_ops = &pipeops;
 264         rf->f_data = rpipe;
 265         error = falloc(td->td_lwp, &wf, &fd2);
 266         if (error) {
 267                 fsetfd(fdp, NULL, fd1);
 268                 fdrop(rf);
 269                 /* rpipe has been closed by fdrop(). */
 270                 pipeclose(wpipe);
 271                 return (error);
 272         }
 273         wf->f_type = DTYPE_PIPE;
 274         wf->f_flag = FREAD | FWRITE;
 275         wf->f_ops = &pipeops;
 276         wf->f_data = wpipe;
 277         uap->sysmsg_fds[1] = fd2;
 278
 279         rpipe->pipe_slock = kmalloc(sizeof(struct lock),
 280                                     M_PIPE, M_WAITOK|M_ZERO);
 281         wpipe->pipe_slock = rpipe->pipe_slock;
 282         rpipe->pipe_peer = wpipe;
 283         wpipe->pipe_peer = rpipe;
 284         lockinit(rpipe->pipe_slock, "pipecl", 0, 0);
 285
 286         /*
 287          * Once activated the peer relationship remains valid until
 288          * both sides are closed.
 289          */
 290         fsetfd(fdp, rf, fd1);
 291         fsetfd(fdp, wf, fd2);
 292         fdrop(rf);
 293         fdrop(wf);
 294
 295         return (0);
 296 }
 297
 298 /*
 299  * Allocate kva for pipe circular buffer, the space is pageable
 300  * This routine will 'realloc' the size of a pipe safely, if it fails
 301  * it will retain the old buffer.
 302  * If it fails it will return ENOMEM.
 303  */
 304 static int
 305 pipespace(struct pipe *cpipe, int size)
 306 {
 307         struct vm_object *object;
 308         caddr_t buffer;
 309         int npages, error;
 310
 311         npages = round_page(size) / PAGE_SIZE;
 312         object = cpipe->pipe_buffer.object;
 313
 314         /*
 315          * [re]create the object if necessary and reserve space for it
 316          * in the kernel_map.  The object and memory are pageable.  On
 317          * success, free the old resources before assigning the new
 318          * ones.
 319          */
 320         if (object == NULL || object->size != npages) {
 321                 object = vm_object_allocate(OBJT_DEFAULT, npages);
 322                 buffer = (caddr_t)vm_map_min(&kernel_map);
 323
 324                 error = vm_map_find(&kernel_map, object, 0,
 325                                     (vm_offset_t *)&buffer,
 326                                     size, PAGE_SIZE,
 327                                     1, VM_MAPTYPE_NORMAL,
 328                                     VM_PROT_ALL, VM_PROT_ALL,
 329                                     0);
 330
 331                 if (error != KERN_SUCCESS) {
 332                         vm_object_deallocate(object);
 333                         return (ENOMEM);
 334                 }
 335                 pipe_free_kmem(cpipe);
 336                 cpipe->pipe_buffer.object = object;
 337                 cpipe->pipe_buffer.buffer = buffer;
 338                 cpipe->pipe_buffer.size = size;
 339                 ++pipe_bkmem_alloc;
 340         } else {
 341                 ++pipe_bcache_alloc;
 342         }
 343         cpipe->pipe_buffer.rindex = 0;
 344         cpipe->pipe_buffer.windex = 0;
 345         return (0);
 346 }
 347
 348 /*
 349  * Initialize and allocate VM and memory for pipe, pulling the pipe from
 350  * our per-cpu cache if possible.  For now make sure it is sized for the
 351  * smaller PIPE_SIZE default.
 352  */
 353 static int
 354 pipe_create(struct pipe **cpipep)
 355 {
 356         globaldata_t gd = mycpu;
 357         struct pipe *cpipe;
 358         int error;
 359
 360         if ((cpipe = gd->gd_pipeq) != NULL) {
 361                 gd->gd_pipeq = cpipe->pipe_peer;
 362                 --gd->gd_pipeqcount;
 363                 cpipe->pipe_peer = NULL;
 364                 cpipe->pipe_wantwcnt = 0;
 365         } else {
 366                 cpipe = kmalloc(sizeof(struct pipe), M_PIPE, M_WAITOK|M_ZERO);
 367         }
 368         *cpipep = cpipe;
 369         if ((error = pipespace(cpipe, PIPE_SIZE)) != 0)
 370                 return (error);
 371         vfs_timestamp(&cpipe->pipe_ctime);
 372         cpipe->pipe_atime = cpipe->pipe_ctime;
 373         cpipe->pipe_mtime = cpipe->pipe_ctime;
 374         lwkt_token_init(&cpipe->pipe_rlock, "piper");
 375         lwkt_token_init(&cpipe->pipe_wlock, "pipew");
 376         return (0);
 377 }
 378
 379 static int
 380 pipe_read(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 381 {
 382         struct pipe *rpipe;
 383         struct pipe *wpipe;
 384         int error;
 385         size_t nread = 0;
 386         int nbio;
 387         u_int size;     /* total bytes available */
 388         u_int nsize;    /* total bytes to read */
 389         u_int rindex;   /* contiguous bytes available */
 390         int notify_writer;
 391         int bigread;
 392         int bigcount;
 393
 394         atomic_set_int(&curthread->td_mpflags, TDF_MP_BATCH_DEMARC);
 395
 396         if (uio->uio_resid == 0)
 397                 return(0);
 398
 399         /*
 400          * Setup locks, calculate nbio
 401          */
 402         rpipe = (struct pipe *)fp->f_data;
 403         wpipe = rpipe->pipe_peer;
 404         lwkt_gettoken(&rpipe->pipe_rlock);
 405
 406         if (fflags & O_FBLOCKING)
 407                 nbio = 0;
 408         else if (fflags & O_FNONBLOCKING)
 409                 nbio = 1;
 410         else if (fp->f_flag & O_NONBLOCK)
 411                 nbio = 1;
 412         else
 413                 nbio = 0;
 414
 415         /*
 416          * Reads are serialized.  Note however that pipe_buffer.buffer and
 417          * pipe_buffer.size can change out from under us when the number
 418          * of bytes in the buffer are zero due to the write-side doing a
 419          * pipespace().
 420          */
 421         error = pipe_start_uio(rpipe, &rpipe->pipe_rip);
 422         if (error) {
 423                 lwkt_reltoken(&rpipe->pipe_rlock);
 424                 return (error);
 425         }
 426         notify_writer = 0;
 427
 428         bigread = (uio->uio_resid > 10 * 1024 * 1024);
 429         bigcount = 10;
 430
 431         while (uio->uio_resid) {
 432                 /*
 433                  * Don't hog the cpu.
 434                  */
 435                 if (bigread && --bigcount == 0) {
 436                         lwkt_user_yield();
 437                         bigcount = 10;
 438                         if (CURSIG(curthread->td_lwp)) {
 439                                 error = EINTR;
 440                                 break;
 441                         }
 442                 }
 443
 444                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 445                 cpu_lfence();
 446                 if (size) {
 447                         rindex = rpipe->pipe_buffer.rindex &
 448                                  (rpipe->pipe_buffer.size - 1);
 449                         nsize = size;
 450                         if (nsize > rpipe->pipe_buffer.size - rindex)
 451                                 nsize = rpipe->pipe_buffer.size - rindex;
 452                         nsize = szmin(nsize, uio->uio_resid);
 453
 454                         error = uiomove(&rpipe->pipe_buffer.buffer[rindex],
 455                                         nsize, uio);
 456                         if (error)
 457                                 break;
 458                         cpu_mfence();
 459                         rpipe->pipe_buffer.rindex += nsize;
 460                         nread += nsize;
 461
 462                         /*
 463                          * If the FIFO is still over half full just continue
 464                          * and do not try to notify the writer yet.
 465                          */
 466                         if (size - nsize >= (rpipe->pipe_buffer.size >> 1)) {
 467                                 notify_writer = 0;
 468                                 continue;
 469                         }
 470
 471                         /*
 472                          * When the FIFO is less then half full notify any
 473                          * waiting writer.  WANTW can be checked while
 474                          * holding just the rlock.
 475                          */
 476                         notify_writer = 1;
 477                         if ((rpipe->pipe_state & PIPE_WANTW) == 0)
 478                                 continue;
 479                 }
 480
 481                 /*
 482                  * If the "write-side" was blocked we wake it up.  This code
 483                  * is reached either when the buffer is completely emptied
 484                  * or if it becomes more then half-empty.
 485                  *
 486                  * Pipe_state can only be modified if both the rlock and
 487                  * wlock are held.
 488                  */
 489                 if (rpipe->pipe_state & PIPE_WANTW) {
 490                         lwkt_gettoken(&rpipe->pipe_wlock);
 491                         if (rpipe->pipe_state & PIPE_WANTW) {
 492                                 rpipe->pipe_state &= ~PIPE_WANTW;
 493                                 lwkt_reltoken(&rpipe->pipe_wlock);
 494                                 wakeup(rpipe);
 495                         } else {
 496                                 lwkt_reltoken(&rpipe->pipe_wlock);
 497                         }
 498                 }
 499
 500                 /*
 501                  * Pick up our copy loop again if the writer sent data to
 502                  * us while we were messing around.
 503                  *
 504                  * On a SMP box poll up to pipe_delay nanoseconds for new
 505                  * data.  Typically a value of 2000 to 4000 is sufficient
 506                  * to eradicate most IPIs/tsleeps/wakeups when a pipe
 507                  * is used for synchronous communications with small packets,
 508                  * and 8000 or so (8uS) will pipeline large buffer xfers
 509                  * between cpus over a pipe.
 510                  *
 511                  * For synchronous communications a hit means doing a
 512                  * full Awrite-Bread-Bwrite-Aread cycle in less then 2uS,
 513                  * where as miss requiring a tsleep/wakeup sequence
 514                  * will take 7uS or more.
 515                  */
 516                 if (rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex)
 517                         continue;
 518
 519 #ifdef _RDTSC_SUPPORTED_
 520                 if (pipe_delay) {
 521                         int64_t tsc_target;
 522                         int good = 0;
 523
 524                         tsc_target = tsc_get_target(pipe_delay);
 525                         while (tsc_test_target(tsc_target) == 0) {
 526                                 if (rpipe->pipe_buffer.windex !=
 527                                     rpipe->pipe_buffer.rindex) {
 528                                         good = 1;
 529                                         break;
 530                                 }
 531                         }
 532                         if (good)
 533                                 continue;
 534                 }
 535 #endif
 536
 537                 /*
 538                  * Detect EOF condition, do not set error.
 539                  */
 540                 if (rpipe->pipe_state & PIPE_REOF)
 541                         break;
 542
 543                 /*
 544                  * Break if some data was read, or if this was a non-blocking
 545                  * read.
 546                  */
 547                 if (nread > 0)
 548                         break;
 549
 550                 if (nbio) {
 551                         error = EAGAIN;
 552                         break;
 553                 }
 554
 555                 /*
 556                  * Last chance, interlock with WANTR.
 557                  */
 558                 lwkt_gettoken(&rpipe->pipe_wlock);
 559                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 560                 if (size) {
 561                         lwkt_reltoken(&rpipe->pipe_wlock);
 562                         continue;
 563                 }
 564
 565                 /*
 566                  * Retest EOF - acquiring a new token can temporarily release
 567                  * tokens already held.
 568                  */
 569                 if (rpipe->pipe_state & PIPE_REOF) {
 570                         lwkt_reltoken(&rpipe->pipe_wlock);
 571                         break;
 572                 }
 573
 574                 /*
 575                  * If there is no more to read in the pipe, reset its
 576                  * pointers to the beginning.  This improves cache hit
 577                  * stats.
 578                  *
 579                  * We need both locks to modify both pointers, and there
 580                  * must also not be a write in progress or the uiomove()
 581                  * in the write might block and temporarily release
 582                  * its wlock, then reacquire and update windex.  We are
 583                  * only serialized against reads, not writes.
 584                  *
 585                  * XXX should we even bother resetting the indices?  It
 586                  *     might actually be more cache efficient not to.
 587                  */
 588                 if (rpipe->pipe_buffer.rindex == rpipe->pipe_buffer.windex &&
 589                     rpipe->pipe_wip == 0) {
 590                         rpipe->pipe_buffer.rindex = 0;
 591                         rpipe->pipe_buffer.windex = 0;
 592                 }
 593
 594                 /*
 595                  * Wait for more data.
 596                  *
 597                  * Pipe_state can only be set if both the rlock and wlock
 598                  * are held.
 599                  */
 600                 rpipe->pipe_state |= PIPE_WANTR;
 601                 tsleep_interlock(rpipe, PCATCH);
 602                 lwkt_reltoken(&rpipe->pipe_wlock);
 603                 error = tsleep(rpipe, PCATCH | PINTERLOCKED, "piperd", 0);
 604                 ++pipe_rblocked_count;
 605                 if (error)
 606                         break;
 607         }
 608         pipe_end_uio(rpipe, &rpipe->pipe_rip);
 609
 610         /*
 611          * Uptime last access time
 612          */
 613         if (error == 0 && nread)
 614                 vfs_timestamp(&rpipe->pipe_atime);
 615
 616         /*
 617          * If we drained the FIFO more then half way then handle
 618          * write blocking hysteresis.
 619          *
 620          * Note that PIPE_WANTW cannot be set by the writer without
 621          * it holding both rlock and wlock, so we can test it
 622          * while holding just rlock.
 623          */
 624         if (notify_writer) {
 625                 /*
 626                  * Synchronous blocking is done on the pipe involved
 627                  */
 628                 if (rpipe->pipe_state & PIPE_WANTW) {
 629                         lwkt_gettoken(&rpipe->pipe_wlock);
 630                         if (rpipe->pipe_state & PIPE_WANTW) {
 631                                 rpipe->pipe_state &= ~PIPE_WANTW;
 632                                 lwkt_reltoken(&rpipe->pipe_wlock);
 633                                 wakeup(rpipe);
 634                         } else {
 635                                 lwkt_reltoken(&rpipe->pipe_wlock);
 636                         }
 637                 }
 638
 639                 /*
 640                  * But we may also have to deal with a kqueue which is
 641                  * stored on the same pipe as its descriptor, so a
 642                  * EVFILT_WRITE event waiting for our side to drain will
 643                  * be on the other side.
 644                  */
 645                 lwkt_gettoken(&wpipe->pipe_wlock);
 646                 pipewakeup(wpipe, 0);
 647                 lwkt_reltoken(&wpipe->pipe_wlock);
 648         }
 649         /*size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;*/
 650         lwkt_reltoken(&rpipe->pipe_rlock);
 651
 652         return (error);
 653 }
 654
 655 static int
 656 pipe_write(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 657 {
 658         int error;
 659         int orig_resid;
 660         int nbio;
 661         struct pipe *wpipe;
 662         struct pipe *rpipe;
 663         u_int windex;
 664         u_int space;
 665         u_int wcount;
 666         int bigwrite;
 667         int bigcount;
 668
 669         /*
 670          * Writes go to the peer.  The peer will always exist.
 671          */
 672         rpipe = (struct pipe *) fp->f_data;
 673         wpipe = rpipe->pipe_peer;
 674         lwkt_gettoken(&wpipe->pipe_wlock);
 675         if (wpipe->pipe_state & PIPE_WEOF) {
 676                 lwkt_reltoken(&wpipe->pipe_wlock);
 677                 return (EPIPE);
 678         }
 679
 680         /*
 681          * Degenerate case (EPIPE takes prec)
 682          */
 683         if (uio->uio_resid == 0) {
 684                 lwkt_reltoken(&wpipe->pipe_wlock);
 685                 return(0);
 686         }
 687
 688         /*
 689          * Writes are serialized (start_uio must be called with wlock)
 690          */
 691         error = pipe_start_uio(wpipe, &wpipe->pipe_wip);
 692         if (error) {
 693                 lwkt_reltoken(&wpipe->pipe_wlock);
 694                 return (error);
 695         }
 696
 697         if (fflags & O_FBLOCKING)
 698                 nbio = 0;
 699         else if (fflags & O_FNONBLOCKING)
 700                 nbio = 1;
 701         else if (fp->f_flag & O_NONBLOCK)
 702                 nbio = 1;
 703         else
 704                 nbio = 0;
 705
 706         /*
 707          * If it is advantageous to resize the pipe buffer, do
 708          * so.  We are write-serialized so we can block safely.
 709          */
 710         if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 711             (pipe_nbig < pipe_maxbig) &&
 712             wpipe->pipe_wantwcnt > 4 &&
 713             (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 714                 /*
 715                  * Recheck after lock.
 716                  */
 717                 lwkt_gettoken(&wpipe->pipe_rlock);
 718                 if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 719                     (pipe_nbig < pipe_maxbig) &&
 720                     (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 721                         atomic_add_int(&pipe_nbig, 1);
 722                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
 723                                 ++pipe_bigcount;
 724                         else
 725                                 atomic_subtract_int(&pipe_nbig, 1);
 726                 }
 727                 lwkt_reltoken(&wpipe->pipe_rlock);
 728         }
 729
 730         orig_resid = uio->uio_resid;
 731         wcount = 0;
 732
 733         bigwrite = (uio->uio_resid > 10 * 1024 * 1024);
 734         bigcount = 10;
 735
 736         while (uio->uio_resid) {
 737                 if (wpipe->pipe_state & PIPE_WEOF) {
 738                         error = EPIPE;
 739                         break;
 740                 }
 741
 742                 /*
 743                  * Don't hog the cpu.
 744                  */
 745                 if (bigwrite && --bigcount == 0) {
 746                         lwkt_user_yield();
 747                         bigcount = 10;
 748                         if (CURSIG(curthread->td_lwp)) {
 749                                 error = EINTR;
 750                                 break;
 751                         }
 752                 }
 753
 754                 windex = wpipe->pipe_buffer.windex &
 755                          (wpipe->pipe_buffer.size - 1);
 756                 space = wpipe->pipe_buffer.size -
 757                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 758                 cpu_lfence();
 759
 760                 /* Writes of size <= PIPE_BUF must be atomic. */
 761                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 762                         space = 0;
 763
 764                 /*
 765                  * Write to fill, read size handles write hysteresis.  Also
 766                  * additional restrictions can cause select-based non-blocking
 767                  * writes to spin.
 768                  */
 769                 if (space > 0) {
 770                         u_int segsize;
 771
 772                         /*
 773                          * Transfer size is minimum of uio transfer
 774                          * and free space in pipe buffer.
 775                          *
 776                          * Limit each uiocopy to no more then PIPE_SIZE
 777                          * so we can keep the gravy train going on a
 778                          * SMP box.  This doubles the performance for
 779                          * write sizes > 16K.  Otherwise large writes
 780                          * wind up doing an inefficient synchronous
 781                          * ping-pong.
 782                          */
 783                         space = szmin(space, uio->uio_resid);
 784                         if (space > PIPE_SIZE)
 785                                 space = PIPE_SIZE;
 786
 787                         /*
 788                          * First segment to transfer is minimum of
 789                          * transfer size and contiguous space in
 790                          * pipe buffer.  If first segment to transfer
 791                          * is less than the transfer size, we've got
 792                          * a wraparound in the buffer.
 793                          */
 794                         segsize = wpipe->pipe_buffer.size - windex;
 795                         if (segsize > space)
 796                                 segsize = space;
 797
 798                         /*
 799                          * If this is the first loop and the reader is
 800                          * blocked, do a preemptive wakeup of the reader.
 801                          *
 802                          * On SMP the IPI latency plus the wlock interlock
 803                          * on the reader side is the fastest way to get the
 804                          * reader going.  (The scheduler will hard loop on
 805                          * lock tokens).
 806                          *
 807                          * NOTE: We can't clear WANTR here without acquiring
 808                          * the rlock, which we don't want to do here!
 809                          */
 810                         if ((wpipe->pipe_state & PIPE_WANTR))
 811                                 wakeup(wpipe);
 812
 813                         /*
 814                          * Transfer segment, which may include a wrap-around.
 815                          * Update windex to account for both all in one go
 816                          * so the reader can read() the data atomically.
 817                          */
 818                         error = uiomove(&wpipe->pipe_buffer.buffer[windex],
 819                                         segsize, uio);
 820                         if (error == 0 && segsize < space) {
 821                                 segsize = space - segsize;
 822                                 error = uiomove(&wpipe->pipe_buffer.buffer[0],
 823                                                 segsize, uio);
 824                         }
 825                         if (error)
 826                                 break;
 827                         cpu_mfence();
 828                         wpipe->pipe_buffer.windex += space;
 829                         wcount += space;
 830                         continue;
 831                 }
 832
 833                 /*
 834                  * We need both the rlock and the wlock to interlock against
 835                  * the EOF, WANTW, and size checks, and to modify pipe_state.
 836                  *
 837                  * These are token locks so we do not have to worry about
 838                  * deadlocks.
 839                  */
 840                 lwkt_gettoken(&wpipe->pipe_rlock);
 841
 842                 /*
 843                  * If the "read-side" has been blocked, wake it up now
 844                  * and yield to let it drain synchronously rather
 845                  * then block.
 846                  */
 847                 if (wpipe->pipe_state & PIPE_WANTR) {
 848                         wpipe->pipe_state &= ~PIPE_WANTR;
 849                         wakeup(wpipe);
 850                 }
 851
 852                 /*
 853                  * don't block on non-blocking I/O
 854                  */
 855                 if (nbio) {
 856                         lwkt_reltoken(&wpipe->pipe_rlock);
 857                         error = EAGAIN;
 858                         break;
 859                 }
 860
 861                 /*
 862                  * re-test whether we have to block in the writer after
 863                  * acquiring both locks, in case the reader opened up
 864                  * some space.
 865                  */
 866                 space = wpipe->pipe_buffer.size -
 867                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 868                 cpu_lfence();
 869                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 870                         space = 0;
 871
 872                 /*
 873                  * Retest EOF - acquiring a new token can temporarily release
 874                  * tokens already held.
 875                  */
 876                 if (wpipe->pipe_state & PIPE_WEOF) {
 877                         lwkt_reltoken(&wpipe->pipe_rlock);
 878                         error = EPIPE;
 879                         break;
 880                 }
 881
 882                 /*
 883                  * We have no more space and have something to offer,
 884                  * wake up select/poll/kq.
 885                  */
 886                 if (space == 0) {
 887                         wpipe->pipe_state |= PIPE_WANTW;
 888                         ++wpipe->pipe_wantwcnt;
 889                         pipewakeup(wpipe, 1);
 890                         if (wpipe->pipe_state & PIPE_WANTW)
 891                                 error = tsleep(wpipe, PCATCH, "pipewr", 0);
 892                         ++pipe_wblocked_count;
 893                 }
 894                 lwkt_reltoken(&wpipe->pipe_rlock);
 895
 896                 /*
 897                  * Break out if we errored or the read side wants us to go
 898                  * away.
 899                  */
 900                 if (error)
 901                         break;
 902                 if (wpipe->pipe_state & PIPE_WEOF) {
 903                         error = EPIPE;
 904                         break;
 905                 }
 906         }
 907         pipe_end_uio(wpipe, &wpipe->pipe_wip);
 908
 909         /*
 910          * If we have put any characters in the buffer, we wake up
 911          * the reader.
 912          *
 913          * Both rlock and wlock are required to be able to modify pipe_state.
 914          */
 915         if (wpipe->pipe_buffer.windex != wpipe->pipe_buffer.rindex) {
 916                 if (wpipe->pipe_state & PIPE_WANTR) {
 917                         lwkt_gettoken(&wpipe->pipe_rlock);
 918                         if (wpipe->pipe_state & PIPE_WANTR) {
 919                                 wpipe->pipe_state &= ~PIPE_WANTR;
 920                                 lwkt_reltoken(&wpipe->pipe_rlock);
 921                                 wakeup(wpipe);
 922                         } else {
 923                                 lwkt_reltoken(&wpipe->pipe_rlock);
 924                         }
 925                 }
 926                 lwkt_gettoken(&wpipe->pipe_rlock);
 927                 pipewakeup(wpipe, 1);
 928                 lwkt_reltoken(&wpipe->pipe_rlock);
 929         }
 930
 931         /*
 932          * Don't return EPIPE if I/O was successful
 933          */
 934         if ((wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex) &&
 935             (uio->uio_resid == 0) &&
 936             (error == EPIPE)) {
 937                 error = 0;
 938         }
 939
 940         if (error == 0)
 941                 vfs_timestamp(&wpipe->pipe_mtime);
 942
 943         /*
 944          * We have something to offer,
 945          * wake up select/poll/kq.
 946          */
 947         /*space = wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex;*/
 948         lwkt_reltoken(&wpipe->pipe_wlock);
 949         return (error);
 950 }
 951
 952 /*
 953  * we implement a very minimal set of ioctls for compatibility with sockets.
 954  */
 955 int
 956 pipe_ioctl(struct file *fp, u_long cmd, caddr_t data,
 957            struct ucred *cred, struct sysmsg *msg)
 958 {
 959         struct pipe *mpipe;
 960         int error;
 961
 962         mpipe = (struct pipe *)fp->f_data;
 963
 964         lwkt_gettoken(&mpipe->pipe_rlock);
 965         lwkt_gettoken(&mpipe->pipe_wlock);
 966
 967         switch (cmd) {
 968         case FIOASYNC:
 969                 if (*(int *)data) {
 970                         mpipe->pipe_state |= PIPE_ASYNC;
 971                 } else {
 972                         mpipe->pipe_state &= ~PIPE_ASYNC;
 973                 }
 974                 error = 0;
 975                 break;
 976         case FIONREAD:
 977                 *(int *)data = mpipe->pipe_buffer.windex -
 978                                 mpipe->pipe_buffer.rindex;
 979                 error = 0;
 980                 break;
 981         case FIOSETOWN:
 982                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 983                 break;
 984         case FIOGETOWN:
 985                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 986                 error = 0;
 987                 break;
 988         case TIOCSPGRP:
 989                 /* This is deprecated, FIOSETOWN should be used instead. */
 990                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 991                 break;
 992
 993         case TIOCGPGRP:
 994                 /* This is deprecated, FIOGETOWN should be used instead. */
 995                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 996                 error = 0;
 997                 break;
 998         default:
 999                 error = ENOTTY;
1000                 break;
1001         }
1002         lwkt_reltoken(&mpipe->pipe_wlock);
1003         lwkt_reltoken(&mpipe->pipe_rlock);
1004
1005         return (error);
1006 }
1007
1008 /*
1009  * MPSAFE
1010  */
1011 static int
1012 pipe_stat(struct file *fp, struct stat *ub, struct ucred *cred)
1013 {
1014         struct pipe *pipe;
1015
1016         pipe = (struct pipe *)fp->f_data;
1017
1018         bzero((caddr_t)ub, sizeof(*ub));
1019         ub->st_mode = S_IFIFO;
1020         ub->st_blksize = pipe->pipe_buffer.size;
1021         ub->st_size = pipe->pipe_buffer.windex - pipe->pipe_buffer.rindex;
1022         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
1023         ub->st_atimespec = pipe->pipe_atime;
1024         ub->st_mtimespec = pipe->pipe_mtime;
1025         ub->st_ctimespec = pipe->pipe_ctime;
1026         /*
1027          * Left as 0: st_dev, st_ino, st_nlink, st_uid, st_gid, st_rdev,
1028          * st_flags, st_gen.
1029          * XXX (st_dev, st_ino) should be unique.
1030          */
1031         return (0);
1032 }
1033
1034 static int
1035 pipe_close(struct file *fp)
1036 {
1037         struct pipe *cpipe;
1038
1039         cpipe = (struct pipe *)fp->f_data;
1040         fp->f_ops = &badfileops;
1041         fp->f_data = NULL;
1042         funsetown(&cpipe->pipe_sigio);
1043         pipeclose(cpipe);
1044         return (0);
1045 }
1046
1047 /*
1048  * Shutdown one or both directions of a full-duplex pipe.
1049  */
1050 static int
1051 pipe_shutdown(struct file *fp, int how)
1052 {
1053         struct pipe *rpipe;
1054         struct pipe *wpipe;
1055         int error = EPIPE;
1056
1057         rpipe = (struct pipe *)fp->f_data;
1058         wpipe = rpipe->pipe_peer;
1059
1060         /*
1061          * We modify pipe_state on both pipes, which means we need
1062          * all four tokens!
1063          */
1064         lwkt_gettoken(&rpipe->pipe_rlock);
1065         lwkt_gettoken(&rpipe->pipe_wlock);
1066         lwkt_gettoken(&wpipe->pipe_rlock);
1067         lwkt_gettoken(&wpipe->pipe_wlock);
1068
1069         switch(how) {
1070         case SHUT_RDWR:
1071         case SHUT_RD:
1072                 rpipe->pipe_state |= PIPE_REOF;         /* my reads */
1073                 rpipe->pipe_state |= PIPE_WEOF;         /* peer writes */
1074                 if (rpipe->pipe_state & PIPE_WANTR) {
1075                         rpipe->pipe_state &= ~PIPE_WANTR;
1076                         wakeup(rpipe);
1077                 }
1078                 if (rpipe->pipe_state & PIPE_WANTW) {
1079                         rpipe->pipe_state &= ~PIPE_WANTW;
1080                         wakeup(rpipe);
1081                 }
1082                 error = 0;
1083                 if (how == SHUT_RD)
1084                         break;
1085                 /* fall through */
1086         case SHUT_WR:
1087                 wpipe->pipe_state |= PIPE_REOF;         /* peer reads */
1088                 wpipe->pipe_state |= PIPE_WEOF;         /* my writes */
1089                 if (wpipe->pipe_state & PIPE_WANTR) {
1090                         wpipe->pipe_state &= ~PIPE_WANTR;
1091                         wakeup(wpipe);
1092                 }
1093                 if (wpipe->pipe_state & PIPE_WANTW) {
1094                         wpipe->pipe_state &= ~PIPE_WANTW;
1095                         wakeup(wpipe);
1096                 }
1097                 error = 0;
1098                 break;
1099         }
1100         pipewakeup(rpipe, 1);
1101         pipewakeup(wpipe, 1);
1102
1103         lwkt_reltoken(&wpipe->pipe_wlock);
1104         lwkt_reltoken(&wpipe->pipe_rlock);
1105         lwkt_reltoken(&rpipe->pipe_wlock);
1106         lwkt_reltoken(&rpipe->pipe_rlock);
1107
1108         return (error);
1109 }
1110
1111 static void
1112 pipe_free_kmem(struct pipe *cpipe)
1113 {
1114         if (cpipe->pipe_buffer.buffer != NULL) {
1115                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
1116                         atomic_subtract_int(&pipe_nbig, 1);
1117                 kmem_free(&kernel_map,
1118                         (vm_offset_t)cpipe->pipe_buffer.buffer,
1119                         cpipe->pipe_buffer.size);
1120                 cpipe->pipe_buffer.buffer = NULL;
1121                 cpipe->pipe_buffer.object = NULL;
1122         }
1123 }
1124
1125 /*
1126  * Close the pipe.  The slock must be held to interlock against simultanious
1127  * closes.  The rlock and wlock must be held to adjust the pipe_state.
1128  */
1129 static void
1130 pipeclose(struct pipe *cpipe)
1131 {
1132         globaldata_t gd;
1133         struct pipe *ppipe;
1134
1135         if (cpipe == NULL)
1136                 return;
1137
1138         /*
1139          * The slock may not have been allocated yet (close during
1140          * initialization)
1141          *
1142          * We need both the read and write tokens to modify pipe_state.
1143          */
1144         if (cpipe->pipe_slock)
1145                 lockmgr(cpipe->pipe_slock, LK_EXCLUSIVE);
1146         lwkt_gettoken(&cpipe->pipe_rlock);
1147         lwkt_gettoken(&cpipe->pipe_wlock);
1148
1149         /*
1150          * Set our state, wakeup anyone waiting in select/poll/kq, and
1151          * wakeup anyone blocked on our pipe.
1152          */
1153         cpipe->pipe_state |= PIPE_CLOSED | PIPE_REOF | PIPE_WEOF;
1154         pipewakeup(cpipe, 1);
1155         if (cpipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1156                 cpipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1157                 wakeup(cpipe);
1158         }
1159
1160         /*
1161          * Disconnect from peer.
1162          */
1163         if ((ppipe = cpipe->pipe_peer) != NULL) {
1164                 lwkt_gettoken(&ppipe->pipe_rlock);
1165                 lwkt_gettoken(&ppipe->pipe_wlock);
1166                 ppipe->pipe_state |= PIPE_REOF | PIPE_WEOF;
1167                 pipewakeup(ppipe, 1);
1168                 if (ppipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1169                         ppipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1170                         wakeup(ppipe);
1171                 }
1172                 if (SLIST_FIRST(&ppipe->pipe_kq.ki_note))
1173                         KNOTE(&ppipe->pipe_kq.ki_note, 0);
1174                 lwkt_reltoken(&ppipe->pipe_wlock);
1175                 lwkt_reltoken(&ppipe->pipe_rlock);
1176         }
1177
1178         /*
1179          * If the peer is also closed we can free resources for both
1180          * sides, otherwise we leave our side intact to deal with any
1181          * races (since we only have the slock).
1182          */
1183         if (ppipe && (ppipe->pipe_state & PIPE_CLOSED)) {
1184                 cpipe->pipe_peer = NULL;
1185                 ppipe->pipe_peer = NULL;
1186                 ppipe->pipe_slock = NULL;       /* we will free the slock */
1187                 pipeclose(ppipe);
1188                 ppipe = NULL;
1189         }
1190
1191         lwkt_reltoken(&cpipe->pipe_wlock);
1192         lwkt_reltoken(&cpipe->pipe_rlock);
1193         if (cpipe->pipe_slock)
1194                 lockmgr(cpipe->pipe_slock, LK_RELEASE);
1195
1196         /*
1197          * If we disassociated from our peer we can free resources
1198          */
1199         if (ppipe == NULL) {
1200                 gd = mycpu;
1201                 if (cpipe->pipe_slock) {
1202                         kfree(cpipe->pipe_slock, M_PIPE);
1203                         cpipe->pipe_slock = NULL;
1204                 }
1205                 if (gd->gd_pipeqcount >= pipe_maxcache ||
1206                     cpipe->pipe_buffer.size != PIPE_SIZE
1207                 ) {
1208                         pipe_free_kmem(cpipe);
1209                         kfree(cpipe, M_PIPE);
1210                 } else {
1211                         cpipe->pipe_state = 0;
1212                         cpipe->pipe_peer = gd->gd_pipeq;
1213                         gd->gd_pipeq = cpipe;
1214                         ++gd->gd_pipeqcount;
1215                 }
1216         }
1217 }
1218
1219 static int
1220 pipe_kqfilter(struct file *fp, struct knote *kn)
1221 {
1222         struct pipe *cpipe;
1223
1224         cpipe = (struct pipe *)kn->kn_fp->f_data;
1225
1226         switch (kn->kn_filter) {
1227         case EVFILT_READ:
1228                 kn->kn_fop = &pipe_rfiltops;
1229                 break;
1230         case EVFILT_WRITE:
1231                 kn->kn_fop = &pipe_wfiltops;
1232                 if (cpipe->pipe_peer == NULL) {
1233                         /* other end of pipe has been closed */
1234                         return (EPIPE);
1235                 }
1236                 break;
1237         default:
1238                 return (EOPNOTSUPP);
1239         }
1240         kn->kn_hook = (caddr_t)cpipe;
1241
1242         knote_insert(&cpipe->pipe_kq.ki_note, kn);
1243
1244         return (0);
1245 }
1246
1247 static void
1248 filt_pipedetach(struct knote *kn)
1249 {
1250         struct pipe *cpipe = (struct pipe *)kn->kn_hook;
1251
1252         knote_remove(&cpipe->pipe_kq.ki_note, kn);
1253 }
1254
1255 /*ARGSUSED*/
1256 static int
1257 filt_piperead(struct knote *kn, long hint)
1258 {
1259         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1260         int ready = 0;
1261
1262         lwkt_gettoken(&rpipe->pipe_rlock);
1263         lwkt_gettoken(&rpipe->pipe_wlock);
1264
1265         kn->kn_data = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
1266
1267         if (rpipe->pipe_state & PIPE_REOF) {
1268                 /*
1269                  * Only set NODATA if all data has been exhausted
1270                  */
1271                 if (kn->kn_data == 0)
1272                         kn->kn_flags |= EV_NODATA;
1273                 kn->kn_flags |= EV_EOF;
1274                 ready = 1;
1275         }
1276
1277         lwkt_reltoken(&rpipe->pipe_wlock);
1278         lwkt_reltoken(&rpipe->pipe_rlock);
1279
1280         if (!ready)
1281                 ready = kn->kn_data > 0;
1282
1283         return (ready);
1284 }
1285
1286 /*ARGSUSED*/
1287 static int
1288 filt_pipewrite(struct knote *kn, long hint)
1289 {
1290         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1291         struct pipe *wpipe = rpipe->pipe_peer;
1292         int ready = 0;
1293
1294         kn->kn_data = 0;
1295         if (wpipe == NULL) {
1296                 kn->kn_flags |= (EV_EOF | EV_NODATA);
1297                 return (1);
1298         }
1299
1300         lwkt_gettoken(&wpipe->pipe_rlock);
1301         lwkt_gettoken(&wpipe->pipe_wlock);
1302
1303         if (wpipe->pipe_state & PIPE_WEOF) {
1304                 kn->kn_flags |= (EV_EOF | EV_NODATA);
1305                 ready = 1;
1306         }
1307
1308         if (!ready)
1309                 kn->kn_data = wpipe->pipe_buffer.size -
1310                               (wpipe->pipe_buffer.windex -
1311                                wpipe->pipe_buffer.rindex);
1312
1313         lwkt_reltoken(&wpipe->pipe_wlock);
1314         lwkt_reltoken(&wpipe->pipe_rlock);
1315
1316         if (!ready)
1317                 ready = kn->kn_data >= PIPE_BUF;
1318
1319         return (ready);
1320 }