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/signalvar.h>
  40 #include <sys/sysproto.h>
  41 #include <sys/pipe.h>
  42 #include <sys/vnode.h>
  43 #include <sys/uio.h>
  44 #include <sys/event.h>
  45 #include <sys/globaldata.h>
  46 #include <sys/module.h>
  47 #include <sys/malloc.h>
  48 #include <sys/sysctl.h>
  49 #include <sys/socket.h>
  50
  51 #include <vm/vm.h>
  52 #include <vm/vm_param.h>
  53 #include <sys/lock.h>
  54 #include <vm/vm_object.h>
  55 #include <vm/vm_kern.h>
  56 #include <vm/vm_extern.h>
  57 #include <vm/pmap.h>
  58 #include <vm/vm_map.h>
  59 #include <vm/vm_page.h>
  60 #include <vm/vm_zone.h>
  61
  62 #include <sys/file2.h>
  63 #include <sys/signal2.h>
  64
  65 #include <machine/cpufunc.h>
  66
  67 /*
  68  * interfaces to the outside world
  69  */
  70 static int pipe_read (struct file *fp, struct uio *uio,
  71                 struct ucred *cred, int flags);
  72 static int pipe_write (struct file *fp, struct uio *uio,
  73                 struct ucred *cred, int flags);
  74 static int pipe_close (struct file *fp);
  75 static int pipe_shutdown (struct file *fp, int how);
  76 static int pipe_kqfilter (struct file *fp, struct knote *kn);
  77 static int pipe_stat (struct file *fp, struct stat *sb, struct ucred *cred);
  78 static int pipe_ioctl (struct file *fp, u_long cmd, caddr_t data,
  79                 struct ucred *cred, struct sysmsg *msg);
  80
  81 static struct fileops pipeops = {
  82         .fo_read = pipe_read,
  83         .fo_write = pipe_write,
  84         .fo_ioctl = pipe_ioctl,
  85         .fo_kqfilter = pipe_kqfilter,
  86         .fo_stat = pipe_stat,
  87         .fo_close = pipe_close,
  88         .fo_shutdown = pipe_shutdown
  89 };
  90
  91 static void     filt_pipedetach(struct knote *kn);
  92 static int      filt_piperead(struct knote *kn, long hint);
  93 static int      filt_pipewrite(struct knote *kn, long hint);
  94
  95 static struct filterops pipe_rfiltops =
  96         { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_pipedetach, filt_piperead };
  97 static struct filterops pipe_wfiltops =
  98         { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_pipedetach, filt_pipewrite };
  99
 100 MALLOC_DEFINE(M_PIPE, "pipe", "pipe structures");
 101
 102 /*
 103  * Default pipe buffer size(s), this can be kind-of large now because pipe
 104  * space is pageable.  The pipe code will try to maintain locality of
 105  * reference for performance reasons, so small amounts of outstanding I/O
 106  * will not wipe the cache.
 107  */
 108 #define MINPIPESIZE (PIPE_SIZE/3)
 109 #define MAXPIPESIZE (2*PIPE_SIZE/3)
 110
 111 /*
 112  * Limit the number of "big" pipes
 113  */
 114 #define LIMITBIGPIPES   64
 115 #define PIPEQ_MAX_CACHE 16      /* per-cpu pipe structure cache */
 116
 117 static int pipe_maxbig = LIMITBIGPIPES;
 118 static int pipe_maxcache = PIPEQ_MAX_CACHE;
 119 static int pipe_bigcount;
 120 static int pipe_nbig;
 121 static int pipe_bcache_alloc;
 122 static int pipe_bkmem_alloc;
 123 static int pipe_rblocked_count;
 124 static int pipe_wblocked_count;
 125
 126 SYSCTL_NODE(_kern, OID_AUTO, pipe, CTLFLAG_RW, 0, "Pipe operation");
 127 SYSCTL_INT(_kern_pipe, OID_AUTO, nbig,
 128         CTLFLAG_RD, &pipe_nbig, 0, "numer of big pipes allocated");
 129 SYSCTL_INT(_kern_pipe, OID_AUTO, bigcount,
 130         CTLFLAG_RW, &pipe_bigcount, 0, "number of times pipe expanded");
 131 SYSCTL_INT(_kern_pipe, OID_AUTO, rblocked,
 132         CTLFLAG_RW, &pipe_rblocked_count, 0, "number of times pipe expanded");
 133 SYSCTL_INT(_kern_pipe, OID_AUTO, wblocked,
 134         CTLFLAG_RW, &pipe_wblocked_count, 0, "number of times pipe expanded");
 135 SYSCTL_INT(_kern_pipe, OID_AUTO, maxcache,
 136         CTLFLAG_RW, &pipe_maxcache, 0, "max pipes cached per-cpu");
 137 SYSCTL_INT(_kern_pipe, OID_AUTO, maxbig,
 138         CTLFLAG_RW, &pipe_maxbig, 0, "max number of big pipes");
 139 #ifdef SMP
 140 static int pipe_delay = 5000;   /* 5uS default */
 141 SYSCTL_INT(_kern_pipe, OID_AUTO, delay,
 142         CTLFLAG_RW, &pipe_delay, 0, "SMP delay optimization in ns");
 143 #endif
 144 #if !defined(NO_PIPE_SYSCTL_STATS)
 145 SYSCTL_INT(_kern_pipe, OID_AUTO, bcache_alloc,
 146         CTLFLAG_RW, &pipe_bcache_alloc, 0, "pipe buffer from pcpu cache");
 147 SYSCTL_INT(_kern_pipe, OID_AUTO, bkmem_alloc,
 148         CTLFLAG_RW, &pipe_bkmem_alloc, 0, "pipe buffer from kmem");
 149 #endif
 150
 151 /*
 152  * Auto-size pipe cache to reduce kmem allocations and frees.
 153  */
 154 static
 155 void
 156 pipeinit(void *dummy)
 157 {
 158         size_t mbytes = kmem_lim_size();
 159
 160         if (pipe_maxbig == LIMITBIGPIPES) {
 161                 if (mbytes >= 7 * 1024)
 162                         pipe_maxbig *= 2;
 163                 if (mbytes >= 15 * 1024)
 164                         pipe_maxbig *= 2;
 165         }
 166         if (pipe_maxcache == PIPEQ_MAX_CACHE) {
 167                 if (mbytes >= 7 * 1024)
 168                         pipe_maxcache *= 2;
 169                 if (mbytes >= 15 * 1024)
 170                         pipe_maxcache *= 2;
 171         }
 172 }
 173 SYSINIT(kmem, SI_BOOT2_MACHDEP, SI_ORDER_ANY, pipeinit, NULL)
 174
 175 static void pipeclose (struct pipe *cpipe);
 176 static void pipe_free_kmem (struct pipe *cpipe);
 177 static int pipe_create (struct pipe **cpipep);
 178 static int pipespace (struct pipe *cpipe, int size);
 179
 180 static __inline void
 181 pipewakeup(struct pipe *cpipe, int dosigio)
 182 {
 183         if (dosigio && (cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio) {
 184                 lwkt_gettoken(&proc_token);
 185                 pgsigio(cpipe->pipe_sigio, SIGIO, 0);
 186                 lwkt_reltoken(&proc_token);
 187         }
 188         KNOTE(&cpipe->pipe_kq.ki_note, 0);
 189 }
 190
 191 /*
 192  * These routines are called before and after a UIO.  The UIO
 193  * may block, causing our held tokens to be lost temporarily.
 194  *
 195  * We use these routines to serialize reads against other reads
 196  * and writes against other writes.
 197  *
 198  * The read token is held on entry so *ipp does not race.
 199  */
 200 static __inline int
 201 pipe_start_uio(struct pipe *cpipe, int *ipp)
 202 {
 203         int error;
 204
 205         while (*ipp) {
 206                 *ipp = -1;
 207                 error = tsleep(ipp, PCATCH, "pipexx", 0);
 208                 if (error)
 209                         return (error);
 210         }
 211         *ipp = 1;
 212         return (0);
 213 }
 214
 215 static __inline void
 216 pipe_end_uio(struct pipe *cpipe, int *ipp)
 217 {
 218         if (*ipp < 0) {
 219                 *ipp = 0;
 220                 wakeup(ipp);
 221         } else {
 222                 KKASSERT(*ipp > 0);
 223                 *ipp = 0;
 224         }
 225 }
 226
 227 /*
 228  * The pipe system call for the DTYPE_PIPE type of pipes
 229  *
 230  * pipe_args(int dummy)
 231  *
 232  * MPSAFE
 233  */
 234 int
 235 sys_pipe(struct pipe_args *uap)
 236 {
 237         struct thread *td = curthread;
 238         struct filedesc *fdp = td->td_proc->p_fd;
 239         struct file *rf, *wf;
 240         struct pipe *rpipe, *wpipe;
 241         int fd1, fd2, error;
 242
 243         rpipe = wpipe = NULL;
 244         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
 245                 pipeclose(rpipe);
 246                 pipeclose(wpipe);
 247                 return (ENFILE);
 248         }
 249
 250         error = falloc(td->td_lwp, &rf, &fd1);
 251         if (error) {
 252                 pipeclose(rpipe);
 253                 pipeclose(wpipe);
 254                 return (error);
 255         }
 256         uap->sysmsg_fds[0] = fd1;
 257
 258         /*
 259          * Warning: once we've gotten past allocation of the fd for the
 260          * read-side, we can only drop the read side via fdrop() in order
 261          * to avoid races against processes which manage to dup() the read
 262          * side while we are blocked trying to allocate the write side.
 263          */
 264         rf->f_type = DTYPE_PIPE;
 265         rf->f_flag = FREAD | FWRITE;
 266         rf->f_ops = &pipeops;
 267         rf->f_data = rpipe;
 268         error = falloc(td->td_lwp, &wf, &fd2);
 269         if (error) {
 270                 fsetfd(fdp, NULL, fd1);
 271                 fdrop(rf);
 272                 /* rpipe has been closed by fdrop(). */
 273                 pipeclose(wpipe);
 274                 return (error);
 275         }
 276         wf->f_type = DTYPE_PIPE;
 277         wf->f_flag = FREAD | FWRITE;
 278         wf->f_ops = &pipeops;
 279         wf->f_data = wpipe;
 280         uap->sysmsg_fds[1] = fd2;
 281
 282         rpipe->pipe_slock = kmalloc(sizeof(struct lock),
 283                                     M_PIPE, M_WAITOK|M_ZERO);
 284         wpipe->pipe_slock = rpipe->pipe_slock;
 285         rpipe->pipe_peer = wpipe;
 286         wpipe->pipe_peer = rpipe;
 287         lockinit(rpipe->pipe_slock, "pipecl", 0, 0);
 288
 289         /*
 290          * Once activated the peer relationship remains valid until
 291          * both sides are closed.
 292          */
 293         fsetfd(fdp, rf, fd1);
 294         fsetfd(fdp, wf, fd2);
 295         fdrop(rf);
 296         fdrop(wf);
 297
 298         return (0);
 299 }
 300
 301 /*
 302  * Allocate kva for pipe circular buffer, the space is pageable
 303  * This routine will 'realloc' the size of a pipe safely, if it fails
 304  * it will retain the old buffer.
 305  * If it fails it will return ENOMEM.
 306  */
 307 static int
 308 pipespace(struct pipe *cpipe, int size)
 309 {
 310         struct vm_object *object;
 311         caddr_t buffer;
 312         int npages, error;
 313
 314         npages = round_page(size) / PAGE_SIZE;
 315         object = cpipe->pipe_buffer.object;
 316
 317         /*
 318          * [re]create the object if necessary and reserve space for it
 319          * in the kernel_map.  The object and memory are pageable.  On
 320          * success, free the old resources before assigning the new
 321          * ones.
 322          */
 323         if (object == NULL || object->size != npages) {
 324                 object = vm_object_allocate(OBJT_DEFAULT, npages);
 325                 buffer = (caddr_t)vm_map_min(&kernel_map);
 326
 327                 error = vm_map_find(&kernel_map, object, 0,
 328                                     (vm_offset_t *)&buffer,
 329                                     size, PAGE_SIZE,
 330                                     1, VM_MAPTYPE_NORMAL,
 331                                     VM_PROT_ALL, VM_PROT_ALL,
 332                                     0);
 333
 334                 if (error != KERN_SUCCESS) {
 335                         vm_object_deallocate(object);
 336                         return (ENOMEM);
 337                 }
 338                 pipe_free_kmem(cpipe);
 339                 cpipe->pipe_buffer.object = object;
 340                 cpipe->pipe_buffer.buffer = buffer;
 341                 cpipe->pipe_buffer.size = size;
 342                 ++pipe_bkmem_alloc;
 343         } else {
 344                 ++pipe_bcache_alloc;
 345         }
 346         cpipe->pipe_buffer.rindex = 0;
 347         cpipe->pipe_buffer.windex = 0;
 348         return (0);
 349 }
 350
 351 /*
 352  * Initialize and allocate VM and memory for pipe, pulling the pipe from
 353  * our per-cpu cache if possible.  For now make sure it is sized for the
 354  * smaller PIPE_SIZE default.
 355  */
 356 static int
 357 pipe_create(struct pipe **cpipep)
 358 {
 359         globaldata_t gd = mycpu;
 360         struct pipe *cpipe;
 361         int error;
 362
 363         if ((cpipe = gd->gd_pipeq) != NULL) {
 364                 gd->gd_pipeq = cpipe->pipe_peer;
 365                 --gd->gd_pipeqcount;
 366                 cpipe->pipe_peer = NULL;
 367                 cpipe->pipe_wantwcnt = 0;
 368         } else {
 369                 cpipe = kmalloc(sizeof(struct pipe), M_PIPE, M_WAITOK|M_ZERO);
 370         }
 371         *cpipep = cpipe;
 372         if ((error = pipespace(cpipe, PIPE_SIZE)) != 0)
 373                 return (error);
 374         vfs_timestamp(&cpipe->pipe_ctime);
 375         cpipe->pipe_atime = cpipe->pipe_ctime;
 376         cpipe->pipe_mtime = cpipe->pipe_ctime;
 377         lwkt_token_init(&cpipe->pipe_rlock, "piper");
 378         lwkt_token_init(&cpipe->pipe_wlock, "pipew");
 379         return (0);
 380 }
 381
 382 static int
 383 pipe_read(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 384 {
 385         struct pipe *rpipe;
 386         struct pipe *wpipe;
 387         int error;
 388         size_t nread = 0;
 389         int nbio;
 390         u_int size;     /* total bytes available */
 391         u_int nsize;    /* total bytes to read */
 392         u_int rindex;   /* contiguous bytes available */
 393         int notify_writer;
 394         int bigread;
 395         int bigcount;
 396
 397         if (uio->uio_resid == 0)
 398                 return(0);
 399
 400         /*
 401          * Setup locks, calculate nbio
 402          */
 403         rpipe = (struct pipe *)fp->f_data;
 404         wpipe = rpipe->pipe_peer;
 405         lwkt_gettoken(&rpipe->pipe_rlock);
 406
 407         if (fflags & O_FBLOCKING)
 408                 nbio = 0;
 409         else if (fflags & O_FNONBLOCKING)
 410                 nbio = 1;
 411         else if (fp->f_flag & O_NONBLOCK)
 412                 nbio = 1;
 413         else
 414                 nbio = 0;
 415
 416         /*
 417          * Reads are serialized.  Note however that pipe_buffer.buffer and
 418          * pipe_buffer.size can change out from under us when the number
 419          * of bytes in the buffer are zero due to the write-side doing a
 420          * pipespace().
 421          */
 422         error = pipe_start_uio(rpipe, &rpipe->pipe_rip);
 423         if (error) {
 424                 lwkt_reltoken(&rpipe->pipe_rlock);
 425                 return (error);
 426         }
 427         notify_writer = 0;
 428
 429         bigread = (uio->uio_resid > 10 * 1024 * 1024);
 430         bigcount = 10;
 431
 432         while (uio->uio_resid) {
 433                 /*
 434                  * Don't hog the cpu.
 435                  */
 436                 if (bigread && --bigcount == 0) {
 437                         lwkt_user_yield();
 438                         bigcount = 10;
 439                         if (CURSIG(curthread->td_lwp)) {
 440                                 error = EINTR;
 441                                 break;
 442                         }
 443                 }
 444
 445                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 446                 cpu_lfence();
 447                 if (size) {
 448                         rindex = rpipe->pipe_buffer.rindex &
 449                                  (rpipe->pipe_buffer.size - 1);
 450                         nsize = size;
 451                         if (nsize > rpipe->pipe_buffer.size - rindex)
 452                                 nsize = rpipe->pipe_buffer.size - rindex;
 453                         nsize = szmin(nsize, uio->uio_resid);
 454
 455                         error = uiomove(&rpipe->pipe_buffer.buffer[rindex],
 456                                         nsize, uio);
 457                         if (error)
 458                                 break;
 459                         cpu_mfence();
 460                         rpipe->pipe_buffer.rindex += nsize;
 461                         nread += nsize;
 462
 463                         /*
 464                          * If the FIFO is still over half full just continue
 465                          * and do not try to notify the writer yet.
 466                          */
 467                         if (size - nsize >= (rpipe->pipe_buffer.size >> 1)) {
 468                                 notify_writer = 0;
 469                                 continue;
 470                         }
 471
 472                         /*
 473                          * When the FIFO is less then half full notify any
 474                          * waiting writer.  WANTW can be checked while
 475                          * holding just the rlock.
 476                          */
 477                         notify_writer = 1;
 478                         if ((rpipe->pipe_state & PIPE_WANTW) == 0)
 479                                 continue;
 480                 }
 481
 482                 /*
 483                  * If the "write-side" was blocked we wake it up.  This code
 484                  * is reached either when the buffer is completely emptied
 485                  * or if it becomes more then half-empty.
 486                  *
 487                  * Pipe_state can only be modified if both the rlock and
 488                  * wlock are held.
 489                  */
 490                 if (rpipe->pipe_state & PIPE_WANTW) {
 491                         lwkt_gettoken(&rpipe->pipe_wlock);
 492                         if (rpipe->pipe_state & PIPE_WANTW) {
 493                                 rpipe->pipe_state &= ~PIPE_WANTW;
 494                                 lwkt_reltoken(&rpipe->pipe_wlock);
 495                                 wakeup(rpipe);
 496                         } else {
 497                                 lwkt_reltoken(&rpipe->pipe_wlock);
 498                         }
 499                 }
 500
 501                 /*
 502                  * Pick up our copy loop again if the writer sent data to
 503                  * us while we were messing around.
 504                  *
 505                  * On a SMP box poll up to pipe_delay nanoseconds for new
 506                  * data.  Typically a value of 2000 to 4000 is sufficient
 507                  * to eradicate most IPIs/tsleeps/wakeups when a pipe
 508                  * is used for synchronous communications with small packets,
 509                  * and 8000 or so (8uS) will pipeline large buffer xfers
 510                  * between cpus over a pipe.
 511                  *
 512                  * For synchronous communications a hit means doing a
 513                  * full Awrite-Bread-Bwrite-Aread cycle in less then 2uS,
 514                  * where as miss requiring a tsleep/wakeup sequence
 515                  * will take 7uS or more.
 516                  */
 517                 if (rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex)
 518                         continue;
 519
 520 #if defined(SMP) && defined(_RDTSC_SUPPORTED_)
 521                 if (pipe_delay) {
 522                         int64_t tsc_target;
 523                         int good = 0;
 524
 525                         tsc_target = tsc_get_target(pipe_delay);
 526                         while (tsc_test_target(tsc_target) == 0) {
 527                                 if (rpipe->pipe_buffer.windex !=
 528                                     rpipe->pipe_buffer.rindex) {
 529                                         good = 1;
 530                                         break;
 531                                 }
 532                         }
 533                         if (good)
 534                                 continue;
 535                 }
 536 #endif
 537
 538                 /*
 539                  * Detect EOF condition, do not set error.
 540                  */
 541                 if (rpipe->pipe_state & PIPE_REOF)
 542                         break;
 543
 544                 /*
 545                  * Break if some data was read, or if this was a non-blocking
 546                  * read.
 547                  */
 548                 if (nread > 0)
 549                         break;
 550
 551                 if (nbio) {
 552                         error = EAGAIN;
 553                         break;
 554                 }
 555
 556                 /*
 557                  * Last chance, interlock with WANTR.
 558                  */
 559                 lwkt_gettoken(&rpipe->pipe_wlock);
 560                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 561                 if (size) {
 562                         lwkt_reltoken(&rpipe->pipe_wlock);
 563                         continue;
 564                 }
 565
 566                 /*
 567                  * Retest EOF - acquiring a new token can temporarily release
 568                  * tokens already held.
 569                  */
 570                 if (rpipe->pipe_state & PIPE_REOF) {
 571                         lwkt_reltoken(&rpipe->pipe_wlock);
 572                         break;
 573                 }
 574
 575                 /*
 576                  * If there is no more to read in the pipe, reset its
 577                  * pointers to the beginning.  This improves cache hit
 578                  * stats.
 579                  *
 580                  * We need both locks to modify both pointers, and there
 581                  * must also not be a write in progress or the uiomove()
 582                  * in the write might block and temporarily release
 583                  * its wlock, then reacquire and update windex.  We are
 584                  * only serialized against reads, not writes.
 585                  *
 586                  * XXX should we even bother resetting the indices?  It
 587                  *     might actually be more cache efficient not to.
 588                  */
 589                 if (rpipe->pipe_buffer.rindex == rpipe->pipe_buffer.windex &&
 590                     rpipe->pipe_wip == 0) {
 591                         rpipe->pipe_buffer.rindex = 0;
 592                         rpipe->pipe_buffer.windex = 0;
 593                 }
 594
 595                 /*
 596                  * Wait for more data.
 597                  *
 598                  * Pipe_state can only be set if both the rlock and wlock
 599                  * are held.
 600                  */
 601                 rpipe->pipe_state |= PIPE_WANTR;
 602                 tsleep_interlock(rpipe, PCATCH);
 603                 lwkt_reltoken(&rpipe->pipe_wlock);
 604                 error = tsleep(rpipe, PCATCH | PINTERLOCKED, "piperd", 0);
 605                 ++pipe_rblocked_count;
 606                 if (error)
 607                         break;
 608         }
 609         pipe_end_uio(rpipe, &rpipe->pipe_rip);
 610
 611         /*
 612          * Uptime last access time
 613          */
 614         if (error == 0 && nread)
 615                 vfs_timestamp(&rpipe->pipe_atime);
 616
 617         /*
 618          * If we drained the FIFO more then half way then handle
 619          * write blocking hysteresis.
 620          *
 621          * Note that PIPE_WANTW cannot be set by the writer without
 622          * it holding both rlock and wlock, so we can test it
 623          * while holding just rlock.
 624          */
 625         if (notify_writer) {
 626                 /*
 627                  * Synchronous blocking is done on the pipe involved
 628                  */
 629                 if (rpipe->pipe_state & PIPE_WANTW) {
 630                         lwkt_gettoken(&rpipe->pipe_wlock);
 631                         if (rpipe->pipe_state & PIPE_WANTW) {
 632                                 rpipe->pipe_state &= ~PIPE_WANTW;
 633                                 lwkt_reltoken(&rpipe->pipe_wlock);
 634                                 wakeup(rpipe);
 635                         } else {
 636                                 lwkt_reltoken(&rpipe->pipe_wlock);
 637                         }
 638                 }
 639
 640                 /*
 641                  * But we may also have to deal with a kqueue which is
 642                  * stored on the same pipe as its descriptor, so a
 643                  * EVFILT_WRITE event waiting for our side to drain will
 644                  * be on the other side.
 645                  */
 646                 lwkt_gettoken(&wpipe->pipe_wlock);
 647                 pipewakeup(wpipe, 0);
 648                 lwkt_reltoken(&wpipe->pipe_wlock);
 649         }
 650         /*size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;*/
 651         lwkt_reltoken(&rpipe->pipe_rlock);
 652
 653         return (error);
 654 }
 655
 656 static int
 657 pipe_write(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 658 {
 659         int error;
 660         int orig_resid;
 661         int nbio;
 662         struct pipe *wpipe;
 663         struct pipe *rpipe;
 664         u_int windex;
 665         u_int space;
 666         u_int wcount;
 667         int bigwrite;
 668         int bigcount;
 669
 670         /*
 671          * Writes go to the peer.  The peer will always exist.
 672          */
 673         rpipe = (struct pipe *) fp->f_data;
 674         wpipe = rpipe->pipe_peer;
 675         lwkt_gettoken(&wpipe->pipe_wlock);
 676         if (wpipe->pipe_state & PIPE_WEOF) {
 677                 lwkt_reltoken(&wpipe->pipe_wlock);
 678                 return (EPIPE);
 679         }
 680
 681         /*
 682          * Degenerate case (EPIPE takes prec)
 683          */
 684         if (uio->uio_resid == 0) {
 685                 lwkt_reltoken(&wpipe->pipe_wlock);
 686                 return(0);
 687         }
 688
 689         /*
 690          * Writes are serialized (start_uio must be called with wlock)
 691          */
 692         error = pipe_start_uio(wpipe, &wpipe->pipe_wip);
 693         if (error) {
 694                 lwkt_reltoken(&wpipe->pipe_wlock);
 695                 return (error);
 696         }
 697
 698         if (fflags & O_FBLOCKING)
 699                 nbio = 0;
 700         else if (fflags & O_FNONBLOCKING)
 701                 nbio = 1;
 702         else if (fp->f_flag & O_NONBLOCK)
 703                 nbio = 1;
 704         else
 705                 nbio = 0;
 706
 707         /*
 708          * If it is advantageous to resize the pipe buffer, do
 709          * so.  We are write-serialized so we can block safely.
 710          */
 711         if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 712             (pipe_nbig < pipe_maxbig) &&
 713             wpipe->pipe_wantwcnt > 4 &&
 714             (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 715                 /*
 716                  * Recheck after lock.
 717                  */
 718                 lwkt_gettoken(&wpipe->pipe_rlock);
 719                 if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 720                     (pipe_nbig < pipe_maxbig) &&
 721                     (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 722                         atomic_add_int(&pipe_nbig, 1);
 723                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
 724                                 ++pipe_bigcount;
 725                         else
 726                                 atomic_subtract_int(&pipe_nbig, 1);
 727                 }
 728                 lwkt_reltoken(&wpipe->pipe_rlock);
 729         }
 730
 731         orig_resid = uio->uio_resid;
 732         wcount = 0;
 733
 734         bigwrite = (uio->uio_resid > 10 * 1024 * 1024);
 735         bigcount = 10;
 736
 737         while (uio->uio_resid) {
 738                 if (wpipe->pipe_state & PIPE_WEOF) {
 739                         error = EPIPE;
 740                         break;
 741                 }
 742
 743                 /*
 744                  * Don't hog the cpu.
 745                  */
 746                 if (bigwrite && --bigcount == 0) {
 747                         lwkt_user_yield();
 748                         bigcount = 10;
 749                         if (CURSIG(curthread->td_lwp)) {
 750                                 error = EINTR;
 751                                 break;
 752                         }
 753                 }
 754
 755                 windex = wpipe->pipe_buffer.windex &
 756                          (wpipe->pipe_buffer.size - 1);
 757                 space = wpipe->pipe_buffer.size -
 758                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 759                 cpu_lfence();
 760
 761                 /* Writes of size <= PIPE_BUF must be atomic. */
 762                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 763                         space = 0;
 764
 765                 /*
 766                  * Write to fill, read size handles write hysteresis.  Also
 767                  * additional restrictions can cause select-based non-blocking
 768                  * writes to spin.
 769                  */
 770                 if (space > 0) {
 771                         u_int segsize;
 772
 773                         /*
 774                          * Transfer size is minimum of uio transfer
 775                          * and free space in pipe buffer.
 776                          *
 777                          * Limit each uiocopy to no more then PIPE_SIZE
 778                          * so we can keep the gravy train going on a
 779                          * SMP box.  This doubles the performance for
 780                          * write sizes > 16K.  Otherwise large writes
 781                          * wind up doing an inefficient synchronous
 782                          * ping-pong.
 783                          */
 784                         space = szmin(space, uio->uio_resid);
 785                         if (space > PIPE_SIZE)
 786                                 space = PIPE_SIZE;
 787
 788                         /*
 789                          * First segment to transfer is minimum of
 790                          * transfer size and contiguous space in
 791                          * pipe buffer.  If first segment to transfer
 792                          * is less than the transfer size, we've got
 793                          * a wraparound in the buffer.
 794                          */
 795                         segsize = wpipe->pipe_buffer.size - windex;
 796                         if (segsize > space)
 797                                 segsize = space;
 798
 799 #ifdef SMP
 800                         /*
 801                          * If this is the first loop and the reader is
 802                          * blocked, do a preemptive wakeup of the reader.
 803                          *
 804                          * On SMP the IPI latency plus the wlock interlock
 805                          * on the reader side is the fastest way to get the
 806                          * reader going.  (The scheduler will hard loop on
 807                          * lock tokens).
 808                          *
 809                          * NOTE: We can't clear WANTR here without acquiring
 810                          * the rlock, which we don't want to do here!
 811                          */
 812                         if ((wpipe->pipe_state & PIPE_WANTR))
 813                                 wakeup(wpipe);
 814 #endif
 815
 816                         /*
 817                          * Transfer segment, which may include a wrap-around.
 818                          * Update windex to account for both all in one go
 819                          * so the reader can read() the data atomically.
 820                          */
 821                         error = uiomove(&wpipe->pipe_buffer.buffer[windex],
 822                                         segsize, uio);
 823                         if (error == 0 && segsize < space) {
 824                                 segsize = space - segsize;
 825                                 error = uiomove(&wpipe->pipe_buffer.buffer[0],
 826                                                 segsize, uio);
 827                         }
 828                         if (error)
 829                                 break;
 830                         cpu_mfence();
 831                         wpipe->pipe_buffer.windex += space;
 832                         wcount += space;
 833                         continue;
 834                 }
 835
 836                 /*
 837                  * We need both the rlock and the wlock to interlock against
 838                  * the EOF, WANTW, and size checks, and to modify pipe_state.
 839                  *
 840                  * These are token locks so we do not have to worry about
 841                  * deadlocks.
 842                  */
 843                 lwkt_gettoken(&wpipe->pipe_rlock);
 844
 845                 /*
 846                  * If the "read-side" has been blocked, wake it up now
 847                  * and yield to let it drain synchronously rather
 848                  * then block.
 849                  */
 850                 if (wpipe->pipe_state & PIPE_WANTR) {
 851                         wpipe->pipe_state &= ~PIPE_WANTR;
 852                         wakeup(wpipe);
 853                 }
 854
 855                 /*
 856                  * don't block on non-blocking I/O
 857                  */
 858                 if (nbio) {
 859                         lwkt_reltoken(&wpipe->pipe_rlock);
 860                         error = EAGAIN;
 861                         break;
 862                 }
 863
 864                 /*
 865                  * re-test whether we have to block in the writer after
 866                  * acquiring both locks, in case the reader opened up
 867                  * some space.
 868                  */
 869                 space = wpipe->pipe_buffer.size -
 870                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 871                 cpu_lfence();
 872                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 873                         space = 0;
 874
 875                 /*
 876                  * Retest EOF - acquiring a new token can temporarily release
 877                  * tokens already held.
 878                  */
 879                 if (wpipe->pipe_state & PIPE_WEOF) {
 880                         lwkt_reltoken(&wpipe->pipe_rlock);
 881                         error = EPIPE;
 882                         break;
 883                 }
 884
 885                 /*
 886                  * We have no more space and have something to offer,
 887                  * wake up select/poll/kq.
 888                  */
 889                 if (space == 0) {
 890                         wpipe->pipe_state |= PIPE_WANTW;
 891                         ++wpipe->pipe_wantwcnt;
 892                         pipewakeup(wpipe, 1);
 893                         if (wpipe->pipe_state & PIPE_WANTW)
 894                                 error = tsleep(wpipe, PCATCH, "pipewr", 0);
 895                         ++pipe_wblocked_count;
 896                 }
 897                 lwkt_reltoken(&wpipe->pipe_rlock);
 898
 899                 /*
 900                  * Break out if we errored or the read side wants us to go
 901                  * away.
 902                  */
 903                 if (error)
 904                         break;
 905                 if (wpipe->pipe_state & PIPE_WEOF) {
 906                         error = EPIPE;
 907                         break;
 908                 }
 909         }
 910         pipe_end_uio(wpipe, &wpipe->pipe_wip);
 911
 912         /*
 913          * If we have put any characters in the buffer, we wake up
 914          * the reader.
 915          *
 916          * Both rlock and wlock are required to be able to modify pipe_state.
 917          */
 918         if (wpipe->pipe_buffer.windex != wpipe->pipe_buffer.rindex) {
 919                 if (wpipe->pipe_state & PIPE_WANTR) {
 920                         lwkt_gettoken(&wpipe->pipe_rlock);
 921                         if (wpipe->pipe_state & PIPE_WANTR) {
 922                                 wpipe->pipe_state &= ~PIPE_WANTR;
 923                                 lwkt_reltoken(&wpipe->pipe_rlock);
 924                                 wakeup(wpipe);
 925                         } else {
 926                                 lwkt_reltoken(&wpipe->pipe_rlock);
 927                         }
 928                 }
 929                 lwkt_gettoken(&wpipe->pipe_rlock);
 930                 pipewakeup(wpipe, 1);
 931                 lwkt_reltoken(&wpipe->pipe_rlock);
 932         }
 933
 934         /*
 935          * Don't return EPIPE if I/O was successful
 936          */
 937         if ((wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex) &&
 938             (uio->uio_resid == 0) &&
 939             (error == EPIPE)) {
 940                 error = 0;
 941         }
 942
 943         if (error == 0)
 944                 vfs_timestamp(&wpipe->pipe_mtime);
 945
 946         /*
 947          * We have something to offer,
 948          * wake up select/poll/kq.
 949          */
 950         /*space = wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex;*/
 951         lwkt_reltoken(&wpipe->pipe_wlock);
 952         return (error);
 953 }
 954
 955 /*
 956  * we implement a very minimal set of ioctls for compatibility with sockets.
 957  */
 958 int
 959 pipe_ioctl(struct file *fp, u_long cmd, caddr_t data,
 960            struct ucred *cred, struct sysmsg *msg)
 961 {
 962         struct pipe *mpipe;
 963         int error;
 964
 965         mpipe = (struct pipe *)fp->f_data;
 966
 967         lwkt_gettoken(&mpipe->pipe_rlock);
 968         lwkt_gettoken(&mpipe->pipe_wlock);
 969
 970         switch (cmd) {
 971         case FIOASYNC:
 972                 if (*(int *)data) {
 973                         mpipe->pipe_state |= PIPE_ASYNC;
 974                 } else {
 975                         mpipe->pipe_state &= ~PIPE_ASYNC;
 976                 }
 977                 error = 0;
 978                 break;
 979         case FIONREAD:
 980                 *(int *)data = mpipe->pipe_buffer.windex -
 981                                 mpipe->pipe_buffer.rindex;
 982                 error = 0;
 983                 break;
 984         case FIOSETOWN:
 985                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 986                 break;
 987         case FIOGETOWN:
 988                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 989                 error = 0;
 990                 break;
 991         case TIOCSPGRP:
 992                 /* This is deprecated, FIOSETOWN should be used instead. */
 993                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 994                 break;
 995
 996         case TIOCGPGRP:
 997                 /* This is deprecated, FIOGETOWN should be used instead. */
 998                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 999                 error = 0;
1000                 break;
1001         default:
1002                 error = ENOTTY;
1003                 break;
1004         }
1005         lwkt_reltoken(&mpipe->pipe_wlock);
1006         lwkt_reltoken(&mpipe->pipe_rlock);
1007
1008         return (error);
1009 }
1010
1011 /*
1012  * MPSAFE
1013  */
1014 static int
1015 pipe_stat(struct file *fp, struct stat *ub, struct ucred *cred)
1016 {
1017         struct pipe *pipe;
1018
1019         pipe = (struct pipe *)fp->f_data;
1020
1021         bzero((caddr_t)ub, sizeof(*ub));
1022         ub->st_mode = S_IFIFO;
1023         ub->st_blksize = pipe->pipe_buffer.size;
1024         ub->st_size = pipe->pipe_buffer.windex - pipe->pipe_buffer.rindex;
1025         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
1026         ub->st_atimespec = pipe->pipe_atime;
1027         ub->st_mtimespec = pipe->pipe_mtime;
1028         ub->st_ctimespec = pipe->pipe_ctime;
1029         /*
1030          * Left as 0: st_dev, st_ino, st_nlink, st_uid, st_gid, st_rdev,
1031          * st_flags, st_gen.
1032          * XXX (st_dev, st_ino) should be unique.
1033          */
1034         return (0);
1035 }
1036
1037 static int
1038 pipe_close(struct file *fp)
1039 {
1040         struct pipe *cpipe;
1041
1042         cpipe = (struct pipe *)fp->f_data;
1043         fp->f_ops = &badfileops;
1044         fp->f_data = NULL;
1045         funsetown(&cpipe->pipe_sigio);
1046         pipeclose(cpipe);
1047         return (0);
1048 }
1049
1050 /*
1051  * Shutdown one or both directions of a full-duplex pipe.
1052  */
1053 static int
1054 pipe_shutdown(struct file *fp, int how)
1055 {
1056         struct pipe *rpipe;
1057         struct pipe *wpipe;
1058         int error = EPIPE;
1059
1060         rpipe = (struct pipe *)fp->f_data;
1061         wpipe = rpipe->pipe_peer;
1062
1063         /*
1064          * We modify pipe_state on both pipes, which means we need
1065          * all four tokens!
1066          */
1067         lwkt_gettoken(&rpipe->pipe_rlock);
1068         lwkt_gettoken(&rpipe->pipe_wlock);
1069         lwkt_gettoken(&wpipe->pipe_rlock);
1070         lwkt_gettoken(&wpipe->pipe_wlock);
1071
1072         switch(how) {
1073         case SHUT_RDWR:
1074         case SHUT_RD:
1075                 rpipe->pipe_state |= PIPE_REOF;         /* my reads */
1076                 rpipe->pipe_state |= PIPE_WEOF;         /* peer writes */
1077                 if (rpipe->pipe_state & PIPE_WANTR) {
1078                         rpipe->pipe_state &= ~PIPE_WANTR;
1079                         wakeup(rpipe);
1080                 }
1081                 if (rpipe->pipe_state & PIPE_WANTW) {
1082                         rpipe->pipe_state &= ~PIPE_WANTW;
1083                         wakeup(rpipe);
1084                 }
1085                 error = 0;
1086                 if (how == SHUT_RD)
1087                         break;
1088                 /* fall through */
1089         case SHUT_WR:
1090                 wpipe->pipe_state |= PIPE_REOF;         /* peer reads */
1091                 wpipe->pipe_state |= PIPE_WEOF;         /* my writes */
1092                 if (wpipe->pipe_state & PIPE_WANTR) {
1093                         wpipe->pipe_state &= ~PIPE_WANTR;
1094                         wakeup(wpipe);
1095                 }
1096                 if (wpipe->pipe_state & PIPE_WANTW) {
1097                         wpipe->pipe_state &= ~PIPE_WANTW;
1098                         wakeup(wpipe);
1099                 }
1100                 error = 0;
1101                 break;
1102         }
1103         pipewakeup(rpipe, 1);
1104         pipewakeup(wpipe, 1);
1105
1106         lwkt_reltoken(&wpipe->pipe_wlock);
1107         lwkt_reltoken(&wpipe->pipe_rlock);
1108         lwkt_reltoken(&rpipe->pipe_wlock);
1109         lwkt_reltoken(&rpipe->pipe_rlock);
1110
1111         return (error);
1112 }
1113
1114 static void
1115 pipe_free_kmem(struct pipe *cpipe)
1116 {
1117         if (cpipe->pipe_buffer.buffer != NULL) {
1118                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
1119                         atomic_subtract_int(&pipe_nbig, 1);
1120                 kmem_free(&kernel_map,
1121                         (vm_offset_t)cpipe->pipe_buffer.buffer,
1122                         cpipe->pipe_buffer.size);
1123                 cpipe->pipe_buffer.buffer = NULL;
1124                 cpipe->pipe_buffer.object = NULL;
1125         }
1126 }
1127
1128 /*
1129  * Close the pipe.  The slock must be held to interlock against simultanious
1130  * closes.  The rlock and wlock must be held to adjust the pipe_state.
1131  */
1132 static void
1133 pipeclose(struct pipe *cpipe)
1134 {
1135         globaldata_t gd;
1136         struct pipe *ppipe;
1137
1138         if (cpipe == NULL)
1139                 return;
1140
1141         /*
1142          * The slock may not have been allocated yet (close during
1143          * initialization)
1144          *
1145          * We need both the read and write tokens to modify pipe_state.
1146          */
1147         if (cpipe->pipe_slock)
1148                 lockmgr(cpipe->pipe_slock, LK_EXCLUSIVE);
1149         lwkt_gettoken(&cpipe->pipe_rlock);
1150         lwkt_gettoken(&cpipe->pipe_wlock);
1151
1152         /*
1153          * Set our state, wakeup anyone waiting in select/poll/kq, and
1154          * wakeup anyone blocked on our pipe.
1155          */
1156         cpipe->pipe_state |= PIPE_CLOSED | PIPE_REOF | PIPE_WEOF;
1157         pipewakeup(cpipe, 1);
1158         if (cpipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1159                 cpipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1160                 wakeup(cpipe);
1161         }
1162
1163         /*
1164          * Disconnect from peer.
1165          */
1166         if ((ppipe = cpipe->pipe_peer) != NULL) {
1167                 lwkt_gettoken(&ppipe->pipe_rlock);
1168                 lwkt_gettoken(&ppipe->pipe_wlock);
1169                 ppipe->pipe_state |= PIPE_REOF | PIPE_WEOF;
1170                 pipewakeup(ppipe, 1);
1171                 if (ppipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1172                         ppipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1173                         wakeup(ppipe);
1174                 }
1175                 if (SLIST_FIRST(&ppipe->pipe_kq.ki_note))
1176                         KNOTE(&ppipe->pipe_kq.ki_note, 0);
1177                 lwkt_reltoken(&ppipe->pipe_wlock);
1178                 lwkt_reltoken(&ppipe->pipe_rlock);
1179         }
1180
1181         /*
1182          * If the peer is also closed we can free resources for both
1183          * sides, otherwise we leave our side intact to deal with any
1184          * races (since we only have the slock).
1185          */
1186         if (ppipe && (ppipe->pipe_state & PIPE_CLOSED)) {
1187                 cpipe->pipe_peer = NULL;
1188                 ppipe->pipe_peer = NULL;
1189                 ppipe->pipe_slock = NULL;       /* we will free the slock */
1190                 pipeclose(ppipe);
1191                 ppipe = NULL;
1192         }
1193
1194         lwkt_reltoken(&cpipe->pipe_wlock);
1195         lwkt_reltoken(&cpipe->pipe_rlock);
1196         if (cpipe->pipe_slock)
1197                 lockmgr(cpipe->pipe_slock, LK_RELEASE);
1198
1199         /*
1200          * If we disassociated from our peer we can free resources
1201          */
1202         if (ppipe == NULL) {
1203                 gd = mycpu;
1204                 if (cpipe->pipe_slock) {
1205                         kfree(cpipe->pipe_slock, M_PIPE);
1206                         cpipe->pipe_slock = NULL;
1207                 }
1208                 if (gd->gd_pipeqcount >= pipe_maxcache ||
1209                     cpipe->pipe_buffer.size != PIPE_SIZE
1210                 ) {
1211                         pipe_free_kmem(cpipe);
1212                         kfree(cpipe, M_PIPE);
1213                 } else {
1214                         cpipe->pipe_state = 0;
1215                         cpipe->pipe_peer = gd->gd_pipeq;
1216                         gd->gd_pipeq = cpipe;
1217                         ++gd->gd_pipeqcount;
1218                 }
1219         }
1220 }
1221
1222 static int
1223 pipe_kqfilter(struct file *fp, struct knote *kn)
1224 {
1225         struct pipe *cpipe;
1226
1227         cpipe = (struct pipe *)kn->kn_fp->f_data;
1228
1229         switch (kn->kn_filter) {
1230         case EVFILT_READ:
1231                 kn->kn_fop = &pipe_rfiltops;
1232                 break;
1233         case EVFILT_WRITE:
1234                 kn->kn_fop = &pipe_wfiltops;
1235                 if (cpipe->pipe_peer == NULL) {
1236                         /* other end of pipe has been closed */
1237                         return (EPIPE);
1238                 }
1239                 break;
1240         default:
1241                 return (EOPNOTSUPP);
1242         }
1243         kn->kn_hook = (caddr_t)cpipe;
1244
1245         knote_insert(&cpipe->pipe_kq.ki_note, kn);
1246
1247         return (0);
1248 }
1249
1250 static void
1251 filt_pipedetach(struct knote *kn)
1252 {
1253         struct pipe *cpipe = (struct pipe *)kn->kn_hook;
1254
1255         knote_remove(&cpipe->pipe_kq.ki_note, kn);
1256 }
1257
1258 /*ARGSUSED*/
1259 static int
1260 filt_piperead(struct knote *kn, long hint)
1261 {
1262         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1263         int ready = 0;
1264
1265         lwkt_gettoken(&rpipe->pipe_rlock);
1266         lwkt_gettoken(&rpipe->pipe_wlock);
1267
1268         kn->kn_data = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
1269
1270         if (rpipe->pipe_state & PIPE_REOF) {
1271                 /*
1272                  * Only set NODATA if all data has been exhausted
1273                  */
1274                 if (kn->kn_data == 0)
1275                         kn->kn_flags |= EV_NODATA;
1276                 kn->kn_flags |= EV_EOF;
1277                 ready = 1;
1278         }
1279
1280         lwkt_reltoken(&rpipe->pipe_wlock);
1281         lwkt_reltoken(&rpipe->pipe_rlock);
1282
1283         if (!ready)
1284                 ready = kn->kn_data > 0;
1285
1286         return (ready);
1287 }
1288
1289 /*ARGSUSED*/
1290 static int
1291 filt_pipewrite(struct knote *kn, long hint)
1292 {
1293         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1294         struct pipe *wpipe = rpipe->pipe_peer;
1295         int ready = 0;
1296
1297         kn->kn_data = 0;
1298         if (wpipe == NULL) {
1299                 kn->kn_flags |= (EV_EOF | EV_NODATA);
1300                 return (1);
1301         }
1302
1303         lwkt_gettoken(&wpipe->pipe_rlock);
1304         lwkt_gettoken(&wpipe->pipe_wlock);
1305
1306         if (wpipe->pipe_state & PIPE_WEOF) {
1307                 kn->kn_flags |= (EV_EOF | EV_NODATA);
1308                 ready = 1;
1309         }
1310
1311         if (!ready)
1312                 kn->kn_data = wpipe->pipe_buffer.size -
1313                               (wpipe->pipe_buffer.windex -
1314                                wpipe->pipe_buffer.rindex);
1315
1316         lwkt_reltoken(&wpipe->pipe_wlock);
1317         lwkt_reltoken(&wpipe->pipe_rlock);
1318
1319         if (!ready)
1320                 ready = kn->kn_data >= PIPE_BUF;
1321
1322         return (ready);
1323 }