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/select.h>
  40 #include <sys/signalvar.h>
  41 #include <sys/sysproto.h>
  42 #include <sys/pipe.h>
  43 #include <sys/vnode.h>
  44 #include <sys/uio.h>
  45 #include <sys/event.h>
  46 #include <sys/globaldata.h>
  47 #include <sys/module.h>
  48 #include <sys/malloc.h>
  49 #include <sys/sysctl.h>
  50 #include <sys/socket.h>
  51
  52 #include <vm/vm.h>
  53 #include <vm/vm_param.h>
  54 #include <sys/lock.h>
  55 #include <vm/vm_object.h>
  56 #include <vm/vm_kern.h>
  57 #include <vm/vm_extern.h>
  58 #include <vm/pmap.h>
  59 #include <vm/vm_map.h>
  60 #include <vm/vm_page.h>
  61 #include <vm/vm_zone.h>
  62
  63 #include <sys/file2.h>
  64 #include <sys/signal2.h>
  65 #include <sys/mplock2.h>
  66
  67 #include <machine/cpufunc.h>
  68
  69 /*
  70  * interfaces to the outside world
  71  */
  72 static int pipe_read (struct file *fp, struct uio *uio,
  73                 struct ucred *cred, int flags);
  74 static int pipe_write (struct file *fp, struct uio *uio,
  75                 struct ucred *cred, int flags);
  76 static int pipe_close (struct file *fp);
  77 static int pipe_shutdown (struct file *fp, int how);
  78 static int pipe_kqfilter (struct file *fp, struct knote *kn);
  79 static int pipe_stat (struct file *fp, struct stat *sb, struct ucred *cred);
  80 static int pipe_ioctl (struct file *fp, u_long cmd, caddr_t data,
  81                 struct ucred *cred, struct sysmsg *msg);
  82
  83 static struct fileops pipeops = {
  84         .fo_read = pipe_read,
  85         .fo_write = pipe_write,
  86         .fo_ioctl = pipe_ioctl,
  87         .fo_kqfilter = pipe_kqfilter,
  88         .fo_stat = pipe_stat,
  89         .fo_close = pipe_close,
  90         .fo_shutdown = pipe_shutdown
  91 };
  92
  93 static void     filt_pipedetach(struct knote *kn);
  94 static int      filt_piperead(struct knote *kn, long hint);
  95 static int      filt_pipewrite(struct knote *kn, long hint);
  96
  97 static struct filterops pipe_rfiltops =
  98         { 1, NULL, filt_pipedetach, filt_piperead };
  99 static struct filterops pipe_wfiltops =
 100         { 1, NULL, filt_pipedetach, filt_pipewrite };
 101
 102 MALLOC_DEFINE(M_PIPE, "pipe", "pipe structures");
 103
 104 /*
 105  * Default pipe buffer size(s), this can be kind-of large now because pipe
 106  * space is pageable.  The pipe code will try to maintain locality of
 107  * reference for performance reasons, so small amounts of outstanding I/O
 108  * will not wipe the cache.
 109  */
 110 #define MINPIPESIZE (PIPE_SIZE/3)
 111 #define MAXPIPESIZE (2*PIPE_SIZE/3)
 112
 113 /*
 114  * Limit the number of "big" pipes
 115  */
 116 #define LIMITBIGPIPES   64
 117 #define PIPEQ_MAX_CACHE 16      /* per-cpu pipe structure cache */
 118
 119 static int pipe_maxbig = LIMITBIGPIPES;
 120 static int pipe_maxcache = PIPEQ_MAX_CACHE;
 121 static int pipe_bigcount;
 122 static int pipe_nbig;
 123 static int pipe_bcache_alloc;
 124 static int pipe_bkmem_alloc;
 125 static int pipe_rblocked_count;
 126 static int pipe_wblocked_count;
 127
 128 SYSCTL_NODE(_kern, OID_AUTO, pipe, CTLFLAG_RW, 0, "Pipe operation");
 129 SYSCTL_INT(_kern_pipe, OID_AUTO, nbig,
 130         CTLFLAG_RD, &pipe_nbig, 0, "numer of big pipes allocated");
 131 SYSCTL_INT(_kern_pipe, OID_AUTO, bigcount,
 132         CTLFLAG_RW, &pipe_bigcount, 0, "number of times pipe expanded");
 133 SYSCTL_INT(_kern_pipe, OID_AUTO, rblocked,
 134         CTLFLAG_RW, &pipe_rblocked_count, 0, "number of times pipe expanded");
 135 SYSCTL_INT(_kern_pipe, OID_AUTO, wblocked,
 136         CTLFLAG_RW, &pipe_wblocked_count, 0, "number of times pipe expanded");
 137 SYSCTL_INT(_kern_pipe, OID_AUTO, maxcache,
 138         CTLFLAG_RW, &pipe_maxcache, 0, "max pipes cached per-cpu");
 139 SYSCTL_INT(_kern_pipe, OID_AUTO, maxbig,
 140         CTLFLAG_RW, &pipe_maxbig, 0, "max number of big pipes");
 141 #ifdef SMP
 142 static int pipe_delay = 5000;   /* 5uS default */
 143 SYSCTL_INT(_kern_pipe, OID_AUTO, delay,
 144         CTLFLAG_RW, &pipe_delay, 0, "SMP delay optimization in ns");
 145 static int pipe_mpsafe = 1;
 146 SYSCTL_INT(_kern_pipe, OID_AUTO, mpsafe,
 147         CTLFLAG_RW, &pipe_mpsafe, 0, "");
 148 #endif
 149 #if !defined(NO_PIPE_SYSCTL_STATS)
 150 SYSCTL_INT(_kern_pipe, OID_AUTO, bcache_alloc,
 151         CTLFLAG_RW, &pipe_bcache_alloc, 0, "pipe buffer from pcpu cache");
 152 SYSCTL_INT(_kern_pipe, OID_AUTO, bkmem_alloc,
 153         CTLFLAG_RW, &pipe_bkmem_alloc, 0, "pipe buffer from kmem");
 154 #endif
 155
 156 static void pipeclose (struct pipe *cpipe);
 157 static void pipe_free_kmem (struct pipe *cpipe);
 158 static int pipe_create (struct pipe **cpipep);
 159 static __inline void pipeselwakeup (struct pipe *cpipe);
 160 static int pipespace (struct pipe *cpipe, int size);
 161
 162 static __inline int
 163 pipeseltest(struct pipe *cpipe)
 164 {
 165         return ((cpipe->pipe_state & PIPE_SEL) ||
 166                 ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio) ||
 167                 SLIST_FIRST(&cpipe->pipe_sel.si_note));
 168 }
 169
 170 static __inline void
 171 pipeselwakeup(struct pipe *cpipe)
 172 {
 173         if (cpipe->pipe_state & PIPE_SEL) {
 174                 get_mplock();
 175                 cpipe->pipe_state &= ~PIPE_SEL;
 176                 selwakeup(&cpipe->pipe_sel);
 177                 rel_mplock();
 178         }
 179         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio) {
 180                 get_mplock();
 181                 pgsigio(cpipe->pipe_sigio, SIGIO, 0);
 182                 rel_mplock();
 183         }
 184         if (SLIST_FIRST(&cpipe->pipe_sel.si_note)) {
 185                 get_mplock();
 186                 KNOTE(&cpipe->pipe_sel.si_note, 0);
 187                 rel_mplock();
 188         }
 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 static __inline void
 228 pipe_get_mplock(int *save)
 229 {
 230 #ifdef SMP
 231         if (pipe_mpsafe == 0) {
 232                 get_mplock();
 233                 *save = 1;
 234         } else
 235 #endif
 236         {
 237                 *save = 0;
 238         }
 239 }
 240
 241 static __inline void
 242 pipe_rel_mplock(int *save)
 243 {
 244 #ifdef SMP
 245         if (*save)
 246                 rel_mplock();
 247 #endif
 248 }
 249
 250
 251 /*
 252  * The pipe system call for the DTYPE_PIPE type of pipes
 253  *
 254  * pipe_args(int dummy)
 255  *
 256  * MPSAFE
 257  */
 258 int
 259 sys_pipe(struct pipe_args *uap)
 260 {
 261         struct thread *td = curthread;
 262         struct filedesc *fdp = td->td_proc->p_fd;
 263         struct file *rf, *wf;
 264         struct pipe *rpipe, *wpipe;
 265         int fd1, fd2, error;
 266
 267         rpipe = wpipe = NULL;
 268         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
 269                 pipeclose(rpipe);
 270                 pipeclose(wpipe);
 271                 return (ENFILE);
 272         }
 273
 274         error = falloc(td->td_lwp, &rf, &fd1);
 275         if (error) {
 276                 pipeclose(rpipe);
 277                 pipeclose(wpipe);
 278                 return (error);
 279         }
 280         uap->sysmsg_fds[0] = fd1;
 281
 282         /*
 283          * Warning: once we've gotten past allocation of the fd for the
 284          * read-side, we can only drop the read side via fdrop() in order
 285          * to avoid races against processes which manage to dup() the read
 286          * side while we are blocked trying to allocate the write side.
 287          */
 288         rf->f_type = DTYPE_PIPE;
 289         rf->f_flag = FREAD | FWRITE;
 290         rf->f_ops = &pipeops;
 291         rf->f_data = rpipe;
 292         error = falloc(td->td_lwp, &wf, &fd2);
 293         if (error) {
 294                 fsetfd(fdp, NULL, fd1);
 295                 fdrop(rf);
 296                 /* rpipe has been closed by fdrop(). */
 297                 pipeclose(wpipe);
 298                 return (error);
 299         }
 300         wf->f_type = DTYPE_PIPE;
 301         wf->f_flag = FREAD | FWRITE;
 302         wf->f_ops = &pipeops;
 303         wf->f_data = wpipe;
 304         uap->sysmsg_fds[1] = fd2;
 305
 306         rpipe->pipe_slock = kmalloc(sizeof(struct lock),
 307                                     M_PIPE, M_WAITOK|M_ZERO);
 308         wpipe->pipe_slock = rpipe->pipe_slock;
 309         rpipe->pipe_peer = wpipe;
 310         wpipe->pipe_peer = rpipe;
 311         lockinit(rpipe->pipe_slock, "pipecl", 0, 0);
 312
 313         /*
 314          * Once activated the peer relationship remains valid until
 315          * both sides are closed.
 316          */
 317         fsetfd(fdp, rf, fd1);
 318         fsetfd(fdp, wf, fd2);
 319         fdrop(rf);
 320         fdrop(wf);
 321
 322         return (0);
 323 }
 324
 325 /*
 326  * Allocate kva for pipe circular buffer, the space is pageable
 327  * This routine will 'realloc' the size of a pipe safely, if it fails
 328  * it will retain the old buffer.
 329  * If it fails it will return ENOMEM.
 330  */
 331 static int
 332 pipespace(struct pipe *cpipe, int size)
 333 {
 334         struct vm_object *object;
 335         caddr_t buffer;
 336         int npages, error;
 337
 338         npages = round_page(size) / PAGE_SIZE;
 339         object = cpipe->pipe_buffer.object;
 340
 341         /*
 342          * [re]create the object if necessary and reserve space for it
 343          * in the kernel_map.  The object and memory are pageable.  On
 344          * success, free the old resources before assigning the new
 345          * ones.
 346          */
 347         if (object == NULL || object->size != npages) {
 348                 get_mplock();
 349                 object = vm_object_allocate(OBJT_DEFAULT, npages);
 350                 buffer = (caddr_t)vm_map_min(&kernel_map);
 351
 352                 error = vm_map_find(&kernel_map, object, 0,
 353                                     (vm_offset_t *)&buffer,
 354                                     size, PAGE_SIZE,
 355                                     1, VM_MAPTYPE_NORMAL,
 356                                     VM_PROT_ALL, VM_PROT_ALL,
 357                                     0);
 358
 359                 if (error != KERN_SUCCESS) {
 360                         vm_object_deallocate(object);
 361                         rel_mplock();
 362                         return (ENOMEM);
 363                 }
 364                 pipe_free_kmem(cpipe);
 365                 rel_mplock();
 366                 cpipe->pipe_buffer.object = object;
 367                 cpipe->pipe_buffer.buffer = buffer;
 368                 cpipe->pipe_buffer.size = size;
 369                 ++pipe_bkmem_alloc;
 370         } else {
 371                 ++pipe_bcache_alloc;
 372         }
 373         cpipe->pipe_buffer.rindex = 0;
 374         cpipe->pipe_buffer.windex = 0;
 375         return (0);
 376 }
 377
 378 /*
 379  * Initialize and allocate VM and memory for pipe, pulling the pipe from
 380  * our per-cpu cache if possible.  For now make sure it is sized for the
 381  * smaller PIPE_SIZE default.
 382  */
 383 static int
 384 pipe_create(struct pipe **cpipep)
 385 {
 386         globaldata_t gd = mycpu;
 387         struct pipe *cpipe;
 388         int error;
 389
 390         if ((cpipe = gd->gd_pipeq) != NULL) {
 391                 gd->gd_pipeq = cpipe->pipe_peer;
 392                 --gd->gd_pipeqcount;
 393                 cpipe->pipe_peer = NULL;
 394                 cpipe->pipe_wantwcnt = 0;
 395         } else {
 396                 cpipe = kmalloc(sizeof(struct pipe), M_PIPE, M_WAITOK|M_ZERO);
 397         }
 398         *cpipep = cpipe;
 399         if ((error = pipespace(cpipe, PIPE_SIZE)) != 0)
 400                 return (error);
 401         vfs_timestamp(&cpipe->pipe_ctime);
 402         cpipe->pipe_atime = cpipe->pipe_ctime;
 403         cpipe->pipe_mtime = cpipe->pipe_ctime;
 404         lwkt_token_init(&cpipe->pipe_rlock, 1);
 405         lwkt_token_init(&cpipe->pipe_wlock, 1);
 406         return (0);
 407 }
 408
 409 /*
 410  * MPALMOSTSAFE (acquires mplock)
 411  */
 412 static int
 413 pipe_read(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 414 {
 415         struct pipe *rpipe;
 416         int error;
 417         size_t nread = 0;
 418         int nbio;
 419         u_int size;     /* total bytes available */
 420         u_int nsize;    /* total bytes to read */
 421         u_int rindex;   /* contiguous bytes available */
 422         int notify_writer;
 423         int mpsave;
 424         int bigread;
 425         int bigcount;
 426
 427         if (uio->uio_resid == 0)
 428                 return(0);
 429
 430         /*
 431          * Setup locks, calculate nbio
 432          */
 433         pipe_get_mplock(&mpsave);
 434         rpipe = (struct pipe *)fp->f_data;
 435         lwkt_gettoken(&rpipe->pipe_rlock);
 436
 437         if (fflags & O_FBLOCKING)
 438                 nbio = 0;
 439         else if (fflags & O_FNONBLOCKING)
 440                 nbio = 1;
 441         else if (fp->f_flag & O_NONBLOCK)
 442                 nbio = 1;
 443         else
 444                 nbio = 0;
 445
 446         /*
 447          * Reads are serialized.  Note howeverthat pipe_buffer.buffer and
 448          * pipe_buffer.size can change out from under us when the number
 449          * of bytes in the buffer are zero due to the write-side doing a
 450          * pipespace().
 451          */
 452         error = pipe_start_uio(rpipe, &rpipe->pipe_rip);
 453         if (error) {
 454                 pipe_rel_mplock(&mpsave);
 455                 lwkt_reltoken(&rpipe->pipe_rlock);
 456                 return (error);
 457         }
 458         notify_writer = 0;
 459
 460         bigread = (uio->uio_resid > 10 * 1024 * 1024);
 461         bigcount = 10;
 462
 463         while (uio->uio_resid) {
 464                 /*
 465                  * Don't hog the cpu.
 466                  */
 467                 if (bigread && --bigcount == 0) {
 468                         lwkt_user_yield();
 469                         bigcount = 10;
 470                         if (CURSIG(curthread->td_lwp)) {
 471                                 error = EINTR;
 472                                 break;
 473                         }
 474                 }
 475
 476                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 477                 cpu_lfence();
 478                 if (size) {
 479                         rindex = rpipe->pipe_buffer.rindex &
 480                                  (rpipe->pipe_buffer.size - 1);
 481                         nsize = size;
 482                         if (nsize > rpipe->pipe_buffer.size - rindex)
 483                                 nsize = rpipe->pipe_buffer.size - rindex;
 484                         nsize = szmin(nsize, uio->uio_resid);
 485
 486                         error = uiomove(&rpipe->pipe_buffer.buffer[rindex],
 487                                         nsize, uio);
 488                         if (error)
 489                                 break;
 490                         cpu_mfence();
 491                         rpipe->pipe_buffer.rindex += nsize;
 492                         nread += nsize;
 493
 494                         /*
 495                          * If the FIFO is still over half full just continue
 496                          * and do not try to notify the writer yet.
 497                          */
 498                         if (size - nsize >= (rpipe->pipe_buffer.size >> 1)) {
 499                                 notify_writer = 0;
 500                                 continue;
 501                         }
 502
 503                         /*
 504                          * When the FIFO is less then half full notify any
 505                          * waiting writer.  WANTW can be checked while
 506                          * holding just the rlock.
 507                          */
 508                         notify_writer = 1;
 509                         if ((rpipe->pipe_state & PIPE_WANTW) == 0)
 510                                 continue;
 511                 }
 512
 513                 /*
 514                  * If the "write-side" was blocked we wake it up.  This code
 515                  * is reached either when the buffer is completely emptied
 516                  * or if it becomes more then half-empty.
 517                  *
 518                  * Pipe_state can only be modified if both the rlock and
 519                  * wlock are held.
 520                  */
 521                 if (rpipe->pipe_state & PIPE_WANTW) {
 522                         lwkt_gettoken(&rpipe->pipe_wlock);
 523                         if (rpipe->pipe_state & PIPE_WANTW) {
 524                                 notify_writer = 0;
 525                                 rpipe->pipe_state &= ~PIPE_WANTW;
 526                                 lwkt_reltoken(&rpipe->pipe_wlock);
 527                                 wakeup(rpipe);
 528                         } else {
 529                                 lwkt_reltoken(&rpipe->pipe_wlock);
 530                         }
 531                 }
 532
 533                 /*
 534                  * Pick up our copy loop again if the writer sent data to
 535                  * us while we were messing around.
 536                  *
 537                  * On a SMP box poll up to pipe_delay nanoseconds for new
 538                  * data.  Typically a value of 2000 to 4000 is sufficient
 539                  * to eradicate most IPIs/tsleeps/wakeups when a pipe
 540                  * is used for synchronous communications with small packets,
 541                  * and 8000 or so (8uS) will pipeline large buffer xfers
 542                  * between cpus over a pipe.
 543                  *
 544                  * For synchronous communications a hit means doing a
 545                  * full Awrite-Bread-Bwrite-Aread cycle in less then 2uS,
 546                  * where as miss requiring a tsleep/wakeup sequence
 547                  * will take 7uS or more.
 548                  */
 549                 if (rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex)
 550                         continue;
 551
 552 #if defined(SMP) && defined(_RDTSC_SUPPORTED_)
 553                 if (pipe_delay) {
 554                         int64_t tsc_target;
 555                         int good = 0;
 556
 557                         tsc_target = tsc_get_target(pipe_delay);
 558                         while (tsc_test_target(tsc_target) == 0) {
 559                                 if (rpipe->pipe_buffer.windex !=
 560                                     rpipe->pipe_buffer.rindex) {
 561                                         good = 1;
 562                                         break;
 563                                 }
 564                         }
 565                         if (good)
 566                                 continue;
 567                 }
 568 #endif
 569
 570                 /*
 571                  * Detect EOF condition, do not set error.
 572                  */
 573                 if (rpipe->pipe_state & PIPE_REOF)
 574                         break;
 575
 576                 /*
 577                  * Break if some data was read, or if this was a non-blocking
 578                  * read.
 579                  */
 580                 if (nread > 0)
 581                         break;
 582
 583                 if (nbio) {
 584                         error = EAGAIN;
 585                         break;
 586                 }
 587
 588                 /*
 589                  * Last chance, interlock with WANTR.
 590                  */
 591                 lwkt_gettoken(&rpipe->pipe_wlock);
 592                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 593                 if (size) {
 594                         lwkt_reltoken(&rpipe->pipe_wlock);
 595                         continue;
 596                 }
 597
 598                 /*
 599                  * Retest EOF - acquiring a new token can temporarily release
 600                  * tokens already held.
 601                  */
 602                 if (rpipe->pipe_state & PIPE_REOF) {
 603                         lwkt_reltoken(&rpipe->pipe_wlock);
 604                         break;
 605                 }
 606
 607                 /*
 608                  * If there is no more to read in the pipe, reset its
 609                  * pointers to the beginning.  This improves cache hit
 610                  * stats.
 611                  *
 612                  * We need both locks to modify both pointers, and there
 613                  * must also not be a write in progress or the uiomove()
 614                  * in the write might block and temporarily release
 615                  * its wlock, then reacquire and update windex.  We are
 616                  * only serialized against reads, not writes.
 617                  *
 618                  * XXX should we even bother resetting the indices?  It
 619                  *     might actually be more cache efficient not to.
 620                  */
 621                 if (rpipe->pipe_buffer.rindex == rpipe->pipe_buffer.windex &&
 622                     rpipe->pipe_wip == 0) {
 623                         rpipe->pipe_buffer.rindex = 0;
 624                         rpipe->pipe_buffer.windex = 0;
 625                 }
 626
 627                 /*
 628                  * Wait for more data.
 629                  *
 630                  * Pipe_state can only be set if both the rlock and wlock
 631                  * are held.
 632                  */
 633                 rpipe->pipe_state |= PIPE_WANTR;
 634                 tsleep_interlock(rpipe, PCATCH);
 635                 lwkt_reltoken(&rpipe->pipe_wlock);
 636                 error = tsleep(rpipe, PCATCH | PINTERLOCKED, "piperd", 0);
 637                 ++pipe_rblocked_count;
 638                 if (error)
 639                         break;
 640         }
 641         pipe_end_uio(rpipe, &rpipe->pipe_rip);
 642
 643         /*
 644          * Uptime last access time
 645          */
 646         if (error == 0 && nread)
 647                 vfs_timestamp(&rpipe->pipe_atime);
 648
 649         /*
 650          * If we drained the FIFO more then half way then handle
 651          * write blocking hysteresis.
 652          *
 653          * Note that PIPE_WANTW cannot be set by the writer without
 654          * it holding both rlock and wlock, so we can test it
 655          * while holding just rlock.
 656          */
 657         if (notify_writer) {
 658                 if (rpipe->pipe_state & PIPE_WANTW) {
 659                         lwkt_gettoken(&rpipe->pipe_wlock);
 660                         if (rpipe->pipe_state & PIPE_WANTW) {
 661                                 rpipe->pipe_state &= ~PIPE_WANTW;
 662                                 lwkt_reltoken(&rpipe->pipe_wlock);
 663                                 wakeup(rpipe);
 664                         } else {
 665                                 lwkt_reltoken(&rpipe->pipe_wlock);
 666                         }
 667                 }
 668                 if (pipeseltest(rpipe)) {
 669                         lwkt_gettoken(&rpipe->pipe_wlock);
 670                         pipeselwakeup(rpipe);
 671                         lwkt_reltoken(&rpipe->pipe_wlock);
 672                 }
 673         }
 674         /*size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;*/
 675         lwkt_reltoken(&rpipe->pipe_rlock);
 676
 677         pipe_rel_mplock(&mpsave);
 678         return (error);
 679 }
 680
 681 /*
 682  * MPALMOSTSAFE - acquires mplock
 683  */
 684 static int
 685 pipe_write(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 686 {
 687         int error;
 688         int orig_resid;
 689         int nbio;
 690         struct pipe *wpipe, *rpipe;
 691         u_int windex;
 692         u_int space;
 693         u_int wcount;
 694         int mpsave;
 695         int bigwrite;
 696         int bigcount;
 697
 698         pipe_get_mplock(&mpsave);
 699
 700         /*
 701          * Writes go to the peer.  The peer will always exist.
 702          */
 703         rpipe = (struct pipe *) fp->f_data;
 704         wpipe = rpipe->pipe_peer;
 705         lwkt_gettoken(&wpipe->pipe_wlock);
 706         if (wpipe->pipe_state & PIPE_WEOF) {
 707                 pipe_rel_mplock(&mpsave);
 708                 lwkt_reltoken(&wpipe->pipe_wlock);
 709                 return (EPIPE);
 710         }
 711
 712         /*
 713          * Degenerate case (EPIPE takes prec)
 714          */
 715         if (uio->uio_resid == 0) {
 716                 pipe_rel_mplock(&mpsave);
 717                 lwkt_reltoken(&wpipe->pipe_wlock);
 718                 return(0);
 719         }
 720
 721         /*
 722          * Writes are serialized (start_uio must be called with wlock)
 723          */
 724         error = pipe_start_uio(wpipe, &wpipe->pipe_wip);
 725         if (error) {
 726                 pipe_rel_mplock(&mpsave);
 727                 lwkt_reltoken(&wpipe->pipe_wlock);
 728                 return (error);
 729         }
 730
 731         if (fflags & O_FBLOCKING)
 732                 nbio = 0;
 733         else if (fflags & O_FNONBLOCKING)
 734                 nbio = 1;
 735         else if (fp->f_flag & O_NONBLOCK)
 736                 nbio = 1;
 737         else
 738                 nbio = 0;
 739
 740         /*
 741          * If it is advantageous to resize the pipe buffer, do
 742          * so.  We are write-serialized so we can block safely.
 743          */
 744         if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 745             (pipe_nbig < pipe_maxbig) &&
 746             wpipe->pipe_wantwcnt > 4 &&
 747             (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 748                 /*
 749                  * Recheck after lock.
 750                  */
 751                 lwkt_gettoken(&wpipe->pipe_rlock);
 752                 if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 753                     (pipe_nbig < pipe_maxbig) &&
 754                     (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 755                         atomic_add_int(&pipe_nbig, 1);
 756                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
 757                                 ++pipe_bigcount;
 758                         else
 759                                 atomic_subtract_int(&pipe_nbig, 1);
 760                 }
 761                 lwkt_reltoken(&wpipe->pipe_rlock);
 762         }
 763
 764         orig_resid = uio->uio_resid;
 765         wcount = 0;
 766
 767         bigwrite = (uio->uio_resid > 10 * 1024 * 1024);
 768         bigcount = 10;
 769
 770         while (uio->uio_resid) {
 771                 if (wpipe->pipe_state & PIPE_WEOF) {
 772                         error = EPIPE;
 773                         break;
 774                 }
 775
 776                 /*
 777                  * Don't hog the cpu.
 778                  */
 779                 if (bigwrite && --bigcount == 0) {
 780                         lwkt_user_yield();
 781                         bigcount = 10;
 782                         if (CURSIG(curthread->td_lwp)) {
 783                                 error = EINTR;
 784                                 break;
 785                         }
 786                 }
 787
 788                 windex = wpipe->pipe_buffer.windex &
 789                          (wpipe->pipe_buffer.size - 1);
 790                 space = wpipe->pipe_buffer.size -
 791                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 792                 cpu_lfence();
 793
 794                 /* Writes of size <= PIPE_BUF must be atomic. */
 795                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 796                         space = 0;
 797
 798                 /*
 799                  * Write to fill, read size handles write hysteresis.  Also
 800                  * additional restrictions can cause select-based non-blocking
 801                  * writes to spin.
 802                  */
 803                 if (space > 0) {
 804                         u_int segsize;
 805
 806                         /*
 807                          * Transfer size is minimum of uio transfer
 808                          * and free space in pipe buffer.
 809                          *
 810                          * Limit each uiocopy to no more then PIPE_SIZE
 811                          * so we can keep the gravy train going on a
 812                          * SMP box.  This doubles the performance for
 813                          * write sizes > 16K.  Otherwise large writes
 814                          * wind up doing an inefficient synchronous
 815                          * ping-pong.
 816                          */
 817                         space = szmin(space, uio->uio_resid);
 818                         if (space > PIPE_SIZE)
 819                                 space = PIPE_SIZE;
 820
 821                         /*
 822                          * First segment to transfer is minimum of
 823                          * transfer size and contiguous space in
 824                          * pipe buffer.  If first segment to transfer
 825                          * is less than the transfer size, we've got
 826                          * a wraparound in the buffer.
 827                          */
 828                         segsize = wpipe->pipe_buffer.size - windex;
 829                         if (segsize > space)
 830                                 segsize = space;
 831
 832 #ifdef SMP
 833                         /*
 834                          * If this is the first loop and the reader is
 835                          * blocked, do a preemptive wakeup of the reader.
 836                          *
 837                          * On SMP the IPI latency plus the wlock interlock
 838                          * on the reader side is the fastest way to get the
 839                          * reader going.  (The scheduler will hard loop on
 840                          * lock tokens).
 841                          *
 842                          * NOTE: We can't clear WANTR here without acquiring
 843                          * the rlock, which we don't want to do here!
 844                          */
 845                         if ((wpipe->pipe_state & PIPE_WANTR) && pipe_mpsafe > 1)
 846                                 wakeup(wpipe);
 847 #endif
 848
 849                         /*
 850                          * Transfer segment, which may include a wrap-around.
 851                          * Update windex to account for both all in one go
 852                          * so the reader can read() the data atomically.
 853                          */
 854                         error = uiomove(&wpipe->pipe_buffer.buffer[windex],
 855                                         segsize, uio);
 856                         if (error == 0 && segsize < space) {
 857                                 segsize = space - segsize;
 858                                 error = uiomove(&wpipe->pipe_buffer.buffer[0],
 859                                                 segsize, uio);
 860                         }
 861                         if (error)
 862                                 break;
 863                         cpu_mfence();
 864                         wpipe->pipe_buffer.windex += space;
 865                         wcount += space;
 866                         continue;
 867                 }
 868
 869                 /*
 870                  * We need both the rlock and the wlock to interlock against
 871                  * the EOF, WANTW, and size checks, and to modify pipe_state.
 872                  *
 873                  * These are token locks so we do not have to worry about
 874                  * deadlocks.
 875                  */
 876                 lwkt_gettoken(&wpipe->pipe_rlock);
 877
 878                 /*
 879                  * If the "read-side" has been blocked, wake it up now
 880                  * and yield to let it drain synchronously rather
 881                  * then block.
 882                  */
 883                 if (wpipe->pipe_state & PIPE_WANTR) {
 884                         wpipe->pipe_state &= ~PIPE_WANTR;
 885                         wakeup(wpipe);
 886                 }
 887
 888                 /*
 889                  * don't block on non-blocking I/O
 890                  */
 891                 if (nbio) {
 892                         lwkt_reltoken(&wpipe->pipe_rlock);
 893                         error = EAGAIN;
 894                         break;
 895                 }
 896
 897                 /*
 898                  * re-test whether we have to block in the writer after
 899                  * acquiring both locks, in case the reader opened up
 900                  * some space.
 901                  */
 902                 space = wpipe->pipe_buffer.size -
 903                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 904                 cpu_lfence();
 905                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 906                         space = 0;
 907
 908                 /*
 909                  * Retest EOF - acquiring a new token can temporarily release
 910                  * tokens already held.
 911                  */
 912                 if (wpipe->pipe_state & PIPE_WEOF) {
 913                         lwkt_reltoken(&wpipe->pipe_rlock);
 914                         error = EPIPE;
 915                         break;
 916                 }
 917
 918                 /*
 919                  * We have no more space and have something to offer,
 920                  * wake up select/poll.
 921                  */
 922                 if (space == 0) {
 923                         wpipe->pipe_state |= PIPE_WANTW;
 924                         ++wpipe->pipe_wantwcnt;
 925                         pipeselwakeup(wpipe);
 926                         if (wpipe->pipe_state & PIPE_WANTW)
 927                                 error = tsleep(wpipe, PCATCH, "pipewr", 0);
 928                         ++pipe_wblocked_count;
 929                 }
 930                 lwkt_reltoken(&wpipe->pipe_rlock);
 931
 932                 /*
 933                  * Break out if we errored or the read side wants us to go
 934                  * away.
 935                  */
 936                 if (error)
 937                         break;
 938                 if (wpipe->pipe_state & PIPE_WEOF) {
 939                         error = EPIPE;
 940                         break;
 941                 }
 942         }
 943         pipe_end_uio(wpipe, &wpipe->pipe_wip);
 944
 945         /*
 946          * If we have put any characters in the buffer, we wake up
 947          * the reader.
 948          *
 949          * Both rlock and wlock are required to be able to modify pipe_state.
 950          */
 951         if (wpipe->pipe_buffer.windex != wpipe->pipe_buffer.rindex) {
 952                 if (wpipe->pipe_state & PIPE_WANTR) {
 953                         lwkt_gettoken(&wpipe->pipe_rlock);
 954                         if (wpipe->pipe_state & PIPE_WANTR) {
 955                                 wpipe->pipe_state &= ~PIPE_WANTR;
 956                                 lwkt_reltoken(&wpipe->pipe_rlock);
 957                                 wakeup(wpipe);
 958                         } else {
 959                                 lwkt_reltoken(&wpipe->pipe_rlock);
 960                         }
 961                 }
 962                 if (pipeseltest(wpipe)) {
 963                         lwkt_gettoken(&wpipe->pipe_rlock);
 964                         pipeselwakeup(wpipe);
 965                         lwkt_reltoken(&wpipe->pipe_rlock);
 966                 }
 967         }
 968
 969         /*
 970          * Don't return EPIPE if I/O was successful
 971          */
 972         if ((wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex) &&
 973             (uio->uio_resid == 0) &&
 974             (error == EPIPE)) {
 975                 error = 0;
 976         }
 977
 978         if (error == 0)
 979                 vfs_timestamp(&wpipe->pipe_mtime);
 980
 981         /*
 982          * We have something to offer,
 983          * wake up select/poll.
 984          */
 985         /*space = wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex;*/
 986         lwkt_reltoken(&wpipe->pipe_wlock);
 987         pipe_rel_mplock(&mpsave);
 988         return (error);
 989 }
 990
 991 /*
 992  * MPALMOSTSAFE - acquires mplock
 993  *
 994  * we implement a very minimal set of ioctls for compatibility with sockets.
 995  */
 996 int
 997 pipe_ioctl(struct file *fp, u_long cmd, caddr_t data,
 998            struct ucred *cred, struct sysmsg *msg)
 999 {
1000         struct pipe *mpipe;
1001         int error;
1002         int mpsave;
1003
1004         pipe_get_mplock(&mpsave);
1005         mpipe = (struct pipe *)fp->f_data;
1006
1007         lwkt_gettoken(&mpipe->pipe_rlock);
1008         lwkt_gettoken(&mpipe->pipe_wlock);
1009
1010         switch (cmd) {
1011         case FIOASYNC:
1012                 if (*(int *)data) {
1013                         mpipe->pipe_state |= PIPE_ASYNC;
1014                 } else {
1015                         mpipe->pipe_state &= ~PIPE_ASYNC;
1016                 }
1017                 error = 0;
1018                 break;
1019         case FIONREAD:
1020                 *(int *)data = mpipe->pipe_buffer.windex -
1021                                 mpipe->pipe_buffer.rindex;
1022                 error = 0;
1023                 break;
1024         case FIOSETOWN:
1025                 get_mplock();
1026                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
1027                 rel_mplock();
1028                 break;
1029         case FIOGETOWN:
1030                 *(int *)data = fgetown(mpipe->pipe_sigio);
1031                 error = 0;
1032                 break;
1033         case TIOCSPGRP:
1034                 /* This is deprecated, FIOSETOWN should be used instead. */
1035                 get_mplock();
1036                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
1037                 rel_mplock();
1038                 break;
1039
1040         case TIOCGPGRP:
1041                 /* This is deprecated, FIOGETOWN should be used instead. */
1042                 *(int *)data = -fgetown(mpipe->pipe_sigio);
1043                 error = 0;
1044                 break;
1045         default:
1046                 error = ENOTTY;
1047                 break;
1048         }
1049         lwkt_reltoken(&mpipe->pipe_wlock);
1050         lwkt_reltoken(&mpipe->pipe_rlock);
1051         pipe_rel_mplock(&mpsave);
1052
1053         return (error);
1054 }
1055
1056 /*
1057  * MPSAFE
1058  */
1059 static int
1060 pipe_stat(struct file *fp, struct stat *ub, struct ucred *cred)
1061 {
1062         struct pipe *pipe;
1063         int mpsave;
1064
1065         pipe_get_mplock(&mpsave);
1066         pipe = (struct pipe *)fp->f_data;
1067
1068         bzero((caddr_t)ub, sizeof(*ub));
1069         ub->st_mode = S_IFIFO;
1070         ub->st_blksize = pipe->pipe_buffer.size;
1071         ub->st_size = pipe->pipe_buffer.windex - pipe->pipe_buffer.rindex;
1072         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
1073         ub->st_atimespec = pipe->pipe_atime;
1074         ub->st_mtimespec = pipe->pipe_mtime;
1075         ub->st_ctimespec = pipe->pipe_ctime;
1076         /*
1077          * Left as 0: st_dev, st_ino, st_nlink, st_uid, st_gid, st_rdev,
1078          * st_flags, st_gen.
1079          * XXX (st_dev, st_ino) should be unique.
1080          */
1081         pipe_rel_mplock(&mpsave);
1082         return (0);
1083 }
1084
1085 /*
1086  * MPALMOSTSAFE - acquires mplock
1087  */
1088 static int
1089 pipe_close(struct file *fp)
1090 {
1091         struct pipe *cpipe;
1092
1093         get_mplock();
1094         cpipe = (struct pipe *)fp->f_data;
1095         fp->f_ops = &badfileops;
1096         fp->f_data = NULL;
1097         funsetown(cpipe->pipe_sigio);
1098         pipeclose(cpipe);
1099         rel_mplock();
1100         return (0);
1101 }
1102
1103 /*
1104  * Shutdown one or both directions of a full-duplex pipe.
1105  *
1106  * MPALMOSTSAFE - acquires mplock
1107  */
1108 static int
1109 pipe_shutdown(struct file *fp, int how)
1110 {
1111         struct pipe *rpipe;
1112         struct pipe *wpipe;
1113         int error = EPIPE;
1114         int mpsave;
1115
1116         pipe_get_mplock(&mpsave);
1117         rpipe = (struct pipe *)fp->f_data;
1118         wpipe = rpipe->pipe_peer;
1119
1120         /*
1121          * We modify pipe_state on both pipes, which means we need
1122          * all four tokens!
1123          */
1124         lwkt_gettoken(&rpipe->pipe_rlock);
1125         lwkt_gettoken(&rpipe->pipe_wlock);
1126         lwkt_gettoken(&wpipe->pipe_rlock);
1127         lwkt_gettoken(&wpipe->pipe_wlock);
1128
1129         switch(how) {
1130         case SHUT_RDWR:
1131         case SHUT_RD:
1132                 rpipe->pipe_state |= PIPE_REOF;         /* my reads */
1133                 rpipe->pipe_state |= PIPE_WEOF;         /* peer writes */
1134                 if (rpipe->pipe_state & PIPE_WANTR) {
1135                         rpipe->pipe_state &= ~PIPE_WANTR;
1136                         wakeup(rpipe);
1137                 }
1138                 if (rpipe->pipe_state & PIPE_WANTW) {
1139                         rpipe->pipe_state &= ~PIPE_WANTW;
1140                         wakeup(rpipe);
1141                 }
1142                 error = 0;
1143                 if (how == SHUT_RD)
1144                         break;
1145                 /* fall through */
1146         case SHUT_WR:
1147                 wpipe->pipe_state |= PIPE_REOF;         /* peer reads */
1148                 wpipe->pipe_state |= PIPE_WEOF;         /* my writes */
1149                 if (wpipe->pipe_state & PIPE_WANTR) {
1150                         wpipe->pipe_state &= ~PIPE_WANTR;
1151                         wakeup(wpipe);
1152                 }
1153                 if (wpipe->pipe_state & PIPE_WANTW) {
1154                         wpipe->pipe_state &= ~PIPE_WANTW;
1155                         wakeup(wpipe);
1156                 }
1157                 error = 0;
1158                 break;
1159         }
1160         pipeselwakeup(rpipe);
1161         pipeselwakeup(wpipe);
1162
1163         lwkt_reltoken(&wpipe->pipe_wlock);
1164         lwkt_reltoken(&wpipe->pipe_rlock);
1165         lwkt_reltoken(&rpipe->pipe_wlock);
1166         lwkt_reltoken(&rpipe->pipe_rlock);
1167
1168         pipe_rel_mplock(&mpsave);
1169         return (error);
1170 }
1171
1172 static void
1173 pipe_free_kmem(struct pipe *cpipe)
1174 {
1175         if (cpipe->pipe_buffer.buffer != NULL) {
1176                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
1177                         atomic_subtract_int(&pipe_nbig, 1);
1178                 kmem_free(&kernel_map,
1179                         (vm_offset_t)cpipe->pipe_buffer.buffer,
1180                         cpipe->pipe_buffer.size);
1181                 cpipe->pipe_buffer.buffer = NULL;
1182                 cpipe->pipe_buffer.object = NULL;
1183         }
1184 }
1185
1186 /*
1187  * Close the pipe.  The slock must be held to interlock against simultanious
1188  * closes.  The rlock and wlock must be held to adjust the pipe_state.
1189  */
1190 static void
1191 pipeclose(struct pipe *cpipe)
1192 {
1193         globaldata_t gd;
1194         struct pipe *ppipe;
1195
1196         if (cpipe == NULL)
1197                 return;
1198
1199         /*
1200          * The slock may not have been allocated yet (close during
1201          * initialization)
1202          *
1203          * We need both the read and write tokens to modify pipe_state.
1204          */
1205         if (cpipe->pipe_slock)
1206                 lockmgr(cpipe->pipe_slock, LK_EXCLUSIVE);
1207         lwkt_gettoken(&cpipe->pipe_rlock);
1208         lwkt_gettoken(&cpipe->pipe_wlock);
1209
1210         /*
1211          * Set our state, wakeup anyone waiting in select, and
1212          * wakeup anyone blocked on our pipe.
1213          */
1214         cpipe->pipe_state |= PIPE_CLOSED | PIPE_REOF | PIPE_WEOF;
1215         pipeselwakeup(cpipe);
1216         if (cpipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1217                 cpipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1218                 wakeup(cpipe);
1219         }
1220
1221         /*
1222          * Disconnect from peer.
1223          */
1224         if ((ppipe = cpipe->pipe_peer) != NULL) {
1225                 lwkt_gettoken(&ppipe->pipe_rlock);
1226                 lwkt_gettoken(&ppipe->pipe_wlock);
1227                 ppipe->pipe_state |= PIPE_REOF | PIPE_WEOF;
1228                 pipeselwakeup(ppipe);
1229                 if (ppipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1230                         ppipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1231                         wakeup(ppipe);
1232                 }
1233                 if (SLIST_FIRST(&ppipe->pipe_sel.si_note)) {
1234                         get_mplock();
1235                         KNOTE(&ppipe->pipe_sel.si_note, 0);
1236                         rel_mplock();
1237                 }
1238                 lwkt_reltoken(&ppipe->pipe_wlock);
1239                 lwkt_reltoken(&ppipe->pipe_rlock);
1240         }
1241
1242         /*
1243          * If the peer is also closed we can free resources for both
1244          * sides, otherwise we leave our side intact to deal with any
1245          * races (since we only have the slock).
1246          */
1247         if (ppipe && (ppipe->pipe_state & PIPE_CLOSED)) {
1248                 cpipe->pipe_peer = NULL;
1249                 ppipe->pipe_peer = NULL;
1250                 ppipe->pipe_slock = NULL;       /* we will free the slock */
1251                 pipeclose(ppipe);
1252                 ppipe = NULL;
1253         }
1254
1255         lwkt_reltoken(&cpipe->pipe_wlock);
1256         lwkt_reltoken(&cpipe->pipe_rlock);
1257         if (cpipe->pipe_slock)
1258                 lockmgr(cpipe->pipe_slock, LK_RELEASE);
1259
1260         /*
1261          * If we disassociated from our peer we can free resources
1262          */
1263         if (ppipe == NULL) {
1264                 gd = mycpu;
1265                 if (cpipe->pipe_slock) {
1266                         kfree(cpipe->pipe_slock, M_PIPE);
1267                         cpipe->pipe_slock = NULL;
1268                 }
1269                 if (gd->gd_pipeqcount >= pipe_maxcache ||
1270                     cpipe->pipe_buffer.size != PIPE_SIZE
1271                 ) {
1272                         pipe_free_kmem(cpipe);
1273                         kfree(cpipe, M_PIPE);
1274                 } else {
1275                         cpipe->pipe_state = 0;
1276                         cpipe->pipe_peer = gd->gd_pipeq;
1277                         gd->gd_pipeq = cpipe;
1278                         ++gd->gd_pipeqcount;
1279                 }
1280         }
1281 }
1282
1283 /*
1284  * MPALMOSTSAFE - acquires mplock
1285  */
1286 static int
1287 pipe_kqfilter(struct file *fp, struct knote *kn)
1288 {
1289         struct pipe *cpipe;
1290
1291         get_mplock();
1292         cpipe = (struct pipe *)kn->kn_fp->f_data;
1293
1294         switch (kn->kn_filter) {
1295         case EVFILT_READ:
1296                 kn->kn_fop = &pipe_rfiltops;
1297                 break;
1298         case EVFILT_WRITE:
1299                 kn->kn_fop = &pipe_wfiltops;
1300                 cpipe = cpipe->pipe_peer;
1301                 if (cpipe == NULL) {
1302                         /* other end of pipe has been closed */
1303                         rel_mplock();
1304                         return (EPIPE);
1305                 }
1306                 break;
1307         default:
1308                 rel_mplock();
1309                 return (EOPNOTSUPP);
1310         }
1311         kn->kn_hook = (caddr_t)cpipe;
1312
1313         SLIST_INSERT_HEAD(&cpipe->pipe_sel.si_note, kn, kn_selnext);
1314         rel_mplock();
1315         return (0);
1316 }
1317
1318 static void
1319 filt_pipedetach(struct knote *kn)
1320 {
1321         struct pipe *cpipe = (struct pipe *)kn->kn_hook;
1322
1323         SLIST_REMOVE(&cpipe->pipe_sel.si_note, kn, knote, kn_selnext);
1324 }
1325
1326 /*ARGSUSED*/
1327 static int
1328 filt_piperead(struct knote *kn, long hint)
1329 {
1330         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1331
1332         kn->kn_data = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
1333
1334         /* XXX RACE */
1335         if (rpipe->pipe_state & PIPE_REOF) {
1336                 kn->kn_flags |= EV_EOF;
1337                 return (1);
1338         }
1339         return (kn->kn_data > 0);
1340 }
1341
1342 /*ARGSUSED*/
1343 static int
1344 filt_pipewrite(struct knote *kn, long hint)
1345 {
1346         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1347         struct pipe *wpipe = rpipe->pipe_peer;
1348         u_int32_t space;
1349
1350         /* XXX RACE */
1351         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_WEOF)) {
1352                 kn->kn_data = 0;
1353                 kn->kn_flags |= EV_EOF;
1354                 return (1);
1355         }
1356         space = wpipe->pipe_buffer.windex -
1357                 wpipe->pipe_buffer.rindex;
1358         space = wpipe->pipe_buffer.size - space;
1359         kn->kn_data = space;
1360         return (kn->kn_data >= PIPE_BUF);
1361 }