sys/kern/sys_pipe.c

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