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, 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, int *ipp)
 209 {
 210         if (*ipp < 0) {
 211                 *ipp = 0;
 212                 wakeup(ipp);
 213         } else {
 214                 KKASSERT(*ipp > 0);
 215                 *ipp = 0;
 216         }
 217 }
 218
 219 static __inline void
 220 pipe_get_mplock(int *save)
 221 {
 222 #ifdef SMP
 223         if (pipe_mpsafe == 0) {
 224                 get_mplock();
 225                 *save = 1;
 226         } else
 227 #endif
 228         {
 229                 *save = 0;
 230         }
 231 }
 232
 233 static __inline void
 234 pipe_rel_mplock(int *save)
 235 {
 236 #ifdef SMP
 237         if (*save)
 238                 rel_mplock();
 239 #endif
 240 }
 241
 242
 243 /*
 244  * The pipe system call for the DTYPE_PIPE type of pipes
 245  *
 246  * pipe_ARgs(int dummy)
 247  */
 248
 249 /* ARGSUSED */
 250 int
 251 sys_pipe(struct pipe_args *uap)
 252 {
 253         struct thread *td = curthread;
 254         struct proc *p = td->td_proc;
 255         struct file *rf, *wf;
 256         struct pipe *rpipe, *wpipe;
 257         int fd1, fd2, error;
 258
 259         KKASSERT(p);
 260
 261         rpipe = wpipe = NULL;
 262         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
 263                 pipeclose(rpipe);
 264                 pipeclose(wpipe);
 265                 return (ENFILE);
 266         }
 267
 268         error = falloc(p, &rf, &fd1);
 269         if (error) {
 270                 pipeclose(rpipe);
 271                 pipeclose(wpipe);
 272                 return (error);
 273         }
 274         uap->sysmsg_fds[0] = fd1;
 275
 276         /*
 277          * Warning: once we've gotten past allocation of the fd for the
 278          * read-side, we can only drop the read side via fdrop() in order
 279          * to avoid races against processes which manage to dup() the read
 280          * side while we are blocked trying to allocate the write side.
 281          */
 282         rf->f_type = DTYPE_PIPE;
 283         rf->f_flag = FREAD | FWRITE;
 284         rf->f_ops = &pipeops;
 285         rf->f_data = rpipe;
 286         error = falloc(p, &wf, &fd2);
 287         if (error) {
 288                 fsetfd(p, NULL, fd1);
 289                 fdrop(rf);
 290                 /* rpipe has been closed by fdrop(). */
 291                 pipeclose(wpipe);
 292                 return (error);
 293         }
 294         wf->f_type = DTYPE_PIPE;
 295         wf->f_flag = FREAD | FWRITE;
 296         wf->f_ops = &pipeops;
 297         wf->f_data = wpipe;
 298         uap->sysmsg_fds[1] = fd2;
 299
 300         rpipe->pipe_slock = kmalloc(sizeof(struct lock),
 301                                     M_PIPE, M_WAITOK|M_ZERO);
 302         wpipe->pipe_slock = rpipe->pipe_slock;
 303         rpipe->pipe_peer = wpipe;
 304         wpipe->pipe_peer = rpipe;
 305         lockinit(rpipe->pipe_slock, "pipecl", 0, 0);
 306
 307         /*
 308          * Once activated the peer relationship remains valid until
 309          * both sides are closed.
 310          */
 311         fsetfd(p, rf, fd1);
 312         fsetfd(p, wf, fd2);
 313         fdrop(rf);
 314         fdrop(wf);
 315
 316         return (0);
 317 }
 318
 319 /*
 320  * Allocate kva for pipe circular buffer, the space is pageable
 321  * This routine will 'realloc' the size of a pipe safely, if it fails
 322  * it will retain the old buffer.
 323  * If it fails it will return ENOMEM.
 324  */
 325 static int
 326 pipespace(struct pipe *cpipe, int size)
 327 {
 328         struct vm_object *object;
 329         caddr_t buffer;
 330         int npages, error;
 331
 332         npages = round_page(size) / PAGE_SIZE;
 333         object = cpipe->pipe_buffer.object;
 334
 335         /*
 336          * [re]create the object if necessary and reserve space for it
 337          * in the kernel_map.  The object and memory are pageable.  On
 338          * success, free the old resources before assigning the new
 339          * ones.
 340          */
 341         if (object == NULL || object->size != npages) {
 342                 get_mplock();
 343                 object = vm_object_allocate(OBJT_DEFAULT, npages);
 344                 buffer = (caddr_t)vm_map_min(&kernel_map);
 345
 346                 error = vm_map_find(&kernel_map, object, 0,
 347                                     (vm_offset_t *)&buffer, size,
 348                                     1,
 349                                     VM_MAPTYPE_NORMAL,
 350                                     VM_PROT_ALL, VM_PROT_ALL,
 351                                     0);
 352
 353                 if (error != KERN_SUCCESS) {
 354                         vm_object_deallocate(object);
 355                         rel_mplock();
 356                         return (ENOMEM);
 357                 }
 358                 pipe_free_kmem(cpipe);
 359                 rel_mplock();
 360                 cpipe->pipe_buffer.object = object;
 361                 cpipe->pipe_buffer.buffer = buffer;
 362                 cpipe->pipe_buffer.size = size;
 363                 ++pipe_bkmem_alloc;
 364         } else {
 365                 ++pipe_bcache_alloc;
 366         }
 367         cpipe->pipe_buffer.rindex = 0;
 368         cpipe->pipe_buffer.windex = 0;
 369         return (0);
 370 }
 371
 372 /*
 373  * Initialize and allocate VM and memory for pipe, pulling the pipe from
 374  * our per-cpu cache if possible.  For now make sure it is sized for the
 375  * smaller PIPE_SIZE default.
 376  */
 377 static int
 378 pipe_create(struct pipe **cpipep)
 379 {
 380         globaldata_t gd = mycpu;
 381         struct pipe *cpipe;
 382         int error;
 383
 384         if ((cpipe = gd->gd_pipeq) != NULL) {
 385                 gd->gd_pipeq = cpipe->pipe_peer;
 386                 --gd->gd_pipeqcount;
 387                 cpipe->pipe_peer = NULL;
 388                 cpipe->pipe_wantwcnt = 0;
 389         } else {
 390                 cpipe = kmalloc(sizeof(struct pipe), M_PIPE, M_WAITOK|M_ZERO);
 391         }
 392         *cpipep = cpipe;
 393         if ((error = pipespace(cpipe, PIPE_SIZE)) != 0)
 394                 return (error);
 395         vfs_timestamp(&cpipe->pipe_ctime);
 396         cpipe->pipe_atime = cpipe->pipe_ctime;
 397         cpipe->pipe_mtime = cpipe->pipe_ctime;
 398         lwkt_token_init(&cpipe->pipe_rlock);
 399         lwkt_token_init(&cpipe->pipe_wlock);
 400         return (0);
 401 }
 402
 403 /*
 404  * MPALMOSTSAFE (acquires mplock)
 405  */
 406 static int
 407 pipe_read(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 408 {
 409         struct pipe *rpipe;
 410         int error;
 411         int orig_resid;
 412         int nread = 0;
 413         int nbio;
 414         u_int size;     /* total bytes available */
 415         u_int nsize;    /* total bytes to read */
 416         u_int rindex;   /* contiguous bytes available */
 417         int notify_writer;
 418         lwkt_tokref rlock;
 419         lwkt_tokref wlock;
 420         int mpsave;
 421
 422         /*
 423          * Degenerate case
 424          */
 425         orig_resid = uio->uio_resid;
 426         if (orig_resid == 0)
 427                 return(0);
 428
 429         /*
 430          * Setup locks, calculate nbio
 431          */
 432         pipe_get_mplock(&mpsave);
 433         rpipe = (struct pipe *)fp->f_data;
 434         lwkt_gettoken(&rlock, &rpipe->pipe_rlock);
 435
 436         if (fflags & O_FBLOCKING)
 437                 nbio = 0;
 438         else if (fflags & O_FNONBLOCKING)
 439                 nbio = 1;
 440         else if (fp->f_flag & O_NONBLOCK)
 441                 nbio = 1;
 442         else
 443                 nbio = 0;
 444
 445         /*
 446          * Reads are serialized.  Note howeverthat pipe_buffer.buffer and
 447          * pipe_buffer.size can change out from under us when the number
 448          * of bytes in the buffer are zero due to the write-side doing a
 449          * pipespace().
 450          */
 451         error = pipe_start_uio(rpipe, &rpipe->pipe_rip);
 452         if (error) {
 453                 pipe_rel_mplock(&mpsave);
 454                 lwkt_reltoken(&rlock);
 455                 return (error);
 456         }
 457         notify_writer = 0;
 458         while (uio->uio_resid) {
 459                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 460                 cpu_lfence();
 461                 if (size) {
 462                         rindex = rpipe->pipe_buffer.rindex &
 463                                  (rpipe->pipe_buffer.size - 1);
 464                         nsize = size;
 465                         if (nsize > rpipe->pipe_buffer.size - rindex)
 466                                 nsize = rpipe->pipe_buffer.size - rindex;
 467                         if (nsize > (u_int)uio->uio_resid)
 468                                 nsize = (u_int)uio->uio_resid;
 469
 470                         error = uiomove(&rpipe->pipe_buffer.buffer[rindex],
 471                                         nsize, uio);
 472                         if (error)
 473                                 break;
 474                         cpu_mfence();
 475                         rpipe->pipe_buffer.rindex += nsize;
 476                         nread += nsize;
 477
 478                         /*
 479                          * If the FIFO is still over half full just continue
 480                          * and do not try to notify the writer yet.
 481                          */
 482                         if (size - nsize >= (rpipe->pipe_buffer.size >> 1)) {
 483                                 notify_writer = 0;
 484                                 continue;
 485                         }
 486
 487                         /*
 488                          * When the FIFO is less then half full notify any
 489                          * waiting writer.  WANTW can be checked while
 490                          * holding just the rlock.
 491                          */
 492                         notify_writer = 1;
 493                         if ((rpipe->pipe_state & PIPE_WANTW) == 0)
 494                                 continue;
 495                 }
 496
 497                 /*
 498                  * If the "write-side" was blocked we wake it up.  This code
 499                  * is reached either when the buffer is completely emptied
 500                  * or if it becomes more then half-empty.
 501                  *
 502                  * Pipe_state can only be modified if both the rlock and
 503                  * wlock are held.
 504                  */
 505                 if (rpipe->pipe_state & PIPE_WANTW) {
 506                         lwkt_gettoken(&wlock, &rpipe->pipe_wlock);
 507                         if (rpipe->pipe_state & PIPE_WANTW) {
 508                                 notify_writer = 0;
 509                                 rpipe->pipe_state &= ~PIPE_WANTW;
 510                                 lwkt_reltoken(&wlock);
 511                                 wakeup(rpipe);
 512                         } else {
 513                                 lwkt_reltoken(&wlock);
 514                         }
 515                 }
 516
 517                 /*
 518                  * Pick up our copy loop again if the writer sent data to
 519                  * us while we were messing around.
 520                  *
 521                  * On a SMP box poll up to pipe_delay nanoseconds for new
 522                  * data.  Typically a value of 2000 to 4000 is sufficient
 523                  * to eradicate most IPIs/tsleeps/wakeups when a pipe
 524                  * is used for synchronous communications with small packets,
 525                  * and 8000 or so (8uS) will pipeline large buffer xfers
 526                  * between cpus over a pipe.
 527                  *
 528                  * For synchronous communications a hit means doing a
 529                  * full Awrite-Bread-Bwrite-Aread cycle in less then 2uS,
 530                  * where as miss requiring a tsleep/wakeup sequence
 531                  * will take 7uS or more.
 532                  */
 533                 if (rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex)
 534                         continue;
 535
 536 #if defined(SMP) && defined(_RDTSC_SUPPORTED_)
 537                 if (pipe_delay) {
 538                         int64_t tsc_target;
 539                         int good = 0;
 540
 541                         tsc_target = tsc_get_target(pipe_delay);
 542                         while (tsc_test_target(tsc_target) == 0) {
 543                                 if (rpipe->pipe_buffer.windex !=
 544                                     rpipe->pipe_buffer.rindex) {
 545                                         good = 1;
 546                                         break;
 547                                 }
 548                         }
 549                         if (good)
 550                                 continue;
 551                 }
 552 #endif
 553
 554                 /*
 555                  * Detect EOF condition, do not set error.
 556                  */
 557                 if (rpipe->pipe_state & PIPE_REOF)
 558                         break;
 559
 560                 /*
 561                  * Break if some data was read, or if this was a non-blocking
 562                  * read.
 563                  */
 564                 if (nread > 0)
 565                         break;
 566
 567                 if (nbio) {
 568                         error = EAGAIN;
 569                         break;
 570                 }
 571
 572                 /*
 573                  * Last chance, interlock with WANTR.
 574                  */
 575                 lwkt_gettoken(&wlock, &rpipe->pipe_wlock);
 576                 size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 577                 if (size) {
 578                         lwkt_reltoken(&wlock);
 579                         continue;
 580                 }
 581
 582                 /*
 583                  * If there is no more to read in the pipe, reset its
 584                  * pointers to the beginning.  This improves cache hit
 585                  * stats.
 586                  *
 587                  * We need both locks to modify both pointers, and there
 588                  * must also not be a write in progress or the uiomove()
 589                  * in the write might block and temporarily release
 590                  * its wlock, then reacquire and update windex.  We are
 591                  * only serialized against reads, not writes.
 592                  *
 593                  * XXX should we even bother resetting the indices?  It
 594                  *     might actually be more cache efficient not to.
 595                  */
 596                 if (rpipe->pipe_buffer.rindex == rpipe->pipe_buffer.windex &&
 597                     rpipe->pipe_wip == 0) {
 598                         rpipe->pipe_buffer.rindex = 0;
 599                         rpipe->pipe_buffer.windex = 0;
 600                 }
 601
 602                 /*
 603                  * Wait for more data.
 604                  *
 605                  * Pipe_state can only be set if both the rlock and wlock
 606                  * are held.
 607                  */
 608                 rpipe->pipe_state |= PIPE_WANTR;
 609                 tsleep_interlock(rpipe, PCATCH);
 610                 lwkt_reltoken(&wlock);
 611                 error = tsleep(rpipe, PCATCH | PINTERLOCKED, "piperd", 0);
 612                 ++pipe_rblocked_count;
 613                 if (error)
 614                         break;
 615         }
 616         pipe_end_uio(rpipe, &rpipe->pipe_rip);
 617
 618         /*
 619          * Uptime last access time
 620          */
 621         if (error == 0 && nread)
 622                 vfs_timestamp(&rpipe->pipe_atime);
 623
 624         /*
 625          * If we drained the FIFO more then half way then handle
 626          * write blocking hysteresis.
 627          *
 628          * Note that PIPE_WANTW cannot be set by the writer without
 629          * it holding both rlock and wlock, so we can test it
 630          * while holding just rlock.
 631          */
 632         if (notify_writer) {
 633                 if (rpipe->pipe_state & PIPE_WANTW) {
 634                         lwkt_gettoken(&wlock, &rpipe->pipe_wlock);
 635                         if (rpipe->pipe_state & PIPE_WANTW) {
 636                                 rpipe->pipe_state &= ~PIPE_WANTW;
 637                                 lwkt_reltoken(&wlock);
 638                                 wakeup(rpipe);
 639                         } else {
 640                                 lwkt_reltoken(&wlock);
 641                         }
 642                 }
 643         }
 644         size = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 645         lwkt_reltoken(&rlock);
 646
 647         /*
 648          * If enough space is available in buffer then wakeup sel writers?
 649          */
 650         if ((rpipe->pipe_buffer.size - size) >= PIPE_BUF)
 651                 pipeselwakeup(rpipe);
 652         pipe_rel_mplock(&mpsave);
 653         return (error);
 654 }
 655
 656 /*
 657  * MPALMOSTSAFE - acquires mplock
 658  */
 659 static int
 660 pipe_write(struct file *fp, struct uio *uio, struct ucred *cred, int fflags)
 661 {
 662         int error;
 663         int orig_resid;
 664         int nbio;
 665         struct pipe *wpipe, *rpipe;
 666         lwkt_tokref rlock;
 667         lwkt_tokref wlock;
 668         u_int windex;
 669         u_int space;
 670         u_int wcount;
 671         int mpsave;
 672
 673         pipe_get_mplock(&mpsave);
 674
 675         /*
 676          * Writes go to the peer.  The peer will always exist.
 677          */
 678         rpipe = (struct pipe *) fp->f_data;
 679         wpipe = rpipe->pipe_peer;
 680         lwkt_gettoken(&wlock, &wpipe->pipe_wlock);
 681         if (wpipe->pipe_state & PIPE_WEOF) {
 682                 pipe_rel_mplock(&mpsave);
 683                 lwkt_reltoken(&wlock);
 684                 return (EPIPE);
 685         }
 686
 687         /*
 688          * Degenerate case (EPIPE takes prec)
 689          */
 690         if (uio->uio_resid == 0) {
 691                 pipe_rel_mplock(&mpsave);
 692                 lwkt_reltoken(&wlock);
 693                 return(0);
 694         }
 695
 696         /*
 697          * Writes are serialized (start_uio must be called with wlock)
 698          */
 699         error = pipe_start_uio(wpipe, &wpipe->pipe_wip);
 700         if (error) {
 701                 pipe_rel_mplock(&mpsave);
 702                 lwkt_reltoken(&wlock);
 703                 return (error);
 704         }
 705
 706         if (fflags & O_FBLOCKING)
 707                 nbio = 0;
 708         else if (fflags & O_FNONBLOCKING)
 709                 nbio = 1;
 710         else if (fp->f_flag & O_NONBLOCK)
 711                 nbio = 1;
 712         else
 713                 nbio = 0;
 714
 715         /*
 716          * If it is advantageous to resize the pipe buffer, do
 717          * so.  We are write-serialized so we can block safely.
 718          */
 719         if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 720             (pipe_nbig < pipe_maxbig) &&
 721             wpipe->pipe_wantwcnt > 4 &&
 722             (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 723                 /*
 724                  * Recheck after lock.
 725                  */
 726                 lwkt_gettoken(&rlock, &wpipe->pipe_rlock);
 727                 if ((wpipe->pipe_buffer.size <= PIPE_SIZE) &&
 728                     (pipe_nbig < pipe_maxbig) &&
 729                     (wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex)) {
 730                         atomic_add_int(&pipe_nbig, 1);
 731                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
 732                                 ++pipe_bigcount;
 733                         else
 734                                 atomic_subtract_int(&pipe_nbig, 1);
 735                 }
 736                 lwkt_reltoken(&rlock);
 737         }
 738
 739         orig_resid = uio->uio_resid;
 740         wcount = 0;
 741
 742         while (uio->uio_resid) {
 743                 if (wpipe->pipe_state & PIPE_WEOF) {
 744                         error = EPIPE;
 745                         break;
 746                 }
 747
 748                 windex = wpipe->pipe_buffer.windex &
 749                          (wpipe->pipe_buffer.size - 1);
 750                 space = wpipe->pipe_buffer.size -
 751                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 752                 cpu_lfence();
 753
 754                 /* Writes of size <= PIPE_BUF must be atomic. */
 755                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 756                         space = 0;
 757
 758                 /*
 759                  * Write to fill, read size handles write hysteresis.  Also
 760                  * additional restrictions can cause select-based non-blocking
 761                  * writes to spin.
 762                  */
 763                 if (space > 0) {
 764                         u_int segsize;
 765
 766                         /*
 767                          * Transfer size is minimum of uio transfer
 768                          * and free space in pipe buffer.
 769                          *
 770                          * Limit each uiocopy to no more then PIPE_SIZE
 771                          * so we can keep the gravy train going on a
 772                          * SMP box.  This doubles the performance for
 773                          * write sizes > 16K.  Otherwise large writes
 774                          * wind up doing an inefficient synchronous
 775                          * ping-pong.
 776                          */
 777                         if (space > (u_int)uio->uio_resid)
 778                                 space = (u_int)uio->uio_resid;
 779                         if (space > PIPE_SIZE)
 780                                 space = PIPE_SIZE;
 781
 782                         /*
 783                          * First segment to transfer is minimum of
 784                          * transfer size and contiguous space in
 785                          * pipe buffer.  If first segment to transfer
 786                          * is less than the transfer size, we've got
 787                          * a wraparound in the buffer.
 788                          */
 789                         segsize = wpipe->pipe_buffer.size - windex;
 790                         if (segsize > space)
 791                                 segsize = space;
 792
 793 #ifdef SMP
 794                         /*
 795                          * If this is the first loop and the reader is
 796                          * blocked, do a preemptive wakeup of the reader.
 797                          *
 798                          * On SMP the IPI latency plus the wlock interlock
 799                          * on the reader side is the fastest way to get the
 800                          * reader going.  (The scheduler will hard loop on
 801                          * lock tokens).
 802                          *
 803                          * NOTE: We can't clear WANTR here without acquiring
 804                          * the rlock, which we don't want to do here!
 805                          */
 806                         if ((wpipe->pipe_state & PIPE_WANTR) && pipe_mpsafe > 1)
 807                                 wakeup(wpipe);
 808 #endif
 809
 810                         /*
 811                          * Transfer segment, which may include a wrap-around.
 812                          * Update windex to account for both all in one go
 813                          * so the reader can read() the data atomically.
 814                          */
 815                         error = uiomove(&wpipe->pipe_buffer.buffer[windex],
 816                                         segsize, uio);
 817                         if (error == 0 && segsize < space) {
 818                                 segsize = space - segsize;
 819                                 error = uiomove(&wpipe->pipe_buffer.buffer[0],
 820                                                 segsize, uio);
 821                         }
 822                         if (error)
 823                                 break;
 824                         cpu_mfence();
 825                         wpipe->pipe_buffer.windex += space;
 826                         wcount += space;
 827                         continue;
 828                 }
 829
 830                 /*
 831                  * We need both the rlock and the wlock to interlock against
 832                  * the EOF, WANTW, and size checks, and to modify pipe_state.
 833                  *
 834                  * These are token locks so we do not have to worry about
 835                  * deadlocks.
 836                  */
 837                 lwkt_gettoken(&rlock, &wpipe->pipe_rlock);
 838
 839                 /*
 840                  * If the "read-side" has been blocked, wake it up now
 841                  * and yield to let it drain synchronously rather
 842                  * then block.
 843                  */
 844                 if (wpipe->pipe_state & PIPE_WANTR) {
 845                         wpipe->pipe_state &= ~PIPE_WANTR;
 846                         wakeup(wpipe);
 847                 }
 848
 849                 /*
 850                  * don't block on non-blocking I/O
 851                  */
 852                 if (nbio) {
 853                         lwkt_reltoken(&rlock);
 854                         error = EAGAIN;
 855                         break;
 856                 }
 857
 858                 /*
 859                  * re-test whether we have to block in the writer after
 860                  * acquiring both locks, in case the reader opened up
 861                  * some space.
 862                  */
 863                 space = wpipe->pipe_buffer.size -
 864                         (wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex);
 865                 cpu_lfence();
 866                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 867                         space = 0;
 868
 869                 /*
 870                  * We have no more space and have something to offer,
 871                  * wake up select/poll.
 872                  */
 873                 if (space == 0) {
 874                         wpipe->pipe_state |= PIPE_WANTW;
 875                         ++wpipe->pipe_wantwcnt;
 876                         pipeselwakeup(wpipe);
 877                         if (wpipe->pipe_state & PIPE_WANTW)
 878                                 error = tsleep(wpipe, PCATCH, "pipewr", 0);
 879                         ++pipe_wblocked_count;
 880                 }
 881                 lwkt_reltoken(&rlock);
 882
 883                 /*
 884                  * Break out if we errored or the read side wants us to go
 885                  * away.
 886                  */
 887                 if (error)
 888                         break;
 889                 if (wpipe->pipe_state & PIPE_WEOF) {
 890                         error = EPIPE;
 891                         break;
 892                 }
 893         }
 894         pipe_end_uio(wpipe, &wpipe->pipe_wip);
 895
 896         /*
 897          * If we have put any characters in the buffer, we wake up
 898          * the reader.
 899          *
 900          * Both rlock and wlock are required to be able to modify pipe_state.
 901          */
 902         if (wpipe->pipe_buffer.windex != wpipe->pipe_buffer.rindex) {
 903                 if (wpipe->pipe_state & PIPE_WANTR) {
 904                         lwkt_gettoken(&rlock, &wpipe->pipe_rlock);
 905                         if (wpipe->pipe_state & PIPE_WANTR) {
 906                                 wpipe->pipe_state &= ~PIPE_WANTR;
 907                                 lwkt_reltoken(&rlock);
 908                                 wakeup(wpipe);
 909                         } else {
 910                                 lwkt_reltoken(&rlock);
 911                         }
 912                 }
 913         }
 914
 915         /*
 916          * Don't return EPIPE if I/O was successful
 917          */
 918         if ((wpipe->pipe_buffer.rindex == wpipe->pipe_buffer.windex) &&
 919             (uio->uio_resid == 0) &&
 920             (error == EPIPE)) {
 921                 error = 0;
 922         }
 923
 924         if (error == 0)
 925                 vfs_timestamp(&wpipe->pipe_mtime);
 926
 927         /*
 928          * We have something to offer,
 929          * wake up select/poll.
 930          */
 931         space = wpipe->pipe_buffer.windex - wpipe->pipe_buffer.rindex;
 932         lwkt_reltoken(&wlock);
 933         if (space)
 934                 pipeselwakeup(wpipe);
 935         pipe_rel_mplock(&mpsave);
 936         return (error);
 937 }
 938
 939 /*
 940  * MPALMOSTSAFE - acquires mplock
 941  *
 942  * we implement a very minimal set of ioctls for compatibility with sockets.
 943  */
 944 int
 945 pipe_ioctl(struct file *fp, u_long cmd, caddr_t data, struct ucred *cred)
 946 {
 947         struct pipe *mpipe;
 948         lwkt_tokref rlock;
 949         lwkt_tokref wlock;
 950         int error;
 951         int mpsave;
 952
 953         pipe_get_mplock(&mpsave);
 954         mpipe = (struct pipe *)fp->f_data;
 955
 956         lwkt_gettoken(&rlock, &mpipe->pipe_rlock);
 957         lwkt_gettoken(&wlock, &mpipe->pipe_wlock);
 958
 959         switch (cmd) {
 960         case FIOASYNC:
 961                 if (*(int *)data) {
 962                         mpipe->pipe_state |= PIPE_ASYNC;
 963                 } else {
 964                         mpipe->pipe_state &= ~PIPE_ASYNC;
 965                 }
 966                 error = 0;
 967                 break;
 968         case FIONREAD:
 969                 *(int *)data = mpipe->pipe_buffer.windex -
 970                                 mpipe->pipe_buffer.rindex;
 971                 error = 0;
 972                 break;
 973         case FIOSETOWN:
 974                 get_mplock();
 975                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 976                 rel_mplock();
 977                 break;
 978         case FIOGETOWN:
 979                 *(int *)data = fgetown(mpipe->pipe_sigio);
 980                 error = 0;
 981                 break;
 982         case TIOCSPGRP:
 983                 /* This is deprecated, FIOSETOWN should be used instead. */
 984                 get_mplock();
 985                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 986                 rel_mplock();
 987                 break;
 988
 989         case TIOCGPGRP:
 990                 /* This is deprecated, FIOGETOWN should be used instead. */
 991                 *(int *)data = -fgetown(mpipe->pipe_sigio);
 992                 error = 0;
 993                 break;
 994         default:
 995                 error = ENOTTY;
 996                 break;
 997         }
 998         lwkt_reltoken(&rlock);
 999         lwkt_reltoken(&wlock);
1000         pipe_rel_mplock(&mpsave);
1001
1002         return (error);
1003 }
1004
1005 /*
1006  * MPALMOSTSAFE - acquires mplock
1007  */
1008 int
1009 pipe_poll(struct file *fp, int events, struct ucred *cred)
1010 {
1011         struct pipe *rpipe;
1012         struct pipe *wpipe;
1013         int revents = 0;
1014         u_int space;
1015         int mpsave;
1016
1017         pipe_get_mplock(&mpsave);
1018         rpipe = (struct pipe *)fp->f_data;
1019         wpipe = rpipe->pipe_peer;
1020         if (events & (POLLIN | POLLRDNORM)) {
1021                 if ((rpipe->pipe_buffer.windex != rpipe->pipe_buffer.rindex) ||
1022                     (rpipe->pipe_state & PIPE_REOF)) {
1023                         revents |= events & (POLLIN | POLLRDNORM);
1024                 }
1025         }
1026
1027         if (events & (POLLOUT | POLLWRNORM)) {
1028                 if (wpipe == NULL || (wpipe->pipe_state & PIPE_WEOF)) {
1029                         revents |= events & (POLLOUT | POLLWRNORM);
1030                 } else {
1031                         space = wpipe->pipe_buffer.windex -
1032                                 wpipe->pipe_buffer.rindex;
1033                         space = wpipe->pipe_buffer.size - space;
1034                         if (space >= PIPE_BUF)
1035                                 revents |= events & (POLLOUT | POLLWRNORM);
1036                 }
1037         }
1038
1039         if ((rpipe->pipe_state & PIPE_REOF) ||
1040             (wpipe == NULL) ||
1041             (wpipe->pipe_state & PIPE_WEOF))
1042                 revents |= POLLHUP;
1043
1044         if (revents == 0) {
1045                 if (events & (POLLIN | POLLRDNORM)) {
1046                         selrecord(curthread, &rpipe->pipe_sel);
1047                         rpipe->pipe_state |= PIPE_SEL;
1048                 }
1049
1050                 if (events & (POLLOUT | POLLWRNORM)) {
1051                         selrecord(curthread, &wpipe->pipe_sel);
1052                         wpipe->pipe_state |= PIPE_SEL;
1053                 }
1054         }
1055         pipe_rel_mplock(&mpsave);
1056         return (revents);
1057 }
1058
1059 /*
1060  * MPSAFE
1061  */
1062 static int
1063 pipe_stat(struct file *fp, struct stat *ub, struct ucred *cred)
1064 {
1065         struct pipe *pipe;
1066         int mpsave;
1067
1068         pipe_get_mplock(&mpsave);
1069         pipe = (struct pipe *)fp->f_data;
1070
1071         bzero((caddr_t)ub, sizeof(*ub));
1072         ub->st_mode = S_IFIFO;
1073         ub->st_blksize = pipe->pipe_buffer.size;
1074         ub->st_size = pipe->pipe_buffer.windex - pipe->pipe_buffer.rindex;
1075         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
1076         ub->st_atimespec = pipe->pipe_atime;
1077         ub->st_mtimespec = pipe->pipe_mtime;
1078         ub->st_ctimespec = pipe->pipe_ctime;
1079         /*
1080          * Left as 0: st_dev, st_ino, st_nlink, st_uid, st_gid, st_rdev,
1081          * st_flags, st_gen.
1082          * XXX (st_dev, st_ino) should be unique.
1083          */
1084         pipe_rel_mplock(&mpsave);
1085         return (0);
1086 }
1087
1088 /*
1089  * MPALMOSTSAFE - acquires mplock
1090  */
1091 static int
1092 pipe_close(struct file *fp)
1093 {
1094         struct pipe *cpipe;
1095
1096         get_mplock();
1097         cpipe = (struct pipe *)fp->f_data;
1098         fp->f_ops = &badfileops;
1099         fp->f_data = NULL;
1100         funsetown(cpipe->pipe_sigio);
1101         pipeclose(cpipe);
1102         rel_mplock();
1103         return (0);
1104 }
1105
1106 /*
1107  * Shutdown one or both directions of a full-duplex pipe.
1108  *
1109  * MPALMOSTSAFE - acquires mplock
1110  */
1111 static int
1112 pipe_shutdown(struct file *fp, int how)
1113 {
1114         struct pipe *rpipe;
1115         struct pipe *wpipe;
1116         int error = EPIPE;
1117         lwkt_tokref rpipe_rlock;
1118         lwkt_tokref rpipe_wlock;
1119         lwkt_tokref wpipe_rlock;
1120         lwkt_tokref wpipe_wlock;
1121         int mpsave;
1122
1123         pipe_get_mplock(&mpsave);
1124         rpipe = (struct pipe *)fp->f_data;
1125         wpipe = rpipe->pipe_peer;
1126
1127         /*
1128          * We modify pipe_state on both pipes, which means we need
1129          * all four tokens!
1130          */
1131         lwkt_gettoken(&rpipe_rlock, &rpipe->pipe_rlock);
1132         lwkt_gettoken(&rpipe_wlock, &rpipe->pipe_wlock);
1133         lwkt_gettoken(&wpipe_rlock, &wpipe->pipe_rlock);
1134         lwkt_gettoken(&wpipe_wlock, &wpipe->pipe_wlock);
1135
1136         switch(how) {
1137         case SHUT_RDWR:
1138         case SHUT_RD:
1139                 rpipe->pipe_state |= PIPE_REOF;         /* my reads */
1140                 rpipe->pipe_state |= PIPE_WEOF;         /* peer writes */
1141                 if (rpipe->pipe_state & PIPE_WANTR) {
1142                         rpipe->pipe_state &= ~PIPE_WANTR;
1143                         wakeup(rpipe);
1144                 }
1145                 if (rpipe->pipe_state & PIPE_WANTW) {
1146                         rpipe->pipe_state &= ~PIPE_WANTW;
1147                         wakeup(rpipe);
1148                 }
1149                 error = 0;
1150                 if (how == SHUT_RD)
1151                         break;
1152                 /* fall through */
1153         case SHUT_WR:
1154                 wpipe->pipe_state |= PIPE_REOF;         /* peer reads */
1155                 wpipe->pipe_state |= PIPE_WEOF;         /* my writes */
1156                 if (wpipe->pipe_state & PIPE_WANTR) {
1157                         wpipe->pipe_state &= ~PIPE_WANTR;
1158                         wakeup(wpipe);
1159                 }
1160                 if (wpipe->pipe_state & PIPE_WANTW) {
1161                         wpipe->pipe_state &= ~PIPE_WANTW;
1162                         wakeup(wpipe);
1163                 }
1164                 error = 0;
1165                 break;
1166         }
1167         pipeselwakeup(rpipe);
1168         pipeselwakeup(wpipe);
1169
1170         lwkt_reltoken(&rpipe_rlock);
1171         lwkt_reltoken(&rpipe_wlock);
1172         lwkt_reltoken(&wpipe_rlock);
1173         lwkt_reltoken(&wpipe_wlock);
1174
1175         pipe_rel_mplock(&mpsave);
1176         return (error);
1177 }
1178
1179 static void
1180 pipe_free_kmem(struct pipe *cpipe)
1181 {
1182         if (cpipe->pipe_buffer.buffer != NULL) {
1183                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
1184                         atomic_subtract_int(&pipe_nbig, 1);
1185                 kmem_free(&kernel_map,
1186                         (vm_offset_t)cpipe->pipe_buffer.buffer,
1187                         cpipe->pipe_buffer.size);
1188                 cpipe->pipe_buffer.buffer = NULL;
1189                 cpipe->pipe_buffer.object = NULL;
1190         }
1191 }
1192
1193 /*
1194  * Close the pipe.  The slock must be held to interlock against simultanious
1195  * closes.  The rlock and wlock must be held to adjust the pipe_state.
1196  */
1197 static void
1198 pipeclose(struct pipe *cpipe)
1199 {
1200         globaldata_t gd;
1201         struct pipe *ppipe;
1202         lwkt_tokref cpipe_rlock;
1203         lwkt_tokref cpipe_wlock;
1204         lwkt_tokref ppipe_rlock;
1205         lwkt_tokref ppipe_wlock;
1206
1207         if (cpipe == NULL)
1208                 return;
1209
1210         /*
1211          * The slock may not have been allocated yet (close during
1212          * initialization)
1213          *
1214          * We need both the read and write tokens to modify pipe_state.
1215          */
1216         if (cpipe->pipe_slock)
1217                 lockmgr(cpipe->pipe_slock, LK_EXCLUSIVE);
1218         lwkt_gettoken(&cpipe_rlock, &cpipe->pipe_rlock);
1219         lwkt_gettoken(&cpipe_wlock, &cpipe->pipe_wlock);
1220
1221         /*
1222          * Set our state, wakeup anyone waiting in select, and
1223          * wakeup anyone blocked on our pipe.
1224          */
1225         cpipe->pipe_state |= PIPE_CLOSED | PIPE_REOF | PIPE_WEOF;
1226         pipeselwakeup(cpipe);
1227         if (cpipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1228                 cpipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1229                 wakeup(cpipe);
1230         }
1231
1232         /*
1233          * Disconnect from peer.
1234          */
1235         if ((ppipe = cpipe->pipe_peer) != NULL) {
1236                 lwkt_gettoken(&ppipe_rlock, &ppipe->pipe_rlock);
1237                 lwkt_gettoken(&ppipe_wlock, &ppipe->pipe_wlock);
1238                 ppipe->pipe_state |= PIPE_REOF | PIPE_WEOF;
1239                 pipeselwakeup(ppipe);
1240                 if (ppipe->pipe_state & (PIPE_WANTR | PIPE_WANTW)) {
1241                         ppipe->pipe_state &= ~(PIPE_WANTR | PIPE_WANTW);
1242                         wakeup(ppipe);
1243                 }
1244                 if (SLIST_FIRST(&ppipe->pipe_sel.si_note)) {
1245                         get_mplock();
1246                         KNOTE(&ppipe->pipe_sel.si_note, 0);
1247                         rel_mplock();
1248                 }
1249                 lwkt_reltoken(&ppipe_rlock);
1250                 lwkt_reltoken(&ppipe_wlock);
1251         }
1252
1253         /*
1254          * If the peer is also closed we can free resources for both
1255          * sides, otherwise we leave our side intact to deal with any
1256          * races (since we only have the slock).
1257          */
1258         if (ppipe && (ppipe->pipe_state & PIPE_CLOSED)) {
1259                 cpipe->pipe_peer = NULL;
1260                 ppipe->pipe_peer = NULL;
1261                 ppipe->pipe_slock = NULL;       /* we will free the slock */
1262                 pipeclose(ppipe);
1263                 ppipe = NULL;
1264         }
1265
1266         lwkt_reltoken(&cpipe_rlock);
1267         lwkt_reltoken(&cpipe_wlock);
1268         if (cpipe->pipe_slock)
1269                 lockmgr(cpipe->pipe_slock, LK_RELEASE);
1270
1271         /*
1272          * If we disassociated from our peer we can free resources
1273          */
1274         if (ppipe == NULL) {
1275                 gd = mycpu;
1276                 if (cpipe->pipe_slock) {
1277                         kfree(cpipe->pipe_slock, M_PIPE);
1278                         cpipe->pipe_slock = NULL;
1279                 }
1280                 if (gd->gd_pipeqcount >= pipe_maxcache ||
1281                     cpipe->pipe_buffer.size != PIPE_SIZE
1282                 ) {
1283                         pipe_free_kmem(cpipe);
1284                         kfree(cpipe, M_PIPE);
1285                 } else {
1286                         cpipe->pipe_state = 0;
1287                         cpipe->pipe_peer = gd->gd_pipeq;
1288                         gd->gd_pipeq = cpipe;
1289                         ++gd->gd_pipeqcount;
1290                 }
1291         }
1292 }
1293
1294 /*
1295  * MPALMOSTSAFE - acquires mplock
1296  */
1297 static int
1298 pipe_kqfilter(struct file *fp, struct knote *kn)
1299 {
1300         struct pipe *cpipe;
1301
1302         get_mplock();
1303         cpipe = (struct pipe *)kn->kn_fp->f_data;
1304
1305         switch (kn->kn_filter) {
1306         case EVFILT_READ:
1307                 kn->kn_fop = &pipe_rfiltops;
1308                 break;
1309         case EVFILT_WRITE:
1310                 kn->kn_fop = &pipe_wfiltops;
1311                 cpipe = cpipe->pipe_peer;
1312                 if (cpipe == NULL) {
1313                         /* other end of pipe has been closed */
1314                         rel_mplock();
1315                         return (EPIPE);
1316                 }
1317                 break;
1318         default:
1319                 return (1);
1320         }
1321         kn->kn_hook = (caddr_t)cpipe;
1322
1323         SLIST_INSERT_HEAD(&cpipe->pipe_sel.si_note, kn, kn_selnext);
1324         rel_mplock();
1325         return (0);
1326 }
1327
1328 static void
1329 filt_pipedetach(struct knote *kn)
1330 {
1331         struct pipe *cpipe = (struct pipe *)kn->kn_hook;
1332
1333         SLIST_REMOVE(&cpipe->pipe_sel.si_note, kn, knote, kn_selnext);
1334 }
1335
1336 /*ARGSUSED*/
1337 static int
1338 filt_piperead(struct knote *kn, long hint)
1339 {
1340         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1341
1342         kn->kn_data = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
1343
1344         /* XXX RACE */
1345         if (rpipe->pipe_state & PIPE_REOF) {
1346                 kn->kn_flags |= EV_EOF;
1347                 return (1);
1348         }
1349         return (kn->kn_data > 0);
1350 }
1351
1352 /*ARGSUSED*/
1353 static int
1354 filt_pipewrite(struct knote *kn, long hint)
1355 {
1356         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
1357         struct pipe *wpipe = rpipe->pipe_peer;
1358         u_int32_t space;
1359
1360         /* XXX RACE */
1361         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_WEOF)) {
1362                 kn->kn_data = 0;
1363                 kn->kn_flags |= EV_EOF;
1364                 return (1);
1365         }
1366         space = wpipe->pipe_buffer.windex -
1367                 wpipe->pipe_buffer.rindex;
1368         space = wpipe->pipe_buffer.size - space;
1369         kn->kn_data = space;
1370         return (kn->kn_data >= PIPE_BUF);
1371 }