src/comm/ModDevPoll.cc

   1 /*
   2  * $Id$
   3  *
   4  * DEBUG: section 05    Socket Functions
   5  *
   6  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   7  * ----------------------------------------------------------
   8  *
   9  *  Squid is the result of efforts by numerous individuals from
  10  *  the Internet community; see the CONTRIBUTORS file for full
  11  *  details.   Many organizations have provided support for Squid's
  12  *  development; see the SPONSORS file for full details.  Squid is
  13  *  Copyrighted (C) 2001 by the Regents of the University of
  14  *  California; see the COPYRIGHT file for full details.  Squid
  15  *  incorporates software developed and/or copyrighted by other
  16  *  sources; see the CREDITS file for full details.
  17  *
  18  *  This program is free software; you can redistribute it and/or modify
  19  *  it under the terms of the GNU General Public License as published by
  20  *  the Free Software Foundation; either version 2 of the License, or
  21  *  (at your option) any later version.
  22  *
  23  *  This program is distributed in the hope that it will be useful,
  24  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  25  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  26  *  GNU General Public License for more details.
  27  *
  28  *  You should have received a copy of the GNU General Public License
  29  *  along with this program; if not, write to the Free Software
  30  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  31  *
  32  */
  33
  34 /*
  35  * This is a very simple driver for Solaris /dev/poll.
  36  *
  37  * The updates are batched, one trip through the comm loop.
  38  * (like libevent.) We keep a pointer into the structs so we
  39  * can zero out an entry in the poll list if its active.
  40  *
  41  * Ported by Peter Payne from Squid 2.7.STABLE9 comm_devpoll.c
  42  * on August 11, 2010 at 3pm (GMT+0100 Europe/London).
  43  *
  44  * Last modified 2010-10-08
  45  */
  46
  47 /*
  48  * There are several poll types in Squid, ALL of which are compiled and linked
  49  * in. Thus conditional compile-time flags are used to prevent the different
  50  * modules from creating several versions of the same function simultaneously.
  51  */
  52
  53 #include "squid.h"
  54
  55 #if USE_DEVPOLL
  56
  57 #include "squid-old.h"
  58 #include "comm/Loops.h"
  59 #include "fde.h"
  60 #include "mgr/Registration.h"
  61 #include "SquidTime.h"
  62 #include "StatCounters.h"
  63 #include "StatHist.h"
  64 #include "Store.h"
  65
  66 #if HAVE_SYS_DEVPOLL_H
  67 /* Solaris /dev/poll support, see "man -s 7D poll" */
  68 #include <sys/devpoll.h>
  69 #endif
  70
  71 #define DEBUG_DEVPOLL 0
  72
  73 /* OPEN_MAX is defined in <limits.h>, presumably included by sys/devpoll.h */
  74 #define DEVPOLL_UPDATESIZE      OPEN_MAX
  75 #define DEVPOLL_QUERYSIZE       OPEN_MAX
  76
  77 /* TYPEDEFS */
  78 typedef short pollfd_events_t; /* type of pollfd.events from sys/poll.h */
  79
  80 /* STRUCTURES */
  81 /** \brief Current state */
  82 struct _devpoll_state {
  83     pollfd_events_t state; /**< current known state of file handle */
  84 };
  85
  86 /** \brief Update list
  87  *
  88  * This structure contains an array of settings to send to the /dev/poll
  89  * interface. Rather than send changes to /dev/poll one at a time they
  90  * are pushed onto this array (updating cur to indicate how many of the
  91  * pfds structure elements have been set) until it is full before it
  92  * is written out the API.
  93  */
  94 static struct {
  95     struct pollfd *pfds; /**< ptr to array of struct pollfd config elements */
  96     int cur; /**< index of last written element of array, or -1 if none */
  97     int size; /**< maximum number of elements in array */
  98 } devpoll_update;
  99
 100
 101 /* STATIC VARIABLES */
 102 static int devpoll_fd; /**< handle to /dev/poll device */
 103 static int max_poll_time = 1000; /**< maximum milliseconds to spend in poll */
 104
 105 static struct _devpoll_state *devpoll_state; /**< array of socket states */
 106 static struct dvpoll do_poll; /**< data struct for storing poll results */
 107 static int dpoll_nfds; /**< maximum number of poll results */
 108
 109 /* PROTOTYPES */
 110 static void commDevPollRegisterWithCacheManager(void);
 111
 112
 113 /* PRIVATE FUNCTIONS */
 114 /** \brief Write batched file descriptor event changes to poll device
 115  *
 116  * Writes out the static array of file descriptor event changes to the
 117  * poll device. This is done only when necessary (i.e. just before
 118  * the poll device is queried during the select call, and whenever
 119  * the number of changes to store in the array exceeds the size of the
 120  * array).
 121  */
 122 static void
 123 comm_flush_updates(void)
 124 {
 125     int i;
 126     if (devpoll_update.cur == -1)
 127         return; /* array of changes to make is empty */
 128
 129     debugs(
 130         5,
 131         DEBUG_DEVPOLL ? 0 : 8,
 132         HERE << (devpoll_update.cur + 1) << " fds queued"
 133     );
 134
 135     i = write(
 136             devpoll_fd, /* open handle to /dev/poll */
 137             devpoll_update.pfds, /* pointer to array of struct pollfd */
 138             (devpoll_update.cur + 1) * sizeof(struct pollfd) /* bytes to process */
 139         );
 140     assert(i > 0);
 141     assert(static_cast<size_t>(i) == (sizeof(struct pollfd) * (devpoll_update.cur + 1)));
 142     devpoll_update.cur = -1; /* reset size of array, no elements remain */
 143 }
 144
 145 /** \brief Register change in desired polling state for file descriptor
 146  *
 147  * Prevents unnecessary calls to the /dev/poll API by queueing changes
 148  * in the devpoll_update array. If the array fills up the comm_flush_updates
 149  * function is called.
 150  *
 151  * @param fd file descriptor to register change with
 152  * @param events events to register (usually POLLIN, POLLOUT, or POLLREMOVE)
 153  */
 154 static void
 155 comm_update_fd(int fd, int events)
 156 {
 157     debugs(
 158         5,
 159         DEBUG_DEVPOLL ? 0 : 8,
 160         HERE << "FD " << fd << ", events=" << events
 161     );
 162
 163     /* Is the array already full and in need of flushing? */
 164     if (devpoll_update.cur != -1 && (devpoll_update.cur == devpoll_update.size))
 165         comm_flush_updates();
 166
 167     /* Push new event onto array */
 168     ++ devpoll_update.cur;
 169     devpoll_update.pfds[devpoll_update.cur].fd = fd;
 170     devpoll_update.pfds[devpoll_update.cur].events = events;
 171     devpoll_update.pfds[devpoll_update.cur].revents = 0;
 172 }
 173
 174
 175 static void commIncomingStats(StoreEntry *sentry)
 176 {
 177     storeAppendPrintf(sentry, "Total number of devpoll loops: %ld\n", statCounter.select_loops);
 178     storeAppendPrintf(sentry, "Histogram of returned filedescriptors\n");
 179     statCounter.select_fds_hist.dump(sentry, statHistIntDumper);
 180 }
 181
 182
 183 static void
 184 commDevPollRegisterWithCacheManager(void)
 185 {
 186     Mgr::RegisterAction(
 187         "comm_devpoll_incoming",
 188         "comm_incoming() stats",
 189         commIncomingStats,
 190         0,
 191         1
 192     );
 193 }
 194
 195
 196 /* PUBLIC FUNCTIONS */
 197
 198 /** \brief Initialise /dev/poll support
 199  *
 200  * Allocates memory, opens /dev/poll device handle.
 201  */
 202 void
 203 Comm::SelectLoopInit(void)
 204 {
 205     /* allocate memory first before attempting to open poll device */
 206     /* This tracks the FD devpoll offset+state */
 207     devpoll_state = (struct _devpoll_state *)xcalloc(
 208                         SQUID_MAXFD, sizeof(struct _devpoll_state)
 209                     );
 210
 211     /* And this is the stuff we use to read events */
 212     do_poll.dp_fds = (struct pollfd *)xcalloc(
 213                          DEVPOLL_QUERYSIZE, sizeof(struct pollfd)
 214                      );
 215     dpoll_nfds = DEVPOLL_QUERYSIZE;
 216
 217     devpoll_update.pfds = (struct pollfd *)xcalloc(
 218                               DEVPOLL_UPDATESIZE, sizeof(struct pollfd)
 219                           );
 220     devpoll_update.cur = -1;
 221     devpoll_update.size = DEVPOLL_UPDATESIZE;
 222
 223     /* attempt to open /dev/poll device */
 224     devpoll_fd = open("/dev/poll", O_RDWR);
 225     if (devpoll_fd < 0)
 226         fatalf("comm_select_init: can't open /dev/poll: %s\n", xstrerror());
 227
 228     fd_open(devpoll_fd, FD_UNKNOWN, "devpoll ctl");
 229
 230     commDevPollRegisterWithCacheManager();
 231 }
 232
 233 /** \brief Set polling state of file descriptor and callback functions
 234  *
 235  * Sets requested polling state for given file handle along with
 236  * desired callback function in the event the request event triggers.
 237  *
 238  * Note that setting a polling state with a NULL callback function will
 239  * clear the polling for that event on that file descriptor.
 240  *
 241  * @param fd file descriptor to change
 242  * @param type may be COMM_SELECT_READ (input) or COMM_SELECT_WRITE (output)
 243  * @param handler callback function, or NULL to stop type of polling
 244  * @param client_data pointer to be provided to call back function
 245  * @param timeout if non-zero then timeout relative to now
 246  */
 247 void
 248 Comm::SetSelect(int fd, unsigned int type, PF * handler, void *client_data, time_t timeout)
 249 {
 250     assert(fd >= 0);
 251     debugs(5, 5, HERE << "FD " << fd << ", type=" << type <<
 252            ", handler=" << handler << ", client_data=" << client_data <<
 253            ", timeout=" << timeout);
 254
 255     /* POLLIN/POLLOUT are defined in <sys/poll.h> */
 256     fde *F = &fd_table[fd];
 257     if (!F->flags.open) {
 258         /* remove from poll set */
 259         comm_update_fd( fd, POLLREMOVE );
 260         devpoll_state[fd].state = 0;
 261         return;
 262     }
 263
 264     pollfd_events_t state_old = devpoll_state[fd].state;
 265     pollfd_events_t state_new = 0; /* new state (derive from old state) */
 266
 267     if ( type & COMM_SELECT_READ ) {
 268         if ( handler != NULL ) {
 269             /* we want to POLLIN */
 270             state_new |= POLLIN;
 271         } else {
 272             ; /* we want to clear POLLIN because handler is NULL */
 273         }
 274
 275         F->read_handler = handler;
 276         F->read_data = client_data;
 277     } else if ( state_old & POLLIN ) {
 278         /* we're not changing reading state so take from existing */
 279         state_new |= POLLIN;
 280     }
 281
 282     if ( type & COMM_SELECT_WRITE ) {
 283         if ( handler != NULL ) {
 284             /* we want to POLLOUT */
 285             state_new |= POLLOUT;
 286         } else {
 287             ; /* we want to clear POLLOUT because handler is NULL */
 288         }
 289
 290         F->write_handler = handler;
 291         F->write_data = client_data;
 292     } else if ( state_old & POLLOUT ) {
 293         /* we're not changing writing state so take from existing */
 294         state_new |= POLLOUT;
 295     }
 296
 297     if ( pollfd_events_t bits_changed = (state_old ^ state_new) ) {
 298         /* something has changed, update /dev/poll of what to listen for */
 299
 300         /* did any bits clear? (in which case a poll remove is necessary) */
 301         if ( bits_changed & state_old ) {
 302             comm_update_fd( fd, POLLREMOVE );
 303             /* existing state cleared, so update with all required events */
 304             if ( state_new )
 305                 comm_update_fd( fd, state_new );
 306         } else {
 307             /* only update with new required event */
 308             if ( pollfd_events_t newly_set_only = (bits_changed & state_new) )
 309                 comm_update_fd( fd, newly_set_only );
 310         }
 311
 312         devpoll_state[fd].state = state_new;
 313     }
 314
 315     if (timeout)
 316         F->timeout = squid_curtime + timeout;
 317 }
 318
 319
 320 /** \brief Clear polling of file handle (both read and write)
 321  *
 322  * @param fd file descriptor to clear polling on
 323  */
 324 void
 325 Comm::ResetSelect(int fd)
 326 {
 327     SetSelect(fd, COMM_SELECT_WRITE, NULL, NULL, 0);
 328     SetSelect(fd, COMM_SELECT_READ, NULL, NULL, 0);
 329 }
 330
 331
 332 /** \brief Do poll and trigger callback functions as appropriate
 333  *
 334  * Check all connections for new connections and input data that is to be
 335  * processed. Also check for connections with data queued and whether we can
 336  * write it out.
 337  *
 338  * Called to do the new-style IO, courtesy of of squid (like most of this
 339  * new IO code). This routine handles the stuff we've hidden in
 340  * comm_setselect and fd_table[] and calls callbacks for IO ready
 341  * events.
 342  *
 343  * @param msec milliseconds to poll for (limited by max_poll_time)
 344  */
 345 comm_err_t
 346 Comm::DoSelect(int msec)
 347 {
 348     int num, i;
 349     fde *F;
 350     PF *hdl;
 351
 352     PROF_start(comm_check_incoming);
 353
 354     if (msec > max_poll_time)
 355         msec = max_poll_time;
 356
 357     for (;;) {
 358         do_poll.dp_timeout = msec;
 359         do_poll.dp_nfds = dpoll_nfds;
 360
 361         comm_flush_updates(); /* ensure latest changes are sent to /dev/poll */
 362
 363         num = ioctl(devpoll_fd, DP_POLL, &do_poll);
 364         ++ statCounter.select_loops;
 365
 366         if (num >= 0)
 367             break; /* no error, skip out of loop */
 368
 369         if (ignoreErrno(errno))
 370             break; /* error is one we may ignore, skip out of loop */
 371
 372         /* error during poll */
 373         getCurrentTime();
 374         PROF_stop(comm_check_incoming);
 375         return COMM_ERROR;
 376     }
 377
 378     PROF_stop(comm_check_incoming);
 379     getCurrentTime();
 380
 381     statCounter.select_fds_hist.count(num);
 382
 383     if (num == 0)
 384         return COMM_TIMEOUT; /* no error */
 385
 386     PROF_start(comm_handle_ready_fd);
 387
 388     for (i = 0; i < num; ++i) {
 389         int fd = (int)do_poll.dp_fds[i].fd;
 390         F = &fd_table[fd];
 391         debugs(
 392             5,
 393             DEBUG_DEVPOLL ? 0 : 8,
 394             HERE << "got FD " << fd
 395             << ",events=" << std::hex << do_poll.dp_fds[i].revents
 396             << ",monitoring=" << devpoll_state[fd].state
 397             << ",F->read_handler=" << F->read_handler
 398             << ",F->write_handler=" << F->write_handler
 399         );
 400
 401         /* handle errors */
 402         if (do_poll.dp_fds[i].revents & (POLLERR | POLLHUP | POLLNVAL)) {
 403             debugs(
 404                 5,
 405                 DEBUG_DEVPOLL ? 0 : 8,
 406                 HERE << "devpoll event error: fd " << fd
 407             );
 408             continue;
 409         }
 410
 411         /* check if file descriptor has data to read */
 412         if (do_poll.dp_fds[i].revents & POLLIN || F->flags.read_pending) {
 413             if ( (hdl = F->read_handler) != NULL ) {
 414                 debugs(
 415                     5,
 416                     DEBUG_DEVPOLL ? 0 : 8,
 417                     HERE << "Calling read handler on FD " << fd
 418                 );
 419                 PROF_start(comm_read_handler);
 420                 F->flags.read_pending = 0;
 421                 F->read_handler = NULL;
 422                 hdl(fd, F->read_data);
 423                 PROF_stop(comm_read_handler);
 424                 ++ statCounter.select_fds;
 425             } else {
 426                 debugs(
 427                     5,
 428                     DEBUG_DEVPOLL ? 0 : 8,
 429                     HERE << "no read handler for FD " << fd
 430                 );
 431                 // remove interest since no handler exist for this event.
 432                 SetSelect(fd, COMM_SELECT_READ, NULL, NULL, 0);
 433             }
 434         }
 435
 436         /* check if file descriptor is ready to write */
 437         if (do_poll.dp_fds[i].revents & POLLOUT) {
 438             if ((hdl = F->write_handler) != NULL) {
 439                 debugs(
 440                     5,
 441                     DEBUG_DEVPOLL ? 0 : 8,
 442                     HERE << "Calling write handler on FD " << fd
 443                 );
 444                 PROF_start(comm_write_handler);
 445                 F->write_handler = NULL;
 446                 hdl(fd, F->write_data);
 447                 PROF_stop(comm_write_handler);
 448                 ++ statCounter.select_fds;
 449             } else {
 450                 debugs(
 451                     5,
 452                     DEBUG_DEVPOLL ? 0 : 8,
 453                     HERE << "no write handler for FD " << fd
 454                 );
 455                 // remove interest since no handler exist for this event.
 456                 SetSelect(fd, COMM_SELECT_WRITE, NULL, NULL, 0);
 457             }
 458         }
 459     }
 460
 461     PROF_stop(comm_handle_ready_fd);
 462     return COMM_OK;
 463 }
 464
 465 void
 466 Comm::QuickPollRequired(void)
 467 {
 468     max_poll_time = 10;
 469 }
 470
 471 #endif /* USE_DEVPOLL */