src/common/compat/poll.h

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #ifndef _LTT_POLL_H
  19 #define _LTT_POLL_H
  20
  21 #include <assert.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24
  25 #include <common/common.h>
  26
  27 /*
  28  * Maximum number of fd we can monitor.
  29  *
  30  * For epoll(7), /proc/sys/fs/epoll/max_user_watches (since Linux 2.6.28) will
  31  * be used for the maximum size of the poll set. If this interface is not
  32  * available, according to the manpage, the max_user_watches value is 1/25 (4%)
  33  * of the available low memory divided by the registration cost in bytes which
  34  * is 90 bytes on a 32-bit kernel and 160 bytes on a 64-bit kernel.
  35  *
  36  * For poll(2), the max fds must not exceed RLIMIT_NOFILE given by
  37  * getrlimit(2).
  38  */
  39 extern unsigned int poll_max_size;
  40
  41 /*
  42  * Used by lttng_poll_clean to free the events structure in a lttng_poll_event.
  43  */
  44 static inline void __lttng_poll_free(void *events)
  45 {
  46         free(events);
  47 }
  48
  49 /*
  50  * epoll(7) implementation.
  51  */
  52 #ifdef HAVE_EPOLL
  53 #include <sys/epoll.h>
  54 #include <stdio.h>
  55 #include <features.h>
  56 #include <common/compat/fcntl.h>
  57
  58 /* See man epoll(7) for this define path */
  59 #define COMPAT_EPOLL_PROC_PATH "/proc/sys/fs/epoll/max_user_watches"
  60
  61 enum {
  62         /* Polling variables compatibility for epoll */
  63         LPOLLIN = EPOLLIN,
  64         LPOLLPRI = EPOLLPRI,
  65         LPOLLOUT = EPOLLOUT,
  66         LPOLLRDNORM = EPOLLRDNORM,
  67         LPOLLRDBAND = EPOLLRDBAND,
  68         LPOLLWRNORM = EPOLLWRNORM,
  69         LPOLLWRBAND = EPOLLWRBAND,
  70         LPOLLMSG = EPOLLMSG,
  71         LPOLLERR = EPOLLERR,
  72         LPOLLHUP = EPOLLHUP,
  73         LPOLLNVAL = EPOLLHUP,
  74         LPOLLRDHUP = EPOLLRDHUP,
  75         /* Close on exec feature of epoll */
  76 #if defined(HAVE_EPOLL_CREATE1) && defined(EPOLL_CLOEXEC)
  77         LTTNG_CLOEXEC = EPOLL_CLOEXEC,
  78 #else
  79         /*
  80          * EPOLL_CLOEXEC was added in glibc 2.8 (usually used in conjunction with
  81          * epoll_create1(..)), but since neither EPOLL_CLOEXEC exists nor
  82          * epoll_create1(..), we set it to FD_CLOEXEC so that we can pass it
  83          * directly to fcntl(..) instead.
  84          */
  85         LTTNG_CLOEXEC = FD_CLOEXEC,
  86 #endif
  87 };
  88
  89 struct compat_epoll_event {
  90         int epfd;
  91         uint32_t nb_fd;       /* Current number of fd in events */
  92         uint32_t alloc_size; /* Size of events array */
  93         uint32_t init_size;     /* Initial size of events array */
  94         struct epoll_event *events;
  95 };
  96 #define lttng_poll_event compat_epoll_event
  97
  98 static inline int __lttng_epoll_get_prev_fd(struct lttng_poll_event *events,
  99                 int index, uint32_t nb_fd)
 100 {
 101         assert(events);
 102         assert(index != nb_fd);
 103
 104         if (index == 0 || nb_fd == 0) {
 105                 return -1;
 106         } else {
 107                 return events->events[index - 1].data.fd;
 108         }
 109 }
 110
 111 /*
 112  * For the following calls, consider 'e' to be a lttng_poll_event pointer and i
 113  * being the index of the events array.
 114  */
 115 #define LTTNG_POLL_GETFD(e, i) LTTNG_REF(e)->events[i].data.fd
 116 #define LTTNG_POLL_GETEV(e, i) LTTNG_REF(e)->events[i].events
 117 #define LTTNG_POLL_GETNB(e) LTTNG_REF(e)->nb_fd
 118 #define LTTNG_POLL_GETSZ(e) LTTNG_REF(e)->events_size
 119 #define LTTNG_POLL_GET_PREV_FD(e, i, nb_fd) \
 120         __lttng_epoll_get_prev_fd(LTTNG_REF(e), i, nb_fd)
 121
 122 /*
 123  * Create the epoll set. No memory allocation is done here.
 124  */
 125 extern int compat_epoll_create(struct lttng_poll_event *events,
 126                 int size, int flags);
 127 #define lttng_poll_create(events, size, flags) \
 128         compat_epoll_create(events, size, flags)
 129
 130 #if defined(HAVE_EPOLL_CREATE1) && defined(EPOLL_CLOEXEC)
 131 static inline int compat_glibc_epoll_create(int size __attribute__((unused)),
 132                 int flags)
 133 {
 134         return epoll_create1(flags);
 135 }
 136 #else
 137 static inline int compat_glibc_epoll_create(int size, int flags)
 138 {
 139         /*
 140          * epoll_create1 was added in glibc 2.9, but unfortunatly reverting to
 141          * epoll_create(..) also means that we lose the possibility to
 142          * directly set the EPOLL_CLOEXEC, so try and do it anyway but through
 143          * fcntl(..).
 144          */
 145         int efd = epoll_create(size);
 146         assert(fcntl(efd, F_SETFD, flags) != -1);
 147         return efd;
 148 }
 149 #endif
 150
 151 /*
 152  * Wait on epoll set with the number of fd registered to the lttng_poll_event
 153  * data structure (events).
 154  */
 155 extern int compat_epoll_wait(struct lttng_poll_event *events, int timeout);
 156 #define lttng_poll_wait(events, timeout) \
 157         compat_epoll_wait(events, timeout)
 158
 159 /*
 160  * Add a fd to the epoll set and resize the epoll_event structure if needed.
 161  */
 162 extern int compat_epoll_add(struct lttng_poll_event *events,
 163                 int fd, uint32_t req_events);
 164 #define lttng_poll_add(events, fd, req_events) \
 165         compat_epoll_add(events, fd, req_events)
 166
 167 /*
 168  * Remove a fd from the epoll set.
 169  */
 170 extern int compat_epoll_del(struct lttng_poll_event *events, int fd);
 171 #define lttng_poll_del(events, fd) \
 172         compat_epoll_del(events, fd)
 173
 174 /*
 175  * Set up the poll set limits variable poll_max_size
 176  */
 177 extern int compat_epoll_set_max_size(void);
 178 #define lttng_poll_set_max_size() \
 179         compat_epoll_set_max_size()
 180
 181 /*
 182  * This function memset with zero the structure since it can be reused at each
 183  * round of a main loop. Being in a loop and using a non static number of fds,
 184  * this function must be called to insure coherent events with associted fds.
 185  */
 186 static inline void lttng_poll_reset(struct lttng_poll_event *events)
 187 {
 188         if (events && events->events) {
 189                 memset(events->events, 0,
 190                                 events->nb_fd * sizeof(struct epoll_event));
 191         }
 192 }
 193
 194 /*
 195  * Initialize an already allocated poll event data structure. For epoll(), the
 196  * epfd is set to -1 to indicate that it's not usable.
 197  */
 198 static inline void lttng_poll_init(struct lttng_poll_event *events)
 199 {
 200         memset(events, 0, sizeof(struct lttng_poll_event));
 201         /* Set fd to -1 so if clean before created, we don't close 0. */
 202         events->epfd = -1;
 203 }
 204
 205 /*
 206  * Clean the events structure of a lttng_poll_event. It's the caller
 207  * responsability to free the lttng_poll_event memory.
 208  */
 209 static inline void lttng_poll_clean(struct lttng_poll_event *events)
 210 {
 211         int ret;
 212
 213         if (!events) {
 214                 return;
 215         }
 216
 217         if (events->epfd >= 0) {
 218                 ret = close(events->epfd);
 219                 if (ret) {
 220                         PERROR("close");
 221                 }
 222         }
 223
 224         __lttng_poll_free((void *) events->events);
 225 }
 226
 227 #else   /* HAVE_EPOLL */
 228 /*
 229  * Fallback on poll(2) API
 230  */
 231
 232 /* Needed for some poll event values */
 233 #ifndef __USE_XOPEN
 234 #define __USE_XOPEN
 235 #endif
 236
 237 /* Needed for some poll event values */
 238 #ifndef __USE_GNU
 239 #define __USE_GNU
 240 #endif
 241
 242 #include <poll.h>
 243 #include <stdint.h>
 244
 245 enum {
 246         /* Polling variables compatibility for poll */
 247         LPOLLIN = POLLIN,
 248         LPOLLPRI = POLLPRI,
 249         LPOLLOUT = POLLOUT,
 250         LPOLLRDNORM = POLLRDNORM,
 251         LPOLLRDBAND = POLLRDBAND,
 252         LPOLLWRNORM = POLLWRNORM,
 253         LPOLLWRBAND = POLLWRBAND,
 254 #if __linux__
 255         LPOLLMSG = POLLMSG,
 256         LPOLLRDHUP = POLLRDHUP,
 257 #elif (defined(__FreeBSD__) || defined(__CYGWIN__) || defined(__sun__))
 258         LPOLLMSG = 0,
 259         LPOLLRDHUP = 0,
 260 #else
 261 #error "Please add support for your OS."
 262 #endif /* __linux__ */
 263         LPOLLERR = POLLERR,
 264         LPOLLHUP = POLLHUP | POLLNVAL,
 265         /* Close on exec feature does not exist for poll(2) */
 266         LTTNG_CLOEXEC = 0xdead,
 267 };
 268
 269 struct compat_poll_event_array {
 270         uint32_t nb_fd;       /* Current number of fd in events */
 271         uint32_t alloc_size; /* Size of events array */
 272         /* Initial size of the pollset. We never shrink below that. */
 273         uint32_t init_size;
 274         struct pollfd *events;
 275 };
 276
 277 struct compat_poll_event {
 278         /*
 279          * Modified by the wait action. Updated using current fields if the
 280          * need_update flag is set.
 281          */
 282         struct compat_poll_event_array wait;
 283         /*
 284          * This is modified by add/del actions being the _current_ flow of
 285          * execution before a poll wait is done.
 286          */
 287         struct compat_poll_event_array current;
 288
 289         /* Indicate if wait.events need to be updated from current. */
 290         int need_update:1;
 291 };
 292 #define lttng_poll_event compat_poll_event
 293
 294 static inline int __lttng_poll_get_prev_fd(struct lttng_poll_event *events,
 295                 int index, uint32_t nb_fd)
 296 {
 297         assert(events);
 298         assert(index != nb_fd);
 299
 300         if (index == 0 || nb_fd == 0) {
 301                 return -1;
 302         } else {
 303                 return events->current.events[index - 1].fd;
 304         }
 305 }
 306
 307 /*
 308  * For the following calls, consider 'e' to be a lttng_poll_event pointer and i
 309  * being the index of the events array.
 310  */
 311 #define LTTNG_POLL_GETFD(e, i) LTTNG_REF(e)->wait.events[i].fd
 312 #define LTTNG_POLL_GETEV(e, i) LTTNG_REF(e)->wait.events[i].revents
 313 #define LTTNG_POLL_GETNB(e) LTTNG_REF(e)->wait.nb_fd
 314 #define LTTNG_POLL_GETSZ(e) LTTNG_REF(e)->wait.events_size
 315 #define LTTNG_POLL_GET_PREV_FD(e, i, nb_fd) \
 316         __lttng_poll_get_prev_fd(LTTNG_REF(e), i, nb_fd)
 317
 318 /*
 319  * Create a pollfd structure of size 'size'.
 320  */
 321 extern int compat_poll_create(struct lttng_poll_event *events, int size);
 322 #define lttng_poll_create(events, size, flags) \
 323         compat_poll_create(events, size)
 324
 325 /*
 326  * Wait on poll(2) event with nb_fd registered to the lttng_poll_event data
 327  * structure.
 328  */
 329 extern int compat_poll_wait(struct lttng_poll_event *events, int timeout);
 330 #define lttng_poll_wait(events, timeout) \
 331         compat_poll_wait(events, timeout)
 332
 333 /*
 334  * Add the fd to the pollfd structure. Resize if needed.
 335  */
 336 extern int compat_poll_add(struct lttng_poll_event *events,
 337                 int fd, uint32_t req_events);
 338 #define lttng_poll_add(events, fd, req_events) \
 339         compat_poll_add(events, fd, req_events)
 340
 341 /*
 342  * Remove the fd from the pollfd. Memory allocation is done to recreate a new
 343  * pollfd, data is copied from the old pollfd to the new and, finally, the old
 344  * one is freed().
 345  */
 346 extern int compat_poll_del(struct lttng_poll_event *events, int fd);
 347 #define lttng_poll_del(events, fd) \
 348         compat_poll_del(events, fd)
 349
 350 /*
 351  * Set up the poll set limits variable poll_max_size
 352  */
 353 extern int compat_poll_set_max_size(void);
 354 #define lttng_poll_set_max_size() \
 355         compat_poll_set_max_size()
 356
 357 /*
 358  * No need to reset a pollfd structure for poll(2)
 359  */
 360 static inline void lttng_poll_reset(struct lttng_poll_event *events)
 361 {}
 362
 363 /*
 364  * Initialize an already allocated poll event data structure.
 365  */
 366 static inline void lttng_poll_init(struct lttng_poll_event *events)
 367 {
 368         memset(events, 0, sizeof(struct lttng_poll_event));
 369 }
 370
 371 /*
 372  * Clean the events structure of a lttng_poll_event. It's the caller
 373  * responsability to free the lttng_poll_event memory.
 374  */
 375 static inline void lttng_poll_clean(struct lttng_poll_event *events)
 376 {
 377         if (events) {
 378                 __lttng_poll_free((void *) events->wait.events);
 379                 __lttng_poll_free((void *) events->current.events);
 380         }
 381 }
 382
 383 #endif /* HAVE_EPOLL */
 384
 385 #endif /* _LTT_POLL_H */