src/common/compat/compat-poll.c

   1 /*
   2  * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
   3  * Copyright (C)  2019 - Yannick Lamarre <ylamarre@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #define _LGPL_SOURCE
  20 #include <assert.h>
  21 #include <stdlib.h>
  22 #include <sys/resource.h>
  23 #include <sys/time.h>
  24 #include <stdbool.h>
  25
  26 #include <common/defaults.h>
  27 #include <common/error.h>
  28 #include <common/macros.h>
  29 #include <common/utils.h>
  30
  31 #include "poll.h"
  32
  33 unsigned int poll_max_size;
  34
  35 /*
  36  * Resize the epoll events structure of the new size.
  37  *
  38  * Return 0 on success or else -1 with the current events pointer untouched.
  39  */
  40 static int resize_poll_event(struct compat_poll_event_array *array,
  41                 uint32_t new_size)
  42 {
  43         struct pollfd *ptr;
  44
  45         assert(array);
  46
  47         /* Refuse to resize the array more than the max size. */
  48         if (new_size > poll_max_size) {
  49                 goto error;
  50         }
  51
  52         ptr = realloc(array->events, new_size * sizeof(*ptr));
  53         if (ptr == NULL) {
  54                 PERROR("realloc epoll add");
  55                 goto error;
  56         }
  57         if (new_size > array->alloc_size) {
  58                 /* Zero newly allocated memory */
  59                 memset(ptr + array->alloc_size, 0,
  60                         (new_size - array->alloc_size) * sizeof(*ptr));
  61         }
  62         array->events = ptr;
  63         array->alloc_size = new_size;
  64
  65         return 0;
  66
  67 error:
  68         return -1;
  69 }
  70
  71 /*
  72  * Update events with the current events object.
  73  */
  74 static int update_current_events(struct lttng_poll_event *events)
  75 {
  76         int ret;
  77         struct compat_poll_event_array *current, *wait;
  78
  79         assert(events);
  80
  81         current = &events->current;
  82         wait = &events->wait;
  83
  84         wait->nb_fd = current->nb_fd;
  85         if (current->alloc_size != wait->alloc_size) {
  86                 ret = resize_poll_event(wait, current->alloc_size);
  87                 if (ret < 0) {
  88                         goto error;
  89                 }
  90         }
  91         memcpy(wait->events, current->events,
  92                         current->nb_fd * sizeof(*current->events));
  93
  94         /* Update is done. */
  95         events->need_update = 0;
  96
  97         return 0;
  98
  99 error:
 100         return -1;
 101 }
 102
 103 /*
 104  * Create pollfd data structure.
 105  */
 106 int compat_poll_create(struct lttng_poll_event *events, int size)
 107 {
 108         struct compat_poll_event_array *current, *wait;
 109
 110         if (events == NULL || size <= 0) {
 111                 ERR("Wrong arguments for poll create");
 112                 goto error;
 113         }
 114
 115         if (!poll_max_size) {
 116                 if (lttng_poll_set_max_size()) {
 117                         goto error;
 118                 }
 119         }
 120
 121         /* Don't bust the limit here */
 122         if (size > poll_max_size) {
 123                 size = poll_max_size;
 124         }
 125
 126         /* Reset everything before begining the allocation. */
 127         memset(events, 0, sizeof(struct lttng_poll_event));
 128
 129         current = &events->current;
 130         wait = &events->wait;
 131
 132         /* This *must* be freed by using lttng_poll_free() */
 133         wait->events = zmalloc(size * sizeof(struct pollfd));
 134         if (wait->events == NULL) {
 135                 PERROR("zmalloc struct pollfd");
 136                 goto error;
 137         }
 138
 139         wait->alloc_size = wait->init_size = size;
 140
 141         current->events = zmalloc(size * sizeof(struct pollfd));
 142         if (current->events == NULL) {
 143                 PERROR("zmalloc struct current pollfd");
 144                 goto error;
 145         }
 146
 147         current->alloc_size = current->init_size = size;
 148
 149         return 0;
 150
 151 error:
 152         return -1;
 153 }
 154
 155 /*
 156  * Add fd to pollfd data structure with requested events.
 157  */
 158 int compat_poll_add(struct lttng_poll_event *events, int fd,
 159                 uint32_t req_events)
 160 {
 161         int new_size, ret, i;
 162         struct compat_poll_event_array *current;
 163
 164         if (events == NULL || events->current.events == NULL || fd < 0) {
 165                 ERR("Bad compat poll add arguments");
 166                 goto error;
 167         }
 168
 169         current = &events->current;
 170
 171         /* Check if fd we are trying to add is already there. */
 172         for (i = 0; i < current->nb_fd; i++) {
 173                 if (current->events[i].fd == fd) {
 174                         errno = EEXIST;
 175                         goto error;
 176                 }
 177         }
 178
 179         /* Resize array if needed. */
 180         new_size = 1U << utils_get_count_order_u32(current->nb_fd + 1);
 181         if (new_size != current->alloc_size && new_size >= current->init_size) {
 182                 ret = resize_poll_event(current, new_size);
 183                 if (ret < 0) {
 184                         goto error;
 185                 }
 186         }
 187
 188         current->events[current->nb_fd].fd = fd;
 189         current->events[current->nb_fd].events = req_events;
 190         current->nb_fd++;
 191         events->need_update = 1;
 192
 193         DBG("fd %d of %d added to pollfd", fd, current->nb_fd);
 194
 195         return 0;
 196
 197 error:
 198         return -1;
 199 }
 200
 201 /*
 202  * Modify an fd's events..
 203  */
 204 int compat_poll_mod(struct lttng_poll_event *events, int fd,
 205                 uint32_t req_events)
 206 {
 207         int i;
 208         struct compat_poll_event_array *current;
 209
 210         if (events == NULL || events->current.nb_fd == 0 ||
 211                         events->current.events == NULL || fd < 0) {
 212                 ERR("Bad compat poll mod arguments");
 213                 goto error;
 214         }
 215
 216         current = &events->current;
 217
 218         for (i = 0; i < current->nb_fd; i++) {
 219                 if (current->events[i].fd == fd) {
 220                         current->events[i].events = req_events;
 221                         events->need_update = 1;
 222                         break;
 223                 }
 224         }
 225
 226         /*
 227          * The epoll flavor doesn't flag modifying a non-included FD as an
 228          * error.
 229          */
 230
 231         return 0;
 232
 233 error:
 234         return -1;
 235 }
 236
 237 /*
 238  * Remove a fd from the pollfd structure.
 239  */
 240 int compat_poll_del(struct lttng_poll_event *events, int fd)
 241 {
 242         int i, count = 0, ret;
 243         uint32_t new_size;
 244         struct compat_poll_event_array *current;
 245
 246         if (events == NULL || events->current.nb_fd == 0 ||
 247                         events->current.events == NULL || fd < 0) {
 248                 goto error;
 249         }
 250
 251         /* Ease our life a bit. */
 252         current = &events->current;
 253
 254         for (i = 0; i < current->nb_fd; i++) {
 255                 /* Don't put back the fd we want to delete */
 256                 if (current->events[i].fd != fd) {
 257                         current->events[count].fd = current->events[i].fd;
 258                         current->events[count].events = current->events[i].events;
 259                         count++;
 260                 }
 261         }
 262
 263         /* The fd was not in our set, return no error as with epoll. */
 264         if (current->nb_fd == count) {
 265                 goto end;
 266         }
 267
 268         /* No fd duplicate should be ever added into array. */
 269         assert(current->nb_fd - 1 == count);
 270         current->nb_fd = count;
 271
 272         /* Resize array if needed. */
 273         new_size = 1U << utils_get_count_order_u32(current->nb_fd);
 274         if (new_size != current->alloc_size && new_size >= current->init_size
 275                         && current->nb_fd != 0) {
 276                 ret = resize_poll_event(current, new_size);
 277                 if (ret < 0) {
 278                         goto error;
 279                 }
 280         }
 281
 282         events->need_update = 1;
 283
 284 end:
 285         return 0;
 286
 287 error:
 288         return -1;
 289 }
 290
 291 /*
 292  * Wait on poll() with timeout. Blocking call.
 293  */
 294 int compat_poll_wait(struct lttng_poll_event *events, int timeout)
 295 {
 296         int ret, active_fd_count;
 297         int idle_pfd_index = 0;
 298         size_t i;
 299
 300         if (events == NULL || events->current.events == NULL) {
 301                 ERR("poll wait arguments error");
 302                 goto error;
 303         }
 304         assert(events->current.nb_fd >= 0);
 305
 306         if (events->current.nb_fd == 0) {
 307                 /* Return an invalid error to be consistent with epoll. */
 308                 errno = EINVAL;
 309                 events->wait.nb_fd = 0;
 310                 goto error;
 311         }
 312
 313         if (events->need_update) {
 314                 ret = update_current_events(events);
 315                 if (ret < 0) {
 316                         errno = ENOMEM;
 317                         goto error;
 318                 }
 319         }
 320
 321         do {
 322                 ret = poll(events->wait.events, events->wait.nb_fd, timeout);
 323         } while (ret == -1 && errno == EINTR);
 324         if (ret < 0) {
 325                 /* At this point, every error is fatal */
 326                 PERROR("poll wait");
 327                 goto error;
 328         }
 329
 330         active_fd_count = ret;
 331
 332         /*
 333          * Swap all active pollfd structs to the beginning of the
 334          * array to emulate compat-epoll behaviour. This algorithm takes
 335          * advantage of poll's returned value and the burst nature of active
 336          * events on the file descriptors. The while loop guarantees that
 337          * idle_pfd will always point to an idle fd.
 338          */
 339         if (active_fd_count == events->wait.nb_fd) {
 340                 goto end;
 341         }
 342         while (idle_pfd_index < active_fd_count &&
 343                         events->wait.events[idle_pfd_index].revents != 0) {
 344                 idle_pfd_index++;
 345         }
 346
 347         for (i = idle_pfd_index + 1; idle_pfd_index < active_fd_count;
 348                         i++) {
 349                 struct pollfd swap_pfd;
 350                 struct pollfd *idle_pfd = &events->wait.events[idle_pfd_index];
 351                 struct pollfd *current_pfd = &events->wait.events[i];
 352
 353                 if (idle_pfd->revents != 0) {
 354                         swap_pfd = *current_pfd;
 355                         *current_pfd = *idle_pfd;
 356                         *idle_pfd = swap_pfd;
 357                         idle_pfd_index++;
 358                 }
 359         }
 360
 361 end:
 362         return ret;
 363
 364 error:
 365         return -1;
 366 }
 367
 368 /*
 369  * Setup poll set maximum size.
 370  */
 371 int compat_poll_set_max_size(void)
 372 {
 373         int ret, retval = 0;
 374         struct rlimit lim;
 375
 376         ret = getrlimit(RLIMIT_NOFILE, &lim);
 377         if (ret < 0) {
 378                 PERROR("getrlimit poll RLIMIT_NOFILE");
 379                 retval = -1;
 380                 goto end;
 381         }
 382
 383         poll_max_size = lim.rlim_cur;
 384 end:
 385         if (poll_max_size == 0) {
 386                 poll_max_size = DEFAULT_POLL_SIZE;
 387         }
 388         DBG("poll set max size set to %u", poll_max_size);
 389         return retval;
 390 }