src/common/compat/compat-poll.c

   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 #define _GNU_SOURCE
  19 #include <assert.h>
  20 #include <stdlib.h>
  21 #include <sys/resource.h>
  22 #include <sys/time.h>
  23
  24 #include <common/defaults.h>
  25 #include <common/error.h>
  26
  27 #include "poll.h"
  28
  29 unsigned int poll_max_size;
  30
  31 /*
  32  * Resize the epoll events structure of the new size.
  33  *
  34  * Return 0 on success or else -1 with the current events pointer untouched.
  35  */
  36 static int resize_poll_event(struct compat_poll_event_array *array,
  37                 uint32_t new_size)
  38 {
  39         struct pollfd *ptr;
  40
  41         assert(array);
  42
  43         ptr = realloc(array->events, new_size * sizeof(*ptr));
  44         if (ptr == NULL) {
  45                 PERROR("realloc epoll add");
  46                 goto error;
  47         }
  48         array->events = ptr;
  49         array->alloc_size = new_size;
  50
  51         return 0;
  52
  53 error:
  54         return -1;
  55 }
  56
  57 /*
  58  * Update events with the current events object.
  59  */
  60 static int update_current_events(struct lttng_poll_event *events)
  61 {
  62         int ret;
  63         struct compat_poll_event_array *current, *wait;
  64
  65         assert(events);
  66
  67         current = &events->current;
  68         wait = &events->wait;
  69
  70         wait->nb_fd = current->nb_fd;
  71         if (events->need_realloc) {
  72                 ret = resize_poll_event(wait, current->alloc_size);
  73                 if (ret < 0) {
  74                         goto error;
  75                 }
  76         }
  77         memcpy(wait->events, current->events,
  78                         current->nb_fd * sizeof(*current->events));
  79
  80         /* Update is done and realloc as well. */
  81         events->need_update = 0;
  82         events->need_realloc = 0;
  83
  84         return 0;
  85
  86 error:
  87         return -1;
  88 }
  89
  90 /*
  91  * Create pollfd data structure.
  92  */
  93 int compat_poll_create(struct lttng_poll_event *events, int size)
  94 {
  95         struct compat_poll_event_array *current, *wait;
  96
  97         if (events == NULL || size <= 0) {
  98                 ERR("Wrong arguments for poll create");
  99                 goto error;
 100         }
 101
 102         /* Don't bust the limit here */
 103         if (size > poll_max_size) {
 104                 size = poll_max_size;
 105         }
 106
 107         /* Reset everything before begining the allocation. */
 108         memset(events, 0, sizeof(struct lttng_poll_event));
 109
 110         /* Ease our life a bit. */
 111         current = &events->current;
 112         wait = &events->wait;
 113
 114         /* This *must* be freed by using lttng_poll_free() */
 115         wait->events = zmalloc(size * sizeof(struct pollfd));
 116         if (wait->events == NULL) {
 117                 perror("zmalloc struct pollfd");
 118                 goto error;
 119         }
 120
 121         wait->alloc_size = wait->init_size = size;
 122
 123         current->events = zmalloc(size * sizeof(struct pollfd));
 124         if (current->events == NULL) {
 125                 perror("zmalloc struct current pollfd");
 126                 goto error;
 127         }
 128
 129         current->alloc_size = current->init_size = size;
 130
 131         return 0;
 132
 133 error:
 134         return -1;
 135 }
 136
 137 /*
 138  * Add fd to pollfd data structure with requested events.
 139  */
 140 int compat_poll_add(struct lttng_poll_event *events, int fd,
 141                 uint32_t req_events)
 142 {
 143         int new_size, ret, i;
 144         struct compat_poll_event_array *current;
 145
 146         if (events == NULL || events->current.events == NULL || fd < 0) {
 147                 ERR("Bad compat poll add arguments");
 148                 goto error;
 149         }
 150
 151         /* Ease our life a bit. */
 152         current = &events->current;
 153
 154         /* Check if fd we are trying to add is already there. */
 155         for (i = 0; i < current->nb_fd; i++) {
 156                 /* Don't put back the fd we want to delete */
 157                 if (current->events[i].fd == fd) {
 158                         errno = EEXIST;
 159                         goto error;
 160                 }
 161         }
 162
 163         /* Check for a needed resize of the array. */
 164         if (current->nb_fd > current->alloc_size) {
 165                 /* Expand it by a power of two of the current size. */
 166                 new_size = current->alloc_size << 1UL;
 167                 ret = resize_poll_event(current, new_size);
 168                 if (ret < 0) {
 169                         goto error;
 170                 }
 171                 events->need_realloc = 1;
 172         }
 173
 174         current->events[current->nb_fd].fd = fd;
 175         current->events[current->nb_fd].events = req_events;
 176         current->nb_fd++;
 177         events->need_update = 1;
 178
 179         DBG("fd %d of %d added to pollfd", fd, current->nb_fd);
 180
 181         return 0;
 182
 183 error:
 184         return -1;
 185 }
 186
 187 /*
 188  * Remove a fd from the pollfd structure.
 189  */
 190 int compat_poll_del(struct lttng_poll_event *events, int fd)
 191 {
 192         int new_size, i, count = 0, ret;
 193         struct compat_poll_event_array *current;
 194
 195         if (events == NULL || events->current.events == NULL || fd < 0) {
 196                 ERR("Wrong arguments for poll del");
 197                 goto error;
 198         }
 199
 200         /* Ease our life a bit. */
 201         current = &events->current;
 202
 203         /* Safety check on size */
 204         if (new_size > poll_max_size) {
 205                 new_size = poll_max_size;
 206         }
 207
 208         /* Check if we need to shrink it down. */
 209         if ((current->nb_fd << 1UL) <= current->alloc_size &&
 210                         current->nb_fd >= current->init_size) {
 211                 /*
 212                  * Shrink if nb_fd multiplied by two is <= than the actual size and we
 213                  * are above the initial size.
 214                  */
 215                 new_size = current->alloc_size >> 1UL;
 216                 ret = resize_poll_event(current, new_size);
 217                 if (ret < 0) {
 218                         goto error;
 219                 }
 220                 events->need_realloc = 1;
 221         }
 222
 223         for (i = 0; i < current->nb_fd; i++) {
 224                 /* Don't put back the fd we want to delete */
 225                 if (current->events[i].fd != fd) {
 226                         current->events[count].fd = current->events[i].fd;
 227                         current->events[count].events = current->events[i].events;
 228                         count++;
 229                 }
 230         }
 231
 232         current->nb_fd--;
 233         events->need_update = 1;
 234
 235         return 0;
 236
 237 error:
 238         return -1;
 239 }
 240
 241 /*
 242  * Wait on poll() with timeout. Blocking call.
 243  */
 244 int compat_poll_wait(struct lttng_poll_event *events, int timeout)
 245 {
 246         int ret;
 247
 248         if (events == NULL || events->current.events == NULL) {
 249                 ERR("poll wait arguments error");
 250                 goto error;
 251         }
 252
 253         if (events->current.nb_fd == 0) {
 254                 /* Return an invalid error to be consistent with epoll. */
 255                 errno = EINVAL;
 256                 goto error;
 257         }
 258
 259         if (events->need_update) {
 260                 ret = update_current_events(events);
 261                 if (ret < 0) {
 262                         errno = ENOMEM;
 263                         goto error;
 264                 }
 265         }
 266
 267         ret = poll(events->wait.events, events->wait.nb_fd, timeout);
 268         if (ret < 0) {
 269                 /* At this point, every error is fatal */
 270                 perror("poll wait");
 271                 goto error;
 272         }
 273
 274         /*
 275          * poll() should always iterate on all FDs since we handle the pollset in
 276          * user space and after poll returns, we have to try every fd for a match.
 277          */
 278         return events->wait.nb_fd;
 279
 280 error:
 281         return -1;
 282 }
 283
 284 /*
 285  * Setup poll set maximum size.
 286  */
 287 void compat_poll_set_max_size(void)
 288 {
 289         int ret;
 290         struct rlimit lim;
 291
 292         /* Default value */
 293         poll_max_size = DEFAULT_POLL_SIZE;
 294
 295         ret = getrlimit(RLIMIT_NOFILE, &lim);
 296         if (ret < 0) {
 297                 perror("getrlimit poll RLIMIT_NOFILE");
 298                 return;
 299         }
 300
 301         poll_max_size = lim.rlim_cur;
 302         if (poll_max_size == 0) {
 303                 /* Extra precaution */
 304                 poll_max_size = DEFAULT_POLL_SIZE;
 305         }
 306
 307         DBG("poll set max size set to %u", poll_max_size);
 308 }