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 #include <common/macros.h>
  27 #include <common/utils.h>
  28
  29 #include "poll.h"
  30
  31 unsigned int poll_max_size;
  32
  33 /*
  34  * Resize the epoll events structure of the new size.
  35  *
  36  * Return 0 on success or else -1 with the current events pointer untouched.
  37  */
  38 static int resize_poll_event(struct compat_poll_event_array *array,
  39                 uint32_t new_size)
  40 {
  41         struct pollfd *ptr;
  42
  43         assert(array);
  44
  45         /* Refuse to resize the array more than the max size. */
  46         if (new_size > poll_max_size) {
  47                 goto error;
  48         }
  49
  50         ptr = realloc(array->events, new_size * sizeof(*ptr));
  51         if (ptr == NULL) {
  52                 PERROR("realloc epoll add");
  53                 goto error;
  54         }
  55         if (new_size > array->alloc_size) {
  56                 /* Zero newly allocated memory */
  57                 memset(ptr + array->alloc_size, 0,
  58                         (new_size - array->alloc_size) * sizeof(*ptr));
  59         }
  60         array->events = ptr;
  61         array->alloc_size = new_size;
  62
  63         return 0;
  64
  65 error:
  66         return -1;
  67 }
  68
  69 /*
  70  * Update events with the current events object.
  71  */
  72 static int update_current_events(struct lttng_poll_event *events)
  73 {
  74         int ret;
  75         struct compat_poll_event_array *current, *wait;
  76
  77         assert(events);
  78
  79         current = &events->current;
  80         wait = &events->wait;
  81
  82         wait->nb_fd = current->nb_fd;
  83         if (events->need_realloc) {
  84                 ret = resize_poll_event(wait, current->alloc_size);
  85                 if (ret < 0) {
  86                         goto error;
  87                 }
  88         }
  89         memcpy(wait->events, current->events,
  90                         current->nb_fd * sizeof(*current->events));
  91
  92         /* Update is done and realloc as well. */
  93         events->need_update = 0;
  94         events->need_realloc = 0;
  95
  96         return 0;
  97
  98 error:
  99         return -1;
 100 }
 101
 102 /*
 103  * Create pollfd data structure.
 104  */
 105 int compat_poll_create(struct lttng_poll_event *events, int size)
 106 {
 107         struct compat_poll_event_array *current, *wait;
 108
 109         if (events == NULL || size <= 0) {
 110                 ERR("Wrong arguments for poll create");
 111                 goto error;
 112         }
 113
 114         /* Don't bust the limit here */
 115         if (size > poll_max_size) {
 116                 size = poll_max_size;
 117         }
 118
 119         /* Reset everything before begining the allocation. */
 120         memset(events, 0, sizeof(struct lttng_poll_event));
 121
 122         /* Ease our life a bit. */
 123         current = &events->current;
 124         wait = &events->wait;
 125
 126         /* This *must* be freed by using lttng_poll_free() */
 127         wait->events = zmalloc(size * sizeof(struct pollfd));
 128         if (wait->events == NULL) {
 129                 perror("zmalloc struct pollfd");
 130                 goto error;
 131         }
 132
 133         wait->alloc_size = wait->init_size = size;
 134
 135         current->events = zmalloc(size * sizeof(struct pollfd));
 136         if (current->events == NULL) {
 137                 perror("zmalloc struct current pollfd");
 138                 goto error;
 139         }
 140
 141         current->alloc_size = current->init_size = size;
 142
 143         return 0;
 144
 145 error:
 146         return -1;
 147 }
 148
 149 /*
 150  * Add fd to pollfd data structure with requested events.
 151  */
 152 int compat_poll_add(struct lttng_poll_event *events, int fd,
 153                 uint32_t req_events)
 154 {
 155         int new_size, ret, i;
 156         struct compat_poll_event_array *current;
 157
 158         if (events == NULL || events->current.events == NULL || fd < 0) {
 159                 ERR("Bad compat poll add arguments");
 160                 goto error;
 161         }
 162
 163         /* Ease our life a bit. */
 164         current = &events->current;
 165
 166         /* Check if fd we are trying to add is already there. */
 167         for (i = 0; i < current->nb_fd; i++) {
 168                 /* Don't put back the fd we want to delete */
 169                 if (current->events[i].fd == fd) {
 170                         errno = EEXIST;
 171                         goto error;
 172                 }
 173         }
 174
 175         /* Check for a needed resize of the array. */
 176         if (current->nb_fd > current->alloc_size) {
 177                 /* Expand it by a power of two of the current size. */
 178                 new_size = max_t(int,
 179                                 1U << utils_get_count_order_u32(current->nb_fd),
 180                                 current->alloc_size << 1UL);
 181                 ret = resize_poll_event(current, new_size);
 182                 if (ret < 0) {
 183                         goto error;
 184                 }
 185                 events->need_realloc = 1;
 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  * Remove a fd from the pollfd structure.
 203  */
 204 int compat_poll_del(struct lttng_poll_event *events, int fd)
 205 {
 206         int new_size, i, count = 0, ret;
 207         struct compat_poll_event_array *current;
 208
 209         if (events == NULL || events->current.events == NULL || fd < 0) {
 210                 ERR("Wrong arguments for poll del");
 211                 goto error;
 212         }
 213
 214         /* Ease our life a bit. */
 215         current = &events->current;
 216
 217         /* Check if we need to shrink it down. */
 218         if ((current->nb_fd << 1UL) <= current->alloc_size &&
 219                         current->nb_fd >= current->init_size) {
 220                 /*
 221                  * Shrink if nb_fd multiplied by two is <= than the actual size and we
 222                  * are above the initial size.
 223                  */
 224                 new_size = max_t(int,
 225                                 utils_get_count_order_u32(current->nb_fd) >> 1U,
 226                                 current->alloc_size >> 1U);
 227                 ret = resize_poll_event(current, new_size);
 228                 if (ret < 0) {
 229                         goto error;
 230                 }
 231                 events->need_realloc = 1;
 232         }
 233
 234         for (i = 0; i < current->nb_fd; i++) {
 235                 /* Don't put back the fd we want to delete */
 236                 if (current->events[i].fd != fd) {
 237                         current->events[count].fd = current->events[i].fd;
 238                         current->events[count].events = current->events[i].events;
 239                         count++;
 240                 }
 241         }
 242
 243         current->nb_fd--;
 244         events->need_update = 1;
 245
 246         return 0;
 247
 248 error:
 249         return -1;
 250 }
 251
 252 /*
 253  * Wait on poll() with timeout. Blocking call.
 254  */
 255 int compat_poll_wait(struct lttng_poll_event *events, int timeout)
 256 {
 257         int ret;
 258
 259         if (events == NULL || events->current.events == NULL) {
 260                 ERR("poll wait arguments error");
 261                 goto error;
 262         }
 263
 264         if (events->current.nb_fd == 0) {
 265                 /* Return an invalid error to be consistent with epoll. */
 266                 errno = EINVAL;
 267                 goto error;
 268         }
 269
 270         if (events->need_update) {
 271                 ret = update_current_events(events);
 272                 if (ret < 0) {
 273                         errno = ENOMEM;
 274                         goto error;
 275                 }
 276         }
 277
 278         ret = poll(events->wait.events, events->wait.nb_fd, timeout);
 279         if (ret < 0) {
 280                 /* At this point, every error is fatal */
 281                 perror("poll wait");
 282                 goto error;
 283         }
 284
 285         /*
 286          * poll() should always iterate on all FDs since we handle the pollset in
 287          * user space and after poll returns, we have to try every fd for a match.
 288          */
 289         return events->wait.nb_fd;
 290
 291 error:
 292         return -1;
 293 }
 294
 295 /*
 296  * Setup poll set maximum size.
 297  */
 298 void compat_poll_set_max_size(void)
 299 {
 300         int ret;
 301         struct rlimit lim;
 302
 303         /* Default value */
 304         poll_max_size = DEFAULT_POLL_SIZE;
 305
 306         ret = getrlimit(RLIMIT_NOFILE, &lim);
 307         if (ret < 0) {
 308                 perror("getrlimit poll RLIMIT_NOFILE");
 309                 return;
 310         }
 311
 312         poll_max_size = lim.rlim_cur;
 313         if (poll_max_size == 0) {
 314                 /* Extra precaution */
 315                 poll_max_size = DEFAULT_POLL_SIZE;
 316         }
 317
 318         DBG("poll set max size set to %u", poll_max_size);
 319 }