src/common/compat/compat-epoll.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 _LGPL_SOURCE
  19 #include <assert.h>
  20 #include <fcntl.h>
  21 #include <limits.h>
  22 #include <stdlib.h>
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <unistd.h>
  26 #include <stdbool.h>
  27
  28 #include <common/error.h>
  29 #include <common/defaults.h>
  30 #include <common/macros.h>
  31 #include <common/utils.h>
  32
  33 #include "poll.h"
  34
  35 unsigned int poll_max_size;
  36
  37 /*
  38  * Resize the epoll events structure of the new size.
  39  *
  40  * Return 0 on success or else -1 with the current events pointer untouched.
  41  */
  42 static int resize_poll_event(struct lttng_poll_event *events,
  43                 uint32_t new_size)
  44 {
  45         struct epoll_event *ptr;
  46
  47         assert(events);
  48
  49         ptr = realloc(events->events, new_size * sizeof(*ptr));
  50         if (ptr == NULL) {
  51                 PERROR("realloc epoll add");
  52                 goto error;
  53         }
  54         if (new_size > events->alloc_size) {
  55                 /* Zero newly allocated memory */
  56                 memset(ptr + events->alloc_size, 0,
  57                         (new_size - events->alloc_size) * sizeof(*ptr));
  58         }
  59         events->events = ptr;
  60         events->alloc_size = new_size;
  61
  62         return 0;
  63
  64 error:
  65         return -1;
  66 }
  67
  68 /*
  69  * Create epoll set and allocate returned events structure.
  70  */
  71 int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
  72 {
  73         int ret;
  74
  75         if (events == NULL || size <= 0) {
  76                 goto error;
  77         }
  78
  79         if (!poll_max_size) {
  80                 if (lttng_poll_set_max_size()) {
  81                         goto error;
  82                 }
  83         }
  84
  85         /* Don't bust the limit here */
  86         if (size > poll_max_size) {
  87                 size = poll_max_size;
  88         }
  89
  90         ret = compat_glibc_epoll_create(size, flags);
  91         if (ret < 0) {
  92                 /* At this point, every error is fatal */
  93                 PERROR("epoll_create1");
  94                 goto error;
  95         }
  96
  97         events->epfd = ret;
  98
  99         /* This *must* be freed by using lttng_poll_free() */
 100         events->events = zmalloc(size * sizeof(struct epoll_event));
 101         if (events->events == NULL) {
 102                 PERROR("zmalloc epoll set");
 103                 goto error_close;
 104         }
 105
 106         events->alloc_size = events->init_size = size;
 107         events->nb_fd = 0;
 108
 109         return 0;
 110
 111 error_close:
 112         ret = close(events->epfd);
 113         if (ret) {
 114                 PERROR("close");
 115         }
 116 error:
 117         return -1;
 118 }
 119
 120 /*
 121  * Add a fd to the epoll set with requesting events.
 122  */
 123 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 124 {
 125         int ret;
 126         struct epoll_event ev;
 127
 128         if (events == NULL || events->events == NULL || fd < 0) {
 129                 ERR("Bad compat epoll add arguments");
 130                 goto error;
 131         }
 132
 133         /*
 134          * Zero struct epoll_event to ensure all representations of its
 135          * union are zeroed.
 136          */
 137         memset(&ev, 0, sizeof(ev));
 138         ev.events = req_events;
 139         ev.data.fd = fd;
 140
 141         ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
 142         if (ret < 0) {
 143                 switch (errno) {
 144                 case EEXIST:
 145                         /* If exist, it's OK. */
 146                         goto end;
 147                 case ENOSPC:
 148                 case EPERM:
 149                         /* Print PERROR and goto end not failing. Show must go on. */
 150                         PERROR("epoll_ctl ADD");
 151                         goto end;
 152                 default:
 153                         PERROR("epoll_ctl ADD fatal");
 154                         goto error;
 155                 }
 156         }
 157
 158         events->nb_fd++;
 159
 160 end:
 161         return 0;
 162
 163 error:
 164         return -1;
 165 }
 166
 167 /*
 168  * Remove a fd from the epoll set.
 169  */
 170 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 171 {
 172         int ret;
 173
 174         if (events == NULL || fd < 0 || events->nb_fd == 0) {
 175                 goto error;
 176         }
 177
 178         ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
 179         if (ret < 0) {
 180                 switch (errno) {
 181                 case ENOENT:
 182                 case EPERM:
 183                         /* Print PERROR and goto end not failing. Show must go on. */
 184                         PERROR("epoll_ctl DEL");
 185                         goto end;
 186                 default:
 187                         PERROR("epoll_ctl DEL fatal");
 188                         goto error;
 189                 }
 190         }
 191
 192         events->nb_fd--;
 193
 194 end:
 195         return 0;
 196
 197 error:
 198         return -1;
 199 }
 200
 201 /*
 202  * Set an fd's events.
 203  */
 204 int compat_epoll_mod(struct lttng_poll_event *events, int fd, uint32_t req_events)
 205 {
 206         int ret;
 207         struct epoll_event ev;
 208
 209         if (events == NULL || fd < 0 || events->nb_fd == 0) {
 210                 goto error;
 211         }
 212
 213         /*
 214          * Zero struct epoll_event to ensure all representations of its
 215          * union are zeroed.
 216          */
 217         memset(&ev, 0, sizeof(ev));
 218         ev.events = req_events;
 219         ev.data.fd = fd;
 220
 221         ret = epoll_ctl(events->epfd, EPOLL_CTL_MOD, fd, &ev);
 222         if (ret < 0) {
 223                 switch (errno) {
 224                 case ENOENT:
 225                 case EPERM:
 226                         /* Print PERROR and goto end not failing. Show must go on. */
 227                         PERROR("epoll_ctl MOD");
 228                         goto end;
 229                 default:
 230                         PERROR("epoll_ctl MOD fatal");
 231                         goto error;
 232                 }
 233         }
 234
 235 end:
 236         return 0;
 237
 238 error:
 239         return -1;
 240 }
 241
 242 /*
 243  * Wait on epoll set. This is a blocking call of timeout value.
 244  */
 245 int compat_epoll_wait(struct lttng_poll_event *events, int timeout,
 246                 bool interruptible)
 247 {
 248         int ret;
 249         uint32_t new_size;
 250
 251         if (events == NULL || events->events == NULL) {
 252                 ERR("Wrong arguments in compat_epoll_wait");
 253                 goto error;
 254         }
 255
 256         if (events->nb_fd == 0) {
 257                 errno = EINVAL;
 258                 return -1;
 259         }
 260
 261         /*
 262          * Resize if needed before waiting. We could either expand the array or
 263          * shrink it down. It's important to note that after this step, we are
 264          * ensured that the events argument of the epoll_wait call will be large
 265          * enough to hold every possible returned events.
 266          */
 267         new_size = 1U << utils_get_count_order_u32(events->nb_fd);
 268         if (new_size != events->alloc_size && new_size >= events->init_size) {
 269                 ret = resize_poll_event(events, new_size);
 270                 if (ret < 0) {
 271                         /* ENOMEM problem at this point. */
 272                         goto error;
 273                 }
 274         }
 275
 276         do {
 277                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 278         } while (!interruptible && ret == -1 && errno == EINTR);
 279         if (ret < 0) {
 280                 if (errno != EINTR) {
 281                         PERROR("epoll_wait");
 282                 }
 283                 goto error;
 284         }
 285
 286         /*
 287          * Since the returned events are set sequentially in the "events" structure
 288          * we only need to return the epoll_wait value and iterate over it.
 289          */
 290         return ret;
 291
 292 error:
 293         return -1;
 294 }
 295
 296 /*
 297  * Setup poll set maximum size.
 298  */
 299 int compat_epoll_set_max_size(void)
 300 {
 301         int ret, fd, retval = 0;
 302         ssize_t size_ret;
 303         char buf[64];
 304
 305         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 306         if (fd < 0) {
 307                 /*
 308                  * Failing on opening [1] is not an error per see. [1] was
 309                  * introduced in Linux 2.6.28 but epoll is available since
 310                  * 2.5.44. Hence, goto end and set a default value without
 311                  * setting an error return value.
 312                  *
 313                  * [1] /proc/sys/fs/epoll/max_user_watches
 314                  */
 315                 retval = 0;
 316                 goto end;
 317         }
 318
 319         size_ret = lttng_read(fd, buf, sizeof(buf));
 320         /*
 321          * Allow reading a file smaller than buf, but keep space for
 322          * final \0.
 323          */
 324         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 325                 PERROR("read set max size");
 326                 retval = -1;
 327                 goto end_read;
 328         }
 329         buf[size_ret] = '\0';
 330         poll_max_size = atoi(buf);
 331 end_read:
 332         ret = close(fd);
 333         if (ret) {
 334                 PERROR("close");
 335         }
 336 end:
 337         if (!poll_max_size) {
 338                 poll_max_size = DEFAULT_POLL_SIZE;
 339         }
 340         DBG("epoll set max size is %d", poll_max_size);
 341         return retval;
 342 }