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
  27 #include <common/error.h>
  28 #include <common/defaults.h>
  29 #include <common/macros.h>
  30 #include <common/utils.h>
  31
  32 #include "poll.h"
  33
  34 unsigned int poll_max_size;
  35
  36 /*
  37  * Resize the epoll events structure of the new size.
  38  *
  39  * Return 0 on success or else -1 with the current events pointer untouched.
  40  */
  41 static int resize_poll_event(struct lttng_poll_event *events,
  42                 uint32_t new_size)
  43 {
  44         struct epoll_event *ptr;
  45
  46         assert(events);
  47
  48         ptr = realloc(events->events, new_size * sizeof(*ptr));
  49         if (ptr == NULL) {
  50                 PERROR("realloc epoll add");
  51                 goto error;
  52         }
  53         if (new_size > events->alloc_size) {
  54                 /* Zero newly allocated memory */
  55                 memset(ptr + events->alloc_size, 0,
  56                         (new_size - events->alloc_size) * sizeof(*ptr));
  57         }
  58         events->events = ptr;
  59         events->alloc_size = new_size;
  60
  61         return 0;
  62
  63 error:
  64         return -1;
  65 }
  66
  67 /*
  68  * Create epoll set and allocate returned events structure.
  69  */
  70 LTTNG_HIDDEN
  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 LTTNG_HIDDEN
 124 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 125 {
 126         int ret;
 127         struct epoll_event ev;
 128
 129         if (events == NULL || events->events == NULL || fd < 0) {
 130                 ERR("Bad compat epoll add arguments");
 131                 goto error;
 132         }
 133
 134         /*
 135          * Zero struct epoll_event to ensure all representations of its
 136          * union are zeroed.
 137          */
 138         memset(&ev, 0, sizeof(ev));
 139         ev.events = req_events;
 140         ev.data.fd = fd;
 141
 142         ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
 143         if (ret < 0) {
 144                 switch (errno) {
 145                 case EEXIST:
 146                         /* If exist, it's OK. */
 147                         goto end;
 148                 case ENOSPC:
 149                 case EPERM:
 150                         /* Print PERROR and goto end not failing. Show must go on. */
 151                         PERROR("epoll_ctl ADD");
 152                         goto end;
 153                 default:
 154                         PERROR("epoll_ctl ADD fatal");
 155                         goto error;
 156                 }
 157         }
 158
 159         events->nb_fd++;
 160
 161 end:
 162         return 0;
 163
 164 error:
 165         return -1;
 166 }
 167
 168 /*
 169  * Remove a fd from the epoll set.
 170  */
 171 LTTNG_HIDDEN
 172 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 173 {
 174         int ret;
 175
 176         if (events == NULL || fd < 0 || events->nb_fd == 0) {
 177                 goto error;
 178         }
 179
 180         ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
 181         if (ret < 0) {
 182                 switch (errno) {
 183                 case ENOENT:
 184                 case EPERM:
 185                         /* Print PERROR and goto end not failing. Show must go on. */
 186                         PERROR("epoll_ctl DEL");
 187                         goto end;
 188                 default:
 189                         PERROR("epoll_ctl DEL fatal");
 190                         goto error;
 191                 }
 192         }
 193
 194         events->nb_fd--;
 195
 196 end:
 197         return 0;
 198
 199 error:
 200         return -1;
 201 }
 202
 203 /*
 204  * Set an fd's events.
 205  */
 206 LTTNG_HIDDEN
 207 int compat_epoll_mod(struct lttng_poll_event *events, int fd, uint32_t req_events)
 208 {
 209         int ret;
 210         struct epoll_event ev;
 211
 212         if (events == NULL || fd < 0 || events->nb_fd == 0) {
 213                 goto error;
 214         }
 215
 216         /*
 217          * Zero struct epoll_event to ensure all representations of its
 218          * union are zeroed.
 219          */
 220         memset(&ev, 0, sizeof(ev));
 221         ev.events = req_events;
 222         ev.data.fd = fd;
 223
 224         ret = epoll_ctl(events->epfd, EPOLL_CTL_MOD, fd, &ev);
 225         if (ret < 0) {
 226                 switch (errno) {
 227                 case ENOENT:
 228                 case EPERM:
 229                         /* Print PERROR and goto end not failing. Show must go on. */
 230                         PERROR("epoll_ctl MOD");
 231                         goto end;
 232                 default:
 233                         PERROR("epoll_ctl MOD fatal");
 234                         goto error;
 235                 }
 236         }
 237
 238 end:
 239         return 0;
 240
 241 error:
 242         return -1;
 243 }
 244
 245 /*
 246  * Wait on epoll set. This is a blocking call of timeout value.
 247  */
 248 LTTNG_HIDDEN
 249 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 250 {
 251         int ret;
 252         uint32_t new_size;
 253
 254         if (events == NULL || events->events == NULL) {
 255                 ERR("Wrong arguments in compat_epoll_wait");
 256                 goto error;
 257         }
 258
 259         if (events->nb_fd == 0) {
 260                 errno = EINVAL;
 261                 return -1;
 262         }
 263
 264         /*
 265          * Resize if needed before waiting. We could either expand the array or
 266          * shrink it down. It's important to note that after this step, we are
 267          * ensured that the events argument of the epoll_wait call will be large
 268          * enough to hold every possible returned events.
 269          */
 270         new_size = 1U << utils_get_count_order_u32(events->nb_fd);
 271         if (new_size != events->alloc_size && new_size >= events->init_size) {
 272                 ret = resize_poll_event(events, new_size);
 273                 if (ret < 0) {
 274                         /* ENOMEM problem at this point. */
 275                         goto error;
 276                 }
 277         }
 278
 279         do {
 280                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 281         } while (ret == -1 && errno == EINTR);
 282         if (ret < 0) {
 283                 /* At this point, every error is fatal */
 284                 PERROR("epoll_wait");
 285                 goto error;
 286         }
 287
 288         /*
 289          * Since the returned events are set sequentially in the "events" structure
 290          * we only need to return the epoll_wait value and iterate over it.
 291          */
 292         return ret;
 293
 294 error:
 295         return -1;
 296 }
 297
 298 /*
 299  * Setup poll set maximum size.
 300  */
 301 LTTNG_HIDDEN
 302 int compat_epoll_set_max_size(void)
 303 {
 304         int ret, fd, retval = 0;
 305         ssize_t size_ret;
 306         char buf[64];
 307
 308         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 309         if (fd < 0) {
 310                 /*
 311                  * Failing on opening [1] is not an error per see. [1] was
 312                  * introduced in Linux 2.6.28 but epoll is available since
 313                  * 2.5.44. Hence, goto end and set a default value without
 314                  * setting an error return value.
 315                  *
 316                  * [1] /proc/sys/fs/epoll/max_user_watches
 317                  */
 318                 retval = 0;
 319                 goto end;
 320         }
 321
 322         size_ret = lttng_read(fd, buf, sizeof(buf));
 323         /*
 324          * Allow reading a file smaller than buf, but keep space for
 325          * final \0.
 326          */
 327         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 328                 PERROR("read set max size");
 329                 retval = -1;
 330                 goto end_read;
 331         }
 332         buf[size_ret] = '\0';
 333         poll_max_size = atoi(buf);
 334 end_read:
 335         ret = close(fd);
 336         if (ret) {
 337                 PERROR("close");
 338         }
 339 end:
 340         if (!poll_max_size) {
 341                 poll_max_size = DEFAULT_POLL_SIZE;
 342         }
 343         DBG("epoll set max size is %d", poll_max_size);
 344         return retval;
 345 }