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 _GNU_SOURCE
  19 #define _LGPL_SOURCE
  20 #include <assert.h>
  21 #include <fcntl.h>
  22 #include <limits.h>
  23 #include <stdlib.h>
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26 #include <unistd.h>
  27 #include <config.h>
  28
  29 #include <common/error.h>
  30 #include <common/defaults.h>
  31 #include <common/macros.h>
  32 #include <common/utils.h>
  33
  34 #include "poll.h"
  35
  36 unsigned int poll_max_size;
  37
  38 /*
  39  * Resize the epoll events structure of the new size.
  40  *
  41  * Return 0 on success or else -1 with the current events pointer untouched.
  42  */
  43 static int resize_poll_event(struct lttng_poll_event *events,
  44                 uint32_t new_size)
  45 {
  46         struct epoll_event *ptr;
  47
  48         assert(events);
  49
  50         ptr = realloc(events->events, new_size * sizeof(*ptr));
  51         if (ptr == NULL) {
  52                 PERROR("realloc epoll add");
  53                 goto error;
  54         }
  55         if (new_size > events->alloc_size) {
  56                 /* Zero newly allocated memory */
  57                 memset(ptr + events->alloc_size, 0,
  58                         (new_size - events->alloc_size) * sizeof(*ptr));
  59         }
  60         events->events = ptr;
  61         events->alloc_size = new_size;
  62
  63         return 0;
  64
  65 error:
  66         return -1;
  67 }
  68
  69 /*
  70  * Create epoll set and allocate returned events structure.
  71  */
  72 int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
  73 {
  74         int ret;
  75
  76         if (events == NULL || size <= 0) {
  77                 goto error;
  78         }
  79
  80         if (!poll_max_size) {
  81                 ERR("poll_max_size not initialized yet");
  82                 goto error;
  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  * Wait on epoll set. This is a blocking call of timeout value.
 203  */
 204 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 205 {
 206         int ret;
 207         uint32_t new_size;
 208
 209         if (events == NULL || events->events == NULL) {
 210                 ERR("Wrong arguments in compat_epoll_wait");
 211                 goto error;
 212         }
 213         assert(events->nb_fd >= 0);
 214
 215         if (events->nb_fd == 0) {
 216                 errno = EINVAL;
 217                 return -1;
 218         }
 219
 220         /*
 221          * Resize if needed before waiting. We could either expand the array or
 222          * shrink it down. It's important to note that after this step, we are
 223          * ensured that the events argument of the epoll_wait call will be large
 224          * enough to hold every possible returned events.
 225          */
 226         new_size = 1U << utils_get_count_order_u32(events->nb_fd);
 227         if (new_size != events->alloc_size && new_size >= events->init_size) {
 228                 ret = resize_poll_event(events, new_size);
 229                 if (ret < 0) {
 230                         /* ENOMEM problem at this point. */
 231                         goto error;
 232                 }
 233         }
 234
 235         do {
 236                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 237         } while (ret == -1 && errno == EINTR);
 238         if (ret < 0) {
 239                 /* At this point, every error is fatal */
 240                 PERROR("epoll_wait");
 241                 goto error;
 242         }
 243
 244         /*
 245          * Since the returned events are set sequentially in the "events" structure
 246          * we only need to return the epoll_wait value and iterate over it.
 247          */
 248         return ret;
 249
 250 error:
 251         return -1;
 252 }
 253
 254 /*
 255  * Setup poll set maximum size.
 256  */
 257 int compat_epoll_set_max_size(void)
 258 {
 259         int ret, fd, retval = 0;
 260         ssize_t size_ret;
 261         char buf[64];
 262
 263         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 264         if (fd < 0) {
 265                 retval = -1;
 266                 goto end;
 267         }
 268
 269         size_ret = lttng_read(fd, buf, sizeof(buf));
 270         /*
 271          * Allow reading a file smaller than buf, but keep space for
 272          * final \0.
 273          */
 274         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 275                 PERROR("read set max size");
 276                 retval = -1;
 277                 goto end_read;
 278         }
 279         buf[size_ret] = '\0';
 280         poll_max_size = atoi(buf);
 281 end_read:
 282         ret = close(fd);
 283         if (ret) {
 284                 PERROR("close");
 285         }
 286 end:
 287         if (!poll_max_size) {
 288                 poll_max_size = DEFAULT_POLL_SIZE;
 289         }
 290         DBG("epoll set max size is %d", poll_max_size);
 291         return retval;
 292 }