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 #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 <config.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         events->events = ptr;
  55         events->alloc_size = new_size;
  56
  57         return 0;
  58
  59 error:
  60         return -1;
  61 }
  62
  63 /*
  64  * Create epoll set and allocate returned events structure.
  65  */
  66 int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
  67 {
  68         int ret;
  69
  70         if (events == NULL || size <= 0) {
  71                 goto error;
  72         }
  73
  74         /* Don't bust the limit here */
  75         if (size > poll_max_size && poll_max_size != 0) {
  76                 size = poll_max_size;
  77         }
  78
  79         ret = epoll_create1(flags);
  80         if (ret < 0) {
  81                 /* At this point, every error is fatal */
  82                 PERROR("epoll_create1");
  83                 goto error;
  84         }
  85
  86         events->epfd = ret;
  87
  88         /* This *must* be freed by using lttng_poll_free() */
  89         events->events = zmalloc(size * sizeof(struct epoll_event));
  90         if (events->events == NULL) {
  91                 PERROR("zmalloc epoll set");
  92                 goto error_close;
  93         }
  94
  95         events->alloc_size = events->init_size = size;
  96         events->nb_fd = 0;
  97
  98         return 0;
  99
 100 error_close:
 101         ret = close(events->epfd);
 102         if (ret) {
 103                 PERROR("close");
 104         }
 105 error:
 106         return -1;
 107 }
 108
 109 /*
 110  * Add a fd to the epoll set with requesting events.
 111  */
 112 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 113 {
 114         int ret;
 115         struct epoll_event ev;
 116
 117         if (events == NULL || events->events == NULL || fd < 0) {
 118                 ERR("Bad compat epoll add arguments");
 119                 goto error;
 120         }
 121
 122         ev.events = req_events;
 123         ev.data.fd = fd;
 124
 125         ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
 126         if (ret < 0) {
 127                 switch (errno) {
 128                 case EEXIST:
 129                         /* If exist, it's OK. */
 130                         goto end;
 131                 case ENOSPC:
 132                 case EPERM:
 133                         /* Print PERROR and goto end not failing. Show must go on. */
 134                         PERROR("epoll_ctl ADD");
 135                         goto end;
 136                 default:
 137                         PERROR("epoll_ctl ADD fatal");
 138                         goto error;
 139                 }
 140         }
 141
 142         events->nb_fd++;
 143
 144 end:
 145         return 0;
 146
 147 error:
 148         return -1;
 149 }
 150
 151 /*
 152  * Remove a fd from the epoll set.
 153  */
 154 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 155 {
 156         int ret;
 157
 158         if (events == NULL || fd < 0) {
 159                 goto error;
 160         }
 161
 162         ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
 163         if (ret < 0) {
 164                 switch (errno) {
 165                 case ENOENT:
 166                 case EPERM:
 167                         /* Print PERROR and goto end not failing. Show must go on. */
 168                         PERROR("epoll_ctl DEL");
 169                         goto end;
 170                 default:
 171                         PERROR("epoll_ctl DEL fatal");
 172                         goto error;
 173                 }
 174         }
 175
 176         events->nb_fd--;
 177
 178 end:
 179         return 0;
 180
 181 error:
 182         return -1;
 183 }
 184
 185 /*
 186  * Wait on epoll set. This is a blocking call of timeout value.
 187  */
 188 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 189 {
 190         int ret;
 191         uint32_t new_size;
 192
 193         if (events == NULL || events->events == NULL) {
 194                 ERR("Wrong arguments in compat_epoll_wait");
 195                 goto error;
 196         }
 197
 198         /*
 199          * Resize if needed before waiting. We could either expand the array or
 200          * shrink it down. It's important to note that after this step, we are
 201          * ensured that the events argument of the epoll_wait call will be large
 202          * enough to hold every possible returned events.
 203          */
 204         if (events->nb_fd > events->alloc_size) {
 205                 /* Expand if the nb_fd is higher than the actual size. */
 206                 new_size = max_t(uint32_t,
 207                                 1U << utils_get_count_order_u32(events->nb_fd),
 208                                 events->alloc_size << 1UL);
 209         } else if ((events->nb_fd << 1UL) <= events->alloc_size &&
 210                         events->nb_fd >= events->init_size) {
 211                 /* Shrink if nb_fd multiplied by two is <= than the actual size. */
 212                 new_size = max_t(uint32_t,
 213                                 utils_get_count_order_u32(events->nb_fd) >> 1U,
 214                                 events->alloc_size >> 1U);
 215         } else {
 216                 /* Indicate that we don't want to resize. */
 217                 new_size = 0;
 218         }
 219
 220         if (new_size) {
 221                 ret = resize_poll_event(events, new_size);
 222                 if (ret < 0) {
 223                         /* ENOMEM problem at this point. */
 224                         goto error;
 225                 }
 226         }
 227
 228         do {
 229                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 230         } while (ret == -1 && errno == EINTR);
 231         if (ret < 0) {
 232                 /* At this point, every error is fatal */
 233                 PERROR("epoll_wait");
 234                 goto error;
 235         }
 236
 237         /*
 238          * Since the returned events are set sequentially in the "events" structure
 239          * we only need to return the epoll_wait value and iterate over it.
 240          */
 241         return ret;
 242
 243 error:
 244         return -1;
 245 }
 246
 247 /*
 248  * Setup poll set maximum size.
 249  */
 250 void compat_epoll_set_max_size(void)
 251 {
 252         int ret, fd;
 253         size_t size_ret;
 254         char buf[64];
 255
 256         poll_max_size = DEFAULT_POLL_SIZE;
 257
 258         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 259         if (fd < 0) {
 260                 return;
 261         }
 262
 263         size_ret = lttng_read(fd, buf, sizeof(buf));
 264         /*
 265          * Allow reading a file smaller than buf, but keep space for
 266          * final \0.
 267          */
 268         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 269                 PERROR("read set max size");
 270                 goto error;
 271         }
 272         buf[size_ret] = '\0';
 273
 274         poll_max_size = atoi(buf);
 275         if (poll_max_size == 0) {
 276                 /* Extra precaution */
 277                 poll_max_size = DEFAULT_POLL_SIZE;
 278         }
 279
 280         DBG("epoll set max size is %d", poll_max_size);
 281
 282 error:
 283         ret = close(fd);
 284         if (ret) {
 285                 PERROR("close");
 286         }
 287 }