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         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         /* Don't bust the limit here */
  80         if (size > poll_max_size && poll_max_size != 0) {
  81                 size = poll_max_size;
  82         }
  83
  84         ret = compat_glibc_epoll_create(size, flags);
  85         if (ret < 0) {
  86                 /* At this point, every error is fatal */
  87                 PERROR("epoll_create1");
  88                 goto error;
  89         }
  90
  91         events->epfd = ret;
  92
  93         /* This *must* be freed by using lttng_poll_free() */
  94         events->events = zmalloc(size * sizeof(struct epoll_event));
  95         if (events->events == NULL) {
  96                 PERROR("zmalloc epoll set");
  97                 goto error_close;
  98         }
  99
 100         events->alloc_size = events->init_size = size;
 101         events->nb_fd = 0;
 102
 103         return 0;
 104
 105 error_close:
 106         ret = close(events->epfd);
 107         if (ret) {
 108                 PERROR("close");
 109         }
 110 error:
 111         return -1;
 112 }
 113
 114 /*
 115  * Add a fd to the epoll set with requesting events.
 116  */
 117 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 118 {
 119         int ret;
 120         struct epoll_event ev;
 121
 122         if (events == NULL || events->events == NULL || fd < 0) {
 123                 ERR("Bad compat epoll add arguments");
 124                 goto error;
 125         }
 126
 127         /*
 128          * Zero struct epoll_event to ensure all representations of its
 129          * union are zeroed.
 130          */
 131         memset(&ev, 0, sizeof(ev));
 132         ev.events = req_events;
 133         ev.data.fd = fd;
 134
 135         ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
 136         if (ret < 0) {
 137                 switch (errno) {
 138                 case EEXIST:
 139                         /* If exist, it's OK. */
 140                         goto end;
 141                 case ENOSPC:
 142                 case EPERM:
 143                         /* Print PERROR and goto end not failing. Show must go on. */
 144                         PERROR("epoll_ctl ADD");
 145                         goto end;
 146                 default:
 147                         PERROR("epoll_ctl ADD fatal");
 148                         goto error;
 149                 }
 150         }
 151
 152         events->nb_fd++;
 153
 154 end:
 155         return 0;
 156
 157 error:
 158         return -1;
 159 }
 160
 161 /*
 162  * Remove a fd from the epoll set.
 163  */
 164 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 165 {
 166         int ret;
 167
 168         if (events == NULL || fd < 0) {
 169                 goto error;
 170         }
 171
 172         ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
 173         if (ret < 0) {
 174                 switch (errno) {
 175                 case ENOENT:
 176                 case EPERM:
 177                         /* Print PERROR and goto end not failing. Show must go on. */
 178                         PERROR("epoll_ctl DEL");
 179                         goto end;
 180                 default:
 181                         PERROR("epoll_ctl DEL fatal");
 182                         goto error;
 183                 }
 184         }
 185
 186         events->nb_fd--;
 187
 188 end:
 189         return 0;
 190
 191 error:
 192         return -1;
 193 }
 194
 195 /*
 196  * Wait on epoll set. This is a blocking call of timeout value.
 197  */
 198 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 199 {
 200         int ret;
 201         uint32_t new_size;
 202
 203         if (events == NULL || events->events == NULL) {
 204                 ERR("Wrong arguments in compat_epoll_wait");
 205                 goto error;
 206         }
 207
 208         /*
 209          * Resize if needed before waiting. We could either expand the array or
 210          * shrink it down. It's important to note that after this step, we are
 211          * ensured that the events argument of the epoll_wait call will be large
 212          * enough to hold every possible returned events.
 213          */
 214         if (events->nb_fd > events->alloc_size) {
 215                 /* Expand if the nb_fd is higher than the actual size. */
 216                 new_size = max_t(uint32_t,
 217                                 1U << utils_get_count_order_u32(events->nb_fd),
 218                                 events->alloc_size << 1UL);
 219         } else if ((events->nb_fd << 1UL) <= events->alloc_size &&
 220                         events->nb_fd >= events->init_size) {
 221                 /* Shrink if nb_fd multiplied by two is <= than the actual size. */
 222                 new_size = max_t(uint32_t,
 223                                 utils_get_count_order_u32(events->nb_fd) >> 1U,
 224                                 events->alloc_size >> 1U);
 225         } else {
 226                 /* Indicate that we don't want to resize. */
 227                 new_size = 0;
 228         }
 229
 230         if (new_size) {
 231                 ret = resize_poll_event(events, new_size);
 232                 if (ret < 0) {
 233                         /* ENOMEM problem at this point. */
 234                         goto error;
 235                 }
 236         }
 237
 238         do {
 239                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 240         } while (ret == -1 && errno == EINTR);
 241         if (ret < 0) {
 242                 /* At this point, every error is fatal */
 243                 PERROR("epoll_wait");
 244                 goto error;
 245         }
 246
 247         /*
 248          * Since the returned events are set sequentially in the "events" structure
 249          * we only need to return the epoll_wait value and iterate over it.
 250          */
 251         return ret;
 252
 253 error:
 254         return -1;
 255 }
 256
 257 /*
 258  * Setup poll set maximum size.
 259  */
 260 void compat_epoll_set_max_size(void)
 261 {
 262         int ret, fd;
 263         ssize_t size_ret;
 264         char buf[64];
 265
 266         poll_max_size = DEFAULT_POLL_SIZE;
 267
 268         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 269         if (fd < 0) {
 270                 return;
 271         }
 272
 273         size_ret = lttng_read(fd, buf, sizeof(buf));
 274         /*
 275          * Allow reading a file smaller than buf, but keep space for
 276          * final \0.
 277          */
 278         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 279                 PERROR("read set max size");
 280                 goto error;
 281         }
 282         buf[size_ret] = '\0';
 283
 284         poll_max_size = atoi(buf);
 285         if (poll_max_size == 0) {
 286                 /* Extra precaution */
 287                 poll_max_size = DEFAULT_POLL_SIZE;
 288         }
 289
 290         DBG("epoll set max size is %d", poll_max_size);
 291
 292 error:
 293         ret = close(fd);
 294         if (ret) {
 295                 PERROR("close");
 296         }
 297 }