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         /* Don't bust the limit here */
  81         if (size > poll_max_size && poll_max_size != 0) {
  82                 size = poll_max_size;
  83         }
  84
  85         ret = compat_glibc_epoll_create(size, flags);
  86         if (ret < 0) {
  87                 /* At this point, every error is fatal */
  88                 PERROR("epoll_create1");
  89                 goto error;
  90         }
  91
  92         events->epfd = ret;
  93
  94         /* This *must* be freed by using lttng_poll_free() */
  95         events->events = zmalloc(size * sizeof(struct epoll_event));
  96         if (events->events == NULL) {
  97                 PERROR("zmalloc epoll set");
  98                 goto error_close;
  99         }
 100
 101         events->alloc_size = events->init_size = size;
 102         events->nb_fd = 0;
 103
 104         return 0;
 105
 106 error_close:
 107         ret = close(events->epfd);
 108         if (ret) {
 109                 PERROR("close");
 110         }
 111 error:
 112         return -1;
 113 }
 114
 115 /*
 116  * Add a fd to the epoll set with requesting events.
 117  */
 118 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 119 {
 120         int ret;
 121         struct epoll_event ev;
 122
 123         if (events == NULL || events->events == NULL || fd < 0) {
 124                 ERR("Bad compat epoll add arguments");
 125                 goto error;
 126         }
 127
 128         /*
 129          * Zero struct epoll_event to ensure all representations of its
 130          * union are zeroed.
 131          */
 132         memset(&ev, 0, sizeof(ev));
 133         ev.events = req_events;
 134         ev.data.fd = fd;
 135
 136         ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
 137         if (ret < 0) {
 138                 switch (errno) {
 139                 case EEXIST:
 140                         /* If exist, it's OK. */
 141                         goto end;
 142                 case ENOSPC:
 143                 case EPERM:
 144                         /* Print PERROR and goto end not failing. Show must go on. */
 145                         PERROR("epoll_ctl ADD");
 146                         goto end;
 147                 default:
 148                         PERROR("epoll_ctl ADD fatal");
 149                         goto error;
 150                 }
 151         }
 152
 153         events->nb_fd++;
 154
 155 end:
 156         return 0;
 157
 158 error:
 159         return -1;
 160 }
 161
 162 /*
 163  * Remove a fd from the epoll set.
 164  */
 165 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 166 {
 167         int ret;
 168
 169         if (events == NULL || fd < 0) {
 170                 goto error;
 171         }
 172
 173         ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
 174         if (ret < 0) {
 175                 switch (errno) {
 176                 case ENOENT:
 177                 case EPERM:
 178                         /* Print PERROR and goto end not failing. Show must go on. */
 179                         PERROR("epoll_ctl DEL");
 180                         goto end;
 181                 default:
 182                         PERROR("epoll_ctl DEL fatal");
 183                         goto error;
 184                 }
 185         }
 186
 187         events->nb_fd--;
 188
 189 end:
 190         return 0;
 191
 192 error:
 193         return -1;
 194 }
 195
 196 /*
 197  * Wait on epoll set. This is a blocking call of timeout value.
 198  */
 199 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 200 {
 201         int ret;
 202         uint32_t new_size;
 203
 204         if (events == NULL || events->events == NULL) {
 205                 ERR("Wrong arguments in compat_epoll_wait");
 206                 goto error;
 207         }
 208
 209         /*
 210          * Resize if needed before waiting. We could either expand the array or
 211          * shrink it down. It's important to note that after this step, we are
 212          * ensured that the events argument of the epoll_wait call will be large
 213          * enough to hold every possible returned events.
 214          */
 215         if (events->nb_fd > events->alloc_size) {
 216                 /* Expand if the nb_fd is higher than the actual size. */
 217                 new_size = max_t(uint32_t,
 218                                 1U << utils_get_count_order_u32(events->nb_fd),
 219                                 events->alloc_size << 1UL);
 220         } else if ((events->nb_fd << 1UL) <= events->alloc_size &&
 221                         events->nb_fd >= events->init_size) {
 222                 /* Shrink if nb_fd multiplied by two is <= than the actual size. */
 223                 new_size = max_t(uint32_t,
 224                                 utils_get_count_order_u32(events->nb_fd) >> 1U,
 225                                 events->alloc_size >> 1U);
 226         } else {
 227                 /* Indicate that we don't want to resize. */
 228                 new_size = 0;
 229         }
 230
 231         if (new_size) {
 232                 ret = resize_poll_event(events, new_size);
 233                 if (ret < 0) {
 234                         /* ENOMEM problem at this point. */
 235                         goto error;
 236                 }
 237         }
 238
 239         do {
 240                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 241         } while (ret == -1 && errno == EINTR);
 242         if (ret < 0) {
 243                 /* At this point, every error is fatal */
 244                 PERROR("epoll_wait");
 245                 goto error;
 246         }
 247
 248         /*
 249          * Since the returned events are set sequentially in the "events" structure
 250          * we only need to return the epoll_wait value and iterate over it.
 251          */
 252         return ret;
 253
 254 error:
 255         return -1;
 256 }
 257
 258 /*
 259  * Setup poll set maximum size.
 260  */
 261 void compat_epoll_set_max_size(void)
 262 {
 263         int ret, fd;
 264         ssize_t size_ret;
 265         char buf[64];
 266
 267         poll_max_size = DEFAULT_POLL_SIZE;
 268
 269         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 270         if (fd < 0) {
 271                 return;
 272         }
 273
 274         size_ret = lttng_read(fd, buf, sizeof(buf));
 275         /*
 276          * Allow reading a file smaller than buf, but keep space for
 277          * final \0.
 278          */
 279         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 280                 PERROR("read set max size");
 281                 goto error;
 282         }
 283         buf[size_ret] = '\0';
 284
 285         poll_max_size = atoi(buf);
 286         if (poll_max_size == 0) {
 287                 /* Extra precaution */
 288                 poll_max_size = DEFAULT_POLL_SIZE;
 289         }
 290
 291         DBG("epoll set max size is %d", poll_max_size);
 292
 293 error:
 294         ret = close(fd);
 295         if (ret) {
 296                 PERROR("close");
 297         }
 298 }