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 int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
  71 {
  72         int ret;
  73
  74         if (events == NULL || size <= 0) {
  75                 goto error;
  76         }
  77
  78         if (!poll_max_size) {
  79                 ERR("poll_max_size not initialized yet");
  80                 goto error;
  81         }
  82
  83         /* Don't bust the limit here */
  84         if (size > poll_max_size) {
  85                 size = poll_max_size;
  86         }
  87
  88         ret = compat_glibc_epoll_create(size, flags);
  89         if (ret < 0) {
  90                 /* At this point, every error is fatal */
  91                 PERROR("epoll_create1");
  92                 goto error;
  93         }
  94
  95         events->epfd = ret;
  96
  97         /* This *must* be freed by using lttng_poll_free() */
  98         events->events = zmalloc(size * sizeof(struct epoll_event));
  99         if (events->events == NULL) {
 100                 PERROR("zmalloc epoll set");
 101                 goto error_close;
 102         }
 103
 104         events->alloc_size = events->init_size = size;
 105         events->nb_fd = 0;
 106
 107         return 0;
 108
 109 error_close:
 110         ret = close(events->epfd);
 111         if (ret) {
 112                 PERROR("close");
 113         }
 114 error:
 115         return -1;
 116 }
 117
 118 /*
 119  * Add a fd to the epoll set with requesting events.
 120  */
 121 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 122 {
 123         int ret;
 124         struct epoll_event ev;
 125
 126         if (events == NULL || events->events == NULL || fd < 0) {
 127                 ERR("Bad compat epoll add arguments");
 128                 goto error;
 129         }
 130
 131         /*
 132          * Zero struct epoll_event to ensure all representations of its
 133          * union are zeroed.
 134          */
 135         memset(&ev, 0, sizeof(ev));
 136         ev.events = req_events;
 137         ev.data.fd = fd;
 138
 139         ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
 140         if (ret < 0) {
 141                 switch (errno) {
 142                 case EEXIST:
 143                         /* If exist, it's OK. */
 144                         goto end;
 145                 case ENOSPC:
 146                 case EPERM:
 147                         /* Print PERROR and goto end not failing. Show must go on. */
 148                         PERROR("epoll_ctl ADD");
 149                         goto end;
 150                 default:
 151                         PERROR("epoll_ctl ADD fatal");
 152                         goto error;
 153                 }
 154         }
 155
 156         events->nb_fd++;
 157
 158 end:
 159         return 0;
 160
 161 error:
 162         return -1;
 163 }
 164
 165 /*
 166  * Remove a fd from the epoll set.
 167  */
 168 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 169 {
 170         int ret;
 171
 172         if (events == NULL || fd < 0 || events->nb_fd == 0) {
 173                 goto error;
 174         }
 175
 176         ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
 177         if (ret < 0) {
 178                 switch (errno) {
 179                 case ENOENT:
 180                 case EPERM:
 181                         /* Print PERROR and goto end not failing. Show must go on. */
 182                         PERROR("epoll_ctl DEL");
 183                         goto end;
 184                 default:
 185                         PERROR("epoll_ctl DEL fatal");
 186                         goto error;
 187                 }
 188         }
 189
 190         events->nb_fd--;
 191
 192 end:
 193         return 0;
 194
 195 error:
 196         return -1;
 197 }
 198
 199 /*
 200  * Wait on epoll set. This is a blocking call of timeout value.
 201  */
 202 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 203 {
 204         int ret;
 205         uint32_t new_size;
 206
 207         if (events == NULL || events->events == NULL) {
 208                 ERR("Wrong arguments in compat_epoll_wait");
 209                 goto error;
 210         }
 211         assert(events->nb_fd >= 0);
 212
 213         if (events->nb_fd == 0) {
 214                 errno = EINVAL;
 215                 return -1;
 216         }
 217
 218         /*
 219          * Resize if needed before waiting. We could either expand the array or
 220          * shrink it down. It's important to note that after this step, we are
 221          * ensured that the events argument of the epoll_wait call will be large
 222          * enough to hold every possible returned events.
 223          */
 224         new_size = 1U << utils_get_count_order_u32(events->nb_fd);
 225         if (new_size != events->alloc_size && new_size >= events->init_size) {
 226                 ret = resize_poll_event(events, new_size);
 227                 if (ret < 0) {
 228                         /* ENOMEM problem at this point. */
 229                         goto error;
 230                 }
 231         }
 232
 233         do {
 234                 ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 235         } while (ret == -1 && errno == EINTR);
 236         if (ret < 0) {
 237                 /* At this point, every error is fatal */
 238                 PERROR("epoll_wait");
 239                 goto error;
 240         }
 241
 242         /*
 243          * Since the returned events are set sequentially in the "events" structure
 244          * we only need to return the epoll_wait value and iterate over it.
 245          */
 246         return ret;
 247
 248 error:
 249         return -1;
 250 }
 251
 252 /*
 253  * Setup poll set maximum size.
 254  */
 255 int compat_epoll_set_max_size(void)
 256 {
 257         int ret, fd, retval = 0;
 258         ssize_t size_ret;
 259         char buf[64];
 260
 261         fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 262         if (fd < 0) {
 263                 retval = -1;
 264                 goto end;
 265         }
 266
 267         size_ret = lttng_read(fd, buf, sizeof(buf));
 268         /*
 269          * Allow reading a file smaller than buf, but keep space for
 270          * final \0.
 271          */
 272         if (size_ret < 0 || size_ret >= sizeof(buf)) {
 273                 PERROR("read set max size");
 274                 retval = -1;
 275                 goto end_read;
 276         }
 277         buf[size_ret] = '\0';
 278         poll_max_size = atoi(buf);
 279 end_read:
 280         ret = close(fd);
 281         if (ret) {
 282                 PERROR("close");
 283         }
 284 end:
 285         if (!poll_max_size) {
 286                 poll_max_size = DEFAULT_POLL_SIZE;
 287         }
 288         DBG("epoll set max size is %d", poll_max_size);
 289         return retval;
 290 }