src/libudev/libudev-queue.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2008-2012 Kay Sievers <kay@vrfy.org>
   6   Copyright 2009 Alan Jenkins <alan-jenkins@tuffmail.co.uk>
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <errno.h>
  23 #include <stddef.h>
  24 #include <stdlib.h>
  25 #include <sys/inotify.h>
  26 #include <unistd.h>
  27
  28 #include "alloc-util.h"
  29 #include "fd-util.h"
  30 #include "io-util.h"
  31 #include "libudev-private.h"
  32
  33 /**
  34  * SECTION:libudev-queue
  35  * @short_description: access to currently active events
  36  *
  37  * This exports the current state of the udev processing queue.
  38  */
  39
  40 /**
  41  * udev_queue:
  42  *
  43  * Opaque object representing the current event queue in the udev daemon.
  44  */
  45 struct udev_queue {
  46         struct udev *udev;
  47         int refcount;
  48         int fd;
  49 };
  50
  51 /**
  52  * udev_queue_new:
  53  * @udev: udev library context
  54  *
  55  * The initial refcount is 1, and needs to be decremented to
  56  * release the resources of the udev queue context.
  57  *
  58  * Returns: the udev queue context, or #NULL on error.
  59  **/
  60 _public_ struct udev_queue *udev_queue_new(struct udev *udev)
  61 {
  62         struct udev_queue *udev_queue;
  63
  64         if (udev == NULL) {
  65                 errno = EINVAL;
  66                 return NULL;
  67         }
  68
  69         udev_queue = new0(struct udev_queue, 1);
  70         if (udev_queue == NULL) {
  71                 errno = ENOMEM;
  72                 return NULL;
  73         }
  74
  75         udev_queue->refcount = 1;
  76         udev_queue->udev = udev;
  77         udev_queue->fd = -1;
  78         return udev_queue;
  79 }
  80
  81 /**
  82  * udev_queue_ref:
  83  * @udev_queue: udev queue context
  84  *
  85  * Take a reference of a udev queue context.
  86  *
  87  * Returns: the same udev queue context.
  88  **/
  89 _public_ struct udev_queue *udev_queue_ref(struct udev_queue *udev_queue)
  90 {
  91         if (udev_queue == NULL)
  92                 return NULL;
  93
  94         udev_queue->refcount++;
  95         return udev_queue;
  96 }
  97
  98 /**
  99  * udev_queue_unref:
 100  * @udev_queue: udev queue context
 101  *
 102  * Drop a reference of a udev queue context. If the refcount reaches zero,
 103  * the resources of the queue context will be released.
 104  *
 105  * Returns: #NULL
 106  **/
 107 _public_ struct udev_queue *udev_queue_unref(struct udev_queue *udev_queue)
 108 {
 109         if (udev_queue == NULL)
 110                 return NULL;
 111
 112         udev_queue->refcount--;
 113         if (udev_queue->refcount > 0)
 114                 return NULL;
 115
 116         safe_close(udev_queue->fd);
 117
 118         return mfree(udev_queue);
 119 }
 120
 121 /**
 122  * udev_queue_get_udev:
 123  * @udev_queue: udev queue context
 124  *
 125  * Retrieve the udev library context the queue context was created with.
 126  *
 127  * Returns: the udev library context.
 128  **/
 129 _public_ struct udev *udev_queue_get_udev(struct udev_queue *udev_queue)
 130 {
 131         if (udev_queue == NULL) {
 132                 errno = EINVAL;
 133                 return NULL;
 134         }
 135         return udev_queue->udev;
 136 }
 137
 138 /**
 139  * udev_queue_get_kernel_seqnum:
 140  * @udev_queue: udev queue context
 141  *
 142  * This function is deprecated.
 143  *
 144  * Returns: 0.
 145  **/
 146 _public_ unsigned long long int udev_queue_get_kernel_seqnum(struct udev_queue *udev_queue)
 147 {
 148         return 0;
 149 }
 150
 151 /**
 152  * udev_queue_get_udev_seqnum:
 153  * @udev_queue: udev queue context
 154  *
 155  * This function is deprecated.
 156  *
 157  * Returns: 0.
 158  **/
 159 _public_ unsigned long long int udev_queue_get_udev_seqnum(struct udev_queue *udev_queue)
 160 {
 161         return 0;
 162 }
 163
 164 /**
 165  * udev_queue_get_udev_is_active:
 166  * @udev_queue: udev queue context
 167  *
 168  * Check if udev is active on the system.
 169  *
 170  * Returns: a flag indicating if udev is active.
 171  **/
 172 _public_ int udev_queue_get_udev_is_active(struct udev_queue *udev_queue)
 173 {
 174         return access("/run/udev/control", F_OK) >= 0;
 175 }
 176
 177 /**
 178  * udev_queue_get_queue_is_empty:
 179  * @udev_queue: udev queue context
 180  *
 181  * Check if udev is currently processing any events.
 182  *
 183  * Returns: a flag indicating if udev is currently handling events.
 184  **/
 185 _public_ int udev_queue_get_queue_is_empty(struct udev_queue *udev_queue)
 186 {
 187         return access("/run/udev/queue", F_OK) < 0;
 188 }
 189
 190 /**
 191  * udev_queue_get_seqnum_sequence_is_finished:
 192  * @udev_queue: udev queue context
 193  * @start: first event sequence number
 194  * @end: last event sequence number
 195  *
 196  * This function is deprecated, it just returns the result of
 197  * udev_queue_get_queue_is_empty().
 198  *
 199  * Returns: a flag indicating if udev is currently handling events.
 200  **/
 201 _public_ int udev_queue_get_seqnum_sequence_is_finished(struct udev_queue *udev_queue,
 202                                                unsigned long long int start, unsigned long long int end)
 203 {
 204         return udev_queue_get_queue_is_empty(udev_queue);
 205 }
 206
 207 /**
 208  * udev_queue_get_seqnum_is_finished:
 209  * @udev_queue: udev queue context
 210  * @seqnum: sequence number
 211  *
 212  * This function is deprecated, it just returns the result of
 213  * udev_queue_get_queue_is_empty().
 214  *
 215  * Returns: a flag indicating if udev is currently handling events.
 216  **/
 217 _public_ int udev_queue_get_seqnum_is_finished(struct udev_queue *udev_queue, unsigned long long int seqnum)
 218 {
 219         return udev_queue_get_queue_is_empty(udev_queue);
 220 }
 221
 222 /**
 223  * udev_queue_get_queued_list_entry:
 224  * @udev_queue: udev queue context
 225  *
 226  * This function is deprecated.
 227  *
 228  * Returns: NULL.
 229  **/
 230 _public_ struct udev_list_entry *udev_queue_get_queued_list_entry(struct udev_queue *udev_queue)
 231 {
 232         errno = ENODATA;
 233         return NULL;
 234 }
 235
 236 /**
 237  * udev_queue_get_fd:
 238  * @udev_queue: udev queue context
 239  *
 240  * Returns: a file descriptor to watch for a queue to become empty.
 241  */
 242 _public_ int udev_queue_get_fd(struct udev_queue *udev_queue) {
 243         int fd;
 244         int r;
 245
 246         if (udev_queue->fd >= 0)
 247                 return udev_queue->fd;
 248
 249         fd = inotify_init1(IN_CLOEXEC);
 250         if (fd < 0)
 251                 return -errno;
 252
 253         r = inotify_add_watch(fd, "/run/udev" , IN_DELETE);
 254         if (r < 0) {
 255                 r = -errno;
 256                 close(fd);
 257                 return r;
 258         }
 259
 260         udev_queue->fd = fd;
 261         return fd;
 262 }
 263
 264 /**
 265  * udev_queue_flush:
 266  * @udev_queue: udev queue context
 267  *
 268  * Returns: the result of clearing the watch for queue changes.
 269  */
 270 _public_ int udev_queue_flush(struct udev_queue *udev_queue) {
 271         int r;
 272
 273         assert(udev_queue);
 274
 275         if (udev_queue->fd < 0)
 276                 return -EINVAL;
 277
 278         r = flush_fd(udev_queue->fd);
 279         if (r < 0)
 280                 return r;
 281
 282         return 0;
 283 }