lib/lockfile.c

   1 /*
   2  * Copyright (c) 2019 Stefan Sperling <stsp@openbsd.org>
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16
  17 #include "got_compat.h"
  18
  19 #include <sys/stat.h>
  20 #include <sys/queue.h>
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <stdlib.h>
  25 #include <unistd.h>
  26 #include <string.h>
  27 #include <stdio.h>
  28 #include <time.h>
  29
  30 #include "got_error.h"
  31 #include "got_path.h"
  32
  33 #include "got_lib_lockfile.h"
  34
  35 const struct got_error *
  36 got_lockfile_lock(struct got_lockfile **lf, const char *path, int dir_fd)
  37 {
  38         const struct got_error *err = NULL;
  39         int attempts = 5;
  40
  41         *lf = calloc(1, sizeof(**lf));
  42         if (*lf == NULL)
  43                 return got_error_from_errno("calloc");
  44         (*lf)->fd = -1;
  45
  46         (*lf)->locked_path = strdup(path);
  47         if ((*lf)->locked_path == NULL) {
  48                 err = got_error_from_errno("strdup");
  49                 goto done;
  50         }
  51
  52         if (asprintf(&(*lf)->path, "%s%s", path, GOT_LOCKFILE_SUFFIX) == -1) {
  53                 err = got_error_from_errno("asprintf");
  54                 goto done;
  55         }
  56
  57         do {
  58                 if (dir_fd != -1) {
  59                         (*lf)->fd = openat(dir_fd, (*lf)->path,
  60                             O_RDWR | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
  61                             GOT_DEFAULT_FILE_MODE);
  62                 } else {
  63                         (*lf)->fd = open((*lf)->path,
  64                             O_RDWR | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
  65                             GOT_DEFAULT_FILE_MODE);
  66                 }
  67                 if ((*lf)->fd != -1)
  68                         break;
  69                 if (errno != EEXIST) {
  70                         err = got_error_from_errno2("open", (*lf)->path);
  71                         goto done;
  72                 }
  73                 sleep(1);
  74         } while (--attempts > 0);
  75
  76         if ((*lf)->fd == -1)
  77                 err = got_error(GOT_ERR_LOCKFILE_TIMEOUT);
  78 done:
  79         if (err) {
  80                 got_lockfile_unlock(*lf, dir_fd);
  81                 *lf = NULL;
  82         }
  83         return err;
  84 }
  85
  86 const struct got_error *
  87 got_lockfile_unlock(struct got_lockfile *lf, int dir_fd)
  88 {
  89         const struct got_error *err = NULL;
  90
  91         if (dir_fd != -1) {
  92                 if (lf->path && lf->fd != -1 &&
  93                     unlinkat(dir_fd, lf->path, 0) != 0)
  94                         err = got_error_from_errno("unlinkat");
  95         } else if (lf->path && lf->fd != -1 && unlink(lf->path) != 0)
  96                 err = got_error_from_errno("unlink");
  97         if (lf->fd != -1 && close(lf->fd) == -1 && err == NULL)
  98                 err = got_error_from_errno("close");
  99         free(lf->path);
 100         free(lf->locked_path);
 101         free(lf);
 102         return err;
 103 }