git.gag.com Git - debian/amanda/blob - config/amanda/flock.m4

   1 # SYNOPSIS
   2 #
   3 #   AMANDA_SETUP_FILE_LOCKING
   4 #
   5 # OVERVIEW
   6 #
   7 #   Set up file locking support.  Four locking mechanisms are available:
   8 #     POSIX_FCNTL - use fcntl().  The full job.
   9 #     FLOCK       - use flock().  Does just as well.
  10 #     LOCKF       - use lockf().  Only handles advisory, exclusive,
  11 #                       blocking file locks as used by Amanda.
  12 #     LNLOCK      - Home brew exclusive, blocking file lock.
  13 #
  14 #   For the chosen method, WANT_AMFLOCK_mech is defined and set up as an
  15 #   AM_CONDITIONAL.  Also, LOCKING, which contains the mechanism, is substituted.
  16 #
  17 AC_DEFUN([AMANDA_SETUP_FILE_LOCKING],
  18 [
  19     AC_CHECK_HEADERS(
  20         fcntl.h \
  21         sys/fcntl.h \
  22         sys/types.h \
  23         sys/file.h \
  24         unistd.h \
  25     )
  26
  27     # find a working file-locking mechanism.
  28     # Note: these all use AC_TRY_LINK to make sure that we can compile
  29     # and link each variant.  They do not try to test the variants --
  30     # that is left to runtime.
  31     LOCKING="no"
  32
  33     # check POSIX locking
  34     AC_CACHE_CHECK(
  35        [whether POSIX locking (with fcntl(2)) is available],
  36        amanda_cv_posix_filelocking,
  37        [
  38             AC_TRY_LINK([
  39 #if HAVE_SYS_TYPES_H
  40 # include <sys/types.h>
  41 #endif
  42 #if HAVE_UNISTD_H
  43 # include <unistd.h>
  44 #endif
  45 #if HAVE_FCNTL_H
  46 # include <fcntl.h>
  47 #endif
  48             ], [
  49             struct flock lock;
  50
  51             lock.l_type = F_RDLCK;
  52             lock.l_start = 0;
  53             lock.l_whence = SEEK_CUR;
  54             lock.l_len = 0;
  55             return fcntl(1, F_SETLK, &lock);
  56             ], [
  57         amanda_cv_posix_filelocking="yes"
  58             ],[
  59         amanda_cv_posix_filelocking="no"
  60             ])
  61         ])
  62     if test "x$amanda_cv_posix_filelocking" = xyes; then
  63         AC_DEFINE(WANT_AMFLOCK_POSIX,1,[Define to use POSIX (fcntl()) for file locking])
  64         WANT_AMFLOCK_POSIX="yes"
  65         LOCKING="POSIX_FCNTL"
  66     fi
  67     AM_CONDITIONAL(WANT_AMFLOCK_POSIX, test x"$WANT_AMFLOCK_POSIX" = x"yes")
  68
  69     # check flock-based (BSD) locking
  70     AC_CACHE_CHECK(
  71        [whether flock locking is available],
  72        amanda_cv_flock_filelocking,
  73        [
  74             AC_TRY_LINK([
  75 #if HAVE_SYS_FILE_H
  76 # include <sys/file.h>
  77 #endif
  78             ], [
  79             return flock(1, LOCK_SH);
  80             ], [
  81         amanda_cv_flock_filelocking="yes"
  82             ],[
  83         amanda_cv_flock_filelocking="no"
  84             ])
  85         ])
  86     if test "x$amanda_cv_flock_filelocking" = xyes; then
  87         AC_DEFINE(WANT_AMFLOCK_FLOCK,1,[Define to use flock(2) for file locking])
  88         WANT_AMFLOCK_FLOCK="yes"
  89         LOCKING="FLOCK"
  90     fi
  91     AM_CONDITIONAL(WANT_AMFLOCK_FLOCK, test x"$WANT_AMFLOCK_FLOCK" = x"yes")
  92
  93     # check lockf-based (SVR2, SVR3, SVR4) locking
  94     AC_CACHE_CHECK(
  95        [whether lockf(3) locking is available],
  96        amanda_cv_lockf_filelocking,
  97        [
  98             AC_TRY_LINK([
  99 #if HAVE_UNISTD_H
 100 # include <unistd.h>
 101 #endif
 102             ], [
 103             return lockf(1, F_LOCK, 0);
 104             ], [
 105         amanda_cv_lockf_filelocking="yes"
 106             ],[
 107         amanda_cv_lockf_filelocking="no"
 108             ])
 109         ])
 110     if test "x$amanda_cv_lockf_filelocking" = xyes; then
 111         AC_DEFINE(WANT_AMFLOCK_LOCKF,1,[Define to use lockf(3) for file locking.])
 112         WANT_AMFLOCK_LOCKF="yes"
 113         LOCKING="LOCKF"
 114     fi
 115     AM_CONDITIONAL(WANT_AMFLOCK_LOCKF, test x"$WANT_AMFLOCK_LOCKF" = x"yes")
 116
 117     # check our homebrew hardlink-based locking (requires hardlinks)
 118     AC_CACHE_CHECK(
 119        [whether link(2) is available for locking],
 120        amanda_cv_lnlock_filelocking,
 121        [
 122             AC_TRY_LINK([
 123 #if HAVE_UNISTD_H
 124 # include <unistd.h>
 125 #endif
 126             ], [
 127             return link("/tmp/foo", "/tmp/bar");
 128             ], [
 129         amanda_cv_lnlock_filelocking="yes"
 130             ],[
 131         amanda_cv_lnlock_filelocking="no"
 132             ])
 133         ])
 134     if test "x$amanda_cv_lnlock_filelocking" = xyes; then
 135         AC_DEFINE(WANT_AMFLOCK_LNLOCK,1,[Define to use link(2) to emulate file locking.])
 136         WANT_AMFLOCK_LNLOCK="yes"
 137         LOCKING="LNLOCK"
 138     fi
 139     AM_CONDITIONAL(WANT_AMFLOCK_LNLOCK, test x"$WANT_AMFLOCK_LNLOCK" = x"yes")
 140
 141     if test x"$LOCKING" = "no"; then
 142         # this shouldn't happen, and is *bad* if it does
 143         AC_MSG_ERROR([*** No working file locking capability found!])
 144     fi
 145
 146     AC_SUBST(LOCKING)
 147 ])