pym/portage/locks.py

   1 # portage: Lock management code
   2 # Copyright 2004 Gentoo Foundation
   3 # Distributed under the terms of the GNU General Public License v2
   4 # $Id$
   5
   6 __all__ = ["lockdir", "unlockdir", "lockfile", "unlockfile", \
   7         "hardlock_name", "hardlink_is_mine", "hardlink_lockfile", \
   8         "unhardlink_lockfile", "hardlock_cleanup"]
   9
  10 import errno, os, stat, time, types
  11 from portage.exception import DirectoryNotFound, FileNotFound, \
  12         InvalidData, TryAgain
  13 from portage.data import portage_gid
  14 from portage.output import EOutput
  15 from portage.util import writemsg
  16 from portage.localization import _
  17
  18 HARDLINK_FD = -2
  19
  20 # Used by emerge in order to disable the "waiting for lock" message
  21 # so that it doesn't interfere with the status display.
  22 _quiet = False
  23
  24 def lockdir(mydir):
  25         return lockfile(mydir,wantnewlockfile=1)
  26 def unlockdir(mylock):
  27         return unlockfile(mylock)
  28
  29 def lockfile(mypath, wantnewlockfile=0, unlinkfile=0,
  30         waiting_msg=None, flags=0):
  31         """Creates all dirs upto, the given dir. Creates a lockfile
  32         for the given directory as the file: directoryname+'.portage_lockfile'."""
  33         import fcntl
  34
  35         if not mypath:
  36                 raise InvalidData("Empty path given")
  37
  38         if type(mypath) == types.StringType and mypath[-1] == '/':
  39                 mypath = mypath[:-1]
  40
  41         if type(mypath) == types.FileType:
  42                 mypath = mypath.fileno()
  43         if type(mypath) == types.IntType:
  44                 lockfilename    = mypath
  45                 wantnewlockfile = 0
  46                 unlinkfile      = 0
  47         elif wantnewlockfile:
  48                 base, tail = os.path.split(mypath)
  49                 lockfilename = os.path.join(base, "." + tail + ".portage_lockfile")
  50                 del base, tail
  51                 unlinkfile   = 1
  52         else:
  53                 lockfilename = mypath
  54
  55         if type(mypath) == types.StringType:
  56                 if not os.path.exists(os.path.dirname(mypath)):
  57                         raise DirectoryNotFound(os.path.dirname(mypath))
  58                 if not os.path.exists(lockfilename):
  59                         old_mask=os.umask(000)
  60                         myfd = os.open(lockfilename, os.O_CREAT|os.O_RDWR,0660)
  61                         try:
  62                                 if os.stat(lockfilename).st_gid != portage_gid:
  63                                         os.chown(lockfilename,os.getuid(),portage_gid)
  64                         except OSError, e:
  65                                 if e[0] == 2: # No such file or directory
  66                                         return lockfile(mypath, wantnewlockfile=wantnewlockfile,
  67                                                 unlinkfile=unlinkfile, waiting_msg=waiting_msg,
  68                                                 flags=flags)
  69                                 else:
  70                                         writemsg("Cannot chown a lockfile. This could cause inconvenience later.\n");
  71                         os.umask(old_mask)
  72                 else:
  73                         myfd = os.open(lockfilename, os.O_CREAT|os.O_RDWR,0660)
  74
  75         elif type(mypath) == types.IntType:
  76                 myfd = mypath
  77
  78         else:
  79                 raise ValueError("Unknown type passed in '%s': '%s'" % \
  80                         (type(mypath), mypath))
  81
  82         # try for a non-blocking lock, if it's held, throw a message
  83         # we're waiting on lockfile and use a blocking attempt.
  84         locking_method = fcntl.lockf
  85         try:
  86                 fcntl.lockf(myfd,fcntl.LOCK_EX|fcntl.LOCK_NB)
  87         except IOError, e:
  88                 if "errno" not in dir(e):
  89                         raise
  90                 if e.errno in (errno.EACCES, errno.EAGAIN):
  91                         # resource temp unavailable; eg, someone beat us to the lock.
  92                         if flags & os.O_NONBLOCK:
  93                                 raise TryAgain(mypath)
  94
  95                         global _quiet
  96                         out = EOutput()
  97                         out.quiet = _quiet
  98                         if waiting_msg is None:
  99                                 if isinstance(mypath, int):
 100                                         waiting_msg = "waiting for lock on fd %i" % myfd
 101                                 else:
 102                                         waiting_msg = "waiting for lock on %s\n" % lockfilename
 103                         out.ebegin(waiting_msg)
 104                         # try for the exclusive lock now.
 105                         try:
 106                                 fcntl.lockf(myfd, fcntl.LOCK_EX)
 107                         except EnvironmentError, e:
 108                                 out.eend(1, str(e))
 109                                 raise
 110                         out.eend(os.EX_OK)
 111                 elif e.errno == errno.ENOLCK:
 112                         # We're not allowed to lock on this FS.
 113                         os.close(myfd)
 114                         link_success = False
 115                         if lockfilename == str(lockfilename):
 116                                 if wantnewlockfile:
 117                                         try:
 118                                                 if os.stat(lockfilename)[stat.ST_NLINK] == 1:
 119                                                         os.unlink(lockfilename)
 120                                         except OSError:
 121                                                 pass
 122                                         link_success = hardlink_lockfile(lockfilename)
 123                         if not link_success:
 124                                 raise
 125                         locking_method = None
 126                         myfd = HARDLINK_FD
 127                 else:
 128                         raise
 129
 130
 131         if type(lockfilename) == types.StringType and \
 132                 myfd != HARDLINK_FD and _fstat_nlink(myfd) == 0:
 133                 # The file was deleted on us... Keep trying to make one...
 134                 os.close(myfd)
 135                 writemsg("lockfile recurse\n",1)
 136                 lockfilename, myfd, unlinkfile, locking_method = lockfile(
 137                         mypath, wantnewlockfile=wantnewlockfile, unlinkfile=unlinkfile,
 138                         waiting_msg=waiting_msg, flags=flags)
 139
 140         writemsg(str((lockfilename,myfd,unlinkfile))+"\n",1)
 141         return (lockfilename,myfd,unlinkfile,locking_method)
 142
 143 def _fstat_nlink(fd):
 144         """
 145         @param fd: an open file descriptor
 146         @type fd: Integer
 147         @rtype: Integer
 148         @return: the current number of hardlinks to the file
 149         """
 150         try:
 151                 return os.fstat(fd).st_nlink
 152         except EnvironmentError, e:
 153                 if e.errno == errno.ENOENT:
 154                         # Some filesystems such as CIFS return
 155                         # ENOENT which means st_nlink == 0.
 156                         return 0
 157                 raise
 158
 159 def unlockfile(mytuple):
 160         import fcntl
 161
 162         #XXX: Compatability hack.
 163         if len(mytuple) == 3:
 164                 lockfilename,myfd,unlinkfile = mytuple
 165                 locking_method = fcntl.flock
 166         elif len(mytuple) == 4:
 167                 lockfilename,myfd,unlinkfile,locking_method = mytuple
 168         else:
 169                 raise InvalidData
 170
 171         if(myfd == HARDLINK_FD):
 172                 unhardlink_lockfile(lockfilename)
 173                 return True
 174
 175         # myfd may be None here due to myfd = mypath in lockfile()
 176         if type(lockfilename) == types.StringType and not os.path.exists(lockfilename):
 177                 writemsg("lockfile does not exist '%s'\n" % lockfilename,1)
 178                 if myfd is not None:
 179                         os.close(myfd)
 180                 return False
 181
 182         try:
 183                 if myfd is None:
 184                         myfd = os.open(lockfilename, os.O_WRONLY,0660)
 185                         unlinkfile = 1
 186                 locking_method(myfd,fcntl.LOCK_UN)
 187         except OSError:
 188                 if type(lockfilename) == types.StringType:
 189                         os.close(myfd)
 190                 raise IOError("Failed to unlock file '%s'\n" % lockfilename)
 191
 192         try:
 193                 # This sleep call was added to allow other processes that are
 194                 # waiting for a lock to be able to grab it before it is deleted.
 195                 # lockfile() already accounts for this situation, however, and
 196                 # the sleep here adds more time than is saved overall, so am
 197                 # commenting until it is proved necessary.
 198                 #time.sleep(0.0001)
 199                 if unlinkfile:
 200                         locking_method(myfd,fcntl.LOCK_EX|fcntl.LOCK_NB)
 201                         # We won the lock, so there isn't competition for it.
 202                         # We can safely delete the file.
 203                         writemsg("Got the lockfile...\n",1)
 204                         if _fstat_nlink(myfd) == 1:
 205                                 os.unlink(lockfilename)
 206                                 writemsg("Unlinked lockfile...\n",1)
 207                                 locking_method(myfd,fcntl.LOCK_UN)
 208                         else:
 209                                 writemsg("lockfile does not exist '%s'\n" % lockfilename,1)
 210                                 os.close(myfd)
 211                                 return False
 212         except Exception, e:
 213                 writemsg("Failed to get lock... someone took it.\n",1)
 214                 writemsg(str(e)+"\n",1)
 215
 216         # why test lockfilename?  because we may have been handed an
 217         # fd originally, and the caller might not like having their
 218         # open fd closed automatically on them.
 219         if type(lockfilename) == types.StringType:
 220                 os.close(myfd)
 221
 222         return True
 223
 224
 225
 226
 227 def hardlock_name(path):
 228         return path+".hardlock-"+os.uname()[1]+"-"+str(os.getpid())
 229
 230 def hardlink_is_mine(link,lock):
 231         try:
 232                 return os.stat(link).st_nlink == 2
 233         except OSError:
 234                 return False
 235
 236 def hardlink_lockfile(lockfilename, max_wait=14400):
 237         """Does the NFS, hardlink shuffle to ensure locking on the disk.
 238         We create a PRIVATE lockfile, that is just a placeholder on the disk.
 239         Then we HARDLINK the real lockfile to that private file.
 240         If our file can 2 references, then we have the lock. :)
 241         Otherwise we lather, rise, and repeat.
 242         We default to a 4 hour timeout.
 243         """
 244
 245         start_time = time.time()
 246         myhardlock = hardlock_name(lockfilename)
 247         reported_waiting = False
 248
 249         while(time.time() < (start_time + max_wait)):
 250                 # We only need it to exist.
 251                 myfd = os.open(myhardlock, os.O_CREAT|os.O_RDWR,0660)
 252                 os.close(myfd)
 253
 254                 if not os.path.exists(myhardlock):
 255                         raise FileNotFound(
 256                                 _("Created lockfile is missing: %(filename)s") % \
 257                                 {"filename" : myhardlock})
 258
 259                 try:
 260                         res = os.link(myhardlock, lockfilename)
 261                 except OSError:
 262                         pass
 263
 264                 if hardlink_is_mine(myhardlock, lockfilename):
 265                         # We have the lock.
 266                         if reported_waiting:
 267                                 writemsg("\n", noiselevel=-1)
 268                         return True
 269
 270                 if reported_waiting:
 271                         writemsg(".", noiselevel=-1)
 272                 else:
 273                         reported_waiting = True
 274                         from portage.const import PORTAGE_BIN_PATH
 275                         msg = "\nWaiting on (hardlink) lockfile:" + \
 276                                 " (one '.' per 3 seconds)\n" + \
 277                                 "%s/clean_locks can fix stuck locks.\n" % PORTAGE_BIN_PATH + \
 278                                 "Lockfile: %s\n" % lockfilename
 279                         writemsg(msg, noiselevel=-1)
 280                 time.sleep(3)
 281
 282         os.unlink(myhardlock)
 283         return False
 284
 285 def unhardlink_lockfile(lockfilename):
 286         myhardlock = hardlock_name(lockfilename)
 287         if hardlink_is_mine(myhardlock, lockfilename):
 288                 # Make sure not to touch lockfilename unless we really have a lock.
 289                 try:
 290                         os.unlink(lockfilename)
 291                 except OSError:
 292                         pass
 293         try:
 294                 os.unlink(myhardlock)
 295         except OSError:
 296                 pass
 297
 298 def hardlock_cleanup(path, remove_all_locks=False):
 299         mypid  = str(os.getpid())
 300         myhost = os.uname()[1]
 301         mydl = os.listdir(path)
 302
 303         results = []
 304         mycount = 0
 305
 306         mylist = {}
 307         for x in mydl:
 308                 if os.path.isfile(path+"/"+x):
 309                         parts = x.split(".hardlock-")
 310                         if len(parts) == 2:
 311                                 filename = parts[0]
 312                                 hostpid  = parts[1].split("-")
 313                                 host  = "-".join(hostpid[:-1])
 314                                 pid   = hostpid[-1]
 315
 316                                 if filename not in mylist:
 317                                         mylist[filename] = {}
 318                                 if host not in mylist[filename]:
 319                                         mylist[filename][host] = []
 320                                 mylist[filename][host].append(pid)
 321
 322                                 mycount += 1
 323
 324
 325         results.append("Found %(count)s locks" % {"count":mycount})
 326
 327         for x in mylist:
 328                 if myhost in mylist[x] or remove_all_locks:
 329                         mylockname = hardlock_name(path+"/"+x)
 330                         if hardlink_is_mine(mylockname, path+"/"+x) or \
 331                            not os.path.exists(path+"/"+x) or \
 332                                  remove_all_locks:
 333                                 for y in mylist[x]:
 334                                         for z in mylist[x][y]:
 335                                                 filename = path+"/"+x+".hardlock-"+y+"-"+z
 336                                                 if filename == mylockname:
 337                                                         continue
 338                                                 try:
 339                                                         # We're sweeping through, unlinking everyone's locks.
 340                                                         os.unlink(filename)
 341                                                         results.append(_("Unlinked: ") + filename)
 342                                                 except OSError:
 343                                                         pass
 344                                 try:
 345                                         os.unlink(path+"/"+x)
 346                                         results.append(_("Unlinked: ") + path+"/"+x)
 347                                         os.unlink(mylockname)
 348                                         results.append(_("Unlinked: ") + mylockname)
 349                                 except OSError:
 350                                         pass
 351                         else:
 352                                 try:
 353                                         os.unlink(mylockname)
 354                                         results.append(_("Unlinked: ") + mylockname)
 355                                 except OSError:
 356                                         pass
 357
 358         return results
 359