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418e61a824
Implement locking for W32.
625 lines
16 KiB
C
625 lines
16 KiB
C
/* dotlock.c - dotfile locking
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* Copyright (C) 1998, 1999, 2000, 2001, 2004,
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* 2005, 2009 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <ctype.h>
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#include <errno.h>
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#include <unistd.h>
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#ifdef HAVE_DOSISH_SYSTEM
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# define WIN32_LEAN_AND_MEAN
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# include <windows.h>
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#else
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# include <sys/utsname.h>
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#endif
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#include <sys/types.h>
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#ifndef _WIN32
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#include <sys/time.h>
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#endif
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <signal.h>
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#include "types.h"
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#include "util.h"
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#include "memory.h"
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#include "i18n.h"
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/* The object describing a lock. */
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struct dotlock_handle {
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struct dotlock_handle *next;
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char *tname; /* name of lockfile template */
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char *lockname; /* name of the real lockfile */
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int locked; /* lock status */
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int disable; /* locking */
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#ifdef HAVE_DOSISH_SYSTEM
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HANDLE lockhd; /* The W32 handle of the lock file. */
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#else
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size_t nodename_off; /* Offset in TNAME to the nodename part. */
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size_t nodename_len; /* Length of the nodename part. */
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#endif
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};
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/* A list of of all lock handles. */
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static volatile DOTLOCK all_lockfiles;
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/* If this has the value true all locking is disabled. */
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static int never_lock;
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#ifdef _REENTRANT
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/* fixme: acquire mutex on all_lockfiles */
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# define lock_all_lockfiles(h) do { } while (0)
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# define unlock_all_lockfiles(h) do { } while (0)
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#else
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# define lock_all_lockfiles(h) do { } while (0)
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# define unlock_all_lockfiles(h) do { } while (0)
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#endif
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void
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disable_dotlock(void)
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{
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never_lock = 1;
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}
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/****************
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* Create a lockfile with the given name and return an object of
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* type DOTLOCK which may be used later to actually do the lock.
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* A cleanup routine gets installed to cleanup left over locks
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* or other files used together with the lockmechanism.
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* Althoug the function is called dotlock, this does not necessarily
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* mean that real lockfiles are used - the function may decide to
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* use fcntl locking. Calling the function with NULL only install
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* the atexit handler and maybe used to assure that the cleanup
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* is called after all other atexit handlers.
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*
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* Notes: This function creates a lock file in the same directory
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* as file_to_lock with the name "file_to_lock.lock"
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* A temporary file ".#lk.<hostname>.pid[.threadid] is used.
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* This function does nothing for Windoze.
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*/
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DOTLOCK
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create_dotlock( const char *file_to_lock )
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{
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static int initialized;
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DOTLOCK h;
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#ifndef HAVE_DOSISH_SYSTEM
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int fd = -1;
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char pidstr[16];
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struct utsname utsbuf;
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const char *nodename;
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const char *dirpart;
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int dirpartlen;
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size_t tnamelen;
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int n;
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#endif /*!HAVE_DOSISH_SYSTEM*/
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if( !initialized ) {
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atexit( remove_lockfiles );
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initialized = 1;
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}
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if( !file_to_lock )
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return NULL;
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h = xmalloc_clear( sizeof *h );
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if( never_lock ) {
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h->disable = 1;
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lock_all_lockfiles (h);
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h->next = all_lockfiles;
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all_lockfiles = h;
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return h;
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}
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#ifndef HAVE_DOSISH_SYSTEM
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snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid() );
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/* create a temporary file */
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if( uname( &utsbuf ) )
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nodename = "unknown";
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else
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nodename = utsbuf.nodename;
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# ifdef __riscos__
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{
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char *iter = (char *) nodename;
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for (; iter[0]; iter++)
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if (iter[0] == '.')
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iter[0] = '/';
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}
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# endif /* __riscos__ */
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if( !(dirpart = strrchr( file_to_lock, DIRSEP_C )) ) {
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dirpart = EXTSEP_S;
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dirpartlen = 1;
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}
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else {
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dirpartlen = dirpart - file_to_lock;
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dirpart = file_to_lock;
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}
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lock_all_lockfiles (h);
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h->next = all_lockfiles;
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all_lockfiles = h;
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tnamelen = dirpartlen + 6+30+ strlen(nodename) + 10;
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h->tname = xmalloc (tnamelen + 1);
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h->nodename_len = strlen (nodename);
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# ifndef __riscos__
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snprintf (h->tname, tnamelen, "%.*s/.#lk%p.%n%s.%d",
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dirpartlen, dirpart, (void *)h, &n, nodename, (int)getpid ());
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# else /* __riscos__ */
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snprintf (h->tname, tnamelen, "%.*s.lk%p/%n%s/%d",
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dirpartlen, dirpart, (void *)h, &n, nodename, (int)getpid ());
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# endif /* __riscos__ */
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h->nodename_off = n;
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do {
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errno = 0;
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fd = open (h->tname, O_WRONLY|O_CREAT|O_EXCL,
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S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR);
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} while( fd == -1 && errno == EINTR );
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if( fd == -1 ) {
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all_lockfiles = h->next;
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log_error( "failed to create temporary file `%s': %s\n",
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h->tname, strerror(errno));
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xfree(h->tname);
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xfree(h);
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return NULL;
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}
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if (write (fd, pidstr, 11) != 11)
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goto write_failed;
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if (write (fd, nodename, strlen (nodename)) != strlen (nodename))
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goto write_failed;
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if (write (fd, "\n", 1 ) != 1)
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goto write_failed;
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if (close (fd))
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goto write_failed;
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unlock_all_lockfiles (h);
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h->lockname = xmalloc( strlen(file_to_lock) + 6 );
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strcpy(stpcpy(h->lockname, file_to_lock), EXTSEP_S "lock");
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return h;
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write_failed:
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all_lockfiles = h->next;
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unlock_all_lockfiles (h);
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log_error ("error writing to `%s': %s\n", h->tname, strerror(errno));
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close (fd);
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unlink (h->tname);
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xfree (h->tname);
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xfree (h);
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return NULL;
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#else /* HAVE_DOSISH_SYSTEM */
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/* The Windows version does not need a temporary file but uses the
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plain lock file along with record locking. We create this file
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here so that we later do only need to do the file locking. For
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error reporting it is useful to keep the name of the file in the
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handle. */
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h->next = all_lockfiles;
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all_lockfiles = h;
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h->lockname = xmalloc ( strlen (file_to_lock) + 6 );
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strcpy (stpcpy(h->lockname, file_to_lock), EXTSEP_S "lock");
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/* If would be nice if we would use the FILE_FLAG_DELETE_ON_CLOSE
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along with FILE_SHARE_DELETE but that does not work due to a race
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condition: Despite the OPEN_ALWAYS flag CreateFile may return an
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error and we can't reliable create/open the lock file unless we
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would wait here until it works - however there are other valid
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reasons why a lock file can't be created and thus the process
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would not stop as expected but spin until Windows crashes. Our
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solution is to keep the lock file open; that does not harm. */
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h->lockhd = CreateFile (h->lockname,
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GENERIC_READ|GENERIC_WRITE,
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FILE_SHARE_READ|FILE_SHARE_WRITE,
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NULL, OPEN_ALWAYS, 0, NULL);
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if (h->lockhd == INVALID_HANDLE_VALUE)
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{
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log_error (_("can't create `%s': %s\n"), h->lockname, w32_strerror (-1));
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all_lockfiles = h->next;
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xfree (h->lockname);
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xfree (h);
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return NULL;
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}
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return h;
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#endif /* HAVE_DOSISH_SYSTEM */
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}
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void
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destroy_dotlock ( DOTLOCK h )
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{
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DOTLOCK hprev, htmp;
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if (!h)
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return;
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/* First remove the handle from our global list of all locks. */
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for (hprev=NULL, htmp=all_lockfiles; htmp; hprev=htmp, htmp=htmp->next)
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if (htmp == h)
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{
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if (hprev)
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hprev->next = htmp->next;
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else
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all_lockfiles = htmp->next;
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h->next = NULL;
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break;
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}
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/* Second destroy the lock. */
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if (!h->disable)
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{
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#ifdef HAVE_DOSISH_SYSTEM
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if (h->locked)
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UnlockFile (h->lockhd, 0, 0, 1, 0);
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CloseHandle (h->lockhd);
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#else
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if (h->locked && h->lockname)
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unlink (h->lockname);
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if (h->tname)
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unlink (h->tname);
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xfree (h->tname);
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#endif
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xfree (h->lockname);
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}
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xfree(h);
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}
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#ifndef HAVE_DOSISH_SYSTEM
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static int
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maybe_deadlock( DOTLOCK h )
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{
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DOTLOCK r;
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for( r=all_lockfiles; r; r = r->next ) {
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if( r != h && r->locked )
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return 1;
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}
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return 0;
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}
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#endif /* !HAVE_DOSISH_SYSTEM */
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/* Read the lock file and return the pid, returns -1 on error. True
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will be stored in the integer at address SAME_NODE if the lock file
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has been created on the same node. */
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#ifndef HAVE_DOSISH_SYSTEM
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static int
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read_lockfile (DOTLOCK h, int *same_node )
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{
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char buffer_space[10+1+70+1]; /* 70 is just an estimated value; node
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names are usually shorter. */
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int fd;
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int pid = -1;
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char *buffer, *p;
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size_t expected_len;
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int res, nread;
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*same_node = 0;
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expected_len = 10 + 1 + h->nodename_len + 1;
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if ( expected_len >= sizeof buffer_space)
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buffer = xmalloc (expected_len);
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else
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buffer = buffer_space;
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if ( (fd = open (h->lockname, O_RDONLY)) == -1 )
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{
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int e = errno;
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log_info ("error opening lockfile `%s': %s\n",
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h->lockname, strerror(errno) );
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if (buffer != buffer_space)
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xfree (buffer);
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errno = e; /* Need to return ERRNO here. */
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return -1;
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}
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p = buffer;
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nread = 0;
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do
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{
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res = read (fd, p, expected_len - nread);
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if (res == -1 && errno == EINTR)
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continue;
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if (res < 0)
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{
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log_info ("error reading lockfile `%s'", h->lockname );
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close (fd);
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if (buffer != buffer_space)
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xfree (buffer);
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errno = 0; /* Do not return an inappropriate ERRNO. */
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return -1;
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}
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p += res;
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nread += res;
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}
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while (res && nread != expected_len);
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close (fd);
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if (nread < 11)
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{
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log_info ("invalid size of lockfile `%s'", h->lockname );
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if (buffer != buffer_space)
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xfree (buffer);
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errno = 0; /* Better don't return an inappropriate ERRNO. */
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return -1;
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}
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if (buffer[10] != '\n'
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|| (buffer[10] = 0, pid = atoi (buffer)) == -1
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#ifndef __riscos__
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|| !pid
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#else /* __riscos__ */
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|| (!pid && riscos_getpid())
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#endif /* __riscos__ */
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)
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{
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log_error ("invalid pid %d in lockfile `%s'", pid, h->lockname );
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if (buffer != buffer_space)
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xfree (buffer);
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errno = 0;
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return -1;
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}
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if (nread == expected_len
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&& !memcmp (h->tname+h->nodename_off, buffer+11, h->nodename_len)
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&& buffer[11+h->nodename_len] == '\n')
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*same_node = 1;
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if (buffer != buffer_space)
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xfree (buffer);
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return pid;
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}
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#endif /* !HAVE_DOSISH_SYSTEM */
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/****************
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* Do a lock on H. A TIMEOUT of 0 returns immediately,
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* -1 waits forever (hopefully not), other
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* values are timeouts in milliseconds.
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* Returns: 0 on success
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*/
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int
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make_dotlock( DOTLOCK h, long timeout )
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{
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int backoff=0;
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#ifndef HAVE_DOSISH_SYSTEM
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int pid;
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const char *maybe_dead="";
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int same_node;
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#endif
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if (h->disable)
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return 0;
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if (h->locked)
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{
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#ifndef __riscos__
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log_debug ("oops, `%s' is already locked\n", h->lockname);
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#endif /* !__riscos__ */
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return 0;
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}
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for (;;)
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{
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#ifndef HAVE_DOSISH_SYSTEM
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# ifndef __riscos__
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if( !link(h->tname, h->lockname) )
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{
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/* fixme: better use stat to check the link count */
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h->locked = 1;
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return 0; /* okay */
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}
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if (errno != EEXIST)
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{
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log_error ("lock not made: link() failed: %s\n", strerror(errno));
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return -1;
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}
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# else /* __riscos__ */
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if ( !riscos_renamefile(h->tname, h->lockname) )
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{
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h->locked = 1;
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return 0; /* okay */
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}
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if (errno != EEXIST)
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{
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log_error ("lock not made: rename() failed: %s\n", strerror(errno));
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return -1;
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}
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# endif /* __riscos__ */
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if ((pid = read_lockfile (h, &same_node)) == -1 )
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{
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if (errno != ENOENT)
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{
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log_info ("cannot read lockfile\n");
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return -1;
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}
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log_info ("lockfile disappeared\n");
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continue;
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}
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else if (pid == getpid ())
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{
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log_info ("Oops: lock already held by us\n");
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h->locked = 1;
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return 0; /* okay */
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}
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else if (same_node && kill(pid, 0) && errno == ESRCH)
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{
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# ifndef __riscos__
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log_info (_("removing stale lockfile (created by %d)\n"), pid );
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unlink (h->lockname);
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continue;
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# else /* __riscos__ */
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/* We are *pretty* sure that the other task is dead and
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therefore we remove the other lock file. */
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maybe_dead = " - probably dead - removing lock";
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unlink (h->lockname);
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# endif /* __riscos__ */
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}
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if (timeout == -1)
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{
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struct timeval tv;
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log_info ("waiting for lock (held by %d%s) %s...\n",
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pid, maybe_dead, maybe_deadlock(h)? "(deadlock?) ":"");
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/* We can't use sleep, because signals may be blocked. */
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tv.tv_sec = 1 + backoff;
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tv.tv_usec = 0;
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select (0, NULL, NULL, NULL, &tv);
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if (backoff < 10)
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backoff++ ;
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}
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else
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return -1;
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#else /*HAVE_DOSISH_SYSTEM*/
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int w32err;
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if (LockFile (h->lockhd, 0, 0, 1, 0))
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{
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h->locked = 1;
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return 0; /* okay */
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}
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w32err = GetLastError ();
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if (w32err != ERROR_LOCK_VIOLATION)
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{
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log_error (_("lock `%s' not made: %s\n"),
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h->lockname, w32_strerror (w32err));
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return -1;
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}
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if (timeout == -1)
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{
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/* Wait until lock has been released. */
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log_info (_("waiting for lock %s...\n"), h->lockname);
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Sleep ((1 + backoff)*1000);
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if ( backoff < 10 )
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backoff++ ;
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}
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else
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return -1;
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#endif /*HAVE_DOSISH_SYSTEM*/
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}
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/*NOTREACHED */
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}
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|
|
/****************
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|
* release a lock
|
|
* Returns: 0 := success
|
|
*/
|
|
int
|
|
release_dotlock (DOTLOCK h)
|
|
{
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|
#ifndef HAVE_DOSISH_SYSTEM
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|
int pid, same_node;
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|
#endif
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|
|
|
/* To avoid atexit race conditions we first check whether there are
|
|
any locks left. It might happen that another atexit handler
|
|
tries to release the lock while the atexit handler of this module
|
|
already ran and thus H is undefined. */
|
|
if (!all_lockfiles)
|
|
return 0;
|
|
|
|
if (h->disable)
|
|
return 0;
|
|
|
|
if (!h->locked)
|
|
{
|
|
log_debug("oops, `%s' is not locked\n", h->lockname );
|
|
return 0;
|
|
}
|
|
|
|
#ifndef HAVE_DOSISH_SYSTEM
|
|
pid = read_lockfile (h, &same_node);
|
|
if (pid == -1)
|
|
{
|
|
log_error ("release_dotlock: lockfile error\n");
|
|
return -1;
|
|
}
|
|
if (pid != getpid () || !same_node)
|
|
{
|
|
log_error ("release_dotlock: not our lock (pid=%d)\n", pid);
|
|
return -1;
|
|
}
|
|
# ifndef __riscos__
|
|
if (unlink (h->lockname))
|
|
{
|
|
log_error ("release_dotlock: error removing lockfile `%s'",
|
|
h->lockname);
|
|
return -1;
|
|
}
|
|
# else /* __riscos__ */
|
|
if( riscos_renamefile(h->lockname, h->tname) )
|
|
{
|
|
log_error( "release_dotlock: error renaming lockfile `%s' to `%s'",
|
|
h->lockname, h->tname);
|
|
return -1;
|
|
}
|
|
# endif /* __riscos__ */
|
|
|
|
#else /*HAVE_DOSISH_SYSTEM*/
|
|
|
|
if (!UnlockFile (h->lockhd, 0, 0, 1, 0))
|
|
{
|
|
log_error ("release_dotlock: error removing lockfile `%s': %s\n",
|
|
h->lockname, w32_strerror (-1));
|
|
return -1;
|
|
}
|
|
#endif /*HAVE_DOSISH_SYSTEM*/
|
|
|
|
h->locked = 0;
|
|
return 0;
|
|
}
|
|
|
|
|
|
void
|
|
remove_lockfiles()
|
|
{
|
|
#if !defined (HAVE_DOSISH_SYSTEM)
|
|
DOTLOCK h, h2;
|
|
|
|
h = all_lockfiles;
|
|
all_lockfiles = NULL;
|
|
|
|
while( h ) {
|
|
h2 = h->next;
|
|
destroy_dotlock (h);
|
|
h = h2;
|
|
}
|
|
#endif
|
|
}
|