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b008274afd
We better do this once and for all instead of cluttering all future commits with diffs of trailing white spaces. In the majority of cases blank or single lines are affected and thus this change won't disturb a git blame too much. For future commits the pre-commit scripts checks that this won't happen again.
725 lines
18 KiB
C
725 lines
18 KiB
C
/* dotlock.c - dotfile locking
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* Copyright (C) 1998, 2000, 2001, 2003, 2004,
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* 2005, 2006, 2008, 2010 Free Software Foundation, Inc.
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*
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* This file is part of JNLIB.
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*
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* JNLIB is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 3 of
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* the License, or (at your option) any later version.
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*
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* JNLIB is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License 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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#include <sys/time.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#ifdef HAVE_SIGNAL_H
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# include <signal.h>
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#endif
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#include "libjnlib-config.h"
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#include "stringhelp.h"
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#include "dotlock.h"
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#include "utf8conv.h"
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#if !defined(DIRSEP_C) && !defined(EXTSEP_C) \
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&& !defined(DIRSEP_S) && !defined(EXTSEP_S)
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#ifdef HAVE_DOSISH_SYSTEM
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#define DIRSEP_C '\\'
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#define EXTSEP_C '.'
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#define DIRSEP_S "\\"
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#define EXTSEP_S "."
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#else
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#define DIRSEP_C '/'
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#define EXTSEP_C '.'
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#define DIRSEP_S "/"
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#define EXTSEP_S "."
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#endif
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#endif
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/* The object describing a lock. */
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struct dotlock_handle
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{
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struct dotlock_handle *next;
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char *lockname; /* Name of the actual lockfile. */
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int locked; /* Lock status. */
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int disable; /* If true, locking is disabled. */
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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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char *tname; /* Name of the lockfile template. */
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size_t nodename_off; /* Offset in TNAME of the nodename part. */
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size_t nodename_len; /* Length of the nodename part. */
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#endif /* HAVE_DOSISH_SYSTEM */
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};
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/* A list of of all lock handles. */
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static volatile dotlock_t 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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/* Local protototypes. */
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#ifndef HAVE_DOSISH_SYSTEM
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static int read_lockfile (dotlock_t h, int *same_node);
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#endif /*!HAVE_DOSISH_SYSTEM*/
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/* Entirely disable all locking. This function should be called
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before any locking is done. It may be called right at startup of
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the process as it only sets a global value. */
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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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/* Create a lockfile for a file name FILE_TO_LOCK and returns an
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object of type dotlock_t which may be used later to actually acquire
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the lock. A cleanup routine gets installed to cleanup left over
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locks or other files used internally by the lock mechanism.
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Calling this function with NULL does only install the atexit
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handler and may thus be used to assure that the cleanup is called
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after all other atexit handlers.
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This function creates a lock file in the same directory as
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FILE_TO_LOCK using that name and a suffix of ".lock". Note that on
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POSIX systems a temporary file ".#lk.<hostname>.pid[.threadid] is
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used.
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The function returns an new handle which needs to be released using
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destroy_dotlock but gets also released at the termination of the
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process. On error NULL is returned.
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*/
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dotlock_t
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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_t 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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const char *nodename;
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const char *dirpart;
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int dirpartlen;
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struct utsname utsbuf;
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size_t tnamelen;
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#endif
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if ( !initialized )
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{
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atexit (dotlock_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; /* Only initialization was requested. */
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h = jnlib_calloc (1, sizeof *h);
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if (!h)
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return NULL;
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if (never_lock)
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{
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h->disable = 1;
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#ifdef _REENTRANT
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/* fixme: aquire mutex on all_lockfiles */
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#endif
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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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/*
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This is the POSIX version which uses a temporary file and the
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link system call to make locking an atomic operation.
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*/
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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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{
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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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{
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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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#ifdef _REENTRANT
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/* fixme: aquire mutex on all_lockfiles */
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#endif
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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 = jnlib_malloc (tnamelen + 1);
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if (!h->tname)
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{
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all_lockfiles = h->next;
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jnlib_free (h);
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return NULL;
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}
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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.", dirpartlen, dirpart, h );
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h->nodename_off = strlen (h->tname);
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snprintf (h->tname+h->nodename_off, tnamelen - h->nodename_off,
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"%s.%d", nodename, (int)getpid ());
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#else /* __riscos__ */
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snprintf (h->tname, tnamelen, "%.*s.lk%p/", dirpartlen, dirpart, h );
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h->nodename_off = strlen (h->tname);
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snprintf (h->tname+h->nodename_off, tnamelen - h->modename_off,
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"%s/%d", nodename, (int)getpid () );
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#endif /* __riscos__ */
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do
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{
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jnlib_set_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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}
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while (fd == -1 && errno == EINTR);
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if ( fd == -1 )
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{
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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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jnlib_free (h->tname);
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jnlib_free (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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# ifdef _REENTRANT
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/* release mutex */
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# endif
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h->lockname = jnlib_malloc ( strlen (file_to_lock) + 6 );
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if (!h->lockname)
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{
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all_lockfiles = h->next;
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unlink (h->tname);
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jnlib_free (h->tname);
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jnlib_free (h);
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return NULL;
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}
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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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# ifdef _REENTRANT
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/* fixme: release mutex */
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# endif
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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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jnlib_free (h->tname);
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jnlib_free (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 = jnlib_malloc ( strlen (file_to_lock) + 6 );
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if (!h->lockname)
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{
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all_lockfiles = h->next;
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jnlib_free (h);
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return NULL;
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}
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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 til until Windows crashes.
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Our solution is to keep the lock file open; that does not
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harm. */
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{
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#ifdef HAVE_W32CE_SYSTEM
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wchar_t *wname = utf8_to_wchar (h->lockname);
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h->lockhd = INVALID_HANDLE_VALUE;
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if (wname)
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h->lockhd = CreateFile (wname,
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#else
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h->lockhd = CreateFile (h->lockname,
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#endif
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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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#ifdef HAVE_W32CE_SYSTEM
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jnlib_free (wname);
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#endif
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}
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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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jnlib_free (h->lockname);
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jnlib_free (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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/* Destroy the local handle H and release the lock. */
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void
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destroy_dotlock (dotlock_t h)
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{
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dotlock_t 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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/* Then 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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{
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OVERLAPPED ovl;
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memset (&ovl, 0, sizeof ovl);
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UnlockFileEx (h->lockhd, 0, 1, 0, &ovl);
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}
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CloseHandle (h->lockhd);
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#else /* !HAVE_DOSISH_SYSTEM */
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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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jnlib_free (h->tname);
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#endif /* HAVE_DOSISH_SYSTEM */
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jnlib_free (h->lockname);
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}
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jnlib_free(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_t h)
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{
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dotlock_t r;
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for ( r=all_lockfiles; r; r = r->next )
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{
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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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/* Do a lock on H. A TIMEOUT of 0 returns immediately, -1 waits
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forever (hopefully not), other values are reserved (should then be
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timeouts in milliseconds). Returns: 0 on success */
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int
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make_dotlock (dotlock_t 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 /*!HAVE_DOSISH_SYSTEM*/
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if ( h->disable )
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return 0; /* Locks are completely disabled. Return success. */
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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 ( !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() && same_node )
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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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/* Under RISCOS we are *pretty* sure that the other task
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is dead and therefore we remove the stale 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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/* Wait until lock has been released. */
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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, cause 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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OVERLAPPED ovl;
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/* Lock one byte at offset 0. The offset is given by OVL. */
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memset (&ovl, 0, sizeof ovl);
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if (LockFileEx (h->lockhd, (LOCKFILE_EXCLUSIVE_LOCK
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| LOCKFILE_FAIL_IMMEDIATELY), 0, 1, 0, &ovl))
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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;
|
||
#endif /*HAVE_DOSISH_SYSTEM*/
|
||
}
|
||
/*NOTREACHED*/
|
||
}
|
||
|
||
|
||
/* Release a lock. Returns 0 on success. */
|
||
int
|
||
release_dotlock (dotlock_t h)
|
||
{
|
||
#ifndef HAVE_DOSISH_SYSTEM
|
||
int pid, same_node;
|
||
#endif
|
||
|
||
/* 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;
|
||
}
|
||
|
||
#ifdef HAVE_DOSISH_SYSTEM
|
||
{
|
||
OVERLAPPED ovl;
|
||
|
||
memset (&ovl, 0, sizeof ovl);
|
||
if (!UnlockFileEx (h->lockhd, 0, 1, 0, &ovl))
|
||
{
|
||
log_error ("release_dotlock: error removing lockfile `%s': %s\n",
|
||
h->lockname, w32_strerror (-1));
|
||
return -1;
|
||
}
|
||
}
|
||
#else
|
||
|
||
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'\n",
|
||
h->lockname);
|
||
return -1;
|
||
}
|
||
/* Fixme: As an extra check we could check whether the link count is
|
||
now really at 1. */
|
||
#else /* __riscos__ */
|
||
if ( renamefile (h->lockname, h->tname) )
|
||
{
|
||
log_error ("release_dotlock: error renaming lockfile `%s' to `%s'\n",
|
||
h->lockname, h->tname);
|
||
return -1;
|
||
}
|
||
#endif /* __riscos__ */
|
||
|
||
#endif /* !HAVE_DOSISH_SYSTEM */
|
||
h->locked = 0;
|
||
return 0;
|
||
}
|
||
|
||
|
||
/* Read the lock file and return the pid, returns -1 on error. True
|
||
will be stored in the integer at address SAME_NODE if the lock file
|
||
has been created on the same node. */
|
||
#ifndef HAVE_DOSISH_SYSTEM
|
||
static int
|
||
read_lockfile (dotlock_t h, int *same_node )
|
||
{
|
||
char buffer_space[10+1+70+1]; /* 70 is just an estimated value; node
|
||
name are usually shorter. */
|
||
int fd;
|
||
int pid = -1;
|
||
char *buffer, *p;
|
||
size_t expected_len;
|
||
int res, nread;
|
||
|
||
*same_node = 0;
|
||
expected_len = 10 + 1 + h->nodename_len + 1;
|
||
if ( expected_len >= sizeof buffer_space)
|
||
{
|
||
buffer = jnlib_malloc (expected_len);
|
||
if (!buffer)
|
||
return -1;
|
||
}
|
||
else
|
||
buffer = buffer_space;
|
||
|
||
if ( (fd = open (h->lockname, O_RDONLY)) == -1 )
|
||
{
|
||
int e = errno;
|
||
log_info ("error opening lockfile `%s': %s\n",
|
||
h->lockname, strerror(errno) );
|
||
if (buffer != buffer_space)
|
||
jnlib_free (buffer);
|
||
jnlib_set_errno (e); /* Need to return ERRNO here. */
|
||
return -1;
|
||
}
|
||
|
||
p = buffer;
|
||
nread = 0;
|
||
do
|
||
{
|
||
res = read (fd, p, expected_len - nread);
|
||
if (res == -1 && errno == EINTR)
|
||
continue;
|
||
if (res < 0)
|
||
{
|
||
log_info ("error reading lockfile `%s'", h->lockname );
|
||
close (fd);
|
||
if (buffer != buffer_space)
|
||
jnlib_free (buffer);
|
||
jnlib_set_errno (0); /* Do not return an inappropriate ERRNO. */
|
||
return -1;
|
||
}
|
||
p += res;
|
||
nread += res;
|
||
}
|
||
while (res && nread != expected_len);
|
||
close(fd);
|
||
|
||
if (nread < 11)
|
||
{
|
||
log_info ("invalid size of lockfile `%s'", h->lockname );
|
||
if (buffer != buffer_space)
|
||
jnlib_free (buffer);
|
||
jnlib_set_errno (0); /* Better don't return an inappropriate ERRNO. */
|
||
return -1;
|
||
}
|
||
|
||
if (buffer[10] != '\n'
|
||
|| (buffer[10] = 0, pid = atoi (buffer)) == -1
|
||
#ifndef __riscos__
|
||
|| !pid
|
||
#else /* __riscos__ */
|
||
|| (!pid && riscos_getpid())
|
||
#endif /* __riscos__ */
|
||
)
|
||
{
|
||
log_error ("invalid pid %d in lockfile `%s'", pid, h->lockname );
|
||
if (buffer != buffer_space)
|
||
jnlib_free (buffer);
|
||
jnlib_set_errno (0);
|
||
return -1;
|
||
}
|
||
|
||
if (nread == expected_len
|
||
&& !memcmp (h->tname+h->nodename_off, buffer+11, h->nodename_len)
|
||
&& buffer[11+h->nodename_len] == '\n')
|
||
*same_node = 1;
|
||
|
||
if (buffer != buffer_space)
|
||
jnlib_free (buffer);
|
||
return pid;
|
||
}
|
||
#endif /* !HAVE_DOSISH_SYSTEM */
|
||
|
||
|
||
/* Remove all lockfiles. This is usually called by the atexit handler
|
||
installed by this module but may also be called by other
|
||
termination handlers. */
|
||
void
|
||
dotlock_remove_lockfiles (void)
|
||
{
|
||
dotlock_t h, h2;
|
||
|
||
h = all_lockfiles;
|
||
all_lockfiles = NULL;
|
||
|
||
while ( h )
|
||
{
|
||
h2 = h->next;
|
||
destroy_dotlock (h);
|
||
h = h2;
|
||
}
|
||
}
|