-/* Copyright (C) 1985, 1986, 1987, 1993 Free Software Foundation, Inc.
+/* Copyright (C) 1985, 86, 87, 93, 94, 96 Free Software Foundation, Inc.
This file is part of GNU Emacs.
You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING. If not, write to
-the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA. */
#include <sys/types.h>
#include <sys/stat.h>
-#include "config.h"
+#include <config.h>
#ifdef VMS
#include "vms-pwd.h"
#else
#include <pwd.h>
-#endif
+#endif /* not VMS */
-#include <errno.h>
#include <sys/file.h>
#ifdef USG
#include <fcntl.h>
+#include <string.h>
#endif /* USG */
#include "lisp.h"
-#include "paths.h"
#include "buffer.h"
+#include <errno.h>
+#ifndef errno
extern int errno;
-
-extern char *egetenv ();
-extern char *strcpy ();
-
-#if defined (__bsdi__) || defined (DECLARE_GETPWUID_WITH_UID_T)
-extern struct passwd *getpwuid (uid_t);
-#else
-extern struct passwd *getpwuid ();
#endif
#ifdef CLASH_DETECTION
-/* If system does not have symbolic links, it does not have lstat.
- In that case, use ordinary stat instead. */
-
-#ifndef S_IFLNK
-#define lstat stat
-#endif
-
+/* The strategy: to lock a file FN, create a symlink .#FN in FN's
+ directory, with link data `user@host.pid'. This avoids a single
+ mount (== failure) point for lock files.
+
+ When the host in the lock data is the current host, we can check if
+ the pid is valid with kill.
+
+ Otherwise, we could look at a separate file that maps hostnames to
+ reboot times to see if the remote pid can possibly be valid, since we
+ don't want Emacs to have to communicate via pipes or sockets or
+ whatever to other processes, either locally or remotely; rms says
+ that's too unreliable. Hence the separate file, which could
+ theoretically be updated by daemons running separately -- but this
+ whole idea is unimplemented; in practice, at least in our
+ environment, it seems such stale locks arise fiarly infrequently, and
+ Emacs' standard methods of dealing with clashes suffice.
+
+ We use symlinks instead of normal files because (1) they can be
+ stored more efficiently on the filesystem, since the kernel knows
+ they will be small, and (2) all the info about the lock can be read
+ in a single system call (readlink). Although we could use regular
+ files to be useful on old systems lacking symlinks, noawdays
+ virtually all such systems are probably single-user anyway, so it
+ didn't seem worth the complication.
+
+ Similarly, we don't worry about a possible 14-character limit on
+ file names, because those are all the same systems that don't have
+ symlinks.
+
+ This is compatible with the locking scheme used by Interleaf (which
+ has contributed this implementation for Emacs), and was designed by
+ Ethan Jacobson, Kimbo Mundy, and others.
+
+ --karl@cs.umb.edu/karl@hq.ileaf.com. */
-/* The name of the directory in which we keep lock files, with a '/'
- appended. */
-char *lock_path;
-
-/* The name of the file in the lock directory which is used to
- arbitrate access to the entire directory. */
-#define SUPERLOCK_NAME "!!!SuperLock!!!"
+\f
+/* Here is the structure that stores information about a lock. */
-/* The path to the superlock file. This is SUPERLOCK_NAME appended to
- lock_path. */
-char *superlock_path;
+typedef struct
+{
+ char *user;
+ char *host;
+ unsigned long pid;
+} lock_info_type;
-/* Set LOCK to the name of the lock file for the filename FILE.
- char *LOCK; Lisp_Object FILE; */
+/* When we read the info back, we might need this much more,
+ enough for decimal representation plus null. */
+#define LOCK_PID_MAX (4 * sizeof (unsigned long))
-#ifndef HAVE_LONG_FILE_NAMES
+/* Free the two dynamically-allocated pieces in PTR. */
+#define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
-#define MAKE_LOCK_PATH(lock, file) \
- (lock = (char *) alloca (14 + strlen (lock_path) + 1), \
- fill_in_lock_short_file_name (lock, (file)))
+/* Write the name of the lock file for FN into LFNAME. Length will be
+ that of FN plus two more for the leading `.#' plus one for the null. */
+#define MAKE_LOCK_NAME(lock, file) \
+ (lock = (char *) alloca (XSTRING (file)->size + 2 + 1), \
+ fill_in_lock_file_name (lock, (file)))
-fill_in_lock_short_file_name (lockfile, fn)
+static void
+fill_in_lock_file_name (lockfile, fn)
register char *lockfile;
register Lisp_Object fn;
{
- register union
- {
- unsigned int word [2];
- unsigned char byte [8];
- } crc;
- register unsigned char *p, new;
+ register char *p;
+
+ strcpy (lockfile, XSTRING (fn)->data);
+
+ /* Shift the nondirectory part of the file name (including the null)
+ right two characters. Here is one of the places where we'd have to
+ do something to support 14-character-max file names. */
+ for (p = lockfile + strlen (lockfile); p != lockfile && *p != '/'; p--)
+ p[2] = *p;
- /* 7-bytes cyclic code for burst correction on byte-by-byte basis.
- the used polynomial is D^7 + D^6 + D^3 +1. pot@cnuce.cnr.it */
+ /* Insert the `.#'. */
+ p[1] = '.';
+ p[2] = '#';
+}
- crc.word[0] = crc.word[1] = 0;
+/* Lock the lock file named LFNAME.
+ If FORCE is nonzero, we do so even if it is already locked.
+ Return 1 if successful, 0 if not. */
+
+static int
+lock_file_1 (lfname, force)
+ char *lfname;
+ int force;
+{
+ register int err;
+ char *user_name = XSTRING (Fuser_login_name (Qnil))->data;
+ char *host_name = XSTRING (Fsystem_name ())->data;
+ char *lock_info_str = alloca (strlen (user_name) + strlen (host_name)
+ + LOCK_PID_MAX + 5);
- for (p = XSTRING (fn)->data; new = *p++; )
+ sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name,
+ (unsigned long) getpid ());
+
+ err = symlink (lock_info_str, lfname);
+ if (errno == EEXIST && force)
{
- new += crc.byte[6];
- crc.byte[6] = crc.byte[5] + new;
- crc.byte[5] = crc.byte[4];
- crc.byte[4] = crc.byte[3];
- crc.byte[3] = crc.byte[2] + new;
- crc.byte[2] = crc.byte[1];
- crc.byte[1] = crc.byte[0];
- crc.byte[0] = new;
+ unlink (lfname);
+ err = symlink (lock_info_str, lfname);
}
- sprintf (lockfile, "%s%.2x%.2x%.2x%.2x%.2x%.2x%.2x", lock_path,
- crc.byte[0], crc.byte[1], crc.byte[2], crc.byte[3],
- crc.byte[4], crc.byte[5], crc.byte[6]);
-}
-#else /* defined HAVE_LONG_FILE_NAMES */
+ return err == 0;
+}
-#define MAKE_LOCK_PATH(lock, file) \
- (lock = (char *) alloca (XSTRING (file)->size + strlen (lock_path) + 1), \
- fill_in_lock_file_name (lock, (file)))
+\f
+/* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete,
+ 1 if another process owns it (and set OWNER (if non-null) to info),
+ 2 if the current process owns it,
+ or -1 if something is wrong with the locking mechanism. */
-fill_in_lock_file_name (lockfile, fn)
- register char *lockfile;
- register Lisp_Object fn;
+static int
+current_lock_owner (owner, lfname)
+ lock_info_type *owner;
+ char *lfname;
{
- register char *p;
-
- strcpy (lockfile, lock_path);
+#ifndef index
+ extern char *rindex (), *index ();
+#endif
+ int o, p, len, ret;
+ int local_owner = 0;
+ char *at, *dot;
+ char *lfinfo = 0;
+ int bufsize = 50;
+ /* Read arbitrarily-long contents of symlink. Similar code in
+ file-symlink-p in fileio.c. */
+ do
+ {
+ bufsize *= 2;
+ lfinfo = (char *) xrealloc (lfinfo, bufsize);
+ len = readlink (lfname, lfinfo, bufsize);
+ }
+ while (len >= bufsize);
+
+ /* If nonexistent lock file, all is well; otherwise, got strange error. */
+ if (len == -1)
+ {
+ xfree (lfinfo);
+ return errno == ENOENT ? 0 : -1;
+ }
- p = lockfile + strlen (lockfile);
+ /* Link info exists, so `len' is its length. Null terminate. */
+ lfinfo[len] = 0;
+
+ /* Even if the caller doesn't want the owner info, we still have to
+ read it to determine return value, so allocate it. */
+ if (!owner)
+ {
+ owner = alloca (sizeof (lock_info_type));
+ local_owner = 1;
+ }
+
+ /* Parse USER@HOST.PID. If can't parse, return -1. */
+ /* The USER is everything before the first @. */
+ at = index (lfinfo, '@');
+ dot = rindex (lfinfo, '.');
+ if (!at || !dot) {
+ xfree (lfinfo);
+ return -1;
+ }
+ len = at - lfinfo;
+ owner->user = (char *) xmalloc (len + 1);
+ strncpy (owner->user, lfinfo, len);
+ owner->user[len] = 0;
+
+ /* The PID is everything after the last `.'. */
+ owner->pid = atoi (dot + 1);
- strcpy (p, XSTRING (fn)->data);
+ /* The host is everything in between. */
+ len = dot - at - 1;
+ owner->host = (char *) xmalloc (len + 1);
+ strncpy (owner->host, at + 1, len);
+ owner->host[len] = 0;
- for (; *p; p++)
+ /* We're done looking at the link info. */
+ xfree (lfinfo);
+
+ /* On current host? */
+ if (strcmp (owner->host, XSTRING (Fsystem_name ())->data) == 0)
+ {
+ if (owner->pid == getpid ())
+ ret = 2; /* We own it. */
+
+ if (owner->pid > 0
+ && (kill (owner->pid, 0) >= 0 || errno == EPERM))
+ ret = 1; /* An existing process on this machine owns it. */
+
+ /* The owner process is dead or has a strange pid (<=0), so try to
+ zap the lockfile. */
+ if (unlink (lfname) < 0)
+ ret = -1;
+
+ ret = 0;
+ }
+ else
+ { /* If we wanted to support the check for stale locks on remote machines,
+ here's where we'd do it. */
+ ret = 1;
+ }
+
+ /* Avoid garbage. */
+ if (local_owner || ret <= 0)
{
- if (*p == '/')
- *p = '!';
+ FREE_LOCK_INFO (*owner);
}
+ return ret;
}
-#endif /* !defined HAVE_LONG_FILE_NAMES */
-static Lisp_Object
-lock_file_owner_name (lfname)
- char *lfname;
+\f
+/* Lock the lock named LFNAME if possible.
+ Return 0 in that case.
+ Return positive if some other process owns the lock, and info about
+ that process in CLASHER.
+ Return -1 if cannot lock for any other reason. */
+
+static int
+lock_if_free (clasher, lfname)
+ lock_info_type *clasher;
+ register char *lfname;
{
- struct stat s;
- struct passwd *the_pw;
+ while (lock_file_1 (lfname, 0) == 0)
+ {
+ int locker;
- if (lstat (lfname, &s) == 0)
- the_pw = getpwuid (s.st_uid);
- return (the_pw == 0 ? Qnil : build_string (the_pw->pw_name));
+ if (errno != EEXIST)
+ return -1;
+
+ locker = current_lock_owner (clasher, lfname);
+ if (locker == 2)
+ {
+ FREE_LOCK_INFO (*clasher);
+ return 0; /* We ourselves locked it. */
+ }
+ else if (locker == 1)
+ return 1; /* Someone else has it. */
+ else if (locker == -1)
+ return -1; /* Something's wrong. */
+
+ /* If some other error, or no such lock, try to lock again. */
+ /* Is there a case where we loop forever? */
+ }
+ return 0;
}
-
-/* lock_file locks file fn,
+/* lock_file locks file FN,
meaning it serves notice on the world that you intend to edit that file.
This should be done only when about to modify a file-visiting
buffer previously unmodified.
- Do not (normally) call lock_buffer for a buffer already modified,
+ Do not (normally) call this for a buffer already modified,
as either the file is already locked, or the user has already
decided to go ahead without locking.
- When lock_buffer returns, either the lock is locked for us,
+ When this returns, either the lock is locked for us,
or the user has said to go ahead without locking.
- If the file is locked by someone else, lock_buffer calls
+ If the file is locked by someone else, this calls
ask-user-about-lock (a Lisp function) with two arguments,
- the file name and the name of the user who did the locking.
+ the file name and info about the user who did the locking.
This function can signal an error, or return t meaning
take away the lock, or return nil meaning ignore the lock. */
-/* The lock file name is the file name with "/" replaced by "!"
- and put in the Emacs lock directory. */
-/* (ie., /ka/king/junk.tex -> /!/!ka!king!junk.tex). */
-
-/* If HAVE_LONG_FILE_NAMES is not defined, the lock file name is the hex
- representation of a 14-bytes CRC generated from the file name
- and put in the Emacs lock directory (not very nice, but it works).
- (ie., /ka/king/junk.tex -> /!/12a82c62f1c6da). */
-
void
lock_file (fn)
- register Lisp_Object fn;
+ register Lisp_Object fn;
{
- register Lisp_Object attack;
- register char *lfname;
+ register Lisp_Object attack, orig_fn;
+ register char *lfname, *locker;
+ lock_info_type lock_info;
+
+ orig_fn = fn;
+ fn = Fexpand_file_name (fn, Qnil);
- MAKE_LOCK_PATH (lfname, fn);
+ /* Create the name of the lock-file for file fn */
+ MAKE_LOCK_NAME (lfname, fn);
/* See if this file is visited and has changed on disk since it was
visited. */
{
- register Lisp_Object subject_buf = Fget_file_buffer (fn);
+ register Lisp_Object subject_buf;
+ subject_buf = get_truename_buffer (orig_fn);
if (!NILP (subject_buf)
&& NILP (Fverify_visited_file_modtime (subject_buf))
&& !NILP (Ffile_exists_p (fn)))
}
/* Try to lock the lock. */
- if (lock_if_free (lfname) <= 0)
- /* Return now if we have locked it, or if lock dir does not exist */
+ if (lock_if_free (&lock_info, lfname) <= 0)
+ /* Return now if we have locked it, or if lock creation failed */
return;
/* Else consider breaking the lock */
- attack = call2 (intern ("ask-user-about-lock"), fn,
- lock_file_owner_name (lfname));
+ locker = alloca (strlen (lock_info.user) + strlen (lock_info.host)
+ + LOCK_PID_MAX + 9);
+ sprintf (locker, "%s@%s (pid %d)", lock_info.user, lock_info.host,
+ lock_info.pid);
+ FREE_LOCK_INFO (lock_info);
+
+ attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker));
if (!NILP (attack))
/* User says take the lock */
{
- lock_superlock (lfname);
- lock_file_1 (lfname, O_WRONLY) ;
- unlink (superlock_path);
+ lock_file_1 (lfname, 1);
return;
}
/* User says ignore the lock */
}
-/* Lock the lock file named LFNAME.
- If MODE is O_WRONLY, we do so even if it is already locked.
- If MODE is O_WRONLY | O_EXCL | O_CREAT, we do so only if it is free.
- Return 1 if successful, 0 if not. */
-
-int
-lock_file_1 (lfname, mode)
- int mode; char *lfname;
-{
- register int fd;
- char buf[20];
-
- if ((fd = open (lfname, mode, 0666)) >= 0)
- {
-#ifdef USG
- chmod (lfname, 0666);
-#else
- fchmod (fd, 0666);
-#endif
- sprintf (buf, "%d ", getpid ());
- write (fd, buf, strlen (buf));
- close (fd);
- return 1;
- }
- else
- return 0;
-}
-
-/* Lock the lock named LFNAME if possible.
- Return 0 in that case.
- Return positive if lock is really locked by someone else.
- Return -1 if cannot lock for any other reason. */
-
-int
-lock_if_free (lfname)
- register char *lfname;
-{
- register int clasher;
-
- while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0)
- {
- if (errno != EEXIST)
- return -1;
- clasher = current_lock_owner (lfname);
- if (clasher != 0)
- if (clasher != getpid ())
- return (clasher);
- else return (0);
- /* Try again to lock it */
- }
- return 0;
-}
-
-/* Return the pid of the process that claims to own the lock file LFNAME,
- or 0 if nobody does or the lock is obsolete,
- or -1 if something is wrong with the locking mechanism. */
-
-int
-current_lock_owner (lfname)
- char *lfname;
-{
- int owner = current_lock_owner_1 (lfname);
- if (owner == 0 && errno == ENOENT)
- return (0);
- /* Is it locked by a process that exists? */
- if (owner != 0 && (kill (owner, 0) >= 0 || errno == EPERM))
- return (owner);
- if (unlink (lfname) < 0)
- return (-1);
- return (0);
-}
-
-int
-current_lock_owner_1 (lfname)
- char *lfname;
-{
- register int fd;
- char buf[20];
- int tem;
-
- fd = open (lfname, O_RDONLY, 0666);
- if (fd < 0)
- return 0;
- tem = read (fd, buf, sizeof buf);
- close (fd);
- return (tem <= 0 ? 0 : atoi (buf));
-}
-
-\f
void
unlock_file (fn)
register Lisp_Object fn;
{
register char *lfname;
- MAKE_LOCK_PATH (lfname, fn);
+ fn = Fexpand_file_name (fn, Qnil);
- lock_superlock (lfname);
+ MAKE_LOCK_NAME (lfname, fn);
- if (current_lock_owner_1 (lfname) == getpid ())
+ if (current_lock_owner (0, lfname) == 2)
unlink (lfname);
-
- unlink (superlock_path);
-}
-
-lock_superlock (lfname)
- char *lfname;
-{
- register int i, fd;
-
- for (i = -20; i < 0 && (fd = open (superlock_path,
- O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0;
- i++)
- {
- if (errno != EEXIST)
- return;
- sleep (1);
- }
- if (fd >= 0)
- {
-#ifdef USG
- chmod (superlock_path, 0666);
-#else
- fchmod (fd, 0666);
-#endif
- write (fd, lfname, strlen (lfname));
- close (fd);
- }
}
void
register Lisp_Object tail;
register struct buffer *b;
- for (tail = Vbuffer_alist; XGCTYPE (tail) == Lisp_Cons;
- tail = XCONS (tail)->cdr)
+ for (tail = Vbuffer_alist; GC_CONSP (tail); tail = XCONS (tail)->cdr)
{
b = XBUFFER (XCONS (XCONS (tail)->car)->cdr);
- if (XTYPE (b->filename) == Lisp_String &&
- b->save_modified < BUF_MODIFF (b))
- unlock_file (b->filename);
+ if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
+ unlock_file (b->file_truename);
}
}
-
\f
DEFUN ("lock-buffer", Flock_buffer, Slock_buffer,
0, 1, 0,
"Lock FILE, if current buffer is modified.\n\
FILE defaults to current buffer's visited file,\n\
or else nothing is done if current buffer isn't visiting a file.")
- (fn)
- Lisp_Object fn;
+ (file)
+ Lisp_Object file;
{
- if (NILP (fn))
- fn = current_buffer->filename;
+ if (NILP (file))
+ file = current_buffer->file_truename;
else
- CHECK_STRING (fn, 0);
- if (current_buffer->save_modified < MODIFF
- && !NILP (fn))
- lock_file (fn);
+ CHECK_STRING (file, 0);
+ if (SAVE_MODIFF < MODIFF
+ && !NILP (file))
+ lock_file (file);
return Qnil;
}
if it should normally be locked.")
()
{
- if (current_buffer->save_modified < MODIFF &&
- XTYPE (current_buffer->filename) == Lisp_String)
- unlock_file (current_buffer->filename);
+ if (SAVE_MODIFF < MODIFF
+ && STRINGP (current_buffer->file_truename))
+ unlock_file (current_buffer->file_truename);
return Qnil;
}
-\f
/* Unlock the file visited in buffer BUFFER. */
unlock_buffer (buffer)
struct buffer *buffer;
{
- if (buffer->save_modified < BUF_MODIFF (buffer) &&
- XTYPE (buffer->filename) == Lisp_String)
- unlock_file (buffer->filename);
+ if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer)
+ && STRINGP (buffer->file_truename))
+ unlock_file (buffer->file_truename);
}
DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 0, 1, 0,
"Return nil if the FILENAME is not locked,\n\
t if it is locked by you, else a string of the name of the locker.")
- (fn)
- Lisp_Object fn;
+ (filename)
+ Lisp_Object filename;
{
+ Lisp_Object ret;
register char *lfname;
int owner;
+ lock_info_type locker;
- fn = Fexpand_file_name (fn, Qnil);
+ filename = Fexpand_file_name (filename, Qnil);
- MAKE_LOCK_PATH (lfname, fn);
+ MAKE_LOCK_NAME (lfname, filename);
- owner = current_lock_owner (lfname);
+ owner = current_lock_owner (&locker, lfname);
if (owner <= 0)
- return (Qnil);
- else if (owner == getpid ())
- return (Qt);
-
- return (lock_file_owner_name (lfname));
+ ret = Qnil;
+ else if (owner == 2)
+ ret = Qt;
+ else
+ ret = build_string (locker.user);
+
+ if (owner > 0)
+ FREE_LOCK_INFO (locker);
+
+ return ret;
}
\f
init_filelock ()
{
- lock_path = egetenv ("EMACSLOCKDIR");
- if (! lock_path)
- lock_path = PATH_LOCK;
+#if 0
+ char *new_name;
+
+ lock_dir = egetenv ("EMACSLOCKDIR");
+ if (! lock_dir)
+ lock_dir = PATH_LOCK;
+
+ /* Copy the name in case egetenv got it from a Lisp string. */
+ new_name = (char *) xmalloc (strlen (lock_dir) + 2);
+ strcpy (new_name, lock_dir);
+ lock_dir = new_name;
/* Make sure it ends with a slash. */
- if (lock_path[strlen (lock_path) - 1] != '/')
- {
- char *new_path = (char *) xmalloc (strlen (lock_path) + 2);
- strcpy (new_path, lock_path);
- lock_path = new_path;
- strcat (lock_path, "/");
- }
+ if (lock_dir[strlen (lock_dir) - 1] != '/')
+ strcat (lock_dir, "/");
- superlock_path = (char *) xmalloc ((strlen (lock_path)
+ superlock_file = (char *) xmalloc ((strlen (lock_dir)
+ sizeof (SUPERLOCK_NAME)));
- strcpy (superlock_path, lock_path);
- strcat (superlock_path, SUPERLOCK_NAME);
+ strcpy (superlock_file, lock_dir);
+ strcat (superlock_file, SUPERLOCK_NAME);
+#endif
}
syms_of_filelock ()