-/* Copyright (C) 1985, 1986, 1987 Free Software Foundation, Inc.
+/* Copyright (C) 1985, 86, 87, 93, 94, 96 Free Software Foundation, Inc.
This file is part of GNU Emacs.
GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 1, or (at your option)
+the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Emacs is distributed in the hope that it will be useful,
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 "pwd.h"
+#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 <time.h>
+#include <utmp.h>
+#include <errno.h>
+#ifndef errno
extern int errno;
+#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 fairly 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, nowadays
+ 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. */
-static Lisp_Object
-lock_file_owner_name (lfname)
- char *lfname;
-{
- struct stat s;
- struct passwd *the_pw;
- extern struct passwd *getpwuid ();
+\f
+/* Return the time of the last system boot. */
- if (lstat (lfname, &s) == 0)
- the_pw = getpwuid (s.st_uid);
- return (the_pw == 0 ? Qnil : build_string (the_pw->pw_name));
-}
+static time_t boot_time;
+static time_t
+get_boot_time ()
+{
+#ifdef BOOT_TIME
+ struct utmp ut, *utp;
-/* 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,
- as either the file is already locked, or the user has already
- decided to go ahead without locking.
+ if (boot_time)
+ return boot_time;
- When lock_buffer returns, either the lock is locked for us,
- or the user has said to go ahead without locking.
+ utmpname ("/var/log/wtmp");
+ ut.ut_type = BOOT_TIME;
+ utp = getutid (&ut);
+ endutent ();
- If the file is locked by someone else, lock_buffer calls
- ask-user-about-lock (a Lisp function) with two arguments,
- the file name and the name of 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 (!utp)
+ return boot_time = 1;
+ return boot_time = utp->ut_time;
+#else
+ return 0;
+#endif;
+}
+\f
+/* Here is the structure that stores information about a lock. */
-void
-lock_file (fn)
- register Lisp_Object fn;
+typedef struct
{
- register Lisp_Object attack;
- register char *lfname;
+ char *user;
+ char *host;
+ unsigned long pid;
+ time_t boot_time;
+} lock_info_type;
- /* Create the name of the lock-file for file fn */
- lfname = (char *) alloca (XSTRING (fn)->size + strlen (PATH_LOCK) + 1);
- fill_in_lock_file_name (lfname, fn);
+/* 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))
- /* See if this file is visited and has changed on disk since it was visited. */
- {
- register Lisp_Object subject_buf = Fget_file_buffer (fn);
- if (!NILP (subject_buf)
- && NILP (Fverify_visited_file_modtime (subject_buf))
- && !NILP (Ffile_exists_p (fn)))
- call1 (intern ("ask-user-about-supersession-threat"), fn);
- }
+/* Free the two dynamically-allocated pieces in PTR. */
+#define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
- /* 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 */
- return;
- /* Else consider breaking the lock */
- attack = call2 (intern ("ask-user-about-lock"), fn,
- lock_file_owner_name (lfname));
- if (!NILP (attack))
- /* User says take the lock */
- {
- lock_superlock (lfname);
- lock_file_1 (lfname, O_WRONLY) ;
- unlink (PATH_SUPERLOCK);
- return;
- }
- /* User says ignore the lock */
-}
+/* 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_byte + 2 + 1), \
+ fill_in_lock_file_name (lock, (file)))
+static void
fill_in_lock_file_name (lockfile, fn)
register char *lockfile;
register Lisp_Object fn;
{
register char *p;
- strcpy (lockfile, PATH_LOCK);
+ 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;
+
+ /* Insert the `.#'. */
+ p[1] = '.';
+ p[2] = '#';
+}
- p = lockfile + strlen (lockfile);
+/* 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. */
- strcpy (p, XSTRING (fn)->data);
+static int
+lock_file_1 (lfname, force)
+ char *lfname;
+ int force;
+{
+ register int err;
+ time_t boot_time;
+ char *user_name;
+ char *host_name;
+ char *lock_info_str;
+
+ if (STRINGP (Fuser_login_name (Qnil)))
+ user_name = (char *)XSTRING (Fuser_login_name (Qnil))->data;
+ else
+ user_name = "";
+ if (STRINGP (Fsystem_name ()))
+ host_name = (char *)XSTRING (Fsystem_name ())->data;
+ else
+ host_name = "";
+ lock_info_str = (char *)alloca (strlen (user_name) + strlen (host_name)
+ + LOCK_PID_MAX + 5);
+
+ boot_time = get_boot_time ();
+ if (boot_time)
+ sprintf (lock_info_str, "%s@%s.%lu:%lu", user_name, host_name,
+ (unsigned long) getpid (), (unsigned long) boot_time);
+ else
+ sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name,
+ (unsigned long) getpid ());
- for (; *p; p++)
+ err = symlink (lock_info_str, lfname);
+ if (errno == EEXIST && force)
{
- if (*p == '/')
- *p = '!';
+ unlink (lfname);
+ err = symlink (lock_info_str, lfname);
}
+
+ return err == 0;
}
-/* 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;
+\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. */
+
+static int
+current_lock_owner (owner, lfname)
+ lock_info_type *owner;
+ char *lfname;
{
- register int fd;
- char buf[20];
+#ifndef index
+ extern char *rindex (), *index ();
+#endif
+ int o, p, len, ret;
+ int local_owner = 0;
+ char *at, *dot, *colon;
+ 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;
+ }
- if ((fd = open (lfname, mode, 0666)) >= 0)
+ /* 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)
{
-#ifdef USG
- chmod (lfname, 0666);
-#else
- fchmod (fd, 0666);
-#endif
- sprintf (buf, "%d ", getpid ());
- write (fd, buf, strlen (buf));
- close (fd);
- return 1;
+ owner = (lock_info_type *) alloca (sizeof (lock_info_type));
+ local_owner = 1;
+ }
+
+ /* Parse USER@HOST.PID:BOOT_TIME. 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 from the last `.' to the `:'. */
+ owner->pid = atoi (dot + 1);
+ colon = dot;
+ while (*colon && *colon != ':')
+ colon++;
+ /* After the `:', if there is one, comes the boot time. */
+ if (*colon == ':')
+ owner->boot_time = atoi (colon + 1);
+ else
+ owner->boot_time = 0;
+
+ /* 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;
+
+ /* We're done looking at the link info. */
+ xfree (lfinfo);
+
+ /* On current host? */
+ if (STRINGP (Fsystem_name ())
+ && strcmp (owner->host, XSTRING (Fsystem_name ())->data) == 0)
+ {
+ if (owner->pid == getpid ())
+ ret = 2; /* We own it. */
+ else if (owner->pid > 0
+ && (kill (owner->pid, 0) >= 0 || errno == EPERM)
+ && (owner->boot_time == 0
+ || owner->boot_time == get_boot_time ()))
+ 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. */
+ else if (unlink (lfname) < 0)
+ ret = -1;
+ else
+ ret = 0;
}
else
- return 0;
+ { /* 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)
+ {
+ FREE_LOCK_INFO (*owner);
+ }
+ return ret;
}
+\f
/* Lock the lock named LFNAME if possible.
Return 0 in that case.
- Return positive if lock is really locked by someone else.
+ 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. */
-int
-lock_if_free (lfname)
+static int
+lock_if_free (clasher, lfname)
+ lock_info_type *clasher;
register char *lfname;
{
- register int clasher;
-
- while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0)
+ if (lock_file_1 (lfname, 0) == 0)
{
+ int locker;
+
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 */
+
+ 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. */
+
+ return -1; /* Something's wrong. */
}
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. */
+/* 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 this for a buffer already modified,
+ as either the file is already locked, or the user has already
+ decided to go ahead without locking.
-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);
-}
+ When this returns, either the lock is locked for us,
+ or the user has said to go ahead without locking.
-int
-current_lock_owner_1 (lfname)
- char *lfname;
+ If the file is locked by someone else, this calls
+ ask-user-about-lock (a Lisp function) with two arguments,
+ 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. */
+
+void
+lock_file (fn)
+ register Lisp_Object fn;
{
- 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));
+ register Lisp_Object attack, orig_fn;
+ register char *lfname, *locker;
+ lock_info_type lock_info;
+
+ orig_fn = fn;
+ fn = Fexpand_file_name (fn, Qnil);
+
+ /* 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;
+ subject_buf = get_truename_buffer (orig_fn);
+ if (!NILP (subject_buf)
+ && NILP (Fverify_visited_file_modtime (subject_buf))
+ && !NILP (Ffile_exists_p (fn)))
+ call1 (intern ("ask-user-about-supersession-threat"), fn);
+ }
+
+ /* Try to lock the lock. */
+ 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 */
+ locker = (char *) alloca (strlen (lock_info.user) + strlen (lock_info.host)
+ + LOCK_PID_MAX + 9);
+ sprintf (locker, "%s@%s (pid %lu)", 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_file_1 (lfname, 1);
+ return;
+ }
+ /* User says ignore the lock */
}
-\f
void
unlock_file (fn)
register Lisp_Object fn;
{
register char *lfname;
- lfname = (char *) alloca (XSTRING (fn)->size + strlen (PATH_LOCK) + 1);
- fill_in_lock_file_name (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 (PATH_SUPERLOCK);
-}
-
-lock_superlock (lfname)
- char *lfname;
-{
- register int i, fd;
-
- for (i = -20; i < 0 && (fd = open (PATH_SUPERLOCK,
- O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0;
- i++)
- {
- if (errno != EEXIST)
- return;
- sleep (1);
- }
- if (fd >= 0)
- {
-#ifdef USG
- chmod (PATH_SUPERLOCK, 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))
+ {
+ register char *lfname;
+
+ MAKE_LOCK_NAME (lfname, b->file_truename);
+
+ if (current_lock_owner (0, lfname) == 2)
+ unlink (lfname);
+ }
}
}
-
\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. */
+void
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);
- /* Create the name of the lock-file for file filename */
- lfname = (char *) alloca (XSTRING (fn)->size + strlen (PATH_LOCK) + 1);
- fill_in_lock_file_name (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
+/* Initialization functions. */
syms_of_filelock ()
{
HCoop / bpt / emacs.git / blobdiff