|
373
|
1 /* Copyright (C) 1985, 86, 87, 93, 94, 96 Free Software Foundation, Inc.
|
|
0
|
2
|
|
373
|
3 This file is part of GNU Emacs.
|
|
0
|
4
|
|
373
|
5 GNU Emacs is free software; you can redistribute it and/or modify
|
|
|
6 it under the terms of the GNU General Public License as published by
|
|
|
7 the Free Software Foundation; either version 2, or (at your option)
|
|
|
8 any later version.
|
|
0
|
9
|
|
373
|
10 GNU Emacs is distributed in the hope that it will be useful,
|
|
|
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
|
13 GNU General Public License for more details.
|
|
0
|
14
|
|
|
15 You should have received a copy of the GNU General Public License
|
|
373
|
16 along with GNU Emacs; see the file COPYING. If not, write to
|
|
0
|
17 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
|
|
|
18 Boston, MA 02111-1307, USA. */
|
|
|
19
|
|
373
|
20 /* Synced with FSF 20.2 */
|
|
0
|
21
|
|
|
22 #include <config.h>
|
|
|
23 #include "lisp.h"
|
|
|
24
|
|
|
25 #include "buffer.h"
|
|
159
|
26 #include <paths.h>
|
|
0
|
27
|
|
|
28 #include "sysfile.h"
|
|
|
29 #include "sysdir.h"
|
|
|
30 #include "syspwd.h"
|
|
|
31 #include "syssignal.h" /* for kill */
|
|
|
32
|
|
|
33 Lisp_Object Qask_user_about_supersession_threat;
|
|
|
34 Lisp_Object Qask_user_about_lock;
|
|
|
35
|
|
373
|
36 #ifdef CLASH_DETECTION
|
|
406
|
37
|
|
373
|
38 /* The strategy: to lock a file FN, create a symlink .#FN in FN's
|
|
|
39 directory, with link data `user@host.pid'. This avoids a single
|
|
|
40 mount (== failure) point for lock files.
|
|
0
|
41
|
|
373
|
42 When the host in the lock data is the current host, we can check if
|
|
|
43 the pid is valid with kill.
|
|
406
|
44
|
|
373
|
45 Otherwise, we could look at a separate file that maps hostnames to
|
|
|
46 reboot times to see if the remote pid can possibly be valid, since we
|
|
|
47 don't want Emacs to have to communicate via pipes or sockets or
|
|
|
48 whatever to other processes, either locally or remotely; rms says
|
|
|
49 that's too unreliable. Hence the separate file, which could
|
|
|
50 theoretically be updated by daemons running separately -- but this
|
|
|
51 whole idea is unimplemented; in practice, at least in our
|
|
|
52 environment, it seems such stale locks arise fairly infrequently, and
|
|
|
53 Emacs' standard methods of dealing with clashes suffice.
|
|
0
|
54
|
|
373
|
55 We use symlinks instead of normal files because (1) they can be
|
|
|
56 stored more efficiently on the filesystem, since the kernel knows
|
|
|
57 they will be small, and (2) all the info about the lock can be read
|
|
|
58 in a single system call (readlink). Although we could use regular
|
|
|
59 files to be useful on old systems lacking symlinks, nowadays
|
|
|
60 virtually all such systems are probably single-user anyway, so it
|
|
|
61 didn't seem worth the complication.
|
|
0
|
62
|
|
373
|
63 Similarly, we don't worry about a possible 14-character limit on
|
|
|
64 file names, because those are all the same systems that don't have
|
|
|
65 symlinks.
|
|
406
|
66
|
|
373
|
67 This is compatible with the locking scheme used by Interleaf (which
|
|
|
68 has contributed this implementation for Emacs), and was designed by
|
|
|
69 Ethan Jacobson, Kimbo Mundy, and others.
|
|
406
|
70
|
|
373
|
71 --karl@cs.umb.edu/karl@hq.ileaf.com. */
|
|
0
|
72
|
|
406
|
73 /* Note that muleization is provided by using mule-encapsulated
|
|
|
74 versions of the system calls we use like symlink(), unlink(), etc... */
|
|
|
75
|
|
373
|
76
|
|
|
77 /* Here is the structure that stores information about a lock. */
|
|
0
|
78
|
|
373
|
79 typedef struct
|
|
|
80 {
|
|
|
81 char *user;
|
|
|
82 char *host;
|
|
|
83 unsigned long pid;
|
|
|
84 } lock_info_type;
|
|
0
|
85
|
|
373
|
86 /* When we read the info back, we might need this much more,
|
|
|
87 enough for decimal representation plus null. */
|
|
|
88 #define LOCK_PID_MAX (4 * sizeof (unsigned long))
|
|
0
|
89
|
|
373
|
90 /* Free the two dynamically-allocated pieces in PTR. */
|
|
|
91 #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
|
|
0
|
92
|
|
373
|
93 /* Write the name of the lock file for FN into LFNAME. Length will be
|
|
|
94 that of FN plus two more for the leading `.#' plus one for the null. */
|
|
|
95 #define MAKE_LOCK_NAME(lock, file) \
|
|
406
|
96 (lock = (char *) alloca (XSTRING_LENGTH (file) + 2 + 1), \
|
|
|
97 fill_in_lock_file_name ((Bufbyte *) (lock), (file)))
|
|
0
|
98
|
|
|
99 static void
|
|
406
|
100 fill_in_lock_file_name (Bufbyte *lockfile, Lisp_Object fn)
|
|
0
|
101 {
|
|
406
|
102 Bufbyte *file_name = XSTRING_DATA (fn);
|
|
|
103 Bufbyte *p;
|
|
|
104 size_t dirlen;
|
|
373
|
105
|
|
406
|
106 for (p = file_name + XSTRING_LENGTH (fn) - 1;
|
|
|
107 p > file_name && !IS_ANY_SEP (p[-1]);
|
|
|
108 p--)
|
|
|
109 ;
|
|
|
110 dirlen = p - file_name;
|
|
373
|
111
|
|
406
|
112 memcpy (lockfile, file_name, dirlen);
|
|
|
113 p = lockfile + dirlen;
|
|
|
114 *(p++) = '.';
|
|
|
115 *(p++) = '#';
|
|
|
116 memcpy (p, file_name + dirlen, XSTRING_LENGTH (fn) - dirlen + 1);
|
|
373
|
117 }
|
|
|
118
|
|
|
119 /* Lock the lock file named LFNAME.
|
|
|
120 If FORCE is nonzero, we do so even if it is already locked.
|
|
|
121 Return 1 if successful, 0 if not. */
|
|
0
|
122
|
|
373
|
123 static int
|
|
406
|
124 lock_file_1 (char *lfname, int force)
|
|
373
|
125 {
|
|
406
|
126 int err;
|
|
|
127 char *lock_info_str;
|
|
373
|
128 char *host_name;
|
|
406
|
129 char *user_name = user_login_name (NULL);
|
|
373
|
130
|
|
406
|
131 if (user_name == NULL)
|
|
373
|
132 user_name = "";
|
|
406
|
133
|
|
|
134 if (STRINGP (Vsystem_name))
|
|
|
135 host_name = (char *) XSTRING_DATA (Vsystem_name);
|
|
373
|
136 else
|
|
|
137 host_name = "";
|
|
406
|
138
|
|
373
|
139 lock_info_str = (char *)alloca (strlen (user_name) + strlen (host_name)
|
|
|
140 + LOCK_PID_MAX + 5);
|
|
0
|
141
|
|
373
|
142 sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name,
|
|
|
143 (unsigned long) getpid ());
|
|
0
|
144
|
|
373
|
145 err = symlink (lock_info_str, lfname);
|
|
406
|
146 if (err != 0 && errno == EEXIST && force)
|
|
373
|
147 {
|
|
|
148 unlink (lfname);
|
|
|
149 err = symlink (lock_info_str, lfname);
|
|
|
150 }
|
|
|
151
|
|
|
152 return err == 0;
|
|
|
153 }
|
|
|
154
|
|
|
155 /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete,
|
|
|
156 1 if another process owns it (and set OWNER (if non-null) to info),
|
|
|
157 2 if the current process owns it,
|
|
|
158 or -1 if something is wrong with the locking mechanism. */
|
|
0
|
159
|
|
373
|
160 static int
|
|
|
161 current_lock_owner (lock_info_type *owner, char *lfname)
|
|
|
162 {
|
|
406
|
163 int len, ret;
|
|
373
|
164 int local_owner = 0;
|
|
|
165 char *at, *dot;
|
|
|
166 char *lfinfo = 0;
|
|
|
167 int bufsize = 50;
|
|
|
168 /* Read arbitrarily-long contents of symlink. Similar code in
|
|
|
169 file-symlink-p in fileio.c. */
|
|
|
170 do
|
|
0
|
171 {
|
|
373
|
172 bufsize *= 2;
|
|
|
173 lfinfo = (char *) xrealloc (lfinfo, bufsize);
|
|
|
174 len = readlink (lfname, lfinfo, bufsize);
|
|
|
175 }
|
|
|
176 while (len >= bufsize);
|
|
406
|
177
|
|
373
|
178 /* If nonexistent lock file, all is well; otherwise, got strange error. */
|
|
|
179 if (len == -1)
|
|
|
180 {
|
|
|
181 xfree (lfinfo);
|
|
|
182 return errno == ENOENT ? 0 : -1;
|
|
0
|
183 }
|
|
|
184
|
|
373
|
185 /* Link info exists, so `len' is its length. Null terminate. */
|
|
|
186 lfinfo[len] = 0;
|
|
406
|
187
|
|
373
|
188 /* Even if the caller doesn't want the owner info, we still have to
|
|
|
189 read it to determine return value, so allocate it. */
|
|
|
190 if (!owner)
|
|
0
|
191 {
|
|
373
|
192 owner = (lock_info_type *) alloca (sizeof (lock_info_type));
|
|
|
193 local_owner = 1;
|
|
0
|
194 }
|
|
406
|
195
|
|
373
|
196 /* Parse USER@HOST.PID. If can't parse, return -1. */
|
|
|
197 /* The USER is everything before the first @. */
|
|
382
|
198 at = strchr (lfinfo, '@');
|
|
|
199 dot = strrchr (lfinfo, '.');
|
|
373
|
200 if (!at || !dot) {
|
|
|
201 xfree (lfinfo);
|
|
|
202 return -1;
|
|
|
203 }
|
|
|
204 len = at - lfinfo;
|
|
|
205 owner->user = (char *) xmalloc (len + 1);
|
|
|
206 strncpy (owner->user, lfinfo, len);
|
|
|
207 owner->user[len] = 0;
|
|
406
|
208
|
|
373
|
209 /* The PID is everything after the last `.'. */
|
|
|
210 owner->pid = atoi (dot + 1);
|
|
|
211
|
|
|
212 /* The host is everything in between. */
|
|
|
213 len = dot - at - 1;
|
|
|
214 owner->host = (char *) xmalloc (len + 1);
|
|
|
215 strncpy (owner->host, at + 1, len);
|
|
|
216 owner->host[len] = 0;
|
|
0
|
217
|
|
373
|
218 /* We're done looking at the link info. */
|
|
|
219 xfree (lfinfo);
|
|
406
|
220
|
|
373
|
221 /* On current host? */
|
|
406
|
222 if (STRINGP (Fsystem_name ())
|
|
|
223 && strcmp (owner->host, (char *) XSTRING_DATA (Fsystem_name ())) == 0)
|
|
373
|
224 {
|
|
|
225 if (owner->pid == getpid ())
|
|
|
226 ret = 2; /* We own it. */
|
|
|
227 else if (owner->pid > 0
|
|
|
228 && (kill (owner->pid, 0) >= 0 || errno == EPERM))
|
|
|
229 ret = 1; /* An existing process on this machine owns it. */
|
|
|
230 /* The owner process is dead or has a strange pid (<=0), so try to
|
|
|
231 zap the lockfile. */
|
|
|
232 else if (unlink (lfname) < 0)
|
|
|
233 ret = -1;
|
|
|
234 else
|
|
|
235 ret = 0;
|
|
|
236 }
|
|
|
237 else
|
|
|
238 { /* If we wanted to support the check for stale locks on remote machines,
|
|
|
239 here's where we'd do it. */
|
|
|
240 ret = 1;
|
|
|
241 }
|
|
406
|
242
|
|
373
|
243 /* Avoid garbage. */
|
|
|
244 if (local_owner || ret <= 0)
|
|
|
245 {
|
|
|
246 FREE_LOCK_INFO (*owner);
|
|
|
247 }
|
|
|
248 return ret;
|
|
|
249 }
|
|
|
250
|
|
|
251 /* Lock the lock named LFNAME if possible.
|
|
|
252 Return 0 in that case.
|
|
|
253 Return positive if some other process owns the lock, and info about
|
|
|
254 that process in CLASHER.
|
|
|
255 Return -1 if cannot lock for any other reason. */
|
|
|
256
|
|
|
257 static int
|
|
|
258 lock_if_free (lock_info_type *clasher, char *lfname)
|
|
0
|
259 {
|
|
373
|
260 if (lock_file_1 (lfname, 0) == 0)
|
|
|
261 {
|
|
|
262 int locker;
|
|
0
|
263
|
|
373
|
264 if (errno != EEXIST)
|
|
|
265 return -1;
|
|
406
|
266
|
|
373
|
267 locker = current_lock_owner (clasher, lfname);
|
|
|
268 if (locker == 2)
|
|
|
269 {
|
|
|
270 FREE_LOCK_INFO (*clasher);
|
|
|
271 return 0; /* We ourselves locked it. */
|
|
|
272 }
|
|
|
273 else if (locker == 1)
|
|
|
274 return 1; /* Someone else has it. */
|
|
|
275
|
|
|
276 return -1; /* Something's wrong. */
|
|
|
277 }
|
|
|
278 return 0;
|
|
0
|
279 }
|
|
|
280
|
|
373
|
281 /* lock_file locks file FN,
|
|
0
|
282 meaning it serves notice on the world that you intend to edit that file.
|
|
|
283 This should be done only when about to modify a file-visiting
|
|
|
284 buffer previously unmodified.
|
|
373
|
285 Do not (normally) call this for a buffer already modified,
|
|
0
|
286 as either the file is already locked, or the user has already
|
|
|
287 decided to go ahead without locking.
|
|
|
288
|
|
373
|
289 When this returns, either the lock is locked for us,
|
|
0
|
290 or the user has said to go ahead without locking.
|
|
|
291
|
|
373
|
292 If the file is locked by someone else, this calls
|
|
0
|
293 ask-user-about-lock (a Lisp function) with two arguments,
|
|
373
|
294 the file name and info about the user who did the locking.
|
|
0
|
295 This function can signal an error, or return t meaning
|
|
|
296 take away the lock, or return nil meaning ignore the lock. */
|
|
|
297
|
|
|
298 void
|
|
|
299 lock_file (Lisp_Object fn)
|
|
|
300 {
|
|
114
|
301 /* This function can GC. */
|
|
|
302 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
|
303 mean nasty things with pointy teeth. If you call this make sure
|
|
|
304 you protect things right. */
|
|
406
|
305 /* Somebody updated the code in this function and removed the previous
|
|
373
|
306 comment. -slb */
|
|
114
|
307
|
|
373
|
308 register Lisp_Object attack, orig_fn;
|
|
|
309 register char *lfname, *locker;
|
|
|
310 lock_info_type lock_info;
|
|
|
311 struct gcpro gcpro1,gcpro2;
|
|
|
312 Lisp_Object subject_buf;
|
|
0
|
313
|
|
|
314 GCPRO2 (fn, subject_buf);
|
|
|
315 orig_fn = fn;
|
|
|
316 fn = Fexpand_file_name (fn, Qnil);
|
|
|
317
|
|
|
318 /* Create the name of the lock-file for file fn */
|
|
|
319 MAKE_LOCK_NAME (lfname, fn);
|
|
|
320
|
|
|
321 /* See if this file is visited and has changed on disk since it was
|
|
|
322 visited. */
|
|
373
|
323 {
|
|
|
324 subject_buf = get_truename_buffer (orig_fn);
|
|
|
325 if (!NILP (subject_buf)
|
|
|
326 && NILP (Fverify_visited_file_modtime (subject_buf))
|
|
|
327 && !NILP (Ffile_exists_p (fn)))
|
|
|
328 call1_in_buffer (XBUFFER(subject_buf),
|
|
406
|
329 Qask_user_about_supersession_threat, fn);
|
|
373
|
330 }
|
|
0
|
331
|
|
|
332 /* Try to lock the lock. */
|
|
373
|
333 if (lock_if_free (&lock_info, lfname) <= 0)
|
|
|
334 /* Return now if we have locked it, or if lock creation failed */
|
|
0
|
335 goto done;
|
|
|
336
|
|
|
337 /* Else consider breaking the lock */
|
|
373
|
338 locker = (char *) alloca (strlen (lock_info.user) + strlen (lock_info.host)
|
|
|
339 + LOCK_PID_MAX + 9);
|
|
|
340 sprintf (locker, "%s@%s (pid %lu)", lock_info.user, lock_info.host,
|
|
|
341 lock_info.pid);
|
|
|
342 FREE_LOCK_INFO (lock_info);
|
|
406
|
343
|
|
0
|
344 attack = call2_in_buffer (BUFFERP (subject_buf) ? XBUFFER (subject_buf) :
|
|
373
|
345 current_buffer, Qask_user_about_lock , fn,
|
|
|
346 build_string (locker));
|
|
0
|
347 if (!NILP (attack))
|
|
|
348 /* User says take the lock */
|
|
|
349 {
|
|
373
|
350 lock_file_1 (lfname, 1);
|
|
0
|
351 goto done;
|
|
|
352 }
|
|
|
353 /* User says ignore the lock */
|
|
|
354 done:
|
|
|
355 UNGCPRO;
|
|
|
356 }
|
|
|
357
|
|
|
358 void
|
|
|
359 unlock_file (Lisp_Object fn)
|
|
|
360 {
|
|
373
|
361 register char *lfname;
|
|
406
|
362 struct gcpro gcpro1;
|
|
|
363
|
|
|
364 GCPRO1 (fn);
|
|
0
|
365
|
|
|
366 fn = Fexpand_file_name (fn, Qnil);
|
|
|
367
|
|
|
368 MAKE_LOCK_NAME (lfname, fn);
|
|
|
369
|
|
373
|
370 if (current_lock_owner (0, lfname) == 2)
|
|
0
|
371 unlink (lfname);
|
|
406
|
372
|
|
|
373 UNGCPRO;
|
|
0
|
374 }
|
|
|
375
|
|
|
376 void
|
|
404
|
377 unlock_all_files (void)
|
|
0
|
378 {
|
|
373
|
379 register Lisp_Object tail;
|
|
114
|
380
|
|
398
|
381 for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail))
|
|
0
|
382 {
|
|
406
|
383 struct buffer *b = XBUFFER (XCDR (XCAR (tail)));
|
|
373
|
384 if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
|
|
0
|
385 unlock_file (b->file_truename);
|
|
|
386 }
|
|
|
387 }
|
|
|
388
|
|
373
|
389 DEFUN ("lock-buffer", Flock_buffer, 0, 1, 0, /*
|
|
406
|
390 Lock FILE, if current buffer is modified.
|
|
|
391 FILE defaults to current buffer's visited file,
|
|
0
|
392 or else nothing is done if current buffer isn't visiting a file.
|
|
20
|
393 */
|
|
406
|
394 (file))
|
|
0
|
395 {
|
|
373
|
396 if (NILP (file))
|
|
|
397 file = current_buffer->file_truename;
|
|
|
398 CHECK_STRING (file);
|
|
0
|
399 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
|
|
373
|
400 && !NILP (file))
|
|
|
401 lock_file (file);
|
|
185
|
402 return Qnil;
|
|
0
|
403 }
|
|
|
404
|
|
20
|
405 DEFUN ("unlock-buffer", Funlock_buffer, 0, 0, 0, /*
|
|
0
|
406 Unlock the file visited in the current buffer,
|
|
|
407 if it should normally be locked.
|
|
20
|
408 */
|
|
|
409 ())
|
|
0
|
410 {
|
|
114
|
411 /* This function can GC */
|
|
|
412 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
|
413 mean nasty things with pointy teeth. If you call this make sure
|
|
|
414 you protect things right. */
|
|
|
415
|
|
0
|
416 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
|
|
|
417 && STRINGP (current_buffer->file_truename))
|
|
|
418 unlock_file (current_buffer->file_truename);
|
|
|
419 return Qnil;
|
|
|
420 }
|
|
|
421
|
|
|
422 /* Unlock the file visited in buffer BUFFER. */
|
|
|
423
|
|
373
|
424
|
|
0
|
425 void
|
|
|
426 unlock_buffer (struct buffer *buffer)
|
|
|
427 {
|
|
114
|
428 /* This function can GC */
|
|
|
429 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
|
430 mean nasty things with pointy teeth. If you call this make sure
|
|
|
431 you protect things right. */
|
|
0
|
432 if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer)
|
|
|
433 && STRINGP (buffer->file_truename))
|
|
|
434 unlock_file (buffer->file_truename);
|
|
|
435 }
|
|
|
436
|
|
20
|
437 DEFUN ("file-locked-p", Ffile_locked_p, 0, 1, 0, /*
|
|
406
|
438 Return nil if the FILENAME is not locked,
|
|
0
|
439 t if it is locked by you, else a string of the name of the locker.
|
|
20
|
440 */
|
|
406
|
441 (filename))
|
|
0
|
442 {
|
|
373
|
443 Lisp_Object ret;
|
|
|
444 register char *lfname;
|
|
0
|
445 int owner;
|
|
373
|
446 lock_info_type locker;
|
|
406
|
447 struct gcpro gcpro1;
|
|
|
448
|
|
|
449 GCPRO1 (filename);
|
|
0
|
450
|
|
373
|
451 filename = Fexpand_file_name (filename, Qnil);
|
|
|
452
|
|
|
453 MAKE_LOCK_NAME (lfname, filename);
|
|
0
|
454
|
|
373
|
455 owner = current_lock_owner (&locker, lfname);
|
|
0
|
456 if (owner <= 0)
|
|
373
|
457 ret = Qnil;
|
|
|
458 else if (owner == 2)
|
|
|
459 ret = Qt;
|
|
|
460 else
|
|
|
461 ret = build_string (locker.user);
|
|
185
|
462
|
|
373
|
463 if (owner > 0)
|
|
|
464 FREE_LOCK_INFO (locker);
|
|
|
465
|
|
406
|
466 UNGCPRO;
|
|
|
467
|
|
373
|
468 return ret;
|
|
0
|
469 }
|
|
|
470
|
|
373
|
471
|
|
|
472 /* Initialization functions. */
|
|
|
473
|
|
0
|
474 void
|
|
|
475 syms_of_filelock (void)
|
|
|
476 {
|
|
|
477 /* This function can GC */
|
|
20
|
478 DEFSUBR (Funlock_buffer);
|
|
|
479 DEFSUBR (Flock_buffer);
|
|
|
480 DEFSUBR (Ffile_locked_p);
|
|
0
|
481
|
|
|
482 defsymbol (&Qask_user_about_supersession_threat,
|
|
|
483 "ask-user-about-supersession-threat");
|
|
|
484 defsymbol (&Qask_user_about_lock, "ask-user-about-lock");
|
|
|
485 }
|
|
|
486
|
|
|
487
|
|
373
|
488 #endif /* CLASH_DETECTION */
|
