Commit | Line | Data |
---|---|---|
b97771fc RS |
1 | /* Lock files for editing. |
2 | Copyright (C) 1985, 86, 87, 93, 94, 96, 98, 1999 Free Software Foundation, Inc. | |
8489eb67 RS |
3 | |
4 | This file is part of GNU Emacs. | |
5 | ||
6 | GNU Emacs is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
32676c08 | 8 | the Free Software Foundation; either version 2, or (at your option) |
8489eb67 RS |
9 | any later version. |
10 | ||
11 | GNU Emacs is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with GNU Emacs; see the file COPYING. If not, write to | |
3b7ad313 EN |
18 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
19 | Boston, MA 02111-1307, USA. */ | |
8489eb67 RS |
20 | |
21 | ||
68c45bf0 | 22 | #include <config.h> |
8489eb67 RS |
23 | #include <sys/types.h> |
24 | #include <sys/stat.h> | |
dfcf069d | 25 | #include <signal.h> |
2decc5a9 | 26 | #include <stdio.h> |
bfb61299 JB |
27 | |
28 | #ifdef VMS | |
b350a838 | 29 | #include "vms-pwd.h" |
bfb61299 | 30 | #else |
8489eb67 | 31 | #include <pwd.h> |
8dbbc384 | 32 | #endif /* not VMS */ |
bfb61299 | 33 | |
8489eb67 | 34 | #include <sys/file.h> |
e5ef3cdf | 35 | #ifdef HAVE_FCNTL_H |
8489eb67 | 36 | #include <fcntl.h> |
e5ef3cdf DL |
37 | #endif |
38 | #ifdef HAVE_STRING_H | |
8dbbc384 | 39 | #include <string.h> |
e5ef3cdf | 40 | #endif |
8489eb67 | 41 | |
dfcf069d AS |
42 | #ifdef HAVE_UNISTD_H |
43 | #include <unistd.h> | |
44 | #endif | |
45 | ||
f805a125 | 46 | #ifdef __FreeBSD__ |
f805a125 KH |
47 | #include <sys/sysctl.h> |
48 | #endif /* __FreeBSD__ */ | |
49 | ||
e5ef3cdf DL |
50 | #include <errno.h> |
51 | #ifndef errno | |
52 | extern int errno; | |
53 | #endif | |
54 | ||
8489eb67 | 55 | #include "lisp.h" |
8489eb67 | 56 | #include "buffer.h" |
f4a4528d RS |
57 | #include "charset.h" |
58 | #include "coding.h" | |
9177d978 | 59 | #include "systime.h" |
8489eb67 | 60 | |
5f8d6a10 RS |
61 | /* The directory for writing temporary files. */ |
62 | ||
63 | Lisp_Object Vtemporary_file_directory; | |
64 | ||
8489eb67 | 65 | #ifdef CLASH_DETECTION |
e788eecc KH |
66 | |
67 | #include <utmp.h> | |
77e544a4 | 68 | |
a48de9b2 PE |
69 | /* A file whose last-modified time is just after the most recent boot. |
70 | Define this to be NULL to disable checking for this file. */ | |
71 | #ifndef BOOT_TIME_FILE | |
72 | #define BOOT_TIME_FILE "/var/run/random-seed" | |
73 | #endif | |
74 | ||
77e544a4 RS |
75 | #ifndef WTMP_FILE |
76 | #define WTMP_FILE "/var/log/wtmp" | |
77 | #endif | |
8489eb67 | 78 | |
8dbbc384 RS |
79 | /* The strategy: to lock a file FN, create a symlink .#FN in FN's |
80 | directory, with link data `user@host.pid'. This avoids a single | |
81 | mount (== failure) point for lock files. | |
82 | ||
83 | When the host in the lock data is the current host, we can check if | |
84 | the pid is valid with kill. | |
85 | ||
86 | Otherwise, we could look at a separate file that maps hostnames to | |
87 | reboot times to see if the remote pid can possibly be valid, since we | |
88 | don't want Emacs to have to communicate via pipes or sockets or | |
89 | whatever to other processes, either locally or remotely; rms says | |
90 | that's too unreliable. Hence the separate file, which could | |
91 | theoretically be updated by daemons running separately -- but this | |
92 | whole idea is unimplemented; in practice, at least in our | |
1c4f857c | 93 | environment, it seems such stale locks arise fairly infrequently, and |
8dbbc384 RS |
94 | Emacs' standard methods of dealing with clashes suffice. |
95 | ||
96 | We use symlinks instead of normal files because (1) they can be | |
97 | stored more efficiently on the filesystem, since the kernel knows | |
98 | they will be small, and (2) all the info about the lock can be read | |
99 | in a single system call (readlink). Although we could use regular | |
1c4f857c | 100 | files to be useful on old systems lacking symlinks, nowadays |
8dbbc384 RS |
101 | virtually all such systems are probably single-user anyway, so it |
102 | didn't seem worth the complication. | |
103 | ||
104 | Similarly, we don't worry about a possible 14-character limit on | |
105 | file names, because those are all the same systems that don't have | |
106 | symlinks. | |
107 | ||
108 | This is compatible with the locking scheme used by Interleaf (which | |
109 | has contributed this implementation for Emacs), and was designed by | |
110 | Ethan Jacobson, Kimbo Mundy, and others. | |
111 | ||
112 | --karl@cs.umb.edu/karl@hq.ileaf.com. */ | |
8489eb67 | 113 | |
8dbbc384 | 114 | \f |
15e88d21 RS |
115 | /* Return the time of the last system boot. */ |
116 | ||
117 | static time_t boot_time; | |
b97771fc | 118 | static int boot_time_initialized; |
15e88d21 | 119 | |
9177d978 RS |
120 | extern Lisp_Object Vshell_file_name; |
121 | ||
2f2500ef DL |
122 | #ifdef BOOT_TIME |
123 | static void get_boot_time_1 P_ ((char *, int)); | |
124 | #endif | |
125 | ||
15e88d21 RS |
126 | static time_t |
127 | get_boot_time () | |
128 | { | |
2decc5a9 | 129 | #if defined (BOOT_TIME) && ! defined (NO_WTMP_FILE) |
9177d978 | 130 | int counter; |
2decc5a9 | 131 | #endif |
15e88d21 | 132 | |
b97771fc | 133 | if (boot_time_initialized) |
15e88d21 | 134 | return boot_time; |
b97771fc | 135 | boot_time_initialized = 1; |
15e88d21 | 136 | |
f805a125 KH |
137 | #if defined (CTL_KERN) && defined (KERN_BOOTTIME) |
138 | { | |
139 | int mib[2]; | |
140 | size_t size; | |
141 | struct timeval boottime_val; | |
142 | ||
143 | mib[0] = CTL_KERN; | |
144 | mib[1] = KERN_BOOTTIME; | |
145 | size = sizeof (boottime_val); | |
146 | ||
147 | if (sysctl (mib, 2, &boottime_val, &size, NULL, 0) >= 0) | |
148 | { | |
149 | boot_time = boottime_val.tv_sec; | |
150 | return boot_time; | |
151 | } | |
152 | } | |
153 | #endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */ | |
9177d978 | 154 | |
a48de9b2 PE |
155 | if (BOOT_TIME_FILE) |
156 | { | |
157 | struct stat st; | |
158 | if (stat (BOOT_TIME_FILE, &st) == 0) | |
159 | { | |
160 | boot_time = st.st_mtime; | |
161 | return boot_time; | |
162 | } | |
163 | } | |
164 | ||
c6fd1dc4 | 165 | #if defined (BOOT_TIME) && ! defined (NO_WTMP_FILE) |
b97771fc RS |
166 | #ifndef CANNOT_DUMP |
167 | /* The utmp routines maintain static state. | |
168 | Don't touch that state unless we are initialized, | |
169 | since it might not survive dumping. */ | |
170 | if (! initialized) | |
171 | return boot_time; | |
172 | #endif /* not CANNOT_DUMP */ | |
173 | ||
174 | /* Try to get boot time from utmp before wtmp, | |
175 | since utmp is typically much smaller than wtmp. | |
176 | Passing a null pointer causes get_boot_time_1 | |
177 | to inspect the default file, namely utmp. */ | |
178 | get_boot_time_1 ((char *) 0, 0); | |
179 | if (boot_time) | |
180 | return boot_time; | |
181 | ||
9177d978 | 182 | /* Try to get boot time from the current wtmp file. */ |
b97771fc | 183 | get_boot_time_1 (WTMP_FILE, 1); |
9177d978 RS |
184 | |
185 | /* If we did not find a boot time in wtmp, look at wtmp, and so on. */ | |
b97771fc | 186 | for (counter = 0; counter < 20 && ! boot_time; counter++) |
9177d978 RS |
187 | { |
188 | char cmd_string[100]; | |
189 | Lisp_Object tempname, filename; | |
190 | int delete_flag = 0; | |
191 | ||
192 | filename = Qnil; | |
193 | ||
77e544a4 | 194 | sprintf (cmd_string, "%s.%d", WTMP_FILE, counter); |
9177d978 | 195 | tempname = build_string (cmd_string); |
29a2adb0 | 196 | if (! NILP (Ffile_exists_p (tempname))) |
9177d978 RS |
197 | filename = tempname; |
198 | else | |
199 | { | |
77e544a4 | 200 | sprintf (cmd_string, "%s.%d.gz", WTMP_FILE, counter); |
9177d978 RS |
201 | tempname = build_string (cmd_string); |
202 | if (! NILP (Ffile_exists_p (tempname))) | |
203 | { | |
204 | Lisp_Object args[6]; | |
f1d367aa GM |
205 | |
206 | /* The utmp functions on mescaline.gnu.org accept only | |
207 | file names up to 8 characters long. Choose a 2 | |
208 | character long prefix, and call make_temp_file with | |
209 | second arg non-zero, so that it will add not more | |
210 | than 6 characters to the prefix. */ | |
211 | tempname = Fexpand_file_name (build_string ("wt"), | |
5f8d6a10 | 212 | Vtemporary_file_directory); |
f1d367aa | 213 | tempname = make_temp_name (tempname, 1); |
9177d978 RS |
214 | args[0] = Vshell_file_name; |
215 | args[1] = Qnil; | |
216 | args[2] = Qnil; | |
217 | args[3] = Qnil; | |
218 | args[4] = build_string ("-c"); | |
77e544a4 RS |
219 | sprintf (cmd_string, "gunzip < %s.%d.gz > %s", |
220 | WTMP_FILE, counter, XSTRING (tempname)->data); | |
9177d978 RS |
221 | args[5] = build_string (cmd_string); |
222 | Fcall_process (6, args); | |
223 | filename = tempname; | |
224 | delete_flag = 1; | |
225 | } | |
226 | } | |
227 | ||
228 | if (! NILP (filename)) | |
229 | { | |
b97771fc | 230 | get_boot_time_1 (XSTRING (filename)->data, 1); |
9177d978 RS |
231 | if (delete_flag) |
232 | unlink (XSTRING (filename)->data); | |
233 | } | |
234 | } | |
235 | ||
236 | return boot_time; | |
237 | #else | |
238 | return 0; | |
239 | #endif | |
240 | } | |
241 | ||
e9f22ced | 242 | #ifdef BOOT_TIME |
9177d978 RS |
243 | /* Try to get the boot time from wtmp file FILENAME. |
244 | This succeeds if that file contains a reboot record. | |
9177d978 | 245 | |
b97771fc RS |
246 | If FILENAME is zero, use the same file as before; |
247 | if no FILENAME has ever been specified, this is the utmp file. | |
248 | Use the newest reboot record if NEWEST is nonzero, | |
249 | the first reboot record otherwise. | |
250 | Ignore all reboot records on or before BOOT_TIME. | |
251 | Success is indicated by setting BOOT_TIME to a larger value. */ | |
252 | ||
2f2500ef | 253 | void |
b97771fc | 254 | get_boot_time_1 (filename, newest) |
9177d978 | 255 | char *filename; |
b97771fc | 256 | int newest; |
9177d978 RS |
257 | { |
258 | struct utmp ut, *utp; | |
77e544a4 RS |
259 | int desc; |
260 | ||
b97771fc RS |
261 | if (filename) |
262 | { | |
263 | /* On some versions of IRIX, opening a nonexistent file name | |
264 | is likely to crash in the utmp routines. */ | |
68c45bf0 | 265 | desc = emacs_open (filename, O_RDONLY, 0); |
b97771fc RS |
266 | if (desc < 0) |
267 | return; | |
268 | ||
68c45bf0 | 269 | emacs_close (desc); |
b97771fc RS |
270 | |
271 | utmpname (filename); | |
272 | } | |
9177d978 | 273 | |
c321b190 | 274 | setutent (); |
b97771fc | 275 | |
c321b190 RS |
276 | while (1) |
277 | { | |
278 | /* Find the next reboot record. */ | |
279 | ut.ut_type = BOOT_TIME; | |
280 | utp = getutid (&ut); | |
281 | if (! utp) | |
282 | break; | |
283 | /* Compare reboot times and use the newest one. */ | |
284 | if (utp->ut_time > boot_time) | |
b97771fc RS |
285 | { |
286 | boot_time = utp->ut_time; | |
287 | if (! newest) | |
288 | break; | |
289 | } | |
c321b190 RS |
290 | /* Advance on element in the file |
291 | so that getutid won't repeat the same one. */ | |
292 | utp = getutent (); | |
293 | if (! utp) | |
294 | break; | |
295 | } | |
15e88d21 | 296 | endutent (); |
15e88d21 | 297 | } |
e9f22ced | 298 | #endif /* BOOT_TIME */ |
15e88d21 | 299 | \f |
8dbbc384 | 300 | /* Here is the structure that stores information about a lock. */ |
32676c08 | 301 | |
8dbbc384 RS |
302 | typedef struct |
303 | { | |
304 | char *user; | |
305 | char *host; | |
9005cb4f | 306 | unsigned long pid; |
15e88d21 | 307 | time_t boot_time; |
8dbbc384 | 308 | } lock_info_type; |
32676c08 | 309 | |
49b6d120 RS |
310 | /* When we read the info back, we might need this much more, |
311 | enough for decimal representation plus null. */ | |
312 | #define LOCK_PID_MAX (4 * sizeof (unsigned long)) | |
32676c08 | 313 | |
8dbbc384 RS |
314 | /* Free the two dynamically-allocated pieces in PTR. */ |
315 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 316 | |
e31fbc7a | 317 | |
8dbbc384 | 318 | /* Write the name of the lock file for FN into LFNAME. Length will be |
c1355e1f GM |
319 | that of FN plus two more for the leading `.#' plus 1 for the |
320 | trailing period plus one for the digit after it plus one for the | |
321 | null. */ | |
7b92975f | 322 | #define MAKE_LOCK_NAME(lock, file) \ |
c1355e1f | 323 | (lock = (char *) alloca (STRING_BYTES (XSTRING (file)) + 2 + 1 + 1 + 1), \ |
8dbbc384 | 324 | fill_in_lock_file_name (lock, (file))) |
e31fbc7a | 325 | |
8dbbc384 RS |
326 | static void |
327 | fill_in_lock_file_name (lockfile, fn) | |
e31fbc7a RS |
328 | register char *lockfile; |
329 | register Lisp_Object fn; | |
330 | { | |
8dbbc384 | 331 | register char *p; |
c1355e1f GM |
332 | struct stat st; |
333 | int count = 0; | |
8dbbc384 RS |
334 | |
335 | strcpy (lockfile, XSTRING (fn)->data); | |
336 | ||
337 | /* Shift the nondirectory part of the file name (including the null) | |
338 | right two characters. Here is one of the places where we'd have to | |
339 | do something to support 14-character-max file names. */ | |
340 | for (p = lockfile + strlen (lockfile); p != lockfile && *p != '/'; p--) | |
341 | p[2] = *p; | |
e31fbc7a | 342 | |
8dbbc384 RS |
343 | /* Insert the `.#'. */ |
344 | p[1] = '.'; | |
345 | p[2] = '#'; | |
c1355e1f GM |
346 | |
347 | p = p + strlen (p); | |
348 | ||
349 | while (lstat (lockfile, &st) == 0 && !S_ISLNK (st.st_mode)) | |
350 | { | |
351 | if (count > 9) | |
352 | { | |
353 | *p = '\0'; | |
354 | return; | |
355 | } | |
356 | sprintf (p, ".%d", count++); | |
357 | } | |
8dbbc384 | 358 | } |
e31fbc7a | 359 | |
8dbbc384 RS |
360 | /* Lock the lock file named LFNAME. |
361 | If FORCE is nonzero, we do so even if it is already locked. | |
362 | Return 1 if successful, 0 if not. */ | |
e31fbc7a | 363 | |
8dbbc384 RS |
364 | static int |
365 | lock_file_1 (lfname, force) | |
366 | char *lfname; | |
367 | int force; | |
368 | { | |
369 | register int err; | |
bd26d5a3 | 370 | time_t boot_time; |
662c2ef2 RS |
371 | char *user_name; |
372 | char *host_name; | |
373 | char *lock_info_str; | |
374 | ||
375 | if (STRINGP (Fuser_login_name (Qnil))) | |
266d7a00 | 376 | user_name = (char *)XSTRING (Fuser_login_name (Qnil))->data; |
662c2ef2 RS |
377 | else |
378 | user_name = ""; | |
379 | if (STRINGP (Fsystem_name ())) | |
266d7a00 | 380 | host_name = (char *)XSTRING (Fsystem_name ())->data; |
662c2ef2 RS |
381 | else |
382 | host_name = ""; | |
266d7a00 | 383 | lock_info_str = (char *)alloca (strlen (user_name) + strlen (host_name) |
15e88d21 | 384 | + LOCK_PID_MAX + 5); |
8dbbc384 | 385 | |
bd26d5a3 RS |
386 | boot_time = get_boot_time (); |
387 | if (boot_time) | |
388 | sprintf (lock_info_str, "%s@%s.%lu:%lu", user_name, host_name, | |
389 | (unsigned long) getpid (), (unsigned long) boot_time); | |
390 | else | |
391 | sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name, | |
392 | (unsigned long) getpid ()); | |
8dbbc384 RS |
393 | |
394 | err = symlink (lock_info_str, lfname); | |
395 | if (errno == EEXIST && force) | |
e31fbc7a | 396 | { |
8dbbc384 RS |
397 | unlink (lfname); |
398 | err = symlink (lock_info_str, lfname); | |
e31fbc7a | 399 | } |
e31fbc7a | 400 | |
8dbbc384 RS |
401 | return err == 0; |
402 | } | |
e31fbc7a | 403 | |
9177d978 | 404 | /* Return 1 if times A and B are no more than one second apart. */ |
32676c08 | 405 | |
9177d978 RS |
406 | int |
407 | within_one_second (a, b) | |
408 | time_t a, b; | |
409 | { | |
410 | return (a - b >= -1 && a - b <= 1); | |
411 | } | |
8dbbc384 RS |
412 | \f |
413 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, | |
414 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
415 | 2 if the current process owns it, | |
416 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 417 | |
8dbbc384 RS |
418 | static int |
419 | current_lock_owner (owner, lfname) | |
420 | lock_info_type *owner; | |
421 | char *lfname; | |
32676c08 | 422 | { |
8dbbc384 RS |
423 | #ifndef index |
424 | extern char *rindex (), *index (); | |
425 | #endif | |
5f8d6a10 | 426 | int len, ret; |
8dbbc384 | 427 | int local_owner = 0; |
15e88d21 | 428 | char *at, *dot, *colon; |
8dbbc384 RS |
429 | char *lfinfo = 0; |
430 | int bufsize = 50; | |
431 | /* Read arbitrarily-long contents of symlink. Similar code in | |
432 | file-symlink-p in fileio.c. */ | |
433 | do | |
434 | { | |
435 | bufsize *= 2; | |
436 | lfinfo = (char *) xrealloc (lfinfo, bufsize); | |
437 | len = readlink (lfname, lfinfo, bufsize); | |
438 | } | |
439 | while (len >= bufsize); | |
440 | ||
441 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ | |
442 | if (len == -1) | |
443 | { | |
444 | xfree (lfinfo); | |
445 | return errno == ENOENT ? 0 : -1; | |
446 | } | |
32676c08 | 447 | |
8dbbc384 RS |
448 | /* Link info exists, so `len' is its length. Null terminate. */ |
449 | lfinfo[len] = 0; | |
450 | ||
451 | /* Even if the caller doesn't want the owner info, we still have to | |
452 | read it to determine return value, so allocate it. */ | |
453 | if (!owner) | |
454 | { | |
3609a53b | 455 | owner = (lock_info_type *) alloca (sizeof (lock_info_type)); |
8dbbc384 RS |
456 | local_owner = 1; |
457 | } | |
458 | ||
15e88d21 | 459 | /* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */ |
8dbbc384 RS |
460 | /* The USER is everything before the first @. */ |
461 | at = index (lfinfo, '@'); | |
462 | dot = rindex (lfinfo, '.'); | |
15e88d21 RS |
463 | if (!at || !dot) |
464 | { | |
465 | xfree (lfinfo); | |
466 | return -1; | |
467 | } | |
8dbbc384 RS |
468 | len = at - lfinfo; |
469 | owner->user = (char *) xmalloc (len + 1); | |
470 | strncpy (owner->user, lfinfo, len); | |
471 | owner->user[len] = 0; | |
472 | ||
15e88d21 | 473 | /* The PID is everything from the last `.' to the `:'. */ |
8dbbc384 | 474 | owner->pid = atoi (dot + 1); |
15e88d21 RS |
475 | colon = dot; |
476 | while (*colon && *colon != ':') | |
477 | colon++; | |
478 | /* After the `:', if there is one, comes the boot time. */ | |
479 | if (*colon == ':') | |
480 | owner->boot_time = atoi (colon + 1); | |
481 | else | |
482 | owner->boot_time = 0; | |
32676c08 | 483 | |
8dbbc384 RS |
484 | /* The host is everything in between. */ |
485 | len = dot - at - 1; | |
486 | owner->host = (char *) xmalloc (len + 1); | |
487 | strncpy (owner->host, at + 1, len); | |
488 | owner->host[len] = 0; | |
32676c08 | 489 | |
8dbbc384 RS |
490 | /* We're done looking at the link info. */ |
491 | xfree (lfinfo); | |
492 | ||
493 | /* On current host? */ | |
662c2ef2 RS |
494 | if (STRINGP (Fsystem_name ()) |
495 | && strcmp (owner->host, XSTRING (Fsystem_name ())->data) == 0) | |
32676c08 | 496 | { |
8dbbc384 RS |
497 | if (owner->pid == getpid ()) |
498 | ret = 2; /* We own it. */ | |
72dcef0e | 499 | else if (owner->pid > 0 |
15e88d21 RS |
500 | && (kill (owner->pid, 0) >= 0 || errno == EPERM) |
501 | && (owner->boot_time == 0 | |
9177d978 | 502 | || within_one_second (owner->boot_time, get_boot_time ()))) |
8dbbc384 | 503 | ret = 1; /* An existing process on this machine owns it. */ |
8dbbc384 RS |
504 | /* The owner process is dead or has a strange pid (<=0), so try to |
505 | zap the lockfile. */ | |
72dcef0e | 506 | else if (unlink (lfname) < 0) |
8dbbc384 | 507 | ret = -1; |
72dcef0e RS |
508 | else |
509 | ret = 0; | |
32676c08 | 510 | } |
8dbbc384 RS |
511 | else |
512 | { /* If we wanted to support the check for stale locks on remote machines, | |
513 | here's where we'd do it. */ | |
514 | ret = 1; | |
515 | } | |
516 | ||
517 | /* Avoid garbage. */ | |
518 | if (local_owner || ret <= 0) | |
519 | { | |
520 | FREE_LOCK_INFO (*owner); | |
521 | } | |
522 | return ret; | |
32676c08 JB |
523 | } |
524 | ||
8dbbc384 RS |
525 | \f |
526 | /* Lock the lock named LFNAME if possible. | |
527 | Return 0 in that case. | |
528 | Return positive if some other process owns the lock, and info about | |
529 | that process in CLASHER. | |
530 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 531 | |
8dbbc384 RS |
532 | static int |
533 | lock_if_free (clasher, lfname) | |
534 | lock_info_type *clasher; | |
535 | register char *lfname; | |
536 | { | |
cfc01fa7 | 537 | while (lock_file_1 (lfname, 0) == 0) |
8dbbc384 RS |
538 | { |
539 | int locker; | |
e0e0205b | 540 | |
8dbbc384 RS |
541 | if (errno != EEXIST) |
542 | return -1; | |
543 | ||
544 | locker = current_lock_owner (clasher, lfname); | |
545 | if (locker == 2) | |
546 | { | |
547 | FREE_LOCK_INFO (*clasher); | |
548 | return 0; /* We ourselves locked it. */ | |
549 | } | |
550 | else if (locker == 1) | |
551 | return 1; /* Someone else has it. */ | |
5df0b2fa | 552 | else if (locker == -1) |
ae1ef097 | 553 | return -1; /* current_lock_owner returned strange error. */ |
8dbbc384 | 554 | |
cfc01fa7 | 555 | /* We deleted a stale lock; try again to lock the file. */ |
8dbbc384 RS |
556 | } |
557 | return 0; | |
8489eb67 RS |
558 | } |
559 | ||
8dbbc384 | 560 | /* lock_file locks file FN, |
8489eb67 RS |
561 | meaning it serves notice on the world that you intend to edit that file. |
562 | This should be done only when about to modify a file-visiting | |
563 | buffer previously unmodified. | |
8dbbc384 | 564 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
565 | as either the file is already locked, or the user has already |
566 | decided to go ahead without locking. | |
567 | ||
8dbbc384 | 568 | When this returns, either the lock is locked for us, |
8489eb67 RS |
569 | or the user has said to go ahead without locking. |
570 | ||
8dbbc384 | 571 | If the file is locked by someone else, this calls |
8489eb67 | 572 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 573 | the file name and info about the user who did the locking. |
8489eb67 RS |
574 | This function can signal an error, or return t meaning |
575 | take away the lock, or return nil meaning ignore the lock. */ | |
576 | ||
8489eb67 RS |
577 | void |
578 | lock_file (fn) | |
eb4b1c05 | 579 | Lisp_Object fn; |
8489eb67 | 580 | { |
f4a4528d | 581 | register Lisp_Object attack, orig_fn, encoded_fn; |
8dbbc384 RS |
582 | register char *lfname, *locker; |
583 | lock_info_type lock_info; | |
3edc33a4 | 584 | struct gcpro gcpro1; |
8489eb67 | 585 | |
33bae690 RS |
586 | /* Don't do locking while dumping Emacs. |
587 | Uncompressing wtmp files uses call-process, which does not work | |
588 | in an uninitialized Emacs. */ | |
589 | if (! NILP (Vpurify_flag)) | |
590 | return; | |
591 | ||
5383bc6d | 592 | orig_fn = fn; |
8af8a9ca | 593 | GCPRO1 (fn); |
1e89de84 | 594 | fn = Fexpand_file_name (fn, Qnil); |
f4a4528d | 595 | encoded_fn = ENCODE_FILE (fn); |
1e89de84 | 596 | |
8dbbc384 | 597 | /* Create the name of the lock-file for file fn */ |
f4a4528d | 598 | MAKE_LOCK_NAME (lfname, encoded_fn); |
8489eb67 | 599 | |
32676c08 JB |
600 | /* See if this file is visited and has changed on disk since it was |
601 | visited. */ | |
8489eb67 | 602 | { |
a57bc488 | 603 | register Lisp_Object subject_buf; |
3036594f | 604 | |
5383bc6d | 605 | subject_buf = get_truename_buffer (orig_fn); |
3036594f | 606 | |
265a9e55 JB |
607 | if (!NILP (subject_buf) |
608 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
609 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 | 610 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
3036594f | 611 | |
8489eb67 | 612 | } |
8af8a9ca | 613 | UNGCPRO; |
8489eb67 RS |
614 | |
615 | /* Try to lock the lock. */ | |
8dbbc384 RS |
616 | if (lock_if_free (&lock_info, lfname) <= 0) |
617 | /* Return now if we have locked it, or if lock creation failed */ | |
8489eb67 RS |
618 | return; |
619 | ||
620 | /* Else consider breaking the lock */ | |
266d7a00 RS |
621 | locker = (char *) alloca (strlen (lock_info.user) + strlen (lock_info.host) |
622 | + LOCK_PID_MAX + 9); | |
79e51eeb | 623 | sprintf (locker, "%s@%s (pid %lu)", lock_info.user, lock_info.host, |
8dbbc384 RS |
624 | lock_info.pid); |
625 | FREE_LOCK_INFO (lock_info); | |
626 | ||
627 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); | |
265a9e55 | 628 | if (!NILP (attack)) |
8489eb67 RS |
629 | /* User says take the lock */ |
630 | { | |
8dbbc384 | 631 | lock_file_1 (lfname, 1); |
8489eb67 RS |
632 | return; |
633 | } | |
634 | /* User says ignore the lock */ | |
635 | } | |
636 | ||
8489eb67 RS |
637 | void |
638 | unlock_file (fn) | |
639 | register Lisp_Object fn; | |
640 | { | |
641 | register char *lfname; | |
642 | ||
1e89de84 | 643 | fn = Fexpand_file_name (fn, Qnil); |
88eace34 | 644 | fn = ENCODE_FILE (fn); |
1e89de84 | 645 | |
7b92975f | 646 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 647 | |
8dbbc384 | 648 | if (current_lock_owner (0, lfname) == 2) |
8489eb67 | 649 | unlink (lfname); |
8489eb67 RS |
650 | } |
651 | ||
652 | void | |
653 | unlock_all_files () | |
654 | { | |
655 | register Lisp_Object tail; | |
656 | register struct buffer *b; | |
657 | ||
03699b14 | 658 | for (tail = Vbuffer_alist; GC_CONSP (tail); tail = XCDR (tail)) |
8489eb67 | 659 | { |
03699b14 | 660 | b = XBUFFER (XCDR (XCAR (tail))); |
5757b805 | 661 | if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) |
1c343051 KH |
662 | { |
663 | register char *lfname; | |
664 | ||
665 | MAKE_LOCK_NAME (lfname, b->file_truename); | |
666 | ||
667 | if (current_lock_owner (0, lfname) == 2) | |
668 | unlink (lfname); | |
669 | } | |
8489eb67 RS |
670 | } |
671 | } | |
8489eb67 RS |
672 | \f |
673 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
674 | 0, 1, 0, | |
675 | "Lock FILE, if current buffer is modified.\n\ | |
676 | FILE defaults to current buffer's visited file,\n\ | |
677 | or else nothing is done if current buffer isn't visiting a file.") | |
e9319ef2 EN |
678 | (file) |
679 | Lisp_Object file; | |
8489eb67 | 680 | { |
e9319ef2 EN |
681 | if (NILP (file)) |
682 | file = current_buffer->file_truename; | |
8489eb67 | 683 | else |
e9319ef2 | 684 | CHECK_STRING (file, 0); |
6a140159 | 685 | if (SAVE_MODIFF < MODIFF |
e9319ef2 EN |
686 | && !NILP (file)) |
687 | lock_file (file); | |
8489eb67 RS |
688 | return Qnil; |
689 | } | |
690 | ||
691 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
692 | 0, 0, 0, | |
693 | "Unlock the file visited in the current buffer,\n\ | |
694 | if it should normally be locked.") | |
695 | () | |
696 | { | |
6a140159 | 697 | if (SAVE_MODIFF < MODIFF |
5757b805 RS |
698 | && STRINGP (current_buffer->file_truename)) |
699 | unlock_file (current_buffer->file_truename); | |
8489eb67 RS |
700 | return Qnil; |
701 | } | |
702 | ||
8489eb67 RS |
703 | /* Unlock the file visited in buffer BUFFER. */ |
704 | ||
d07e0802 | 705 | void |
8489eb67 RS |
706 | unlock_buffer (buffer) |
707 | struct buffer *buffer; | |
708 | { | |
6a140159 | 709 | if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer) |
5757b805 RS |
710 | && STRINGP (buffer->file_truename)) |
711 | unlock_file (buffer->file_truename); | |
8489eb67 RS |
712 | } |
713 | ||
8105cbf7 | 714 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 1, 1, 0, |
8489eb67 RS |
715 | "Return nil if the FILENAME is not locked,\n\ |
716 | t if it is locked by you, else a string of the name of the locker.") | |
e9319ef2 EN |
717 | (filename) |
718 | Lisp_Object filename; | |
8489eb67 | 719 | { |
8dbbc384 | 720 | Lisp_Object ret; |
8489eb67 RS |
721 | register char *lfname; |
722 | int owner; | |
8dbbc384 | 723 | lock_info_type locker; |
8489eb67 | 724 | |
e9319ef2 | 725 | filename = Fexpand_file_name (filename, Qnil); |
8489eb67 | 726 | |
e9319ef2 | 727 | MAKE_LOCK_NAME (lfname, filename); |
8489eb67 | 728 | |
8dbbc384 | 729 | owner = current_lock_owner (&locker, lfname); |
8489eb67 | 730 | if (owner <= 0) |
8dbbc384 RS |
731 | ret = Qnil; |
732 | else if (owner == 2) | |
733 | ret = Qt; | |
734 | else | |
735 | ret = build_string (locker.user); | |
736 | ||
737 | if (owner > 0) | |
738 | FREE_LOCK_INFO (locker); | |
739 | ||
740 | return ret; | |
8489eb67 | 741 | } |
32676c08 JB |
742 | \f |
743 | /* Initialization functions. */ | |
744 | ||
a3fd58aa KH |
745 | void |
746 | init_filelock () | |
747 | { | |
748 | boot_time = 0; | |
b97771fc | 749 | boot_time_initialized = 0; |
a3fd58aa KH |
750 | } |
751 | ||
dfcf069d | 752 | void |
8489eb67 RS |
753 | syms_of_filelock () |
754 | { | |
5f8d6a10 RS |
755 | DEFVAR_LISP ("temporary-file-directory", &Vtemporary_file_directory, |
756 | "The directory for writing temporary files."); | |
757 | Vtemporary_file_directory = Qnil; | |
758 | ||
8489eb67 RS |
759 | defsubr (&Sunlock_buffer); |
760 | defsubr (&Slock_buffer); | |
761 | defsubr (&Sfile_locked_p); | |
762 | } | |
763 | ||
764 | #endif /* CLASH_DETECTION */ |