Commit | Line | Data |
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b97771fc | 1 | /* Lock files for editing. |
73b0cd50 | 2 | Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2011 |
8cabe764 | 3 | Free Software Foundation, Inc. |
8489eb67 RS |
4 | |
5 | This file is part of GNU Emacs. | |
6 | ||
9ec0b715 | 7 | GNU Emacs is free software: you can redistribute it and/or modify |
8489eb67 | 8 | it under the terms of the GNU General Public License as published by |
9ec0b715 GM |
9 | the Free Software Foundation, either version 3 of the License, or |
10 | (at your option) any later version. | |
8489eb67 RS |
11 | |
12 | GNU Emacs is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
9ec0b715 | 18 | along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */ |
8489eb67 RS |
19 | |
20 | ||
68c45bf0 | 21 | #include <config.h> |
8489eb67 RS |
22 | #include <sys/types.h> |
23 | #include <sys/stat.h> | |
dfcf069d | 24 | #include <signal.h> |
2decc5a9 | 25 | #include <stdio.h> |
d7306fe6 | 26 | #include <setjmp.h> |
bfb61299 | 27 | |
5b9c0a1d | 28 | #ifdef HAVE_PWD_H |
8489eb67 | 29 | #include <pwd.h> |
5b9c0a1d | 30 | #endif |
bfb61299 | 31 | |
8489eb67 | 32 | #include <sys/file.h> |
8489eb67 | 33 | #include <fcntl.h> |
dfcf069d | 34 | #include <unistd.h> |
dfcf069d | 35 | |
f805a125 | 36 | #ifdef __FreeBSD__ |
f805a125 KH |
37 | #include <sys/sysctl.h> |
38 | #endif /* __FreeBSD__ */ | |
39 | ||
e5ef3cdf | 40 | #include <errno.h> |
e5ef3cdf | 41 | |
8489eb67 | 42 | #include "lisp.h" |
8489eb67 | 43 | #include "buffer.h" |
d2f6dae8 | 44 | #include "character.h" |
f4a4528d | 45 | #include "coding.h" |
9177d978 | 46 | #include "systime.h" |
8489eb67 | 47 | |
8489eb67 | 48 | #ifdef CLASH_DETECTION |
e788eecc | 49 | |
c6d09b8d | 50 | #ifdef HAVE_UTMP_H |
e788eecc | 51 | #include <utmp.h> |
c6d09b8d | 52 | #endif |
77e544a4 | 53 | |
a48de9b2 PE |
54 | /* A file whose last-modified time is just after the most recent boot. |
55 | Define this to be NULL to disable checking for this file. */ | |
56 | #ifndef BOOT_TIME_FILE | |
57 | #define BOOT_TIME_FILE "/var/run/random-seed" | |
58 | #endif | |
59 | ||
77e544a4 RS |
60 | #ifndef WTMP_FILE |
61 | #define WTMP_FILE "/var/log/wtmp" | |
62 | #endif | |
177c0ea7 | 63 | |
8dbbc384 RS |
64 | /* The strategy: to lock a file FN, create a symlink .#FN in FN's |
65 | directory, with link data `user@host.pid'. This avoids a single | |
66 | mount (== failure) point for lock files. | |
67 | ||
68 | When the host in the lock data is the current host, we can check if | |
69 | the pid is valid with kill. | |
177c0ea7 | 70 | |
8dbbc384 RS |
71 | Otherwise, we could look at a separate file that maps hostnames to |
72 | reboot times to see if the remote pid can possibly be valid, since we | |
73 | don't want Emacs to have to communicate via pipes or sockets or | |
74 | whatever to other processes, either locally or remotely; rms says | |
75 | that's too unreliable. Hence the separate file, which could | |
76 | theoretically be updated by daemons running separately -- but this | |
77 | whole idea is unimplemented; in practice, at least in our | |
1c4f857c | 78 | environment, it seems such stale locks arise fairly infrequently, and |
8dbbc384 RS |
79 | Emacs' standard methods of dealing with clashes suffice. |
80 | ||
81 | We use symlinks instead of normal files because (1) they can be | |
82 | stored more efficiently on the filesystem, since the kernel knows | |
83 | they will be small, and (2) all the info about the lock can be read | |
84 | in a single system call (readlink). Although we could use regular | |
1c4f857c | 85 | files to be useful on old systems lacking symlinks, nowadays |
8dbbc384 RS |
86 | virtually all such systems are probably single-user anyway, so it |
87 | didn't seem worth the complication. | |
177c0ea7 | 88 | |
8dbbc384 RS |
89 | Similarly, we don't worry about a possible 14-character limit on |
90 | file names, because those are all the same systems that don't have | |
91 | symlinks. | |
177c0ea7 | 92 | |
8dbbc384 RS |
93 | This is compatible with the locking scheme used by Interleaf (which |
94 | has contributed this implementation for Emacs), and was designed by | |
95 | Ethan Jacobson, Kimbo Mundy, and others. | |
177c0ea7 | 96 | |
8dbbc384 | 97 | --karl@cs.umb.edu/karl@hq.ileaf.com. */ |
8489eb67 | 98 | |
8dbbc384 | 99 | \f |
15e88d21 RS |
100 | /* Return the time of the last system boot. */ |
101 | ||
102 | static time_t boot_time; | |
b97771fc | 103 | static int boot_time_initialized; |
15e88d21 | 104 | |
2f2500ef | 105 | #ifdef BOOT_TIME |
8ea90aa3 | 106 | static void get_boot_time_1 (const char *, int); |
2f2500ef DL |
107 | #endif |
108 | ||
15e88d21 | 109 | static time_t |
971de7fb | 110 | get_boot_time (void) |
15e88d21 | 111 | { |
9d2818d6 | 112 | #if defined (BOOT_TIME) |
9177d978 | 113 | int counter; |
2decc5a9 | 114 | #endif |
15e88d21 | 115 | |
b97771fc | 116 | if (boot_time_initialized) |
15e88d21 | 117 | return boot_time; |
b97771fc | 118 | boot_time_initialized = 1; |
15e88d21 | 119 | |
f805a125 KH |
120 | #if defined (CTL_KERN) && defined (KERN_BOOTTIME) |
121 | { | |
122 | int mib[2]; | |
123 | size_t size; | |
124 | struct timeval boottime_val; | |
125 | ||
126 | mib[0] = CTL_KERN; | |
127 | mib[1] = KERN_BOOTTIME; | |
128 | size = sizeof (boottime_val); | |
129 | ||
130 | if (sysctl (mib, 2, &boottime_val, &size, NULL, 0) >= 0) | |
131 | { | |
132 | boot_time = boottime_val.tv_sec; | |
133 | return boot_time; | |
134 | } | |
135 | } | |
136 | #endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */ | |
9177d978 | 137 | |
a48de9b2 PE |
138 | if (BOOT_TIME_FILE) |
139 | { | |
140 | struct stat st; | |
141 | if (stat (BOOT_TIME_FILE, &st) == 0) | |
142 | { | |
143 | boot_time = st.st_mtime; | |
144 | return boot_time; | |
145 | } | |
146 | } | |
147 | ||
9d2818d6 | 148 | #if defined (BOOT_TIME) |
b97771fc RS |
149 | #ifndef CANNOT_DUMP |
150 | /* The utmp routines maintain static state. | |
151 | Don't touch that state unless we are initialized, | |
152 | since it might not survive dumping. */ | |
153 | if (! initialized) | |
154 | return boot_time; | |
155 | #endif /* not CANNOT_DUMP */ | |
156 | ||
157 | /* Try to get boot time from utmp before wtmp, | |
158 | since utmp is typically much smaller than wtmp. | |
159 | Passing a null pointer causes get_boot_time_1 | |
160 | to inspect the default file, namely utmp. */ | |
161 | get_boot_time_1 ((char *) 0, 0); | |
162 | if (boot_time) | |
163 | return boot_time; | |
164 | ||
9177d978 | 165 | /* Try to get boot time from the current wtmp file. */ |
b97771fc | 166 | get_boot_time_1 (WTMP_FILE, 1); |
9177d978 RS |
167 | |
168 | /* If we did not find a boot time in wtmp, look at wtmp, and so on. */ | |
b97771fc | 169 | for (counter = 0; counter < 20 && ! boot_time; counter++) |
9177d978 RS |
170 | { |
171 | char cmd_string[100]; | |
172 | Lisp_Object tempname, filename; | |
173 | int delete_flag = 0; | |
174 | ||
175 | filename = Qnil; | |
176 | ||
77e544a4 | 177 | sprintf (cmd_string, "%s.%d", WTMP_FILE, counter); |
9177d978 | 178 | tempname = build_string (cmd_string); |
29a2adb0 | 179 | if (! NILP (Ffile_exists_p (tempname))) |
9177d978 RS |
180 | filename = tempname; |
181 | else | |
182 | { | |
77e544a4 | 183 | sprintf (cmd_string, "%s.%d.gz", WTMP_FILE, counter); |
9177d978 RS |
184 | tempname = build_string (cmd_string); |
185 | if (! NILP (Ffile_exists_p (tempname))) | |
186 | { | |
187 | Lisp_Object args[6]; | |
f1d367aa GM |
188 | |
189 | /* The utmp functions on mescaline.gnu.org accept only | |
190 | file names up to 8 characters long. Choose a 2 | |
191 | character long prefix, and call make_temp_file with | |
192 | second arg non-zero, so that it will add not more | |
193 | than 6 characters to the prefix. */ | |
194 | tempname = Fexpand_file_name (build_string ("wt"), | |
5f8d6a10 | 195 | Vtemporary_file_directory); |
f1d367aa | 196 | tempname = make_temp_name (tempname, 1); |
9177d978 RS |
197 | args[0] = Vshell_file_name; |
198 | args[1] = Qnil; | |
199 | args[2] = Qnil; | |
200 | args[3] = Qnil; | |
201 | args[4] = build_string ("-c"); | |
77e544a4 | 202 | sprintf (cmd_string, "gunzip < %s.%d.gz > %s", |
d5db4077 | 203 | WTMP_FILE, counter, SDATA (tempname)); |
9177d978 RS |
204 | args[5] = build_string (cmd_string); |
205 | Fcall_process (6, args); | |
206 | filename = tempname; | |
207 | delete_flag = 1; | |
208 | } | |
209 | } | |
210 | ||
211 | if (! NILP (filename)) | |
212 | { | |
42a5b22f | 213 | get_boot_time_1 (SSDATA (filename), 1); |
9177d978 | 214 | if (delete_flag) |
42a5b22f | 215 | unlink (SSDATA (filename)); |
9177d978 RS |
216 | } |
217 | } | |
218 | ||
219 | return boot_time; | |
220 | #else | |
221 | return 0; | |
222 | #endif | |
223 | } | |
224 | ||
e9f22ced | 225 | #ifdef BOOT_TIME |
9177d978 RS |
226 | /* Try to get the boot time from wtmp file FILENAME. |
227 | This succeeds if that file contains a reboot record. | |
9177d978 | 228 | |
b97771fc RS |
229 | If FILENAME is zero, use the same file as before; |
230 | if no FILENAME has ever been specified, this is the utmp file. | |
231 | Use the newest reboot record if NEWEST is nonzero, | |
232 | the first reboot record otherwise. | |
233 | Ignore all reboot records on or before BOOT_TIME. | |
234 | Success is indicated by setting BOOT_TIME to a larger value. */ | |
235 | ||
2f2500ef | 236 | void |
8ea90aa3 | 237 | get_boot_time_1 (const char *filename, int newest) |
9177d978 RS |
238 | { |
239 | struct utmp ut, *utp; | |
77e544a4 RS |
240 | int desc; |
241 | ||
b97771fc RS |
242 | if (filename) |
243 | { | |
244 | /* On some versions of IRIX, opening a nonexistent file name | |
245 | is likely to crash in the utmp routines. */ | |
68c45bf0 | 246 | desc = emacs_open (filename, O_RDONLY, 0); |
b97771fc RS |
247 | if (desc < 0) |
248 | return; | |
249 | ||
68c45bf0 | 250 | emacs_close (desc); |
b97771fc RS |
251 | |
252 | utmpname (filename); | |
253 | } | |
9177d978 | 254 | |
c321b190 | 255 | setutent (); |
b97771fc | 256 | |
c321b190 RS |
257 | while (1) |
258 | { | |
259 | /* Find the next reboot record. */ | |
260 | ut.ut_type = BOOT_TIME; | |
261 | utp = getutid (&ut); | |
262 | if (! utp) | |
263 | break; | |
264 | /* Compare reboot times and use the newest one. */ | |
265 | if (utp->ut_time > boot_time) | |
b97771fc RS |
266 | { |
267 | boot_time = utp->ut_time; | |
268 | if (! newest) | |
269 | break; | |
270 | } | |
c321b190 RS |
271 | /* Advance on element in the file |
272 | so that getutid won't repeat the same one. */ | |
273 | utp = getutent (); | |
274 | if (! utp) | |
275 | break; | |
276 | } | |
15e88d21 | 277 | endutent (); |
15e88d21 | 278 | } |
e9f22ced | 279 | #endif /* BOOT_TIME */ |
15e88d21 | 280 | \f |
8dbbc384 | 281 | /* Here is the structure that stores information about a lock. */ |
32676c08 | 282 | |
8dbbc384 RS |
283 | typedef struct |
284 | { | |
285 | char *user; | |
286 | char *host; | |
9005cb4f | 287 | unsigned long pid; |
15e88d21 | 288 | time_t boot_time; |
8dbbc384 | 289 | } lock_info_type; |
32676c08 | 290 | |
49b6d120 RS |
291 | /* When we read the info back, we might need this much more, |
292 | enough for decimal representation plus null. */ | |
293 | #define LOCK_PID_MAX (4 * sizeof (unsigned long)) | |
32676c08 | 294 | |
8dbbc384 RS |
295 | /* Free the two dynamically-allocated pieces in PTR. */ |
296 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 297 | |
e31fbc7a | 298 | |
8dbbc384 | 299 | /* Write the name of the lock file for FN into LFNAME. Length will be |
c1355e1f GM |
300 | that of FN plus two more for the leading `.#' plus 1 for the |
301 | trailing period plus one for the digit after it plus one for the | |
302 | null. */ | |
7b92975f | 303 | #define MAKE_LOCK_NAME(lock, file) \ |
d5db4077 | 304 | (lock = (char *) alloca (SBYTES (file) + 2 + 1 + 1 + 1), \ |
8dbbc384 | 305 | fill_in_lock_file_name (lock, (file))) |
e31fbc7a | 306 | |
8dbbc384 | 307 | static void |
971de7fb | 308 | fill_in_lock_file_name (register char *lockfile, register Lisp_Object fn) |
e31fbc7a | 309 | { |
8dbbc384 | 310 | register char *p; |
c1355e1f GM |
311 | struct stat st; |
312 | int count = 0; | |
8dbbc384 | 313 | |
42a5b22f | 314 | strcpy (lockfile, SSDATA (fn)); |
8dbbc384 RS |
315 | |
316 | /* Shift the nondirectory part of the file name (including the null) | |
317 | right two characters. Here is one of the places where we'd have to | |
318 | do something to support 14-character-max file names. */ | |
319 | for (p = lockfile + strlen (lockfile); p != lockfile && *p != '/'; p--) | |
320 | p[2] = *p; | |
177c0ea7 | 321 | |
8dbbc384 RS |
322 | /* Insert the `.#'. */ |
323 | p[1] = '.'; | |
324 | p[2] = '#'; | |
c1355e1f GM |
325 | |
326 | p = p + strlen (p); | |
327 | ||
328 | while (lstat (lockfile, &st) == 0 && !S_ISLNK (st.st_mode)) | |
329 | { | |
330 | if (count > 9) | |
331 | { | |
332 | *p = '\0'; | |
333 | return; | |
334 | } | |
335 | sprintf (p, ".%d", count++); | |
336 | } | |
8dbbc384 | 337 | } |
e31fbc7a | 338 | |
8dbbc384 RS |
339 | /* Lock the lock file named LFNAME. |
340 | If FORCE is nonzero, we do so even if it is already locked. | |
341 | Return 1 if successful, 0 if not. */ | |
e31fbc7a | 342 | |
8dbbc384 | 343 | static int |
971de7fb | 344 | lock_file_1 (char *lfname, int force) |
8dbbc384 RS |
345 | { |
346 | register int err; | |
bd26d5a3 | 347 | time_t boot_time; |
8ea90aa3 DN |
348 | const char *user_name; |
349 | const char *host_name; | |
662c2ef2 RS |
350 | char *lock_info_str; |
351 | ||
4ba93ac0 AS |
352 | /* Call this first because it can GC. */ |
353 | boot_time = get_boot_time (); | |
354 | ||
662c2ef2 | 355 | if (STRINGP (Fuser_login_name (Qnil))) |
51b59d79 | 356 | user_name = SSDATA (Fuser_login_name (Qnil)); |
662c2ef2 RS |
357 | else |
358 | user_name = ""; | |
359 | if (STRINGP (Fsystem_name ())) | |
51b59d79 | 360 | host_name = SSDATA (Fsystem_name ()); |
662c2ef2 RS |
361 | else |
362 | host_name = ""; | |
266d7a00 | 363 | lock_info_str = (char *)alloca (strlen (user_name) + strlen (host_name) |
4ba93ac0 | 364 | + LOCK_PID_MAX + 30); |
8dbbc384 | 365 | |
bd26d5a3 RS |
366 | if (boot_time) |
367 | sprintf (lock_info_str, "%s@%s.%lu:%lu", user_name, host_name, | |
368 | (unsigned long) getpid (), (unsigned long) boot_time); | |
369 | else | |
370 | sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name, | |
177c0ea7 | 371 | (unsigned long) getpid ()); |
8dbbc384 RS |
372 | |
373 | err = symlink (lock_info_str, lfname); | |
374 | if (errno == EEXIST && force) | |
e31fbc7a | 375 | { |
8dbbc384 RS |
376 | unlink (lfname); |
377 | err = symlink (lock_info_str, lfname); | |
e31fbc7a | 378 | } |
e31fbc7a | 379 | |
8dbbc384 RS |
380 | return err == 0; |
381 | } | |
e31fbc7a | 382 | |
9177d978 | 383 | /* Return 1 if times A and B are no more than one second apart. */ |
32676c08 | 384 | |
9177d978 | 385 | int |
971de7fb | 386 | within_one_second (time_t a, time_t b) |
9177d978 RS |
387 | { |
388 | return (a - b >= -1 && a - b <= 1); | |
389 | } | |
8dbbc384 RS |
390 | \f |
391 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, | |
392 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
393 | 2 if the current process owns it, | |
394 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 395 | |
8dbbc384 | 396 | static int |
971de7fb | 397 | current_lock_owner (lock_info_type *owner, char *lfname) |
32676c08 | 398 | { |
5f8d6a10 | 399 | int len, ret; |
8dbbc384 | 400 | int local_owner = 0; |
15e88d21 | 401 | char *at, *dot, *colon; |
8dbbc384 RS |
402 | char *lfinfo = 0; |
403 | int bufsize = 50; | |
404 | /* Read arbitrarily-long contents of symlink. Similar code in | |
405 | file-symlink-p in fileio.c. */ | |
406 | do | |
407 | { | |
408 | bufsize *= 2; | |
409 | lfinfo = (char *) xrealloc (lfinfo, bufsize); | |
620c4704 | 410 | errno = 0; |
8dbbc384 | 411 | len = readlink (lfname, lfinfo, bufsize); |
b6e97b0a GM |
412 | #ifdef ERANGE |
413 | /* HP-UX reports ERANGE if the buffer is too small. */ | |
414 | if (len == -1 && errno == ERANGE) | |
63680feb | 415 | len = bufsize; |
b6e97b0a | 416 | #endif |
8dbbc384 RS |
417 | } |
418 | while (len >= bufsize); | |
177c0ea7 | 419 | |
8dbbc384 RS |
420 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ |
421 | if (len == -1) | |
422 | { | |
423 | xfree (lfinfo); | |
424 | return errno == ENOENT ? 0 : -1; | |
425 | } | |
32676c08 | 426 | |
8dbbc384 RS |
427 | /* Link info exists, so `len' is its length. Null terminate. */ |
428 | lfinfo[len] = 0; | |
177c0ea7 | 429 | |
8dbbc384 RS |
430 | /* Even if the caller doesn't want the owner info, we still have to |
431 | read it to determine return value, so allocate it. */ | |
432 | if (!owner) | |
433 | { | |
3609a53b | 434 | owner = (lock_info_type *) alloca (sizeof (lock_info_type)); |
8dbbc384 RS |
435 | local_owner = 1; |
436 | } | |
177c0ea7 | 437 | |
15e88d21 | 438 | /* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */ |
50624218 | 439 | /* The USER is everything before the last @. */ |
8966b757 AS |
440 | at = strrchr (lfinfo, '@'); |
441 | dot = strrchr (lfinfo, '.'); | |
15e88d21 RS |
442 | if (!at || !dot) |
443 | { | |
444 | xfree (lfinfo); | |
445 | return -1; | |
446 | } | |
8dbbc384 RS |
447 | len = at - lfinfo; |
448 | owner->user = (char *) xmalloc (len + 1); | |
449 | strncpy (owner->user, lfinfo, len); | |
450 | owner->user[len] = 0; | |
177c0ea7 | 451 | |
15e88d21 | 452 | /* The PID is everything from the last `.' to the `:'. */ |
8dbbc384 | 453 | owner->pid = atoi (dot + 1); |
15e88d21 RS |
454 | colon = dot; |
455 | while (*colon && *colon != ':') | |
456 | colon++; | |
457 | /* After the `:', if there is one, comes the boot time. */ | |
458 | if (*colon == ':') | |
459 | owner->boot_time = atoi (colon + 1); | |
460 | else | |
461 | owner->boot_time = 0; | |
32676c08 | 462 | |
8dbbc384 RS |
463 | /* The host is everything in between. */ |
464 | len = dot - at - 1; | |
465 | owner->host = (char *) xmalloc (len + 1); | |
466 | strncpy (owner->host, at + 1, len); | |
467 | owner->host[len] = 0; | |
32676c08 | 468 | |
8dbbc384 RS |
469 | /* We're done looking at the link info. */ |
470 | xfree (lfinfo); | |
177c0ea7 | 471 | |
8dbbc384 | 472 | /* On current host? */ |
662c2ef2 | 473 | if (STRINGP (Fsystem_name ()) |
42a5b22f | 474 | && strcmp (owner->host, SSDATA (Fsystem_name ())) == 0) |
32676c08 | 475 | { |
8dbbc384 RS |
476 | if (owner->pid == getpid ()) |
477 | ret = 2; /* We own it. */ | |
72dcef0e | 478 | else if (owner->pid > 0 |
15e88d21 RS |
479 | && (kill (owner->pid, 0) >= 0 || errno == EPERM) |
480 | && (owner->boot_time == 0 | |
9177d978 | 481 | || within_one_second (owner->boot_time, get_boot_time ()))) |
8dbbc384 | 482 | ret = 1; /* An existing process on this machine owns it. */ |
8dbbc384 RS |
483 | /* The owner process is dead or has a strange pid (<=0), so try to |
484 | zap the lockfile. */ | |
72dcef0e | 485 | else if (unlink (lfname) < 0) |
8dbbc384 | 486 | ret = -1; |
72dcef0e RS |
487 | else |
488 | ret = 0; | |
32676c08 | 489 | } |
8dbbc384 RS |
490 | else |
491 | { /* If we wanted to support the check for stale locks on remote machines, | |
492 | here's where we'd do it. */ | |
493 | ret = 1; | |
494 | } | |
177c0ea7 | 495 | |
8dbbc384 RS |
496 | /* Avoid garbage. */ |
497 | if (local_owner || ret <= 0) | |
498 | { | |
499 | FREE_LOCK_INFO (*owner); | |
500 | } | |
501 | return ret; | |
32676c08 JB |
502 | } |
503 | ||
8dbbc384 RS |
504 | \f |
505 | /* Lock the lock named LFNAME if possible. | |
506 | Return 0 in that case. | |
507 | Return positive if some other process owns the lock, and info about | |
508 | that process in CLASHER. | |
509 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 510 | |
8dbbc384 | 511 | static int |
971de7fb | 512 | lock_if_free (lock_info_type *clasher, register char *lfname) |
8dbbc384 | 513 | { |
cfc01fa7 | 514 | while (lock_file_1 (lfname, 0) == 0) |
8dbbc384 RS |
515 | { |
516 | int locker; | |
e0e0205b | 517 | |
8dbbc384 RS |
518 | if (errno != EEXIST) |
519 | return -1; | |
177c0ea7 | 520 | |
8dbbc384 RS |
521 | locker = current_lock_owner (clasher, lfname); |
522 | if (locker == 2) | |
523 | { | |
524 | FREE_LOCK_INFO (*clasher); | |
525 | return 0; /* We ourselves locked it. */ | |
526 | } | |
527 | else if (locker == 1) | |
528 | return 1; /* Someone else has it. */ | |
5df0b2fa | 529 | else if (locker == -1) |
ae1ef097 | 530 | return -1; /* current_lock_owner returned strange error. */ |
8dbbc384 | 531 | |
cfc01fa7 | 532 | /* We deleted a stale lock; try again to lock the file. */ |
8dbbc384 RS |
533 | } |
534 | return 0; | |
8489eb67 RS |
535 | } |
536 | ||
8dbbc384 | 537 | /* lock_file locks file FN, |
8489eb67 RS |
538 | meaning it serves notice on the world that you intend to edit that file. |
539 | This should be done only when about to modify a file-visiting | |
540 | buffer previously unmodified. | |
8dbbc384 | 541 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
542 | as either the file is already locked, or the user has already |
543 | decided to go ahead without locking. | |
544 | ||
8dbbc384 | 545 | When this returns, either the lock is locked for us, |
8489eb67 RS |
546 | or the user has said to go ahead without locking. |
547 | ||
8dbbc384 | 548 | If the file is locked by someone else, this calls |
8489eb67 | 549 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 550 | the file name and info about the user who did the locking. |
8489eb67 RS |
551 | This function can signal an error, or return t meaning |
552 | take away the lock, or return nil meaning ignore the lock. */ | |
553 | ||
8489eb67 | 554 | void |
971de7fb | 555 | lock_file (Lisp_Object fn) |
8489eb67 | 556 | { |
f4a4528d | 557 | register Lisp_Object attack, orig_fn, encoded_fn; |
8dbbc384 RS |
558 | register char *lfname, *locker; |
559 | lock_info_type lock_info; | |
3edc33a4 | 560 | struct gcpro gcpro1; |
8489eb67 | 561 | |
33bae690 RS |
562 | /* Don't do locking while dumping Emacs. |
563 | Uncompressing wtmp files uses call-process, which does not work | |
564 | in an uninitialized Emacs. */ | |
565 | if (! NILP (Vpurify_flag)) | |
566 | return; | |
567 | ||
5383bc6d | 568 | orig_fn = fn; |
8af8a9ca | 569 | GCPRO1 (fn); |
1e89de84 | 570 | fn = Fexpand_file_name (fn, Qnil); |
f4a4528d | 571 | encoded_fn = ENCODE_FILE (fn); |
1e89de84 | 572 | |
8dbbc384 | 573 | /* Create the name of the lock-file for file fn */ |
f4a4528d | 574 | MAKE_LOCK_NAME (lfname, encoded_fn); |
8489eb67 | 575 | |
32676c08 JB |
576 | /* See if this file is visited and has changed on disk since it was |
577 | visited. */ | |
8489eb67 | 578 | { |
a57bc488 | 579 | register Lisp_Object subject_buf; |
3036594f | 580 | |
5383bc6d | 581 | subject_buf = get_truename_buffer (orig_fn); |
3036594f | 582 | |
265a9e55 JB |
583 | if (!NILP (subject_buf) |
584 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
585 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 | 586 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
3036594f | 587 | |
8489eb67 | 588 | } |
8af8a9ca | 589 | UNGCPRO; |
8489eb67 RS |
590 | |
591 | /* Try to lock the lock. */ | |
8dbbc384 RS |
592 | if (lock_if_free (&lock_info, lfname) <= 0) |
593 | /* Return now if we have locked it, or if lock creation failed */ | |
8489eb67 RS |
594 | return; |
595 | ||
596 | /* Else consider breaking the lock */ | |
266d7a00 RS |
597 | locker = (char *) alloca (strlen (lock_info.user) + strlen (lock_info.host) |
598 | + LOCK_PID_MAX + 9); | |
79e51eeb | 599 | sprintf (locker, "%s@%s (pid %lu)", lock_info.user, lock_info.host, |
8dbbc384 RS |
600 | lock_info.pid); |
601 | FREE_LOCK_INFO (lock_info); | |
177c0ea7 | 602 | |
8dbbc384 | 603 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); |
265a9e55 | 604 | if (!NILP (attack)) |
8489eb67 RS |
605 | /* User says take the lock */ |
606 | { | |
8dbbc384 | 607 | lock_file_1 (lfname, 1); |
8489eb67 RS |
608 | return; |
609 | } | |
610 | /* User says ignore the lock */ | |
611 | } | |
612 | ||
8489eb67 | 613 | void |
971de7fb | 614 | unlock_file (register Lisp_Object fn) |
8489eb67 RS |
615 | { |
616 | register char *lfname; | |
617 | ||
1e89de84 | 618 | fn = Fexpand_file_name (fn, Qnil); |
88eace34 | 619 | fn = ENCODE_FILE (fn); |
1e89de84 | 620 | |
7b92975f | 621 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 622 | |
8dbbc384 | 623 | if (current_lock_owner (0, lfname) == 2) |
8489eb67 | 624 | unlink (lfname); |
8489eb67 RS |
625 | } |
626 | ||
627 | void | |
971de7fb | 628 | unlock_all_files (void) |
8489eb67 RS |
629 | { |
630 | register Lisp_Object tail; | |
631 | register struct buffer *b; | |
632 | ||
8e50cc2d | 633 | for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail)) |
8489eb67 | 634 | { |
03699b14 | 635 | b = XBUFFER (XCDR (XCAR (tail))); |
4b4deea2 | 636 | if (STRINGP (BVAR (b, file_truename)) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) |
1c343051 | 637 | { |
4b4deea2 | 638 | unlock_file(BVAR (b, file_truename)); |
1c343051 | 639 | } |
8489eb67 RS |
640 | } |
641 | } | |
8489eb67 RS |
642 | \f |
643 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
335c5470 PJ |
644 | 0, 1, 0, |
645 | doc: /* Lock FILE, if current buffer is modified. | |
646 | FILE defaults to current buffer's visited file, | |
647 | or else nothing is done if current buffer isn't visiting a file. */) | |
5842a27b | 648 | (Lisp_Object file) |
8489eb67 | 649 | { |
e9319ef2 | 650 | if (NILP (file)) |
4b4deea2 | 651 | file = BVAR (current_buffer, file_truename); |
8489eb67 | 652 | else |
b7826503 | 653 | CHECK_STRING (file); |
6a140159 | 654 | if (SAVE_MODIFF < MODIFF |
e9319ef2 EN |
655 | && !NILP (file)) |
656 | lock_file (file); | |
177c0ea7 | 657 | return Qnil; |
8489eb67 RS |
658 | } |
659 | ||
660 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
335c5470 | 661 | 0, 0, 0, |
3bfb8921 RS |
662 | doc: /* Unlock the file visited in the current buffer. |
663 | If the buffer is not modified, this does nothing because the file | |
664 | should not be locked in that case. */) | |
5842a27b | 665 | (void) |
8489eb67 | 666 | { |
6a140159 | 667 | if (SAVE_MODIFF < MODIFF |
4b4deea2 TT |
668 | && STRINGP (BVAR (current_buffer, file_truename))) |
669 | unlock_file (BVAR (current_buffer, file_truename)); | |
8489eb67 RS |
670 | return Qnil; |
671 | } | |
672 | ||
8489eb67 RS |
673 | /* Unlock the file visited in buffer BUFFER. */ |
674 | ||
d07e0802 | 675 | void |
971de7fb | 676 | unlock_buffer (struct buffer *buffer) |
8489eb67 | 677 | { |
6a140159 | 678 | if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer) |
4b4deea2 TT |
679 | && STRINGP (BVAR (buffer, file_truename))) |
680 | unlock_file (BVAR (buffer, file_truename)); | |
8489eb67 RS |
681 | } |
682 | ||
8105cbf7 | 683 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 1, 1, 0, |
3bfb8921 RS |
684 | doc: /* Return a value indicating whether FILENAME is locked. |
685 | The value is nil if the FILENAME is not locked, | |
686 | t if it is locked by you, else a string saying which user has locked it. */) | |
5842a27b | 687 | (Lisp_Object filename) |
8489eb67 | 688 | { |
8dbbc384 | 689 | Lisp_Object ret; |
8489eb67 RS |
690 | register char *lfname; |
691 | int owner; | |
8dbbc384 | 692 | lock_info_type locker; |
8489eb67 | 693 | |
e9319ef2 | 694 | filename = Fexpand_file_name (filename, Qnil); |
8489eb67 | 695 | |
e9319ef2 | 696 | MAKE_LOCK_NAME (lfname, filename); |
8489eb67 | 697 | |
8dbbc384 | 698 | owner = current_lock_owner (&locker, lfname); |
8489eb67 | 699 | if (owner <= 0) |
8dbbc384 RS |
700 | ret = Qnil; |
701 | else if (owner == 2) | |
702 | ret = Qt; | |
703 | else | |
704 | ret = build_string (locker.user); | |
705 | ||
706 | if (owner > 0) | |
707 | FREE_LOCK_INFO (locker); | |
708 | ||
709 | return ret; | |
8489eb67 | 710 | } |
32676c08 JB |
711 | \f |
712 | /* Initialization functions. */ | |
713 | ||
a3fd58aa | 714 | void |
971de7fb | 715 | init_filelock (void) |
a3fd58aa KH |
716 | { |
717 | boot_time = 0; | |
b97771fc | 718 | boot_time_initialized = 0; |
a3fd58aa KH |
719 | } |
720 | ||
ffe75e6b EZ |
721 | #endif /* CLASH_DETECTION */ |
722 | ||
dfcf069d | 723 | void |
971de7fb | 724 | syms_of_filelock (void) |
8489eb67 | 725 | { |
29208e82 | 726 | DEFVAR_LISP ("temporary-file-directory", Vtemporary_file_directory, |
335c5470 | 727 | doc: /* The directory for writing temporary files. */); |
5f8d6a10 RS |
728 | Vtemporary_file_directory = Qnil; |
729 | ||
ffe75e6b | 730 | #ifdef CLASH_DETECTION |
8489eb67 RS |
731 | defsubr (&Sunlock_buffer); |
732 | defsubr (&Slock_buffer); | |
733 | defsubr (&Sfile_locked_p); | |
ffe75e6b | 734 | #endif |
8489eb67 | 735 | } |