Commit | Line | Data |
---|---|---|
b97771fc | 1 | /* Lock files for editing. |
acaf905b | 2 | Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2012 |
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" |
d2f6dae8 | 43 | #include "character.h" |
e5560ff7 | 44 | #include "buffer.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 | 170 | { |
882f0d81 | 171 | char cmd_string[sizeof WTMP_FILE ".19.gz"]; |
9177d978 RS |
172 | Lisp_Object tempname, filename; |
173 | int delete_flag = 0; | |
174 | ||
175 | filename = Qnil; | |
176 | ||
a8290ec3 DA |
177 | tempname = make_formatted_string |
178 | (cmd_string, "%s.%d", WTMP_FILE, counter); | |
29a2adb0 | 179 | if (! NILP (Ffile_exists_p (tempname))) |
9177d978 RS |
180 | filename = tempname; |
181 | else | |
182 | { | |
a8290ec3 DA |
183 | tempname = make_formatted_string (cmd_string, "%s.%d.gz", |
184 | WTMP_FILE, counter); | |
9177d978 RS |
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. */ | |
882f0d81 | 194 | filename = Fexpand_file_name (build_string ("wt"), |
5f8d6a10 | 195 | Vtemporary_file_directory); |
882f0d81 PE |
196 | filename = make_temp_name (filename, 1); |
197 | args[0] = build_string ("gzip"); | |
9177d978 | 198 | args[1] = Qnil; |
882f0d81 | 199 | args[2] = list2 (QCfile, filename); |
9177d978 | 200 | args[3] = Qnil; |
882f0d81 PE |
201 | args[4] = build_string ("-cd"); |
202 | args[5] = tempname; | |
9177d978 | 203 | Fcall_process (6, args); |
9177d978 RS |
204 | delete_flag = 1; |
205 | } | |
206 | } | |
207 | ||
208 | if (! NILP (filename)) | |
209 | { | |
42a5b22f | 210 | get_boot_time_1 (SSDATA (filename), 1); |
9177d978 | 211 | if (delete_flag) |
42a5b22f | 212 | unlink (SSDATA (filename)); |
9177d978 RS |
213 | } |
214 | } | |
215 | ||
216 | return boot_time; | |
217 | #else | |
218 | return 0; | |
219 | #endif | |
220 | } | |
221 | ||
e9f22ced | 222 | #ifdef BOOT_TIME |
9177d978 RS |
223 | /* Try to get the boot time from wtmp file FILENAME. |
224 | This succeeds if that file contains a reboot record. | |
9177d978 | 225 | |
b97771fc RS |
226 | If FILENAME is zero, use the same file as before; |
227 | if no FILENAME has ever been specified, this is the utmp file. | |
228 | Use the newest reboot record if NEWEST is nonzero, | |
229 | the first reboot record otherwise. | |
230 | Ignore all reboot records on or before BOOT_TIME. | |
231 | Success is indicated by setting BOOT_TIME to a larger value. */ | |
232 | ||
2f2500ef | 233 | void |
8ea90aa3 | 234 | get_boot_time_1 (const char *filename, int newest) |
9177d978 RS |
235 | { |
236 | struct utmp ut, *utp; | |
77e544a4 RS |
237 | int desc; |
238 | ||
b97771fc RS |
239 | if (filename) |
240 | { | |
241 | /* On some versions of IRIX, opening a nonexistent file name | |
242 | is likely to crash in the utmp routines. */ | |
68c45bf0 | 243 | desc = emacs_open (filename, O_RDONLY, 0); |
b97771fc RS |
244 | if (desc < 0) |
245 | return; | |
246 | ||
68c45bf0 | 247 | emacs_close (desc); |
b97771fc RS |
248 | |
249 | utmpname (filename); | |
250 | } | |
9177d978 | 251 | |
c321b190 | 252 | setutent (); |
b97771fc | 253 | |
c321b190 RS |
254 | while (1) |
255 | { | |
256 | /* Find the next reboot record. */ | |
257 | ut.ut_type = BOOT_TIME; | |
258 | utp = getutid (&ut); | |
259 | if (! utp) | |
260 | break; | |
261 | /* Compare reboot times and use the newest one. */ | |
262 | if (utp->ut_time > boot_time) | |
b97771fc RS |
263 | { |
264 | boot_time = utp->ut_time; | |
265 | if (! newest) | |
266 | break; | |
267 | } | |
c321b190 RS |
268 | /* Advance on element in the file |
269 | so that getutid won't repeat the same one. */ | |
270 | utp = getutent (); | |
271 | if (! utp) | |
272 | break; | |
273 | } | |
15e88d21 | 274 | endutent (); |
15e88d21 | 275 | } |
e9f22ced | 276 | #endif /* BOOT_TIME */ |
15e88d21 | 277 | \f |
8dbbc384 | 278 | /* Here is the structure that stores information about a lock. */ |
32676c08 | 279 | |
8dbbc384 RS |
280 | typedef struct |
281 | { | |
282 | char *user; | |
283 | char *host; | |
882f0d81 | 284 | pid_t pid; |
15e88d21 | 285 | time_t boot_time; |
8dbbc384 | 286 | } lock_info_type; |
32676c08 | 287 | |
8dbbc384 RS |
288 | /* Free the two dynamically-allocated pieces in PTR. */ |
289 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 290 | |
e31fbc7a | 291 | |
8dbbc384 | 292 | /* Write the name of the lock file for FN into LFNAME. Length will be |
c1355e1f GM |
293 | that of FN plus two more for the leading `.#' plus 1 for the |
294 | trailing period plus one for the digit after it plus one for the | |
295 | null. */ | |
7b92975f | 296 | #define MAKE_LOCK_NAME(lock, file) \ |
38182d90 | 297 | (lock = alloca (SBYTES (file) + 2 + 1 + 1 + 1), \ |
8dbbc384 | 298 | fill_in_lock_file_name (lock, (file))) |
e31fbc7a | 299 | |
8dbbc384 | 300 | static void |
971de7fb | 301 | fill_in_lock_file_name (register char *lockfile, register Lisp_Object fn) |
e31fbc7a | 302 | { |
c293e30c | 303 | ptrdiff_t length = SBYTES (fn); |
8dbbc384 | 304 | register char *p; |
c1355e1f GM |
305 | struct stat st; |
306 | int count = 0; | |
8dbbc384 | 307 | |
42a5b22f | 308 | strcpy (lockfile, SSDATA (fn)); |
8dbbc384 RS |
309 | |
310 | /* Shift the nondirectory part of the file name (including the null) | |
311 | right two characters. Here is one of the places where we'd have to | |
312 | do something to support 14-character-max file names. */ | |
c293e30c | 313 | for (p = lockfile + length; p != lockfile && *p != '/'; p--) |
8dbbc384 | 314 | p[2] = *p; |
177c0ea7 | 315 | |
8dbbc384 RS |
316 | /* Insert the `.#'. */ |
317 | p[1] = '.'; | |
318 | p[2] = '#'; | |
c1355e1f | 319 | |
c293e30c | 320 | p = p + length + 2; |
c1355e1f GM |
321 | |
322 | while (lstat (lockfile, &st) == 0 && !S_ISLNK (st.st_mode)) | |
323 | { | |
324 | if (count > 9) | |
325 | { | |
326 | *p = '\0'; | |
327 | return; | |
328 | } | |
329 | sprintf (p, ".%d", count++); | |
330 | } | |
8dbbc384 | 331 | } |
e31fbc7a | 332 | |
8dbbc384 RS |
333 | /* Lock the lock file named LFNAME. |
334 | If FORCE is nonzero, we do so even if it is already locked. | |
335 | Return 1 if successful, 0 if not. */ | |
e31fbc7a | 336 | |
8dbbc384 | 337 | static int |
971de7fb | 338 | lock_file_1 (char *lfname, int force) |
8dbbc384 RS |
339 | { |
340 | register int err; | |
a81d11a3 | 341 | printmax_t boot, pid; |
8ea90aa3 DN |
342 | const char *user_name; |
343 | const char *host_name; | |
662c2ef2 | 344 | char *lock_info_str; |
b5cd1905 PE |
345 | ptrdiff_t lock_info_size; |
346 | int symlink_errno; | |
347 | USE_SAFE_ALLOCA; | |
662c2ef2 | 348 | |
4ba93ac0 | 349 | /* Call this first because it can GC. */ |
b3dd38ab | 350 | boot = get_boot_time (); |
4ba93ac0 | 351 | |
662c2ef2 | 352 | if (STRINGP (Fuser_login_name (Qnil))) |
51b59d79 | 353 | user_name = SSDATA (Fuser_login_name (Qnil)); |
662c2ef2 RS |
354 | else |
355 | user_name = ""; | |
356 | if (STRINGP (Fsystem_name ())) | |
51b59d79 | 357 | host_name = SSDATA (Fsystem_name ()); |
662c2ef2 RS |
358 | else |
359 | host_name = ""; | |
b5cd1905 PE |
360 | lock_info_size = (strlen (user_name) + strlen (host_name) |
361 | + 2 * INT_STRLEN_BOUND (printmax_t) | |
362 | + sizeof "@.:"); | |
363 | SAFE_ALLOCA (lock_info_str, char *, lock_info_size); | |
882f0d81 | 364 | pid = getpid (); |
8dbbc384 | 365 | |
b5cd1905 PE |
366 | esprintf (lock_info_str, boot ? "%s@%s.%"pMd":%"pMd : "%s@%s.%"pMd, |
367 | user_name, host_name, pid, boot); | |
8dbbc384 RS |
368 | |
369 | err = symlink (lock_info_str, lfname); | |
370 | if (errno == EEXIST && force) | |
e31fbc7a | 371 | { |
8dbbc384 RS |
372 | unlink (lfname); |
373 | err = symlink (lock_info_str, lfname); | |
e31fbc7a | 374 | } |
e31fbc7a | 375 | |
b5cd1905 PE |
376 | symlink_errno = errno; |
377 | SAFE_FREE (); | |
378 | errno = symlink_errno; | |
8dbbc384 RS |
379 | return err == 0; |
380 | } | |
e31fbc7a | 381 | |
9177d978 | 382 | /* Return 1 if times A and B are no more than one second apart. */ |
32676c08 | 383 | |
03d78a21 | 384 | static int |
971de7fb | 385 | within_one_second (time_t a, time_t b) |
9177d978 RS |
386 | { |
387 | return (a - b >= -1 && a - b <= 1); | |
388 | } | |
8dbbc384 RS |
389 | \f |
390 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, | |
391 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
392 | 2 if the current process owns it, | |
393 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 394 | |
8dbbc384 | 395 | static int |
971de7fb | 396 | current_lock_owner (lock_info_type *owner, char *lfname) |
32676c08 | 397 | { |
d1fdcab7 | 398 | int ret; |
882f0d81 PE |
399 | ptrdiff_t len; |
400 | lock_info_type local_owner; | |
401 | intmax_t n; | |
15e88d21 | 402 | char *at, *dot, *colon; |
d1fdcab7 PE |
403 | char readlink_buf[READLINK_BUFSIZE]; |
404 | char *lfinfo = emacs_readlink (lfname, readlink_buf); | |
177c0ea7 | 405 | |
8dbbc384 | 406 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ |
d1fdcab7 PE |
407 | if (!lfinfo) |
408 | return errno == ENOENT ? 0 : -1; | |
177c0ea7 | 409 | |
8dbbc384 | 410 | /* Even if the caller doesn't want the owner info, we still have to |
882f0d81 | 411 | read it to determine return value. */ |
8dbbc384 | 412 | if (!owner) |
882f0d81 | 413 | owner = &local_owner; |
177c0ea7 | 414 | |
15e88d21 | 415 | /* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */ |
50624218 | 416 | /* The USER is everything before the last @. */ |
8966b757 AS |
417 | at = strrchr (lfinfo, '@'); |
418 | dot = strrchr (lfinfo, '.'); | |
15e88d21 RS |
419 | if (!at || !dot) |
420 | { | |
d1fdcab7 PE |
421 | if (lfinfo != readlink_buf) |
422 | xfree (lfinfo); | |
15e88d21 RS |
423 | return -1; |
424 | } | |
8dbbc384 | 425 | len = at - lfinfo; |
23f86fce | 426 | owner->user = xmalloc (len + 1); |
882f0d81 | 427 | memcpy (owner->user, lfinfo, len); |
8dbbc384 | 428 | owner->user[len] = 0; |
177c0ea7 | 429 | |
15e88d21 | 430 | /* The PID is everything from the last `.' to the `:'. */ |
882f0d81 PE |
431 | errno = 0; |
432 | n = strtoimax (dot + 1, NULL, 10); | |
433 | owner->pid = | |
434 | ((0 <= n && n <= TYPE_MAXIMUM (pid_t) | |
435 | && (TYPE_MAXIMUM (pid_t) < INTMAX_MAX || errno != ERANGE)) | |
436 | ? n : 0); | |
437 | ||
438 | colon = strchr (dot + 1, ':'); | |
15e88d21 | 439 | /* After the `:', if there is one, comes the boot time. */ |
882f0d81 PE |
440 | n = 0; |
441 | if (colon) | |
442 | { | |
443 | errno = 0; | |
444 | n = strtoimax (colon + 1, NULL, 10); | |
445 | } | |
446 | owner->boot_time = | |
447 | ((0 <= n && n <= TYPE_MAXIMUM (time_t) | |
448 | && (TYPE_MAXIMUM (time_t) < INTMAX_MAX || errno != ERANGE)) | |
449 | ? n : 0); | |
32676c08 | 450 | |
8dbbc384 RS |
451 | /* The host is everything in between. */ |
452 | len = dot - at - 1; | |
23f86fce | 453 | owner->host = xmalloc (len + 1); |
882f0d81 | 454 | memcpy (owner->host, at + 1, len); |
8dbbc384 | 455 | owner->host[len] = 0; |
32676c08 | 456 | |
8dbbc384 | 457 | /* We're done looking at the link info. */ |
d1fdcab7 PE |
458 | if (lfinfo != readlink_buf) |
459 | xfree (lfinfo); | |
177c0ea7 | 460 | |
8dbbc384 | 461 | /* On current host? */ |
662c2ef2 | 462 | if (STRINGP (Fsystem_name ()) |
42a5b22f | 463 | && strcmp (owner->host, SSDATA (Fsystem_name ())) == 0) |
32676c08 | 464 | { |
8dbbc384 RS |
465 | if (owner->pid == getpid ()) |
466 | ret = 2; /* We own it. */ | |
72dcef0e | 467 | else if (owner->pid > 0 |
15e88d21 RS |
468 | && (kill (owner->pid, 0) >= 0 || errno == EPERM) |
469 | && (owner->boot_time == 0 | |
9177d978 | 470 | || within_one_second (owner->boot_time, get_boot_time ()))) |
8dbbc384 | 471 | ret = 1; /* An existing process on this machine owns it. */ |
8dbbc384 RS |
472 | /* The owner process is dead or has a strange pid (<=0), so try to |
473 | zap the lockfile. */ | |
72dcef0e | 474 | else if (unlink (lfname) < 0) |
8dbbc384 | 475 | ret = -1; |
72dcef0e RS |
476 | else |
477 | ret = 0; | |
32676c08 | 478 | } |
8dbbc384 RS |
479 | else |
480 | { /* If we wanted to support the check for stale locks on remote machines, | |
481 | here's where we'd do it. */ | |
482 | ret = 1; | |
483 | } | |
177c0ea7 | 484 | |
8dbbc384 | 485 | /* Avoid garbage. */ |
882f0d81 | 486 | if (owner == &local_owner || ret <= 0) |
8dbbc384 RS |
487 | { |
488 | FREE_LOCK_INFO (*owner); | |
489 | } | |
490 | return ret; | |
32676c08 JB |
491 | } |
492 | ||
8dbbc384 RS |
493 | \f |
494 | /* Lock the lock named LFNAME if possible. | |
495 | Return 0 in that case. | |
496 | Return positive if some other process owns the lock, and info about | |
497 | that process in CLASHER. | |
498 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 499 | |
8dbbc384 | 500 | static int |
971de7fb | 501 | lock_if_free (lock_info_type *clasher, register char *lfname) |
8dbbc384 | 502 | { |
cfc01fa7 | 503 | while (lock_file_1 (lfname, 0) == 0) |
8dbbc384 RS |
504 | { |
505 | int locker; | |
e0e0205b | 506 | |
8dbbc384 RS |
507 | if (errno != EEXIST) |
508 | return -1; | |
177c0ea7 | 509 | |
8dbbc384 RS |
510 | locker = current_lock_owner (clasher, lfname); |
511 | if (locker == 2) | |
512 | { | |
513 | FREE_LOCK_INFO (*clasher); | |
514 | return 0; /* We ourselves locked it. */ | |
515 | } | |
516 | else if (locker == 1) | |
517 | return 1; /* Someone else has it. */ | |
5df0b2fa | 518 | else if (locker == -1) |
ae1ef097 | 519 | return -1; /* current_lock_owner returned strange error. */ |
8dbbc384 | 520 | |
cfc01fa7 | 521 | /* We deleted a stale lock; try again to lock the file. */ |
8dbbc384 RS |
522 | } |
523 | return 0; | |
8489eb67 RS |
524 | } |
525 | ||
8dbbc384 | 526 | /* lock_file locks file FN, |
8489eb67 RS |
527 | meaning it serves notice on the world that you intend to edit that file. |
528 | This should be done only when about to modify a file-visiting | |
529 | buffer previously unmodified. | |
8dbbc384 | 530 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
531 | as either the file is already locked, or the user has already |
532 | decided to go ahead without locking. | |
533 | ||
8dbbc384 | 534 | When this returns, either the lock is locked for us, |
8489eb67 RS |
535 | or the user has said to go ahead without locking. |
536 | ||
8dbbc384 | 537 | If the file is locked by someone else, this calls |
8489eb67 | 538 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 539 | the file name and info about the user who did the locking. |
8489eb67 RS |
540 | This function can signal an error, or return t meaning |
541 | take away the lock, or return nil meaning ignore the lock. */ | |
542 | ||
8489eb67 | 543 | void |
971de7fb | 544 | lock_file (Lisp_Object fn) |
8489eb67 | 545 | { |
f4a4528d | 546 | register Lisp_Object attack, orig_fn, encoded_fn; |
8dbbc384 | 547 | register char *lfname, *locker; |
b5cd1905 | 548 | ptrdiff_t locker_size; |
8dbbc384 | 549 | lock_info_type lock_info; |
a81d11a3 | 550 | printmax_t pid; |
3edc33a4 | 551 | struct gcpro gcpro1; |
b5cd1905 | 552 | USE_SAFE_ALLOCA; |
8489eb67 | 553 | |
836d29b3 DA |
554 | /* Don't do locking if the user has opted out. */ |
555 | if (! create_lockfiles) | |
556 | return; | |
557 | ||
33bae690 RS |
558 | /* Don't do locking while dumping Emacs. |
559 | Uncompressing wtmp files uses call-process, which does not work | |
560 | in an uninitialized Emacs. */ | |
561 | if (! NILP (Vpurify_flag)) | |
562 | return; | |
563 | ||
5383bc6d | 564 | orig_fn = fn; |
8af8a9ca | 565 | GCPRO1 (fn); |
1e89de84 | 566 | fn = Fexpand_file_name (fn, Qnil); |
f4a4528d | 567 | encoded_fn = ENCODE_FILE (fn); |
1e89de84 | 568 | |
8dbbc384 | 569 | /* Create the name of the lock-file for file fn */ |
f4a4528d | 570 | MAKE_LOCK_NAME (lfname, encoded_fn); |
8489eb67 | 571 | |
32676c08 JB |
572 | /* See if this file is visited and has changed on disk since it was |
573 | visited. */ | |
8489eb67 | 574 | { |
a57bc488 | 575 | register Lisp_Object subject_buf; |
3036594f | 576 | |
5383bc6d | 577 | subject_buf = get_truename_buffer (orig_fn); |
3036594f | 578 | |
265a9e55 JB |
579 | if (!NILP (subject_buf) |
580 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
581 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 | 582 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
3036594f | 583 | |
8489eb67 | 584 | } |
8af8a9ca | 585 | UNGCPRO; |
8489eb67 RS |
586 | |
587 | /* Try to lock the lock. */ | |
8dbbc384 RS |
588 | if (lock_if_free (&lock_info, lfname) <= 0) |
589 | /* Return now if we have locked it, or if lock creation failed */ | |
8489eb67 RS |
590 | return; |
591 | ||
592 | /* Else consider breaking the lock */ | |
b5cd1905 PE |
593 | locker_size = (strlen (lock_info.user) + strlen (lock_info.host) |
594 | + INT_STRLEN_BOUND (printmax_t) | |
595 | + sizeof "@ (pid )"); | |
596 | SAFE_ALLOCA (locker, char *, locker_size); | |
882f0d81 | 597 | pid = lock_info.pid; |
b5cd1905 PE |
598 | esprintf (locker, "%s@%s (pid %"pMd")", |
599 | lock_info.user, lock_info.host, pid); | |
8dbbc384 | 600 | FREE_LOCK_INFO (lock_info); |
177c0ea7 | 601 | |
8dbbc384 | 602 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); |
b5cd1905 | 603 | SAFE_FREE (); |
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 | { |
5e617bc2 | 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 | ||
a7ca3326 | 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 | } |
a3fd58aa | 711 | |
ffe75e6b EZ |
712 | #endif /* CLASH_DETECTION */ |
713 | ||
dfcf069d | 714 | void |
971de7fb | 715 | syms_of_filelock (void) |
8489eb67 | 716 | { |
29208e82 | 717 | DEFVAR_LISP ("temporary-file-directory", Vtemporary_file_directory, |
335c5470 | 718 | doc: /* The directory for writing temporary files. */); |
5f8d6a10 RS |
719 | Vtemporary_file_directory = Qnil; |
720 | ||
836d29b3 DA |
721 | DEFVAR_BOOL ("create-lockfiles", create_lockfiles, |
722 | doc: /* Non-nil means use lockfiles to avoid editing collisions. */); | |
723 | create_lockfiles = 1; | |
724 | ||
ffe75e6b | 725 | #ifdef CLASH_DETECTION |
8489eb67 RS |
726 | defsubr (&Sunlock_buffer); |
727 | defsubr (&Slock_buffer); | |
728 | defsubr (&Sfile_locked_p); | |
ffe75e6b | 729 | #endif |
8489eb67 | 730 | } |