Commit | Line | Data |
---|---|---|
b97771fc | 1 | /* Lock files for editing. |
ab422c4d PE |
2 | Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2013 Free Software |
3 | 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> |
bfb61299 | 26 | |
5b9c0a1d | 27 | #ifdef HAVE_PWD_H |
8489eb67 | 28 | #include <pwd.h> |
5b9c0a1d | 29 | #endif |
bfb61299 | 30 | |
8489eb67 | 31 | #include <sys/file.h> |
8489eb67 | 32 | #include <fcntl.h> |
dfcf069d | 33 | #include <unistd.h> |
dfcf069d | 34 | |
f805a125 | 35 | #ifdef __FreeBSD__ |
f805a125 KH |
36 | #include <sys/sysctl.h> |
37 | #endif /* __FreeBSD__ */ | |
38 | ||
e5ef3cdf | 39 | #include <errno.h> |
e5ef3cdf | 40 | |
8489eb67 | 41 | #include "lisp.h" |
d2f6dae8 | 42 | #include "character.h" |
e5560ff7 | 43 | #include "buffer.h" |
f4a4528d | 44 | #include "coding.h" |
9177d978 | 45 | #include "systime.h" |
343a2aef | 46 | #ifdef WINDOWSNT |
531e70ec | 47 | #include <share.h> |
343a2aef EZ |
48 | #include "w32.h" /* for dostounix_filename */ |
49 | #endif | |
8489eb67 | 50 | |
8489eb67 | 51 | #ifdef CLASH_DETECTION |
e788eecc | 52 | |
c6d09b8d | 53 | #ifdef HAVE_UTMP_H |
e788eecc | 54 | #include <utmp.h> |
c6d09b8d | 55 | #endif |
77e544a4 | 56 | |
a48de9b2 PE |
57 | /* A file whose last-modified time is just after the most recent boot. |
58 | Define this to be NULL to disable checking for this file. */ | |
59 | #ifndef BOOT_TIME_FILE | |
60 | #define BOOT_TIME_FILE "/var/run/random-seed" | |
61 | #endif | |
62 | ||
77e544a4 RS |
63 | #ifndef WTMP_FILE |
64 | #define WTMP_FILE "/var/log/wtmp" | |
65 | #endif | |
177c0ea7 | 66 | |
8dbbc384 RS |
67 | /* The strategy: to lock a file FN, create a symlink .#FN in FN's |
68 | directory, with link data `user@host.pid'. This avoids a single | |
69 | mount (== failure) point for lock files. | |
70 | ||
71 | When the host in the lock data is the current host, we can check if | |
72 | the pid is valid with kill. | |
177c0ea7 | 73 | |
8dbbc384 RS |
74 | Otherwise, we could look at a separate file that maps hostnames to |
75 | reboot times to see if the remote pid can possibly be valid, since we | |
76 | don't want Emacs to have to communicate via pipes or sockets or | |
77 | whatever to other processes, either locally or remotely; rms says | |
78 | that's too unreliable. Hence the separate file, which could | |
79 | theoretically be updated by daemons running separately -- but this | |
80 | whole idea is unimplemented; in practice, at least in our | |
1c4f857c | 81 | environment, it seems such stale locks arise fairly infrequently, and |
8dbbc384 RS |
82 | Emacs' standard methods of dealing with clashes suffice. |
83 | ||
84 | We use symlinks instead of normal files because (1) they can be | |
85 | stored more efficiently on the filesystem, since the kernel knows | |
86 | they will be small, and (2) all the info about the lock can be read | |
87 | in a single system call (readlink). Although we could use regular | |
1c4f857c | 88 | files to be useful on old systems lacking symlinks, nowadays |
8dbbc384 RS |
89 | virtually all such systems are probably single-user anyway, so it |
90 | didn't seem worth the complication. | |
177c0ea7 | 91 | |
8dbbc384 RS |
92 | Similarly, we don't worry about a possible 14-character limit on |
93 | file names, because those are all the same systems that don't have | |
94 | symlinks. | |
177c0ea7 | 95 | |
8dbbc384 RS |
96 | This is compatible with the locking scheme used by Interleaf (which |
97 | has contributed this implementation for Emacs), and was designed by | |
98 | Ethan Jacobson, Kimbo Mundy, and others. | |
177c0ea7 | 99 | |
8dbbc384 | 100 | --karl@cs.umb.edu/karl@hq.ileaf.com. */ |
8489eb67 | 101 | |
8dbbc384 | 102 | \f |
15e88d21 RS |
103 | /* Return the time of the last system boot. */ |
104 | ||
105 | static time_t boot_time; | |
f75d7a91 | 106 | static bool boot_time_initialized; |
15e88d21 | 107 | |
2f2500ef | 108 | #ifdef BOOT_TIME |
f75d7a91 | 109 | static void get_boot_time_1 (const char *, bool); |
2f2500ef DL |
110 | #endif |
111 | ||
15e88d21 | 112 | static time_t |
971de7fb | 113 | get_boot_time (void) |
15e88d21 | 114 | { |
9d2818d6 | 115 | #if defined (BOOT_TIME) |
9177d978 | 116 | int counter; |
2decc5a9 | 117 | #endif |
15e88d21 | 118 | |
b97771fc | 119 | if (boot_time_initialized) |
15e88d21 | 120 | return boot_time; |
b97771fc | 121 | boot_time_initialized = 1; |
15e88d21 | 122 | |
f805a125 KH |
123 | #if defined (CTL_KERN) && defined (KERN_BOOTTIME) |
124 | { | |
125 | int mib[2]; | |
126 | size_t size; | |
127 | struct timeval boottime_val; | |
128 | ||
129 | mib[0] = CTL_KERN; | |
130 | mib[1] = KERN_BOOTTIME; | |
131 | size = sizeof (boottime_val); | |
132 | ||
133 | if (sysctl (mib, 2, &boottime_val, &size, NULL, 0) >= 0) | |
134 | { | |
135 | boot_time = boottime_val.tv_sec; | |
136 | return boot_time; | |
137 | } | |
138 | } | |
139 | #endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */ | |
9177d978 | 140 | |
a48de9b2 PE |
141 | if (BOOT_TIME_FILE) |
142 | { | |
143 | struct stat st; | |
144 | if (stat (BOOT_TIME_FILE, &st) == 0) | |
145 | { | |
146 | boot_time = st.st_mtime; | |
147 | return boot_time; | |
148 | } | |
149 | } | |
150 | ||
9d2818d6 | 151 | #if defined (BOOT_TIME) |
b97771fc RS |
152 | #ifndef CANNOT_DUMP |
153 | /* The utmp routines maintain static state. | |
154 | Don't touch that state unless we are initialized, | |
155 | since it might not survive dumping. */ | |
156 | if (! initialized) | |
157 | return boot_time; | |
158 | #endif /* not CANNOT_DUMP */ | |
159 | ||
160 | /* Try to get boot time from utmp before wtmp, | |
161 | since utmp is typically much smaller than wtmp. | |
162 | Passing a null pointer causes get_boot_time_1 | |
163 | to inspect the default file, namely utmp. */ | |
164 | get_boot_time_1 ((char *) 0, 0); | |
165 | if (boot_time) | |
166 | return boot_time; | |
167 | ||
9177d978 | 168 | /* Try to get boot time from the current wtmp file. */ |
b97771fc | 169 | get_boot_time_1 (WTMP_FILE, 1); |
9177d978 RS |
170 | |
171 | /* If we did not find a boot time in wtmp, look at wtmp, and so on. */ | |
b97771fc | 172 | for (counter = 0; counter < 20 && ! boot_time; counter++) |
9177d978 | 173 | { |
882f0d81 | 174 | char cmd_string[sizeof WTMP_FILE ".19.gz"]; |
9177d978 | 175 | Lisp_Object tempname, filename; |
f75d7a91 | 176 | bool delete_flag = 0; |
9177d978 RS |
177 | |
178 | filename = Qnil; | |
179 | ||
a8290ec3 DA |
180 | tempname = make_formatted_string |
181 | (cmd_string, "%s.%d", WTMP_FILE, counter); | |
29a2adb0 | 182 | if (! NILP (Ffile_exists_p (tempname))) |
9177d978 RS |
183 | filename = tempname; |
184 | else | |
185 | { | |
a8290ec3 DA |
186 | tempname = make_formatted_string (cmd_string, "%s.%d.gz", |
187 | WTMP_FILE, counter); | |
9177d978 RS |
188 | if (! NILP (Ffile_exists_p (tempname))) |
189 | { | |
190 | Lisp_Object args[6]; | |
f1d367aa GM |
191 | |
192 | /* The utmp functions on mescaline.gnu.org accept only | |
193 | file names up to 8 characters long. Choose a 2 | |
194 | character long prefix, and call make_temp_file with | |
195 | second arg non-zero, so that it will add not more | |
196 | than 6 characters to the prefix. */ | |
882f0d81 | 197 | filename = Fexpand_file_name (build_string ("wt"), |
5f8d6a10 | 198 | Vtemporary_file_directory); |
882f0d81 PE |
199 | filename = make_temp_name (filename, 1); |
200 | args[0] = build_string ("gzip"); | |
9177d978 | 201 | args[1] = Qnil; |
882f0d81 | 202 | args[2] = list2 (QCfile, filename); |
9177d978 | 203 | args[3] = Qnil; |
882f0d81 PE |
204 | args[4] = build_string ("-cd"); |
205 | args[5] = tempname; | |
9177d978 | 206 | Fcall_process (6, args); |
9177d978 RS |
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. | |
f75d7a91 | 231 | Use the newest reboot record if NEWEST, |
b97771fc RS |
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 |
f75d7a91 | 237 | get_boot_time_1 (const char *filename, bool 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; | |
882f0d81 | 287 | pid_t pid; |
15e88d21 | 288 | time_t boot_time; |
8dbbc384 | 289 | } lock_info_type; |
32676c08 | 290 | |
8dbbc384 RS |
291 | /* Free the two dynamically-allocated pieces in PTR. */ |
292 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 293 | |
e31fbc7a | 294 | |
343a2aef EZ |
295 | /* Write the name of the lock file for FNAME into LOCKNAME. Length |
296 | will be that of FN plus two more for the leading `.#' plus 1 for | |
297 | the trailing period plus one for the digit after it plus one for | |
298 | the null. */ | |
299 | #define MAKE_LOCK_NAME(LOCKNAME, FNAME) \ | |
300 | (LOCKNAME = alloca (SBYTES (FNAME) + 2 + 1 + 1 + 1), \ | |
301 | fill_in_lock_file_name (LOCKNAME, (FNAME))) | |
302 | ||
303 | #ifdef WINDOWSNT | |
304 | /* 256 chars for user, 1024 chars for host, 10 digits for each of 2 int's. */ | |
305 | #define MAX_LFINFO (256 + 1024 + 10 + 10 + 2) | |
306 | /* min size: .@PID */ | |
307 | #define IS_LOCK_FILE(ST) (MAX_LFINFO >= (ST).st_size && (ST).st_size >= 3) | |
308 | #else | |
309 | #define IS_LOCK_FILE(ST) S_ISLNK ((ST).st_mode) | |
310 | #endif | |
e31fbc7a | 311 | |
8dbbc384 | 312 | static void |
971de7fb | 313 | fill_in_lock_file_name (register char *lockfile, register Lisp_Object fn) |
e31fbc7a | 314 | { |
c293e30c | 315 | ptrdiff_t length = SBYTES (fn); |
8dbbc384 | 316 | register char *p; |
c1355e1f GM |
317 | struct stat st; |
318 | int count = 0; | |
8dbbc384 | 319 | |
42a5b22f | 320 | strcpy (lockfile, SSDATA (fn)); |
8dbbc384 RS |
321 | |
322 | /* Shift the nondirectory part of the file name (including the null) | |
323 | right two characters. Here is one of the places where we'd have to | |
324 | do something to support 14-character-max file names. */ | |
c293e30c | 325 | for (p = lockfile + length; p != lockfile && *p != '/'; p--) |
8dbbc384 | 326 | p[2] = *p; |
177c0ea7 | 327 | |
8dbbc384 RS |
328 | /* Insert the `.#'. */ |
329 | p[1] = '.'; | |
330 | p[2] = '#'; | |
c1355e1f | 331 | |
1938d88c | 332 | p = lockfile + length + 2; |
c1355e1f | 333 | |
343a2aef | 334 | while (lstat (lockfile, &st) == 0 && !IS_LOCK_FILE (st)) |
c1355e1f GM |
335 | { |
336 | if (count > 9) | |
337 | { | |
338 | *p = '\0'; | |
339 | return; | |
340 | } | |
341 | sprintf (p, ".%d", count++); | |
342 | } | |
8dbbc384 | 343 | } |
e31fbc7a | 344 | |
343a2aef EZ |
345 | static int |
346 | create_lock_file (char *lfname, char *lock_info_str, bool force) | |
347 | { | |
348 | int err; | |
349 | ||
350 | #ifdef WINDOWSNT | |
351 | /* Symlinks are supported only by latest versions of Windows, and | |
352 | creating them is a privileged operation that often triggers UAC | |
353 | elevation prompts. Therefore, instead of using symlinks, we | |
354 | create a regular file with the lock info written as its | |
355 | contents. */ | |
356 | { | |
531e70ec EZ |
357 | /* Deny everybody else any kind of access to the file until we are |
358 | done writing it and close the handle. This makes the entire | |
359 | open/write/close operation atomic, as far as other processes | |
360 | are concerned. */ | |
361 | int fd = _sopen (lfname, | |
362 | _O_WRONLY | _O_BINARY | _O_CREAT | _O_EXCL | _O_NOINHERIT, | |
363 | _SH_DENYRW, S_IREAD | S_IWRITE); | |
343a2aef EZ |
364 | |
365 | if (fd < 0 && errno == EEXIST && force) | |
531e70ec EZ |
366 | fd = _sopen (lfname, _O_WRONLY | _O_BINARY | _O_TRUNC |_O_NOINHERIT, |
367 | _SH_DENYRW, S_IREAD | S_IWRITE); | |
343a2aef EZ |
368 | if (fd >= 0) |
369 | { | |
370 | ssize_t lock_info_len = strlen (lock_info_str); | |
371 | ||
372 | err = 0; | |
373 | if (emacs_write (fd, lock_info_str, lock_info_len) != lock_info_len) | |
374 | err = -1; | |
375 | if (emacs_close (fd)) | |
376 | err = -1; | |
377 | } | |
378 | else | |
379 | err = -1; | |
380 | } | |
381 | #else | |
382 | err = symlink (lock_info_str, lfname); | |
383 | if (errno == EEXIST && force) | |
384 | { | |
385 | unlink (lfname); | |
386 | err = symlink (lock_info_str, lfname); | |
387 | } | |
388 | #endif | |
389 | ||
390 | return err; | |
391 | } | |
392 | ||
8dbbc384 | 393 | /* Lock the lock file named LFNAME. |
f75d7a91 PE |
394 | If FORCE, do so even if it is already locked. |
395 | Return true if successful. */ | |
e31fbc7a | 396 | |
f75d7a91 PE |
397 | static bool |
398 | lock_file_1 (char *lfname, bool force) | |
8dbbc384 | 399 | { |
98c6f1e3 | 400 | int err; |
b5cd1905 PE |
401 | int symlink_errno; |
402 | USE_SAFE_ALLOCA; | |
662c2ef2 | 403 | |
4ba93ac0 | 404 | /* Call this first because it can GC. */ |
98c6f1e3 PE |
405 | printmax_t boot = get_boot_time (); |
406 | ||
407 | Lisp_Object luser_name = Fuser_login_name (Qnil); | |
408 | char const *user_name = STRINGP (luser_name) ? SSDATA (luser_name) : ""; | |
409 | Lisp_Object lhost_name = Fsystem_name (); | |
410 | char const *host_name = STRINGP (lhost_name) ? SSDATA (lhost_name) : ""; | |
411 | ptrdiff_t lock_info_size = (strlen (user_name) + strlen (host_name) | |
412 | + 2 * INT_STRLEN_BOUND (printmax_t) | |
413 | + sizeof "@.:"); | |
414 | char *lock_info_str = SAFE_ALLOCA (lock_info_size); | |
415 | printmax_t pid = getpid (); | |
8dbbc384 | 416 | |
b5cd1905 PE |
417 | esprintf (lock_info_str, boot ? "%s@%s.%"pMd":%"pMd : "%s@%s.%"pMd, |
418 | user_name, host_name, pid, boot); | |
343a2aef | 419 | err = create_lock_file (lfname, lock_info_str, force); |
e31fbc7a | 420 | |
b5cd1905 PE |
421 | symlink_errno = errno; |
422 | SAFE_FREE (); | |
423 | errno = symlink_errno; | |
8dbbc384 RS |
424 | return err == 0; |
425 | } | |
e31fbc7a | 426 | |
f75d7a91 | 427 | /* Return true if times A and B are no more than one second apart. */ |
32676c08 | 428 | |
f75d7a91 | 429 | static bool |
971de7fb | 430 | within_one_second (time_t a, time_t b) |
9177d978 RS |
431 | { |
432 | return (a - b >= -1 && a - b <= 1); | |
433 | } | |
8dbbc384 | 434 | \f |
343a2aef EZ |
435 | static Lisp_Object |
436 | read_lock_data (char *lfname) | |
437 | { | |
438 | #ifndef WINDOWSNT | |
439 | return emacs_readlinkat (AT_FDCWD, lfname); | |
440 | #else | |
441 | int fd = emacs_open (lfname, O_RDONLY | O_BINARY, S_IREAD); | |
442 | ssize_t nbytes; | |
443 | char lfinfo[MAX_LFINFO + 1]; | |
444 | ||
445 | if (fd < 0) | |
446 | return Qnil; | |
447 | ||
448 | nbytes = emacs_read (fd, lfinfo, MAX_LFINFO); | |
449 | emacs_close (fd); | |
450 | ||
451 | if (nbytes > 0) | |
452 | { | |
453 | lfinfo[nbytes] = '\0'; | |
454 | return build_string (lfinfo); | |
455 | } | |
456 | else | |
457 | return Qnil; | |
458 | #endif | |
459 | } | |
460 | ||
8dbbc384 RS |
461 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, |
462 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
463 | 2 if the current process owns it, | |
464 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 465 | |
8dbbc384 | 466 | static int |
971de7fb | 467 | current_lock_owner (lock_info_type *owner, char *lfname) |
32676c08 | 468 | { |
d1fdcab7 | 469 | int ret; |
882f0d81 PE |
470 | ptrdiff_t len; |
471 | lock_info_type local_owner; | |
472 | intmax_t n; | |
15e88d21 | 473 | char *at, *dot, *colon; |
343a2aef | 474 | Lisp_Object lfinfo_object = read_lock_data (lfname); |
8654f9d7 PE |
475 | char *lfinfo; |
476 | struct gcpro gcpro1; | |
177c0ea7 | 477 | |
8dbbc384 | 478 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ |
8654f9d7 | 479 | if (NILP (lfinfo_object)) |
d1fdcab7 | 480 | return errno == ENOENT ? 0 : -1; |
8654f9d7 | 481 | lfinfo = SSDATA (lfinfo_object); |
177c0ea7 | 482 | |
8dbbc384 | 483 | /* Even if the caller doesn't want the owner info, we still have to |
882f0d81 | 484 | read it to determine return value. */ |
8dbbc384 | 485 | if (!owner) |
882f0d81 | 486 | owner = &local_owner; |
177c0ea7 | 487 | |
15e88d21 | 488 | /* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */ |
50624218 | 489 | /* The USER is everything before the last @. */ |
8966b757 AS |
490 | at = strrchr (lfinfo, '@'); |
491 | dot = strrchr (lfinfo, '.'); | |
15e88d21 | 492 | if (!at || !dot) |
8654f9d7 | 493 | return -1; |
8dbbc384 | 494 | len = at - lfinfo; |
8654f9d7 | 495 | GCPRO1 (lfinfo_object); |
23f86fce | 496 | owner->user = xmalloc (len + 1); |
882f0d81 | 497 | memcpy (owner->user, lfinfo, len); |
8dbbc384 | 498 | owner->user[len] = 0; |
177c0ea7 | 499 | |
15e88d21 | 500 | /* The PID is everything from the last `.' to the `:'. */ |
882f0d81 PE |
501 | errno = 0; |
502 | n = strtoimax (dot + 1, NULL, 10); | |
503 | owner->pid = | |
504 | ((0 <= n && n <= TYPE_MAXIMUM (pid_t) | |
505 | && (TYPE_MAXIMUM (pid_t) < INTMAX_MAX || errno != ERANGE)) | |
506 | ? n : 0); | |
507 | ||
508 | colon = strchr (dot + 1, ':'); | |
15e88d21 | 509 | /* After the `:', if there is one, comes the boot time. */ |
882f0d81 PE |
510 | n = 0; |
511 | if (colon) | |
512 | { | |
513 | errno = 0; | |
514 | n = strtoimax (colon + 1, NULL, 10); | |
515 | } | |
516 | owner->boot_time = | |
517 | ((0 <= n && n <= TYPE_MAXIMUM (time_t) | |
518 | && (TYPE_MAXIMUM (time_t) < INTMAX_MAX || errno != ERANGE)) | |
519 | ? n : 0); | |
32676c08 | 520 | |
8dbbc384 RS |
521 | /* The host is everything in between. */ |
522 | len = dot - at - 1; | |
23f86fce | 523 | owner->host = xmalloc (len + 1); |
882f0d81 | 524 | memcpy (owner->host, at + 1, len); |
8dbbc384 | 525 | owner->host[len] = 0; |
32676c08 | 526 | |
8dbbc384 | 527 | /* We're done looking at the link info. */ |
8654f9d7 | 528 | UNGCPRO; |
177c0ea7 | 529 | |
8dbbc384 | 530 | /* On current host? */ |
662c2ef2 | 531 | if (STRINGP (Fsystem_name ()) |
42a5b22f | 532 | && strcmp (owner->host, SSDATA (Fsystem_name ())) == 0) |
32676c08 | 533 | { |
8dbbc384 RS |
534 | if (owner->pid == getpid ()) |
535 | ret = 2; /* We own it. */ | |
72dcef0e | 536 | else if (owner->pid > 0 |
15e88d21 RS |
537 | && (kill (owner->pid, 0) >= 0 || errno == EPERM) |
538 | && (owner->boot_time == 0 | |
9177d978 | 539 | || within_one_second (owner->boot_time, get_boot_time ()))) |
8dbbc384 | 540 | ret = 1; /* An existing process on this machine owns it. */ |
8dbbc384 RS |
541 | /* The owner process is dead or has a strange pid (<=0), so try to |
542 | zap the lockfile. */ | |
72dcef0e | 543 | else if (unlink (lfname) < 0) |
8dbbc384 | 544 | ret = -1; |
72dcef0e RS |
545 | else |
546 | ret = 0; | |
32676c08 | 547 | } |
8dbbc384 RS |
548 | else |
549 | { /* If we wanted to support the check for stale locks on remote machines, | |
550 | here's where we'd do it. */ | |
551 | ret = 1; | |
552 | } | |
177c0ea7 | 553 | |
8dbbc384 | 554 | /* Avoid garbage. */ |
882f0d81 | 555 | if (owner == &local_owner || ret <= 0) |
8dbbc384 RS |
556 | { |
557 | FREE_LOCK_INFO (*owner); | |
558 | } | |
559 | return ret; | |
32676c08 JB |
560 | } |
561 | ||
8dbbc384 RS |
562 | \f |
563 | /* Lock the lock named LFNAME if possible. | |
564 | Return 0 in that case. | |
565 | Return positive if some other process owns the lock, and info about | |
566 | that process in CLASHER. | |
567 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 568 | |
8dbbc384 | 569 | static int |
971de7fb | 570 | lock_if_free (lock_info_type *clasher, register char *lfname) |
8dbbc384 | 571 | { |
f75d7a91 | 572 | while (! lock_file_1 (lfname, 0)) |
8dbbc384 RS |
573 | { |
574 | int locker; | |
e0e0205b | 575 | |
8dbbc384 RS |
576 | if (errno != EEXIST) |
577 | return -1; | |
177c0ea7 | 578 | |
8dbbc384 RS |
579 | locker = current_lock_owner (clasher, lfname); |
580 | if (locker == 2) | |
581 | { | |
582 | FREE_LOCK_INFO (*clasher); | |
583 | return 0; /* We ourselves locked it. */ | |
584 | } | |
585 | else if (locker == 1) | |
586 | return 1; /* Someone else has it. */ | |
5df0b2fa | 587 | else if (locker == -1) |
ae1ef097 | 588 | return -1; /* current_lock_owner returned strange error. */ |
8dbbc384 | 589 | |
cfc01fa7 | 590 | /* We deleted a stale lock; try again to lock the file. */ |
8dbbc384 RS |
591 | } |
592 | return 0; | |
8489eb67 RS |
593 | } |
594 | ||
8dbbc384 | 595 | /* lock_file locks file FN, |
8489eb67 RS |
596 | meaning it serves notice on the world that you intend to edit that file. |
597 | This should be done only when about to modify a file-visiting | |
598 | buffer previously unmodified. | |
8dbbc384 | 599 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
600 | as either the file is already locked, or the user has already |
601 | decided to go ahead without locking. | |
602 | ||
8dbbc384 | 603 | When this returns, either the lock is locked for us, |
8489eb67 RS |
604 | or the user has said to go ahead without locking. |
605 | ||
8dbbc384 | 606 | If the file is locked by someone else, this calls |
8489eb67 | 607 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 608 | the file name and info about the user who did the locking. |
8489eb67 RS |
609 | This function can signal an error, or return t meaning |
610 | take away the lock, or return nil meaning ignore the lock. */ | |
611 | ||
8489eb67 | 612 | void |
971de7fb | 613 | lock_file (Lisp_Object fn) |
8489eb67 | 614 | { |
f4a4528d | 615 | register Lisp_Object attack, orig_fn, encoded_fn; |
8dbbc384 | 616 | register char *lfname, *locker; |
b5cd1905 | 617 | ptrdiff_t locker_size; |
8dbbc384 | 618 | lock_info_type lock_info; |
a81d11a3 | 619 | printmax_t pid; |
3edc33a4 | 620 | struct gcpro gcpro1; |
b5cd1905 | 621 | USE_SAFE_ALLOCA; |
8489eb67 | 622 | |
836d29b3 DA |
623 | /* Don't do locking if the user has opted out. */ |
624 | if (! create_lockfiles) | |
625 | return; | |
626 | ||
33bae690 RS |
627 | /* Don't do locking while dumping Emacs. |
628 | Uncompressing wtmp files uses call-process, which does not work | |
629 | in an uninitialized Emacs. */ | |
630 | if (! NILP (Vpurify_flag)) | |
631 | return; | |
632 | ||
5383bc6d | 633 | orig_fn = fn; |
8af8a9ca | 634 | GCPRO1 (fn); |
1e89de84 | 635 | fn = Fexpand_file_name (fn, Qnil); |
343a2aef EZ |
636 | #ifdef WINDOWSNT |
637 | /* Ensure we have only '/' separators, to avoid problems with | |
638 | looking (inside fill_in_lock_file_name) for backslashes in file | |
639 | names encoded by some DBCS codepage. */ | |
640 | dostounix_filename (SSDATA (fn), 1); | |
641 | #endif | |
f4a4528d | 642 | encoded_fn = ENCODE_FILE (fn); |
1e89de84 | 643 | |
8dbbc384 | 644 | /* Create the name of the lock-file for file fn */ |
f4a4528d | 645 | MAKE_LOCK_NAME (lfname, encoded_fn); |
8489eb67 | 646 | |
32676c08 JB |
647 | /* See if this file is visited and has changed on disk since it was |
648 | visited. */ | |
8489eb67 | 649 | { |
a57bc488 | 650 | register Lisp_Object subject_buf; |
3036594f | 651 | |
5383bc6d | 652 | subject_buf = get_truename_buffer (orig_fn); |
3036594f | 653 | |
265a9e55 JB |
654 | if (!NILP (subject_buf) |
655 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
656 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 | 657 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
3036594f | 658 | |
8489eb67 | 659 | } |
8af8a9ca | 660 | UNGCPRO; |
8489eb67 RS |
661 | |
662 | /* Try to lock the lock. */ | |
8dbbc384 RS |
663 | if (lock_if_free (&lock_info, lfname) <= 0) |
664 | /* Return now if we have locked it, or if lock creation failed */ | |
8489eb67 RS |
665 | return; |
666 | ||
667 | /* Else consider breaking the lock */ | |
b5cd1905 PE |
668 | locker_size = (strlen (lock_info.user) + strlen (lock_info.host) |
669 | + INT_STRLEN_BOUND (printmax_t) | |
670 | + sizeof "@ (pid )"); | |
98c6f1e3 | 671 | locker = SAFE_ALLOCA (locker_size); |
882f0d81 | 672 | pid = lock_info.pid; |
b5cd1905 PE |
673 | esprintf (locker, "%s@%s (pid %"pMd")", |
674 | lock_info.user, lock_info.host, pid); | |
8dbbc384 | 675 | FREE_LOCK_INFO (lock_info); |
177c0ea7 | 676 | |
8dbbc384 | 677 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); |
b5cd1905 | 678 | SAFE_FREE (); |
265a9e55 | 679 | if (!NILP (attack)) |
8489eb67 RS |
680 | /* User says take the lock */ |
681 | { | |
8dbbc384 | 682 | lock_file_1 (lfname, 1); |
8489eb67 RS |
683 | return; |
684 | } | |
685 | /* User says ignore the lock */ | |
686 | } | |
687 | ||
8489eb67 | 688 | void |
971de7fb | 689 | unlock_file (register Lisp_Object fn) |
8489eb67 RS |
690 | { |
691 | register char *lfname; | |
692 | ||
1e89de84 | 693 | fn = Fexpand_file_name (fn, Qnil); |
88eace34 | 694 | fn = ENCODE_FILE (fn); |
1e89de84 | 695 | |
7b92975f | 696 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 697 | |
8dbbc384 | 698 | if (current_lock_owner (0, lfname) == 2) |
8489eb67 | 699 | unlink (lfname); |
8489eb67 RS |
700 | } |
701 | ||
702 | void | |
971de7fb | 703 | unlock_all_files (void) |
8489eb67 RS |
704 | { |
705 | register Lisp_Object tail; | |
706 | register struct buffer *b; | |
707 | ||
8e50cc2d | 708 | for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail)) |
8489eb67 | 709 | { |
03699b14 | 710 | b = XBUFFER (XCDR (XCAR (tail))); |
4b4deea2 | 711 | if (STRINGP (BVAR (b, file_truename)) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) |
1c343051 | 712 | { |
5e617bc2 | 713 | unlock_file (BVAR (b, file_truename)); |
1c343051 | 714 | } |
8489eb67 RS |
715 | } |
716 | } | |
8489eb67 RS |
717 | \f |
718 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
335c5470 PJ |
719 | 0, 1, 0, |
720 | doc: /* Lock FILE, if current buffer is modified. | |
721 | FILE defaults to current buffer's visited file, | |
722 | or else nothing is done if current buffer isn't visiting a file. */) | |
5842a27b | 723 | (Lisp_Object file) |
8489eb67 | 724 | { |
e9319ef2 | 725 | if (NILP (file)) |
4b4deea2 | 726 | file = BVAR (current_buffer, file_truename); |
8489eb67 | 727 | else |
b7826503 | 728 | CHECK_STRING (file); |
6a140159 | 729 | if (SAVE_MODIFF < MODIFF |
e9319ef2 EN |
730 | && !NILP (file)) |
731 | lock_file (file); | |
177c0ea7 | 732 | return Qnil; |
8489eb67 RS |
733 | } |
734 | ||
a7ca3326 | 735 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, |
335c5470 | 736 | 0, 0, 0, |
3bfb8921 RS |
737 | doc: /* Unlock the file visited in the current buffer. |
738 | If the buffer is not modified, this does nothing because the file | |
739 | should not be locked in that case. */) | |
5842a27b | 740 | (void) |
8489eb67 | 741 | { |
6a140159 | 742 | if (SAVE_MODIFF < MODIFF |
4b4deea2 TT |
743 | && STRINGP (BVAR (current_buffer, file_truename))) |
744 | unlock_file (BVAR (current_buffer, file_truename)); | |
8489eb67 RS |
745 | return Qnil; |
746 | } | |
747 | ||
8489eb67 RS |
748 | /* Unlock the file visited in buffer BUFFER. */ |
749 | ||
d07e0802 | 750 | void |
971de7fb | 751 | unlock_buffer (struct buffer *buffer) |
8489eb67 | 752 | { |
6a140159 | 753 | if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer) |
4b4deea2 TT |
754 | && STRINGP (BVAR (buffer, file_truename))) |
755 | unlock_file (BVAR (buffer, file_truename)); | |
8489eb67 RS |
756 | } |
757 | ||
8105cbf7 | 758 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 1, 1, 0, |
3bfb8921 RS |
759 | doc: /* Return a value indicating whether FILENAME is locked. |
760 | The value is nil if the FILENAME is not locked, | |
761 | t if it is locked by you, else a string saying which user has locked it. */) | |
5842a27b | 762 | (Lisp_Object filename) |
8489eb67 | 763 | { |
8dbbc384 | 764 | Lisp_Object ret; |
8489eb67 RS |
765 | register char *lfname; |
766 | int owner; | |
8dbbc384 | 767 | lock_info_type locker; |
8489eb67 | 768 | |
e9319ef2 | 769 | filename = Fexpand_file_name (filename, Qnil); |
8489eb67 | 770 | |
e9319ef2 | 771 | MAKE_LOCK_NAME (lfname, filename); |
8489eb67 | 772 | |
8dbbc384 | 773 | owner = current_lock_owner (&locker, lfname); |
8489eb67 | 774 | if (owner <= 0) |
8dbbc384 RS |
775 | ret = Qnil; |
776 | else if (owner == 2) | |
777 | ret = Qt; | |
778 | else | |
779 | ret = build_string (locker.user); | |
780 | ||
781 | if (owner > 0) | |
782 | FREE_LOCK_INFO (locker); | |
783 | ||
784 | return ret; | |
8489eb67 | 785 | } |
a3fd58aa | 786 | |
ffe75e6b EZ |
787 | #endif /* CLASH_DETECTION */ |
788 | ||
dfcf069d | 789 | void |
971de7fb | 790 | syms_of_filelock (void) |
8489eb67 | 791 | { |
29208e82 | 792 | DEFVAR_LISP ("temporary-file-directory", Vtemporary_file_directory, |
335c5470 | 793 | doc: /* The directory for writing temporary files. */); |
5f8d6a10 RS |
794 | Vtemporary_file_directory = Qnil; |
795 | ||
836d29b3 DA |
796 | DEFVAR_BOOL ("create-lockfiles", create_lockfiles, |
797 | doc: /* Non-nil means use lockfiles to avoid editing collisions. */); | |
798 | create_lockfiles = 1; | |
799 | ||
ffe75e6b | 800 | #ifdef CLASH_DETECTION |
8489eb67 RS |
801 | defsubr (&Sunlock_buffer); |
802 | defsubr (&Slock_buffer); | |
803 | defsubr (&Sfile_locked_p); | |
ffe75e6b | 804 | #endif |
8489eb67 | 805 | } |