3 * The Regents of the University of California. All rights reserved.
6 * John S. Dyson. All rights reserved.
8 * This code contains ideas from software contributed to Berkeley by
9 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
10 * System project at Carnegie-Mellon University.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
41 * $FreeBSD: src/sys/kern/kern_lock.c,v 1.31.2.3 2001/12/25 01:44:44 dillon Exp $
42 * $DragonFly: src/sys/kern/kern_lock.c,v 1.7 2003/09/25 23:52:28 dillon Exp $
47 #include <sys/param.h>
50 #include <sys/systm.h>
53 * Locking primitives implementation.
54 * Locks provide shared/exclusive sychronization.
57 #ifdef SIMPLELOCK_DEBUG
58 #define COUNT(td, x) (td)->td_locks += (x)
63 #define LOCK_WAIT_TIME 100
64 #define LOCK_SAMPLE_WAIT 7
66 #if defined(DIAGNOSTIC)
69 #define LOCK_INLINE __inline
72 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
73 LK_SHARE_NONZERO | LK_WAIT_NONZERO)
75 static int acquire(struct lock *lkp, int extflags, int wanted);
76 static int acquiredrain(struct lock *lkp, int extflags) ;
78 static LOCK_INLINE void
79 sharelock(struct lock *lkp, int incr) {
80 lkp->lk_flags |= LK_SHARE_NONZERO;
81 lkp->lk_sharecount += incr;
84 static LOCK_INLINE void
85 shareunlock(struct lock *lkp, int decr) {
87 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
89 if (lkp->lk_sharecount == decr) {
90 lkp->lk_flags &= ~LK_SHARE_NONZERO;
91 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
94 lkp->lk_sharecount = 0;
96 lkp->lk_sharecount -= decr;
101 acquire(struct lock *lkp, int extflags, int wanted)
105 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
109 if (((lkp->lk_flags | extflags) & LK_NOPAUSE) == 0) {
110 if ((lkp->lk_flags & wanted) == 0)
115 while ((lkp->lk_flags & wanted) != 0) {
116 lkp->lk_flags |= LK_WAIT_NONZERO;
118 lwkt_reltoken(&lkp->lk_interlock);
119 error = tsleep(lkp, lkp->lk_prio, lkp->lk_wmesg,
120 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
121 lwkt_gettoken(&lkp->lk_interlock);
122 if (lkp->lk_waitcount == 1) {
123 lkp->lk_flags &= ~LK_WAIT_NONZERO;
124 lkp->lk_waitcount = 0;
132 if (extflags & LK_SLEEPFAIL) {
142 * Set, change, or release a lock.
144 * Shared requests increment the shared count. Exclusive requests set the
145 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
146 * accepted shared locks and shared-to-exclusive upgrades to go away.
150 lockmgr(struct lock *lkp, u_int flags, struct lwkt_token *interlkp,
153 debuglockmgr(struct lock *lkp, u_int flags, struct lwkt_token *interlkp,
154 struct thread *td, const char *name, const char *file, int line)
163 if ((flags & LK_NOWAIT) == 0 && (flags & LK_TYPE_MASK) != LK_RELEASE && didpanic == 0) {
165 if (mycpu->gd_intr_nesting_level) {
166 /* didpanic = 1; printf below will be a panic soon */
167 printf("lockmgr %s from %p: called from FASTint\n",
168 lkp->lk_wmesg, ((int **)&lkp)[-1]);
171 if (mycpu->gd_intr_nesting_level) {
172 /* didpanic = 1; printf below will be a panic soon */
173 printf("lockmgr %s from %s:%d: called from FASTint\n",
174 lkp->lk_wmesg, file, line);
179 lwkt_gettoken(&lkp->lk_interlock);
180 if (flags & LK_INTERLOCK)
181 lwkt_reltoken(interlkp);
183 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
185 switch (flags & LK_TYPE_MASK) {
189 * If we are not the exclusive lock holder, we have to block
190 * while there is an exclusive lock holder or while an
191 * exclusive lock request or upgrade request is in progress.
193 * However, if P_DEADLKTREAT is set, we override exclusive
194 * lock requests or upgrade requests ( but not the exclusive
197 if (lkp->lk_lockholder != td) {
198 if (td->td_flags & TDF_DEADLKTREAT) {
208 LK_HAVE_EXCL | LK_WANT_EXCL |
219 * We hold an exclusive lock, so downgrade it to shared.
220 * An alternative would be to fail with EDEADLK.
224 /* fall into downgrade */
227 if (lkp->lk_lockholder != td || lkp->lk_exclusivecount == 0)
228 panic("lockmgr: not holding exclusive lock");
229 sharelock(lkp, lkp->lk_exclusivecount);
230 lkp->lk_exclusivecount = 0;
231 lkp->lk_flags &= ~LK_HAVE_EXCL;
232 lkp->lk_lockholder = LK_NOTHREAD;
233 if (lkp->lk_waitcount)
239 * If another process is ahead of us to get an upgrade,
240 * then we want to fail rather than have an intervening
243 if (lkp->lk_flags & LK_WANT_UPGRADE) {
249 /* fall into normal upgrade */
253 * Upgrade a shared lock to an exclusive one. If another
254 * shared lock has already requested an upgrade to an
255 * exclusive lock, our shared lock is released and an
256 * exclusive lock is requested (which will be granted
257 * after the upgrade). If we return an error, the file
258 * will always be unlocked.
260 if ((lkp->lk_lockholder == td) || (lkp->lk_sharecount <= 0))
261 panic("lockmgr: upgrade exclusive lock");
265 * If we are just polling, check to see if we will block.
267 if ((extflags & LK_NOWAIT) &&
268 ((lkp->lk_flags & LK_WANT_UPGRADE) ||
269 lkp->lk_sharecount > 1)) {
273 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
275 * We are first shared lock to request an upgrade, so
276 * request upgrade and wait for the shared count to
277 * drop to zero, then take exclusive lock.
279 lkp->lk_flags |= LK_WANT_UPGRADE;
280 error = acquire(lkp, extflags, LK_SHARE_NONZERO);
281 lkp->lk_flags &= ~LK_WANT_UPGRADE;
285 lkp->lk_flags |= LK_HAVE_EXCL;
286 lkp->lk_lockholder = td;
287 if (lkp->lk_exclusivecount != 0)
288 panic("lockmgr: non-zero exclusive count");
289 lkp->lk_exclusivecount = 1;
290 #if defined(DEBUG_LOCKS)
291 lkp->lk_filename = file;
292 lkp->lk_lineno = line;
293 lkp->lk_lockername = name;
299 * Someone else has requested upgrade. Release our shared
300 * lock, awaken upgrade requestor if we are the last shared
301 * lock, then request an exclusive lock.
303 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
306 /* fall into exclusive request */
309 if (lkp->lk_lockholder == td && td != LK_KERNTHREAD) {
313 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
314 panic("lockmgr: locking against myself");
315 if ((extflags & LK_CANRECURSE) != 0) {
316 lkp->lk_exclusivecount++;
322 * If we are just polling, check to see if we will sleep.
324 if ((extflags & LK_NOWAIT) &&
325 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
330 * Try to acquire the want_exclusive flag.
332 error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
335 lkp->lk_flags |= LK_WANT_EXCL;
337 * Wait for shared locks and upgrades to finish.
339 error = acquire(lkp, extflags, LK_WANT_UPGRADE | LK_SHARE_NONZERO);
340 lkp->lk_flags &= ~LK_WANT_EXCL;
343 lkp->lk_flags |= LK_HAVE_EXCL;
344 lkp->lk_lockholder = td;
345 if (lkp->lk_exclusivecount != 0)
346 panic("lockmgr: non-zero exclusive count");
347 lkp->lk_exclusivecount = 1;
348 #if defined(DEBUG_LOCKS)
349 lkp->lk_filename = file;
350 lkp->lk_lineno = line;
351 lkp->lk_lockername = name;
357 if (lkp->lk_exclusivecount != 0) {
358 if (lkp->lk_lockholder != td &&
359 lkp->lk_lockholder != LK_KERNTHREAD) {
360 panic("lockmgr: pid %d, not %s thr %p unlocking",
361 (td->td_proc ? td->td_proc->p_pid : -99),
362 "exclusive lock holder",
365 if (lkp->lk_lockholder != LK_KERNTHREAD) {
368 if (lkp->lk_exclusivecount == 1) {
369 lkp->lk_flags &= ~LK_HAVE_EXCL;
370 lkp->lk_lockholder = LK_NOTHREAD;
371 lkp->lk_exclusivecount = 0;
373 lkp->lk_exclusivecount--;
375 } else if (lkp->lk_flags & LK_SHARE_NONZERO) {
379 if (lkp->lk_flags & LK_WAIT_NONZERO)
385 * Check that we do not already hold the lock, as it can
386 * never drain if we do. Unfortunately, we have no way to
387 * check for holding a shared lock, but at least we can
388 * check for an exclusive one.
390 if (lkp->lk_lockholder == td)
391 panic("lockmgr: draining against myself");
393 error = acquiredrain(lkp, extflags);
396 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
397 lkp->lk_lockholder = td;
398 lkp->lk_exclusivecount = 1;
399 #if defined(DEBUG_LOCKS)
400 lkp->lk_filename = file;
401 lkp->lk_lineno = line;
402 lkp->lk_lockername = name;
408 lwkt_reltoken(&lkp->lk_interlock);
409 panic("lockmgr: unknown locktype request %d",
410 flags & LK_TYPE_MASK);
413 if ((lkp->lk_flags & LK_WAITDRAIN) &&
414 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
415 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
416 lkp->lk_flags &= ~LK_WAITDRAIN;
417 wakeup((void *)&lkp->lk_flags);
419 lwkt_reltoken(&lkp->lk_interlock);
424 acquiredrain(struct lock *lkp, int extflags)
428 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
432 if ((lkp->lk_flags & LK_ALL) == 0)
435 while (lkp->lk_flags & LK_ALL) {
436 lkp->lk_flags |= LK_WAITDRAIN;
437 lwkt_reltoken(&lkp->lk_interlock);
438 error = tsleep(&lkp->lk_flags, lkp->lk_prio,
440 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
441 lwkt_gettoken(&lkp->lk_interlock);
444 if (extflags & LK_SLEEPFAIL) {
452 * Initialize a lock; required before use.
455 lockinit(lkp, prio, wmesg, timo, flags)
462 lwkt_inittoken(&lkp->lk_interlock);
463 lkp->lk_flags = (flags & LK_EXTFLG_MASK);
464 lkp->lk_sharecount = 0;
465 lkp->lk_waitcount = 0;
466 lkp->lk_exclusivecount = 0;
468 lkp->lk_wmesg = wmesg;
470 lkp->lk_lockholder = LK_NOTHREAD;
474 * Determine the status of a lock.
477 lockstatus(struct lock *lkp, struct thread *td)
481 lwkt_gettoken(&lkp->lk_interlock);
482 if (lkp->lk_exclusivecount != 0) {
483 if (td == NULL || lkp->lk_lockholder == td)
484 lock_type = LK_EXCLUSIVE;
486 lock_type = LK_EXCLOTHER;
487 } else if (lkp->lk_sharecount != 0) {
488 lock_type = LK_SHARED;
490 lwkt_reltoken(&lkp->lk_interlock);
495 * Determine the number of holders of a lock.
503 lwkt_gettoken(&lkp->lk_interlock);
504 count = lkp->lk_exclusivecount + lkp->lk_sharecount;
505 lwkt_reltoken(&lkp->lk_interlock);
510 * Print out information about state of a lock. Used by VOP_PRINT
511 * routines to display status about contained locks.
514 lockmgr_printinfo(lkp)
517 struct thread *td = lkp->lk_lockholder;
520 if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD)
525 if (lkp->lk_sharecount)
526 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
528 else if (lkp->lk_flags & LK_HAVE_EXCL)
529 printf(" lock type %s: EXCL (count %d) by td %p pid %d",
530 lkp->lk_wmesg, lkp->lk_exclusivecount, td,
532 if (lkp->lk_waitcount > 0)
533 printf(" with %d pending", lkp->lk_waitcount);