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
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16 * notice, this list of conditions and the following disclaimer.
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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.
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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 1.12 2004/11/09 17:41:30 dillon Exp $
47 #include <sys/param.h>
48 #include <sys/systm.h>
49 #include <sys/kernel.h>
52 #include <sys/sysctl.h>
55 * 0: no warnings, 1: warnings, 2: panic
57 static int lockmgr_from_int = 1;
58 SYSCTL_INT(_debug, OID_AUTO, lockmgr_from_int, CTLFLAG_RW, &lockmgr_from_int, 0, "");
61 * Locking primitives implementation.
62 * Locks provide shared/exclusive sychronization.
65 #ifdef SIMPLELOCK_DEBUG
66 #define COUNT(td, x) (td)->td_locks += (x)
71 #define LOCK_WAIT_TIME 100
72 #define LOCK_SAMPLE_WAIT 7
74 #if defined(DIAGNOSTIC)
77 #define LOCK_INLINE __inline
80 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
81 LK_SHARE_NONZERO | LK_WAIT_NONZERO)
83 static int acquire(struct lock *lkp, int extflags, int wanted);
84 static int acquiredrain(struct lock *lkp, int extflags) ;
86 static LOCK_INLINE void
87 sharelock(struct lock *lkp, int incr) {
88 lkp->lk_flags |= LK_SHARE_NONZERO;
89 lkp->lk_sharecount += incr;
92 static LOCK_INLINE void
93 shareunlock(struct lock *lkp, int decr) {
95 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
97 if (lkp->lk_sharecount == decr) {
98 lkp->lk_flags &= ~LK_SHARE_NONZERO;
99 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
102 lkp->lk_sharecount = 0;
104 lkp->lk_sharecount -= decr;
109 acquire(struct lock *lkp, int extflags, int wanted)
113 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
117 if (((lkp->lk_flags | extflags) & LK_NOPAUSE) == 0) {
118 if ((lkp->lk_flags & wanted) == 0)
123 while ((lkp->lk_flags & wanted) != 0) {
124 lkp->lk_flags |= LK_WAIT_NONZERO;
126 /* note: serialization lock is held through tsleep */
127 error = tsleep(lkp, lkp->lk_prio, lkp->lk_wmesg,
128 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
129 if (lkp->lk_waitcount == 1) {
130 lkp->lk_flags &= ~LK_WAIT_NONZERO;
131 lkp->lk_waitcount = 0;
139 if (extflags & LK_SLEEPFAIL) {
149 * Set, change, or release a lock.
151 * Shared requests increment the shared count. Exclusive requests set the
152 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
153 * accepted shared locks and shared-to-exclusive upgrades to go away.
157 lockmgr(struct lock *lkp, u_int flags, lwkt_tokref_t interlkp,
160 debuglockmgr(struct lock *lkp, u_int flags, lwkt_tokref_t interlkp,
161 struct thread *td, const char *name, const char *file, int line)
171 if (lockmgr_from_int && mycpu->gd_intr_nesting_level &&
172 (flags & LK_NOWAIT) == 0 &&
173 (flags & LK_TYPE_MASK) != LK_RELEASE && didpanic == 0) {
175 if (lockmgr_from_int == 2) {
178 "lockmgr %s from %p: called from interrupt",
179 lkp->lk_wmesg, ((int **)&lkp)[-1]);
183 "lockmgr %s from %p: called from interrupt\n",
184 lkp->lk_wmesg, ((int **)&lkp)[-1]);
187 if (lockmgr_from_int == 2) {
190 "lockmgr %s from %s:%d: called from interrupt",
191 lkp->lk_wmesg, file, line);
195 "lockmgr %s from %s:%d: called from interrupt\n",
196 lkp->lk_wmesg, file, line);
201 lwkt_gettoken(&ilock, &lkp->lk_interlock);
202 if (flags & LK_INTERLOCK)
203 lwkt_reltoken(interlkp);
205 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
207 switch (flags & LK_TYPE_MASK) {
211 * If we are not the exclusive lock holder, we have to block
212 * while there is an exclusive lock holder or while an
213 * exclusive lock request or upgrade request is in progress.
215 * However, if P_DEADLKTREAT is set, we override exclusive
216 * lock requests or upgrade requests ( but not the exclusive
219 if (lkp->lk_lockholder != td) {
220 if (td->td_flags & TDF_DEADLKTREAT) {
230 LK_HAVE_EXCL | LK_WANT_EXCL |
241 * We hold an exclusive lock, so downgrade it to shared.
242 * An alternative would be to fail with EDEADLK.
246 /* fall into downgrade */
249 if (lkp->lk_lockholder != td || lkp->lk_exclusivecount == 0)
250 panic("lockmgr: not holding exclusive lock");
251 sharelock(lkp, lkp->lk_exclusivecount);
252 lkp->lk_exclusivecount = 0;
253 lkp->lk_flags &= ~LK_HAVE_EXCL;
254 lkp->lk_lockholder = LK_NOTHREAD;
255 if (lkp->lk_waitcount)
261 * If another process is ahead of us to get an upgrade,
262 * then we want to fail rather than have an intervening
265 if (lkp->lk_flags & LK_WANT_UPGRADE) {
271 /* fall into normal upgrade */
275 * Upgrade a shared lock to an exclusive one. If another
276 * shared lock has already requested an upgrade to an
277 * exclusive lock, our shared lock is released and an
278 * exclusive lock is requested (which will be granted
279 * after the upgrade). If we return an error, the file
280 * will always be unlocked.
282 if ((lkp->lk_lockholder == td) || (lkp->lk_sharecount <= 0))
283 panic("lockmgr: upgrade exclusive lock");
287 * If we are just polling, check to see if we will block.
289 if ((extflags & LK_NOWAIT) &&
290 ((lkp->lk_flags & LK_WANT_UPGRADE) ||
291 lkp->lk_sharecount > 1)) {
295 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
297 * We are first shared lock to request an upgrade, so
298 * request upgrade and wait for the shared count to
299 * drop to zero, then take exclusive lock.
301 lkp->lk_flags |= LK_WANT_UPGRADE;
302 error = acquire(lkp, extflags, LK_SHARE_NONZERO);
303 lkp->lk_flags &= ~LK_WANT_UPGRADE;
307 lkp->lk_flags |= LK_HAVE_EXCL;
308 lkp->lk_lockholder = td;
309 if (lkp->lk_exclusivecount != 0)
310 panic("lockmgr: non-zero exclusive count");
311 lkp->lk_exclusivecount = 1;
312 #if defined(DEBUG_LOCKS)
313 lkp->lk_filename = file;
314 lkp->lk_lineno = line;
315 lkp->lk_lockername = name;
321 * Someone else has requested upgrade. Release our shared
322 * lock, awaken upgrade requestor if we are the last shared
323 * lock, then request an exclusive lock.
325 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
328 /* fall into exclusive request */
331 if (lkp->lk_lockholder == td && td != LK_KERNTHREAD) {
335 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
336 panic("lockmgr: locking against myself");
337 if ((extflags & LK_CANRECURSE) != 0) {
338 lkp->lk_exclusivecount++;
344 * If we are just polling, check to see if we will sleep.
346 if ((extflags & LK_NOWAIT) &&
347 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
352 * Try to acquire the want_exclusive flag.
354 error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
357 lkp->lk_flags |= LK_WANT_EXCL;
359 * Wait for shared locks and upgrades to finish.
361 error = acquire(lkp, extflags, LK_WANT_UPGRADE | LK_SHARE_NONZERO);
362 lkp->lk_flags &= ~LK_WANT_EXCL;
365 lkp->lk_flags |= LK_HAVE_EXCL;
366 lkp->lk_lockholder = td;
367 if (lkp->lk_exclusivecount != 0)
368 panic("lockmgr: non-zero exclusive count");
369 lkp->lk_exclusivecount = 1;
370 #if defined(DEBUG_LOCKS)
371 lkp->lk_filename = file;
372 lkp->lk_lineno = line;
373 lkp->lk_lockername = name;
379 if (lkp->lk_exclusivecount != 0) {
380 if (lkp->lk_lockholder != td &&
381 lkp->lk_lockholder != LK_KERNTHREAD) {
382 panic("lockmgr: pid %d, not %s thr %p unlocking",
383 (td->td_proc ? td->td_proc->p_pid : -99),
384 "exclusive lock holder",
387 if (lkp->lk_lockholder != LK_KERNTHREAD) {
390 if (lkp->lk_exclusivecount == 1) {
391 lkp->lk_flags &= ~LK_HAVE_EXCL;
392 lkp->lk_lockholder = LK_NOTHREAD;
393 lkp->lk_exclusivecount = 0;
395 lkp->lk_exclusivecount--;
397 } else if (lkp->lk_flags & LK_SHARE_NONZERO) {
401 if (lkp->lk_flags & LK_WAIT_NONZERO)
407 * Check that we do not already hold the lock, as it can
408 * never drain if we do. Unfortunately, we have no way to
409 * check for holding a shared lock, but at least we can
410 * check for an exclusive one.
412 if (lkp->lk_lockholder == td)
413 panic("lockmgr: draining against myself");
415 error = acquiredrain(lkp, extflags);
418 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
419 lkp->lk_lockholder = td;
420 lkp->lk_exclusivecount = 1;
421 #if defined(DEBUG_LOCKS)
422 lkp->lk_filename = file;
423 lkp->lk_lineno = line;
424 lkp->lk_lockername = name;
430 lwkt_reltoken(&ilock);
431 panic("lockmgr: unknown locktype request %d",
432 flags & LK_TYPE_MASK);
435 if ((lkp->lk_flags & LK_WAITDRAIN) &&
436 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
437 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
438 lkp->lk_flags &= ~LK_WAITDRAIN;
439 wakeup((void *)&lkp->lk_flags);
441 lwkt_reltoken(&ilock);
446 acquiredrain(struct lock *lkp, int extflags)
450 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
454 if ((lkp->lk_flags & LK_ALL) == 0)
457 while (lkp->lk_flags & LK_ALL) {
458 lkp->lk_flags |= LK_WAITDRAIN;
459 /* interlock serialization held through tsleep */
460 error = tsleep(&lkp->lk_flags, lkp->lk_prio,
462 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
465 if (extflags & LK_SLEEPFAIL) {
473 * Initialize a lock; required before use.
476 lockinit(struct lock *lkp, int prio, char *wmesg, int timo, int flags)
478 lwkt_token_init(&lkp->lk_interlock);
479 lkp->lk_flags = (flags & LK_EXTFLG_MASK);
480 lkp->lk_sharecount = 0;
481 lkp->lk_waitcount = 0;
482 lkp->lk_exclusivecount = 0;
484 lkp->lk_wmesg = wmesg;
486 lkp->lk_lockholder = LK_NOTHREAD;
490 * Reinitialize a lock that is being reused for a different purpose, but
491 * which may have pending (blocked) threads sitting on it. The caller
492 * must already hold the interlock.
495 lockreinit(struct lock *lkp, int prio, char *wmesg, int timo, int flags)
497 lkp->lk_flags = (lkp->lk_flags & ~(LK_EXTFLG_MASK|LK_DRAINING)) |
498 (flags & LK_EXTFLG_MASK);
500 lkp->lk_wmesg = wmesg;
505 * Determine the status of a lock.
508 lockstatus(struct lock *lkp, struct thread *td)
513 lwkt_gettoken(&ilock, &lkp->lk_interlock);
514 if (lkp->lk_exclusivecount != 0) {
515 if (td == NULL || lkp->lk_lockholder == td)
516 lock_type = LK_EXCLUSIVE;
518 lock_type = LK_EXCLOTHER;
519 } else if (lkp->lk_sharecount != 0) {
520 lock_type = LK_SHARED;
522 lwkt_reltoken(&ilock);
527 * Determine the number of holders of a lock.
529 * The non-blocking version can usually be used for assertions.
538 lwkt_gettoken(&ilock, &lkp->lk_interlock);
539 count = lkp->lk_exclusivecount + lkp->lk_sharecount;
540 lwkt_reltoken(&ilock);
548 return (lkp->lk_exclusivecount + lkp->lk_sharecount);
552 * Print out information about state of a lock. Used by VOP_PRINT
553 * routines to display status about contained locks.
556 lockmgr_printinfo(lkp)
559 struct thread *td = lkp->lk_lockholder;
562 if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD)
567 if (lkp->lk_sharecount)
568 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
570 else if (lkp->lk_flags & LK_HAVE_EXCL)
571 printf(" lock type %s: EXCL (count %d) by td %p pid %d",
572 lkp->lk_wmesg, lkp->lk_exclusivecount, td,
574 if (lkp->lk_waitcount > 0)
575 printf(" with %d pending", lkp->lk_waitcount);