xref: /freebsd/sys/sys/mutex.h (revision 38069501)
1 /*-
2  * Copyright (c) 1997 Berkeley Software Design, Inc. All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  * 3. Berkeley Software Design Inc's name may not be used to endorse or
13  *    promote products derived from this software without specific prior
14  *    written permission.
15  *
16  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  *
28  *	from BSDI $Id: mutex.h,v 2.7.2.35 2000/04/27 03:10:26 cp Exp $
29  * $FreeBSD$
30  */
31 
32 #ifndef _SYS_MUTEX_H_
33 #define _SYS_MUTEX_H_
34 
35 #include <sys/queue.h>
36 #include <sys/_lock.h>
37 #include <sys/_mutex.h>
38 
39 #ifdef _KERNEL
40 #include <sys/pcpu.h>
41 #include <sys/lock_profile.h>
42 #include <sys/lockstat.h>
43 #include <machine/atomic.h>
44 #include <machine/cpufunc.h>
45 
46 /*
47  * Mutex types and options passed to mtx_init().  MTX_QUIET and MTX_DUPOK
48  * can also be passed in.
49  */
50 #define	MTX_DEF		0x00000000	/* DEFAULT (sleep) lock */
51 #define MTX_SPIN	0x00000001	/* Spin lock (disables interrupts) */
52 #define MTX_RECURSE	0x00000004	/* Option: lock allowed to recurse */
53 #define	MTX_NOWITNESS	0x00000008	/* Don't do any witness checking. */
54 #define MTX_NOPROFILE   0x00000020	/* Don't profile this lock */
55 #define	MTX_NEW		0x00000040	/* Don't check for double-init */
56 
57 /*
58  * Option flags passed to certain lock/unlock routines, through the use
59  * of corresponding mtx_{lock,unlock}_flags() interface macros.
60  */
61 #define	MTX_QUIET	LOP_QUIET	/* Don't log a mutex event */
62 #define	MTX_DUPOK	LOP_DUPOK	/* Don't log a duplicate acquire */
63 
64 /*
65  * State bits kept in mutex->mtx_lock, for the DEFAULT lock type. None of this,
66  * with the exception of MTX_UNOWNED, applies to spin locks.
67  */
68 #define	MTX_UNOWNED	0x00000000	/* Cookie for free mutex */
69 #define	MTX_RECURSED	0x00000001	/* lock recursed (for MTX_DEF only) */
70 #define	MTX_CONTESTED	0x00000002	/* lock contested (for MTX_DEF only) */
71 #define	MTX_DESTROYED	0x00000004	/* lock destroyed */
72 #define	MTX_FLAGMASK	(MTX_RECURSED | MTX_CONTESTED | MTX_DESTROYED)
73 
74 /*
75  * Prototypes
76  *
77  * NOTE: Functions prepended with `_' (underscore) are exported to other parts
78  *	 of the kernel via macros, thus allowing us to use the cpp LOCK_FILE
79  *	 and LOCK_LINE or for hiding the lock cookie crunching to the
80  *	 consumers. These functions should not be called directly by any
81  *	 code using the API. Their macros cover their functionality.
82  *	 Functions with a `_' suffix are the entrypoint for the common
83  *	 KPI covering both compat shims and fast path case.  These can be
84  *	 used by consumers willing to pass options, file and line
85  *	 informations, in an option-independent way.
86  *
87  * [See below for descriptions]
88  *
89  */
90 void	_mtx_init(volatile uintptr_t *c, const char *name, const char *type,
91 	    int opts);
92 void	_mtx_destroy(volatile uintptr_t *c);
93 void	mtx_sysinit(void *arg);
94 int	_mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file,
95 	    int line);
96 void	mutex_init(void);
97 #if LOCK_DEBUG > 0
98 void	__mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, int opts,
99 	    const char *file, int line);
100 void	__mtx_unlock_sleep(volatile uintptr_t *c, int opts, const char *file,
101 	    int line);
102 #else
103 void	__mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v);
104 void	__mtx_unlock_sleep(volatile uintptr_t *c);
105 #endif
106 
107 #ifdef SMP
108 #if LOCK_DEBUG > 0
109 void	_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts,
110 	    const char *file, int line);
111 #else
112 void	_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v);
113 #endif
114 #endif
115 void	__mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file,
116 	    int line);
117 void	__mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file,
118 	    int line);
119 void	__mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
120 	     int line);
121 int	__mtx_trylock_spin_flags(volatile uintptr_t *c, int opts,
122 	     const char *file, int line);
123 void	__mtx_unlock_spin_flags(volatile uintptr_t *c, int opts,
124 	    const char *file, int line);
125 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
126 void	__mtx_assert(const volatile uintptr_t *c, int what, const char *file,
127 	    int line);
128 #endif
129 void	thread_lock_flags_(struct thread *, int, const char *, int);
130 #if LOCK_DEBUG > 0
131 void	_thread_lock(struct thread *td, int opts, const char *file, int line);
132 #else
133 void	_thread_lock(struct thread *);
134 #endif
135 
136 #if defined(LOCK_PROFILING) || defined(KLD_MODULE)
137 #define	thread_lock(tdp)						\
138 	thread_lock_flags_((tdp), 0, __FILE__, __LINE__)
139 #elif LOCK_DEBUG > 0
140 #define	thread_lock(tdp)						\
141 	_thread_lock((tdp), 0, __FILE__, __LINE__)
142 #else
143 #define	thread_lock(tdp)						\
144 	_thread_lock((tdp))
145 #endif
146 
147 #define	thread_lock_flags(tdp, opt)					\
148 	thread_lock_flags_((tdp), (opt), __FILE__, __LINE__)
149 #define	thread_unlock(tdp)						\
150        mtx_unlock_spin((tdp)->td_lock)
151 
152 /*
153  * Top-level macros to provide lock cookie once the actual mtx is passed.
154  * They will also prevent passing a malformed object to the mtx KPI by
155  * failing compilation as the mtx_lock reserved member will not be found.
156  */
157 #define	mtx_init(m, n, t, o)						\
158 	_mtx_init(&(m)->mtx_lock, n, t, o)
159 #define	mtx_destroy(m)							\
160 	_mtx_destroy(&(m)->mtx_lock)
161 #define	mtx_trylock_flags_(m, o, f, l)					\
162 	_mtx_trylock_flags_(&(m)->mtx_lock, o, f, l)
163 #if LOCK_DEBUG > 0
164 #define	_mtx_lock_sleep(m, v, o, f, l)					\
165 	__mtx_lock_sleep(&(m)->mtx_lock, v, o, f, l)
166 #define	_mtx_unlock_sleep(m, o, f, l)					\
167 	__mtx_unlock_sleep(&(m)->mtx_lock, o, f, l)
168 #else
169 #define	_mtx_lock_sleep(m, v, o, f, l)					\
170 	__mtx_lock_sleep(&(m)->mtx_lock, v)
171 #define	_mtx_unlock_sleep(m, o, f, l)					\
172 	__mtx_unlock_sleep(&(m)->mtx_lock)
173 #endif
174 #ifdef SMP
175 #if LOCK_DEBUG > 0
176 #define	_mtx_lock_spin(m, v, o, f, l)					\
177 	_mtx_lock_spin_cookie(&(m)->mtx_lock, v, o, f, l)
178 #else
179 #define	_mtx_lock_spin(m, v, o, f, l)					\
180 	_mtx_lock_spin_cookie(&(m)->mtx_lock, v)
181 #endif
182 #endif
183 #define	_mtx_lock_flags(m, o, f, l)					\
184 	__mtx_lock_flags(&(m)->mtx_lock, o, f, l)
185 #define	_mtx_unlock_flags(m, o, f, l)					\
186 	__mtx_unlock_flags(&(m)->mtx_lock, o, f, l)
187 #define	_mtx_lock_spin_flags(m, o, f, l)				\
188 	__mtx_lock_spin_flags(&(m)->mtx_lock, o, f, l)
189 #define	_mtx_trylock_spin_flags(m, o, f, l)				\
190 	__mtx_trylock_spin_flags(&(m)->mtx_lock, o, f, l)
191 #define	_mtx_unlock_spin_flags(m, o, f, l)				\
192 	__mtx_unlock_spin_flags(&(m)->mtx_lock, o, f, l)
193 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
194 #define	_mtx_assert(m, w, f, l)						\
195 	__mtx_assert(&(m)->mtx_lock, w, f, l)
196 #endif
197 
198 #define	mtx_recurse	lock_object.lo_data
199 
200 /* Very simple operations on mtx_lock. */
201 
202 /* Try to obtain mtx_lock once. */
203 #define _mtx_obtain_lock(mp, tid)					\
204 	atomic_cmpset_acq_ptr(&(mp)->mtx_lock, MTX_UNOWNED, (tid))
205 
206 #define _mtx_obtain_lock_fetch(mp, vp, tid)				\
207 	atomic_fcmpset_acq_ptr(&(mp)->mtx_lock, vp, (tid))
208 
209 /* Try to release mtx_lock if it is unrecursed and uncontested. */
210 #define _mtx_release_lock(mp, tid)					\
211 	atomic_cmpset_rel_ptr(&(mp)->mtx_lock, (tid), MTX_UNOWNED)
212 
213 /* Release mtx_lock quickly, assuming we own it. */
214 #define _mtx_release_lock_quick(mp)					\
215 	atomic_store_rel_ptr(&(mp)->mtx_lock, MTX_UNOWNED)
216 
217 /*
218  * Full lock operations that are suitable to be inlined in non-debug
219  * kernels.  If the lock cannot be acquired or released trivially then
220  * the work is deferred to another function.
221  */
222 
223 /* Lock a normal mutex. */
224 #define __mtx_lock(mp, tid, opts, file, line) do {			\
225 	uintptr_t _tid = (uintptr_t)(tid);				\
226 	uintptr_t _v = MTX_UNOWNED;					\
227 									\
228 	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(adaptive__acquire) ||\
229 	    !_mtx_obtain_lock_fetch((mp), &_v, _tid)))			\
230 		_mtx_lock_sleep((mp), _v, (opts), (file), (line));	\
231 } while (0)
232 
233 /*
234  * Lock a spin mutex.  For spinlocks, we handle recursion inline (it
235  * turns out that function calls can be significantly expensive on
236  * some architectures).  Since spin locks are not _too_ common,
237  * inlining this code is not too big a deal.
238  */
239 #ifdef SMP
240 #define __mtx_lock_spin(mp, tid, opts, file, line) do {			\
241 	uintptr_t _tid = (uintptr_t)(tid);				\
242 	uintptr_t _v = MTX_UNOWNED;					\
243 									\
244 	spinlock_enter();						\
245 	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire) ||	\
246 	    !_mtx_obtain_lock_fetch((mp), &_v, _tid))) 			\
247 		_mtx_lock_spin((mp), _v, (opts), (file), (line)); 	\
248 } while (0)
249 #define __mtx_trylock_spin(mp, tid, opts, file, line) __extension__  ({	\
250 	uintptr_t _tid = (uintptr_t)(tid);				\
251 	int _ret;							\
252 									\
253 	spinlock_enter();						\
254 	if (((mp)->mtx_lock != MTX_UNOWNED || !_mtx_obtain_lock((mp), _tid))) {\
255 		spinlock_exit();					\
256 		_ret = 0;						\
257 	} else {							\
258 		LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire,	\
259 		    mp, 0, 0, file, line);				\
260 		_ret = 1;						\
261 	}								\
262 	_ret;								\
263 })
264 #else /* SMP */
265 #define __mtx_lock_spin(mp, tid, opts, file, line) do {			\
266 	uintptr_t _tid = (uintptr_t)(tid);				\
267 									\
268 	spinlock_enter();						\
269 	if ((mp)->mtx_lock == _tid)					\
270 		(mp)->mtx_recurse++;					\
271 	else {								\
272 		KASSERT((mp)->mtx_lock == MTX_UNOWNED, ("corrupt spinlock")); \
273 		(mp)->mtx_lock = _tid;					\
274 	}								\
275 } while (0)
276 #define __mtx_trylock_spin(mp, tid, opts, file, line) __extension__  ({	\
277 	uintptr_t _tid = (uintptr_t)(tid);				\
278 	int _ret;							\
279 									\
280 	spinlock_enter();						\
281 	if ((mp)->mtx_lock != MTX_UNOWNED) {				\
282 		spinlock_exit();					\
283 		_ret = 0;						\
284 	} else {							\
285 		(mp)->mtx_lock = _tid;					\
286 		_ret = 1;						\
287 	}								\
288 	_ret;								\
289 })
290 #endif /* SMP */
291 
292 /* Unlock a normal mutex. */
293 #define __mtx_unlock(mp, tid, opts, file, line) do {			\
294 	uintptr_t _tid = (uintptr_t)(tid);				\
295 									\
296 	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(adaptive__release) ||\
297 	    !_mtx_release_lock((mp), _tid)))				\
298 		_mtx_unlock_sleep((mp), (opts), (file), (line));	\
299 } while (0)
300 
301 /*
302  * Unlock a spin mutex.  For spinlocks, we can handle everything
303  * inline, as it's pretty simple and a function call would be too
304  * expensive (at least on some architectures).  Since spin locks are
305  * not _too_ common, inlining this code is not too big a deal.
306  *
307  * Since we always perform a spinlock_enter() when attempting to acquire a
308  * spin lock, we need to always perform a matching spinlock_exit() when
309  * releasing a spin lock.  This includes the recursion cases.
310  */
311 #ifdef SMP
312 #define __mtx_unlock_spin(mp) do {					\
313 	if (mtx_recursed((mp)))						\
314 		(mp)->mtx_recurse--;					\
315 	else {								\
316 		LOCKSTAT_PROFILE_RELEASE_LOCK(spin__release, mp);	\
317 		_mtx_release_lock_quick((mp));				\
318 	}								\
319 	spinlock_exit();						\
320 } while (0)
321 #else /* SMP */
322 #define __mtx_unlock_spin(mp) do {					\
323 	if (mtx_recursed((mp)))						\
324 		(mp)->mtx_recurse--;					\
325 	else {								\
326 		LOCKSTAT_PROFILE_RELEASE_LOCK(spin__release, mp);	\
327 		(mp)->mtx_lock = MTX_UNOWNED;				\
328 	}								\
329 	spinlock_exit();						\
330 } while (0)
331 #endif /* SMP */
332 
333 /*
334  * Exported lock manipulation interface.
335  *
336  * mtx_lock(m) locks MTX_DEF mutex `m'
337  *
338  * mtx_lock_spin(m) locks MTX_SPIN mutex `m'
339  *
340  * mtx_unlock(m) unlocks MTX_DEF mutex `m'
341  *
342  * mtx_unlock_spin(m) unlocks MTX_SPIN mutex `m'
343  *
344  * mtx_lock_spin_flags(m, opts) and mtx_lock_flags(m, opts) locks mutex `m'
345  *     and passes option flags `opts' to the "hard" function, if required.
346  *     With these routines, it is possible to pass flags such as MTX_QUIET
347  *     to the appropriate lock manipulation routines.
348  *
349  * mtx_trylock(m) attempts to acquire MTX_DEF mutex `m' but doesn't sleep if
350  *     it cannot. Rather, it returns 0 on failure and non-zero on success.
351  *     It does NOT handle recursion as we assume that if a caller is properly
352  *     using this part of the interface, he will know that the lock in question
353  *     is _not_ recursed.
354  *
355  * mtx_trylock_flags(m, opts) is used the same way as mtx_trylock() but accepts
356  *     relevant option flags `opts.'
357  *
358  * mtx_trylock_spin(m) attempts to acquire MTX_SPIN mutex `m' but doesn't
359  *     spin if it cannot.  Rather, it returns 0 on failure and non-zero on
360  *     success.  It always returns failure for recursed lock attempts.
361  *
362  * mtx_initialized(m) returns non-zero if the lock `m' has been initialized.
363  *
364  * mtx_owned(m) returns non-zero if the current thread owns the lock `m'
365  *
366  * mtx_recursed(m) returns non-zero if the lock `m' is presently recursed.
367  */
368 #define mtx_lock(m)		mtx_lock_flags((m), 0)
369 #define mtx_lock_spin(m)	mtx_lock_spin_flags((m), 0)
370 #define mtx_trylock(m)		mtx_trylock_flags((m), 0)
371 #define mtx_trylock_spin(m)	mtx_trylock_spin_flags((m), 0)
372 #define mtx_unlock(m)		mtx_unlock_flags((m), 0)
373 #define mtx_unlock_spin(m)	mtx_unlock_spin_flags((m), 0)
374 
375 struct mtx_pool;
376 
377 struct mtx_pool *mtx_pool_create(const char *mtx_name, int pool_size, int opts);
378 void mtx_pool_destroy(struct mtx_pool **poolp);
379 struct mtx *mtx_pool_find(struct mtx_pool *pool, void *ptr);
380 struct mtx *mtx_pool_alloc(struct mtx_pool *pool);
381 #define mtx_pool_lock(pool, ptr)					\
382 	mtx_lock(mtx_pool_find((pool), (ptr)))
383 #define mtx_pool_lock_spin(pool, ptr)					\
384 	mtx_lock_spin(mtx_pool_find((pool), (ptr)))
385 #define mtx_pool_unlock(pool, ptr)					\
386 	mtx_unlock(mtx_pool_find((pool), (ptr)))
387 #define mtx_pool_unlock_spin(pool, ptr)					\
388 	mtx_unlock_spin(mtx_pool_find((pool), (ptr)))
389 
390 /*
391  * mtxpool_sleep is a general purpose pool of sleep mutexes.
392  */
393 extern struct mtx_pool *mtxpool_sleep;
394 
395 #ifndef LOCK_DEBUG
396 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/mutex.h>
397 #endif
398 #if LOCK_DEBUG > 0 || defined(MUTEX_NOINLINE)
399 #define	mtx_lock_flags_(m, opts, file, line)				\
400 	_mtx_lock_flags((m), (opts), (file), (line))
401 #define	mtx_unlock_flags_(m, opts, file, line)				\
402 	_mtx_unlock_flags((m), (opts), (file), (line))
403 #define	mtx_lock_spin_flags_(m, opts, file, line)			\
404 	_mtx_lock_spin_flags((m), (opts), (file), (line))
405 #define	mtx_trylock_spin_flags_(m, opts, file, line)			\
406 	_mtx_trylock_spin_flags((m), (opts), (file), (line))
407 #define	mtx_unlock_spin_flags_(m, opts, file, line)			\
408 	_mtx_unlock_spin_flags((m), (opts), (file), (line))
409 #else	/* LOCK_DEBUG == 0 && !MUTEX_NOINLINE */
410 #define	mtx_lock_flags_(m, opts, file, line)				\
411 	__mtx_lock((m), curthread, (opts), (file), (line))
412 #define	mtx_unlock_flags_(m, opts, file, line)				\
413 	__mtx_unlock((m), curthread, (opts), (file), (line))
414 #define	mtx_lock_spin_flags_(m, opts, file, line)			\
415 	__mtx_lock_spin((m), curthread, (opts), (file), (line))
416 #define	mtx_trylock_spin_flags_(m, opts, file, line)			\
417 	__mtx_trylock_spin((m), curthread, (opts), (file), (line))
418 #define	mtx_unlock_spin_flags_(m, opts, file, line)			\
419 	__mtx_unlock_spin((m))
420 #endif	/* LOCK_DEBUG > 0 || MUTEX_NOINLINE */
421 
422 #ifdef INVARIANTS
423 #define	mtx_assert_(m, what, file, line)				\
424 	_mtx_assert((m), (what), (file), (line))
425 
426 #define GIANT_REQUIRED	mtx_assert_(&Giant, MA_OWNED, __FILE__, __LINE__)
427 
428 #else	/* INVARIANTS */
429 #define mtx_assert_(m, what, file, line)	(void)0
430 #define GIANT_REQUIRED
431 #endif	/* INVARIANTS */
432 
433 #define	mtx_lock_flags(m, opts)						\
434 	mtx_lock_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
435 #define	mtx_unlock_flags(m, opts)					\
436 	mtx_unlock_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
437 #define	mtx_lock_spin_flags(m, opts)					\
438 	mtx_lock_spin_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
439 #define	mtx_unlock_spin_flags(m, opts)					\
440 	mtx_unlock_spin_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
441 #define mtx_trylock_flags(m, opts)					\
442 	mtx_trylock_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
443 #define mtx_trylock_spin_flags(m, opts)					\
444 	mtx_trylock_spin_flags_((m), (opts), LOCK_FILE, LOCK_LINE)
445 #define	mtx_assert(m, what)						\
446 	mtx_assert_((m), (what), __FILE__, __LINE__)
447 
448 #define	mtx_sleep(chan, mtx, pri, wmesg, timo)				\
449 	_sleep((chan), &(mtx)->lock_object, (pri), (wmesg),		\
450 	    tick_sbt * (timo), 0, C_HARDCLOCK)
451 
452 #define	MTX_READ_VALUE(m)	((m)->mtx_lock)
453 
454 #define	mtx_initialized(m)	lock_initialized(&(m)->lock_object)
455 
456 #define lv_mtx_owner(v)	((struct thread *)((v) & ~MTX_FLAGMASK))
457 
458 #define mtx_owner(m)	lv_mtx_owner(MTX_READ_VALUE(m))
459 
460 #define mtx_owned(m)	(mtx_owner(m) == curthread)
461 
462 #define mtx_recursed(m)	((m)->mtx_recurse != 0)
463 
464 #define mtx_name(m)	((m)->lock_object.lo_name)
465 
466 /*
467  * Global locks.
468  */
469 extern struct mtx Giant;
470 extern struct mtx blocked_lock;
471 
472 /*
473  * Giant lock manipulation and clean exit macros.
474  * Used to replace return with an exit Giant and return.
475  *
476  * Note that DROP_GIANT*() needs to be paired with PICKUP_GIANT()
477  * The #ifndef is to allow lint-like tools to redefine DROP_GIANT.
478  */
479 #ifndef DROP_GIANT
480 #define DROP_GIANT()							\
481 do {									\
482 	int _giantcnt = 0;						\
483 	WITNESS_SAVE_DECL(Giant);					\
484 									\
485 	if (mtx_owned(&Giant)) {					\
486 		WITNESS_SAVE(&Giant.lock_object, Giant);		\
487 		for (_giantcnt = 0; mtx_owned(&Giant) &&		\
488 		    !SCHEDULER_STOPPED(); _giantcnt++)			\
489 			mtx_unlock(&Giant);				\
490 	}
491 
492 #define PICKUP_GIANT()							\
493 	PARTIAL_PICKUP_GIANT();						\
494 } while (0)
495 
496 #define PARTIAL_PICKUP_GIANT()						\
497 	mtx_assert(&Giant, MA_NOTOWNED);				\
498 	if (_giantcnt > 0) {						\
499 		while (_giantcnt--)					\
500 			mtx_lock(&Giant);				\
501 		WITNESS_RESTORE(&Giant.lock_object, Giant);		\
502 	}
503 #endif
504 
505 struct mtx_args {
506 	void		*ma_mtx;
507 	const char 	*ma_desc;
508 	int		 ma_opts;
509 };
510 
511 #define	MTX_SYSINIT(name, mtx, desc, opts)				\
512 	static struct mtx_args name##_args = {				\
513 		(mtx),							\
514 		(desc),							\
515 		(opts)							\
516 	};								\
517 	SYSINIT(name##_mtx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,	\
518 	    mtx_sysinit, &name##_args);					\
519 	SYSUNINIT(name##_mtx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,	\
520 	    _mtx_destroy, __DEVOLATILE(void *, &(mtx)->mtx_lock))
521 
522 /*
523  * The INVARIANTS-enabled mtx_assert() functionality.
524  *
525  * The constants need to be defined for INVARIANT_SUPPORT infrastructure
526  * support as _mtx_assert() itself uses them and the latter implies that
527  * _mtx_assert() must build.
528  */
529 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
530 #define MA_OWNED	LA_XLOCKED
531 #define MA_NOTOWNED	LA_UNLOCKED
532 #define MA_RECURSED	LA_RECURSED
533 #define MA_NOTRECURSED	LA_NOTRECURSED
534 #endif
535 
536 /*
537  * Common lock type names.
538  */
539 #define	MTX_NETWORK_LOCK	"network driver"
540 
541 #endif	/* _KERNEL */
542 #endif	/* _SYS_MUTEX_H_ */
543