2 * Copyright (c) 2009 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 #ifndef _SYS_MUTEX2_H_
36 #define _SYS_MUTEX2_H_
39 #include <sys/mutex.h>
41 #ifndef _SYS_THREAD2_H_
42 #include <sys/thread2.h>
44 #ifndef _SYS_GLOBALDATA_H_
45 #include <sys/globaldata.h>
47 #include <machine/atomic.h>
50 * Initialize a new mutex, placing it in an unlocked state with no refs.
57 mtx->mtx_owner = NULL;
62 mtx_link_init(mtx_link_t link)
64 link->state = MTX_LINK_IDLE;
68 * Deinitialize a mutex
77 * Exclusive-lock a mutex, block until acquired or aborted. Recursion
80 * This version of the function allows the mtx_link to be passed in, thus
81 * giving the caller visibility for the link structure which is required
82 * when calling mtx_abort_ex_link().
84 * The mutex may be aborted at any time while the passed link structure
88 mtx_lock_ex_link(mtx_t mtx, struct mtx_link *link,
89 const char *ident, int flags, int to)
91 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
92 return(_mtx_lock_ex_link(mtx, link, ident, flags, to));
93 mtx->mtx_owner = curthread;
98 * Short-form exclusive-lock a mutex, block until acquired. Recursion is
99 * allowed. This is equivalent to mtx_lock_ex(mtx, "mtxex", 0, 0).
104 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) {
105 _mtx_lock_ex(mtx, "mtxex", 0, 0);
108 mtx->mtx_owner = curthread;
112 * Exclusive-lock a mutex, block until acquired. Recursion is allowed.
114 * Returns 0 on success, or the tsleep() return code on failure.
115 * An error can only be returned if PCATCH is specified in the flags.
118 mtx_lock_ex(mtx_t mtx, const char *ident, int flags, int to)
120 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
121 return(_mtx_lock_ex(mtx, ident, flags, to));
122 mtx->mtx_owner = curthread;
127 mtx_lock_ex_quick(mtx_t mtx, const char *ident)
129 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
130 return(_mtx_lock_ex_quick(mtx, ident));
131 mtx->mtx_owner = curthread;
136 * Share-lock a mutex, block until acquired. Recursion is allowed.
138 * Returns 0 on success, or the tsleep() return code on failure.
139 * An error can only be returned if PCATCH is specified in the flags.
142 mtx_lock_sh(mtx_t mtx, const char *ident, int flags, int to)
144 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0)
145 return(_mtx_lock_sh(mtx, ident, flags, to));
150 mtx_lock_sh_quick(mtx_t mtx, const char *ident)
152 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0)
153 return(_mtx_lock_sh_quick(mtx, ident));
158 * Short-form exclusive spinlock a mutex. Must be paired with
162 mtx_spinlock(mtx_t mtx)
164 globaldata_t gd = mycpu;
167 * Predispose a hard critical section
169 ++gd->gd_curthread->td_critcount;
174 * If we cannot get it trivially get it the hard way.
176 * Note that mtx_owner will be set twice if we fail to get it
177 * trivially, but there's no point conditionalizing it as a
178 * conditional will be slower.
180 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
182 mtx->mtx_owner = gd->gd_curthread;
186 mtx_spinlock_try(mtx_t mtx)
188 globaldata_t gd = mycpu;
191 * Predispose a hard critical section
193 ++gd->gd_curthread->td_critcount;
198 * If we cannot get it trivially call _mtx_spinlock_try(). This
199 * function will clean up the hard critical section if it fails.
201 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
202 return(_mtx_spinlock_try(mtx));
203 mtx->mtx_owner = gd->gd_curthread;
208 * Short-form exclusive-lock a mutex, spin until acquired. Recursion is
209 * allowed. This form is identical to mtx_spinlock_ex().
211 * Attempt to exclusive-lock a mutex, return 0 on success and
215 mtx_lock_ex_try(mtx_t mtx)
217 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
218 return (_mtx_lock_ex_try(mtx));
219 mtx->mtx_owner = curthread;
224 * Attempt to share-lock a mutex, return 0 on success and
228 mtx_lock_sh_try(mtx_t mtx)
230 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0)
231 return (_mtx_lock_sh_try(mtx));
236 * If the lock is held exclusively it must be owned by the caller. If the
237 * lock is already a shared lock this operation is a NOP. A panic will
238 * occur if the lock is not held either shared or exclusive.
240 * The exclusive count is converted to a shared count.
243 mtx_downgrade(mtx_t mtx)
245 mtx->mtx_owner = NULL;
246 if (atomic_cmpset_int(&mtx->mtx_lock, MTX_EXCLUSIVE | 1, 0) == 0)
251 * Upgrade a shared lock to an exclusive lock. The upgrade will fail if
252 * the shared lock has a count other then 1. Optimize the most likely case
253 * but note that a single cmpset can fail due to WANTED races.
255 * If the lock is held exclusively it must be owned by the caller and
256 * this function will simply return without doing anything. A panic will
257 * occur if the lock is held exclusively by someone other then the caller.
259 * Returns 0 on success, EDEADLK on failure.
262 mtx_upgrade_try(mtx_t mtx)
264 if (atomic_cmpset_int(&mtx->mtx_lock, 1, MTX_EXCLUSIVE | 1))
266 return (_mtx_upgrade_try(mtx));
270 * Optimized unlock cases.
272 * NOTE: mtx_unlock() handles any type of mutex: exclusive, shared, and
273 * both blocking and spin methods.
275 * The mtx_unlock_ex/sh() forms are optimized for exclusive or shared
276 * mutexes and produce less code, but it is ok for code to just use
277 * mtx_unlock() and, in fact, if code uses the short-form mtx_lock()
278 * or mtx_spinlock() to lock it should also use mtx_unlock() to unlock.
281 mtx_unlock(mtx_t mtx)
283 u_int lock = mtx->mtx_lock;
285 if (lock == (MTX_EXCLUSIVE | 1)) {
286 mtx->mtx_owner = NULL;
287 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0)
289 } else if (lock == 1) {
290 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0)
298 mtx_unlock_ex(mtx_t mtx)
300 u_int lock = mtx->mtx_lock;
302 if (lock == (MTX_EXCLUSIVE | 1)) {
303 mtx->mtx_owner = NULL;
304 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0)
312 mtx_unlock_sh(mtx_t mtx)
314 if (atomic_cmpset_int(&mtx->mtx_lock, 1, 0) == 0)
319 * NOTE: spinlocks are exclusive-only
322 mtx_spinunlock(mtx_t mtx)
324 globaldata_t gd = mycpu;
330 --gd->gd_curthread->td_critcount;
334 * Return TRUE (non-zero) if the mutex is locked shared or exclusive by
335 * anyone, including the owner.
338 mtx_islocked(mtx_t mtx)
340 return(mtx->mtx_lock != 0);
344 * Return TRUE (non-zero) if the mutex is locked exclusively by anyone,
345 * including the owner.
347 * The mutex may in an unlocked or shared lock state.
350 mtx_islocked_ex(mtx_t mtx)
352 return((mtx->mtx_lock & MTX_EXCLUSIVE) != 0);
356 * Return TRUE (non-zero) if the mutex is not locked.
359 mtx_notlocked(mtx_t mtx)
361 return(mtx->mtx_lock == 0);
365 * Return TRUE (non-zero) if the mutex is not locked exclusively.
366 * The mutex may in an unlocked or shared lock state.
369 mtx_notlocked_ex(mtx_t mtx)
371 return((mtx->mtx_lock & MTX_EXCLUSIVE) != 0);
375 * Return TRUE (non-zero) if the mutex is exclusively locked by
381 return((mtx->mtx_lock & MTX_EXCLUSIVE) && mtx->mtx_owner == curthread);
385 * Return TRUE (non-zero) if the mutex is not exclusively locked by
389 mtx_notowned(mtx_t mtx)
391 return((mtx->mtx_lock & MTX_EXCLUSIVE) == 0 ||
392 mtx->mtx_owner != curthread);
396 * Return the shared or exclusive lock count. A return value of 0
397 * indicate that the mutex is not locked.
399 * NOTE: If the mutex is held exclusively by someone other then the
400 * caller the lock count for the other owner is still returned.
403 mtx_lockrefs(mtx_t mtx)
405 return(mtx->mtx_lock & MTX_MASK);
409 * Bump the lock's ref count. This field is independent of the lock.
414 atomic_add_acq_int(&mtx->mtx_refs, 1);
418 * Drop the lock's ref count. This field is independent of the lock.
420 * Returns the previous ref count, interlocked so testing against
421 * 1 means you won the 1->0 transition
426 return (atomic_fetchadd_int(&mtx->mtx_refs, -1));