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
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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
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24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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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 #ifndef _MACHINE_ATOMIC_H_
48 #include <machine/atomic.h>
52 * Initialize a new mutex, placing it in an unlocked state with no refs.
59 mtx->mtx_owner = NULL;
64 mtx_link_init(mtx_link_t link)
66 link->state = MTX_LINK_IDLE;
70 * Deinitialize a mutex
79 * Exclusive-lock a mutex, block until acquired or aborted. Recursion
82 * This version of the function allows the mtx_link to be passed in, thus
83 * giving the caller visibility for the link structure which is required
84 * when calling mtx_abort_ex_link().
86 * The mutex may be aborted at any time while the passed link structure
90 mtx_lock_ex_link(mtx_t mtx, struct mtx_link *link,
91 const char *ident, int flags, int to)
93 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
94 return(_mtx_lock_ex_link(mtx, link, ident, flags, to));
95 mtx->mtx_owner = curthread;
100 * Short-form exclusive-lock a mutex, block until acquired. Recursion is
101 * allowed. This is equivalent to mtx_lock_ex(mtx, "mtxex", 0, 0).
106 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) {
107 _mtx_lock_ex(mtx, "mtxex", 0, 0);
110 mtx->mtx_owner = curthread;
114 * Exclusive-lock a mutex, block until acquired. Recursion is allowed.
116 * Returns 0 on success, or the tsleep() return code on failure.
117 * An error can only be returned if PCATCH is specified in the flags.
120 mtx_lock_ex(mtx_t mtx, const char *ident, int flags, int to)
122 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
123 return(_mtx_lock_ex(mtx, ident, flags, to));
124 mtx->mtx_owner = curthread;
129 mtx_lock_ex_quick(mtx_t mtx, const char *ident)
131 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
132 return(_mtx_lock_ex_quick(mtx, ident));
133 mtx->mtx_owner = curthread;
138 * Share-lock a mutex, block until acquired. Recursion is allowed.
140 * Returns 0 on success, or the tsleep() return code on failure.
141 * An error can only be returned if PCATCH is specified in the flags.
144 mtx_lock_sh(mtx_t mtx, const char *ident, int flags, int to)
146 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0)
147 return(_mtx_lock_sh(mtx, ident, flags, to));
152 mtx_lock_sh_quick(mtx_t mtx, const char *ident)
154 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0)
155 return(_mtx_lock_sh_quick(mtx, ident));
160 * Short-form exclusive spinlock a mutex. Must be paired with
164 mtx_spinlock(mtx_t mtx)
166 globaldata_t gd = mycpu;
169 * Predispose a hard critical section
171 ++gd->gd_curthread->td_critcount;
173 ++gd->gd_spinlocks_wr;
176 * If we cannot get it trivially get it the hard way.
178 * Note that mtx_owner will be set twice if we fail to get it
179 * trivially, but there's no point conditionalizing it as a
180 * conditional will be slower.
182 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
184 mtx->mtx_owner = gd->gd_curthread;
188 mtx_spinlock_try(mtx_t mtx)
190 globaldata_t gd = mycpu;
193 * Predispose a hard critical section
195 ++gd->gd_curthread->td_critcount;
197 ++gd->gd_spinlocks_wr;
200 * If we cannot get it trivially call _mtx_spinlock_try(). This
201 * function will clean up the hard critical section if it fails.
203 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
204 return(_mtx_spinlock_try(mtx));
205 mtx->mtx_owner = gd->gd_curthread;
210 * Short-form exclusive-lock a mutex, spin until acquired. Recursion is
211 * allowed. This form is identical to mtx_spinlock_ex().
213 * Attempt to exclusive-lock a mutex, return 0 on success and
217 mtx_lock_ex_try(mtx_t mtx)
219 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0)
220 return (_mtx_lock_ex_try(mtx));
221 mtx->mtx_owner = curthread;
226 * Attempt to share-lock a mutex, return 0 on success and
230 mtx_lock_sh_try(mtx_t mtx)
232 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0)
233 return (_mtx_lock_sh_try(mtx));
238 * If the lock is held exclusively it must be owned by the caller. If the
239 * lock is already a shared lock this operation is a NOP. A panic will
240 * occur if the lock is not held either shared or exclusive.
242 * The exclusive count is converted to a shared count.
245 mtx_downgrade(mtx_t mtx)
247 mtx->mtx_owner = NULL;
248 if (atomic_cmpset_int(&mtx->mtx_lock, MTX_EXCLUSIVE | 1, 0) == 0)
253 * Upgrade a shared lock to an exclusive lock. The upgrade will fail if
254 * the shared lock has a count other then 1. Optimize the most likely case
255 * but note that a single cmpset can fail due to WANTED races.
257 * If the lock is held exclusively it must be owned by the caller and
258 * this function will simply return without doing anything. A panic will
259 * occur if the lock is held exclusively by someone other then the caller.
261 * Returns 0 on success, EDEADLK on failure.
264 mtx_upgrade_try(mtx_t mtx)
266 if (atomic_cmpset_int(&mtx->mtx_lock, 1, MTX_EXCLUSIVE | 1))
268 return (_mtx_upgrade_try(mtx));
272 * Optimized unlock cases.
274 * NOTE: mtx_unlock() handles any type of mutex: exclusive, shared, and
275 * both blocking and spin methods.
277 * The mtx_unlock_ex/sh() forms are optimized for exclusive or shared
278 * mutexes and produce less code, but it is ok for code to just use
279 * mtx_unlock() and, in fact, if code uses the short-form mtx_lock()
280 * or mtx_spinlock() to lock it should also use mtx_unlock() to unlock.
283 mtx_unlock(mtx_t mtx)
285 u_int lock = mtx->mtx_lock;
287 if (lock == (MTX_EXCLUSIVE | 1)) {
288 mtx->mtx_owner = NULL;
289 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0)
291 } else if (lock == 1) {
292 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0)
300 mtx_unlock_ex(mtx_t mtx)
302 u_int lock = mtx->mtx_lock;
304 if (lock == (MTX_EXCLUSIVE | 1)) {
305 mtx->mtx_owner = NULL;
306 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0)
314 mtx_unlock_sh(mtx_t mtx)
316 if (atomic_cmpset_int(&mtx->mtx_lock, 1, 0) == 0)
321 * NOTE: spinlocks are exclusive-only
324 mtx_spinunlock(mtx_t mtx)
326 globaldata_t gd = mycpu;
330 --gd->gd_spinlocks_wr;
332 --gd->gd_curthread->td_critcount;
336 * Return TRUE (non-zero) if the mutex is locked shared or exclusive by
337 * anyone, including the owner.
340 mtx_islocked(mtx_t mtx)
342 return(mtx->mtx_lock != 0);
346 * Return TRUE (non-zero) if the mutex is locked exclusively by anyone,
347 * including the owner.
349 * The mutex may in an unlocked or shared lock state.
352 mtx_islocked_ex(mtx_t mtx)
354 return((mtx->mtx_lock & MTX_EXCLUSIVE) != 0);
358 * Return TRUE (non-zero) if the mutex is not locked.
361 mtx_notlocked(mtx_t mtx)
363 return(mtx->mtx_lock == 0);
367 * Return TRUE (non-zero) if the mutex is not locked exclusively.
368 * The mutex may in an unlocked or shared lock state.
371 mtx_notlocked_ex(mtx_t mtx)
373 return((mtx->mtx_lock & MTX_EXCLUSIVE) != 0);
377 * Return TRUE (non-zero) if the mutex is exclusively locked by
383 return((mtx->mtx_lock & MTX_EXCLUSIVE) && mtx->mtx_owner == curthread);
387 * Return TRUE (non-zero) if the mutex is not exclusively locked by
391 mtx_notowned(mtx_t mtx)
393 return((mtx->mtx_lock & MTX_EXCLUSIVE) == 0 ||
394 mtx->mtx_owner != curthread);
398 * Return the shared or exclusive lock count. A return value of 0
399 * indicate that the mutex is not locked.
401 * NOTE: If the mutex is held exclusively by someone other then the
402 * caller the lock count for the other owner is still returned.
405 mtx_lockrefs(mtx_t mtx)
407 return(mtx->mtx_lock & MTX_MASK);
411 * Bump the lock's ref count. This field is independent of the lock.
416 atomic_add_acq_int(&mtx->mtx_refs, 1);
420 * Drop the lock's ref count. This field is independent of the lock.
422 * Returns the previous ref count, interlocked so testing against
423 * 1 means you won the 1->0 transition
428 return (atomic_fetchadd_int(&mtx->mtx_refs, -1));