Home | History | Annotate | Line # | Download | only in linux
spinlock.h revision 1.12 
      1 /*	$NetBSD: spinlock.h,v 1.12 2021/12/19 11:38:37 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2013 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Taylor R. Campbell.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #ifndef _LINUX_SPINLOCK_H_
     33 #define _LINUX_SPINLOCK_H_
     34 
     35 #include <sys/cdefs.h>
     36 #include <sys/mutex.h>
     37 
     38 #include <machine/limits.h>
     39 
     40 #include <linux/irqflags.h>
     41 #include <linux/lockdep.h>
     42 #include <linux/preempt.h>
     43 
     44 typedef struct spinlock {
     45 	kmutex_t sl_lock;
     46 } spinlock_t;
     47 
     48 static inline int
     49 spin_is_locked(spinlock_t *spinlock)
     50 {
     51 	return mutex_owned(&spinlock->sl_lock);
     52 }
     53 
     54 static inline void
     55 spin_lock(spinlock_t *spinlock)
     56 {
     57 	mutex_enter(&spinlock->sl_lock);
     58 }
     59 
     60 static inline void
     61 spin_unlock(spinlock_t *spinlock)
     62 {
     63 	mutex_exit(&spinlock->sl_lock);
     64 }
     65 
     66 static inline void
     67 spin_lock_irq(spinlock_t *spinlock)
     68 {
     69 	spin_lock(spinlock);
     70 }
     71 
     72 static inline void
     73 spin_unlock_irq(spinlock_t *spinlock)
     74 {
     75 	spin_unlock(spinlock);
     76 }
     77 
     78 /* Must be a macro because the second argument is to be assigned.  */
     79 #define	spin_lock_irqsave(SPINLOCK, FLAGS)				\
     80 	do {								\
     81 		(FLAGS) = 0;						\
     82 		mutex_enter(&((spinlock_t *)(SPINLOCK))->sl_lock);	\
     83 	} while (0)
     84 
     85 static inline void
     86 spin_unlock_irqrestore(spinlock_t *spinlock, unsigned long __unused flags)
     87 {
     88 	mutex_exit(&spinlock->sl_lock);
     89 }
     90 
     91 static inline void
     92 spin_lock_nested(spinlock_t *spinlock, int subclass)
     93 {
     94 	spin_lock(spinlock);
     95 }
     96 
     97 #define	spin_lock_irqsave_nested(SPINLOCK, FLAGS, SUBCLASS)		      \
     98 	spin_lock_irqsave(SPINLOCK, FLAGS)
     99 
    100 static inline void
    101 spin_lock_init(spinlock_t *spinlock)
    102 {
    103 	/* XXX What's the right IPL?  IPL_DRM...?  */
    104 	mutex_init(&spinlock->sl_lock, MUTEX_DEFAULT, IPL_VM);
    105 }
    106 
    107 /*
    108  * XXX Linux doesn't ever destroy spin locks, it seems.  We'll have to
    109  * kludge it up.
    110  */
    111 
    112 static inline void
    113 spin_lock_destroy(spinlock_t *spinlock)
    114 {
    115 	mutex_destroy(&spinlock->sl_lock);
    116 }
    117 
    118 /* This is a macro to make the panic message clearer.  */
    119 #define	assert_spin_locked(spinlock)	\
    120 	KASSERT(mutex_owned(&(spinlock)->sl_lock))
    121 
    122 /*
    123  * Stupid reader/writer spin locks.  No attempt to avoid writer
    124  * starvation.  Must allow recursive readers.  We use mutex and state
    125  * instead of compare-and-swap for expedience and LOCKDEBUG support.
    126  */
    127 
    128 typedef struct linux_rwlock {
    129 	kmutex_t	rw_lock;
    130 	unsigned	rw_nreaders;
    131 } rwlock_t;
    132 
    133 static inline void
    134 rwlock_init(rwlock_t *rw)
    135 {
    136 
    137 	mutex_init(&rw->rw_lock, MUTEX_DEFAULT, IPL_VM);
    138 	rw->rw_nreaders = 0;
    139 }
    140 
    141 static inline void
    142 rwlock_destroy(rwlock_t *rw)
    143 {
    144 
    145 	KASSERTMSG(rw->rw_nreaders == 0,
    146 	    "rwlock still held by %u readers", rw->rw_nreaders);
    147 	mutex_destroy(&rw->rw_lock);
    148 }
    149 
    150 static inline void
    151 write_lock_irq(rwlock_t *rw)
    152 {
    153 
    154 	for (;;) {
    155 		mutex_spin_enter(&rw->rw_lock);
    156 		if (rw->rw_nreaders == 0)
    157 			break;
    158 		mutex_spin_exit(&rw->rw_lock);
    159 	}
    160 }
    161 
    162 static inline void
    163 write_unlock_irq(rwlock_t *rw)
    164 {
    165 
    166 	KASSERT(rw->rw_nreaders == 0);
    167 	mutex_spin_exit(&rw->rw_lock);
    168 }
    169 
    170 static inline void
    171 read_lock(rwlock_t *rw)
    172 {
    173 
    174 	mutex_spin_enter(&rw->rw_lock);
    175 	KASSERT(rw->rw_nreaders < UINT_MAX);
    176 	rw->rw_nreaders++;
    177 	mutex_spin_exit(&rw->rw_lock);
    178 }
    179 
    180 static inline void
    181 read_unlock(rwlock_t *rw)
    182 {
    183 
    184 	mutex_spin_enter(&rw->rw_lock);
    185 	KASSERT(0 < rw->rw_nreaders);
    186 	rw->rw_nreaders--;
    187 	mutex_spin_exit(&rw->rw_lock);
    188 }
    189 
    190 static inline void
    191 local_bh_disable(void)
    192 {
    193 }
    194 
    195 static inline void
    196 local_bh_enable(void)
    197 {
    198 }
    199 
    200 #endif  /* _LINUX_SPINLOCK_H_ */
    201