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spinlock.h revision 1.7.18.1 
      1 /*	$NetBSD: spinlock.h,v 1.7.18.1 2019/06/10 22:08:32 christos 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 #include <linux/irqflags.h>
     40 #include <linux/preempt.h>
     41 
     42 #define	__acquires(lock)	/* XXX lockdep stuff */
     43 #define	__releases(lock)	/* XXX lockdep stuff */
     44 
     45 typedef struct spinlock {
     46 	kmutex_t sl_lock;
     47 } spinlock_t;
     48 
     49 static inline int
     50 spin_is_locked(spinlock_t *spinlock)
     51 {
     52 	return mutex_owned(&spinlock->sl_lock);
     53 }
     54 
     55 static inline void
     56 spin_lock(spinlock_t *spinlock)
     57 {
     58 	mutex_enter(&spinlock->sl_lock);
     59 }
     60 
     61 static inline void
     62 spin_unlock(spinlock_t *spinlock)
     63 {
     64 	mutex_exit(&spinlock->sl_lock);
     65 }
     66 
     67 static inline void
     68 spin_lock_irq(spinlock_t *spinlock)
     69 {
     70 	spin_lock(spinlock);
     71 }
     72 
     73 static inline void
     74 spin_unlock_irq(spinlock_t *spinlock)
     75 {
     76 	spin_unlock(spinlock);
     77 }
     78 
     79 /* Must be a macro because the second argument is to be assigned.  */
     80 #define	spin_lock_irqsave(SPINLOCK, FLAGS)				\
     81 	do {								\
     82 		(FLAGS) = 0;						\
     83 		mutex_enter(&((spinlock_t *)(SPINLOCK))->sl_lock);	\
     84 	} while (0)
     85 
     86 static inline void
     87 spin_unlock_irqrestore(spinlock_t *spinlock, unsigned long __unused flags)
     88 {
     89 	mutex_exit(&spinlock->sl_lock);
     90 }
     91 
     92 static inline void
     93 spin_lock_init(spinlock_t *spinlock)
     94 {
     95 	/* XXX What's the right IPL?  IPL_DRM...?  */
     96 	mutex_init(&spinlock->sl_lock, MUTEX_DEFAULT, IPL_VM);
     97 }
     98 
     99 /*
    100  * XXX Linux doesn't ever destroy spin locks, it seems.  We'll have to
    101  * kludge it up.
    102  */
    103 
    104 static inline void
    105 spin_lock_destroy(spinlock_t *spinlock)
    106 {
    107 	mutex_destroy(&spinlock->sl_lock);
    108 }
    109 
    110 /* This is a macro to make the panic message clearer.  */
    111 #define	assert_spin_locked(spinlock)	\
    112 	KASSERT(mutex_owned(&(spinlock)->sl_lock))
    113 
    114 /*
    115  * Stupid reader/writer spin locks.  No attempt to avoid writer
    116  * starvation.  Must allow recursive readers.  We use mutex and state
    117  * instead of compare-and-swap for expedience and LOCKDEBUG support.
    118  */
    119 
    120 typedef struct linux_rwlock {
    121 	kmutex_t	rw_lock;
    122 	unsigned	rw_nreaders;
    123 } rwlock_t;
    124 
    125 static inline void
    126 rwlock_init(rwlock_t *rw)
    127 {
    128 
    129 	mutex_init(&rw->rw_lock, MUTEX_DEFAULT, IPL_VM);
    130 	rw->rw_nreaders = 0;
    131 }
    132 
    133 static inline void
    134 rwlock_destroy(rwlock_t *rw)
    135 {
    136 
    137 	KASSERTMSG(rw->rw_nreaders == 0,
    138 	    "rwlock still held by %u readers", rw->rw_nreaders);
    139 	mutex_destroy(&rw->rw_lock);
    140 }
    141 
    142 static inline void
    143 write_lock_irq(rwlock_t *rw)
    144 {
    145 
    146 	for (;;) {
    147 		mutex_spin_enter(&rw->rw_lock);
    148 		if (rw->rw_nreaders == 0)
    149 			break;
    150 		mutex_spin_exit(&rw->rw_lock);
    151 	}
    152 }
    153 
    154 static inline void
    155 write_unlock_irq(rwlock_t *rw)
    156 {
    157 
    158 	KASSERT(rw->rw_nreaders == 0);
    159 	mutex_spin_exit(&rw->rw_lock);
    160 }
    161 
    162 static inline void
    163 read_lock(rwlock_t *rw)
    164 {
    165 
    166 	mutex_spin_enter(&rw->rw_lock);
    167 	KASSERT(rw->rw_nreaders < UINT_MAX);
    168 	rw->rw_nreaders++;
    169 	mutex_spin_exit(&rw->rw_lock);
    170 }
    171 
    172 static inline void
    173 read_unlock(rwlock_t *rw)
    174 {
    175 
    176 	mutex_spin_enter(&rw->rw_lock);
    177 	KASSERT(0 < rw->rw_nreaders);
    178 	rw->rw_nreaders--;
    179 	mutex_spin_exit(&rw->rw_lock);
    180 }
    181 
    182 #endif  /* _LINUX_SPINLOCK_H_ */
    183