Home | History | Annotate | Line # | Download | only in kern
subr_pserialize.c revision 1.18 
      1 /*	$NetBSD: subr_pserialize.c,v 1.18 2021/10/10 11:20:46 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2010, 2011 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 /*
     30  * Passive serialization.
     31  */
     32 
     33 #include <sys/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: subr_pserialize.c,v 1.18 2021/10/10 11:20:46 riastradh Exp $");
     35 
     36 #include <sys/param.h>
     37 #include <sys/atomic.h>
     38 #include <sys/cpu.h>
     39 #include <sys/evcnt.h>
     40 #include <sys/kmem.h>
     41 #include <sys/mutex.h>
     42 #include <sys/pserialize.h>
     43 #include <sys/xcall.h>
     44 
     45 struct pserialize {
     46 	char			psz_dummy;
     47 };
     48 
     49 static kmutex_t			psz_lock	__cacheline_aligned;
     50 static struct evcnt		psz_ev_excl	__cacheline_aligned =
     51     EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "pserialize", "exclusive access");
     52 EVCNT_ATTACH_STATIC(psz_ev_excl);
     53 
     54 /*
     55  * pserialize_init:
     56  *
     57  *	Initialize passive serialization structures.
     58  */
     59 void
     60 pserialize_init(void)
     61 {
     62 
     63 	mutex_init(&psz_lock, MUTEX_DEFAULT, IPL_NONE);
     64 }
     65 
     66 /*
     67  * pserialize_create:
     68  *
     69  *	Create and initialize a passive serialization object.
     70  */
     71 pserialize_t
     72 pserialize_create(void)
     73 {
     74 	pserialize_t psz;
     75 
     76 	psz = kmem_zalloc(sizeof(*psz), KM_SLEEP);
     77 	return psz;
     78 }
     79 
     80 /*
     81  * pserialize_destroy:
     82  *
     83  *	Destroy a passive serialization object.
     84  */
     85 void
     86 pserialize_destroy(pserialize_t psz)
     87 {
     88 
     89 	kmem_free(psz, sizeof(*psz));
     90 }
     91 
     92 /*
     93  * pserialize_perform:
     94  *
     95  *	Perform the write side of passive serialization.
     96  */
     97 void
     98 pserialize_perform(pserialize_t psz)
     99 {
    100 
    101 	KASSERT(!cpu_intr_p());
    102 	KASSERT(!cpu_softintr_p());
    103 
    104 	if (__predict_false(panicstr != NULL)) {
    105 		return;
    106 	}
    107 
    108 	if (__predict_false(mp_online == false)) {
    109 		psz_ev_excl.ev_count++;
    110 		return;
    111 	}
    112 
    113 	/*
    114 	 * Broadcast a NOP to all CPUs and wait until all of them complete.
    115 	 */
    116 	xc_barrier(XC_HIGHPRI);
    117 
    118 	mutex_enter(&psz_lock);
    119 	psz_ev_excl.ev_count++;
    120 	mutex_exit(&psz_lock);
    121 }
    122 
    123 int
    124 pserialize_read_enter(void)
    125 {
    126 	int s;
    127 
    128 	s = splsoftserial();
    129 	curcpu()->ci_psz_read_depth++;
    130 	__insn_barrier();
    131 	return s;
    132 }
    133 
    134 void
    135 pserialize_read_exit(int s)
    136 {
    137 
    138 	KASSERT(kpreempt_disabled());
    139 
    140 	__insn_barrier();
    141 	if (__predict_false(curcpu()->ci_psz_read_depth-- == 0))
    142 		panic("mismatching pserialize_read_exit()");
    143 	splx(s);
    144 }
    145 
    146 /*
    147  * pserialize_in_read_section:
    148  *
    149  *	True if the caller is in a pserialize read section.  To be used
    150  *	only for diagnostic assertions where we want to guarantee the
    151  *	condition like:
    152  *
    153  *		KASSERT(pserialize_in_read_section());
    154  */
    155 bool
    156 pserialize_in_read_section(void)
    157 {
    158 
    159 	return kpreempt_disabled() && curcpu()->ci_psz_read_depth > 0;
    160 }
    161 
    162 /*
    163  * pserialize_not_in_read_section:
    164  *
    165  *	True if the caller is not in a pserialize read section.  To be
    166  *	used only for diagnostic assertions where we want to guarantee
    167  *	the condition like:
    168  *
    169  *		KASSERT(pserialize_not_in_read_section());
    170  */
    171 bool
    172 pserialize_not_in_read_section(void)
    173 {
    174 	bool notin;
    175 
    176 	kpreempt_disable();
    177 	notin = (curcpu()->ci_psz_read_depth == 0);
    178 	kpreempt_enable();
    179 
    180 	return notin;
    181 }
    182