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subr_pserialize.c revision 1.19 
      1 /*	$NetBSD: subr_pserialize.c,v 1.19 2022/11/15 10:29:56 macallan 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 1.19 2022/11/15 10:29:56 macallan Exp $");
     35 
     36 #include <sys/param.h>
     37 #include <sys/atomic.h>
     38 #include <sys/cpu.h>
     39 #include <sys/kernel.h>
     40 #include <sys/evcnt.h>
     41 #include <sys/kmem.h>
     42 #include <sys/mutex.h>
     43 #include <sys/pserialize.h>
     44 #include <sys/xcall.h>
     45 
     46 struct pserialize {
     47 	char			psz_dummy;
     48 };
     49 
     50 static kmutex_t			psz_lock	__cacheline_aligned;
     51 static struct evcnt		psz_ev_excl	__cacheline_aligned =
     52     EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "pserialize", "exclusive access");
     53 EVCNT_ATTACH_STATIC(psz_ev_excl);
     54 
     55 /*
     56  * pserialize_init:
     57  *
     58  *	Initialize passive serialization structures.
     59  */
     60 void
     61 pserialize_init(void)
     62 {
     63 
     64 	mutex_init(&psz_lock, MUTEX_DEFAULT, IPL_NONE);
     65 }
     66 
     67 /*
     68  * pserialize_create:
     69  *
     70  *	Create and initialize a passive serialization object.
     71  */
     72 pserialize_t
     73 pserialize_create(void)
     74 {
     75 	pserialize_t psz;
     76 
     77 	psz = kmem_zalloc(sizeof(*psz), KM_SLEEP);
     78 	return psz;
     79 }
     80 
     81 /*
     82  * pserialize_destroy:
     83  *
     84  *	Destroy a passive serialization object.
     85  */
     86 void
     87 pserialize_destroy(pserialize_t psz)
     88 {
     89 
     90 	kmem_free(psz, sizeof(*psz));
     91 }
     92 
     93 /*
     94  * pserialize_perform:
     95  *
     96  *	Perform the write side of passive serialization.
     97  */
     98 void
     99 pserialize_perform(pserialize_t psz)
    100 {
    101 
    102 	KASSERT(!cpu_intr_p());
    103 	KASSERT(!cpu_softintr_p());
    104 
    105 	if (__predict_false(panicstr != NULL)) {
    106 		return;
    107 	}
    108 
    109 	if (__predict_false(mp_online == false)) {
    110 		psz_ev_excl.ev_count++;
    111 		return;
    112 	}
    113 
    114 	/*
    115 	 * Broadcast a NOP to all CPUs and wait until all of them complete.
    116 	 */
    117 	xc_barrier(XC_HIGHPRI);
    118 
    119 	mutex_enter(&psz_lock);
    120 	psz_ev_excl.ev_count++;
    121 	mutex_exit(&psz_lock);
    122 }
    123 
    124 int
    125 pserialize_read_enter(void)
    126 {
    127 	int s;
    128 
    129 	s = splsoftserial();
    130 	curcpu()->ci_psz_read_depth++;
    131 	__insn_barrier();
    132 	return s;
    133 }
    134 
    135 void
    136 pserialize_read_exit(int s)
    137 {
    138 
    139 	KASSERT((cold || kpreempt_disabled()));
    140 
    141 	__insn_barrier();
    142 	if (__predict_false(curcpu()->ci_psz_read_depth-- == 0))
    143 		panic("mismatching pserialize_read_exit()");
    144 	splx(s);
    145 }
    146 
    147 /*
    148  * pserialize_in_read_section:
    149  *
    150  *	True if the caller is in a pserialize read section.  To be used
    151  *	only for diagnostic assertions where we want to guarantee the
    152  *	condition like:
    153  *
    154  *		KASSERT(pserialize_in_read_section());
    155  */
    156 bool
    157 pserialize_in_read_section(void)
    158 {
    159 
    160 	return kpreempt_disabled() && curcpu()->ci_psz_read_depth > 0;
    161 }
    162 
    163 /*
    164  * pserialize_not_in_read_section:
    165  *
    166  *	True if the caller is not in a pserialize read section.  To be
    167  *	used only for diagnostic assertions where we want to guarantee
    168  *	the condition like:
    169  *
    170  *		KASSERT(pserialize_not_in_read_section());
    171  */
    172 bool
    173 pserialize_not_in_read_section(void)
    174 {
    175 	bool notin;
    176 
    177 	kpreempt_disable();
    178 	notin = (curcpu()->ci_psz_read_depth == 0);
    179 	kpreempt_enable();
    180 
    181 	return notin;
    182 }
    183