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