1 /* $NetBSD: subr_pserialize.c,v 1.17 2019/12/05 03:21:29 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 1.17 2019/12/05 03:21:29 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 lwp_t * psz_owner; 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 KASSERT(psz->psz_owner == NULL); 90 kmem_free(psz, sizeof(*psz)); 91 } 92 93 /* 94 * pserialize_perform: 95 * 96 * Perform the write side of passive serialization. This operation 97 * MUST be serialized at a caller level (e.g. with a mutex or by a 98 * single-threaded use). 99 */ 100 void 101 pserialize_perform(pserialize_t psz) 102 { 103 104 KASSERT(!cpu_intr_p()); 105 KASSERT(!cpu_softintr_p()); 106 107 if (__predict_false(panicstr != NULL)) { 108 return; 109 } 110 KASSERT(psz->psz_owner == NULL); 111 112 if (__predict_false(mp_online == false)) { 113 psz_ev_excl.ev_count++; 114 return; 115 } 116 117 psz->psz_owner = curlwp; 118 119 /* 120 * Broadcast a NOP to all CPUs and wait until all of them complete. 121 */ 122 xc_barrier(XC_HIGHPRI); 123 124 KASSERT(psz->psz_owner == curlwp); 125 psz->psz_owner = NULL; 126 mutex_enter(&psz_lock); 127 psz_ev_excl.ev_count++; 128 mutex_exit(&psz_lock); 129 } 130 131 int 132 pserialize_read_enter(void) 133 { 134 int s; 135 136 s = splsoftserial(); 137 curcpu()->ci_psz_read_depth++; 138 __insn_barrier(); 139 return s; 140 } 141 142 void 143 pserialize_read_exit(int s) 144 { 145 146 KASSERT(kpreempt_disabled()); 147 148 __insn_barrier(); 149 if (__predict_false(curcpu()->ci_psz_read_depth-- == 0)) 150 panic("mismatching pserialize_read_exit()"); 151 splx(s); 152 } 153 154 /* 155 * pserialize_in_read_section: 156 * 157 * True if the caller is in a pserialize read section. To be used 158 * only for diagnostic assertions where we want to guarantee the 159 * condition like: 160 * 161 * KASSERT(pserialize_in_read_section()); 162 */ 163 bool 164 pserialize_in_read_section(void) 165 { 166 167 return kpreempt_disabled() && curcpu()->ci_psz_read_depth > 0; 168 } 169 170 /* 171 * pserialize_not_in_read_section: 172 * 173 * True if the caller is not in a pserialize read section. To be 174 * used only for diagnostic assertions where we want to guarantee 175 * the condition like: 176 * 177 * KASSERT(pserialize_not_in_read_section()); 178 */ 179 bool 180 pserialize_not_in_read_section(void) 181 { 182 bool notin; 183 184 kpreempt_disable(); 185 notin = (curcpu()->ci_psz_read_depth == 0); 186 kpreempt_enable(); 187 188 return notin; 189 } 190