1 /* 2 * Copyright (c) 2005 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 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 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 /* 35 * This API provides a fast locked-bus-cycle-based serializer. It's 36 * basically a low level NON-RECURSIVE exclusive lock that can be held across 37 * a blocking condition. It is NOT a mutex. 38 * 39 * This serializer is primarily designed for low level situations and 40 * interrupt/device interaction. There are two primary facilities. First, 41 * the serializer facility itself. Second, an integrated interrupt handler 42 * disablement facility. 43 */ 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/kernel.h> 48 #include <sys/proc.h> 49 #include <sys/rtprio.h> 50 #include <sys/queue.h> 51 #include <sys/serialize.h> 52 #include <sys/sysctl.h> 53 #include <sys/ktr.h> 54 #include <sys/kthread.h> 55 #include <machine/cpu.h> 56 #include <machine/cpufunc.h> 57 #include <machine/specialreg.h> 58 #include <machine/clock.h> 59 #include <sys/lock.h> 60 61 #ifndef SLZ_ADAPTIVE_SPINMAX 62 #define SLZ_ADAPTIVE_SPINMAX 4096 63 #endif 64 65 #define SLZ_KTR_STRING "slz=%p" 66 #define SLZ_KTR_ARGS lwkt_serialize_t slz 67 68 #ifndef KTR_SERIALIZER 69 #define KTR_SERIALIZER KTR_ALL 70 #endif 71 72 KTR_INFO_MASTER(slz); 73 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS); 74 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS); 75 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS); 76 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS); 77 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS); 78 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS); 79 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS); 80 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS); 81 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS); 82 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 9, SLZ_KTR_STRING, SLZ_KTR_ARGS); 83 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS); 84 KTR_INFO(KTR_SERIALIZER, slz, adapt_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS); 85 KTR_INFO(KTR_SERIALIZER, slz, adapt_end, 12, SLZ_KTR_STRING, SLZ_KTR_ARGS); 86 KTR_INFO(KTR_SERIALIZER, slz, adapt_spinend, 13, "slz=%p try=%d", 87 lwkt_serialize_t slz, int try); 88 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepb, 14, SLZ_KTR_STRING, SLZ_KTR_ARGS); 89 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepe, 15, SLZ_KTR_STRING, SLZ_KTR_ARGS); 90 91 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz) 92 #define logslz_spinend(slz, try) KTR_LOG(slz_adapt_spinend, slz, try) 93 94 static void lwkt_serialize_sleep(void *info); 95 static void lwkt_serialize_wakeup(void *info); 96 97 void 98 lwkt_serialize_init(lwkt_serialize_t s) 99 { 100 atomic_intr_init(&s->interlock); 101 s->last_td = (void *)-4; 102 } 103 104 void 105 lwkt_serialize_enter(lwkt_serialize_t s) 106 { 107 ASSERT_NOT_SERIALIZED(s); 108 109 logslz(enter_beg, s); 110 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 111 logslz(enter_end, s); 112 s->last_td = curthread; 113 } 114 115 /* 116 * Returns non-zero on success 117 */ 118 int 119 lwkt_serialize_try(lwkt_serialize_t s) 120 { 121 int error; 122 123 ASSERT_NOT_SERIALIZED(s); 124 125 logslz(try, s); 126 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 127 s->last_td = curthread; 128 logslz(tryok, s); 129 return(1); 130 } 131 logslz(tryfail, s); 132 return (0); 133 } 134 135 void 136 lwkt_serialize_exit(lwkt_serialize_t s) 137 { 138 ASSERT_SERIALIZED(s); 139 s->last_td = (void *)-2; 140 logslz(exit_beg, s); 141 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 142 logslz(exit_end, s); 143 } 144 145 /* 146 * Interrupt handler disablement support, used by drivers. Non-stackable 147 * (uses bit 30). 148 */ 149 void 150 lwkt_serialize_handler_disable(lwkt_serialize_t s) 151 { 152 atomic_intr_handler_disable(&s->interlock); 153 } 154 155 void 156 lwkt_serialize_handler_enable(lwkt_serialize_t s) 157 { 158 atomic_intr_handler_enable(&s->interlock); 159 } 160 161 void 162 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 163 void *arg, void *frame) 164 { 165 /* 166 * note: a return value of 0 indicates that the interrupt handler is 167 * enabled. 168 */ 169 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 170 logslz(enter_beg, s); 171 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 172 logslz(enter_end, s); 173 s->last_td = curthread; 174 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 175 func(arg, frame); 176 177 ASSERT_SERIALIZED(s); 178 s->last_td = (void *)-2; 179 logslz(exit_beg, s); 180 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 181 logslz(exit_end, s); 182 } 183 } 184 185 /* 186 * Similar to handler_call but does not block. Returns 0 on success, 187 * and 1 on failure. 188 */ 189 int 190 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 191 void *arg, void *frame) 192 { 193 /* 194 * note: a return value of 0 indicates that the interrupt handler is 195 * enabled. 196 */ 197 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 198 logslz(try, s); 199 if (atomic_intr_cond_try(&s->interlock) == 0) { 200 s->last_td = curthread; 201 logslz(tryok, s); 202 203 func(arg, frame); 204 205 ASSERT_SERIALIZED(s); 206 s->last_td = (void *)-2; 207 logslz(exit_beg, s); 208 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 209 logslz(exit_end, s); 210 return(0); 211 } 212 } 213 logslz(tryfail, s); 214 return(1); 215 } 216 217 218 /* 219 * Helper functions 220 * 221 * It is possible to race an interrupt which acquires and releases the 222 * bit, then calls wakeup before we actually go to sleep, so we 223 * need to check that the interlock is still acquired from within 224 * a critical section prior to sleeping. 225 */ 226 static void 227 lwkt_serialize_sleep(void *info) 228 { 229 lwkt_serialize_t s = info; 230 231 tsleep_interlock(s, 0); 232 if (atomic_intr_cond_test(&s->interlock) != 0) { 233 logslz(sleep_beg, s); 234 tsleep(s, PINTERLOCKED, "slize", 0); 235 logslz(sleep_end, s); 236 } 237 } 238 239 void 240 lwkt_serialize_adaptive_enter(lwkt_serialize_t s) 241 { 242 int try; 243 244 ASSERT_NOT_SERIALIZED(s); 245 logslz(adapt_beg, s); 246 247 if (atomic_intr_cond_try(&s->interlock) == 0) { 248 s->last_td = curthread; 249 logslz(adapt_end, s); 250 return; 251 } 252 253 restart: 254 /* 255 * Spinning a little bit, before going to sleep 256 * 257 * See the comment before kern/kern_spinlock.c 258 * _spin_lock_contested() about why atomic_intr_cond_test() 259 * is called first. atomic_intr_cond_test() contains 260 * _no_ MPLOCKED intruction. 261 */ 262 for (try = SLZ_ADAPTIVE_SPINMAX; try; --try) { 263 if (atomic_intr_cond_test(&s->interlock) == 0 && 264 atomic_intr_cond_try(&s->interlock) == 0) { 265 s->last_td = curthread; 266 logslz_spinend(s, try); 267 return; 268 } 269 } 270 271 atomic_intr_cond_inc(&s->interlock); 272 273 tsleep_interlock(s, 0); 274 if (atomic_intr_cond_try(&s->interlock) == 0) { 275 atomic_intr_cond_dec(&s->interlock); 276 s->last_td = curthread; 277 logslz_spinend(s, 0); 278 return; 279 } else { 280 logslz(adapt_sleepb, s); 281 tsleep(s, PINTERLOCKED, "aslize", 0); 282 logslz(adapt_sleepe, s); 283 284 atomic_intr_cond_dec(&s->interlock); 285 goto restart; 286 } 287 } 288 289 static void 290 lwkt_serialize_wakeup(void *info) 291 { 292 logslz(wakeup_beg, info); 293 wakeup(info); 294 logslz(wakeup_end, info); 295 } 296