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/thread2.h> 52 #include <sys/serialize.h> 53 #include <sys/sysctl.h> 54 #include <sys/ktr.h> 55 #include <sys/kthread.h> 56 #include <machine/cpu.h> 57 #include <machine/cpufunc.h> 58 #include <machine/specialreg.h> 59 #include <machine/clock.h> 60 #include <sys/lock.h> 61 62 #ifndef SLZ_ADAPTIVE_SPINMAX 63 #define SLZ_ADAPTIVE_SPINMAX 4096 64 #endif 65 66 #define SLZ_KTR_STRING "slz=%p" 67 #define SLZ_KTR_ARGS lwkt_serialize_t slz 68 69 #ifndef KTR_SERIALIZER 70 #define KTR_SERIALIZER KTR_ALL 71 #endif 72 73 KTR_INFO_MASTER(slz); 74 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS); 75 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS); 76 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS); 77 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS); 78 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS); 79 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS); 80 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS); 81 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS); 82 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS); 83 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 9, SLZ_KTR_STRING, SLZ_KTR_ARGS); 84 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS); 85 KTR_INFO(KTR_SERIALIZER, slz, adapt_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS); 86 KTR_INFO(KTR_SERIALIZER, slz, adapt_end, 12, SLZ_KTR_STRING, SLZ_KTR_ARGS); 87 KTR_INFO(KTR_SERIALIZER, slz, adapt_spinend, 13, "slz=%p try=%d", 88 lwkt_serialize_t slz, int try); 89 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepb, 14, SLZ_KTR_STRING, SLZ_KTR_ARGS); 90 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepe, 15, SLZ_KTR_STRING, SLZ_KTR_ARGS); 91 92 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz) 93 #define logslz_spinend(slz, try) KTR_LOG(slz_adapt_spinend, slz, try) 94 95 static void lwkt_serialize_sleep(void *info); 96 static void lwkt_serialize_wakeup(void *info); 97 98 void 99 lwkt_serialize_init(lwkt_serialize_t s) 100 { 101 atomic_intr_init(&s->interlock); 102 s->last_td = (void *)-4; 103 } 104 105 void 106 lwkt_serialize_enter(lwkt_serialize_t s) 107 { 108 ASSERT_NOT_SERIALIZED(s); 109 110 logslz(enter_beg, s); 111 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 112 logslz(enter_end, s); 113 s->last_td = curthread; 114 } 115 116 /* 117 * Returns non-zero on success 118 */ 119 int 120 lwkt_serialize_try(lwkt_serialize_t s) 121 { 122 int error; 123 124 ASSERT_NOT_SERIALIZED(s); 125 126 logslz(try, s); 127 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 128 s->last_td = curthread; 129 logslz(tryok, s); 130 return(1); 131 } 132 logslz(tryfail, s); 133 return (0); 134 } 135 136 void 137 lwkt_serialize_exit(lwkt_serialize_t s) 138 { 139 ASSERT_SERIALIZED(s); 140 s->last_td = (void *)-2; 141 logslz(exit_beg, s); 142 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 143 logslz(exit_end, s); 144 } 145 146 /* 147 * Interrupt handler disablement support, used by drivers. Non-stackable 148 * (uses bit 30). 149 */ 150 void 151 lwkt_serialize_handler_disable(lwkt_serialize_t s) 152 { 153 atomic_intr_handler_disable(&s->interlock); 154 } 155 156 void 157 lwkt_serialize_handler_enable(lwkt_serialize_t s) 158 { 159 atomic_intr_handler_enable(&s->interlock); 160 } 161 162 void 163 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 164 void *arg, void *frame) 165 { 166 /* 167 * note: a return value of 0 indicates that the interrupt handler is 168 * enabled. 169 */ 170 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 171 logslz(enter_beg, s); 172 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 173 logslz(enter_end, s); 174 s->last_td = curthread; 175 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 176 func(arg, frame); 177 178 ASSERT_SERIALIZED(s); 179 s->last_td = (void *)-2; 180 logslz(exit_beg, s); 181 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 182 logslz(exit_end, s); 183 } 184 } 185 186 /* 187 * Similar to handler_call but does not block. Returns 0 on success, 188 * and 1 on failure. 189 */ 190 int 191 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 192 void *arg, void *frame) 193 { 194 /* 195 * note: a return value of 0 indicates that the interrupt handler is 196 * enabled. 197 */ 198 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 199 logslz(try, s); 200 if (atomic_intr_cond_try(&s->interlock) == 0) { 201 s->last_td = curthread; 202 logslz(tryok, s); 203 204 func(arg, frame); 205 206 ASSERT_SERIALIZED(s); 207 s->last_td = (void *)-2; 208 logslz(exit_beg, s); 209 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 210 logslz(exit_end, s); 211 return(0); 212 } 213 } 214 logslz(tryfail, s); 215 return(1); 216 } 217 218 219 /* 220 * Helper functions 221 * 222 * It is possible to race an interrupt which acquires and releases the 223 * bit, then calls wakeup before we actually go to sleep, so we 224 * need to check that the interlock is still acquired from within 225 * a critical section prior to sleeping. 226 */ 227 static void 228 lwkt_serialize_sleep(void *info) 229 { 230 lwkt_serialize_t s = info; 231 232 tsleep_interlock(s, 0); 233 if (atomic_intr_cond_test(&s->interlock) != 0) { 234 logslz(sleep_beg, s); 235 tsleep(s, PINTERLOCKED, "slize", 0); 236 logslz(sleep_end, s); 237 } 238 } 239 240 void 241 lwkt_serialize_adaptive_enter(lwkt_serialize_t s) 242 { 243 int try; 244 245 ASSERT_NOT_SERIALIZED(s); 246 logslz(adapt_beg, s); 247 248 if (atomic_intr_cond_try(&s->interlock) == 0) { 249 s->last_td = curthread; 250 logslz(adapt_end, s); 251 return; 252 } 253 254 restart: 255 /* 256 * Spinning a little bit, before going to sleep 257 * 258 * See the comment before kern/kern_spinlock.c 259 * _spin_lock_contested() about why atomic_intr_cond_test() 260 * is called first. atomic_intr_cond_test() contains 261 * _no_ MPLOCKED intruction. 262 */ 263 for (try = SLZ_ADAPTIVE_SPINMAX; try; --try) { 264 if (atomic_intr_cond_test(&s->interlock) == 0 && 265 atomic_intr_cond_try(&s->interlock) == 0) { 266 s->last_td = curthread; 267 logslz_spinend(s, try); 268 return; 269 } 270 } 271 272 atomic_intr_cond_inc(&s->interlock); 273 274 tsleep_interlock(s, 0); 275 if (atomic_intr_cond_try(&s->interlock) == 0) { 276 atomic_intr_cond_dec(&s->interlock); 277 s->last_td = curthread; 278 logslz_spinend(s, 0); 279 return; 280 } else { 281 logslz(adapt_sleepb, s); 282 tsleep(s, PINTERLOCKED, "aslize", 0); 283 logslz(adapt_sleepe, s); 284 285 atomic_intr_cond_dec(&s->interlock); 286 goto restart; 287 } 288 } 289 290 static void 291 lwkt_serialize_wakeup(void *info) 292 { 293 logslz(wakeup_beg, info); 294 wakeup(info); 295 logslz(wakeup_end, info); 296 } 297