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 <sys/lock.h> 60 61 struct exp_backoff { 62 int backoff; 63 int round; 64 lwkt_serialize_t s; 65 }; 66 67 #define SLZ_KTR_STRING "slz=%p" 68 #define SLZ_KTR_ARGS lwkt_serialize_t slz 69 70 #ifndef KTR_SERIALIZER 71 #define KTR_SERIALIZER KTR_ALL 72 #endif 73 74 KTR_INFO_MASTER(slz); 75 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS); 76 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS); 77 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS); 78 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS); 79 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS); 80 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS); 81 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS); 82 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS); 83 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS); 84 KTR_INFO(KTR_SERIALIZER, slz, spinbo, 9, 85 "slz=%p bo1=%d bo=%d", lwkt_serialize_t slz, int backoff1, int backoff); 86 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS); 87 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS); 88 89 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz) 90 #define logslz_spinbo(slz, bo1, bo) KTR_LOG(slz_spinbo, slz, bo1, bo) 91 92 static void lwkt_serialize_sleep(void *info); 93 static void lwkt_serialize_wakeup(void *info); 94 static void lwkt_serialize_adaptive_sleep(void *bo); 95 96 static int slz_backoff_limit = 128; 97 SYSCTL_INT(_debug, OID_AUTO, serialize_bolimit, CTLFLAG_RW, 98 &slz_backoff_limit, 0, "Backoff limit"); 99 100 static int slz_backoff_shift = 1; 101 SYSCTL_INT(_debug, OID_AUTO, serialize_boshift, CTLFLAG_RW, 102 &slz_backoff_shift, 0, "Backoff shift"); 103 104 static int slz_backoff_round; 105 TUNABLE_INT("debug.serialize_boround", &slz_backoff_round); 106 SYSCTL_INT(_debug, OID_AUTO, serialize_boround, CTLFLAG_RW, 107 &slz_backoff_round, 0, 108 "Backoff rounding"); 109 110 void 111 lwkt_serialize_init(lwkt_serialize_t s) 112 { 113 atomic_intr_init(&s->interlock); 114 #ifdef INVARIANTS 115 s->last_td = (void *)-4; 116 #endif 117 } 118 119 void 120 lwkt_serialize_adaptive_enter(lwkt_serialize_t s) 121 { 122 struct exp_backoff bo; 123 124 bo.backoff = 1; 125 bo.round = 0; 126 bo.s = s; 127 128 ASSERT_NOT_SERIALIZED(s); 129 130 logslz(enter_beg, s); 131 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_adaptive_sleep, &bo); 132 logslz(enter_end, s); 133 #ifdef INVARIANTS 134 s->last_td = curthread; 135 #endif 136 } 137 138 void 139 lwkt_serialize_enter(lwkt_serialize_t s) 140 { 141 ASSERT_NOT_SERIALIZED(s); 142 143 logslz(enter_beg, s); 144 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 145 logslz(enter_end, s); 146 #ifdef INVARIANTS 147 s->last_td = curthread; 148 #endif 149 } 150 151 /* 152 * Returns non-zero on success 153 */ 154 int 155 lwkt_serialize_try(lwkt_serialize_t s) 156 { 157 int error; 158 159 ASSERT_NOT_SERIALIZED(s); 160 161 logslz(try, s); 162 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 163 #ifdef INVARIANTS 164 s->last_td = curthread; 165 #endif 166 logslz(tryok, s); 167 return(1); 168 } 169 logslz(tryfail, s); 170 return (0); 171 } 172 173 void 174 lwkt_serialize_exit(lwkt_serialize_t s) 175 { 176 ASSERT_SERIALIZED(s); 177 #ifdef INVARIANTS 178 s->last_td = (void *)-2; 179 #endif 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 * Interrupt handler disablement support, used by drivers. Non-stackable 187 * (uses bit 30). 188 */ 189 void 190 lwkt_serialize_handler_disable(lwkt_serialize_t s) 191 { 192 atomic_intr_handler_disable(&s->interlock); 193 } 194 195 void 196 lwkt_serialize_handler_enable(lwkt_serialize_t s) 197 { 198 atomic_intr_handler_enable(&s->interlock); 199 } 200 201 void 202 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 203 void *arg, void *frame) 204 { 205 /* 206 * note: a return value of 0 indicates that the interrupt handler is 207 * enabled. 208 */ 209 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 210 logslz(enter_beg, s); 211 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 212 logslz(enter_end, s); 213 #ifdef INVARIANTS 214 s->last_td = curthread; 215 #endif 216 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 217 func(arg, frame); 218 219 ASSERT_SERIALIZED(s); 220 #ifdef INVARIANTS 221 s->last_td = (void *)-2; 222 #endif 223 logslz(exit_beg, s); 224 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 225 logslz(exit_end, s); 226 } 227 } 228 229 /* 230 * Similar to handler_call but does not block. Returns 0 on success, 231 * and 1 on failure. 232 */ 233 int 234 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 235 void *arg, void *frame) 236 { 237 /* 238 * note: a return value of 0 indicates that the interrupt handler is 239 * enabled. 240 */ 241 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 242 logslz(try, s); 243 if (atomic_intr_cond_try(&s->interlock) == 0) { 244 #ifdef INVARIANTS 245 s->last_td = curthread; 246 #endif 247 logslz(tryok, s); 248 249 func(arg, frame); 250 251 ASSERT_SERIALIZED(s); 252 #ifdef INVARIANTS 253 s->last_td = (void *)-2; 254 #endif 255 logslz(exit_beg, s); 256 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 257 logslz(exit_end, s); 258 return(0); 259 } 260 } 261 logslz(tryfail, s); 262 return(1); 263 } 264 265 266 /* 267 * Helper functions 268 * 269 * It is possible to race an interrupt which acquires and releases the 270 * bit, then calls wakeup before we actually go to sleep, so we 271 * need to check that the interlock is still acquired from within 272 * a critical section prior to sleeping. 273 */ 274 static void 275 lwkt_serialize_sleep(void *info) 276 { 277 lwkt_serialize_t s = info; 278 279 tsleep_interlock(s, 0); 280 if (atomic_intr_cond_test(&s->interlock) != 0) { 281 logslz(sleep_beg, s); 282 tsleep(s, PINTERLOCKED, "slize", 0); 283 logslz(sleep_end, s); 284 } 285 } 286 287 static void 288 lwkt_serialize_adaptive_sleep(void *arg) 289 { 290 struct exp_backoff *bo = arg; 291 lwkt_serialize_t s = bo->s; 292 int backoff; 293 294 /* 295 * Randomize backoff value 296 */ 297 #ifdef _RDTSC_SUPPORTED_ 298 if (cpu_feature & CPUID_TSC) { 299 backoff = 300 (((u_long)rdtsc() ^ (((u_long)curthread) >> 5)) & 301 (bo->backoff - 1)) + 1; 302 } else 303 #endif 304 backoff = bo->backoff; 305 306 logslz_spinbo(s, bo->backoff, backoff); 307 308 /* 309 * Quick backoff 310 */ 311 for (; backoff; --backoff) 312 cpu_pause(); 313 if (bo->backoff < slz_backoff_limit) { 314 bo->backoff <<= slz_backoff_shift; 315 return; 316 } else { 317 bo->backoff = 1; 318 bo->round++; 319 if (bo->round >= slz_backoff_round) 320 bo->round = 0; 321 else 322 return; 323 } 324 325 tsleep_interlock(s, 0); 326 if (atomic_intr_cond_test(&s->interlock) != 0) { 327 logslz(sleep_beg, s); 328 tsleep(s, PINTERLOCKED, "slize", 0); 329 logslz(sleep_end, s); 330 } 331 } 332 333 static void 334 lwkt_serialize_wakeup(void *info) 335 { 336 logslz(wakeup_beg, info); 337 wakeup(info); 338 logslz(wakeup_end, info); 339 } 340 341 static void 342 lwkt_serialize_sysinit(void *dummy __unused) 343 { 344 if (slz_backoff_round <= 0) 345 slz_backoff_round = ncpus * 2; 346 } 347 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND, 348 lwkt_serialize_sysinit, NULL); 349