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 * $DragonFly: src/sys/kern/lwkt_serialize.c,v 1.18 2008/10/04 14:22:44 swildner Exp $ 35 */ 36 /* 37 * This API provides a fast locked-bus-cycle-based serializer. It's 38 * basically a low level NON-RECURSIVE exclusive lock that can be held across 39 * a blocking condition. It is NOT a mutex. 40 * 41 * This serializer is primarily designed for low level situations and 42 * interrupt/device interaction. There are two primary facilities. First, 43 * the serializer facility itself. Second, an integrated interrupt handler 44 * disablement facility. 45 */ 46 47 #include "opt_serializer.h" 48 49 #include <sys/param.h> 50 #include <sys/systm.h> 51 #include <sys/kernel.h> 52 #include <sys/proc.h> 53 #include <sys/rtprio.h> 54 #include <sys/queue.h> 55 #include <sys/thread2.h> 56 #include <sys/serialize.h> 57 #include <sys/sysctl.h> 58 #include <sys/ktr.h> 59 #include <sys/kthread.h> 60 #include <machine/cpu.h> 61 #include <machine/cpufunc.h> 62 #include <machine/specialreg.h> 63 #include <sys/lock.h> 64 #include <sys/caps.h> 65 66 struct exp_backoff { 67 int backoff; 68 int round; 69 lwkt_serialize_t s; 70 }; 71 72 #define SLZ_KTR_STRING "slz=%p" 73 #define SLZ_KTR_ARG_SIZE (sizeof(void *)) 74 75 #ifndef KTR_SERIALIZER 76 #define KTR_SERIALIZER KTR_ALL 77 #endif 78 79 KTR_INFO_MASTER(slz); 80 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 81 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 82 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 83 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 84 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 85 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 86 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 87 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 88 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 89 #ifdef SMP 90 KTR_INFO(KTR_SERIALIZER, slz, spinbo, 9, 91 "slz=%p bo1=%d bo=%d", (sizeof(void *) + (2 * sizeof(int)))); 92 #endif 93 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 10, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 94 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 95 96 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz) 97 #ifdef SMP 98 #define logslz_spinbo(slz, bo1, bo) KTR_LOG(slz_spinbo, slz, bo1, bo) 99 #endif 100 101 static void lwkt_serialize_sleep(void *info); 102 static void lwkt_serialize_wakeup(void *info); 103 104 #ifdef SMP 105 static void lwkt_serialize_adaptive_sleep(void *bo); 106 107 static int slz_backoff_limit = 128; 108 SYSCTL_INT(_debug, OID_AUTO, serialize_bolimit, CTLFLAG_RW, 109 &slz_backoff_limit, 0, ""); 110 111 static int slz_backoff_shift = 1; 112 SYSCTL_INT(_debug, OID_AUTO, serialize_boshift, CTLFLAG_RW, 113 &slz_backoff_shift, 0, ""); 114 115 static int slz_backoff_round; 116 TUNABLE_INT("debug.serialize_boround", &slz_backoff_round); 117 SYSCTL_INT(_debug, OID_AUTO, serialize_boround, CTLFLAG_RW, 118 &slz_backoff_round, 0, ""); 119 #endif /* SMP */ 120 121 void 122 lwkt_serialize_init(lwkt_serialize_t s) 123 { 124 atomic_intr_init(&s->interlock); 125 s->last_td = (void *)-4; 126 127 s->sleep_cnt = 0; 128 s->tryfail_cnt = 0; 129 s->enter_cnt = 0; 130 s->try_cnt = 0; 131 } 132 133 #ifdef SMP 134 void 135 lwkt_serialize_adaptive_enter(lwkt_serialize_t s) 136 { 137 struct exp_backoff bo; 138 139 bo.backoff = 1; 140 bo.round = 0; 141 bo.s = s; 142 143 ASSERT_NOT_SERIALIZED(s); 144 145 logslz(enter_beg, s); 146 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_adaptive_sleep, &bo); 147 logslz(enter_end, s); 148 149 s->last_td = curthread; 150 #ifdef PROFILE_SERIALIZER 151 s->enter_cnt++; 152 #endif 153 } 154 #endif /* SMP */ 155 156 void 157 lwkt_serialize_enter(lwkt_serialize_t s) 158 { 159 ASSERT_NOT_SERIALIZED(s); 160 161 logslz(enter_beg, s); 162 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 163 logslz(enter_end, s); 164 165 s->last_td = curthread; 166 #ifdef PROFILE_SERIALIZER 167 s->enter_cnt++; 168 #endif 169 } 170 171 /* 172 * Returns non-zero on success 173 */ 174 int 175 lwkt_serialize_try(lwkt_serialize_t s) 176 { 177 int error; 178 179 ASSERT_NOT_SERIALIZED(s); 180 181 #ifdef PROFILE_SERIALIZER 182 s->try_cnt++; 183 #endif 184 logslz(try, s); 185 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 186 s->last_td = curthread; 187 logslz(tryok, s); 188 return(1); 189 } 190 #ifdef PROFILE_SERIALIZER 191 s->tryfail_cnt++; 192 #endif 193 logslz(tryfail, s); 194 return (0); 195 } 196 197 void 198 lwkt_serialize_exit(lwkt_serialize_t s) 199 { 200 ASSERT_SERIALIZED(s); 201 s->last_td = (void *)-2; 202 203 logslz(exit_beg, s); 204 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 205 logslz(exit_end, s); 206 } 207 208 /* 209 * Interrupt handler disablement support, used by drivers. Non-stackable 210 * (uses bit 30). 211 */ 212 void 213 lwkt_serialize_handler_disable(lwkt_serialize_t s) 214 { 215 atomic_intr_handler_disable(&s->interlock); 216 } 217 218 void 219 lwkt_serialize_handler_enable(lwkt_serialize_t s) 220 { 221 atomic_intr_handler_enable(&s->interlock); 222 } 223 224 void 225 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 226 void *arg, void *frame) 227 { 228 /* 229 * note: a return value of 0 indicates that the interrupt handler is 230 * enabled. 231 */ 232 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 233 logslz(enter_beg, s); 234 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 235 logslz(enter_end, s); 236 237 s->last_td = curthread; 238 #ifdef PROFILE_SERIALIZER 239 s->enter_cnt++; 240 #endif 241 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 242 func(arg, frame); 243 244 ASSERT_SERIALIZED(s); 245 s->last_td = (void *)-2; 246 247 logslz(exit_beg, s); 248 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 249 logslz(exit_end, s); 250 } 251 } 252 253 /* 254 * Similar to handler_call but does not block. Returns 0 on success, 255 * and 1 on failure. 256 */ 257 int 258 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 259 void *arg, void *frame) 260 { 261 /* 262 * note: a return value of 0 indicates that the interrupt handler is 263 * enabled. 264 */ 265 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 266 #ifdef PROFILE_SERIALIZER 267 s->try_cnt++; 268 #endif 269 logslz(try, s); 270 if (atomic_intr_cond_try(&s->interlock) == 0) { 271 s->last_td = curthread; 272 logslz(tryok, s); 273 274 func(arg, frame); 275 276 ASSERT_SERIALIZED(s); 277 s->last_td = (void *)-2; 278 279 logslz(exit_beg, s); 280 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 281 logslz(exit_end, s); 282 return(0); 283 } 284 } 285 #ifdef PROFILE_SERIALIZER 286 s->tryfail_cnt++; 287 #endif 288 logslz(tryfail, s); 289 return(1); 290 } 291 292 293 /* 294 * Helper functions 295 * 296 * It is possible to race an interrupt which acquires and releases the 297 * bit, then calls wakeup before we actually go to sleep, so we 298 * need to check that the interlock is still acquired from within 299 * a critical section prior to sleeping. 300 */ 301 static void 302 lwkt_serialize_sleep(void *info) 303 { 304 lwkt_serialize_t s = info; 305 crit_enter(); 306 tsleep_interlock(s); 307 if (atomic_intr_cond_test(&s->interlock) != 0) { 308 #ifdef PROFILE_SERIALIZER 309 s->sleep_cnt++; 310 #endif 311 logslz(sleep_beg, s); 312 tsleep(s, 0, "slize", 0); 313 logslz(sleep_end, s); 314 } 315 crit_exit(); 316 } 317 318 #ifdef SMP 319 320 static void 321 lwkt_serialize_adaptive_sleep(void *arg) 322 { 323 struct exp_backoff *bo = arg; 324 lwkt_serialize_t s = bo->s; 325 int backoff; 326 327 /* 328 * Randomize backoff value 329 */ 330 #ifdef _RDTSC_SUPPORTED_ 331 if (cpu_feature & CPUID_TSC) { 332 backoff = 333 (((u_long)rdtsc() ^ (((u_long)curthread) >> 5)) & 334 (bo->backoff - 1)) + 1; 335 } else 336 #endif 337 backoff = bo->backoff; 338 339 logslz_spinbo(s, bo->backoff, backoff); 340 341 /* 342 * Quick backoff 343 */ 344 for (; backoff; --backoff) 345 cpu_pause(); 346 if (bo->backoff < slz_backoff_limit) { 347 bo->backoff <<= slz_backoff_shift; 348 return; 349 } else { 350 bo->backoff = 1; 351 bo->round++; 352 if (bo->round >= slz_backoff_round) 353 bo->round = 0; 354 else 355 return; 356 } 357 358 crit_enter(); 359 tsleep_interlock(s); 360 if (atomic_intr_cond_test(&s->interlock) != 0) { 361 #ifdef PROFILE_SERIALIZER 362 s->sleep_cnt++; 363 #endif 364 logslz(sleep_beg, s); 365 tsleep(s, 0, "slize", 0); 366 logslz(sleep_end, s); 367 } 368 crit_exit(); 369 } 370 371 #endif /* SMP */ 372 373 static void 374 lwkt_serialize_wakeup(void *info) 375 { 376 logslz(wakeup_beg, info); 377 wakeup(info); 378 logslz(wakeup_end, info); 379 } 380 381 #ifdef SMP 382 static void 383 lwkt_serialize_sysinit(void *dummy __unused) 384 { 385 if (slz_backoff_round <= 0) 386 slz_backoff_round = ncpus * 2; 387 } 388 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND, 389 lwkt_serialize_sysinit, NULL); 390 #endif 391