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 #ifdef INVARIANTS 126 s->last_td = (void *)-4; 127 #endif 128 s->sleep_cnt = 0; 129 s->tryfail_cnt = 0; 130 s->enter_cnt = 0; 131 s->try_cnt = 0; 132 } 133 134 #ifdef SMP 135 void 136 lwkt_serialize_adaptive_enter(lwkt_serialize_t s) 137 { 138 struct exp_backoff bo; 139 140 bo.backoff = 1; 141 bo.round = 0; 142 bo.s = s; 143 144 ASSERT_NOT_SERIALIZED(s); 145 146 logslz(enter_beg, s); 147 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_adaptive_sleep, &bo); 148 logslz(enter_end, s); 149 #ifdef INVARIANTS 150 s->last_td = curthread; 151 #endif 152 #ifdef PROFILE_SERIALIZER 153 s->enter_cnt++; 154 #endif 155 } 156 #endif /* SMP */ 157 158 void 159 lwkt_serialize_enter(lwkt_serialize_t s) 160 { 161 ASSERT_NOT_SERIALIZED(s); 162 163 logslz(enter_beg, s); 164 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 165 logslz(enter_end, s); 166 #ifdef INVARIANTS 167 s->last_td = curthread; 168 #endif 169 #ifdef PROFILE_SERIALIZER 170 s->enter_cnt++; 171 #endif 172 } 173 174 /* 175 * Returns non-zero on success 176 */ 177 int 178 lwkt_serialize_try(lwkt_serialize_t s) 179 { 180 int error; 181 182 ASSERT_NOT_SERIALIZED(s); 183 184 #ifdef PROFILE_SERIALIZER 185 s->try_cnt++; 186 #endif 187 logslz(try, s); 188 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 189 #ifdef INVARIANTS 190 s->last_td = curthread; 191 #endif 192 logslz(tryok, s); 193 return(1); 194 } 195 #ifdef PROFILE_SERIALIZER 196 s->tryfail_cnt++; 197 #endif 198 logslz(tryfail, s); 199 return (0); 200 } 201 202 void 203 lwkt_serialize_exit(lwkt_serialize_t s) 204 { 205 ASSERT_SERIALIZED(s); 206 #ifdef INVARIANTS 207 s->last_td = (void *)-2; 208 #endif 209 logslz(exit_beg, s); 210 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 211 logslz(exit_end, s); 212 } 213 214 /* 215 * Interrupt handler disablement support, used by drivers. Non-stackable 216 * (uses bit 30). 217 */ 218 void 219 lwkt_serialize_handler_disable(lwkt_serialize_t s) 220 { 221 atomic_intr_handler_disable(&s->interlock); 222 } 223 224 void 225 lwkt_serialize_handler_enable(lwkt_serialize_t s) 226 { 227 atomic_intr_handler_enable(&s->interlock); 228 } 229 230 void 231 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 232 void *arg, void *frame) 233 { 234 /* 235 * note: a return value of 0 indicates that the interrupt handler is 236 * enabled. 237 */ 238 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 239 logslz(enter_beg, s); 240 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 241 logslz(enter_end, s); 242 #ifdef INVARIANTS 243 s->last_td = curthread; 244 #endif 245 #ifdef PROFILE_SERIALIZER 246 s->enter_cnt++; 247 #endif 248 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 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 } 259 } 260 261 /* 262 * Similar to handler_call but does not block. Returns 0 on success, 263 * and 1 on failure. 264 */ 265 int 266 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 267 void *arg, void *frame) 268 { 269 /* 270 * note: a return value of 0 indicates that the interrupt handler is 271 * enabled. 272 */ 273 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 274 #ifdef PROFILE_SERIALIZER 275 s->try_cnt++; 276 #endif 277 logslz(try, s); 278 if (atomic_intr_cond_try(&s->interlock) == 0) { 279 #ifdef INVARIANTS 280 s->last_td = curthread; 281 #endif 282 logslz(tryok, s); 283 284 func(arg, frame); 285 286 ASSERT_SERIALIZED(s); 287 #ifdef INVARIANTS 288 s->last_td = (void *)-2; 289 #endif 290 logslz(exit_beg, s); 291 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 292 logslz(exit_end, s); 293 return(0); 294 } 295 } 296 #ifdef PROFILE_SERIALIZER 297 s->tryfail_cnt++; 298 #endif 299 logslz(tryfail, s); 300 return(1); 301 } 302 303 304 /* 305 * Helper functions 306 * 307 * It is possible to race an interrupt which acquires and releases the 308 * bit, then calls wakeup before we actually go to sleep, so we 309 * need to check that the interlock is still acquired from within 310 * a critical section prior to sleeping. 311 */ 312 static void 313 lwkt_serialize_sleep(void *info) 314 { 315 lwkt_serialize_t s = info; 316 crit_enter(); 317 tsleep_interlock(s); 318 if (atomic_intr_cond_test(&s->interlock) != 0) { 319 #ifdef PROFILE_SERIALIZER 320 s->sleep_cnt++; 321 #endif 322 logslz(sleep_beg, s); 323 tsleep(s, 0, "slize", 0); 324 logslz(sleep_end, s); 325 } 326 crit_exit(); 327 } 328 329 #ifdef SMP 330 331 static void 332 lwkt_serialize_adaptive_sleep(void *arg) 333 { 334 struct exp_backoff *bo = arg; 335 lwkt_serialize_t s = bo->s; 336 int backoff; 337 338 /* 339 * Randomize backoff value 340 */ 341 #ifdef _RDTSC_SUPPORTED_ 342 if (cpu_feature & CPUID_TSC) { 343 backoff = 344 (((u_long)rdtsc() ^ (((u_long)curthread) >> 5)) & 345 (bo->backoff - 1)) + 1; 346 } else 347 #endif 348 backoff = bo->backoff; 349 350 logslz_spinbo(s, bo->backoff, backoff); 351 352 /* 353 * Quick backoff 354 */ 355 for (; backoff; --backoff) 356 cpu_pause(); 357 if (bo->backoff < slz_backoff_limit) { 358 bo->backoff <<= slz_backoff_shift; 359 return; 360 } else { 361 bo->backoff = 1; 362 bo->round++; 363 if (bo->round >= slz_backoff_round) 364 bo->round = 0; 365 else 366 return; 367 } 368 369 crit_enter(); 370 tsleep_interlock(s); 371 if (atomic_intr_cond_test(&s->interlock) != 0) { 372 #ifdef PROFILE_SERIALIZER 373 s->sleep_cnt++; 374 #endif 375 logslz(sleep_beg, s); 376 tsleep(s, 0, "slize", 0); 377 logslz(sleep_end, s); 378 } 379 crit_exit(); 380 } 381 382 #endif /* SMP */ 383 384 static void 385 lwkt_serialize_wakeup(void *info) 386 { 387 logslz(wakeup_beg, info); 388 wakeup(info); 389 logslz(wakeup_end, info); 390 } 391 392 #ifdef SMP 393 static void 394 lwkt_serialize_sysinit(void *dummy __unused) 395 { 396 if (slz_backoff_round <= 0) 397 slz_backoff_round = ncpus * 2; 398 } 399 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND, 400 lwkt_serialize_sysinit, NULL); 401 #endif 402