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 1.17 2008/05/24 12:52:49 sephe 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 KTR_INFO(KTR_SERIALIZER, slz, spinbo, 9, 90 "slz=%p bo1=%d bo=%d", (sizeof(void *) + (2 * sizeof(int)))); 91 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 10, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 92 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE); 93 94 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz) 95 #define logslz_spinbo(slz, bo1, bo) KTR_LOG(slz_spinbo, slz, bo1, bo) 96 97 static void lwkt_serialize_sleep(void *info); 98 static void lwkt_serialize_wakeup(void *info); 99 100 #ifdef SMP 101 static void lwkt_serialize_adaptive_sleep(void *bo); 102 103 static int slz_backoff_limit = 128; 104 SYSCTL_INT(_debug, OID_AUTO, serialize_bolimit, CTLFLAG_RW, 105 &slz_backoff_limit, 0, ""); 106 107 static int slz_backoff_shift = 1; 108 SYSCTL_INT(_debug, OID_AUTO, serialize_boshift, CTLFLAG_RW, 109 &slz_backoff_shift, 0, ""); 110 111 static int slz_backoff_round; 112 TUNABLE_INT("debug.serialize_boround", &slz_backoff_round); 113 SYSCTL_INT(_debug, OID_AUTO, serialize_boround, CTLFLAG_RW, 114 &slz_backoff_round, 0, ""); 115 #endif /* SMP */ 116 117 void 118 lwkt_serialize_init(lwkt_serialize_t s) 119 { 120 atomic_intr_init(&s->interlock); 121 s->last_td = (void *)-4; 122 123 s->sleep_cnt = 0; 124 s->tryfail_cnt = 0; 125 s->enter_cnt = 0; 126 s->try_cnt = 0; 127 } 128 129 #ifdef SMP 130 void 131 lwkt_serialize_adaptive_enter(lwkt_serialize_t s) 132 { 133 struct exp_backoff bo; 134 135 bo.backoff = 1; 136 bo.round = 0; 137 bo.s = s; 138 139 ASSERT_NOT_SERIALIZED(s); 140 141 logslz(enter_beg, s); 142 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_adaptive_sleep, &bo); 143 logslz(enter_end, s); 144 145 s->last_td = curthread; 146 #ifdef PROFILE_SERIALIZER 147 s->enter_cnt++; 148 #endif 149 } 150 #endif /* SMP */ 151 152 void 153 lwkt_serialize_enter(lwkt_serialize_t s) 154 { 155 ASSERT_NOT_SERIALIZED(s); 156 157 logslz(enter_beg, s); 158 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 159 logslz(enter_end, s); 160 161 s->last_td = curthread; 162 #ifdef PROFILE_SERIALIZER 163 s->enter_cnt++; 164 #endif 165 } 166 167 /* 168 * Returns non-zero on success 169 */ 170 int 171 lwkt_serialize_try(lwkt_serialize_t s) 172 { 173 int error; 174 175 ASSERT_NOT_SERIALIZED(s); 176 177 #ifdef PROFILE_SERIALIZER 178 s->try_cnt++; 179 #endif 180 logslz(try, s); 181 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 182 s->last_td = curthread; 183 logslz(tryok, s); 184 return(1); 185 } 186 #ifdef PROFILE_SERIALIZER 187 s->tryfail_cnt++; 188 #endif 189 logslz(tryfail, s); 190 return (0); 191 } 192 193 void 194 lwkt_serialize_exit(lwkt_serialize_t s) 195 { 196 ASSERT_SERIALIZED(s); 197 s->last_td = (void *)-2; 198 199 logslz(exit_beg, s); 200 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 201 logslz(exit_end, s); 202 } 203 204 /* 205 * Interrupt handler disablement support, used by drivers. Non-stackable 206 * (uses bit 30). 207 */ 208 void 209 lwkt_serialize_handler_disable(lwkt_serialize_t s) 210 { 211 atomic_intr_handler_disable(&s->interlock); 212 } 213 214 void 215 lwkt_serialize_handler_enable(lwkt_serialize_t s) 216 { 217 atomic_intr_handler_enable(&s->interlock); 218 } 219 220 void 221 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 222 void *arg, void *frame) 223 { 224 /* 225 * note: a return value of 0 indicates that the interrupt handler is 226 * enabled. 227 */ 228 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 229 logslz(enter_beg, s); 230 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 231 logslz(enter_end, s); 232 233 s->last_td = curthread; 234 #ifdef PROFILE_SERIALIZER 235 s->enter_cnt++; 236 #endif 237 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 238 func(arg, frame); 239 240 ASSERT_SERIALIZED(s); 241 s->last_td = (void *)-2; 242 243 logslz(exit_beg, s); 244 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 245 logslz(exit_end, s); 246 } 247 } 248 249 /* 250 * Similar to handler_call but does not block. Returns 0 on success, 251 * and 1 on failure. 252 */ 253 int 254 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 255 void *arg, void *frame) 256 { 257 /* 258 * note: a return value of 0 indicates that the interrupt handler is 259 * enabled. 260 */ 261 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 262 #ifdef PROFILE_SERIALIZER 263 s->try_cnt++; 264 #endif 265 logslz(try, s); 266 if (atomic_intr_cond_try(&s->interlock) == 0) { 267 s->last_td = curthread; 268 logslz(tryok, s); 269 270 func(arg, frame); 271 272 ASSERT_SERIALIZED(s); 273 s->last_td = (void *)-2; 274 275 logslz(exit_beg, s); 276 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 277 logslz(exit_end, s); 278 return(0); 279 } 280 } 281 #ifdef PROFILE_SERIALIZER 282 s->tryfail_cnt++; 283 #endif 284 logslz(tryfail, s); 285 return(1); 286 } 287 288 289 /* 290 * Helper functions 291 * 292 * It is possible to race an interrupt which acquires and releases the 293 * bit, then calls wakeup before we actually go to sleep, so we 294 * need to check that the interlock is still acquired from within 295 * a critical section prior to sleeping. 296 */ 297 static void 298 lwkt_serialize_sleep(void *info) 299 { 300 lwkt_serialize_t s = info; 301 crit_enter(); 302 tsleep_interlock(s); 303 if (atomic_intr_cond_test(&s->interlock) != 0) { 304 #ifdef PROFILE_SERIALIZER 305 s->sleep_cnt++; 306 #endif 307 logslz(sleep_beg, s); 308 tsleep(s, 0, "slize", 0); 309 logslz(sleep_end, s); 310 } 311 crit_exit(); 312 } 313 314 #ifdef SMP 315 316 static void 317 lwkt_serialize_adaptive_sleep(void *arg) 318 { 319 struct exp_backoff *bo = arg; 320 lwkt_serialize_t s = bo->s; 321 int backoff; 322 323 /* 324 * Randomize backoff value 325 */ 326 #ifdef _RDTSC_SUPPORTED_ 327 if (cpu_feature & CPUID_TSC) { 328 backoff = 329 (((u_long)rdtsc() ^ (((u_long)curthread) >> 5)) & 330 (bo->backoff - 1)) + 1; 331 } else 332 #endif 333 backoff = bo->backoff; 334 335 logslz_spinbo(s, bo->backoff, backoff); 336 337 /* 338 * Quick backoff 339 */ 340 for (; backoff; --backoff) 341 cpu_pause(); 342 if (bo->backoff < slz_backoff_limit) { 343 bo->backoff <<= slz_backoff_shift; 344 return; 345 } else { 346 bo->backoff = 1; 347 bo->round++; 348 if (bo->round >= slz_backoff_round) 349 bo->round = 0; 350 else 351 return; 352 } 353 354 crit_enter(); 355 tsleep_interlock(s); 356 if (atomic_intr_cond_test(&s->interlock) != 0) { 357 #ifdef PROFILE_SERIALIZER 358 s->sleep_cnt++; 359 #endif 360 logslz(sleep_beg, s); 361 tsleep(s, 0, "slize", 0); 362 logslz(sleep_end, s); 363 } 364 crit_exit(); 365 } 366 367 #endif /* SMP */ 368 369 static void 370 lwkt_serialize_wakeup(void *info) 371 { 372 logslz(wakeup_beg, info); 373 wakeup(info); 374 logslz(wakeup_end, info); 375 } 376 377 #ifdef SMP 378 static void 379 lwkt_serialize_sysinit(void *dummy __unused) 380 { 381 if (slz_backoff_round <= 0) 382 slz_backoff_round = ncpus * 2; 383 } 384 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND, 385 lwkt_serialize_sysinit, NULL); 386 #endif 387