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