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_ARGS lwkt_serialize_t slz 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_ARGS); 79 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS); 80 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS); 81 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS); 82 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS); 83 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS); 84 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS); 85 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS); 86 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS); 87 #ifdef SMP 88 KTR_INFO(KTR_SERIALIZER, slz, spinbo, 9, 89 "slz=%p bo1=%d bo=%d", lwkt_serialize_t slz, int backoff1, int backoff); 90 #endif 91 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS); 92 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS); 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, "Backoff limit"); 108 109 static int slz_backoff_shift = 1; 110 SYSCTL_INT(_debug, OID_AUTO, serialize_boshift, CTLFLAG_RW, 111 &slz_backoff_shift, 0, "Backoff shift"); 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 "Backoff rounding"); 118 #endif /* SMP */ 119 120 void 121 lwkt_serialize_init(lwkt_serialize_t s) 122 { 123 atomic_intr_init(&s->interlock); 124 #ifdef INVARIANTS 125 s->last_td = (void *)-4; 126 #endif 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 #ifdef INVARIANTS 145 s->last_td = curthread; 146 #endif 147 } 148 #endif /* SMP */ 149 150 void 151 lwkt_serialize_enter(lwkt_serialize_t s) 152 { 153 ASSERT_NOT_SERIALIZED(s); 154 155 logslz(enter_beg, s); 156 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 157 logslz(enter_end, s); 158 #ifdef INVARIANTS 159 s->last_td = curthread; 160 #endif 161 } 162 163 /* 164 * Returns non-zero on success 165 */ 166 int 167 lwkt_serialize_try(lwkt_serialize_t s) 168 { 169 int error; 170 171 ASSERT_NOT_SERIALIZED(s); 172 173 logslz(try, s); 174 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) { 175 #ifdef INVARIANTS 176 s->last_td = curthread; 177 #endif 178 logslz(tryok, s); 179 return(1); 180 } 181 logslz(tryfail, s); 182 return (0); 183 } 184 185 void 186 lwkt_serialize_exit(lwkt_serialize_t s) 187 { 188 ASSERT_SERIALIZED(s); 189 #ifdef INVARIANTS 190 s->last_td = (void *)-2; 191 #endif 192 logslz(exit_beg, s); 193 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 194 logslz(exit_end, s); 195 } 196 197 /* 198 * Interrupt handler disablement support, used by drivers. Non-stackable 199 * (uses bit 30). 200 */ 201 void 202 lwkt_serialize_handler_disable(lwkt_serialize_t s) 203 { 204 atomic_intr_handler_disable(&s->interlock); 205 } 206 207 void 208 lwkt_serialize_handler_enable(lwkt_serialize_t s) 209 { 210 atomic_intr_handler_enable(&s->interlock); 211 } 212 213 void 214 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 215 void *arg, void *frame) 216 { 217 /* 218 * note: a return value of 0 indicates that the interrupt handler is 219 * enabled. 220 */ 221 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 222 logslz(enter_beg, s); 223 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 224 logslz(enter_end, s); 225 #ifdef INVARIANTS 226 s->last_td = curthread; 227 #endif 228 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 229 func(arg, frame); 230 231 ASSERT_SERIALIZED(s); 232 #ifdef INVARIANTS 233 s->last_td = (void *)-2; 234 #endif 235 logslz(exit_beg, s); 236 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 237 logslz(exit_end, s); 238 } 239 } 240 241 /* 242 * Similar to handler_call but does not block. Returns 0 on success, 243 * and 1 on failure. 244 */ 245 int 246 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 247 void *arg, void *frame) 248 { 249 /* 250 * note: a return value of 0 indicates that the interrupt handler is 251 * enabled. 252 */ 253 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 254 logslz(try, s); 255 if (atomic_intr_cond_try(&s->interlock) == 0) { 256 #ifdef INVARIANTS 257 s->last_td = curthread; 258 #endif 259 logslz(tryok, s); 260 261 func(arg, frame); 262 263 ASSERT_SERIALIZED(s); 264 #ifdef INVARIANTS 265 s->last_td = (void *)-2; 266 #endif 267 logslz(exit_beg, s); 268 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 269 logslz(exit_end, s); 270 return(0); 271 } 272 } 273 logslz(tryfail, s); 274 return(1); 275 } 276 277 278 /* 279 * Helper functions 280 * 281 * It is possible to race an interrupt which acquires and releases the 282 * bit, then calls wakeup before we actually go to sleep, so we 283 * need to check that the interlock is still acquired from within 284 * a critical section prior to sleeping. 285 */ 286 static void 287 lwkt_serialize_sleep(void *info) 288 { 289 lwkt_serialize_t s = info; 290 291 tsleep_interlock(s, 0); 292 if (atomic_intr_cond_test(&s->interlock) != 0) { 293 logslz(sleep_beg, s); 294 tsleep(s, PINTERLOCKED, "slize", 0); 295 logslz(sleep_end, s); 296 } 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 tsleep_interlock(s, 0); 340 if (atomic_intr_cond_test(&s->interlock) != 0) { 341 logslz(sleep_beg, s); 342 tsleep(s, PINTERLOCKED, "slize", 0); 343 logslz(sleep_end, s); 344 } 345 } 346 347 #endif /* SMP */ 348 349 static void 350 lwkt_serialize_wakeup(void *info) 351 { 352 logslz(wakeup_beg, info); 353 wakeup(info); 354 logslz(wakeup_end, info); 355 } 356 357 #ifdef SMP 358 static void 359 lwkt_serialize_sysinit(void *dummy __unused) 360 { 361 if (slz_backoff_round <= 0) 362 slz_backoff_round = ncpus * 2; 363 } 364 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND, 365 lwkt_serialize_sysinit, NULL); 366 #endif 367