1 /*- 2 * Copyright (c) 2001 3 * John Baldwin <jhb@FreeBSD.org>. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the author nor the names of any co-contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY JOHN BALDWIN AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL JOHN BALDWIN OR THE VOICES IN HIS HEAD 21 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 27 * THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 /* 31 * This module holds the global variables and machine independent functions 32 * used for the kernel SMP support. 33 */ 34 35 #include <sys/cdefs.h> 36 __FBSDID("$FreeBSD$"); 37 38 #include "opt_kdb.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/kernel.h> 43 #include <sys/ktr.h> 44 #include <sys/proc.h> 45 #include <sys/bus.h> 46 #include <sys/lock.h> 47 #include <sys/mutex.h> 48 #include <sys/pcpu.h> 49 #include <sys/smp.h> 50 #include <sys/sysctl.h> 51 52 #include <machine/smp.h> 53 54 #include "opt_sched.h" 55 56 #ifdef SMP 57 volatile cpumask_t stopped_cpus; 58 volatile cpumask_t started_cpus; 59 cpumask_t idle_cpus_mask; 60 cpumask_t hlt_cpus_mask; 61 cpumask_t logical_cpus_mask; 62 63 void (*cpustop_restartfunc)(void); 64 #endif 65 /* This is used in modules that need to work in both SMP and UP. */ 66 cpumask_t all_cpus; 67 68 int mp_ncpus; 69 /* export this for libkvm consumers. */ 70 int mp_maxcpus = MAXCPU; 71 72 struct cpu_top *smp_topology; 73 volatile int smp_started; 74 u_int mp_maxid; 75 76 SYSCTL_NODE(_kern, OID_AUTO, smp, CTLFLAG_RD, NULL, "Kernel SMP"); 77 78 SYSCTL_INT(_kern_smp, OID_AUTO, maxcpus, CTLFLAG_RD, &mp_maxcpus, 0, 79 "Max number of CPUs that the system was compiled for."); 80 81 int smp_active = 0; /* are the APs allowed to run? */ 82 SYSCTL_INT(_kern_smp, OID_AUTO, active, CTLFLAG_RW, &smp_active, 0, 83 "Number of Auxillary Processors (APs) that were successfully started"); 84 85 int smp_disabled = 0; /* has smp been disabled? */ 86 SYSCTL_INT(_kern_smp, OID_AUTO, disabled, CTLFLAG_RDTUN, &smp_disabled, 0, 87 "SMP has been disabled from the loader"); 88 TUNABLE_INT("kern.smp.disabled", &smp_disabled); 89 90 int smp_cpus = 1; /* how many cpu's running */ 91 SYSCTL_INT(_kern_smp, OID_AUTO, cpus, CTLFLAG_RD, &smp_cpus, 0, 92 "Number of CPUs online"); 93 94 #ifdef SMP 95 /* Enable forwarding of a signal to a process running on a different CPU */ 96 static int forward_signal_enabled = 1; 97 SYSCTL_INT(_kern_smp, OID_AUTO, forward_signal_enabled, CTLFLAG_RW, 98 &forward_signal_enabled, 0, 99 "Forwarding of a signal to a process on a different CPU"); 100 101 /* Enable forwarding of roundrobin to all other cpus */ 102 static int forward_roundrobin_enabled = 1; 103 SYSCTL_INT(_kern_smp, OID_AUTO, forward_roundrobin_enabled, CTLFLAG_RW, 104 &forward_roundrobin_enabled, 0, 105 "Forwarding of roundrobin to all other CPUs"); 106 107 /* Variables needed for SMP rendezvous. */ 108 static void (*smp_rv_setup_func)(void *arg); 109 static void (*smp_rv_action_func)(void *arg); 110 static void (*smp_rv_teardown_func)(void *arg); 111 static void *smp_rv_func_arg; 112 static volatile int smp_rv_waiters[2]; 113 114 /* 115 * Shared mutex to restrict busywaits between smp_rendezvous() and 116 * smp(_targeted)_tlb_shootdown(). A deadlock occurs if both of these 117 * functions trigger at once and cause multiple CPUs to busywait with 118 * interrupts disabled. 119 */ 120 struct mtx smp_ipi_mtx; 121 122 /* 123 * Let the MD SMP code initialize mp_maxid very early if it can. 124 */ 125 static void 126 mp_setmaxid(void *dummy) 127 { 128 cpu_mp_setmaxid(); 129 } 130 SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL) 131 132 /* 133 * Call the MD SMP initialization code. 134 */ 135 static void 136 mp_start(void *dummy) 137 { 138 139 /* Probe for MP hardware. */ 140 if (smp_disabled != 0 || cpu_mp_probe() == 0) { 141 mp_ncpus = 1; 142 all_cpus = PCPU_GET(cpumask); 143 return; 144 } 145 146 mtx_init(&smp_ipi_mtx, "smp rendezvous", NULL, MTX_SPIN); 147 cpu_mp_start(); 148 printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n", 149 mp_ncpus); 150 cpu_mp_announce(); 151 } 152 SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_SECOND, mp_start, NULL) 153 154 void 155 forward_signal(struct thread *td) 156 { 157 int id; 158 159 /* 160 * signotify() has already set TDF_ASTPENDING and TDF_NEEDSIGCHECK on 161 * this thread, so all we need to do is poke it if it is currently 162 * executing so that it executes ast(). 163 */ 164 mtx_assert(&sched_lock, MA_OWNED); 165 KASSERT(TD_IS_RUNNING(td), 166 ("forward_signal: thread is not TDS_RUNNING")); 167 168 CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc); 169 170 if (!smp_started || cold || panicstr) 171 return; 172 if (!forward_signal_enabled) 173 return; 174 175 /* No need to IPI ourself. */ 176 if (td == curthread) 177 return; 178 179 id = td->td_oncpu; 180 if (id == NOCPU) 181 return; 182 ipi_selected(1 << id, IPI_AST); 183 } 184 185 void 186 forward_roundrobin(void) 187 { 188 struct pcpu *pc; 189 struct thread *td; 190 cpumask_t id, map, me; 191 192 mtx_assert(&sched_lock, MA_OWNED); 193 194 CTR0(KTR_SMP, "forward_roundrobin()"); 195 196 if (!smp_started || cold || panicstr) 197 return; 198 if (!forward_roundrobin_enabled) 199 return; 200 map = 0; 201 me = PCPU_GET(cpumask); 202 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { 203 td = pc->pc_curthread; 204 id = pc->pc_cpumask; 205 if (id != me && (id & stopped_cpus) == 0 && 206 td != pc->pc_idlethread) { 207 td->td_flags |= TDF_NEEDRESCHED; 208 map |= id; 209 } 210 } 211 ipi_selected(map, IPI_AST); 212 } 213 214 /* 215 * When called the executing CPU will send an IPI to all other CPUs 216 * requesting that they halt execution. 217 * 218 * Usually (but not necessarily) called with 'other_cpus' as its arg. 219 * 220 * - Signals all CPUs in map to stop. 221 * - Waits for each to stop. 222 * 223 * Returns: 224 * -1: error 225 * 0: NA 226 * 1: ok 227 * 228 * XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs 229 * from executing at same time. 230 */ 231 int 232 stop_cpus(cpumask_t map) 233 { 234 int i; 235 236 if (!smp_started) 237 return 0; 238 239 CTR1(KTR_SMP, "stop_cpus(%x)", map); 240 241 /* send the stop IPI to all CPUs in map */ 242 ipi_selected(map, IPI_STOP); 243 244 i = 0; 245 while ((atomic_load_acq_int(&stopped_cpus) & map) != map) { 246 /* spin */ 247 i++; 248 #ifdef DIAGNOSTIC 249 if (i == 100000) { 250 printf("timeout stopping cpus\n"); 251 break; 252 } 253 #endif 254 } 255 256 return 1; 257 } 258 259 #ifdef KDB_STOP_NMI 260 int 261 stop_cpus_nmi(cpumask_t map) 262 { 263 int i; 264 265 if (!smp_started) 266 return 0; 267 268 CTR1(KTR_SMP, "stop_cpus(%x)", map); 269 270 /* send the stop IPI to all CPUs in map */ 271 ipi_nmi_selected(map); 272 273 i = 0; 274 while ((atomic_load_acq_int(&stopped_cpus) & map) != map) { 275 /* spin */ 276 i++; 277 #ifdef DIAGNOSTIC 278 if (i == 100000) { 279 printf("timeout stopping cpus\n"); 280 break; 281 } 282 #endif 283 } 284 285 return 1; 286 } 287 #endif /* KDB_STOP_NMI */ 288 289 /* 290 * Called by a CPU to restart stopped CPUs. 291 * 292 * Usually (but not necessarily) called with 'stopped_cpus' as its arg. 293 * 294 * - Signals all CPUs in map to restart. 295 * - Waits for each to restart. 296 * 297 * Returns: 298 * -1: error 299 * 0: NA 300 * 1: ok 301 */ 302 int 303 restart_cpus(cpumask_t map) 304 { 305 306 if (!smp_started) 307 return 0; 308 309 CTR1(KTR_SMP, "restart_cpus(%x)", map); 310 311 /* signal other cpus to restart */ 312 atomic_store_rel_int(&started_cpus, map); 313 314 /* wait for each to clear its bit */ 315 while ((atomic_load_acq_int(&stopped_cpus) & map) != 0) 316 ; /* nothing */ 317 318 return 1; 319 } 320 321 /* 322 * All-CPU rendezvous. CPUs are signalled, all execute the setup function 323 * (if specified), rendezvous, execute the action function (if specified), 324 * rendezvous again, execute the teardown function (if specified), and then 325 * resume. 326 * 327 * Note that the supplied external functions _must_ be reentrant and aware 328 * that they are running in parallel and in an unknown lock context. 329 */ 330 void 331 smp_rendezvous_action(void) 332 { 333 334 /* setup function */ 335 if (smp_rv_setup_func != NULL) 336 smp_rv_setup_func(smp_rv_func_arg); 337 /* spin on entry rendezvous */ 338 atomic_add_int(&smp_rv_waiters[0], 1); 339 while (atomic_load_acq_int(&smp_rv_waiters[0]) < mp_ncpus) 340 ; /* nothing */ 341 /* action function */ 342 if (smp_rv_action_func != NULL) 343 smp_rv_action_func(smp_rv_func_arg); 344 /* spin on exit rendezvous */ 345 atomic_add_int(&smp_rv_waiters[1], 1); 346 while (atomic_load_acq_int(&smp_rv_waiters[1]) < mp_ncpus) 347 ; /* nothing */ 348 /* teardown function */ 349 if (smp_rv_teardown_func != NULL) 350 smp_rv_teardown_func(smp_rv_func_arg); 351 } 352 353 void 354 smp_rendezvous(void (* setup_func)(void *), 355 void (* action_func)(void *), 356 void (* teardown_func)(void *), 357 void *arg) 358 { 359 360 if (!smp_started) { 361 if (setup_func != NULL) 362 setup_func(arg); 363 if (action_func != NULL) 364 action_func(arg); 365 if (teardown_func != NULL) 366 teardown_func(arg); 367 return; 368 } 369 370 /* obtain rendezvous lock */ 371 mtx_lock_spin(&smp_ipi_mtx); 372 373 /* set static function pointers */ 374 smp_rv_setup_func = setup_func; 375 smp_rv_action_func = action_func; 376 smp_rv_teardown_func = teardown_func; 377 smp_rv_func_arg = arg; 378 smp_rv_waiters[0] = 0; 379 smp_rv_waiters[1] = 0; 380 381 /* signal other processors, which will enter the IPI with interrupts off */ 382 ipi_all_but_self(IPI_RENDEZVOUS); 383 384 /* call executor function */ 385 smp_rendezvous_action(); 386 387 /* release lock */ 388 mtx_unlock_spin(&smp_ipi_mtx); 389 } 390 #else /* !SMP */ 391 392 /* 393 * Provide dummy SMP support for UP kernels. Modules that need to use SMP 394 * APIs will still work using this dummy support. 395 */ 396 static void 397 mp_setvariables_for_up(void *dummy) 398 { 399 mp_ncpus = 1; 400 mp_maxid = PCPU_GET(cpuid); 401 all_cpus = PCPU_GET(cpumask); 402 KASSERT(PCPU_GET(cpuid) == 0, ("UP must have a CPU ID of zero")); 403 } 404 SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST, 405 mp_setvariables_for_up, NULL) 406 407 void 408 smp_rendezvous(void (* setup_func)(void *), 409 void (* action_func)(void *), 410 void (* teardown_func)(void *), 411 void *arg) 412 { 413 414 if (setup_func != NULL) 415 setup_func(arg); 416 if (action_func != NULL) 417 action_func(arg); 418 if (teardown_func != NULL) 419 teardown_func(arg); 420 } 421 #endif /* SMP */ 422