subr_smp.c revision 134227
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: head/sys/kern/subr_smp.c 134227 2004-08-23 21:39:29Z peter $"); 37 38#include <sys/param.h> 39#include <sys/systm.h> 40#include <sys/kernel.h> 41#include <sys/ktr.h> 42#include <sys/proc.h> 43#include <sys/bus.h> 44#include <sys/lock.h> 45#include <sys/mutex.h> 46#include <sys/pcpu.h> 47#include <sys/smp.h> 48#include <sys/sysctl.h> 49 50#include <machine/smp.h> 51 52#ifdef SMP 53volatile cpumask_t stopped_cpus; 54volatile cpumask_t started_cpus; 55 56void (*cpustop_restartfunc)(void); 57#endif 58 59int mp_ncpus; 60/* export this for libkvm consumers. */ 61int mp_maxcpus = MAXCPU; 62 63struct cpu_top *smp_topology; 64volatile int smp_started; 65cpumask_t all_cpus; 66u_int mp_maxid; 67 68SYSCTL_NODE(_kern, OID_AUTO, smp, CTLFLAG_RD, NULL, "Kernel SMP"); 69 70SYSCTL_INT(_kern_smp, OID_AUTO, maxcpus, CTLFLAG_RD, &mp_maxcpus, 0, 71 "Max number of CPUs that the system was compiled for."); 72 73int smp_active = 0; /* are the APs allowed to run? */ 74SYSCTL_INT(_kern_smp, OID_AUTO, active, CTLFLAG_RW, &smp_active, 0, 75 "Number of Auxillary Processors (APs) that were successfully started"); 76 77int smp_disabled = 0; /* has smp been disabled? */ 78SYSCTL_INT(_kern_smp, OID_AUTO, disabled, CTLFLAG_RDTUN, &smp_disabled, 0, 79 "SMP has been disabled from the loader"); 80TUNABLE_INT("kern.smp.disabled", &smp_disabled); 81 82int smp_cpus = 1; /* how many cpu's running */ 83SYSCTL_INT(_kern_smp, OID_AUTO, cpus, CTLFLAG_RD, &smp_cpus, 0, 84 "Number of CPUs online"); 85 86#ifdef SMP 87/* Enable forwarding of a signal to a process running on a different CPU */ 88static int forward_signal_enabled = 1; 89SYSCTL_INT(_kern_smp, OID_AUTO, forward_signal_enabled, CTLFLAG_RW, 90 &forward_signal_enabled, 0, 91 "Forwarding of a signal to a process on a different CPU"); 92 93/* Enable forwarding of roundrobin to all other cpus */ 94static int forward_roundrobin_enabled = 1; 95SYSCTL_INT(_kern_smp, OID_AUTO, forward_roundrobin_enabled, CTLFLAG_RW, 96 &forward_roundrobin_enabled, 0, 97 "Forwarding of roundrobin to all other CPUs"); 98 99/* Variables needed for SMP rendezvous. */ 100static void (*smp_rv_setup_func)(void *arg); 101static void (*smp_rv_action_func)(void *arg); 102static void (*smp_rv_teardown_func)(void *arg); 103static void *smp_rv_func_arg; 104static volatile int smp_rv_waiters[2]; 105 106/* 107 * Shared mutex to restrict busywaits between smp_rendezvous() and 108 * smp(_targeted)_tlb_shootdown(). A deadlock occurs if both of these 109 * functions trigger at once and cause multiple CPUs to busywait with 110 * interrupts disabled. 111 */ 112struct mtx smp_rv_mtx; 113 114/* 115 * Let the MD SMP code initialize mp_maxid very early if it can. 116 */ 117static void 118mp_setmaxid(void *dummy) 119{ 120 cpu_mp_setmaxid(); 121} 122SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL) 123 124/* 125 * Call the MD SMP initialization code. 126 */ 127static void 128mp_start(void *dummy) 129{ 130 131 /* Probe for MP hardware. */ 132 if (smp_disabled != 0 || cpu_mp_probe() == 0) { 133 mp_ncpus = 1; 134 all_cpus = PCPU_GET(cpumask); 135 return; 136 } 137 138 mtx_init(&smp_rv_mtx, "smp rendezvous", NULL, MTX_SPIN); 139 cpu_mp_start(); 140 printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n", 141 mp_ncpus); 142 cpu_mp_announce(); 143} 144SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_SECOND, mp_start, NULL) 145 146void 147forward_signal(struct thread *td) 148{ 149 int id; 150 151 /* 152 * signotify() has already set TDF_ASTPENDING and TDF_NEEDSIGCHECK on 153 * this thread, so all we need to do is poke it if it is currently 154 * executing so that it executes ast(). 155 */ 156 mtx_assert(&sched_lock, MA_OWNED); 157 KASSERT(TD_IS_RUNNING(td), 158 ("forward_signal: thread is not TDS_RUNNING")); 159 160 CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc); 161 162 if (!smp_started || cold || panicstr) 163 return; 164 if (!forward_signal_enabled) 165 return; 166 167 /* No need to IPI ourself. */ 168 if (td == curthread) 169 return; 170 171 id = td->td_oncpu; 172 if (id == NOCPU) 173 return; 174 ipi_selected(1 << id, IPI_AST); 175} 176 177void 178forward_roundrobin(void) 179{ 180 struct pcpu *pc; 181 struct thread *td; 182 cpumask_t id, map, me; 183 184 mtx_assert(&sched_lock, MA_OWNED); 185 186 CTR0(KTR_SMP, "forward_roundrobin()"); 187 188 if (!smp_started || cold || panicstr) 189 return; 190 if (!forward_roundrobin_enabled) 191 return; 192 map = 0; 193 me = PCPU_GET(cpumask); 194 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { 195 td = pc->pc_curthread; 196 id = pc->pc_cpumask; 197 if (id != me && (id & stopped_cpus) == 0 && 198 td != pc->pc_idlethread) { 199 td->td_flags |= TDF_NEEDRESCHED; 200 map |= id; 201 } 202 } 203 ipi_selected(map, IPI_AST); 204} 205 206/* 207 * When called the executing CPU will send an IPI to all other CPUs 208 * requesting that they halt execution. 209 * 210 * Usually (but not necessarily) called with 'other_cpus' as its arg. 211 * 212 * - Signals all CPUs in map to stop. 213 * - Waits for each to stop. 214 * 215 * Returns: 216 * -1: error 217 * 0: NA 218 * 1: ok 219 * 220 * XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs 221 * from executing at same time. 222 */ 223int 224stop_cpus(cpumask_t map) 225{ 226 int i; 227 228 if (!smp_started) 229 return 0; 230 231 CTR1(KTR_SMP, "stop_cpus(%x)", map); 232 233 /* send the stop IPI to all CPUs in map */ 234 ipi_selected(map, IPI_STOP); 235 236 i = 0; 237 while ((atomic_load_acq_int(&stopped_cpus) & map) != map) { 238 /* spin */ 239 i++; 240#ifdef DIAGNOSTIC 241 if (i == 100000) { 242 printf("timeout stopping cpus\n"); 243 break; 244 } 245#endif 246 } 247 248 return 1; 249} 250 251 252/* 253 * Called by a CPU to restart stopped CPUs. 254 * 255 * Usually (but not necessarily) called with 'stopped_cpus' as its arg. 256 * 257 * - Signals all CPUs in map to restart. 258 * - Waits for each to restart. 259 * 260 * Returns: 261 * -1: error 262 * 0: NA 263 * 1: ok 264 */ 265int 266restart_cpus(cpumask_t map) 267{ 268 269 if (!smp_started) 270 return 0; 271 272 CTR1(KTR_SMP, "restart_cpus(%x)", map); 273 274 /* signal other cpus to restart */ 275 atomic_store_rel_int(&started_cpus, map); 276 277 /* wait for each to clear its bit */ 278 while ((atomic_load_acq_int(&stopped_cpus) & map) != 0) 279 ; /* nothing */ 280 281 return 1; 282} 283 284/* 285 * All-CPU rendezvous. CPUs are signalled, all execute the setup function 286 * (if specified), rendezvous, execute the action function (if specified), 287 * rendezvous again, execute the teardown function (if specified), and then 288 * resume. 289 * 290 * Note that the supplied external functions _must_ be reentrant and aware 291 * that they are running in parallel and in an unknown lock context. 292 */ 293void 294smp_rendezvous_action(void) 295{ 296 297 /* setup function */ 298 if (smp_rv_setup_func != NULL) 299 smp_rv_setup_func(smp_rv_func_arg); 300 /* spin on entry rendezvous */ 301 atomic_add_int(&smp_rv_waiters[0], 1); 302 while (atomic_load_acq_int(&smp_rv_waiters[0]) < mp_ncpus) 303 ; /* nothing */ 304 /* action function */ 305 if (smp_rv_action_func != NULL) 306 smp_rv_action_func(smp_rv_func_arg); 307 /* spin on exit rendezvous */ 308 atomic_add_int(&smp_rv_waiters[1], 1); 309 while (atomic_load_acq_int(&smp_rv_waiters[1]) < mp_ncpus) 310 ; /* nothing */ 311 /* teardown function */ 312 if (smp_rv_teardown_func != NULL) 313 smp_rv_teardown_func(smp_rv_func_arg); 314} 315 316void 317smp_rendezvous(void (* setup_func)(void *), 318 void (* action_func)(void *), 319 void (* teardown_func)(void *), 320 void *arg) 321{ 322 323 if (!smp_started) { 324 if (setup_func != NULL) 325 setup_func(arg); 326 if (action_func != NULL) 327 action_func(arg); 328 if (teardown_func != NULL) 329 teardown_func(arg); 330 return; 331 } 332 333 /* obtain rendezvous lock */ 334 mtx_lock_spin(&smp_rv_mtx); 335 336 /* set static function pointers */ 337 smp_rv_setup_func = setup_func; 338 smp_rv_action_func = action_func; 339 smp_rv_teardown_func = teardown_func; 340 smp_rv_func_arg = arg; 341 smp_rv_waiters[0] = 0; 342 smp_rv_waiters[1] = 0; 343 344 /* signal other processors, which will enter the IPI with interrupts off */ 345 ipi_all_but_self(IPI_RENDEZVOUS); 346 347 /* call executor function */ 348 smp_rendezvous_action(); 349 350 /* release lock */ 351 mtx_unlock_spin(&smp_rv_mtx); 352} 353#else /* !SMP */ 354 355/* 356 * Provide dummy SMP support for UP kernels. Modules that need to use SMP 357 * APIs will still work using this dummy support. 358 */ 359static void 360mp_setvariables_for_up(void *dummy) 361{ 362 mp_ncpus = 1; 363 mp_maxid = PCPU_GET(cpuid); 364 all_cpus = PCPU_GET(cpumask); 365 KASSERT(PCPU_GET(cpuid) == 0, ("UP must have a CPU ID of zero")); 366} 367SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST, 368 mp_setvariables_for_up, NULL) 369 370void 371smp_rendezvous(void (* setup_func)(void *), 372 void (* action_func)(void *), 373 void (* teardown_func)(void *), 374 void *arg) 375{ 376 377 if (setup_func != NULL) 378 setup_func(arg); 379 if (action_func != NULL) 380 action_func(arg); 381 if (teardown_func != NULL) 382 teardown_func(arg); 383} 384#endif /* SMP */ 385