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 <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 #include "opt_sched.h" 53 54 #ifdef SMP 55 volatile cpumask_t stopped_cpus; 56 volatile cpumask_t started_cpus; 57 cpumask_t idle_cpus_mask; 58 cpumask_t hlt_cpus_mask; 59 cpumask_t logical_cpus_mask; 60 61 void (*cpustop_restartfunc)(void); 62 #endif 63 /* This is used in modules that need to work in both SMP and UP. */ 64 cpumask_t all_cpus; 65 66 int mp_ncpus; 67 /* export this for libkvm consumers. */ 68 int mp_maxcpus = MAXCPU; 69 70 struct cpu_top *smp_topology; 71 volatile int smp_started; 72 u_int mp_maxid; 73 74 SYSCTL_NODE(_kern, OID_AUTO, smp, CTLFLAG_RD, NULL, "Kernel SMP"); 75 76 SYSCTL_INT(_kern_smp, OID_AUTO, maxcpus, CTLFLAG_RD, &mp_maxcpus, 0, 77 "Max number of CPUs that the system was compiled for."); 78 79 int smp_active = 0; /* are the APs allowed to run? */ 80 SYSCTL_INT(_kern_smp, OID_AUTO, active, CTLFLAG_RW, &smp_active, 0, 81 "Number of Auxillary Processors (APs) that were successfully started"); 82 83 int smp_disabled = 0; /* has smp been disabled? */ 84 SYSCTL_INT(_kern_smp, OID_AUTO, disabled, CTLFLAG_RDTUN, &smp_disabled, 0, 85 "SMP has been disabled from the loader"); 86 TUNABLE_INT("kern.smp.disabled", &smp_disabled); 87 88 int smp_cpus = 1; /* how many cpu's running */ 89 SYSCTL_INT(_kern_smp, OID_AUTO, cpus, CTLFLAG_RD, &smp_cpus, 0, 90 "Number of CPUs online"); 91 92 #ifdef SMP 93 /* Enable forwarding of a signal to a process running on a different CPU */ 94 static int forward_signal_enabled = 1; 95 SYSCTL_INT(_kern_smp, OID_AUTO, forward_signal_enabled, CTLFLAG_RW, 96 &forward_signal_enabled, 0, 97 "Forwarding of a signal to a process on a different CPU"); 98 99 /* Enable forwarding of roundrobin to all other cpus */ 100 static int forward_roundrobin_enabled = 1; 101 SYSCTL_INT(_kern_smp, OID_AUTO, forward_roundrobin_enabled, CTLFLAG_RW, 102 &forward_roundrobin_enabled, 0, 103 "Forwarding of roundrobin to all other CPUs"); 104 105 /* Variables needed for SMP rendezvous. */ 106 static void (*smp_rv_setup_func)(void *arg); 107 static void (*smp_rv_action_func)(void *arg); 108 static void (*smp_rv_teardown_func)(void *arg); 109 static void *smp_rv_func_arg; 110 static volatile int smp_rv_waiters[2]; 111 112 /* 113 * Shared mutex to restrict busywaits between smp_rendezvous() and 114 * smp(_targeted)_tlb_shootdown(). A deadlock occurs if both of these 115 * functions trigger at once and cause multiple CPUs to busywait with 116 * interrupts disabled. 117 */ 118 struct mtx smp_ipi_mtx; 119 120 /* 121 * Let the MD SMP code initialize mp_maxid very early if it can. 122 */ 123 static void 124 mp_setmaxid(void *dummy) 125 { 126 cpu_mp_setmaxid(); 127 } 128 SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL) 129 130 /* 131 * Call the MD SMP initialization code. 132 */ 133 static void 134 mp_start(void *dummy) 135 { 136 137 /* Probe for MP hardware. */ 138 if (smp_disabled != 0 || cpu_mp_probe() == 0) { 139 mp_ncpus = 1; 140 all_cpus = PCPU_GET(cpumask); 141 return; 142 } 143 144 mtx_init(&smp_ipi_mtx, "smp rendezvous", NULL, MTX_SPIN); 145 cpu_mp_start(); 146 printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n", 147 mp_ncpus); 148 cpu_mp_announce(); 149 } 150 SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_SECOND, mp_start, NULL) 151 152 void 153 forward_signal(struct thread *td) 154 { 155 int id; 156 157 /* 158 * signotify() has already set TDF_ASTPENDING and TDF_NEEDSIGCHECK on 159 * this thread, so all we need to do is poke it if it is currently 160 * executing so that it executes ast(). 161 */ 162 mtx_assert(&sched_lock, MA_OWNED); 163 KASSERT(TD_IS_RUNNING(td), 164 ("forward_signal: thread is not TDS_RUNNING")); 165 166 CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc); 167 168 if (!smp_started || cold || panicstr) 169 return; 170 if (!forward_signal_enabled) 171 return; 172 173 /* No need to IPI ourself. */ 174 if (td == curthread) 175 return; 176 177 id = td->td_oncpu; 178 if (id == NOCPU) 179 return; 180 ipi_selected(1 << id, IPI_AST); 181 } 182 183 void 184 forward_roundrobin(void) 185 { 186 struct pcpu *pc; 187 struct thread *td; 188 cpumask_t id, map, me; 189 190 mtx_assert(&sched_lock, MA_OWNED); 191 192 CTR0(KTR_SMP, "forward_roundrobin()"); 193 194 if (!smp_started || cold || panicstr) 195 return; 196 if (!forward_roundrobin_enabled) 197 return; 198 map = 0; 199 me = PCPU_GET(cpumask); 200 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { 201 td = pc->pc_curthread; 202 id = pc->pc_cpumask; 203 if (id != me && (id & stopped_cpus) == 0 && 204 td != pc->pc_idlethread) { 205 td->td_flags |= TDF_NEEDRESCHED; 206 map |= id; 207 } 208 } 209 ipi_selected(map, IPI_AST); 210 } 211 212 /* 213 * When called the executing CPU will send an IPI to all other CPUs 214 * requesting that they halt execution. 215 * 216 * Usually (but not necessarily) called with 'other_cpus' as its arg. 217 * 218 * - Signals all CPUs in map to stop. 219 * - Waits for each to stop. 220 * 221 * Returns: 222 * -1: error 223 * 0: NA 224 * 1: ok 225 * 226 * XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs 227 * from executing at same time. 228 */ 229 int 230 stop_cpus(cpumask_t map) 231 { 232 int i; 233 234 if (!smp_started) 235 return 0; 236 237 CTR1(KTR_SMP, "stop_cpus(%x)", map); 238 239 /* send the stop IPI to all CPUs in map */ 240 ipi_selected(map, IPI_STOP); 241 242 i = 0; 243 while ((atomic_load_acq_int(&stopped_cpus) & map) != map) { 244 /* spin */ 245 i++; 246 #ifdef DIAGNOSTIC 247 if (i == 100000) { 248 printf("timeout stopping cpus\n"); 249 break; 250 } 251 #endif 252 } 253 254 return 1; 255 } 256 257 258 /* 259 * Called by a CPU to restart stopped CPUs. 260 * 261 * Usually (but not necessarily) called with 'stopped_cpus' as its arg. 262 * 263 * - Signals all CPUs in map to restart. 264 * - Waits for each to restart. 265 * 266 * Returns: 267 * -1: error 268 * 0: NA 269 * 1: ok 270 */ 271 int 272 restart_cpus(cpumask_t map) 273 { 274 275 if (!smp_started) 276 return 0; 277 278 CTR1(KTR_SMP, "restart_cpus(%x)", map); 279 280 /* signal other cpus to restart */ 281 atomic_store_rel_int(&started_cpus, map); 282 283 /* wait for each to clear its bit */ 284 while ((atomic_load_acq_int(&stopped_cpus) & map) != 0) 285 ; /* nothing */ 286 287 return 1; 288 } 289 290 /* 291 * All-CPU rendezvous. CPUs are signalled, all execute the setup function 292 * (if specified), rendezvous, execute the action function (if specified), 293 * rendezvous again, execute the teardown function (if specified), and then 294 * resume. 295 * 296 * Note that the supplied external functions _must_ be reentrant and aware 297 * that they are running in parallel and in an unknown lock context. 298 */ 299 void 300 smp_rendezvous_action(void) 301 { 302 303 /* setup function */ 304 if (smp_rv_setup_func != NULL) 305 smp_rv_setup_func(smp_rv_func_arg); 306 /* spin on entry rendezvous */ 307 atomic_add_int(&smp_rv_waiters[0], 1); 308 while (atomic_load_acq_int(&smp_rv_waiters[0]) < mp_ncpus) 309 ; /* nothing */ 310 /* action function */ 311 if (smp_rv_action_func != NULL) 312 smp_rv_action_func(smp_rv_func_arg); 313 /* spin on exit rendezvous */ 314 atomic_add_int(&smp_rv_waiters[1], 1); 315 while (atomic_load_acq_int(&smp_rv_waiters[1]) < mp_ncpus) 316 ; /* nothing */ 317 /* teardown function */ 318 if (smp_rv_teardown_func != NULL) 319 smp_rv_teardown_func(smp_rv_func_arg); 320 } 321 322 void 323 smp_rendezvous(void (* setup_func)(void *), 324 void (* action_func)(void *), 325 void (* teardown_func)(void *), 326 void *arg) 327 { 328 329 if (!smp_started) { 330 if (setup_func != NULL) 331 setup_func(arg); 332 if (action_func != NULL) 333 action_func(arg); 334 if (teardown_func != NULL) 335 teardown_func(arg); 336 return; 337 } 338 339 /* obtain rendezvous lock */ 340 mtx_lock_spin(&smp_ipi_mtx); 341 342 /* set static function pointers */ 343 smp_rv_setup_func = setup_func; 344 smp_rv_action_func = action_func; 345 smp_rv_teardown_func = teardown_func; 346 smp_rv_func_arg = arg; 347 smp_rv_waiters[0] = 0; 348 smp_rv_waiters[1] = 0; 349 350 /* signal other processors, which will enter the IPI with interrupts off */ 351 ipi_all_but_self(IPI_RENDEZVOUS); 352 353 /* call executor function */ 354 smp_rendezvous_action(); 355 356 /* release lock */ 357 mtx_unlock_spin(&smp_ipi_mtx); 358 } 359 #else /* !SMP */ 360 361 /* 362 * Provide dummy SMP support for UP kernels. Modules that need to use SMP 363 * APIs will still work using this dummy support. 364 */ 365 static void 366 mp_setvariables_for_up(void *dummy) 367 { 368 mp_ncpus = 1; 369 mp_maxid = PCPU_GET(cpuid); 370 all_cpus = PCPU_GET(cpumask); 371 KASSERT(PCPU_GET(cpuid) == 0, ("UP must have a CPU ID of zero")); 372 } 373 SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST, 374 mp_setvariables_for_up, NULL) 375 376 void 377 smp_rendezvous(void (* setup_func)(void *), 378 void (* action_func)(void *), 379 void (* teardown_func)(void *), 380 void *arg) 381 { 382 383 if (setup_func != NULL) 384 setup_func(arg); 385 if (action_func != NULL) 386 action_func(arg); 387 if (teardown_func != NULL) 388 teardown_func(arg); 389 } 390 #endif /* SMP */ 391