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