The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_smp.c

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    1 /*-
    2  * Copyright (c) 2001, John Baldwin <jhb@FreeBSD.org>.
    3  * 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  * 3. 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 THE AUTHOR 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 THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * 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: releng/8.0/sys/kern/subr_smp.c 197576 2009-09-28 11:31:21Z kib $");
   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/cpu.h>
   51 #include <machine/smp.h>
   52 
   53 #include "opt_sched.h"
   54 
   55 #ifdef SMP
   56 volatile cpumask_t stopped_cpus;
   57 volatile cpumask_t started_cpus;
   58 cpumask_t idle_cpus_mask;
   59 cpumask_t hlt_cpus_mask;
   60 cpumask_t logical_cpus_mask;
   61 
   62 void (*cpustop_restartfunc)(void);
   63 #endif
   64 /* This is used in modules that need to work in both SMP and UP. */
   65 cpumask_t all_cpus;
   66 
   67 int mp_ncpus;
   68 /* export this for libkvm consumers. */
   69 int mp_maxcpus = MAXCPU;
   70 
   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, maxid, CTLFLAG_RD, &mp_maxid, 0,
   77     "Max CPU ID.");
   78 
   79 SYSCTL_INT(_kern_smp, OID_AUTO, maxcpus, CTLFLAG_RD, &mp_maxcpus, 0,
   80     "Max number of CPUs that the system was compiled for.");
   81 
   82 int smp_active = 0;     /* are the APs allowed to run? */
   83 SYSCTL_INT(_kern_smp, OID_AUTO, active, CTLFLAG_RW, &smp_active, 0,
   84     "Number of Auxillary Processors (APs) that were successfully started");
   85 
   86 int smp_disabled = 0;   /* has smp been disabled? */
   87 SYSCTL_INT(_kern_smp, OID_AUTO, disabled, CTLFLAG_RDTUN, &smp_disabled, 0,
   88     "SMP has been disabled from the loader");
   89 TUNABLE_INT("kern.smp.disabled", &smp_disabled);
   90 
   91 int smp_cpus = 1;       /* how many cpu's running */
   92 SYSCTL_INT(_kern_smp, OID_AUTO, cpus, CTLFLAG_RD, &smp_cpus, 0,
   93     "Number of CPUs online");
   94 
   95 int smp_topology = 0;   /* Which topology we're using. */
   96 SYSCTL_INT(_kern_smp, OID_AUTO, topology, CTLFLAG_RD, &smp_topology, 0,
   97     "Topology override setting; 0 is default provided by hardware.");
   98 TUNABLE_INT("kern.smp.topology", &smp_topology);
   99 
  100 #ifdef SMP
  101 /* Enable forwarding of a signal to a process running on a different CPU */
  102 static int forward_signal_enabled = 1;
  103 SYSCTL_INT(_kern_smp, OID_AUTO, forward_signal_enabled, CTLFLAG_RW,
  104            &forward_signal_enabled, 0,
  105            "Forwarding of a signal to a process on a different CPU");
  106 
  107 /* Variables needed for SMP rendezvous. */
  108 static volatile int smp_rv_ncpus;
  109 static void (*volatile smp_rv_setup_func)(void *arg);
  110 static void (*volatile smp_rv_action_func)(void *arg);
  111 static void (*volatile smp_rv_teardown_func)(void *arg);
  112 static void *volatile smp_rv_func_arg;
  113 static volatile int smp_rv_waiters[3];
  114 
  115 /* 
  116  * Shared mutex to restrict busywaits between smp_rendezvous() and
  117  * smp(_targeted)_tlb_shootdown().  A deadlock occurs if both of these
  118  * functions trigger at once and cause multiple CPUs to busywait with
  119  * interrupts disabled. 
  120  */
  121 struct mtx smp_ipi_mtx;
  122 
  123 /*
  124  * Let the MD SMP code initialize mp_maxid very early if it can.
  125  */
  126 static void
  127 mp_setmaxid(void *dummy)
  128 {
  129         cpu_mp_setmaxid();
  130 }
  131 SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL);
  132 
  133 /*
  134  * Call the MD SMP initialization code.
  135  */
  136 static void
  137 mp_start(void *dummy)
  138 {
  139 
  140         /* Probe for MP hardware. */
  141         if (smp_disabled != 0 || cpu_mp_probe() == 0) {
  142                 mp_ncpus = 1;
  143                 all_cpus = PCPU_GET(cpumask);
  144                 return;
  145         }
  146 
  147         mtx_init(&smp_ipi_mtx, "smp rendezvous", NULL, MTX_SPIN);
  148         cpu_mp_start();
  149         printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n",
  150             mp_ncpus);
  151         cpu_mp_announce();
  152 }
  153 SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_THIRD, mp_start, NULL);
  154 
  155 void
  156 forward_signal(struct thread *td)
  157 {
  158         int id;
  159 
  160         /*
  161          * signotify() has already set TDF_ASTPENDING and TDF_NEEDSIGCHECK on
  162          * this thread, so all we need to do is poke it if it is currently
  163          * executing so that it executes ast().
  164          */
  165         THREAD_LOCK_ASSERT(td, MA_OWNED);
  166         KASSERT(TD_IS_RUNNING(td),
  167             ("forward_signal: thread is not TDS_RUNNING"));
  168 
  169         CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc);
  170 
  171         if (!smp_started || cold || panicstr)
  172                 return;
  173         if (!forward_signal_enabled)
  174                 return;
  175 
  176         /* No need to IPI ourself. */
  177         if (td == curthread)
  178                 return;
  179 
  180         id = td->td_oncpu;
  181         if (id == NOCPU)
  182                 return;
  183         ipi_selected(1 << id, IPI_AST);
  184 }
  185 
  186 /*
  187  * When called the executing CPU will send an IPI to all other CPUs
  188  *  requesting that they halt execution.
  189  *
  190  * Usually (but not necessarily) called with 'other_cpus' as its arg.
  191  *
  192  *  - Signals all CPUs in map to stop.
  193  *  - Waits for each to stop.
  194  *
  195  * Returns:
  196  *  -1: error
  197  *   0: NA
  198  *   1: ok
  199  *
  200  * XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs
  201  *            from executing at same time.
  202  */
  203 static int
  204 generic_stop_cpus(cpumask_t map, u_int type)
  205 {
  206         int i;
  207 
  208         KASSERT(type == IPI_STOP || type == IPI_STOP_HARD,
  209             ("%s: invalid stop type", __func__));
  210 
  211         if (!smp_started)
  212                 return 0;
  213 
  214         CTR2(KTR_SMP, "stop_cpus(%x) with %u type", map, type);
  215 
  216         /* send the stop IPI to all CPUs in map */
  217         ipi_selected(map, type);
  218 
  219         i = 0;
  220         while ((stopped_cpus & map) != map) {
  221                 /* spin */
  222                 cpu_spinwait();
  223                 i++;
  224 #ifdef DIAGNOSTIC
  225                 if (i == 100000) {
  226                         printf("timeout stopping cpus\n");
  227                         break;
  228                 }
  229 #endif
  230         }
  231 
  232         return 1;
  233 }
  234 
  235 int
  236 stop_cpus(cpumask_t map)
  237 {
  238 
  239         return (generic_stop_cpus(map, IPI_STOP));
  240 }
  241 
  242 int
  243 stop_cpus_hard(cpumask_t map)
  244 {
  245 
  246         return (generic_stop_cpus(map, IPI_STOP_HARD));
  247 }
  248 
  249 #if defined(__amd64__)
  250 /*
  251  * When called the executing CPU will send an IPI to all other CPUs
  252  *  requesting that they halt execution.
  253  *
  254  * Usually (but not necessarily) called with 'other_cpus' as its arg.
  255  *
  256  *  - Signals all CPUs in map to suspend.
  257  *  - Waits for each to suspend.
  258  *
  259  * Returns:
  260  *  -1: error
  261  *   0: NA
  262  *   1: ok
  263  *
  264  * XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs
  265  *            from executing at same time.
  266  */
  267 int
  268 suspend_cpus(cpumask_t map)
  269 {
  270         int i;
  271 
  272         if (!smp_started)
  273                 return (0);
  274 
  275         CTR1(KTR_SMP, "suspend_cpus(%x)", map);
  276 
  277         /* send the suspend IPI to all CPUs in map */
  278         ipi_selected(map, IPI_SUSPEND);
  279 
  280         i = 0;
  281         while ((stopped_cpus & map) != map) {
  282                 /* spin */
  283                 cpu_spinwait();
  284                 i++;
  285 #ifdef DIAGNOSTIC
  286                 if (i == 100000) {
  287                         printf("timeout suspending cpus\n");
  288                         break;
  289                 }
  290 #endif
  291         }
  292 
  293         return (1);
  294 }
  295 #endif
  296 
  297 /*
  298  * Called by a CPU to restart stopped CPUs. 
  299  *
  300  * Usually (but not necessarily) called with 'stopped_cpus' as its arg.
  301  *
  302  *  - Signals all CPUs in map to restart.
  303  *  - Waits for each to restart.
  304  *
  305  * Returns:
  306  *  -1: error
  307  *   0: NA
  308  *   1: ok
  309  */
  310 int
  311 restart_cpus(cpumask_t map)
  312 {
  313 
  314         if (!smp_started)
  315                 return 0;
  316 
  317         CTR1(KTR_SMP, "restart_cpus(%x)", map);
  318 
  319         /* signal other cpus to restart */
  320         atomic_store_rel_int(&started_cpus, map);
  321 
  322         /* wait for each to clear its bit */
  323         while ((stopped_cpus & map) != 0)
  324                 cpu_spinwait();
  325 
  326         return 1;
  327 }
  328 
  329 /*
  330  * All-CPU rendezvous.  CPUs are signalled, all execute the setup function 
  331  * (if specified), rendezvous, execute the action function (if specified),
  332  * rendezvous again, execute the teardown function (if specified), and then
  333  * resume.
  334  *
  335  * Note that the supplied external functions _must_ be reentrant and aware
  336  * that they are running in parallel and in an unknown lock context.
  337  */
  338 void
  339 smp_rendezvous_action(void)
  340 {
  341         void* local_func_arg = smp_rv_func_arg;
  342         void (*local_setup_func)(void*)   = smp_rv_setup_func;
  343         void (*local_action_func)(void*)   = smp_rv_action_func;
  344         void (*local_teardown_func)(void*) = smp_rv_teardown_func;
  345 
  346         /* Ensure we have up-to-date values. */
  347         atomic_add_acq_int(&smp_rv_waiters[0], 1);
  348         while (smp_rv_waiters[0] < smp_rv_ncpus)
  349                 cpu_spinwait();
  350 
  351         /* setup function */
  352         if (local_setup_func != smp_no_rendevous_barrier) {
  353                 if (smp_rv_setup_func != NULL)
  354                         smp_rv_setup_func(smp_rv_func_arg);
  355 
  356                 /* spin on entry rendezvous */
  357                 atomic_add_int(&smp_rv_waiters[1], 1);
  358                 while (smp_rv_waiters[1] < smp_rv_ncpus)
  359                         cpu_spinwait();
  360         }
  361 
  362         /* action function */
  363         if (local_action_func != NULL)
  364                 local_action_func(local_func_arg);
  365 
  366         /* spin on exit rendezvous */
  367         atomic_add_int(&smp_rv_waiters[2], 1);
  368         if (local_teardown_func == smp_no_rendevous_barrier)
  369                 return;
  370         while (smp_rv_waiters[2] < smp_rv_ncpus)
  371                 cpu_spinwait();
  372 
  373         /* teardown function */
  374         if (local_teardown_func != NULL)
  375                 local_teardown_func(local_func_arg);
  376 }
  377 
  378 void
  379 smp_rendezvous_cpus(cpumask_t map,
  380         void (* setup_func)(void *), 
  381         void (* action_func)(void *),
  382         void (* teardown_func)(void *),
  383         void *arg)
  384 {
  385         int i, ncpus = 0;
  386 
  387         if (!smp_started) {
  388                 if (setup_func != NULL)
  389                         setup_func(arg);
  390                 if (action_func != NULL)
  391                         action_func(arg);
  392                 if (teardown_func != NULL)
  393                         teardown_func(arg);
  394                 return;
  395         }
  396 
  397         for (i = 0; i <= mp_maxid; i++)
  398                 if (((1 << i) & map) != 0 && !CPU_ABSENT(i))
  399                         ncpus++;
  400         if (ncpus == 0)
  401                 panic("ncpus is 0 with map=0x%x", map);
  402 
  403         /* obtain rendezvous lock */
  404         mtx_lock_spin(&smp_ipi_mtx);
  405 
  406         /* set static function pointers */
  407         smp_rv_ncpus = ncpus;
  408         smp_rv_setup_func = setup_func;
  409         smp_rv_action_func = action_func;
  410         smp_rv_teardown_func = teardown_func;
  411         smp_rv_func_arg = arg;
  412         smp_rv_waiters[1] = 0;
  413         smp_rv_waiters[2] = 0;
  414         atomic_store_rel_int(&smp_rv_waiters[0], 0);
  415 
  416         /* signal other processors, which will enter the IPI with interrupts off */
  417         ipi_selected(map & ~(1 << curcpu), IPI_RENDEZVOUS);
  418 
  419         /* Check if the current CPU is in the map */
  420         if ((map & (1 << curcpu)) != 0)
  421                 smp_rendezvous_action();
  422 
  423         if (teardown_func == smp_no_rendevous_barrier)
  424                 while (atomic_load_acq_int(&smp_rv_waiters[2]) < ncpus)
  425                         cpu_spinwait();
  426 
  427         /* release lock */
  428         mtx_unlock_spin(&smp_ipi_mtx);
  429 }
  430 
  431 void
  432 smp_rendezvous(void (* setup_func)(void *), 
  433                void (* action_func)(void *),
  434                void (* teardown_func)(void *),
  435                void *arg)
  436 {
  437         smp_rendezvous_cpus(all_cpus, setup_func, action_func, teardown_func, arg);
  438 }
  439 
  440 static struct cpu_group group[MAXCPU];
  441 
  442 struct cpu_group *
  443 smp_topo(void)
  444 {
  445         struct cpu_group *top;
  446 
  447         /*
  448          * Check for a fake topology request for debugging purposes.
  449          */
  450         switch (smp_topology) {
  451         case 1:
  452                 /* Dual core with no sharing.  */
  453                 top = smp_topo_1level(CG_SHARE_NONE, 2, 0);
  454                 break;
  455         case 2:
  456                 /* No topology, all cpus are equal. */
  457                 top = smp_topo_none();
  458                 break;
  459         case 3:
  460                 /* Dual core with shared L2.  */
  461                 top = smp_topo_1level(CG_SHARE_L2, 2, 0);
  462                 break;
  463         case 4:
  464                 /* quad core, shared l3 among each package, private l2.  */
  465                 top = smp_topo_1level(CG_SHARE_L3, 4, 0);
  466                 break;
  467         case 5:
  468                 /* quad core,  2 dualcore parts on each package share l2.  */
  469                 top = smp_topo_2level(CG_SHARE_NONE, 2, CG_SHARE_L2, 2, 0);
  470                 break;
  471         case 6:
  472                 /* Single-core 2xHTT */
  473                 top = smp_topo_1level(CG_SHARE_L1, 2, CG_FLAG_HTT);
  474                 break;
  475         case 7:
  476                 /* quad core with a shared l3, 8 threads sharing L2.  */
  477                 top = smp_topo_2level(CG_SHARE_L3, 4, CG_SHARE_L2, 8,
  478                     CG_FLAG_SMT);
  479                 break;
  480         default:
  481                 /* Default, ask the system what it wants. */
  482                 top = cpu_topo();
  483                 break;
  484         }
  485         /*
  486          * Verify the returned topology.
  487          */
  488         if (top->cg_count != mp_ncpus)
  489                 panic("Built bad topology at %p.  CPU count %d != %d",
  490                     top, top->cg_count, mp_ncpus);
  491         if (top->cg_mask != all_cpus)
  492                 panic("Built bad topology at %p.  CPU mask 0x%X != 0x%X",
  493                     top, top->cg_mask, all_cpus);
  494         return (top);
  495 }
  496 
  497 struct cpu_group *
  498 smp_topo_none(void)
  499 {
  500         struct cpu_group *top;
  501 
  502         top = &group[0];
  503         top->cg_parent = NULL;
  504         top->cg_child = NULL;
  505         top->cg_mask = (1 << mp_ncpus) - 1;
  506         top->cg_count = mp_ncpus;
  507         top->cg_children = 0;
  508         top->cg_level = CG_SHARE_NONE;
  509         top->cg_flags = 0;
  510         
  511         return (top);
  512 }
  513 
  514 static int
  515 smp_topo_addleaf(struct cpu_group *parent, struct cpu_group *child, int share,
  516     int count, int flags, int start)
  517 {
  518         cpumask_t mask;
  519         int i;
  520 
  521         for (mask = 0, i = 0; i < count; i++, start++)
  522                 mask |= (1 << start);
  523         child->cg_parent = parent;
  524         child->cg_child = NULL;
  525         child->cg_children = 0;
  526         child->cg_level = share;
  527         child->cg_count = count;
  528         child->cg_flags = flags;
  529         child->cg_mask = mask;
  530         parent->cg_children++;
  531         for (; parent != NULL; parent = parent->cg_parent) {
  532                 if ((parent->cg_mask & child->cg_mask) != 0)
  533                         panic("Duplicate children in %p.  mask 0x%X child 0x%X",
  534                             parent, parent->cg_mask, child->cg_mask);
  535                 parent->cg_mask |= child->cg_mask;
  536                 parent->cg_count += child->cg_count;
  537         }
  538 
  539         return (start);
  540 }
  541 
  542 struct cpu_group *
  543 smp_topo_1level(int share, int count, int flags)
  544 {
  545         struct cpu_group *child;
  546         struct cpu_group *top;
  547         int packages;
  548         int cpu;
  549         int i;
  550 
  551         cpu = 0;
  552         top = &group[0];
  553         packages = mp_ncpus / count;
  554         top->cg_child = child = &group[1];
  555         top->cg_level = CG_SHARE_NONE;
  556         for (i = 0; i < packages; i++, child++)
  557                 cpu = smp_topo_addleaf(top, child, share, count, flags, cpu);
  558         return (top);
  559 }
  560 
  561 struct cpu_group *
  562 smp_topo_2level(int l2share, int l2count, int l1share, int l1count,
  563     int l1flags)
  564 {
  565         struct cpu_group *top;
  566         struct cpu_group *l1g;
  567         struct cpu_group *l2g;
  568         int cpu;
  569         int i;
  570         int j;
  571 
  572         cpu = 0;
  573         top = &group[0];
  574         l2g = &group[1];
  575         top->cg_child = l2g;
  576         top->cg_level = CG_SHARE_NONE;
  577         top->cg_children = mp_ncpus / (l2count * l1count);
  578         l1g = l2g + top->cg_children;
  579         for (i = 0; i < top->cg_children; i++, l2g++) {
  580                 l2g->cg_parent = top;
  581                 l2g->cg_child = l1g;
  582                 l2g->cg_level = l2share;
  583                 for (j = 0; j < l2count; j++, l1g++)
  584                         cpu = smp_topo_addleaf(l2g, l1g, l1share, l1count,
  585                             l1flags, cpu);
  586         }
  587         return (top);
  588 }
  589 
  590 
  591 struct cpu_group *
  592 smp_topo_find(struct cpu_group *top, int cpu)
  593 {
  594         struct cpu_group *cg;
  595         cpumask_t mask;
  596         int children;
  597         int i;
  598 
  599         mask = (1 << cpu);
  600         cg = top;
  601         for (;;) {
  602                 if ((cg->cg_mask & mask) == 0)
  603                         return (NULL);
  604                 if (cg->cg_children == 0)
  605                         return (cg);
  606                 children = cg->cg_children;
  607                 for (i = 0, cg = cg->cg_child; i < children; cg++, i++)
  608                         if ((cg->cg_mask & mask) != 0)
  609                                 break;
  610         }
  611         return (NULL);
  612 }
  613 #else /* !SMP */
  614 
  615 void
  616 smp_rendezvous_cpus(cpumask_t map,
  617         void (*setup_func)(void *), 
  618         void (*action_func)(void *),
  619         void (*teardown_func)(void *),
  620         void *arg)
  621 {
  622         if (setup_func != NULL)
  623                 setup_func(arg);
  624         if (action_func != NULL)
  625                 action_func(arg);
  626         if (teardown_func != NULL)
  627                 teardown_func(arg);
  628 }
  629 
  630 void
  631 smp_rendezvous(void (*setup_func)(void *), 
  632                void (*action_func)(void *),
  633                void (*teardown_func)(void *),
  634                void *arg)
  635 {
  636 
  637         if (setup_func != NULL)
  638                 setup_func(arg);
  639         if (action_func != NULL)
  640                 action_func(arg);
  641         if (teardown_func != NULL)
  642                 teardown_func(arg);
  643 }
  644 
  645 /*
  646  * Provide dummy SMP support for UP kernels.  Modules that need to use SMP
  647  * APIs will still work using this dummy support.
  648  */
  649 static void
  650 mp_setvariables_for_up(void *dummy)
  651 {
  652         mp_ncpus = 1;
  653         mp_maxid = PCPU_GET(cpuid);
  654         all_cpus = PCPU_GET(cpumask);
  655         KASSERT(PCPU_GET(cpuid) == 0, ("UP must have a CPU ID of zero"));
  656 }
  657 SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST,
  658     mp_setvariables_for_up, NULL);
  659 #endif /* SMP */
  660 
  661 void
  662 smp_no_rendevous_barrier(void *dummy)
  663 {
  664 #ifdef SMP
  665         KASSERT((!smp_started),("smp_no_rendevous called and smp is started"));
  666 #endif
  667 }

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