3 * John Baldwin <jhb@FreeBSD.org>. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
31 * This module holds the global variables and machine independent functions
32 * used for the kernel SMP support.
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/kernel.h>
47 #include <sys/mutex.h>
50 #include <sys/sysctl.h>
52 #include <machine/smp.h>
54 #include "opt_sched.h"
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;
63 void (*cpustop_restartfunc)(void);
65 /* This is used in modules that need to work in both SMP and UP. */
69 /* export this for libkvm consumers. */
70 int mp_maxcpus = MAXCPU;
72 struct cpu_top *smp_topology;
73 volatile int smp_started;
76 SYSCTL_NODE(_kern, OID_AUTO, smp, CTLFLAG_RD, NULL, "Kernel SMP");
78 SYSCTL_INT(_kern_smp, OID_AUTO, maxcpus, CTLFLAG_RD, &mp_maxcpus, 0,
79 "Max number of CPUs that the system was compiled for.");
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");
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);
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");
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");
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");
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];
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.
120 struct mtx smp_ipi_mtx;
123 * Let the MD SMP code initialize mp_maxid very early if it can.
126 mp_setmaxid(void *dummy)
130 SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL)
133 * Call the MD SMP initialization code.
136 mp_start(void *dummy)
139 /* Probe for MP hardware. */
140 if (smp_disabled != 0 || cpu_mp_probe() == 0) {
142 all_cpus = PCPU_GET(cpumask);
146 mtx_init(&smp_ipi_mtx, "smp rendezvous", NULL, MTX_SPIN);
148 printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n",
152 SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_SECOND, mp_start, NULL)
155 forward_signal(struct thread *td)
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().
164 mtx_assert(&sched_lock, MA_OWNED);
165 KASSERT(TD_IS_RUNNING(td),
166 ("forward_signal: thread is not TDS_RUNNING"));
168 CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc);
170 if (!smp_started || cold || panicstr)
172 if (!forward_signal_enabled)
175 /* No need to IPI ourself. */
182 ipi_selected(1 << id, IPI_AST);
186 forward_roundrobin(void)
190 cpumask_t id, map, me;
192 mtx_assert(&sched_lock, MA_OWNED);
194 CTR0(KTR_SMP, "forward_roundrobin()");
196 if (!smp_started || cold || panicstr)
198 if (!forward_roundrobin_enabled)
201 me = PCPU_GET(cpumask);
202 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
203 td = pc->pc_curthread;
205 if (id != me && (id & stopped_cpus) == 0 &&
206 td != pc->pc_idlethread) {
207 td->td_flags |= TDF_NEEDRESCHED;
211 ipi_selected(map, IPI_AST);
215 * When called the executing CPU will send an IPI to all other CPUs
216 * requesting that they halt execution.
218 * Usually (but not necessarily) called with 'other_cpus' as its arg.
220 * - Signals all CPUs in map to stop.
221 * - Waits for each to stop.
228 * XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs
229 * from executing at same time.
232 stop_cpus(cpumask_t map)
239 CTR1(KTR_SMP, "stop_cpus(%x)", map);
241 /* send the stop IPI to all CPUs in map */
242 ipi_selected(map, IPI_STOP);
245 while ((atomic_load_acq_int(&stopped_cpus) & map) != map) {
250 printf("timeout stopping cpus\n");
261 stop_cpus_nmi(cpumask_t map)
268 CTR1(KTR_SMP, "stop_cpus(%x)", map);
270 /* send the stop IPI to all CPUs in map */
271 ipi_nmi_selected(map);
274 while ((atomic_load_acq_int(&stopped_cpus) & map) != map) {
279 printf("timeout stopping cpus\n");
287 #endif /* KDB_STOP_NMI */
290 * Called by a CPU to restart stopped CPUs.
292 * Usually (but not necessarily) called with 'stopped_cpus' as its arg.
294 * - Signals all CPUs in map to restart.
295 * - Waits for each to restart.
303 restart_cpus(cpumask_t map)
309 CTR1(KTR_SMP, "restart_cpus(%x)", map);
311 /* signal other cpus to restart */
312 atomic_store_rel_int(&started_cpus, map);
314 /* wait for each to clear its bit */
315 while ((atomic_load_acq_int(&stopped_cpus) & map) != 0)
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
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.
331 smp_rendezvous_action(void)
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)
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)
348 /* teardown function */
349 if (smp_rv_teardown_func != NULL)
350 smp_rv_teardown_func(smp_rv_func_arg);
354 smp_rendezvous(void (* setup_func)(void *),
355 void (* action_func)(void *),
356 void (* teardown_func)(void *),
361 if (setup_func != NULL)
363 if (action_func != NULL)
365 if (teardown_func != NULL)
370 /* obtain rendezvous lock */
371 mtx_lock_spin(&smp_ipi_mtx);
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;
381 /* signal other processors, which will enter the IPI with interrupts off */
382 ipi_all_but_self(IPI_RENDEZVOUS);
384 /* call executor function */
385 smp_rendezvous_action();
388 mtx_unlock_spin(&smp_ipi_mtx);
393 * Provide dummy SMP support for UP kernels. Modules that need to use SMP
394 * APIs will still work using this dummy support.
397 mp_setvariables_for_up(void *dummy)
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"));
404 SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST,
405 mp_setvariables_for_up, NULL)
408 smp_rendezvous(void (* setup_func)(void *),
409 void (* action_func)(void *),
410 void (* teardown_func)(void *),
414 if (setup_func != NULL)
416 if (action_func != NULL)
418 if (teardown_func != NULL)