hier.7: Mention /var/run/shm.
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
b12defdc 2 * Copyright (c) 2003-2011 The DragonFly Project. All rights reserved.
60f60350 3 *
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4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
60f60350 6 *
8ad65e08
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7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
60f60350 10 *
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11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
8c10bfcf
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14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
60f60350 20 *
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21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
8ad65e08 32 * SUCH DAMAGE.
75cdbe6c
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33 */
34
35/*
36 * Each cpu in a system has its own self-contained light weight kernel
37 * thread scheduler, which means that generally speaking we only need
38 * to use a critical section to avoid problems. Foreign thread
39 * scheduling is queued via (async) IPIs.
8ad65e08
MD
40 */
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/kernel.h>
45#include <sys/proc.h>
46#include <sys/rtprio.h>
b37f18d6 47#include <sys/kinfo.h>
8ad65e08 48#include <sys/queue.h>
7d0bac62 49#include <sys/sysctl.h>
99df837e 50#include <sys/kthread.h>
f1d1c3fa 51#include <machine/cpu.h>
99df837e 52#include <sys/lock.h>
9d265729 53#include <sys/spinlock.h>
57aa743c 54#include <sys/ktr.h>
5b49787b 55#include <sys/indefinite.h>
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56
57#include <sys/thread2.h>
58#include <sys/spinlock2.h>
5b49787b 59#include <sys/indefinite2.h>
f1d1c3fa 60
8c72e3d5
AH
61#include <sys/dsched.h>
62
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63#include <vm/vm.h>
64#include <vm/vm_param.h>
65#include <vm/vm_kern.h>
66#include <vm/vm_object.h>
67#include <vm/vm_page.h>
68#include <vm/vm_map.h>
69#include <vm/vm_pager.h>
70#include <vm/vm_extern.h>
7d0bac62 71
99df837e 72#include <machine/stdarg.h>
96728c05 73#include <machine/smp.h>
3a06728e 74#include <machine/clock.h>
99df837e 75
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76#ifdef _KERNEL_VIRTUAL
77#include <pthread.h>
78#endif
79
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80#define LOOPMASK
81
d850923c
AE
82#if !defined(KTR_CTXSW)
83#define KTR_CTXSW KTR_ALL
84#endif
85KTR_INFO_MASTER(ctxsw);
5bf48697
AE
86KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td);
87KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td);
88KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm);
89KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td);
1541028a 90
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91static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
92
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93#ifdef INVARIANTS
94static int panic_on_cscount = 0;
95#endif
4b2467b7 96#ifdef DEBUG_LWKT_THREAD
e28c8ef4
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97static int64_t switch_count = 0;
98static int64_t preempt_hit = 0;
99static int64_t preempt_miss = 0;
100static int64_t preempt_weird = 0;
4b2467b7 101#endif
fb0f29c4 102static int lwkt_use_spin_port;
4b2467b7 103__read_mostly static struct objcache *thread_cache;
a46b4a23 104int cpu_mwait_spin = 0;
05220613 105
e381e77c 106static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 107static void lwkt_setcpu_remote(void *arg);
e381e77c 108
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109/*
110 * We can make all thread ports use the spin backend instead of the thread
111 * backend. This should only be set to debug the spin backend.
112 */
113TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
114
0f7a3396 115#ifdef INVARIANTS
0c52fa62
SG
116SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
117 "Panic if attempting to switch lwkt's while mastering cpusync");
0f7a3396 118#endif
4b2467b7 119#ifdef DEBUG_LWKT_THREAD
0c52fa62
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120SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
121 "Number of switched threads");
9733f757 122SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 123 "Successful preemption events");
9733f757 124SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
0c52fa62
SG
125 "Failed preemption events");
126SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
127 "Number of preempted threads.");
4b2467b7 128#endif
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129extern int lwkt_sched_debug;
130int lwkt_sched_debug = 0;
131SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
132 &lwkt_sched_debug, 0, "Scheduler debug");
4b2467b7 133__read_mostly static u_int lwkt_spin_loops = 10;
7fb451cb 134SYSCTL_UINT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
b12defdc 135 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
4b2467b7 136__read_mostly static int preempt_enable = 1;
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137SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
138 &preempt_enable, 0, "Enable preemption");
7b234d8c 139static int lwkt_cache_threads = 0;
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140SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
141 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 142
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143/*
144 * These helper procedures handle the runq, they can only be called from
145 * within a critical section.
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146 *
147 * WARNING! Prior to SMP being brought up it is possible to enqueue and
148 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
149 * instead of 'mycpu' when referencing the globaldata structure. Once
150 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 151 */
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152static __inline
153void
154_lwkt_dequeue(thread_t td)
155{
156 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 157 struct globaldata *gd = td->td_gd;
4b5f931b 158
f1d1c3fa 159 td->td_flags &= ~TDF_RUNQ;
f9235b6d 160 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
de4d4cb0 161 --gd->gd_tdrunqcount;
f9235b6d 162 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 163 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
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164 }
165}
166
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167/*
168 * Priority enqueue.
169 *
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170 * There are a limited number of lwkt threads runnable since user
171 * processes only schedule one at a time per cpu. However, there can
172 * be many user processes in kernel mode exiting from a tsleep() which
e3e6be1f 173 * become runnable.
d992c377 174 *
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175 * We scan the queue in both directions to help deal with degenerate
176 * situations when hundreds or thousands (or more) threads are runnable.
177 *
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178 * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and
179 * will ignore user priority. This is to ensure that user threads in
180 * kernel mode get cpu at some point regardless of what the user
181 * scheduler thinks.
f9235b6d 182 */
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183static __inline
184void
185_lwkt_enqueue(thread_t td)
186{
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187 thread_t xtd; /* forward scan */
188 thread_t rtd; /* reverse scan */
f9235b6d 189
7f5d7ed7 190 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 191 struct globaldata *gd = td->td_gd;
4b5f931b 192
f1d1c3fa 193 td->td_flags |= TDF_RUNQ;
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194 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
195 if (xtd == NULL) {
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196 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
197 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 198 } else {
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199 /*
200 * NOTE: td_upri - higher numbers more desireable, same sense
201 * as td_pri (typically reversed from lwp_upri).
202 *
203 * In the equal priority case we want the best selection
204 * at the beginning so the less desireable selections know
205 * that they have to setrunqueue/go-to-another-cpu, even
206 * though it means switching back to the 'best' selection.
207 * This also avoids degenerate situations when many threads
208 * are runnable or waking up at the same time.
209 *
210 * If upri matches exactly place at end/round-robin.
211 */
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212 rtd = TAILQ_LAST(&gd->gd_tdrunq, lwkt_queue);
213
d992c377 214 while (xtd &&
e6b81333 215 (xtd->td_pri > td->td_pri ||
d992c377 216 (xtd->td_pri == td->td_pri &&
e3e6be1f 217 xtd->td_upri >= td->td_upri))) {
85946b6c 218 xtd = TAILQ_NEXT(xtd, td_threadq);
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219
220 /*
221 * Doing a reverse scan at the same time is an optimization
222 * for the insert-closer-to-tail case that avoids having to
223 * scan the entire list. This situation can occur when
224 * thousands of threads are woken up at the same time.
225 */
226 if (rtd->td_pri > td->td_pri ||
227 (rtd->td_pri == td->td_pri &&
228 rtd->td_upri >= td->td_upri)) {
229 TAILQ_INSERT_AFTER(&gd->gd_tdrunq, rtd, td, td_threadq);
230 goto skip;
231 }
232 rtd = TAILQ_PREV(rtd, lwkt_queue, td_threadq);
d992c377 233 }
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234 if (xtd)
235 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
236 else
237 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 238 }
e6b81333 239skip:
de4d4cb0 240 ++gd->gd_tdrunqcount;
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241
242 /*
85946b6c 243 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 244 */
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245 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
246 need_lwkt_resched();
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MD
247 }
248}
8ad65e08 249
e28c8ef4 250static boolean_t
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NT
251_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
252{
253 struct thread *td = (struct thread *)obj;
254
255 td->td_kstack = NULL;
256 td->td_kstack_size = 0;
257 td->td_flags = TDF_ALLOCATED_THREAD;
4643740a 258 td->td_mpflags = 0;
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NT
259 return (1);
260}
261
262static void
263_lwkt_thread_dtor(void *obj, void *privdata)
264{
265 struct thread *td = (struct thread *)obj;
266
267 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
268 ("_lwkt_thread_dtor: not allocated from objcache"));
269 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
270 td->td_kstack_size > 0,
271 ("_lwkt_thread_dtor: corrupted stack"));
272 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
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273 td->td_kstack = NULL;
274 td->td_flags = 0;
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NT
275}
276
277/*
278 * Initialize the lwkt s/system.
765b1ae0 279 *
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280 * Nominally cache up to 32 thread + kstack structures. Cache more on
281 * systems with a lot of cpu cores.
40aaf5fc 282 */
ced589cb 283static void
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NT
284lwkt_init(void)
285{
765b1ae0 286 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
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287 if (lwkt_cache_threads == 0) {
288 lwkt_cache_threads = ncpus * 4;
289 if (lwkt_cache_threads < 32)
290 lwkt_cache_threads = 32;
291 }
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MD
292 thread_cache = objcache_create_mbacked(
293 M_THREAD, sizeof(struct thread),
2fce2579 294 0, lwkt_cache_threads,
765b1ae0 295 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
40aaf5fc 296}
ced589cb 297SYSINIT(lwkt_init, SI_BOOT2_LWKT_INIT, SI_ORDER_FIRST, lwkt_init, NULL);
40aaf5fc 298
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MD
299/*
300 * Schedule a thread to run. As the current thread we can always safely
301 * schedule ourselves, and a shortcut procedure is provided for that
302 * function.
303 *
304 * (non-blocking, self contained on a per cpu basis)
305 */
306void
307lwkt_schedule_self(thread_t td)
308{
cfaeae2a 309 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 310 crit_enter_quick(td);
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MD
311 KASSERT(td != &td->td_gd->gd_idlethread,
312 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
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313 KKASSERT(td->td_lwp == NULL ||
314 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
37af14fe 315 _lwkt_enqueue(td);
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MD
316 crit_exit_quick(td);
317}
318
319/*
320 * Deschedule a thread.
321 *
322 * (non-blocking, self contained on a per cpu basis)
323 */
324void
325lwkt_deschedule_self(thread_t td)
326{
327 crit_enter_quick(td);
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328 _lwkt_dequeue(td);
329 crit_exit_quick(td);
330}
331
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332/*
333 * LWKTs operate on a per-cpu basis
334 *
73e4f7b9 335 * WARNING! Called from early boot, 'mycpu' may not work yet.
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336 */
337void
338lwkt_gdinit(struct globaldata *gd)
339{
f9235b6d 340 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 341 TAILQ_INIT(&gd->gd_tdallq);
e8e93b5f 342 lockinit(&gd->gd_sysctllock, "sysctl", 0, LK_CANRECURSE);
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MD
343}
344
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345/*
346 * Create a new thread. The thread must be associated with a process context
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347 * or LWKT start address before it can be scheduled. If the target cpu is
348 * -1 the thread will be created on the current cpu.
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349 *
350 * If you intend to create a thread without a process context this function
351 * does everything except load the startup and switcher function.
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352 */
353thread_t
d3d32139 354lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 355{
d2d8515b 356 static int cpu_rotator;
c070746a 357 globaldata_t gd = mycpu;
99df837e 358 void *stack;
7d0bac62 359
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MD
360 /*
361 * If static thread storage is not supplied allocate a thread. Reuse
362 * a cached free thread if possible. gd_freetd is used to keep an exiting
363 * thread intact through the exit.
364 */
ef0fdad1 365 if (td == NULL) {
cf709dd2
MD
366 crit_enter_gd(gd);
367 if ((td = gd->gd_freetd) != NULL) {
368 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
369 TDF_RUNQ)) == 0);
c070746a 370 gd->gd_freetd = NULL;
cf709dd2 371 } else {
c070746a 372 td = objcache_get(thread_cache, M_WAITOK);
cf709dd2
MD
373 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
374 TDF_RUNQ)) == 0);
375 }
376 crit_exit_gd(gd);
40aaf5fc 377 KASSERT((td->td_flags &
2af9d75d
MD
378 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
379 TDF_ALLOCATED_THREAD,
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NT
380 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
381 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 382 }
c070746a
MD
383
384 /*
385 * Try to reuse cached stack.
386 */
f470d0c8
MD
387 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
388 if (flags & TDF_ALLOCATED_STACK) {
e4846942 389 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
390 stack = NULL;
391 }
392 }
393 if (stack == NULL) {
070a58b3
MD
394 if (cpu < 0)
395 stack = (void *)kmem_alloc_stack(&kernel_map, stksize, 0);
396 else
397 stack = (void *)kmem_alloc_stack(&kernel_map, stksize,
398 KM_CPU(cpu));
ef0fdad1 399 flags |= TDF_ALLOCATED_STACK;
99df837e 400 }
d2d8515b
MD
401 if (cpu < 0) {
402 cpu = ++cpu_rotator;
403 cpu_ccfence();
5dd85b08 404 cpu = (uint32_t)cpu % (uint32_t)ncpus;
d2d8515b
MD
405 }
406 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 407 return(td);
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408}
409
410/*
411 * Initialize a preexisting thread structure. This function is used by
412 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
413 *
f8c3996b
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414 * All threads start out in a critical section at a priority of
415 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
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416 * appropriate. This function may send an IPI message when the
417 * requested cpu is not the current cpu and consequently gd_tdallq may
418 * not be initialized synchronously from the point of view of the originating
419 * cpu.
420 *
421 * NOTE! we have to be careful in regards to creating threads for other cpus
422 * if SMP has not yet been activated.
7d0bac62 423 */
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424static void
425lwkt_init_thread_remote(void *arg)
426{
427 thread_t td = arg;
428
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429 /*
430 * Protected by critical section held by IPI dispatch
431 */
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432 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
433}
434
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435/*
436 * lwkt core thread structural initialization.
437 *
438 * NOTE: All threads are initialized as mpsafe threads.
439 */
7d0bac62 440void
f470d0c8
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441lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
442 struct globaldata *gd)
7d0bac62 443{
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444 globaldata_t mygd = mycpu;
445
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446 bzero(td, sizeof(struct thread));
447 td->td_kstack = stack;
f470d0c8 448 td->td_kstack_size = stksize;
d3d32139 449 td->td_flags = flags;
4643740a 450 td->td_mpflags = 0;
f256b6c0 451 td->td_type = TD_TYPE_GENERIC;
26a0694b 452 td->td_gd = gd;
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MD
453 td->td_pri = TDPRI_KERN_DAEMON;
454 td->td_critcount = 1;
54341a3b 455 td->td_toks_have = NULL;
3b998fa9 456 td->td_toks_stop = &td->td_toks_base;
c068fb59
SZ
457 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT)) {
458 lwkt_initport_spin(&td->td_msgport, td,
459 (flags & TDF_FIXEDCPU) ? TRUE : FALSE);
460 } else {
fb0f29c4 461 lwkt_initport_thread(&td->td_msgport, td);
c068fb59 462 }
99df837e 463 pmap_init_thread(td);
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464 /*
465 * Normally initializing a thread for a remote cpu requires sending an
466 * IPI. However, the idlethread is setup before the other cpus are
467 * activated so we have to treat it as a special case. XXX manipulation
468 * of gd_tdallq requires the BGL.
469 */
470 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 471 crit_enter_gd(mygd);
75cdbe6c 472 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 473 crit_exit_gd(mygd);
75cdbe6c 474 } else {
2db3b277 475 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 476 }
3573cf7b 477 dsched_enter_thread(td);
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MD
478}
479
480void
481lwkt_set_comm(thread_t td, const char *ctl, ...)
482{
e2565a42 483 __va_list va;
73e4f7b9 484
e2565a42 485 __va_start(va, ctl);
379210cb 486 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 487 __va_end(va);
5bf48697 488 KTR_LOG(ctxsw_newtd, td, td->td_comm);
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MD
489}
490
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491/*
492 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
493 * this does not prevent the thread from migrating to another cpu so the
494 * gd_tdallq state is not protected by this.
495 */
99df837e 496void
73e4f7b9 497lwkt_hold(thread_t td)
99df837e 498{
74c9628e 499 atomic_add_int(&td->td_refs, 1);
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MD
500}
501
502void
503lwkt_rele(thread_t td)
504{
505 KKASSERT(td->td_refs > 0);
74c9628e 506 atomic_add_int(&td->td_refs, -1);
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MD
507}
508
73e4f7b9
MD
509void
510lwkt_free_thread(thread_t td)
511{
74c9628e 512 KKASSERT(td->td_refs == 0);
c17a6852
MD
513 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
514 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
40aaf5fc
NT
515 if (td->td_flags & TDF_ALLOCATED_THREAD) {
516 objcache_put(thread_cache, td);
517 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
518 /* client-allocated struct with internally allocated stack */
519 KASSERT(td->td_kstack && td->td_kstack_size > 0,
520 ("lwkt_free_thread: corrupted stack"));
521 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
522 td->td_kstack = NULL;
523 td->td_kstack_size = 0;
99df837e 524 }
a86ce0cd 525
e7c0dbba 526 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
527}
528
529
8ad65e08
MD
530/*
531 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
532 * switch to the idlethread. Switching must occur within a critical
533 * section to avoid races with the scheduling queue.
534 *
535 * We always have full control over our cpu's run queue. Other cpus
536 * that wish to manipulate our queue must use the cpu_*msg() calls to
537 * talk to our cpu, so a critical section is all that is needed and
538 * the result is very, very fast thread switching.
539 *
96728c05
MD
540 * The LWKT scheduler uses a fixed priority model and round-robins at
541 * each priority level. User process scheduling is a totally
542 * different beast and LWKT priorities should not be confused with
543 * user process priorities.
f1d1c3fa 544 *
69d78e99
MD
545 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
546 * is not called by the current thread in the preemption case, only when
547 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
548 *
549 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
550 * migration and tsleep deschedule the current lwkt thread and call
551 * lwkt_switch(). In particular, the target cpu of the migration fully
552 * expects the thread to become non-runnable and can deadlock against
553 * cpusync operations if we run any IPIs prior to switching the thread out.
554 *
555 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 556 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
557 */
558void
559lwkt_switch(void)
560{
37af14fe
MD
561 globaldata_t gd = mycpu;
562 thread_t td = gd->gd_curthread;
8ad65e08 563 thread_t ntd;
c6a766f4 564 thread_t xtd;
5411d8f1 565 int upri;
3a06728e
MD
566#ifdef LOOPMASK
567 uint64_t tsc_base = rdtsc();
568#endif
8ad65e08 569
da0b0e8b 570 KKASSERT(gd->gd_processing_ipiq == 0);
121f93bc 571 KKASSERT(td->td_flags & TDF_RUNNING);
da0b0e8b 572
46a3f46d 573 /*
27e88a6e
MD
574 * Switching from within a 'fast' (non thread switched) interrupt or IPI
575 * is illegal. However, we may have to do it anyway if we hit a fatal
576 * kernel trap or we have paniced.
577 *
578 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 579 */
27e88a6e
MD
580 if (gd->gd_intr_nesting_level) {
581 int savegdnest;
582 int savegdtrap;
583
5fddbda2 584 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22 585 panic("lwkt_switch: Attempt to switch from a "
5a8df152 586 "fast interrupt, ipi, or hard code section, "
4a28fe22
MD
587 "td %p\n",
588 td);
27e88a6e
MD
589 } else {
590 savegdnest = gd->gd_intr_nesting_level;
591 savegdtrap = gd->gd_trap_nesting_level;
592 gd->gd_intr_nesting_level = 0;
593 gd->gd_trap_nesting_level = 0;
a7422615
MD
594 if ((td->td_flags & TDF_PANICWARN) == 0) {
595 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
596 kprintf("Warning: thread switch from interrupt, IPI, "
597 "or hard code section.\n"
a7422615 598 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 599 print_backtrace(-1);
a7422615 600 }
27e88a6e
MD
601 lwkt_switch();
602 gd->gd_intr_nesting_level = savegdnest;
603 gd->gd_trap_nesting_level = savegdtrap;
604 return;
605 }
96728c05 606 }
ef0fdad1 607
cb973d15 608 /*
85946b6c
MD
609 * Release our current user process designation if we are blocking
610 * or if a user reschedule was requested.
611 *
612 * NOTE: This function is NOT called if we are switching into or
613 * returning from a preemption.
614 *
615 * NOTE: Releasing our current user process designation may cause
616 * it to be assigned to another thread, which in turn will
617 * cause us to block in the usched acquire code when we attempt
618 * to return to userland.
619 *
620 * NOTE: On SMP systems this can be very nasty when heavy token
621 * contention is present so we want to be careful not to
622 * release the designation gratuitously.
cb973d15 623 */
85946b6c
MD
624 if (td->td_release &&
625 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 626 td->td_release(td);
85946b6c 627 }
cb973d15 628
85946b6c 629 /*
5411d8f1
MD
630 * Release all tokens. Once we do this we must remain in the critical
631 * section and cannot run IPIs or other interrupts until we switch away
632 * because they may implode if they try to get a token using our thread
633 * context.
85946b6c 634 */
37af14fe 635 crit_enter_gd(gd);
3b998fa9 636 if (TD_TOKS_HELD(td))
9d265729
MD
637 lwkt_relalltokens(td);
638
639 /*
b02926de
MD
640 * We had better not be holding any spin locks, but don't get into an
641 * endless panic loop.
9d265729 642 */
0846e4ce 643 KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL,
d666840a 644 ("lwkt_switch: still holding %d exclusive spinlocks!",
0846e4ce 645 gd->gd_spinlocks));
9d265729 646
0f7a3396
MD
647#ifdef INVARIANTS
648 if (td->td_cscount) {
6ea70f76 649 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
650 td);
651 if (panic_on_cscount)
652 panic("switching while mastering cpusync");
653 }
8a8d5d85 654#endif
f9235b6d
MD
655
656 /*
657 * If we had preempted another thread on this cpu, resume the preempted
658 * thread. This occurs transparently, whether the preempted thread
659 * was scheduled or not (it may have been preempted after descheduling
660 * itself).
661 *
662 * We have to setup the MP lock for the original thread after backing
663 * out the adjustment that was made to curthread when the original
664 * was preempted.
665 */
99df837e 666 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
667 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
668 ntd->td_flags |= TDF_PREEMPT_DONE;
7fb451cb 669 ntd->td_contended = 0; /* reset contended */
8ec60c3f
MD
670
671 /*
b9eb1c19
MD
672 * The interrupt may have woken a thread up, we need to properly
673 * set the reschedule flag if the originally interrupted thread is
674 * at a lower priority.
85946b6c 675 *
c6a766f4
MD
676 * NOTE: The interrupt may not have descheduled ntd.
677 *
678 * NOTE: We do not reschedule if there are no threads on the runq.
679 * (ntd could be the idlethread).
8ec60c3f 680 */
c6a766f4
MD
681 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
682 if (xtd && xtd != ntd)
8ec60c3f 683 need_lwkt_resched();
f9235b6d
MD
684 goto havethread_preempted;
685 }
686
b12defdc 687 /*
5411d8f1
MD
688 * Figure out switch target. If we cannot switch to our desired target
689 * look for a thread that we can switch to.
cfaeae2a 690 *
5411d8f1
MD
691 * NOTE! The limited spin loop and related parameters are extremely
692 * important for system performance, particularly for pipes and
693 * concurrent conflicting VM faults.
f9235b6d 694 */
5411d8f1
MD
695 clear_lwkt_resched();
696 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
697
698 if (ntd) {
699 do {
700 if (TD_TOKS_NOT_HELD(ntd) ||
701 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops)))
702 {
703 goto havethread;
704 }
7fb451cb 705 ++ntd->td_contended; /* overflow ok */
b1793cc6
MD
706 if (gd->gd_indefinite.type == 0)
707 indefinite_init(&gd->gd_indefinite, NULL, 0, 't');
3a06728e
MD
708#ifdef LOOPMASK
709 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
710 kprintf("lwkt_switch: excessive contended %d "
711 "thread %p\n", ntd->td_contended, ntd);
712 tsc_base = rdtsc();
713 }
714#endif
5411d8f1
MD
715 } while (ntd->td_contended < (lwkt_spin_loops >> 1));
716 upri = ntd->td_upri;
f9235b6d 717
f9235b6d 718 /*
5411d8f1
MD
719 * Bleh, the thread we wanted to switch to has a contended token.
720 * See if we can switch to another thread.
2a418930 721 *
5411d8f1 722 * We generally don't want to do this because it represents a
5042f74d
MD
723 * priority inversion, but contending tokens on the same cpu can
724 * cause real problems if we don't now that we have an exclusive
725 * priority mechanism over shared for tokens.
726 *
727 * The solution is to allow threads with pending tokens to compete
728 * for them (a lower priority thread will get less cpu once it
729 * returns from the kernel anyway). If a thread does not have
730 * any contending tokens, we go by td_pri and upri.
f9235b6d 731 */
b12defdc 732 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
5042f74d
MD
733 if (TD_TOKS_NOT_HELD(ntd) &&
734 ntd->td_pri < TDPRI_KERN_LPSCHED && upri > ntd->td_upri) {
735 continue;
736 }
737 if (upri < ntd->td_upri)
738 upri = ntd->td_upri;
b12defdc 739
5411d8f1
MD
740 /*
741 * Try this one.
742 */
743 if (TD_TOKS_NOT_HELD(ntd) ||
744 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops))) {
745 goto havethread;
746 }
7fb451cb 747 ++ntd->td_contended; /* overflow ok */
b12defdc 748 }
b12defdc
MD
749
750 /*
5411d8f1
MD
751 * Fall through, switch to idle thread to get us out of the current
752 * context. Since we were contended, prevent HLT by flagging a
753 * LWKT reschedule.
b12defdc 754 */
5411d8f1 755 need_lwkt_resched();
f1d1c3fa 756 }
8a8d5d85 757
5411d8f1
MD
758 /*
759 * We either contended on ntd or the runq is empty. We must switch
760 * through the idle thread to get out of the current context.
761 */
762 ntd = &gd->gd_idlethread;
763 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
764 ASSERT_NO_TOKENS_HELD(ntd);
765 cpu_time.cp_msg[0] = 0;
5411d8f1
MD
766 goto haveidle;
767
2a418930 768havethread:
b12defdc 769 /*
be71787b
MD
770 * Clear gd_idle_repeat when doing a normal switch to a non-idle
771 * thread.
f9235b6d 772 */
9ac1ee6e 773 ntd->td_wmesg = NULL;
7fb451cb 774 ntd->td_contended = 0; /* reset once scheduled */
b12defdc 775 ++gd->gd_cnt.v_swtch;
be71787b 776 gd->gd_idle_repeat = 0;
2a418930 777
5b49787b
MD
778 /*
779 * If we were busy waiting record final disposition
780 */
b1793cc6
MD
781 if (gd->gd_indefinite.type)
782 indefinite_done(&gd->gd_indefinite);
5b49787b 783
f9235b6d 784havethread_preempted:
f9235b6d
MD
785 /*
786 * If the new target does not need the MP lock and we are holding it,
787 * release the MP lock. If the new target requires the MP lock we have
788 * already acquired it for the target.
8a8d5d85 789 */
2a418930 790 ;
f9235b6d
MD
791haveidle:
792 KASSERT(ntd->td_critcount,
b5d16701
MD
793 ("priority problem in lwkt_switch %d %d",
794 td->td_critcount, ntd->td_critcount));
795
94f6d86e 796 if (td != ntd) {
cc9b6223
MD
797 /*
798 * Execute the actual thread switch operation. This function
799 * returns to the current thread and returns the previous thread
800 * (which may be different from the thread we switched to).
801 *
802 * We are responsible for marking ntd as TDF_RUNNING.
803 */
121f93bc 804 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
4b2467b7 805#ifdef DEBUG_LWKT_THREAD
94f6d86e 806 ++switch_count;
4b2467b7 807#endif
a1f0fb66 808 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
809 ntd->td_flags |= TDF_RUNNING;
810 lwkt_switch_return(td->td_switch(ntd));
811 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 812 }
b12defdc 813
b12defdc 814 /*
54341a3b 815 * catch-all. XXX is this strictly needed?
b12defdc
MD
816 */
817 splz_check();
54341a3b 818
37af14fe
MD
819 /* NOTE: current cpu may have changed after switch */
820 crit_exit_quick(td);
8ad65e08
MD
821}
822
cc9b6223
MD
823/*
824 * Called by assembly in the td_switch (thread restore path) for thread
825 * bootstrap cases which do not 'return' to lwkt_switch().
826 */
827void
828lwkt_switch_return(thread_t otd)
829{
cc9b6223 830 globaldata_t rgd;
3a06728e
MD
831#ifdef LOOPMASK
832 uint64_t tsc_base = rdtsc();
833#endif
834 int exiting;
835
836 exiting = otd->td_flags & TDF_EXITING;
837 cpu_ccfence();
cc9b6223
MD
838
839 /*
840 * Check if otd was migrating. Now that we are on ntd we can finish
841 * up the migration. This is a bit messy but it is the only place
842 * where td is known to be fully descheduled.
843 *
844 * We can only activate the migration if otd was migrating but not
845 * held on the cpu due to a preemption chain. We still have to
846 * clear TDF_RUNNING on the old thread either way.
847 *
848 * We are responsible for clearing the previously running thread's
849 * TDF_RUNNING.
850 */
851 if ((rgd = otd->td_migrate_gd) != NULL &&
852 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
853 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
854 (TDF_MIGRATING | TDF_RUNNING));
855 otd->td_migrate_gd = NULL;
856 otd->td_flags &= ~TDF_RUNNING;
857 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
858 } else {
859 otd->td_flags &= ~TDF_RUNNING;
860 }
2b07d9aa
MD
861
862 /*
863 * Final exit validations (see lwp_wait()). Note that otd becomes
864 * invalid the *instant* we set TDF_MP_EXITSIG.
3a06728e
MD
865 *
866 * Use the EXITING status loaded from before we clear TDF_RUNNING,
867 * because if it is not set otd becomes invalid the instant we clear
868 * TDF_RUNNING on it (otherwise, if the system is fast enough, we
869 * might 'steal' TDF_EXITING from another switch-return!).
2b07d9aa 870 */
3a06728e 871 while (exiting) {
2b07d9aa
MD
872 u_int mpflags;
873
874 mpflags = otd->td_mpflags;
875 cpu_ccfence();
876
877 if (mpflags & TDF_MP_EXITWAIT) {
878 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
879 mpflags | TDF_MP_EXITSIG)) {
880 wakeup(otd);
881 break;
882 }
883 } else {
884 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
885 mpflags | TDF_MP_EXITSIG)) {
886 wakeup(otd);
887 break;
888 }
889 }
3a06728e
MD
890
891#ifdef LOOPMASK
892 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
893 kprintf("lwkt_switch_return: excessive TDF_EXITING "
894 "thread %p\n", otd);
895 tsc_base = rdtsc();
896 }
897#endif
2b07d9aa 898 }
cc9b6223
MD
899}
900
b68b7282 901/*
96728c05 902 * Request that the target thread preempt the current thread. Preemption
203592a0
MD
903 * can only occur only:
904 *
905 * - If our critical section is the one that we were called with
906 * - The relative priority of the target thread is higher
907 * - The target is not excessively interrupt-nested via td_nest_count
908 * - The target thread holds no tokens.
909 * - The target thread is not already scheduled and belongs to the
910 * current cpu.
911 * - The current thread is not holding any spin-locks.
96728c05
MD
912 *
913 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
914 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 915 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
916 * to determine whether preemption is possible (aka usually just the crit
917 * priority of lwkt_schedule() itself).
b68b7282 918 *
54341a3b
MD
919 * Preemption is typically limited to interrupt threads.
920 *
921 * Operation works in a fairly straight-forward manner. The normal
922 * scheduling code is bypassed and we switch directly to the target
923 * thread. When the target thread attempts to block or switch away
924 * code at the base of lwkt_switch() will switch directly back to our
925 * thread. Our thread is able to retain whatever tokens it holds and
926 * if the target needs one of them the target will switch back to us
927 * and reschedule itself normally.
b68b7282
MD
928 */
929void
f9235b6d 930lwkt_preempt(thread_t ntd, int critcount)
b68b7282 931{
46a3f46d 932 struct globaldata *gd = mycpu;
cc9b6223 933 thread_t xtd;
0a3f9b47 934 thread_t td;
2d910aaf 935 int save_gd_intr_nesting_level;
b68b7282 936
26a0694b 937 /*
96728c05
MD
938 * The caller has put us in a critical section. We can only preempt
939 * if the caller of the caller was not in a critical section (basically
f9235b6d 940 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 941 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 942 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
943 *
944 * YYY The target thread must be in a critical section (else it must
945 * inherit our critical section? I dunno yet).
26a0694b 946 */
f9235b6d 947 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 948
b12defdc 949 td = gd->gd_curthread;
fbc024e4 950 if (preempt_enable == 0) {
4b2467b7 951#ifdef DEBUG_LWKT_THREAD
fbc024e4 952 ++preempt_miss;
4b2467b7 953#endif
fbc024e4
MD
954 return;
955 }
f9235b6d 956 if (ntd->td_pri <= td->td_pri) {
4b2467b7 957#ifdef DEBUG_LWKT_THREAD
57c254db 958 ++preempt_miss;
4b2467b7 959#endif
57c254db
MD
960 return;
961 }
f9235b6d 962 if (td->td_critcount > critcount) {
4b2467b7 963#ifdef DEBUG_LWKT_THREAD
96728c05 964 ++preempt_miss;
4b2467b7 965#endif
96728c05
MD
966 return;
967 }
203592a0 968 if (td->td_nest_count >= 2) {
4b2467b7 969#ifdef DEBUG_LWKT_THREAD
203592a0 970 ++preempt_miss;
4b2467b7 971#endif
203592a0
MD
972 return;
973 }
121f93bc 974 if (td->td_cscount) {
4b2467b7 975#ifdef DEBUG_LWKT_THREAD
121f93bc 976 ++preempt_miss;
4b2467b7 977#endif
121f93bc
MD
978 return;
979 }
46a3f46d 980 if (ntd->td_gd != gd) {
4b2467b7 981#ifdef DEBUG_LWKT_THREAD
96728c05 982 ++preempt_miss;
4b2467b7 983#endif
96728c05
MD
984 return;
985 }
ee89e80b 986
41a01a4d 987 /*
77912481
MD
988 * We don't have to check spinlocks here as they will also bump
989 * td_critcount.
d3d1cbc8
MD
990 *
991 * Do not try to preempt if the target thread is holding any tokens.
992 * We could try to acquire the tokens but this case is so rare there
993 * is no need to support it.
41a01a4d 994 */
0846e4ce 995 KKASSERT(gd->gd_spinlocks == 0);
77912481 996
3b998fa9 997 if (TD_TOKS_HELD(ntd)) {
4b2467b7 998#ifdef DEBUG_LWKT_THREAD
d3d1cbc8 999 ++preempt_miss;
4b2467b7 1000#endif
d3d1cbc8
MD
1001 return;
1002 }
26a0694b 1003 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
4b2467b7 1004#ifdef DEBUG_LWKT_THREAD
26a0694b 1005 ++preempt_weird;
4b2467b7 1006#endif
26a0694b
MD
1007 return;
1008 }
1009 if (ntd->td_preempted) {
4b2467b7 1010#ifdef DEBUG_LWKT_THREAD
4b5f931b 1011 ++preempt_hit;
4b2467b7 1012#endif
26a0694b 1013 return;
b68b7282 1014 }
da0b0e8b 1015 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1016
8ec60c3f
MD
1017 /*
1018 * Since we are able to preempt the current thread, there is no need to
1019 * call need_lwkt_resched().
2d910aaf
MD
1020 *
1021 * We must temporarily clear gd_intr_nesting_level around the switch
1022 * since switchouts from the target thread are allowed (they will just
1023 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1024 *
1025 * A preemption must switch back to the original thread, assert the
1026 * case.
8ec60c3f 1027 */
4b2467b7 1028#ifdef DEBUG_LWKT_THREAD
26a0694b 1029 ++preempt_hit;
4b2467b7 1030#endif
26a0694b
MD
1031 ntd->td_preempted = td;
1032 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1033 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1034 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1035 gd->gd_intr_nesting_level = 0;
121f93bc
MD
1036
1037 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
cc9b6223
MD
1038 ntd->td_flags |= TDF_RUNNING;
1039 xtd = td->td_switch(ntd);
1040 KKASSERT(xtd == ntd);
1041 lwkt_switch_return(xtd);
2d910aaf 1042 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1043
26a0694b
MD
1044 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1045 ntd->td_preempted = NULL;
1046 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1047}
1048
f1d1c3fa 1049/*
faaeffac 1050 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1051 * This will work inside a critical section but not inside a hard code
1052 * section.
ef0fdad1 1053 *
f1d1c3fa
MD
1054 * (self contained on a per cpu basis)
1055 */
1056void
faaeffac 1057splz_check(void)
f1d1c3fa 1058{
7966cb69
MD
1059 globaldata_t gd = mycpu;
1060 thread_t td = gd->gd_curthread;
ef0fdad1 1061
4a28fe22
MD
1062 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1063 gd->gd_intr_nesting_level == 0 &&
1064 td->td_nest_count < 2)
1065 {
f1d1c3fa 1066 splz();
4a28fe22
MD
1067 }
1068}
1069
1070/*
1071 * This version is integrated into crit_exit, reqflags has already
1072 * been tested but td_critcount has not.
1073 *
1074 * We only want to execute the splz() on the 1->0 transition of
1075 * critcount and not in a hard code section or if too deeply nested.
925040f2 1076 *
0846e4ce 1077 * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0.
4a28fe22
MD
1078 */
1079void
1080lwkt_maybe_splz(thread_t td)
1081{
1082 globaldata_t gd = td->td_gd;
1083
1084 if (td->td_critcount == 0 &&
1085 gd->gd_intr_nesting_level == 0 &&
1086 td->td_nest_count < 2)
1087 {
1088 splz();
1089 }
f1d1c3fa
MD
1090}
1091
e6546af9
MD
1092/*
1093 * Drivers which set up processing co-threads can call this function to
1094 * run the co-thread at a higher priority and to allow it to preempt
1095 * normal threads.
1096 */
1097void
1098lwkt_set_interrupt_support_thread(void)
1099{
1100 thread_t td = curthread;
1101
1102 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1103 td->td_flags |= TDF_INTTHREAD;
1104 td->td_preemptable = lwkt_preempt;
1105}
1106
1107
8ad65e08 1108/*
f9235b6d
MD
1109 * This function is used to negotiate a passive release of the current
1110 * process/lwp designation with the user scheduler, allowing the user
1111 * scheduler to schedule another user thread. The related kernel thread
1112 * (curthread) continues running in the released state.
8ad65e08
MD
1113 */
1114void
f9235b6d 1115lwkt_passive_release(struct thread *td)
8ad65e08 1116{
f9235b6d
MD
1117 struct lwp *lp = td->td_lwp;
1118
1119 td->td_release = NULL;
1120 lwkt_setpri_self(TDPRI_KERN_USER);
d992c377 1121
f9235b6d 1122 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1123}
1124
f9235b6d 1125
3824f392 1126/*
d2d8515b
MD
1127 * This implements a LWKT yield, allowing a kernel thread to yield to other
1128 * kernel threads at the same or higher priority. This function can be
1129 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1130 *
d2d8515b
MD
1131 * Most kernel threads run at the same priority in order to allow equal
1132 * sharing.
f9235b6d
MD
1133 *
1134 * (self contained on a per cpu basis)
3824f392
MD
1135 */
1136void
f9235b6d 1137lwkt_yield(void)
3824f392 1138{
f9235b6d
MD
1139 globaldata_t gd = mycpu;
1140 thread_t td = gd->gd_curthread;
3824f392 1141
fbe96076
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1142 /*
1143 * Should never be called with spinlocks held but there is a path
1144 * via ACPI where it might happen.
1145 */
1146 if (gd->gd_spinlocks)
1147 return;
1148
1149 /*
1150 * Safe to call splz if we are not too-heavily nested.
1151 */
f9235b6d
MD
1152 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1153 splz();
fbe96076
MD
1154
1155 /*
1156 * Caller allows switching
1157 */
85946b6c 1158 if (lwkt_resched_wanted()) {
dd8be70a
MD
1159 atomic_set_int(&td->td_mpflags, TDF_MP_DIDYIELD);
1160 lwkt_schedule_self(td);
f9235b6d 1161 lwkt_switch();
f9235b6d 1162 }
3824f392
MD
1163}
1164
40504122
MD
1165/*
1166 * The quick version processes pending interrupts and higher-priority
1167 * LWKT threads but will not round-robin same-priority LWKT threads.
de4d4cb0
MD
1168 *
1169 * When called while attempting to return to userland the only same-pri
1170 * threads are the ones which have already tried to become the current
1171 * user process.
40504122
MD
1172 */
1173void
1174lwkt_yield_quick(void)
1175{
1176 globaldata_t gd = mycpu;
1177 thread_t td = gd->gd_curthread;
1178
1179 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1180 splz();
1181 if (lwkt_resched_wanted()) {
9c99cb33 1182 crit_enter();
40504122
MD
1183 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1184 clear_lwkt_resched();
1185 } else {
dd8be70a 1186 atomic_set_int(&td->td_mpflags, TDF_MP_DIDYIELD);
40504122
MD
1187 lwkt_schedule_self(curthread);
1188 lwkt_switch();
1189 }
9c99cb33 1190 crit_exit();
40504122
MD
1191 }
1192}
1193
3824f392 1194/*
f9235b6d
MD
1195 * This yield is designed for kernel threads with a user context.
1196 *
1197 * The kernel acting on behalf of the user is potentially cpu-bound,
1198 * this function will efficiently allow other threads to run and also
1199 * switch to other processes by releasing.
3824f392
MD
1200 *
1201 * The lwkt_user_yield() function is designed to have very low overhead
1202 * if no yield is determined to be needed.
1203 */
1204void
1205lwkt_user_yield(void)
1206{
f9235b6d
MD
1207 globaldata_t gd = mycpu;
1208 thread_t td = gd->gd_curthread;
1209
fbe96076
MD
1210 /*
1211 * Should never be called with spinlocks held but there is a path
1212 * via ACPI where it might happen.
1213 */
1214 if (gd->gd_spinlocks)
1215 return;
1216
f9235b6d
MD
1217 /*
1218 * Always run any pending interrupts in case we are in a critical
1219 * section.
1220 */
1221 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1222 splz();
3824f392 1223
3824f392 1224 /*
f9235b6d
MD
1225 * Switch (which forces a release) if another kernel thread needs
1226 * the cpu, if userland wants us to resched, or if our kernel
1227 * quantum has run out.
3824f392 1228 */
f9235b6d 1229 if (lwkt_resched_wanted() ||
85946b6c 1230 user_resched_wanted())
f9235b6d 1231 {
3824f392 1232 lwkt_switch();
3824f392
MD
1233 }
1234
f9235b6d 1235#if 0
3824f392 1236 /*
f9235b6d
MD
1237 * Reacquire the current process if we are released.
1238 *
1239 * XXX not implemented atm. The kernel may be holding locks and such,
1240 * so we want the thread to continue to receive cpu.
3824f392 1241 */
f9235b6d
MD
1242 if (td->td_release == NULL && lp) {
1243 lp->lwp_proc->p_usched->acquire_curproc(lp);
1244 td->td_release = lwkt_passive_release;
1245 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1246 }
f9235b6d 1247#endif
b9eb1c19
MD
1248}
1249
8ad65e08 1250/*
f1d1c3fa
MD
1251 * Generic schedule. Possibly schedule threads belonging to other cpus and
1252 * deal with threads that might be blocked on a wait queue.
1253 *
0a3f9b47
MD
1254 * We have a little helper inline function which does additional work after
1255 * the thread has been enqueued, including dealing with preemption and
1256 * setting need_lwkt_resched() (which prevents the kernel from returning
1257 * to userland until it has processed higher priority threads).
6330a558
MD
1258 *
1259 * It is possible for this routine to be called after a failed _enqueue
1260 * (due to the target thread migrating, sleeping, or otherwise blocked).
1261 * We have to check that the thread is actually on the run queue!
8ad65e08 1262 */
0a3f9b47
MD
1263static __inline
1264void
85946b6c 1265_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1266{
6330a558 1267 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1268 if (ntd->td_preemptable) {
f9235b6d 1269 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1270 }
0a3f9b47
MD
1271 }
1272}
1273
361d01dd 1274static __inline
8ad65e08 1275void
85946b6c 1276_lwkt_schedule(thread_t td)
8ad65e08 1277{
37af14fe
MD
1278 globaldata_t mygd = mycpu;
1279
cf709dd2
MD
1280 KASSERT(td != &td->td_gd->gd_idlethread,
1281 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1282 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1283 crit_enter_gd(mygd);
4643740a
MD
1284 KKASSERT(td->td_lwp == NULL ||
1285 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1286
37af14fe 1287 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1288 _lwkt_enqueue(td);
1289 } else {
f1d1c3fa 1290 /*
7cd8d145
MD
1291 * If we own the thread, there is no race (since we are in a
1292 * critical section). If we do not own the thread there might
1293 * be a race but the target cpu will deal with it.
f1d1c3fa 1294 */
7cd8d145 1295 if (td->td_gd == mygd) {
9d265729 1296 _lwkt_enqueue(td);
85946b6c 1297 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1298 } else {
e381e77c 1299 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1300 }
8ad65e08 1301 }
37af14fe 1302 crit_exit_gd(mygd);
8ad65e08
MD
1303}
1304
361d01dd
MD
1305void
1306lwkt_schedule(thread_t td)
1307{
85946b6c 1308 _lwkt_schedule(td);
361d01dd
MD
1309}
1310
1311void
85946b6c 1312lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1313{
85946b6c 1314 _lwkt_schedule(td);
361d01dd
MD
1315}
1316
e381e77c
MD
1317/*
1318 * When scheduled remotely if frame != NULL the IPIQ is being
1319 * run via doreti or an interrupt then preemption can be allowed.
1320 *
1321 * To allow preemption we have to drop the critical section so only
1322 * one is present in _lwkt_schedule_post.
1323 */
1324static void
1325lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1326{
1327 thread_t td = curthread;
1328 thread_t ntd = arg;
1329
1330 if (frame && ntd->td_preemptable) {
1331 crit_exit_noyield(td);
85946b6c 1332 _lwkt_schedule(ntd);
e381e77c
MD
1333 crit_enter_quick(td);
1334 } else {
85946b6c 1335 _lwkt_schedule(ntd);
e381e77c
MD
1336 }
1337}
1338
d9eea1a5 1339/*
52eedfb5
MD
1340 * Thread migration using a 'Pull' method. The thread may or may not be
1341 * the current thread. It MUST be descheduled and in a stable state.
1342 * lwkt_giveaway() must be called on the cpu owning the thread.
1343 *
1344 * At any point after lwkt_giveaway() is called, the target cpu may
1345 * 'pull' the thread by calling lwkt_acquire().
1346 *
ae8e83e6
MD
1347 * We have to make sure the thread is not sitting on a per-cpu tsleep
1348 * queue or it will blow up when it moves to another cpu.
1349 *
52eedfb5 1350 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1351 */
52eedfb5
MD
1352void
1353lwkt_giveaway(thread_t td)
1354{
3b4192fb 1355 globaldata_t gd = mycpu;
52eedfb5 1356
3b4192fb
MD
1357 crit_enter_gd(gd);
1358 if (td->td_flags & TDF_TSLEEPQ)
1359 tsleep_remove(td);
1360 KKASSERT(td->td_gd == gd);
1361 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1362 td->td_flags |= TDF_MIGRATING;
1363 crit_exit_gd(gd);
52eedfb5
MD
1364}
1365
a2a5ad0d
MD
1366void
1367lwkt_acquire(thread_t td)
1368{
37af14fe
MD
1369 globaldata_t gd;
1370 globaldata_t mygd;
a2a5ad0d 1371
52eedfb5 1372 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1373 gd = td->td_gd;
37af14fe 1374 mygd = mycpu;
52eedfb5 1375 if (gd != mycpu) {
3a06728e
MD
1376#ifdef LOOPMASK
1377 uint64_t tsc_base = rdtsc();
1378#endif
35238fa5 1379 cpu_lfence();
52eedfb5 1380 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1381 crit_enter_gd(mygd);
cfaeae2a 1382 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23 1383 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
df910c23 1384 lwkt_process_ipiq();
52eedfb5 1385 cpu_lfence();
a86ce0cd
MD
1386#ifdef _KERNEL_VIRTUAL
1387 pthread_yield();
3a06728e
MD
1388#endif
1389#ifdef LOOPMASK
1390 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
1391 kprintf("lwkt_acquire: stuck td %p td->td_flags %08x\n",
1392 td, td->td_flags);
1393 tsc_base = rdtsc();
1394 }
a86ce0cd 1395#endif
df910c23 1396 }
cfaeae2a 1397 DEBUG_POP_INFO();
562273ea 1398 cpu_mfence();
37af14fe 1399 td->td_gd = mygd;
52eedfb5
MD
1400 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1401 td->td_flags &= ~TDF_MIGRATING;
1402 crit_exit_gd(mygd);
1403 } else {
1404 crit_enter_gd(mygd);
1405 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1406 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1407 crit_exit_gd(mygd);
a2a5ad0d
MD
1408 }
1409}
1410
f1d1c3fa
MD
1411/*
1412 * Generic deschedule. Descheduling threads other then your own should be
1413 * done only in carefully controlled circumstances. Descheduling is
1414 * asynchronous.
1415 *
1416 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1417 */
1418void
1419lwkt_deschedule(thread_t td)
1420{
f1d1c3fa
MD
1421 crit_enter();
1422 if (td == curthread) {
1423 _lwkt_dequeue(td);
1424 } else {
a72187e9 1425 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1426 _lwkt_dequeue(td);
1427 } else {
b8a98473 1428 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1429 }
1430 }
1431 crit_exit();
1432}
1433
4b5f931b
MD
1434/*
1435 * Set the target thread's priority. This routine does not automatically
1436 * switch to a higher priority thread, LWKT threads are not designed for
1437 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1438 */
1439void
1440lwkt_setpri(thread_t td, int pri)
1441{
f9235b6d
MD
1442 if (td->td_pri != pri) {
1443 KKASSERT(pri >= 0);
1444 crit_enter();
1445 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1446 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1447 _lwkt_dequeue(td);
1448 td->td_pri = pri;
1449 _lwkt_enqueue(td);
1450 } else {
1451 td->td_pri = pri;
1452 }
1453 crit_exit();
26a0694b 1454 }
26a0694b
MD
1455}
1456
03bd0a5e
MD
1457/*
1458 * Set the initial priority for a thread prior to it being scheduled for
1459 * the first time. The thread MUST NOT be scheduled before or during
1460 * this call. The thread may be assigned to a cpu other then the current
1461 * cpu.
1462 *
1463 * Typically used after a thread has been created with TDF_STOPPREQ,
1464 * and before the thread is initially scheduled.
1465 */
1466void
1467lwkt_setpri_initial(thread_t td, int pri)
1468{
1469 KKASSERT(pri >= 0);
1470 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1471 td->td_pri = pri;
03bd0a5e
MD
1472}
1473
26a0694b
MD
1474void
1475lwkt_setpri_self(int pri)
1476{
1477 thread_t td = curthread;
1478
4b5f931b
MD
1479 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1480 crit_enter();
1481 if (td->td_flags & TDF_RUNQ) {
1482 _lwkt_dequeue(td);
f9235b6d 1483 td->td_pri = pri;
4b5f931b
MD
1484 _lwkt_enqueue(td);
1485 } else {
f9235b6d 1486 td->td_pri = pri;
4b5f931b
MD
1487 }
1488 crit_exit();
1489}
1490
f9235b6d 1491/*
85946b6c 1492 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1493 */
1494void
85946b6c 1495lwkt_schedulerclock(thread_t td)
f9235b6d 1496{
85946b6c
MD
1497 globaldata_t gd = td->td_gd;
1498 thread_t xtd;
2a418930 1499
c6a766f4
MD
1500 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
1501 if (xtd == td) {
85946b6c
MD
1502 /*
1503 * If the current thread is at the head of the runq shift it to the
1504 * end of any equal-priority threads and request a LWKT reschedule
1505 * if it moved.
d992c377
MD
1506 *
1507 * Ignore upri in this situation. There will only be one user thread
1508 * in user mode, all others will be user threads running in kernel
1509 * mode and we have to make sure they get some cpu.
85946b6c
MD
1510 */
1511 xtd = TAILQ_NEXT(td, td_threadq);
1512 if (xtd && xtd->td_pri == td->td_pri) {
1513 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1514 while (xtd && xtd->td_pri == td->td_pri)
1515 xtd = TAILQ_NEXT(xtd, td_threadq);
1516 if (xtd)
1517 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1518 else
1519 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1520 need_lwkt_resched();
f9235b6d 1521 }
c6a766f4 1522 } else if (xtd) {
85946b6c
MD
1523 /*
1524 * If we scheduled a thread other than the one at the head of the
1525 * queue always request a reschedule every tick.
1526 */
1527 need_lwkt_resched();
f9235b6d 1528 }
c6a766f4 1529 /* else curthread probably the idle thread, no need to reschedule */
f9235b6d
MD
1530}
1531
5d21b981 1532/*
52eedfb5
MD
1533 * Migrate the current thread to the specified cpu.
1534 *
cc9b6223
MD
1535 * This is accomplished by descheduling ourselves from the current cpu
1536 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1537 * 'old' thread wants to migrate after it has been completely switched out
1538 * and will complete the migration.
1539 *
1540 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1541 *
1542 * We must be sure to release our current process designation (if a user
1543 * process) before clearing out any tsleepq we are on because the release
1544 * code may re-add us.
ae8e83e6
MD
1545 *
1546 * We must be sure to remove ourselves from the current cpu's tsleepq
1547 * before potentially moving to another queue. The thread can be on
1548 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1549 */
5d21b981
MD
1550
1551void
1552lwkt_setcpu_self(globaldata_t rgd)
1553{
5d21b981
MD
1554 thread_t td = curthread;
1555
1556 if (td->td_gd != rgd) {
1557 crit_enter_quick(td);
cc9b6223 1558
95858b91
MD
1559 if (td->td_release)
1560 td->td_release(td);
ae8e83e6 1561 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1562 tsleep_remove(td);
cc9b6223
MD
1563
1564 /*
1565 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1566 * trying to deschedule ourselves and switch away, then deschedule
1567 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1568 * call lwkt_switch() to complete the operation.
1569 */
5d21b981
MD
1570 td->td_flags |= TDF_MIGRATING;
1571 lwkt_deschedule_self(td);
52eedfb5 1572 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1573 td->td_migrate_gd = rgd;
5d21b981 1574 lwkt_switch();
cc9b6223
MD
1575
1576 /*
1577 * We are now on the target cpu
1578 */
1579 KKASSERT(rgd == mycpu);
52eedfb5 1580 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1581 crit_exit_quick(td);
1582 }
5d21b981
MD
1583}
1584
ecdefdda
MD
1585void
1586lwkt_migratecpu(int cpuid)
1587{
ecdefdda
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1588 globaldata_t rgd;
1589
1590 rgd = globaldata_find(cpuid);
1591 lwkt_setcpu_self(rgd);
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1592}
1593
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1594/*
1595 * Remote IPI for cpu migration (called while in a critical section so we
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1596 * do not have to enter another one).
1597 *
1598 * The thread (td) has already been completely descheduled from the
1599 * originating cpu and we can simply assert the case. The thread is
1600 * assigned to the new cpu and enqueued.
5d21b981 1601 *
cc9b6223 1602 * The thread will re-add itself to tdallq when it resumes execution.
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1603 */
1604static void
1605lwkt_setcpu_remote(void *arg)
1606{
1607 thread_t td = arg;
1608 globaldata_t gd = mycpu;
1609
cc9b6223 1610 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1611 td->td_gd = gd;
562273ea 1612 cpu_mfence();
5d21b981 1613 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1614 KKASSERT(td->td_migrate_gd == NULL);
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1615 KKASSERT(td->td_lwp == NULL ||
1616 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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1617 _lwkt_enqueue(td);
1618}
1619
553ea3c8 1620struct lwp *
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1621lwkt_preempted_proc(void)
1622{
73e4f7b9 1623 thread_t td = curthread;
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1624 while (td->td_preempted)
1625 td = td->td_preempted;
553ea3c8 1626 return(td->td_lwp);
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1627}
1628
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1629/*
1630 * Create a kernel process/thread/whatever. It shares it's address space
1631 * with proc0 - ie: kernel only.
1632 *
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1633 * If the cpu is not specified one will be selected. In the future
1634 * specifying a cpu of -1 will enable kernel thread migration between
1635 * cpus.
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1636 */
1637int
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1638lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1639 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1640{
73e4f7b9 1641 thread_t td;
e2565a42 1642 __va_list ap;
99df837e 1643
d3d32139 1644 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1645 tdflags);
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1646 if (tdp)
1647 *tdp = td;
709799ea 1648 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1649
1650 /*
1651 * Set up arg0 for 'ps' etc
1652 */
e2565a42 1653 __va_start(ap, fmt);
379210cb 1654 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1655 __va_end(ap);
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1656
1657 /*
1658 * Schedule the thread to run
1659 */
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1660 if (td->td_flags & TDF_NOSTART)
1661 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1662 else
4643740a 1663 lwkt_schedule(td);
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1664 return 0;
1665}
1666
1667/*
1668 * Destroy an LWKT thread. Warning! This function is not called when
1669 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1670 * uses a different reaping mechanism.
1671 */
1672void
1673lwkt_exit(void)
1674{
1675 thread_t td = curthread;
c070746a 1676 thread_t std;
8826f33a 1677 globaldata_t gd;
99df837e 1678
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1679 /*
1680 * Do any cleanup that might block here
1681 */
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1682 biosched_done(td);
1683 dsched_exit_thread(td);
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1684
1685 /*
1686 * Get us into a critical section to interlock gd_freetd and loop
1687 * until we can get it freed.
1688 *
1689 * We have to cache the current td in gd_freetd because objcache_put()ing
1690 * it would rip it out from under us while our thread is still active.
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1691 *
1692 * We are the current thread so of course our own TDF_RUNNING bit will
1693 * be set, so unlike the lwp reap code we don't wait for it to clear.
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1694 */
1695 gd = mycpu;
37af14fe 1696 crit_enter_quick(td);
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1697 for (;;) {
1698 if (td->td_refs) {
1699 tsleep(td, 0, "tdreap", 1);
1700 continue;
1701 }
1702 if ((std = gd->gd_freetd) != NULL) {
1703 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1704 gd->gd_freetd = NULL;
1705 objcache_put(thread_cache, std);
1706 continue;
1707 }
1708 break;
c070746a 1709 }
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1710
1711 /*
1712 * Remove thread resources from kernel lists and deschedule us for
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1713 * the last time. We cannot block after this point or we may end
1714 * up with a stale td on the tsleepq.
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1715 *
1716 * None of this may block, the critical section is the only thing
1717 * protecting tdallq and the only thing preventing new lwkt_hold()
1718 * thread refs now.
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1719 */
1720 if (td->td_flags & TDF_TSLEEPQ)
1721 tsleep_remove(td);
37af14fe 1722 lwkt_deschedule_self(td);
e56e4dea 1723 lwkt_remove_tdallq(td);
74c9628e 1724 KKASSERT(td->td_refs == 0);
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1725
1726 /*
1727 * Final cleanup
1728 */
1729 KKASSERT(gd->gd_freetd == NULL);
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1730 if (td->td_flags & TDF_ALLOCATED_THREAD)
1731 gd->gd_freetd = td;
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1732 cpu_thread_exit();
1733}
1734
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1735void
1736lwkt_remove_tdallq(thread_t td)
1737{
1738 KKASSERT(td->td_gd == mycpu);
1739 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1740}
1741
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1742/*
1743 * Code reduction and branch prediction improvements. Call/return
1744 * overhead on modern cpus often degenerates into 0 cycles due to
1745 * the cpu's branch prediction hardware and return pc cache. We
1746 * can take advantage of this by not inlining medium-complexity
1747 * functions and we can also reduce the branch prediction impact
1748 * by collapsing perfectly predictable branches into a single
1749 * procedure instead of duplicating it.
1750 *
1751 * Is any of this noticeable? Probably not, so I'll take the
1752 * smaller code size.
1753 */
1754void
b6468f56 1755crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1756{
b6468f56 1757 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1758}
1759
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1760void
1761crit_panic(void)
1762{
1763 thread_t td = curthread;
850634cc 1764 int lcrit = td->td_critcount;
2d93b37a 1765
850634cc 1766 td->td_critcount = 0;
a4d95680 1767 cpu_ccfence();
850634cc 1768 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1769 /* NOT REACHED */
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1770}
1771
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1772/*
1773 * Called from debugger/panic on cpus which have been stopped. We must still
b19f40a4 1774 * process the IPIQ while stopped.
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1775 *
1776 * If we are dumping also try to process any pending interrupts. This may
1777 * or may not work depending on the state of the cpu at the point it was
1778 * stopped.
1779 */
1780void
1781lwkt_smp_stopped(void)
1782{
1783 globaldata_t gd = mycpu;
1784
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1785 if (dumping) {
1786 lwkt_process_ipiq();
b19f40a4 1787 --gd->gd_intr_nesting_level;
bd8015ca 1788 splz();
b19f40a4 1789 ++gd->gd_intr_nesting_level;
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1790 } else {
1791 lwkt_process_ipiq();
1792 }
63cff036 1793 cpu_smp_stopped();
bd8015ca 1794}