test - Fix build warnings
[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
MD
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>
9d265729
MD
55
56#include <sys/thread2.h>
57#include <sys/spinlock2.h>
684a93c4 58#include <sys/mplock2.h>
f1d1c3fa 59
8c72e3d5
AH
60#include <sys/dsched.h>
61
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MD
62#include <vm/vm.h>
63#include <vm/vm_param.h>
64#include <vm/vm_kern.h>
65#include <vm/vm_object.h>
66#include <vm/vm_page.h>
67#include <vm/vm_map.h>
68#include <vm/vm_pager.h>
69#include <vm/vm_extern.h>
7d0bac62 70
99df837e 71#include <machine/stdarg.h>
96728c05 72#include <machine/smp.h>
99df837e 73
8cee56f4
MD
74#ifdef _KERNEL_VIRTUAL
75#include <pthread.h>
76#endif
77
d850923c
AE
78#if !defined(KTR_CTXSW)
79#define KTR_CTXSW KTR_ALL
80#endif
81KTR_INFO_MASTER(ctxsw);
5bf48697
AE
82KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td);
83KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td);
84KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm);
85KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td);
1541028a 86
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87static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
88
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89#ifdef INVARIANTS
90static int panic_on_cscount = 0;
91#endif
e28c8ef4
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92static int64_t switch_count = 0;
93static int64_t preempt_hit = 0;
94static int64_t preempt_miss = 0;
95static int64_t preempt_weird = 0;
fb0f29c4 96static int lwkt_use_spin_port;
40aaf5fc 97static struct objcache *thread_cache;
a46b4a23 98int cpu_mwait_spin = 0;
05220613 99
e381e77c 100static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 101static void lwkt_setcpu_remote(void *arg);
e381e77c 102
fb0f29c4
MD
103/*
104 * We can make all thread ports use the spin backend instead of the thread
105 * backend. This should only be set to debug the spin backend.
106 */
107TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
108
0f7a3396 109#ifdef INVARIANTS
0c52fa62
SG
110SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
111 "Panic if attempting to switch lwkt's while mastering cpusync");
0f7a3396 112#endif
0c52fa62
SG
113SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
114 "Number of switched threads");
9733f757 115SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 116 "Successful preemption events");
9733f757 117SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
0c52fa62
SG
118 "Failed preemption events");
119SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
120 "Number of preempted threads.");
b12defdc 121static int fairq_enable = 0;
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MD
122SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
123 &fairq_enable, 0, "Turn on fairq priority accumulators");
85946b6c 124static int fairq_bypass = -1;
b12defdc
MD
125SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
126 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
127extern int lwkt_sched_debug;
128int lwkt_sched_debug = 0;
129SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
130 &lwkt_sched_debug, 0, "Scheduler debug");
2a418930
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131static int lwkt_spin_loops = 10;
132SYSCTL_INT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
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133 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
134static int lwkt_spin_reseq = 0;
135SYSCTL_INT(_lwkt, OID_AUTO, spin_reseq, CTLFLAG_RW,
136 &lwkt_spin_reseq, 0, "Scheduler resequencer enable");
137static int lwkt_spin_monitor = 0;
138SYSCTL_INT(_lwkt, OID_AUTO, spin_monitor, CTLFLAG_RW,
139 &lwkt_spin_monitor, 0, "Scheduler uses monitor/mwait");
d5b2d319
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140static int lwkt_spin_fatal = 0; /* disabled */
141SYSCTL_INT(_lwkt, OID_AUTO, spin_fatal, CTLFLAG_RW,
142 &lwkt_spin_fatal, 0, "LWKT scheduler spin loops till fatal panic");
fbc024e4 143static int preempt_enable = 1;
2a418930
MD
144SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
145 &preempt_enable, 0, "Enable preemption");
7b234d8c 146static int lwkt_cache_threads = 0;
765b1ae0
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147SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
148 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 149
8cee56f4 150#ifndef _KERNEL_VIRTUAL
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MD
151static __cachealign int lwkt_cseq_rindex;
152static __cachealign int lwkt_cseq_windex;
8cee56f4 153#endif
05220613 154
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MD
155/*
156 * These helper procedures handle the runq, they can only be called from
157 * within a critical section.
75cdbe6c
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158 *
159 * WARNING! Prior to SMP being brought up it is possible to enqueue and
160 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
161 * instead of 'mycpu' when referencing the globaldata structure. Once
162 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 163 */
f1d1c3fa
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164static __inline
165void
166_lwkt_dequeue(thread_t td)
167{
168 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 169 struct globaldata *gd = td->td_gd;
4b5f931b 170
f1d1c3fa 171 td->td_flags &= ~TDF_RUNQ;
f9235b6d 172 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
de4d4cb0 173 --gd->gd_tdrunqcount;
f9235b6d 174 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 175 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
f1d1c3fa
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176 }
177}
178
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179/*
180 * Priority enqueue.
181 *
d992c377
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182 * There are a limited number of lwkt threads runnable since user
183 * processes only schedule one at a time per cpu. However, there can
184 * be many user processes in kernel mode exiting from a tsleep() which
e3e6be1f 185 * become runnable.
d992c377
MD
186 *
187 * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and
188 * will ignore user priority. This is to ensure that user threads in
189 * kernel mode get cpu at some point regardless of what the user
190 * scheduler thinks.
f9235b6d 191 */
f1d1c3fa
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192static __inline
193void
194_lwkt_enqueue(thread_t td)
195{
f9235b6d
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196 thread_t xtd;
197
7f5d7ed7 198 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 199 struct globaldata *gd = td->td_gd;
4b5f931b 200
f1d1c3fa 201 td->td_flags |= TDF_RUNQ;
f9235b6d
MD
202 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
203 if (xtd == NULL) {
85946b6c
MD
204 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
205 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 206 } else {
e3e6be1f
MD
207 /*
208 * NOTE: td_upri - higher numbers more desireable, same sense
209 * as td_pri (typically reversed from lwp_upri).
210 *
211 * In the equal priority case we want the best selection
212 * at the beginning so the less desireable selections know
213 * that they have to setrunqueue/go-to-another-cpu, even
214 * though it means switching back to the 'best' selection.
215 * This also avoids degenerate situations when many threads
216 * are runnable or waking up at the same time.
217 *
218 * If upri matches exactly place at end/round-robin.
219 */
d992c377 220 while (xtd &&
e3e6be1f 221 (xtd->td_pri >= td->td_pri ||
d992c377 222 (xtd->td_pri == td->td_pri &&
e3e6be1f 223 xtd->td_upri >= td->td_upri))) {
85946b6c 224 xtd = TAILQ_NEXT(xtd, td_threadq);
d992c377 225 }
85946b6c
MD
226 if (xtd)
227 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
228 else
229 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 230 }
de4d4cb0 231 ++gd->gd_tdrunqcount;
b12defdc
MD
232
233 /*
85946b6c 234 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 235 */
85946b6c
MD
236 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
237 need_lwkt_resched();
f1d1c3fa
MD
238 }
239}
8ad65e08 240
e28c8ef4 241static boolean_t
40aaf5fc
NT
242_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
243{
244 struct thread *td = (struct thread *)obj;
245
246 td->td_kstack = NULL;
247 td->td_kstack_size = 0;
248 td->td_flags = TDF_ALLOCATED_THREAD;
4643740a 249 td->td_mpflags = 0;
40aaf5fc
NT
250 return (1);
251}
252
253static void
254_lwkt_thread_dtor(void *obj, void *privdata)
255{
256 struct thread *td = (struct thread *)obj;
257
258 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
259 ("_lwkt_thread_dtor: not allocated from objcache"));
260 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
261 td->td_kstack_size > 0,
262 ("_lwkt_thread_dtor: corrupted stack"));
263 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
7b234d8c
MD
264 td->td_kstack = NULL;
265 td->td_flags = 0;
40aaf5fc
NT
266}
267
268/*
269 * Initialize the lwkt s/system.
765b1ae0 270 *
7b234d8c
MD
271 * Nominally cache up to 32 thread + kstack structures. Cache more on
272 * systems with a lot of cpu cores.
40aaf5fc 273 */
ced589cb 274static void
40aaf5fc
NT
275lwkt_init(void)
276{
765b1ae0 277 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
7b234d8c
MD
278 if (lwkt_cache_threads == 0) {
279 lwkt_cache_threads = ncpus * 4;
280 if (lwkt_cache_threads < 32)
281 lwkt_cache_threads = 32;
282 }
765b1ae0
MD
283 thread_cache = objcache_create_mbacked(
284 M_THREAD, sizeof(struct thread),
2fce2579 285 0, lwkt_cache_threads,
765b1ae0 286 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
40aaf5fc 287}
ced589cb 288SYSINIT(lwkt_init, SI_BOOT2_LWKT_INIT, SI_ORDER_FIRST, lwkt_init, NULL);
40aaf5fc 289
37af14fe
MD
290/*
291 * Schedule a thread to run. As the current thread we can always safely
292 * schedule ourselves, and a shortcut procedure is provided for that
293 * function.
294 *
295 * (non-blocking, self contained on a per cpu basis)
296 */
297void
298lwkt_schedule_self(thread_t td)
299{
cfaeae2a 300 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 301 crit_enter_quick(td);
f9235b6d
MD
302 KASSERT(td != &td->td_gd->gd_idlethread,
303 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
4643740a
MD
304 KKASSERT(td->td_lwp == NULL ||
305 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
37af14fe 306 _lwkt_enqueue(td);
37af14fe
MD
307 crit_exit_quick(td);
308}
309
310/*
311 * Deschedule a thread.
312 *
313 * (non-blocking, self contained on a per cpu basis)
314 */
315void
316lwkt_deschedule_self(thread_t td)
317{
318 crit_enter_quick(td);
37af14fe
MD
319 _lwkt_dequeue(td);
320 crit_exit_quick(td);
321}
322
8ad65e08
MD
323/*
324 * LWKTs operate on a per-cpu basis
325 *
73e4f7b9 326 * WARNING! Called from early boot, 'mycpu' may not work yet.
8ad65e08
MD
327 */
328void
329lwkt_gdinit(struct globaldata *gd)
330{
f9235b6d 331 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 332 TAILQ_INIT(&gd->gd_tdallq);
8ad65e08
MD
333}
334
7d0bac62
MD
335/*
336 * Create a new thread. The thread must be associated with a process context
75cdbe6c
MD
337 * or LWKT start address before it can be scheduled. If the target cpu is
338 * -1 the thread will be created on the current cpu.
0cfcada1
MD
339 *
340 * If you intend to create a thread without a process context this function
341 * does everything except load the startup and switcher function.
7d0bac62
MD
342 */
343thread_t
d3d32139 344lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 345{
d2d8515b 346 static int cpu_rotator;
c070746a 347 globaldata_t gd = mycpu;
99df837e 348 void *stack;
7d0bac62 349
c070746a
MD
350 /*
351 * If static thread storage is not supplied allocate a thread. Reuse
352 * a cached free thread if possible. gd_freetd is used to keep an exiting
353 * thread intact through the exit.
354 */
ef0fdad1 355 if (td == NULL) {
cf709dd2
MD
356 crit_enter_gd(gd);
357 if ((td = gd->gd_freetd) != NULL) {
358 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
359 TDF_RUNQ)) == 0);
c070746a 360 gd->gd_freetd = NULL;
cf709dd2 361 } else {
c070746a 362 td = objcache_get(thread_cache, M_WAITOK);
cf709dd2
MD
363 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
364 TDF_RUNQ)) == 0);
365 }
366 crit_exit_gd(gd);
40aaf5fc 367 KASSERT((td->td_flags &
2af9d75d
MD
368 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
369 TDF_ALLOCATED_THREAD,
40aaf5fc
NT
370 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
371 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 372 }
c070746a
MD
373
374 /*
375 * Try to reuse cached stack.
376 */
f470d0c8
MD
377 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
378 if (flags & TDF_ALLOCATED_STACK) {
e4846942 379 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
380 stack = NULL;
381 }
382 }
383 if (stack == NULL) {
e40cfbd7 384 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 385 flags |= TDF_ALLOCATED_STACK;
99df837e 386 }
d2d8515b
MD
387 if (cpu < 0) {
388 cpu = ++cpu_rotator;
389 cpu_ccfence();
390 cpu %= ncpus;
391 }
392 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 393 return(td);
7d0bac62
MD
394}
395
396/*
397 * Initialize a preexisting thread structure. This function is used by
398 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
399 *
f8c3996b
MD
400 * All threads start out in a critical section at a priority of
401 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
MD
402 * appropriate. This function may send an IPI message when the
403 * requested cpu is not the current cpu and consequently gd_tdallq may
404 * not be initialized synchronously from the point of view of the originating
405 * cpu.
406 *
407 * NOTE! we have to be careful in regards to creating threads for other cpus
408 * if SMP has not yet been activated.
7d0bac62 409 */
75cdbe6c
MD
410static void
411lwkt_init_thread_remote(void *arg)
412{
413 thread_t td = arg;
414
52eedfb5
MD
415 /*
416 * Protected by critical section held by IPI dispatch
417 */
75cdbe6c
MD
418 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
419}
420
fdce8919
MD
421/*
422 * lwkt core thread structural initialization.
423 *
424 * NOTE: All threads are initialized as mpsafe threads.
425 */
7d0bac62 426void
f470d0c8
MD
427lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
428 struct globaldata *gd)
7d0bac62 429{
37af14fe
MD
430 globaldata_t mygd = mycpu;
431
99df837e
MD
432 bzero(td, sizeof(struct thread));
433 td->td_kstack = stack;
f470d0c8 434 td->td_kstack_size = stksize;
d3d32139 435 td->td_flags = flags;
4643740a 436 td->td_mpflags = 0;
f256b6c0 437 td->td_type = TD_TYPE_GENERIC;
26a0694b 438 td->td_gd = gd;
f9235b6d
MD
439 td->td_pri = TDPRI_KERN_DAEMON;
440 td->td_critcount = 1;
54341a3b 441 td->td_toks_have = NULL;
3b998fa9 442 td->td_toks_stop = &td->td_toks_base;
c068fb59
SZ
443 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT)) {
444 lwkt_initport_spin(&td->td_msgport, td,
445 (flags & TDF_FIXEDCPU) ? TRUE : FALSE);
446 } else {
fb0f29c4 447 lwkt_initport_thread(&td->td_msgport, td);
c068fb59 448 }
99df837e 449 pmap_init_thread(td);
5d21b981
MD
450 /*
451 * Normally initializing a thread for a remote cpu requires sending an
452 * IPI. However, the idlethread is setup before the other cpus are
453 * activated so we have to treat it as a special case. XXX manipulation
454 * of gd_tdallq requires the BGL.
455 */
456 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 457 crit_enter_gd(mygd);
75cdbe6c 458 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 459 crit_exit_gd(mygd);
75cdbe6c 460 } else {
2db3b277 461 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 462 }
3573cf7b 463 dsched_enter_thread(td);
73e4f7b9
MD
464}
465
466void
467lwkt_set_comm(thread_t td, const char *ctl, ...)
468{
e2565a42 469 __va_list va;
73e4f7b9 470
e2565a42 471 __va_start(va, ctl);
379210cb 472 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 473 __va_end(va);
5bf48697 474 KTR_LOG(ctxsw_newtd, td, td->td_comm);
7d0bac62
MD
475}
476
eb2adbf5
MD
477/*
478 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
479 * this does not prevent the thread from migrating to another cpu so the
480 * gd_tdallq state is not protected by this.
481 */
99df837e 482void
73e4f7b9 483lwkt_hold(thread_t td)
99df837e 484{
74c9628e 485 atomic_add_int(&td->td_refs, 1);
73e4f7b9
MD
486}
487
488void
489lwkt_rele(thread_t td)
490{
491 KKASSERT(td->td_refs > 0);
74c9628e 492 atomic_add_int(&td->td_refs, -1);
73e4f7b9
MD
493}
494
73e4f7b9
MD
495void
496lwkt_free_thread(thread_t td)
497{
74c9628e 498 KKASSERT(td->td_refs == 0);
c17a6852
MD
499 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
500 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
40aaf5fc
NT
501 if (td->td_flags & TDF_ALLOCATED_THREAD) {
502 objcache_put(thread_cache, td);
503 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
504 /* client-allocated struct with internally allocated stack */
505 KASSERT(td->td_kstack && td->td_kstack_size > 0,
506 ("lwkt_free_thread: corrupted stack"));
507 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
508 td->td_kstack = NULL;
509 td->td_kstack_size = 0;
99df837e 510 }
a86ce0cd 511
e7c0dbba 512 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
513}
514
515
8ad65e08
MD
516/*
517 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
518 * switch to the idlethread. Switching must occur within a critical
519 * section to avoid races with the scheduling queue.
520 *
521 * We always have full control over our cpu's run queue. Other cpus
522 * that wish to manipulate our queue must use the cpu_*msg() calls to
523 * talk to our cpu, so a critical section is all that is needed and
524 * the result is very, very fast thread switching.
525 *
96728c05
MD
526 * The LWKT scheduler uses a fixed priority model and round-robins at
527 * each priority level. User process scheduling is a totally
528 * different beast and LWKT priorities should not be confused with
529 * user process priorities.
f1d1c3fa 530 *
69d78e99
MD
531 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
532 * is not called by the current thread in the preemption case, only when
533 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
534 *
535 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
536 * migration and tsleep deschedule the current lwkt thread and call
537 * lwkt_switch(). In particular, the target cpu of the migration fully
538 * expects the thread to become non-runnable and can deadlock against
539 * cpusync operations if we run any IPIs prior to switching the thread out.
540 *
541 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 542 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
543 */
544void
545lwkt_switch(void)
546{
37af14fe
MD
547 globaldata_t gd = mycpu;
548 thread_t td = gd->gd_curthread;
8ad65e08 549 thread_t ntd;
b12defdc 550 int spinning = 0;
8ad65e08 551
da0b0e8b 552 KKASSERT(gd->gd_processing_ipiq == 0);
121f93bc 553 KKASSERT(td->td_flags & TDF_RUNNING);
da0b0e8b 554
46a3f46d 555 /*
27e88a6e
MD
556 * Switching from within a 'fast' (non thread switched) interrupt or IPI
557 * is illegal. However, we may have to do it anyway if we hit a fatal
558 * kernel trap or we have paniced.
559 *
560 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 561 */
27e88a6e
MD
562 if (gd->gd_intr_nesting_level) {
563 int savegdnest;
564 int savegdtrap;
565
5fddbda2 566 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22 567 panic("lwkt_switch: Attempt to switch from a "
5a8df152 568 "fast interrupt, ipi, or hard code section, "
4a28fe22
MD
569 "td %p\n",
570 td);
27e88a6e
MD
571 } else {
572 savegdnest = gd->gd_intr_nesting_level;
573 savegdtrap = gd->gd_trap_nesting_level;
574 gd->gd_intr_nesting_level = 0;
575 gd->gd_trap_nesting_level = 0;
a7422615
MD
576 if ((td->td_flags & TDF_PANICWARN) == 0) {
577 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
578 kprintf("Warning: thread switch from interrupt, IPI, "
579 "or hard code section.\n"
a7422615 580 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 581 print_backtrace(-1);
a7422615 582 }
27e88a6e
MD
583 lwkt_switch();
584 gd->gd_intr_nesting_level = savegdnest;
585 gd->gd_trap_nesting_level = savegdtrap;
586 return;
587 }
96728c05 588 }
ef0fdad1 589
cb973d15 590 /*
85946b6c
MD
591 * Release our current user process designation if we are blocking
592 * or if a user reschedule was requested.
593 *
594 * NOTE: This function is NOT called if we are switching into or
595 * returning from a preemption.
596 *
597 * NOTE: Releasing our current user process designation may cause
598 * it to be assigned to another thread, which in turn will
599 * cause us to block in the usched acquire code when we attempt
600 * to return to userland.
601 *
602 * NOTE: On SMP systems this can be very nasty when heavy token
603 * contention is present so we want to be careful not to
604 * release the designation gratuitously.
cb973d15 605 */
85946b6c
MD
606 if (td->td_release &&
607 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 608 td->td_release(td);
85946b6c 609 }
cb973d15 610
85946b6c
MD
611 /*
612 * Release all tokens
613 */
37af14fe 614 crit_enter_gd(gd);
3b998fa9 615 if (TD_TOKS_HELD(td))
9d265729
MD
616 lwkt_relalltokens(td);
617
618 /*
b02926de
MD
619 * We had better not be holding any spin locks, but don't get into an
620 * endless panic loop.
9d265729 621 */
0846e4ce 622 KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL,
d666840a 623 ("lwkt_switch: still holding %d exclusive spinlocks!",
0846e4ce 624 gd->gd_spinlocks));
9d265729 625
8a8d5d85 626
0f7a3396
MD
627#ifdef INVARIANTS
628 if (td->td_cscount) {
6ea70f76 629 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
630 td);
631 if (panic_on_cscount)
632 panic("switching while mastering cpusync");
633 }
8a8d5d85 634#endif
f9235b6d
MD
635
636 /*
637 * If we had preempted another thread on this cpu, resume the preempted
638 * thread. This occurs transparently, whether the preempted thread
639 * was scheduled or not (it may have been preempted after descheduling
640 * itself).
641 *
642 * We have to setup the MP lock for the original thread after backing
643 * out the adjustment that was made to curthread when the original
644 * was preempted.
645 */
99df837e 646 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
647 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
648 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
649
650 /*
b9eb1c19
MD
651 * The interrupt may have woken a thread up, we need to properly
652 * set the reschedule flag if the originally interrupted thread is
653 * at a lower priority.
85946b6c
MD
654 *
655 * The interrupt may not have descheduled.
8ec60c3f 656 */
85946b6c 657 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 658 need_lwkt_resched();
f9235b6d
MD
659 goto havethread_preempted;
660 }
661
b12defdc 662 /*
f9235b6d 663 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
664 * schedule the target thread.
665 *
666 * Reminder: Again, we cannot afford to run any IPIs in this path if
667 * the current thread has been descheduled.
f9235b6d
MD
668 */
669 for (;;) {
844cfcd6
MD
670 int major_contention;
671
b12defdc 672 clear_lwkt_resched();
f9235b6d 673
4b5f931b 674 /*
2a418930 675 * Hotpath - pull the head of the run queue and attempt to schedule
85946b6c 676 * it.
41a01a4d 677 */
7c3dd309
NA
678 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
679
680 if (ntd == NULL) {
681 /*
682 * Runq is empty, switch to idle to allow it to halt.
683 */
684 ntd = &gd->gd_idlethread;
7c3dd309
NA
685 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
686 ASSERT_NO_TOKENS_HELD(ntd);
7c3dd309
NA
687 cpu_time.cp_msg[0] = 0;
688 cpu_time.cp_stallpc = 0;
689 goto haveidle;
f9235b6d 690 }
41a01a4d 691
8ec60c3f 692 /*
b12defdc 693 * Hotpath - schedule ntd.
6f207a2c
MD
694 *
695 * NOTE: For UP there is no mplock and lwkt_getalltokens()
696 * always succeeds.
8ec60c3f 697 */
b12defdc
MD
698 if (TD_TOKS_NOT_HELD(ntd) ||
699 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops)))
700 {
f9235b6d 701 goto havethread;
b12defdc 702 }
844cfcd6 703 major_contention = (ntd->td_contended > 10);
f9235b6d 704
f9235b6d 705 /*
2a418930
MD
706 * Coldpath (SMP only since tokens always succeed on UP)
707 *
708 * We had some contention on the thread we wanted to schedule.
709 * What we do now is try to find a thread that we can schedule
b12defdc 710 * in its stead.
2a418930 711 *
85946b6c
MD
712 * The coldpath scan does NOT rearrange threads in the run list.
713 * The lwkt_schedulerclock() will assert need_lwkt_resched() on
714 * the next tick whenever the current head is not the current thread.
f9235b6d 715 */
844cfcd6
MD
716 if (ntd->td_release)
717 ntd->td_release(ntd);
85946b6c 718 ++ntd->td_contended;
050032ec 719 ++gd->gd_cnt.v_lock_colls;
b12defdc 720
85946b6c 721 if (fairq_bypass > 0)
b12defdc
MD
722 goto skip;
723
b12defdc 724 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
e3e6be1f 725#ifndef NO_LWKT_SPLIT_USERPRI
85946b6c 726 /*
844cfcd6
MD
727 * Do not generally schedule threads returning to userland
728 * or the user thread scheduler helper thread when higher
729 * priority threads are present. The runq is sorted by
730 * priority so we can give up traversing it when we find
731 * the first low priority thread.
732 *
733 * As an exception, we allow scheduling of lower priority
734 * threads if all higher priority threads are seriously
735 * contended. This can prevent major contention from causing
736 * long multi-second pauses for other processes.
85946b6c 737 */
844cfcd6 738 if (!major_contention && ntd->td_pri < TDPRI_KERN_LPSCHED) {
85946b6c
MD
739 ntd = NULL;
740 break;
741 }
d992c377 742#endif
85946b6c
MD
743
744 /*
745 * Try this one.
746 */
b12defdc
MD
747 if (TD_TOKS_NOT_HELD(ntd) ||
748 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) {
749 goto havethread;
750 }
844cfcd6
MD
751 if (ntd->td_release)
752 ntd->td_release(ntd);
85946b6c 753 ++ntd->td_contended;
844cfcd6
MD
754 if (ntd->td_contended < 10)
755 major_contention = 0;
050032ec 756 ++gd->gd_cnt.v_lock_colls;
2a418930
MD
757 }
758
b12defdc 759skip:
2a418930
MD
760 /*
761 * We exhausted the run list, meaning that all runnable threads
b12defdc 762 * are contested.
2a418930
MD
763 */
764 cpu_pause();
8cee56f4
MD
765#ifdef _KERNEL_VIRTUAL
766 pthread_yield();
767#endif
2a418930 768 ntd = &gd->gd_idlethread;
2a418930
MD
769 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
770 ASSERT_NO_TOKENS_HELD(ntd);
771 /* contention case, do not clear contention mask */
2a418930
MD
772
773 /*
b12defdc
MD
774 * We are going to have to retry but if the current thread is not
775 * on the runq we instead switch through the idle thread to get away
776 * from the current thread. We have to flag for lwkt reschedule
777 * to prevent the idle thread from halting.
2a418930 778 *
b12defdc
MD
779 * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to
780 * instruct it to deal with the potential for deadlocks by
781 * ordering the tokens by address.
2a418930 782 */
b12defdc 783 if ((td->td_flags & TDF_RUNQ) == 0) {
85946b6c 784 need_lwkt_resched(); /* prevent hlt */
2a418930 785 goto haveidle;
4b5f931b 786 }
dbefba87 787#if defined(INVARIANTS) && defined(__x86_64__)
d5b2d319
MD
788 if ((read_rflags() & PSL_I) == 0) {
789 cpu_enable_intr();
790 panic("lwkt_switch() called with interrupts disabled");
791 }
792#endif
b12defdc
MD
793
794 /*
795 * Number iterations so far. After a certain point we switch to
796 * a sorted-address/monitor/mwait version of lwkt_getalltokens()
797 */
798 if (spinning < 0x7FFFFFFF)
799 ++spinning;
800
8cee56f4 801#ifndef _KERNEL_VIRTUAL
b12defdc
MD
802 /*
803 * lwkt_getalltokens() failed in sorted token mode, we can use
804 * monitor/mwait in this case.
805 */
806 if (spinning >= lwkt_spin_loops &&
807 (cpu_mi_feature & CPU_MI_MONITOR) &&
808 lwkt_spin_monitor)
809 {
810 cpu_mmw_pause_int(&gd->gd_reqflags,
811 (gd->gd_reqflags | RQF_SPINNING) &
a46b4a23 812 ~RQF_IDLECHECK_WK_MASK,
e5c52dd7 813 cpu_mwait_spin, 0);
b12defdc 814 }
8cee56f4 815#endif
b12defdc
MD
816
817 /*
818 * We already checked that td is still scheduled so this should be
819 * safe.
820 */
821 splz_check();
822
8cee56f4 823#ifndef _KERNEL_VIRTUAL
b12defdc
MD
824 /*
825 * This experimental resequencer is used as a fall-back to reduce
826 * hw cache line contention by placing each core's scheduler into a
827 * time-domain-multplexed slot.
828 *
829 * The resequencer is disabled by default. It's functionality has
830 * largely been superceeded by the token algorithm which limits races
831 * to a subset of cores.
832 *
833 * The resequencer algorithm tends to break down when more than
834 * 20 cores are contending. What appears to happen is that new
835 * tokens can be obtained out of address-sorted order by new cores
836 * while existing cores languish in long delays between retries and
837 * wind up being starved-out of the token acquisition.
838 */
839 if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) {
840 int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
841 int oseq;
842
843 while ((oseq = lwkt_cseq_rindex) != cseq) {
844 cpu_ccfence();
845#if 1
846 if (cpu_mi_feature & CPU_MI_MONITOR) {
e5c52dd7
SZ
847 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq,
848 cpu_mwait_spin, 0);
b12defdc
MD
849 } else {
850#endif
851 cpu_pause();
852 cpu_lfence();
853#if 1
854 }
8b402283 855#endif
0f0466c0 856 }
b12defdc
MD
857 DELAY(1);
858 atomic_add_int(&lwkt_cseq_rindex, 1);
2a418930 859 }
8cee56f4 860#endif
2a418930 861 /* highest level for(;;) loop */
f1d1c3fa 862 }
8a8d5d85 863
2a418930 864havethread:
b12defdc 865 /*
be71787b
MD
866 * Clear gd_idle_repeat when doing a normal switch to a non-idle
867 * thread.
f9235b6d 868 */
9ac1ee6e 869 ntd->td_wmesg = NULL;
844cfcd6 870 ntd->td_contended = 0;
b12defdc 871 ++gd->gd_cnt.v_swtch;
be71787b 872 gd->gd_idle_repeat = 0;
2a418930 873
f9235b6d 874havethread_preempted:
f9235b6d
MD
875 /*
876 * If the new target does not need the MP lock and we are holding it,
877 * release the MP lock. If the new target requires the MP lock we have
878 * already acquired it for the target.
8a8d5d85 879 */
2a418930 880 ;
f9235b6d
MD
881haveidle:
882 KASSERT(ntd->td_critcount,
b5d16701
MD
883 ("priority problem in lwkt_switch %d %d",
884 td->td_critcount, ntd->td_critcount));
885
94f6d86e 886 if (td != ntd) {
cc9b6223
MD
887 /*
888 * Execute the actual thread switch operation. This function
889 * returns to the current thread and returns the previous thread
890 * (which may be different from the thread we switched to).
891 *
892 * We are responsible for marking ntd as TDF_RUNNING.
893 */
121f93bc 894 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
94f6d86e 895 ++switch_count;
a1f0fb66 896 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
897 ntd->td_flags |= TDF_RUNNING;
898 lwkt_switch_return(td->td_switch(ntd));
899 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 900 }
b12defdc 901
b12defdc 902 /*
54341a3b 903 * catch-all. XXX is this strictly needed?
b12defdc
MD
904 */
905 splz_check();
54341a3b 906
37af14fe
MD
907 /* NOTE: current cpu may have changed after switch */
908 crit_exit_quick(td);
8ad65e08
MD
909}
910
cc9b6223
MD
911/*
912 * Called by assembly in the td_switch (thread restore path) for thread
913 * bootstrap cases which do not 'return' to lwkt_switch().
914 */
915void
916lwkt_switch_return(thread_t otd)
917{
cc9b6223
MD
918 globaldata_t rgd;
919
920 /*
921 * Check if otd was migrating. Now that we are on ntd we can finish
922 * up the migration. This is a bit messy but it is the only place
923 * where td is known to be fully descheduled.
924 *
925 * We can only activate the migration if otd was migrating but not
926 * held on the cpu due to a preemption chain. We still have to
927 * clear TDF_RUNNING on the old thread either way.
928 *
929 * We are responsible for clearing the previously running thread's
930 * TDF_RUNNING.
931 */
932 if ((rgd = otd->td_migrate_gd) != NULL &&
933 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
934 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
935 (TDF_MIGRATING | TDF_RUNNING));
936 otd->td_migrate_gd = NULL;
937 otd->td_flags &= ~TDF_RUNNING;
938 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
939 } else {
940 otd->td_flags &= ~TDF_RUNNING;
941 }
2b07d9aa
MD
942
943 /*
944 * Final exit validations (see lwp_wait()). Note that otd becomes
945 * invalid the *instant* we set TDF_MP_EXITSIG.
946 */
947 while (otd->td_flags & TDF_EXITING) {
948 u_int mpflags;
949
950 mpflags = otd->td_mpflags;
951 cpu_ccfence();
952
953 if (mpflags & TDF_MP_EXITWAIT) {
954 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
955 mpflags | TDF_MP_EXITSIG)) {
956 wakeup(otd);
957 break;
958 }
959 } else {
960 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
961 mpflags | TDF_MP_EXITSIG)) {
962 wakeup(otd);
963 break;
964 }
965 }
966 }
cc9b6223
MD
967}
968
b68b7282 969/*
96728c05 970 * Request that the target thread preempt the current thread. Preemption
54341a3b
MD
971 * can only occur if our only critical section is the one that we were called
972 * with, the relative priority of the target thread is higher, and the target
973 * thread holds no tokens. This also only works if we are not holding any
974 * spinlocks (obviously).
96728c05
MD
975 *
976 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
977 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 978 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
979 * to determine whether preemption is possible (aka usually just the crit
980 * priority of lwkt_schedule() itself).
b68b7282 981 *
54341a3b
MD
982 * Preemption is typically limited to interrupt threads.
983 *
984 * Operation works in a fairly straight-forward manner. The normal
985 * scheduling code is bypassed and we switch directly to the target
986 * thread. When the target thread attempts to block or switch away
987 * code at the base of lwkt_switch() will switch directly back to our
988 * thread. Our thread is able to retain whatever tokens it holds and
989 * if the target needs one of them the target will switch back to us
990 * and reschedule itself normally.
b68b7282
MD
991 */
992void
f9235b6d 993lwkt_preempt(thread_t ntd, int critcount)
b68b7282 994{
46a3f46d 995 struct globaldata *gd = mycpu;
cc9b6223 996 thread_t xtd;
0a3f9b47 997 thread_t td;
2d910aaf 998 int save_gd_intr_nesting_level;
b68b7282 999
26a0694b 1000 /*
96728c05
MD
1001 * The caller has put us in a critical section. We can only preempt
1002 * if the caller of the caller was not in a critical section (basically
f9235b6d 1003 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 1004 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 1005 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
1006 *
1007 * YYY The target thread must be in a critical section (else it must
1008 * inherit our critical section? I dunno yet).
26a0694b 1009 */
f9235b6d 1010 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 1011
b12defdc 1012 td = gd->gd_curthread;
fbc024e4
MD
1013 if (preempt_enable == 0) {
1014 ++preempt_miss;
1015 return;
1016 }
f9235b6d 1017 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
1018 ++preempt_miss;
1019 return;
1020 }
f9235b6d 1021 if (td->td_critcount > critcount) {
96728c05
MD
1022 ++preempt_miss;
1023 return;
1024 }
121f93bc
MD
1025 if (td->td_cscount) {
1026 ++preempt_miss;
1027 return;
1028 }
46a3f46d 1029 if (ntd->td_gd != gd) {
96728c05
MD
1030 ++preempt_miss;
1031 return;
1032 }
41a01a4d 1033 /*
77912481
MD
1034 * We don't have to check spinlocks here as they will also bump
1035 * td_critcount.
d3d1cbc8
MD
1036 *
1037 * Do not try to preempt if the target thread is holding any tokens.
1038 * We could try to acquire the tokens but this case is so rare there
1039 * is no need to support it.
41a01a4d 1040 */
0846e4ce 1041 KKASSERT(gd->gd_spinlocks == 0);
77912481 1042
3b998fa9 1043 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 1044 ++preempt_miss;
d3d1cbc8
MD
1045 return;
1046 }
26a0694b
MD
1047 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1048 ++preempt_weird;
1049 return;
1050 }
1051 if (ntd->td_preempted) {
4b5f931b 1052 ++preempt_hit;
26a0694b 1053 return;
b68b7282 1054 }
da0b0e8b 1055 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1056
8ec60c3f
MD
1057 /*
1058 * Since we are able to preempt the current thread, there is no need to
1059 * call need_lwkt_resched().
2d910aaf
MD
1060 *
1061 * We must temporarily clear gd_intr_nesting_level around the switch
1062 * since switchouts from the target thread are allowed (they will just
1063 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1064 *
1065 * A preemption must switch back to the original thread, assert the
1066 * case.
8ec60c3f 1067 */
26a0694b
MD
1068 ++preempt_hit;
1069 ntd->td_preempted = td;
1070 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1071 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1072 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1073 gd->gd_intr_nesting_level = 0;
121f93bc
MD
1074
1075 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
cc9b6223
MD
1076 ntd->td_flags |= TDF_RUNNING;
1077 xtd = td->td_switch(ntd);
1078 KKASSERT(xtd == ntd);
1079 lwkt_switch_return(xtd);
2d910aaf 1080 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1081
26a0694b
MD
1082 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1083 ntd->td_preempted = NULL;
1084 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1085}
1086
f1d1c3fa 1087/*
faaeffac 1088 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1089 * This will work inside a critical section but not inside a hard code
1090 * section.
ef0fdad1 1091 *
f1d1c3fa
MD
1092 * (self contained on a per cpu basis)
1093 */
1094void
faaeffac 1095splz_check(void)
f1d1c3fa 1096{
7966cb69
MD
1097 globaldata_t gd = mycpu;
1098 thread_t td = gd->gd_curthread;
ef0fdad1 1099
4a28fe22
MD
1100 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1101 gd->gd_intr_nesting_level == 0 &&
1102 td->td_nest_count < 2)
1103 {
f1d1c3fa 1104 splz();
4a28fe22
MD
1105 }
1106}
1107
1108/*
1109 * This version is integrated into crit_exit, reqflags has already
1110 * been tested but td_critcount has not.
1111 *
1112 * We only want to execute the splz() on the 1->0 transition of
1113 * critcount and not in a hard code section or if too deeply nested.
925040f2 1114 *
0846e4ce 1115 * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0.
4a28fe22
MD
1116 */
1117void
1118lwkt_maybe_splz(thread_t td)
1119{
1120 globaldata_t gd = td->td_gd;
1121
1122 if (td->td_critcount == 0 &&
1123 gd->gd_intr_nesting_level == 0 &&
1124 td->td_nest_count < 2)
1125 {
1126 splz();
1127 }
f1d1c3fa
MD
1128}
1129
e6546af9
MD
1130/*
1131 * Drivers which set up processing co-threads can call this function to
1132 * run the co-thread at a higher priority and to allow it to preempt
1133 * normal threads.
1134 */
1135void
1136lwkt_set_interrupt_support_thread(void)
1137{
1138 thread_t td = curthread;
1139
1140 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1141 td->td_flags |= TDF_INTTHREAD;
1142 td->td_preemptable = lwkt_preempt;
1143}
1144
1145
8ad65e08 1146/*
f9235b6d
MD
1147 * This function is used to negotiate a passive release of the current
1148 * process/lwp designation with the user scheduler, allowing the user
1149 * scheduler to schedule another user thread. The related kernel thread
1150 * (curthread) continues running in the released state.
8ad65e08
MD
1151 */
1152void
f9235b6d 1153lwkt_passive_release(struct thread *td)
8ad65e08 1154{
f9235b6d
MD
1155 struct lwp *lp = td->td_lwp;
1156
e3e6be1f 1157#ifndef NO_LWKT_SPLIT_USERPRI
f9235b6d
MD
1158 td->td_release = NULL;
1159 lwkt_setpri_self(TDPRI_KERN_USER);
d992c377
MD
1160#endif
1161
f9235b6d 1162 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1163}
1164
f9235b6d 1165
3824f392 1166/*
d2d8515b
MD
1167 * This implements a LWKT yield, allowing a kernel thread to yield to other
1168 * kernel threads at the same or higher priority. This function can be
1169 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1170 *
d2d8515b
MD
1171 * Most kernel threads run at the same priority in order to allow equal
1172 * sharing.
f9235b6d
MD
1173 *
1174 * (self contained on a per cpu basis)
3824f392
MD
1175 */
1176void
f9235b6d 1177lwkt_yield(void)
3824f392 1178{
f9235b6d
MD
1179 globaldata_t gd = mycpu;
1180 thread_t td = gd->gd_curthread;
3824f392 1181
f9235b6d
MD
1182 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1183 splz();
85946b6c 1184 if (lwkt_resched_wanted()) {
f9235b6d
MD
1185 lwkt_schedule_self(curthread);
1186 lwkt_switch();
f9235b6d 1187 }
3824f392
MD
1188}
1189
40504122
MD
1190/*
1191 * The quick version processes pending interrupts and higher-priority
1192 * LWKT threads but will not round-robin same-priority LWKT threads.
de4d4cb0
MD
1193 *
1194 * When called while attempting to return to userland the only same-pri
1195 * threads are the ones which have already tried to become the current
1196 * user process.
40504122
MD
1197 */
1198void
1199lwkt_yield_quick(void)
1200{
1201 globaldata_t gd = mycpu;
1202 thread_t td = gd->gd_curthread;
1203
1204 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1205 splz();
1206 if (lwkt_resched_wanted()) {
9c99cb33 1207 crit_enter();
40504122
MD
1208 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1209 clear_lwkt_resched();
1210 } else {
1211 lwkt_schedule_self(curthread);
1212 lwkt_switch();
1213 }
9c99cb33 1214 crit_exit();
40504122
MD
1215 }
1216}
1217
3824f392 1218/*
f9235b6d
MD
1219 * This yield is designed for kernel threads with a user context.
1220 *
1221 * The kernel acting on behalf of the user is potentially cpu-bound,
1222 * this function will efficiently allow other threads to run and also
1223 * switch to other processes by releasing.
3824f392
MD
1224 *
1225 * The lwkt_user_yield() function is designed to have very low overhead
1226 * if no yield is determined to be needed.
1227 */
1228void
1229lwkt_user_yield(void)
1230{
f9235b6d
MD
1231 globaldata_t gd = mycpu;
1232 thread_t td = gd->gd_curthread;
1233
1234 /*
1235 * Always run any pending interrupts in case we are in a critical
1236 * section.
1237 */
1238 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1239 splz();
3824f392 1240
3824f392 1241 /*
f9235b6d
MD
1242 * Switch (which forces a release) if another kernel thread needs
1243 * the cpu, if userland wants us to resched, or if our kernel
1244 * quantum has run out.
3824f392 1245 */
f9235b6d 1246 if (lwkt_resched_wanted() ||
85946b6c 1247 user_resched_wanted())
f9235b6d 1248 {
3824f392 1249 lwkt_switch();
3824f392
MD
1250 }
1251
f9235b6d 1252#if 0
3824f392 1253 /*
f9235b6d
MD
1254 * Reacquire the current process if we are released.
1255 *
1256 * XXX not implemented atm. The kernel may be holding locks and such,
1257 * so we want the thread to continue to receive cpu.
3824f392 1258 */
f9235b6d
MD
1259 if (td->td_release == NULL && lp) {
1260 lp->lwp_proc->p_usched->acquire_curproc(lp);
1261 td->td_release = lwkt_passive_release;
1262 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1263 }
f9235b6d 1264#endif
b9eb1c19
MD
1265}
1266
8ad65e08 1267/*
f1d1c3fa
MD
1268 * Generic schedule. Possibly schedule threads belonging to other cpus and
1269 * deal with threads that might be blocked on a wait queue.
1270 *
0a3f9b47
MD
1271 * We have a little helper inline function which does additional work after
1272 * the thread has been enqueued, including dealing with preemption and
1273 * setting need_lwkt_resched() (which prevents the kernel from returning
1274 * to userland until it has processed higher priority threads).
6330a558
MD
1275 *
1276 * It is possible for this routine to be called after a failed _enqueue
1277 * (due to the target thread migrating, sleeping, or otherwise blocked).
1278 * We have to check that the thread is actually on the run queue!
8ad65e08 1279 */
0a3f9b47
MD
1280static __inline
1281void
85946b6c 1282_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1283{
6330a558 1284 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1285 if (ntd->td_preemptable) {
f9235b6d 1286 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1287 }
0a3f9b47
MD
1288 }
1289}
1290
361d01dd 1291static __inline
8ad65e08 1292void
85946b6c 1293_lwkt_schedule(thread_t td)
8ad65e08 1294{
37af14fe
MD
1295 globaldata_t mygd = mycpu;
1296
cf709dd2
MD
1297 KASSERT(td != &td->td_gd->gd_idlethread,
1298 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1299 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1300 crit_enter_gd(mygd);
4643740a
MD
1301 KKASSERT(td->td_lwp == NULL ||
1302 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1303
37af14fe 1304 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1305 _lwkt_enqueue(td);
1306 } else {
f1d1c3fa 1307 /*
7cd8d145
MD
1308 * If we own the thread, there is no race (since we are in a
1309 * critical section). If we do not own the thread there might
1310 * be a race but the target cpu will deal with it.
f1d1c3fa 1311 */
7cd8d145 1312 if (td->td_gd == mygd) {
9d265729 1313 _lwkt_enqueue(td);
85946b6c 1314 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1315 } else {
e381e77c 1316 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1317 }
8ad65e08 1318 }
37af14fe 1319 crit_exit_gd(mygd);
8ad65e08
MD
1320}
1321
361d01dd
MD
1322void
1323lwkt_schedule(thread_t td)
1324{
85946b6c 1325 _lwkt_schedule(td);
361d01dd
MD
1326}
1327
1328void
85946b6c 1329lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1330{
85946b6c 1331 _lwkt_schedule(td);
361d01dd
MD
1332}
1333
e381e77c
MD
1334/*
1335 * When scheduled remotely if frame != NULL the IPIQ is being
1336 * run via doreti or an interrupt then preemption can be allowed.
1337 *
1338 * To allow preemption we have to drop the critical section so only
1339 * one is present in _lwkt_schedule_post.
1340 */
1341static void
1342lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1343{
1344 thread_t td = curthread;
1345 thread_t ntd = arg;
1346
1347 if (frame && ntd->td_preemptable) {
1348 crit_exit_noyield(td);
85946b6c 1349 _lwkt_schedule(ntd);
e381e77c
MD
1350 crit_enter_quick(td);
1351 } else {
85946b6c 1352 _lwkt_schedule(ntd);
e381e77c
MD
1353 }
1354}
1355
d9eea1a5 1356/*
52eedfb5
MD
1357 * Thread migration using a 'Pull' method. The thread may or may not be
1358 * the current thread. It MUST be descheduled and in a stable state.
1359 * lwkt_giveaway() must be called on the cpu owning the thread.
1360 *
1361 * At any point after lwkt_giveaway() is called, the target cpu may
1362 * 'pull' the thread by calling lwkt_acquire().
1363 *
ae8e83e6
MD
1364 * We have to make sure the thread is not sitting on a per-cpu tsleep
1365 * queue or it will blow up when it moves to another cpu.
1366 *
52eedfb5 1367 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1368 */
52eedfb5
MD
1369void
1370lwkt_giveaway(thread_t td)
1371{
3b4192fb 1372 globaldata_t gd = mycpu;
52eedfb5 1373
3b4192fb
MD
1374 crit_enter_gd(gd);
1375 if (td->td_flags & TDF_TSLEEPQ)
1376 tsleep_remove(td);
1377 KKASSERT(td->td_gd == gd);
1378 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1379 td->td_flags |= TDF_MIGRATING;
1380 crit_exit_gd(gd);
52eedfb5
MD
1381}
1382
a2a5ad0d
MD
1383void
1384lwkt_acquire(thread_t td)
1385{
37af14fe
MD
1386 globaldata_t gd;
1387 globaldata_t mygd;
cc9b6223 1388 int retry = 10000000;
a2a5ad0d 1389
52eedfb5 1390 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1391 gd = td->td_gd;
37af14fe 1392 mygd = mycpu;
52eedfb5 1393 if (gd != mycpu) {
35238fa5 1394 cpu_lfence();
52eedfb5 1395 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1396 crit_enter_gd(mygd);
cfaeae2a 1397 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23 1398 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
df910c23 1399 lwkt_process_ipiq();
52eedfb5 1400 cpu_lfence();
cc9b6223
MD
1401 if (--retry == 0) {
1402 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1403 td, td->td_flags);
1404 retry = 10000000;
1405 }
a86ce0cd
MD
1406#ifdef _KERNEL_VIRTUAL
1407 pthread_yield();
1408#endif
df910c23 1409 }
cfaeae2a 1410 DEBUG_POP_INFO();
562273ea 1411 cpu_mfence();
37af14fe 1412 td->td_gd = mygd;
52eedfb5
MD
1413 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1414 td->td_flags &= ~TDF_MIGRATING;
1415 crit_exit_gd(mygd);
1416 } else {
1417 crit_enter_gd(mygd);
1418 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1419 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1420 crit_exit_gd(mygd);
a2a5ad0d
MD
1421 }
1422}
1423
f1d1c3fa
MD
1424/*
1425 * Generic deschedule. Descheduling threads other then your own should be
1426 * done only in carefully controlled circumstances. Descheduling is
1427 * asynchronous.
1428 *
1429 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1430 */
1431void
1432lwkt_deschedule(thread_t td)
1433{
f1d1c3fa
MD
1434 crit_enter();
1435 if (td == curthread) {
1436 _lwkt_dequeue(td);
1437 } else {
a72187e9 1438 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1439 _lwkt_dequeue(td);
1440 } else {
b8a98473 1441 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1442 }
1443 }
1444 crit_exit();
1445}
1446
4b5f931b
MD
1447/*
1448 * Set the target thread's priority. This routine does not automatically
1449 * switch to a higher priority thread, LWKT threads are not designed for
1450 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1451 */
1452void
1453lwkt_setpri(thread_t td, int pri)
1454{
f9235b6d
MD
1455 if (td->td_pri != pri) {
1456 KKASSERT(pri >= 0);
1457 crit_enter();
1458 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1459 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1460 _lwkt_dequeue(td);
1461 td->td_pri = pri;
1462 _lwkt_enqueue(td);
1463 } else {
1464 td->td_pri = pri;
1465 }
1466 crit_exit();
26a0694b 1467 }
26a0694b
MD
1468}
1469
03bd0a5e
MD
1470/*
1471 * Set the initial priority for a thread prior to it being scheduled for
1472 * the first time. The thread MUST NOT be scheduled before or during
1473 * this call. The thread may be assigned to a cpu other then the current
1474 * cpu.
1475 *
1476 * Typically used after a thread has been created with TDF_STOPPREQ,
1477 * and before the thread is initially scheduled.
1478 */
1479void
1480lwkt_setpri_initial(thread_t td, int pri)
1481{
1482 KKASSERT(pri >= 0);
1483 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1484 td->td_pri = pri;
03bd0a5e
MD
1485}
1486
26a0694b
MD
1487void
1488lwkt_setpri_self(int pri)
1489{
1490 thread_t td = curthread;
1491
4b5f931b
MD
1492 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1493 crit_enter();
1494 if (td->td_flags & TDF_RUNQ) {
1495 _lwkt_dequeue(td);
f9235b6d 1496 td->td_pri = pri;
4b5f931b
MD
1497 _lwkt_enqueue(td);
1498 } else {
f9235b6d 1499 td->td_pri = pri;
4b5f931b
MD
1500 }
1501 crit_exit();
1502}
1503
f9235b6d 1504/*
85946b6c 1505 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1506 */
1507void
85946b6c 1508lwkt_schedulerclock(thread_t td)
f9235b6d 1509{
85946b6c
MD
1510 globaldata_t gd = td->td_gd;
1511 thread_t xtd;
2a418930 1512
85946b6c
MD
1513 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1514 /*
1515 * If the current thread is at the head of the runq shift it to the
1516 * end of any equal-priority threads and request a LWKT reschedule
1517 * if it moved.
d992c377
MD
1518 *
1519 * Ignore upri in this situation. There will only be one user thread
1520 * in user mode, all others will be user threads running in kernel
1521 * mode and we have to make sure they get some cpu.
85946b6c
MD
1522 */
1523 xtd = TAILQ_NEXT(td, td_threadq);
1524 if (xtd && xtd->td_pri == td->td_pri) {
1525 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1526 while (xtd && xtd->td_pri == td->td_pri)
1527 xtd = TAILQ_NEXT(xtd, td_threadq);
1528 if (xtd)
1529 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1530 else
1531 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1532 need_lwkt_resched();
f9235b6d 1533 }
85946b6c
MD
1534 } else {
1535 /*
1536 * If we scheduled a thread other than the one at the head of the
1537 * queue always request a reschedule every tick.
1538 */
1539 need_lwkt_resched();
f9235b6d
MD
1540 }
1541}
1542
5d21b981 1543/*
52eedfb5
MD
1544 * Migrate the current thread to the specified cpu.
1545 *
cc9b6223
MD
1546 * This is accomplished by descheduling ourselves from the current cpu
1547 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1548 * 'old' thread wants to migrate after it has been completely switched out
1549 * and will complete the migration.
1550 *
1551 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1552 *
1553 * We must be sure to release our current process designation (if a user
1554 * process) before clearing out any tsleepq we are on because the release
1555 * code may re-add us.
ae8e83e6
MD
1556 *
1557 * We must be sure to remove ourselves from the current cpu's tsleepq
1558 * before potentially moving to another queue. The thread can be on
1559 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1560 */
5d21b981
MD
1561
1562void
1563lwkt_setcpu_self(globaldata_t rgd)
1564{
5d21b981
MD
1565 thread_t td = curthread;
1566
1567 if (td->td_gd != rgd) {
1568 crit_enter_quick(td);
cc9b6223 1569
95858b91
MD
1570 if (td->td_release)
1571 td->td_release(td);
ae8e83e6 1572 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1573 tsleep_remove(td);
cc9b6223
MD
1574
1575 /*
1576 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1577 * trying to deschedule ourselves and switch away, then deschedule
1578 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1579 * call lwkt_switch() to complete the operation.
1580 */
5d21b981
MD
1581 td->td_flags |= TDF_MIGRATING;
1582 lwkt_deschedule_self(td);
52eedfb5 1583 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1584 td->td_migrate_gd = rgd;
5d21b981 1585 lwkt_switch();
cc9b6223
MD
1586
1587 /*
1588 * We are now on the target cpu
1589 */
1590 KKASSERT(rgd == mycpu);
52eedfb5 1591 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1592 crit_exit_quick(td);
1593 }
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1594}
1595
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1596void
1597lwkt_migratecpu(int cpuid)
1598{
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1599 globaldata_t rgd;
1600
1601 rgd = globaldata_find(cpuid);
1602 lwkt_setcpu_self(rgd);
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1603}
1604
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1605/*
1606 * Remote IPI for cpu migration (called while in a critical section so we
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1607 * do not have to enter another one).
1608 *
1609 * The thread (td) has already been completely descheduled from the
1610 * originating cpu and we can simply assert the case. The thread is
1611 * assigned to the new cpu and enqueued.
5d21b981 1612 *
cc9b6223 1613 * The thread will re-add itself to tdallq when it resumes execution.
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1614 */
1615static void
1616lwkt_setcpu_remote(void *arg)
1617{
1618 thread_t td = arg;
1619 globaldata_t gd = mycpu;
1620
cc9b6223 1621 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1622 td->td_gd = gd;
562273ea 1623 cpu_mfence();
5d21b981 1624 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1625 KKASSERT(td->td_migrate_gd == NULL);
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1626 KKASSERT(td->td_lwp == NULL ||
1627 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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1628 _lwkt_enqueue(td);
1629}
1630
553ea3c8 1631struct lwp *
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1632lwkt_preempted_proc(void)
1633{
73e4f7b9 1634 thread_t td = curthread;
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1635 while (td->td_preempted)
1636 td = td->td_preempted;
553ea3c8 1637 return(td->td_lwp);
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1638}
1639
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1640/*
1641 * Create a kernel process/thread/whatever. It shares it's address space
1642 * with proc0 - ie: kernel only.
1643 *
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1644 * If the cpu is not specified one will be selected. In the future
1645 * specifying a cpu of -1 will enable kernel thread migration between
1646 * cpus.
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1647 */
1648int
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1649lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1650 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1651{
73e4f7b9 1652 thread_t td;
e2565a42 1653 __va_list ap;
99df837e 1654
d3d32139 1655 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1656 tdflags);
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1657 if (tdp)
1658 *tdp = td;
709799ea 1659 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1660
1661 /*
1662 * Set up arg0 for 'ps' etc
1663 */
e2565a42 1664 __va_start(ap, fmt);
379210cb 1665 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1666 __va_end(ap);
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1667
1668 /*
1669 * Schedule the thread to run
1670 */
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1671 if (td->td_flags & TDF_NOSTART)
1672 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1673 else
4643740a 1674 lwkt_schedule(td);
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1675 return 0;
1676}
1677
1678/*
1679 * Destroy an LWKT thread. Warning! This function is not called when
1680 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1681 * uses a different reaping mechanism.
1682 */
1683void
1684lwkt_exit(void)
1685{
1686 thread_t td = curthread;
c070746a 1687 thread_t std;
8826f33a 1688 globaldata_t gd;
99df837e 1689
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1690 /*
1691 * Do any cleanup that might block here
1692 */
99df837e 1693 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1694 kprintf("kthread %p %s has exited\n", td, td->td_comm);
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1695 biosched_done(td);
1696 dsched_exit_thread(td);
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1697
1698 /*
1699 * Get us into a critical section to interlock gd_freetd and loop
1700 * until we can get it freed.
1701 *
1702 * We have to cache the current td in gd_freetd because objcache_put()ing
1703 * it would rip it out from under us while our thread is still active.
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1704 *
1705 * We are the current thread so of course our own TDF_RUNNING bit will
1706 * be set, so unlike the lwp reap code we don't wait for it to clear.
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1707 */
1708 gd = mycpu;
37af14fe 1709 crit_enter_quick(td);
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1710 for (;;) {
1711 if (td->td_refs) {
1712 tsleep(td, 0, "tdreap", 1);
1713 continue;
1714 }
1715 if ((std = gd->gd_freetd) != NULL) {
1716 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1717 gd->gd_freetd = NULL;
1718 objcache_put(thread_cache, std);
1719 continue;
1720 }
1721 break;
c070746a 1722 }
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1723
1724 /*
1725 * Remove thread resources from kernel lists and deschedule us for
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1726 * the last time. We cannot block after this point or we may end
1727 * up with a stale td on the tsleepq.
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1728 *
1729 * None of this may block, the critical section is the only thing
1730 * protecting tdallq and the only thing preventing new lwkt_hold()
1731 * thread refs now.
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1732 */
1733 if (td->td_flags & TDF_TSLEEPQ)
1734 tsleep_remove(td);
37af14fe 1735 lwkt_deschedule_self(td);
e56e4dea 1736 lwkt_remove_tdallq(td);
74c9628e 1737 KKASSERT(td->td_refs == 0);
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1738
1739 /*
1740 * Final cleanup
1741 */
1742 KKASSERT(gd->gd_freetd == NULL);
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1743 if (td->td_flags & TDF_ALLOCATED_THREAD)
1744 gd->gd_freetd = td;
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1745 cpu_thread_exit();
1746}
1747
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1748void
1749lwkt_remove_tdallq(thread_t td)
1750{
1751 KKASSERT(td->td_gd == mycpu);
1752 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1753}
1754
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1755/*
1756 * Code reduction and branch prediction improvements. Call/return
1757 * overhead on modern cpus often degenerates into 0 cycles due to
1758 * the cpu's branch prediction hardware and return pc cache. We
1759 * can take advantage of this by not inlining medium-complexity
1760 * functions and we can also reduce the branch prediction impact
1761 * by collapsing perfectly predictable branches into a single
1762 * procedure instead of duplicating it.
1763 *
1764 * Is any of this noticeable? Probably not, so I'll take the
1765 * smaller code size.
1766 */
1767void
b6468f56 1768crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1769{
b6468f56 1770 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1771}
1772
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1773void
1774crit_panic(void)
1775{
1776 thread_t td = curthread;
850634cc 1777 int lcrit = td->td_critcount;
2d93b37a 1778
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1779 td->td_critcount = 0;
1780 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1781 /* NOT REACHED */
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1782}
1783
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1784/*
1785 * Called from debugger/panic on cpus which have been stopped. We must still
b19f40a4 1786 * process the IPIQ while stopped.
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1787 *
1788 * If we are dumping also try to process any pending interrupts. This may
1789 * or may not work depending on the state of the cpu at the point it was
1790 * stopped.
1791 */
1792void
1793lwkt_smp_stopped(void)
1794{
1795 globaldata_t gd = mycpu;
1796
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1797 if (dumping) {
1798 lwkt_process_ipiq();
b19f40a4 1799 --gd->gd_intr_nesting_level;
bd8015ca 1800 splz();
b19f40a4 1801 ++gd->gd_intr_nesting_level;
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1802 } else {
1803 lwkt_process_ipiq();
1804 }
bd8015ca 1805}