threaded interrupts 1: Rewrite the ICU interrupt code, splz, and doreti code.
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
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1/*
2 * Copyright (c) 2003 Matthew Dillon <dillon@backplane.com>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
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26 * Each cpu in a system has its own self-contained light weight kernel
27 * thread scheduler, which means that generally speaking we only need
28 * to use a critical section to prevent hicups.
29 *
ef0fdad1 30 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.9 2003/06/29 03:28:44 dillon Exp $
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31 */
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/kernel.h>
36#include <sys/proc.h>
37#include <sys/rtprio.h>
38#include <sys/queue.h>
f1d1c3fa 39#include <sys/thread2.h>
7d0bac62 40#include <sys/sysctl.h>
99df837e 41#include <sys/kthread.h>
f1d1c3fa 42#include <machine/cpu.h>
99df837e 43#include <sys/lock.h>
f1d1c3fa 44
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45#include <vm/vm.h>
46#include <vm/vm_param.h>
47#include <vm/vm_kern.h>
48#include <vm/vm_object.h>
49#include <vm/vm_page.h>
50#include <vm/vm_map.h>
51#include <vm/vm_pager.h>
52#include <vm/vm_extern.h>
53#include <vm/vm_zone.h>
54
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55#include <machine/stdarg.h>
56
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57static int untimely_switch = 0;
58SYSCTL_INT(_debug, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, "");
59
60
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61static __inline
62void
63_lwkt_dequeue(thread_t td)
64{
65 if (td->td_flags & TDF_RUNQ) {
66 td->td_flags &= ~TDF_RUNQ;
67 TAILQ_REMOVE(&mycpu->gd_tdrunq, td, td_threadq);
68 }
69}
70
71static __inline
72void
73_lwkt_enqueue(thread_t td)
74{
75 if ((td->td_flags & TDF_RUNQ) == 0) {
76 td->td_flags |= TDF_RUNQ;
77 TAILQ_INSERT_TAIL(&mycpu->gd_tdrunq, td, td_threadq);
78 }
79}
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80
81/*
82 * LWKTs operate on a per-cpu basis
83 *
84 * YYY implement strict priorities & round-robin at the same priority
85 */
86void
87lwkt_gdinit(struct globaldata *gd)
88{
89 TAILQ_INIT(&gd->gd_tdrunq);
90}
91
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92/*
93 * Initialize a thread wait structure prior to first use.
94 *
95 * NOTE! called from low level boot code, we cannot do anything fancy!
96 */
97void
98lwkt_init_wait(lwkt_wait_t w)
99{
100 TAILQ_INIT(&w->wa_waitq);
101}
102
103/*
104 * Create a new thread. The thread must be associated with a process context
105 * or LWKT start address before it can be scheduled.
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106 *
107 * If you intend to create a thread without a process context this function
108 * does everything except load the startup and switcher function.
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109 */
110thread_t
ef0fdad1 111lwkt_alloc_thread(struct thread *td)
7d0bac62 112{
99df837e 113 void *stack;
ef0fdad1 114 int flags = 0;
7d0bac62 115
99df837e 116 crit_enter();
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117 if (td == NULL) {
118 if (mycpu->gd_tdfreecount > 0) {
119 --mycpu->gd_tdfreecount;
120 td = TAILQ_FIRST(&mycpu->gd_tdfreeq);
121 KASSERT(td != NULL && (td->td_flags & TDF_EXITED),
122 ("lwkt_alloc_thread: unexpected NULL or corrupted td"));
123 TAILQ_REMOVE(&mycpu->gd_tdfreeq, td, td_threadq);
124 crit_exit();
125 stack = td->td_kstack;
126 flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
127 } else {
128 crit_exit();
129 td = zalloc(thread_zone);
130 td->td_kstack = NULL;
131 flags |= TDF_ALLOCATED_THREAD;
132 }
133 }
134 if ((stack = td->td_kstack) == NULL) {
99df837e 135 stack = (void *)kmem_alloc(kernel_map, UPAGES * PAGE_SIZE);
ef0fdad1 136 flags |= TDF_ALLOCATED_STACK;
99df837e 137 }
ef0fdad1 138 lwkt_init_thread(td, stack, flags);
99df837e 139 return(td);
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140}
141
142/*
143 * Initialize a preexisting thread structure. This function is used by
144 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
145 *
146 * NOTE! called from low level boot code, we cannot do anything fancy!
147 */
148void
99df837e 149lwkt_init_thread(thread_t td, void *stack, int flags)
7d0bac62 150{
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151 bzero(td, sizeof(struct thread));
152 td->td_kstack = stack;
153 td->td_flags |= flags;
154 pmap_init_thread(td);
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155}
156
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157void
158lwkt_free_thread(struct thread *td)
159{
160 KASSERT(td->td_flags & TDF_EXITED,
161 ("lwkt_free_thread: did not exit! %p", td));
162
163 crit_enter();
164 if (mycpu->gd_tdfreecount < CACHE_NTHREADS &&
165 (td->td_flags & TDF_ALLOCATED_THREAD)
166 ) {
167 ++mycpu->gd_tdfreecount;
168 TAILQ_INSERT_HEAD(&mycpu->gd_tdfreeq, td, td_threadq);
169 crit_exit();
170 } else {
171 crit_exit();
172 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
173 kmem_free(kernel_map,
174 (vm_offset_t)td->td_kstack, UPAGES * PAGE_SIZE);
175 td->td_kstack = NULL;
176 }
177 if (td->td_flags & TDF_ALLOCATED_THREAD)
178 zfree(thread_zone, td);
179 }
180}
181
182
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183/*
184 * Switch to the next runnable lwkt. If no LWKTs are runnable then
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185 * switch to the idlethread. Switching must occur within a critical
186 * section to avoid races with the scheduling queue.
187 *
188 * We always have full control over our cpu's run queue. Other cpus
189 * that wish to manipulate our queue must use the cpu_*msg() calls to
190 * talk to our cpu, so a critical section is all that is needed and
191 * the result is very, very fast thread switching.
192 *
193 * We always 'own' our own thread and the threads on our run queue,l
194 * due to TDF_RUNNING or TDF_RUNQ being set. We can safely clear
195 * TDF_RUNNING while in a critical section.
196 *
197 * The td_switch() function must be called while in the critical section.
198 * This function saves as much state as is appropriate for the type of
199 * thread.
200 *
201 * (self contained on a per cpu basis)
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202 */
203void
204lwkt_switch(void)
205{
f1d1c3fa 206 thread_t td = curthread;
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207 thread_t ntd;
208
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209 if (mycpu->gd_intr_nesting_level)
210 panic("lwkt_switch: cannot switch from within an interrupt\n");
211
f1d1c3fa 212 crit_enter();
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213 if ((ntd = td->td_preempted) != NULL) {
214 /*
215 * We had preempted another thread on this cpu, resume the preempted
216 * thread.
217 */
218 td->td_preempted = NULL;
219 ntd->td_flags &= ~TDF_PREEMPTED;
220 } else if ((ntd = TAILQ_FIRST(&mycpu->gd_tdrunq)) != NULL) {
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221 TAILQ_REMOVE(&mycpu->gd_tdrunq, ntd, td_threadq);
222 TAILQ_INSERT_TAIL(&mycpu->gd_tdrunq, ntd, td_threadq);
8ad65e08 223 } else {
85100692 224 ntd = mycpu->gd_idletd;
f1d1c3fa 225 }
99df837e 226 if (td != ntd)
f1d1c3fa 227 td->td_switch(ntd);
f1d1c3fa 228 crit_exit();
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229}
230
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231/*
232 * Yield our thread while higher priority threads are pending. This is
233 * typically called when we leave a critical section but it can be safely
234 * called while we are in a critical section.
235 *
236 * This function will not generally yield to equal priority threads but it
237 * can occur as a side effect. Note that lwkt_switch() is called from
238 * inside the critical section to pervent its own crit_exit() from reentering
239 * lwkt_yield_quick().
240 *
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241 * gd_reqpri indicates that *something* changed, e.g. an interrupt or softint
242 * came along but was blocked and made pending.
243 *
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244 * (self contained on a per cpu basis)
245 */
246void
247lwkt_yield_quick(void)
248{
249 thread_t td = curthread;
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250
251 if ((td->td_pri & TDPRI_MASK) < mycpu->gd_reqpri) {
252 mycpu->gd_reqpri = 0;
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253 splz();
254 }
255
256 /*
257 * YYY enabling will cause wakeup() to task-switch, which really
258 * confused the old 4.x code. This is a good way to simulate
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259 * preemption and MP without actually doing preemption or MP, because a
260 * lot of code assumes that wakeup() does not block.
f1d1c3fa 261 */
ef0fdad1 262 if (untimely_switch && mycpu->gd_intr_nesting_level == 0) {
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263 crit_enter();
264 /*
265 * YYY temporary hacks until we disassociate the userland scheduler
266 * from the LWKT scheduler.
267 */
268 if (td->td_flags & TDF_RUNQ) {
269 lwkt_switch(); /* will not reenter yield function */
270 } else {
271 lwkt_schedule_self(); /* make sure we are scheduled */
272 lwkt_switch(); /* will not reenter yield function */
273 lwkt_deschedule_self(); /* make sure we are descheduled */
274 }
275 crit_exit_noyield();
276 }
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277}
278
8ad65e08 279/*
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280 * This implements a normal yield which, unlike _quick, will yield to equal
281 * priority threads as well. Note that gd_reqpri tests will be handled by
282 * the crit_exit() call in lwkt_switch().
283 *
284 * (self contained on a per cpu basis)
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285 */
286void
f1d1c3fa 287lwkt_yield(void)
8ad65e08 288{
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289 lwkt_schedule_self();
290 lwkt_switch();
291}
292
293/*
294 * Schedule a thread to run. As the current thread we can always safely
295 * schedule ourselves, and a shortcut procedure is provided for that
296 * function.
297 *
298 * (non-blocking, self contained on a per cpu basis)
299 */
300void
301lwkt_schedule_self(void)
302{
303 thread_t td = curthread;
304
305 crit_enter();
306 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
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307 _lwkt_enqueue(td);
308 crit_exit();
8ad65e08 309}
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310
311/*
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312 * Generic schedule. Possibly schedule threads belonging to other cpus and
313 * deal with threads that might be blocked on a wait queue.
314 *
315 * This function will queue requests asynchronously when possible, but may
316 * block if no request structures are available. Upon return the caller
317 * should note that the scheduling request may not yet have been processed
318 * by the target cpu.
319 *
320 * YYY this is one of the best places to implement any load balancing code.
321 * Load balancing can be accomplished by requesting other sorts of actions
322 * for the thread in question.
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323 */
324void
325lwkt_schedule(thread_t td)
326{
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327 crit_enter();
328 if (td == curthread) {
329 _lwkt_enqueue(td);
330 } else {
331 lwkt_wait_t w;
332
333 /*
334 * If the thread is on a wait list we have to send our scheduling
335 * request to the owner of the wait structure. Otherwise we send
336 * the scheduling request to the cpu owning the thread. Races
337 * are ok, the target will forward the message as necessary (the
338 * message may chase the thread around before it finally gets
339 * acted upon).
340 *
341 * (remember, wait structures use stable storage)
342 */
343 if ((w = td->td_wait) != NULL) {
344 if (lwkt_havetoken(&w->wa_token)) {
345 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
346 --w->wa_count;
347 td->td_wait = NULL;
d0e06f83 348 if (td->td_cpu == mycpu->gd_cpuid) {
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349 _lwkt_enqueue(td);
350 } else {
351 panic("lwkt_schedule: cpu mismatch1");
8ad65e08 352#if 0
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353 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
354 initScheduleReqMsg_Wait(&msg.mu_SchedReq, td, w);
355 cpu_sendnormsg(&msg.mu_Msg);
8ad65e08 356#endif
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357 }
358 } else {
359 panic("lwkt_schedule: cpu mismatch2");
360#if 0
361 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
362 initScheduleReqMsg_Wait(&msg.mu_SchedReq, td, w);
363 cpu_sendnormsg(&msg.mu_Msg);
364#endif
365 }
366 } else {
367 /*
368 * If the wait structure is NULL and we own the thread, there
369 * is no race (since we are in a critical section). If we
370 * do not own the thread there might be a race but the
371 * target cpu will deal with it.
372 */
d0e06f83 373 if (td->td_cpu == mycpu->gd_cpuid) {
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374 _lwkt_enqueue(td);
375 } else {
376 panic("lwkt_schedule: cpu mismatch3");
377#if 0
378 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
379 initScheduleReqMsg_Thread(&msg.mu_SchedReq, td);
380 cpu_sendnormsg(&msg.mu_Msg);
381#endif
382 }
383 }
8ad65e08 384 }
f1d1c3fa 385 crit_exit();
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386}
387
388/*
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389 * Deschedule a thread.
390 *
391 * (non-blocking, self contained on a per cpu basis)
392 */
393void
394lwkt_deschedule_self(void)
395{
396 thread_t td = curthread;
397
398 crit_enter();
399 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
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400 _lwkt_dequeue(td);
401 crit_exit();
402}
403
404/*
405 * Generic deschedule. Descheduling threads other then your own should be
406 * done only in carefully controlled circumstances. Descheduling is
407 * asynchronous.
408 *
409 * This function may block if the cpu has run out of messages.
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410 */
411void
412lwkt_deschedule(thread_t td)
413{
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414 crit_enter();
415 if (td == curthread) {
416 _lwkt_dequeue(td);
417 } else {
d0e06f83 418 if (td->td_cpu == mycpu->gd_cpuid) {
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419 _lwkt_dequeue(td);
420 } else {
421 panic("lwkt_deschedule: cpu mismatch");
422#if 0
423 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
424 initDescheduleReqMsg_Thread(&msg.mu_DeschedReq, td);
425 cpu_sendnormsg(&msg.mu_Msg);
426#endif
427 }
428 }
429 crit_exit();
430}
431
432/*
433 * This function deschedules the current thread and blocks on the specified
434 * wait queue. We obtain ownership of the wait queue in order to block
435 * on it. A generation number is used to interlock the wait queue in case
436 * it gets signalled while we are blocked waiting on the token.
437 *
438 * Note: alternatively we could dequeue our thread and then message the
439 * target cpu owning the wait queue. YYY implement as sysctl.
440 *
441 * Note: wait queue signals normally ping-pong the cpu as an optimization.
442 */
443void
ae8050a4 444lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen)
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445{
446 thread_t td = curthread;
f1d1c3fa 447
f1d1c3fa 448 lwkt_gettoken(&w->wa_token);
ae8050a4 449 if (w->wa_gen == *gen) {
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450 _lwkt_dequeue(td);
451 TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq);
452 ++w->wa_count;
453 td->td_wait = w;
ae8050a4 454 td->td_wmesg = wmesg;
f1d1c3fa 455 lwkt_switch();
8ad65e08 456 }
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457 /* token might be lost, doesn't matter for gen update */
458 *gen = w->wa_gen;
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459 lwkt_reltoken(&w->wa_token);
460}
461
462/*
463 * Signal a wait queue. We gain ownership of the wait queue in order to
464 * signal it. Once a thread is removed from the wait queue we have to
465 * deal with the cpu owning the thread.
466 *
467 * Note: alternatively we could message the target cpu owning the wait
468 * queue. YYY implement as sysctl.
469 */
470void
471lwkt_signal(lwkt_wait_t w)
472{
473 thread_t td;
474 int count;
475
476 lwkt_gettoken(&w->wa_token);
477 ++w->wa_gen;
478 count = w->wa_count;
479 while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) {
480 --count;
481 --w->wa_count;
482 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
483 td->td_wait = NULL;
ae8050a4 484 td->td_wmesg = NULL;
d0e06f83 485 if (td->td_cpu == mycpu->gd_cpuid) {
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486 _lwkt_enqueue(td);
487 } else {
488#if 0
489 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
490 initScheduleReqMsg_Thread(&msg.mu_SchedReq, td);
491 cpu_sendnormsg(&msg.mu_Msg);
492#endif
493 panic("lwkt_signal: cpu mismatch");
494 }
495 lwkt_regettoken(&w->wa_token);
496 }
497 lwkt_reltoken(&w->wa_token);
498}
499
500/*
501 * Aquire ownership of a token
502 *
503 * Aquire ownership of a token. The token may have spl and/or critical
504 * section side effects, depending on its purpose. These side effects
505 * guarentee that you will maintain ownership of the token as long as you
506 * do not block. If you block you may lose access to the token (but you
507 * must still release it even if you lose your access to it).
508 *
509 * Note that the spl and critical section characteristics of a token
510 * may not be changed once the token has been initialized.
511 */
512void
513lwkt_gettoken(lwkt_token_t tok)
514{
515 /*
516 * Prevent preemption so the token can't be taken away from us once
517 * we gain ownership of it. Use a synchronous request which might
518 * block. The request will be forwarded as necessary playing catchup
519 * to the token.
520 */
521 crit_enter();
522#if 0
d0e06f83 523 while (tok->t_cpu != mycpu->gd_cpuid) {
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524 lwkt_cpu_msg_union msg;
525 initTokenReqMsg(&msg.mu_TokenReq);
526 cpu_domsg(&msg);
527 }
528#endif
529 /*
530 * leave us in a critical section on return. This will be undone
531 * by lwkt_reltoken()
532 */
533}
534
535/*
536 * Release your ownership of a token. Releases must occur in reverse
537 * order to aquisitions, eventually so priorities can be unwound properly
538 * like SPLs. At the moment the actual implemention doesn't care.
539 *
540 * We can safely hand a token that we own to another cpu without notifying
541 * it, but once we do we can't get it back without requesting it (unless
542 * the other cpu hands it back to us before we check).
543 *
544 * We might have lost the token, so check that.
545 */
546void
547lwkt_reltoken(lwkt_token_t tok)
548{
d0e06f83 549 if (tok->t_cpu == mycpu->gd_cpuid) {
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550 tok->t_cpu = tok->t_reqcpu;
551 }
552 crit_exit();
553}
554
555/*
556 * Reaquire a token that might have been lost. Returns 1 if we blocked
557 * while reaquiring the token (meaning that you might have lost other
558 * tokens you held when you made this call), return 0 if we did not block.
559 */
560int
561lwkt_regettoken(lwkt_token_t tok)
562{
563#if 0
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564 if (tok->t_cpu != mycpu->gd_cpuid) {
565 while (tok->t_cpu != mycpu->gd_cpuid) {
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566 lwkt_cpu_msg_union msg;
567 initTokenReqMsg(&msg.mu_TokenReq);
568 cpu_domsg(&msg);
569 }
570 return(1);
571 }
572#endif
573 return(0);
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574}
575
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576/*
577 * Create a kernel process/thread/whatever. It shares it's address space
578 * with proc0 - ie: kernel only.
579 *
580 * XXX should be renamed to lwkt_create()
581 */
582int
583lwkt_create(void (*func)(void *), void *arg,
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584 struct thread **tdp, struct thread *template, int tdflags,
585 const char *fmt, ...)
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586{
587 struct thread *td;
588 va_list ap;
589
ef0fdad1 590 td = *tdp = lwkt_alloc_thread(template);
99df837e 591 cpu_set_thread_handler(td, kthread_exit, func, arg);
ef0fdad1 592 td->td_flags |= TDF_VERBOSE | tdflags;
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593
594 /*
595 * Set up arg0 for 'ps' etc
596 */
597 va_start(ap, fmt);
598 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
599 va_end(ap);
600
601 /*
602 * Schedule the thread to run
603 */
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604 if ((td->td_flags & TDF_STOPREQ) == 0)
605 lwkt_schedule(td);
606 else
607 td->td_flags &= ~TDF_STOPREQ;
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608 return 0;
609}
610
611/*
612 * Destroy an LWKT thread. Warning! This function is not called when
613 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
614 * uses a different reaping mechanism.
615 */
616void
617lwkt_exit(void)
618{
619 thread_t td = curthread;
620
621 if (td->td_flags & TDF_VERBOSE)
622 printf("kthread %p %s has exited\n", td, td->td_comm);
623 crit_enter();
624 lwkt_deschedule_self();
625 ++mycpu->gd_tdfreecount;
626 TAILQ_INSERT_TAIL(&mycpu->gd_tdfreeq, td, td_threadq);
627 cpu_thread_exit();
628}
629
630/*
631 * Create a kernel process/thread/whatever. It shares it's address space
ef0fdad1 632 * with proc0 - ie: kernel only. 5.x compatible.
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633 */
634int
635kthread_create(void (*func)(void *), void *arg,
636 struct thread **tdp, const char *fmt, ...)
637{
638 struct thread *td;
639 va_list ap;
640
ef0fdad1 641 td = *tdp = lwkt_alloc_thread(NULL);
99df837e
MD
642 cpu_set_thread_handler(td, kthread_exit, func, arg);
643 td->td_flags |= TDF_VERBOSE;
644
645 /*
646 * Set up arg0 for 'ps' etc
647 */
648 va_start(ap, fmt);
649 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
650 va_end(ap);
651
652 /*
653 * Schedule the thread to run
654 */
655 lwkt_schedule(td);
656 return 0;
657}
658
659/*
660 * Destroy an LWKT thread. Warning! This function is not called when
661 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
662 * uses a different reaping mechanism.
663 *
664 * XXX duplicates lwkt_exit()
665 */
666void
667kthread_exit(void)
668{
669 lwkt_exit();
670}
671