Fix a race in sysctl_out_proc() vs copyout() that could crash the kernel.
[dragonfly.git] / sys / kern / lwkt_thread.c
... / ...
CommitLineData
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 *
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 *
30 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.12 2003/06/30 19:50:31 dillon Exp $
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>
39#include <sys/thread2.h>
40#include <sys/sysctl.h>
41#include <sys/kthread.h>
42#include <machine/cpu.h>
43#include <sys/lock.h>
44
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
55#include <machine/stdarg.h>
56
57static int untimely_switch = 0;
58SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, "");
59static quad_t switch_count = 0;
60SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
61static quad_t preempt_hit = 0;
62SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, "");
63static quad_t preempt_miss = 0;
64SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, "");
65static quad_t preempt_weird = 0;
66SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
67
68/*
69 * These helper procedures handle the runq, they can only be called from
70 * within a critical section.
71 */
72static __inline
73void
74_lwkt_dequeue(thread_t td)
75{
76 if (td->td_flags & TDF_RUNQ) {
77 int nq = td->td_pri & TDPRI_MASK;
78 struct globaldata *gd = mycpu;
79
80 td->td_flags &= ~TDF_RUNQ;
81 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq);
82 /* runqmask is passively cleaned up by the switcher */
83 }
84}
85
86static __inline
87void
88_lwkt_enqueue(thread_t td)
89{
90 if ((td->td_flags & TDF_RUNQ) == 0) {
91 int nq = td->td_pri & TDPRI_MASK;
92 struct globaldata *gd = mycpu;
93
94 td->td_flags |= TDF_RUNQ;
95 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq);
96 gd->gd_runqmask |= 1 << nq;
97#if 0
98 /*
99 * YYY needs cli/sti protection? gd_reqpri set by interrupt
100 * when made pending. need better mechanism.
101 */
102 if (gd->gd_reqpri < (td->td_pri & TDPRI_MASK))
103 gd->gd_reqpri = (td->td_pri & TDPRI_MASK);
104#endif
105 }
106}
107
108/*
109 * LWKTs operate on a per-cpu basis
110 *
111 * YYY implement strict priorities & round-robin at the same priority
112 */
113void
114lwkt_gdinit(struct globaldata *gd)
115{
116 int i;
117
118 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
119 TAILQ_INIT(&gd->gd_tdrunq[i]);
120 gd->gd_runqmask = 0;
121}
122
123/*
124 * Initialize a thread wait structure prior to first use.
125 *
126 * NOTE! called from low level boot code, we cannot do anything fancy!
127 */
128void
129lwkt_init_wait(lwkt_wait_t w)
130{
131 TAILQ_INIT(&w->wa_waitq);
132}
133
134/*
135 * Create a new thread. The thread must be associated with a process context
136 * or LWKT start address before it can be scheduled.
137 *
138 * If you intend to create a thread without a process context this function
139 * does everything except load the startup and switcher function.
140 */
141thread_t
142lwkt_alloc_thread(struct thread *td)
143{
144 void *stack;
145 int flags = 0;
146
147 if (td == NULL) {
148 crit_enter();
149 if (mycpu->gd_tdfreecount > 0) {
150 --mycpu->gd_tdfreecount;
151 td = TAILQ_FIRST(&mycpu->gd_tdfreeq);
152 KASSERT(td != NULL && (td->td_flags & TDF_EXITED),
153 ("lwkt_alloc_thread: unexpected NULL or corrupted td"));
154 TAILQ_REMOVE(&mycpu->gd_tdfreeq, td, td_threadq);
155 crit_exit();
156 stack = td->td_kstack;
157 flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
158 } else {
159 crit_exit();
160 td = zalloc(thread_zone);
161 td->td_kstack = NULL;
162 flags |= TDF_ALLOCATED_THREAD;
163 }
164 }
165 if ((stack = td->td_kstack) == NULL) {
166 stack = (void *)kmem_alloc(kernel_map, UPAGES * PAGE_SIZE);
167 flags |= TDF_ALLOCATED_STACK;
168 }
169 lwkt_init_thread(td, stack, flags, mycpu);
170 return(td);
171}
172
173/*
174 * Initialize a preexisting thread structure. This function is used by
175 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
176 *
177 * NOTE! called from low level boot code, we cannot do anything fancy!
178 */
179void
180lwkt_init_thread(thread_t td, void *stack, int flags, struct globaldata *gd)
181{
182 bzero(td, sizeof(struct thread));
183 td->td_kstack = stack;
184 td->td_flags |= flags;
185 td->td_gd = gd;
186 td->td_pri = TDPRI_CRIT;
187 pmap_init_thread(td);
188}
189
190void
191lwkt_free_thread(struct thread *td)
192{
193 KASSERT(td->td_flags & TDF_EXITED,
194 ("lwkt_free_thread: did not exit! %p", td));
195
196 crit_enter();
197 if (mycpu->gd_tdfreecount < CACHE_NTHREADS &&
198 (td->td_flags & TDF_ALLOCATED_THREAD)
199 ) {
200 ++mycpu->gd_tdfreecount;
201 TAILQ_INSERT_HEAD(&mycpu->gd_tdfreeq, td, td_threadq);
202 crit_exit();
203 } else {
204 crit_exit();
205 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
206 kmem_free(kernel_map,
207 (vm_offset_t)td->td_kstack, UPAGES * PAGE_SIZE);
208 td->td_kstack = NULL;
209 }
210 if (td->td_flags & TDF_ALLOCATED_THREAD)
211 zfree(thread_zone, td);
212 }
213}
214
215
216/*
217 * Switch to the next runnable lwkt. If no LWKTs are runnable then
218 * switch to the idlethread. Switching must occur within a critical
219 * section to avoid races with the scheduling queue.
220 *
221 * We always have full control over our cpu's run queue. Other cpus
222 * that wish to manipulate our queue must use the cpu_*msg() calls to
223 * talk to our cpu, so a critical section is all that is needed and
224 * the result is very, very fast thread switching.
225 *
226 * We always 'own' our own thread and the threads on our run queue,l
227 * due to TDF_RUNNING or TDF_RUNQ being set. We can safely clear
228 * TDF_RUNNING while in a critical section.
229 *
230 * The td_switch() function must be called while in the critical section.
231 * This function saves as much state as is appropriate for the type of
232 * thread.
233 *
234 * (self contained on a per cpu basis)
235 */
236void
237lwkt_switch(void)
238{
239 struct globaldata *gd;
240 thread_t td = curthread;
241 thread_t ntd;
242
243 if (mycpu->gd_intr_nesting_level && td->td_preempted == NULL)
244 panic("lwkt_switch: cannot switch from within an interrupt, yet\n");
245
246 crit_enter();
247 ++switch_count;
248 if ((ntd = td->td_preempted) != NULL) {
249 /*
250 * We had preempted another thread on this cpu, resume the preempted
251 * thread. This occurs transparently, whether the preempted thread
252 * was scheduled or not (it may have been preempted after descheduling
253 * itself).
254 */
255 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
256 ntd->td_flags |= TDF_PREEMPT_DONE;
257 } else {
258 /*
259 * Priority queue / round-robin at each priority. Note that user
260 * processes run at a fixed, low priority and the user process
261 * scheduler deals with interactions between user processes
262 * by scheduling and descheduling them from the LWKT queue as
263 * necessary.
264 */
265 gd = mycpu;
266
267again:
268 if (gd->gd_runqmask) {
269 int nq = bsrl(gd->gd_runqmask);
270 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
271 gd->gd_runqmask &= ~(1 << nq);
272 goto again;
273 }
274 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
275 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
276 } else {
277 ntd = gd->gd_idletd;
278 }
279 }
280 KASSERT(ntd->td_pri >= TDPRI_CRIT,
281 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
282 if (td != ntd)
283 td->td_switch(ntd);
284 crit_exit();
285}
286
287/*
288 * Request that the target thread preempt the current thread. This only
289 * works if:
290 *
291 * + We aren't trying to preempt ourselves (it can happen!)
292 * + We are not currently being preempted
293 * + the target is not currently being preempted
294 *
295 * XXX at the moment we run the target thread in a critical section during
296 * the preemption in order to prevent the target from taking interrupts
297 * that *WE* can't. Preemption is strictly limited to interrupt threads
298 * and interrupt-like threads, outside of a critical section, and the
299 * preempted source thread will be resumed the instant the target blocks
300 * whether or not the source is scheduled (i.e. preemption is supposed to
301 * be as transparent as possible).
302 *
303 * This call is typically made from an interrupt handler like sched_ithd()
304 * which will only run if the current thread is not in a critical section,
305 * so we optimize the priority check a bit.
306 *
307 * CAREFUL! either we or the target thread may get interrupted during the
308 * switch.
309 */
310void
311lwkt_preempt(struct thread *ntd, int id)
312{
313 struct thread *td = curthread;
314
315 /*
316 * The caller has put us in a critical section, and in order to have
317 * gotten here in the first place the thread the caller interrupted
318 * cannot have been in a critical section before.
319 */
320 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
321 KASSERT((td->td_pri & ~TDPRI_MASK) == TDPRI_CRIT, ("BADPRI %d", td->td_pri));
322
323 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
324 ++preempt_weird;
325 return;
326 }
327 if (ntd->td_preempted) {
328 ++preempt_hit;
329 return;
330 }
331 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) {
332 ++preempt_miss;
333 return;
334 }
335
336 ++preempt_hit;
337 ntd->td_preempted = td;
338 td->td_flags |= TDF_PREEMPT_LOCK;
339 td->td_switch(ntd);
340 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
341 ntd->td_preempted = NULL;
342 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
343}
344
345/*
346 * Yield our thread while higher priority threads are pending. This is
347 * typically called when we leave a critical section but it can be safely
348 * called while we are in a critical section.
349 *
350 * This function will not generally yield to equal priority threads but it
351 * can occur as a side effect. Note that lwkt_switch() is called from
352 * inside the critical section to pervent its own crit_exit() from reentering
353 * lwkt_yield_quick().
354 *
355 * gd_reqpri indicates that *something* changed, e.g. an interrupt or softint
356 * came along but was blocked and made pending.
357 *
358 * (self contained on a per cpu basis)
359 */
360void
361lwkt_yield_quick(void)
362{
363 thread_t td = curthread;
364
365 if ((td->td_pri & TDPRI_MASK) < mycpu->gd_reqpri) {
366 mycpu->gd_reqpri = 0;
367 splz();
368 }
369
370 /*
371 * YYY enabling will cause wakeup() to task-switch, which really
372 * confused the old 4.x code. This is a good way to simulate
373 * preemption and MP without actually doing preemption or MP, because a
374 * lot of code assumes that wakeup() does not block.
375 */
376 if (untimely_switch && mycpu->gd_intr_nesting_level == 0) {
377 crit_enter();
378 /*
379 * YYY temporary hacks until we disassociate the userland scheduler
380 * from the LWKT scheduler.
381 */
382 if (td->td_flags & TDF_RUNQ) {
383 lwkt_switch(); /* will not reenter yield function */
384 } else {
385 lwkt_schedule_self(); /* make sure we are scheduled */
386 lwkt_switch(); /* will not reenter yield function */
387 lwkt_deschedule_self(); /* make sure we are descheduled */
388 }
389 crit_exit_noyield();
390 }
391}
392
393/*
394 * This implements a normal yield which, unlike _quick, will yield to equal
395 * priority threads as well. Note that gd_reqpri tests will be handled by
396 * the crit_exit() call in lwkt_switch().
397 *
398 * (self contained on a per cpu basis)
399 */
400void
401lwkt_yield(void)
402{
403 lwkt_schedule_self();
404 lwkt_switch();
405}
406
407/*
408 * Schedule a thread to run. As the current thread we can always safely
409 * schedule ourselves, and a shortcut procedure is provided for that
410 * function.
411 *
412 * (non-blocking, self contained on a per cpu basis)
413 */
414void
415lwkt_schedule_self(void)
416{
417 thread_t td = curthread;
418
419 crit_enter();
420 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
421 _lwkt_enqueue(td);
422 if (td->td_proc && td->td_proc->p_stat == SSLEEP)
423 panic("SCHED SELF PANIC");
424 crit_exit();
425}
426
427/*
428 * Generic schedule. Possibly schedule threads belonging to other cpus and
429 * deal with threads that might be blocked on a wait queue.
430 *
431 * This function will queue requests asynchronously when possible, but may
432 * block if no request structures are available. Upon return the caller
433 * should note that the scheduling request may not yet have been processed
434 * by the target cpu.
435 *
436 * YYY this is one of the best places to implement any load balancing code.
437 * Load balancing can be accomplished by requesting other sorts of actions
438 * for the thread in question.
439 */
440void
441lwkt_schedule(thread_t td)
442{
443 if ((td->td_flags & TDF_PREEMPT_LOCK) == 0 && td->td_proc
444 && td->td_proc->p_stat == SSLEEP
445 ) {
446 printf("PANIC schedule curtd = %p (%d %d) target %p (%d %d)\n",
447 curthread,
448 curthread->td_proc ? curthread->td_proc->p_pid : -1,
449 curthread->td_proc ? curthread->td_proc->p_stat : -1,
450 td,
451 td->td_proc ? curthread->td_proc->p_pid : -1,
452 td->td_proc ? curthread->td_proc->p_stat : -1
453 );
454 panic("SCHED PANIC");
455 }
456 crit_enter();
457 if (td == curthread) {
458 _lwkt_enqueue(td);
459 } else {
460 lwkt_wait_t w;
461
462 /*
463 * If the thread is on a wait list we have to send our scheduling
464 * request to the owner of the wait structure. Otherwise we send
465 * the scheduling request to the cpu owning the thread. Races
466 * are ok, the target will forward the message as necessary (the
467 * message may chase the thread around before it finally gets
468 * acted upon).
469 *
470 * (remember, wait structures use stable storage)
471 */
472 if ((w = td->td_wait) != NULL) {
473 if (lwkt_havetoken(&w->wa_token)) {
474 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
475 --w->wa_count;
476 td->td_wait = NULL;
477 if (td->td_cpu == mycpu->gd_cpuid) {
478 _lwkt_enqueue(td);
479 } else {
480 panic("lwkt_schedule: cpu mismatch1");
481#if 0
482 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
483 initScheduleReqMsg_Wait(&msg.mu_SchedReq, td, w);
484 cpu_sendnormsg(&msg.mu_Msg);
485#endif
486 }
487 } else {
488 panic("lwkt_schedule: cpu mismatch2");
489#if 0
490 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
491 initScheduleReqMsg_Wait(&msg.mu_SchedReq, td, w);
492 cpu_sendnormsg(&msg.mu_Msg);
493#endif
494 }
495 } else {
496 /*
497 * If the wait structure is NULL and we own the thread, there
498 * is no race (since we are in a critical section). If we
499 * do not own the thread there might be a race but the
500 * target cpu will deal with it.
501 */
502 if (td->td_cpu == mycpu->gd_cpuid) {
503 _lwkt_enqueue(td);
504 } else {
505 panic("lwkt_schedule: cpu mismatch3");
506#if 0
507 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
508 initScheduleReqMsg_Thread(&msg.mu_SchedReq, td);
509 cpu_sendnormsg(&msg.mu_Msg);
510#endif
511 }
512 }
513 }
514 crit_exit();
515}
516
517/*
518 * Deschedule a thread.
519 *
520 * (non-blocking, self contained on a per cpu basis)
521 */
522void
523lwkt_deschedule_self(void)
524{
525 thread_t td = curthread;
526
527 crit_enter();
528 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
529 _lwkt_dequeue(td);
530 crit_exit();
531}
532
533/*
534 * Generic deschedule. Descheduling threads other then your own should be
535 * done only in carefully controlled circumstances. Descheduling is
536 * asynchronous.
537 *
538 * This function may block if the cpu has run out of messages.
539 */
540void
541lwkt_deschedule(thread_t td)
542{
543 crit_enter();
544 if (td == curthread) {
545 _lwkt_dequeue(td);
546 } else {
547 if (td->td_cpu == mycpu->gd_cpuid) {
548 _lwkt_dequeue(td);
549 } else {
550 panic("lwkt_deschedule: cpu mismatch");
551#if 0
552 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
553 initDescheduleReqMsg_Thread(&msg.mu_DeschedReq, td);
554 cpu_sendnormsg(&msg.mu_Msg);
555#endif
556 }
557 }
558 crit_exit();
559}
560
561/*
562 * Set the target thread's priority. This routine does not automatically
563 * switch to a higher priority thread, LWKT threads are not designed for
564 * continuous priority changes. Yield if you want to switch.
565 *
566 * We have to retain the critical section count which uses the high bits
567 * of the td_pri field. The specified priority may also indicate zero or
568 * more critical sections by adding TDPRI_CRIT*N.
569 */
570void
571lwkt_setpri(thread_t td, int pri)
572{
573 KKASSERT(pri >= 0);
574 crit_enter();
575 if (td->td_flags & TDF_RUNQ) {
576 _lwkt_dequeue(td);
577 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
578 _lwkt_enqueue(td);
579 } else {
580 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
581 }
582 crit_exit();
583}
584
585void
586lwkt_setpri_self(int pri)
587{
588 thread_t td = curthread;
589
590 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
591 crit_enter();
592 if (td->td_flags & TDF_RUNQ) {
593 _lwkt_dequeue(td);
594 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
595 _lwkt_enqueue(td);
596 } else {
597 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
598 }
599 crit_exit();
600}
601
602struct proc *
603lwkt_preempted_proc(void)
604{
605 struct thread *td = curthread;
606 while (td->td_preempted)
607 td = td->td_preempted;
608 return(td->td_proc);
609}
610
611
612/*
613 * This function deschedules the current thread and blocks on the specified
614 * wait queue. We obtain ownership of the wait queue in order to block
615 * on it. A generation number is used to interlock the wait queue in case
616 * it gets signalled while we are blocked waiting on the token.
617 *
618 * Note: alternatively we could dequeue our thread and then message the
619 * target cpu owning the wait queue. YYY implement as sysctl.
620 *
621 * Note: wait queue signals normally ping-pong the cpu as an optimization.
622 */
623void
624lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen)
625{
626 thread_t td = curthread;
627
628 lwkt_gettoken(&w->wa_token);
629 if (w->wa_gen == *gen) {
630 _lwkt_dequeue(td);
631 TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq);
632 ++w->wa_count;
633 td->td_wait = w;
634 td->td_wmesg = wmesg;
635 lwkt_switch();
636 }
637 /* token might be lost, doesn't matter for gen update */
638 *gen = w->wa_gen;
639 lwkt_reltoken(&w->wa_token);
640}
641
642/*
643 * Signal a wait queue. We gain ownership of the wait queue in order to
644 * signal it. Once a thread is removed from the wait queue we have to
645 * deal with the cpu owning the thread.
646 *
647 * Note: alternatively we could message the target cpu owning the wait
648 * queue. YYY implement as sysctl.
649 */
650void
651lwkt_signal(lwkt_wait_t w)
652{
653 thread_t td;
654 int count;
655
656 lwkt_gettoken(&w->wa_token);
657 ++w->wa_gen;
658 count = w->wa_count;
659 while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) {
660 --count;
661 --w->wa_count;
662 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
663 td->td_wait = NULL;
664 td->td_wmesg = NULL;
665 if (td->td_cpu == mycpu->gd_cpuid) {
666 _lwkt_enqueue(td);
667 } else {
668#if 0
669 lwkt_cpu_msg_union_t msg = lwkt_getcpumsg();
670 initScheduleReqMsg_Thread(&msg.mu_SchedReq, td);
671 cpu_sendnormsg(&msg.mu_Msg);
672#endif
673 panic("lwkt_signal: cpu mismatch");
674 }
675 lwkt_regettoken(&w->wa_token);
676 }
677 lwkt_reltoken(&w->wa_token);
678}
679
680/*
681 * Aquire ownership of a token
682 *
683 * Aquire ownership of a token. The token may have spl and/or critical
684 * section side effects, depending on its purpose. These side effects
685 * guarentee that you will maintain ownership of the token as long as you
686 * do not block. If you block you may lose access to the token (but you
687 * must still release it even if you lose your access to it).
688 *
689 * Note that the spl and critical section characteristics of a token
690 * may not be changed once the token has been initialized.
691 */
692void
693lwkt_gettoken(lwkt_token_t tok)
694{
695 /*
696 * Prevent preemption so the token can't be taken away from us once
697 * we gain ownership of it. Use a synchronous request which might
698 * block. The request will be forwarded as necessary playing catchup
699 * to the token.
700 */
701 crit_enter();
702#if 0
703 while (tok->t_cpu != mycpu->gd_cpuid) {
704 lwkt_cpu_msg_union msg;
705 initTokenReqMsg(&msg.mu_TokenReq);
706 cpu_domsg(&msg);
707 }
708#endif
709 /*
710 * leave us in a critical section on return. This will be undone
711 * by lwkt_reltoken()
712 */
713}
714
715/*
716 * Release your ownership of a token. Releases must occur in reverse
717 * order to aquisitions, eventually so priorities can be unwound properly
718 * like SPLs. At the moment the actual implemention doesn't care.
719 *
720 * We can safely hand a token that we own to another cpu without notifying
721 * it, but once we do we can't get it back without requesting it (unless
722 * the other cpu hands it back to us before we check).
723 *
724 * We might have lost the token, so check that.
725 */
726void
727lwkt_reltoken(lwkt_token_t tok)
728{
729 if (tok->t_cpu == mycpu->gd_cpuid) {
730 tok->t_cpu = tok->t_reqcpu;
731 }
732 crit_exit();
733}
734
735/*
736 * Reaquire a token that might have been lost. Returns 1 if we blocked
737 * while reaquiring the token (meaning that you might have lost other
738 * tokens you held when you made this call), return 0 if we did not block.
739 */
740int
741lwkt_regettoken(lwkt_token_t tok)
742{
743#if 0
744 if (tok->t_cpu != mycpu->gd_cpuid) {
745 while (tok->t_cpu != mycpu->gd_cpuid) {
746 lwkt_cpu_msg_union msg;
747 initTokenReqMsg(&msg.mu_TokenReq);
748 cpu_domsg(&msg);
749 }
750 return(1);
751 }
752#endif
753 return(0);
754}
755
756/*
757 * Create a kernel process/thread/whatever. It shares it's address space
758 * with proc0 - ie: kernel only.
759 *
760 * XXX should be renamed to lwkt_create()
761 */
762int
763lwkt_create(void (*func)(void *), void *arg,
764 struct thread **tdp, struct thread *template, int tdflags,
765 const char *fmt, ...)
766{
767 struct thread *td;
768 va_list ap;
769
770 td = *tdp = lwkt_alloc_thread(template);
771 cpu_set_thread_handler(td, kthread_exit, func, arg);
772 td->td_flags |= TDF_VERBOSE | tdflags;
773
774 /*
775 * Set up arg0 for 'ps' etc
776 */
777 va_start(ap, fmt);
778 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
779 va_end(ap);
780
781 /*
782 * Schedule the thread to run
783 */
784 if ((td->td_flags & TDF_STOPREQ) == 0)
785 lwkt_schedule(td);
786 else
787 td->td_flags &= ~TDF_STOPREQ;
788 return 0;
789}
790
791/*
792 * Destroy an LWKT thread. Warning! This function is not called when
793 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
794 * uses a different reaping mechanism.
795 */
796void
797lwkt_exit(void)
798{
799 thread_t td = curthread;
800
801 if (td->td_flags & TDF_VERBOSE)
802 printf("kthread %p %s has exited\n", td, td->td_comm);
803 crit_enter();
804 lwkt_deschedule_self();
805 ++mycpu->gd_tdfreecount;
806 TAILQ_INSERT_TAIL(&mycpu->gd_tdfreeq, td, td_threadq);
807 cpu_thread_exit();
808}
809
810/*
811 * Create a kernel process/thread/whatever. It shares it's address space
812 * with proc0 - ie: kernel only. 5.x compatible.
813 */
814int
815kthread_create(void (*func)(void *), void *arg,
816 struct thread **tdp, const char *fmt, ...)
817{
818 struct thread *td;
819 va_list ap;
820
821 td = *tdp = lwkt_alloc_thread(NULL);
822 cpu_set_thread_handler(td, kthread_exit, func, arg);
823 td->td_flags |= TDF_VERBOSE;
824
825 /*
826 * Set up arg0 for 'ps' etc
827 */
828 va_start(ap, fmt);
829 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
830 va_end(ap);
831
832 /*
833 * Schedule the thread to run
834 */
835 lwkt_schedule(td);
836 return 0;
837}
838
839void
840crit_panic(void)
841{
842 struct thread *td = curthread;
843 int lpri = td->td_pri;
844
845 td->td_pri = 0;
846 panic("td_pri is/would-go negative! %p %d", td, lpri);
847}
848
849/*
850 * Destroy an LWKT thread. Warning! This function is not called when
851 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
852 * uses a different reaping mechanism.
853 *
854 * XXX duplicates lwkt_exit()
855 */
856void
857kthread_exit(void)
858{
859 lwkt_exit();
860}
861