Introduce globals: KvaStart, KvaEnd, and KvaSize. Used by the kernel
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
8c10bfcf
MD
2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
8ad65e08
MD
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
8c10bfcf 10 *
8ad65e08
MD
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
MD
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.
20 *
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.
8c10bfcf 33 *
6ea70f76 34 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.104 2006/12/23 00:35:04 swildner Exp $
75cdbe6c
MD
35 */
36
37/*
38 * Each cpu in a system has its own self-contained light weight kernel
39 * thread scheduler, which means that generally speaking we only need
40 * to use a critical section to avoid problems. Foreign thread
41 * scheduling is queued via (async) IPIs.
8ad65e08
MD
42 */
43
05220613
MD
44#ifdef _KERNEL
45
8ad65e08
MD
46#include <sys/param.h>
47#include <sys/systm.h>
48#include <sys/kernel.h>
49#include <sys/proc.h>
50#include <sys/rtprio.h>
51#include <sys/queue.h>
7d0bac62 52#include <sys/sysctl.h>
99df837e 53#include <sys/kthread.h>
f1d1c3fa 54#include <machine/cpu.h>
99df837e 55#include <sys/lock.h>
f6bf3af1 56#include <sys/caps.h>
9d265729 57#include <sys/spinlock.h>
57aa743c 58#include <sys/ktr.h>
9d265729
MD
59
60#include <sys/thread2.h>
61#include <sys/spinlock2.h>
f1d1c3fa 62
7d0bac62
MD
63#include <vm/vm.h>
64#include <vm/vm_param.h>
65#include <vm/vm_kern.h>
66#include <vm/vm_object.h>
67#include <vm/vm_page.h>
68#include <vm/vm_map.h>
69#include <vm/vm_pager.h>
70#include <vm/vm_extern.h>
71#include <vm/vm_zone.h>
72
99df837e 73#include <machine/stdarg.h>
96728c05 74#include <machine/smp.h>
99df837e 75
05220613
MD
76#else
77
78#include <sys/stdint.h>
fb04f4fd 79#include <libcaps/thread.h>
05220613
MD
80#include <sys/thread.h>
81#include <sys/msgport.h>
82#include <sys/errno.h>
fb04f4fd 83#include <libcaps/globaldata.h>
7e8303ad 84#include <machine/cpufunc.h>
05220613
MD
85#include <sys/thread2.h>
86#include <sys/msgport2.h>
709799ea 87#include <stdio.h>
05220613 88#include <stdlib.h>
709799ea 89#include <string.h>
709799ea 90#include <machine/lock.h>
b950d4b8
EN
91#include <machine/atomic.h>
92#include <machine/cpu.h>
05220613
MD
93
94#endif
95
7d0bac62 96static int untimely_switch = 0;
0f7a3396
MD
97#ifdef INVARIANTS
98static int panic_on_cscount = 0;
99#endif
05220613
MD
100static __int64_t switch_count = 0;
101static __int64_t preempt_hit = 0;
102static __int64_t preempt_miss = 0;
103static __int64_t preempt_weird = 0;
38717797
HP
104static __int64_t token_contention_count = 0;
105static __int64_t mplock_contention_count = 0;
05220613
MD
106
107#ifdef _KERNEL
108
109SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, "");
0f7a3396
MD
110#ifdef INVARIANTS
111SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, "");
112#endif
4b5f931b 113SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
4b5f931b 114SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, "");
4b5f931b 115SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, "");
26a0694b 116SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
38717797
HP
117#ifdef INVARIANTS
118SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW,
119 &token_contention_count, 0, "spinning due to token contention");
120SYSCTL_QUAD(_lwkt, OID_AUTO, mplock_contention_count, CTLFLAG_RW,
121 &mplock_contention_count, 0, "spinning due to MPLOCK contention");
122#endif
05220613
MD
123#endif
124
57aa743c
MD
125/*
126 * Kernel Trace
127 */
128#ifdef _KERNEL
129
130#if !defined(KTR_GIANT_CONTENTION)
131#define KTR_GIANT_CONTENTION KTR_ALL
132#endif
133
134KTR_INFO_MASTER(giant);
135KTR_INFO(KTR_GIANT_CONTENTION, giant, beg, 0, "thread=%p", sizeof(void *));
136KTR_INFO(KTR_GIANT_CONTENTION, giant, end, 1, "thread=%p", sizeof(void *));
137
138#define loggiant(name) KTR_LOG(giant_ ## name, curthread)
139
140#endif
141
4b5f931b
MD
142/*
143 * These helper procedures handle the runq, they can only be called from
144 * within a critical section.
75cdbe6c
MD
145 *
146 * WARNING! Prior to SMP being brought up it is possible to enqueue and
147 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
148 * instead of 'mycpu' when referencing the globaldata structure. Once
149 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 150 */
f1d1c3fa
MD
151static __inline
152void
153_lwkt_dequeue(thread_t td)
154{
155 if (td->td_flags & TDF_RUNQ) {
4b5f931b 156 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 157 struct globaldata *gd = td->td_gd;
4b5f931b 158
f1d1c3fa 159 td->td_flags &= ~TDF_RUNQ;
4b5f931b
MD
160 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq);
161 /* runqmask is passively cleaned up by the switcher */
f1d1c3fa
MD
162 }
163}
164
165static __inline
166void
167_lwkt_enqueue(thread_t td)
168{
344ad853 169 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_TSLEEPQ|TDF_BLOCKQ)) == 0) {
4b5f931b 170 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 171 struct globaldata *gd = td->td_gd;
4b5f931b 172
f1d1c3fa 173 td->td_flags |= TDF_RUNQ;
4b5f931b
MD
174 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq);
175 gd->gd_runqmask |= 1 << nq;
f1d1c3fa
MD
176 }
177}
8ad65e08 178
37af14fe
MD
179/*
180 * Schedule a thread to run. As the current thread we can always safely
181 * schedule ourselves, and a shortcut procedure is provided for that
182 * function.
183 *
184 * (non-blocking, self contained on a per cpu basis)
185 */
186void
187lwkt_schedule_self(thread_t td)
188{
189 crit_enter_quick(td);
37af14fe 190 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
344ad853 191 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
37af14fe 192 _lwkt_enqueue(td);
37af14fe
MD
193 crit_exit_quick(td);
194}
195
196/*
197 * Deschedule a thread.
198 *
199 * (non-blocking, self contained on a per cpu basis)
200 */
201void
202lwkt_deschedule_self(thread_t td)
203{
204 crit_enter_quick(td);
37af14fe
MD
205 _lwkt_dequeue(td);
206 crit_exit_quick(td);
207}
208
2d93b37a
MD
209#ifdef _KERNEL
210
8ad65e08
MD
211/*
212 * LWKTs operate on a per-cpu basis
213 *
73e4f7b9 214 * WARNING! Called from early boot, 'mycpu' may not work yet.
8ad65e08
MD
215 */
216void
217lwkt_gdinit(struct globaldata *gd)
218{
4b5f931b
MD
219 int i;
220
221 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
222 TAILQ_INIT(&gd->gd_tdrunq[i]);
223 gd->gd_runqmask = 0;
73e4f7b9 224 TAILQ_INIT(&gd->gd_tdallq);
8ad65e08
MD
225}
226
2d93b37a
MD
227#endif /* _KERNEL */
228
7d0bac62
MD
229/*
230 * Create a new thread. The thread must be associated with a process context
75cdbe6c
MD
231 * or LWKT start address before it can be scheduled. If the target cpu is
232 * -1 the thread will be created on the current cpu.
0cfcada1
MD
233 *
234 * If you intend to create a thread without a process context this function
235 * does everything except load the startup and switcher function.
7d0bac62
MD
236 */
237thread_t
d3d32139 238lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 239{
99df837e 240 void *stack;
37af14fe 241 globaldata_t gd = mycpu;
7d0bac62 242
ef0fdad1 243 if (td == NULL) {
37af14fe
MD
244 crit_enter_gd(gd);
245 if (gd->gd_tdfreecount > 0) {
246 --gd->gd_tdfreecount;
247 td = TAILQ_FIRST(&gd->gd_tdfreeq);
d9eea1a5 248 KASSERT(td != NULL && (td->td_flags & TDF_RUNNING) == 0,
ef0fdad1 249 ("lwkt_alloc_thread: unexpected NULL or corrupted td"));
37af14fe
MD
250 TAILQ_REMOVE(&gd->gd_tdfreeq, td, td_threadq);
251 crit_exit_gd(gd);
d3d32139 252 flags |= td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
ef0fdad1 253 } else {
37af14fe 254 crit_exit_gd(gd);
05220613 255#ifdef _KERNEL
ef0fdad1 256 td = zalloc(thread_zone);
05220613
MD
257#else
258 td = malloc(sizeof(struct thread));
259#endif
ef0fdad1 260 td->td_kstack = NULL;
f470d0c8 261 td->td_kstack_size = 0;
ef0fdad1
MD
262 flags |= TDF_ALLOCATED_THREAD;
263 }
264 }
f470d0c8
MD
265 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
266 if (flags & TDF_ALLOCATED_STACK) {
a9e5ae82 267#ifdef _KERNEL
f470d0c8 268 kmem_free(kernel_map, (vm_offset_t)stack, td->td_kstack_size);
a9e5ae82
JS
269#else
270 libcaps_free_stack(stack, td->td_kstack_size);
271#endif
f470d0c8
MD
272 stack = NULL;
273 }
274 }
275 if (stack == NULL) {
05220613 276#ifdef _KERNEL
f470d0c8 277 stack = (void *)kmem_alloc(kernel_map, stksize);
05220613 278#else
f470d0c8 279 stack = libcaps_alloc_stack(stksize);
05220613 280#endif
ef0fdad1 281 flags |= TDF_ALLOCATED_STACK;
99df837e 282 }
75cdbe6c 283 if (cpu < 0)
f470d0c8 284 lwkt_init_thread(td, stack, stksize, flags, mycpu);
75cdbe6c 285 else
f470d0c8 286 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 287 return(td);
7d0bac62
MD
288}
289
709799ea
MD
290#ifdef _KERNEL
291
7d0bac62
MD
292/*
293 * Initialize a preexisting thread structure. This function is used by
294 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
295 *
f8c3996b
MD
296 * All threads start out in a critical section at a priority of
297 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
MD
298 * appropriate. This function may send an IPI message when the
299 * requested cpu is not the current cpu and consequently gd_tdallq may
300 * not be initialized synchronously from the point of view of the originating
301 * cpu.
302 *
303 * NOTE! we have to be careful in regards to creating threads for other cpus
304 * if SMP has not yet been activated.
7d0bac62 305 */
41a01a4d
MD
306#ifdef SMP
307
75cdbe6c
MD
308static void
309lwkt_init_thread_remote(void *arg)
310{
311 thread_t td = arg;
312
52eedfb5
MD
313 /*
314 * Protected by critical section held by IPI dispatch
315 */
75cdbe6c
MD
316 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
317}
318
41a01a4d
MD
319#endif
320
7d0bac62 321void
f470d0c8
MD
322lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
323 struct globaldata *gd)
7d0bac62 324{
37af14fe
MD
325 globaldata_t mygd = mycpu;
326
99df837e
MD
327 bzero(td, sizeof(struct thread));
328 td->td_kstack = stack;
f470d0c8 329 td->td_kstack_size = stksize;
d3d32139 330 td->td_flags = flags;
26a0694b 331 td->td_gd = gd;
f8c3996b 332 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT;
d3d32139
MD
333#ifdef SMP
334 if ((flags & TDF_MPSAFE) == 0)
335 td->td_mpcount = 1;
336#endif
c95cd171 337 lwkt_initport(&td->td_msgport, td);
99df837e 338 pmap_init_thread(td);
0f7a3396 339#ifdef SMP
5d21b981
MD
340 /*
341 * Normally initializing a thread for a remote cpu requires sending an
342 * IPI. However, the idlethread is setup before the other cpus are
343 * activated so we have to treat it as a special case. XXX manipulation
344 * of gd_tdallq requires the BGL.
345 */
346 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 347 crit_enter_gd(mygd);
75cdbe6c 348 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 349 crit_exit_gd(mygd);
75cdbe6c 350 } else {
2db3b277 351 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 352 }
0f7a3396 353#else
37af14fe 354 crit_enter_gd(mygd);
0f7a3396 355 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 356 crit_exit_gd(mygd);
0f7a3396 357#endif
73e4f7b9
MD
358}
359
2d93b37a
MD
360#endif /* _KERNEL */
361
73e4f7b9
MD
362void
363lwkt_set_comm(thread_t td, const char *ctl, ...)
364{
e2565a42 365 __va_list va;
73e4f7b9 366
e2565a42 367 __va_start(va, ctl);
379210cb 368 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 369 __va_end(va);
7d0bac62
MD
370}
371
99df837e 372void
73e4f7b9 373lwkt_hold(thread_t td)
99df837e 374{
73e4f7b9
MD
375 ++td->td_refs;
376}
377
378void
379lwkt_rele(thread_t td)
380{
381 KKASSERT(td->td_refs > 0);
382 --td->td_refs;
383}
384
c95cd171
MD
385#ifdef _KERNEL
386
73e4f7b9
MD
387void
388lwkt_wait_free(thread_t td)
389{
390 while (td->td_refs)
377d4740 391 tsleep(td, 0, "tdreap", hz);
73e4f7b9
MD
392}
393
c95cd171
MD
394#endif
395
73e4f7b9
MD
396void
397lwkt_free_thread(thread_t td)
398{
399 struct globaldata *gd = mycpu;
400
d9eea1a5 401 KASSERT((td->td_flags & TDF_RUNNING) == 0,
99df837e
MD
402 ("lwkt_free_thread: did not exit! %p", td));
403
37af14fe 404 crit_enter_gd(gd);
73e4f7b9 405 if (gd->gd_tdfreecount < CACHE_NTHREADS &&
99df837e
MD
406 (td->td_flags & TDF_ALLOCATED_THREAD)
407 ) {
73e4f7b9
MD
408 ++gd->gd_tdfreecount;
409 TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq);
37af14fe 410 crit_exit_gd(gd);
99df837e 411 } else {
37af14fe 412 crit_exit_gd(gd);
99df837e 413 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
05220613 414#ifdef _KERNEL
f470d0c8 415 kmem_free(kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
05220613 416#else
f470d0c8 417 libcaps_free_stack(td->td_kstack, td->td_kstack_size);
05220613 418#endif
73e4f7b9 419 /* gd invalid */
99df837e 420 td->td_kstack = NULL;
f470d0c8 421 td->td_kstack_size = 0;
99df837e 422 }
05220613
MD
423 if (td->td_flags & TDF_ALLOCATED_THREAD) {
424#ifdef _KERNEL
99df837e 425 zfree(thread_zone, td);
05220613
MD
426#else
427 free(td);
428#endif
429 }
99df837e
MD
430 }
431}
432
433
8ad65e08
MD
434/*
435 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
436 * switch to the idlethread. Switching must occur within a critical
437 * section to avoid races with the scheduling queue.
438 *
439 * We always have full control over our cpu's run queue. Other cpus
440 * that wish to manipulate our queue must use the cpu_*msg() calls to
441 * talk to our cpu, so a critical section is all that is needed and
442 * the result is very, very fast thread switching.
443 *
96728c05
MD
444 * The LWKT scheduler uses a fixed priority model and round-robins at
445 * each priority level. User process scheduling is a totally
446 * different beast and LWKT priorities should not be confused with
447 * user process priorities.
f1d1c3fa 448 *
96728c05
MD
449 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch()
450 * cleans it up. Note that the td_switch() function cannot do anything that
451 * requires the MP lock since the MP lock will have already been setup for
71ef2f5c
MD
452 * the target thread (not the current thread). It's nice to have a scheduler
453 * that does not need the MP lock to work because it allows us to do some
454 * really cool high-performance MP lock optimizations.
69d78e99
MD
455 *
456 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
457 * is not called by the current thread in the preemption case, only when
458 * the preempting thread blocks (in order to return to the original thread).
8ad65e08
MD
459 */
460void
461lwkt_switch(void)
462{
37af14fe
MD
463 globaldata_t gd = mycpu;
464 thread_t td = gd->gd_curthread;
8ad65e08 465 thread_t ntd;
8a8d5d85
MD
466#ifdef SMP
467 int mpheld;
468#endif
8ad65e08 469
46a3f46d 470 /*
27e88a6e
MD
471 * Switching from within a 'fast' (non thread switched) interrupt or IPI
472 * is illegal. However, we may have to do it anyway if we hit a fatal
473 * kernel trap or we have paniced.
474 *
475 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 476 */
27e88a6e
MD
477 if (gd->gd_intr_nesting_level) {
478 int savegdnest;
479 int savegdtrap;
480
481 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) {
482 panic("lwkt_switch: cannot switch from within "
483 "a fast interrupt, yet, td %p\n", td);
484 } else {
485 savegdnest = gd->gd_intr_nesting_level;
486 savegdtrap = gd->gd_trap_nesting_level;
487 gd->gd_intr_nesting_level = 0;
488 gd->gd_trap_nesting_level = 0;
a7422615
MD
489 if ((td->td_flags & TDF_PANICWARN) == 0) {
490 td->td_flags |= TDF_PANICWARN;
6ea70f76 491 kprintf("Warning: thread switch from interrupt or IPI, "
a7422615
MD
492 "thread %p (%s)\n", td, td->td_comm);
493#ifdef DDB
494 db_print_backtrace();
495#endif
496 }
27e88a6e
MD
497 lwkt_switch();
498 gd->gd_intr_nesting_level = savegdnest;
499 gd->gd_trap_nesting_level = savegdtrap;
500 return;
501 }
96728c05 502 }
ef0fdad1 503
cb973d15
MD
504 /*
505 * Passive release (used to transition from user to kernel mode
506 * when we block or switch rather then when we enter the kernel).
507 * This function is NOT called if we are switching into a preemption
508 * or returning from a preemption. Typically this causes us to lose
0a3f9b47
MD
509 * our current process designation (if we have one) and become a true
510 * LWKT thread, and may also hand the current process designation to
511 * another process and schedule thread.
cb973d15
MD
512 */
513 if (td->td_release)
514 td->td_release(td);
515
37af14fe 516 crit_enter_gd(gd);
dd55d707 517#ifdef SMP
9d265729
MD
518 if (td->td_toks)
519 lwkt_relalltokens(td);
dd55d707 520#endif
9d265729
MD
521
522 /*
b02926de
MD
523 * We had better not be holding any spin locks, but don't get into an
524 * endless panic loop.
9d265729 525 */
bbb31c5d
MD
526 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL,
527 ("lwkt_switch: still holding a shared spinlock %p!",
528 gd->gd_spinlock_rd));
d666840a
MD
529 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
530 ("lwkt_switch: still holding %d exclusive spinlocks!",
531 gd->gd_spinlocks_wr));
9d265729 532
8a8d5d85
MD
533
534#ifdef SMP
535 /*
536 * td_mpcount cannot be used to determine if we currently hold the
537 * MP lock because get_mplock() will increment it prior to attempting
71ef2f5c
MD
538 * to get the lock, and switch out if it can't. Our ownership of
539 * the actual lock will remain stable while we are in a critical section
540 * (but, of course, another cpu may own or release the lock so the
541 * actual value of mp_lock is not stable).
8a8d5d85
MD
542 */
543 mpheld = MP_LOCK_HELD();
0f7a3396
MD
544#ifdef INVARIANTS
545 if (td->td_cscount) {
6ea70f76 546 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
547 td);
548 if (panic_on_cscount)
549 panic("switching while mastering cpusync");
550 }
551#endif
8a8d5d85 552#endif
99df837e
MD
553 if ((ntd = td->td_preempted) != NULL) {
554 /*
555 * We had preempted another thread on this cpu, resume the preempted
26a0694b
MD
556 * thread. This occurs transparently, whether the preempted thread
557 * was scheduled or not (it may have been preempted after descheduling
8a8d5d85
MD
558 * itself).
559 *
560 * We have to setup the MP lock for the original thread after backing
561 * out the adjustment that was made to curthread when the original
562 * was preempted.
99df837e 563 */
26a0694b 564 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
8a8d5d85 565#ifdef SMP
96728c05 566 if (ntd->td_mpcount && mpheld == 0) {
fc92d4aa 567 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d",
96728c05
MD
568 td, ntd, td->td_mpcount, ntd->td_mpcount);
569 }
8a8d5d85
MD
570 if (ntd->td_mpcount) {
571 td->td_mpcount -= ntd->td_mpcount;
572 KKASSERT(td->td_mpcount >= 0);
573 }
574#endif
26a0694b 575 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
576
577 /*
578 * XXX. The interrupt may have woken a thread up, we need to properly
579 * set the reschedule flag if the originally interrupted thread is at
580 * a lower priority.
581 */
582 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1)
583 need_lwkt_resched();
8a8d5d85 584 /* YYY release mp lock on switchback if original doesn't need it */
8ad65e08 585 } else {
4b5f931b
MD
586 /*
587 * Priority queue / round-robin at each priority. Note that user
588 * processes run at a fixed, low priority and the user process
589 * scheduler deals with interactions between user processes
590 * by scheduling and descheduling them from the LWKT queue as
591 * necessary.
8a8d5d85
MD
592 *
593 * We have to adjust the MP lock for the target thread. If we
594 * need the MP lock and cannot obtain it we try to locate a
41a01a4d
MD
595 * thread that does not need the MP lock. If we cannot, we spin
596 * instead of HLT.
597 *
598 * A similar issue exists for the tokens held by the target thread.
599 * If we cannot obtain ownership of the tokens we cannot immediately
600 * schedule the thread.
601 */
602
8ec60c3f
MD
603 /*
604 * If an LWKT reschedule was requested, well that is what we are
605 * doing now so clear it.
606 */
607 clear_lwkt_resched();
4b5f931b
MD
608again:
609 if (gd->gd_runqmask) {
610 int nq = bsrl(gd->gd_runqmask);
611 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
612 gd->gd_runqmask &= ~(1 << nq);
613 goto again;
614 }
8a8d5d85 615#ifdef SMP
41a01a4d 616 /*
df6b8ba0
MD
617 * THREAD SELECTION FOR AN SMP MACHINE BUILD
618 *
41a01a4d
MD
619 * If the target needs the MP lock and we couldn't get it,
620 * or if the target is holding tokens and we could not
621 * gain ownership of the tokens, continue looking for a
622 * thread to schedule and spin instead of HLT if we can't.
a453459d
MD
623 *
624 * NOTE: the mpheld variable invalid after this conditional, it
625 * can change due to both cpu_try_mplock() returning success
9d265729 626 * AND interactions in lwkt_getalltokens() due to the fact that
a453459d
MD
627 * we are trying to check the mpcount of a thread other then
628 * the current thread. Because of this, if the current thread
629 * is not holding td_mpcount, an IPI indirectly run via
9d265729 630 * lwkt_getalltokens() can obtain and release the MP lock and
a453459d 631 * cause the core MP lock to be released.
41a01a4d
MD
632 */
633 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) ||
9d265729 634 (ntd->td_toks && lwkt_getalltokens(ntd) == 0)
41a01a4d 635 ) {
8a8d5d85 636 u_int32_t rqmask = gd->gd_runqmask;
a453459d
MD
637
638 mpheld = MP_LOCK_HELD();
639 ntd = NULL;
8a8d5d85
MD
640 while (rqmask) {
641 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) {
38717797 642 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) {
a453459d 643 /* spinning due to MP lock being held */
38717797 644#ifdef INVARIANTS
a453459d 645 ++mplock_contention_count;
38717797 646#endif
a453459d 647 /* mplock still not held, 'mpheld' still valid */
41a01a4d 648 continue;
38717797 649 }
a453459d
MD
650
651 /*
9d265729 652 * mpheld state invalid after getalltokens call returns
a453459d
MD
653 * failure, but the variable is only needed for
654 * the loop.
655 */
9d265729 656 if (ntd->td_toks && !lwkt_getalltokens(ntd)) {
a453459d 657 /* spinning due to token contention */
38717797 658#ifdef INVARIANTS
a453459d 659 ++token_contention_count;
38717797 660#endif
a453459d 661 mpheld = MP_LOCK_HELD();
41a01a4d 662 continue;
38717797 663 }
41a01a4d 664 break;
8a8d5d85
MD
665 }
666 if (ntd)
667 break;
668 rqmask &= ~(1 << nq);
669 nq = bsrl(rqmask);
670 }
671 if (ntd == NULL) {
a2a5ad0d
MD
672 ntd = &gd->gd_idlethread;
673 ntd->td_flags |= TDF_IDLE_NOHLT;
df6b8ba0 674 goto using_idle_thread;
8a8d5d85 675 } else {
344ad853 676 ++gd->gd_cnt.v_swtch;
8a8d5d85
MD
677 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
678 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
679 }
680 } else {
344ad853 681 ++gd->gd_cnt.v_swtch;
8a8d5d85
MD
682 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
683 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
684 }
685#else
df6b8ba0
MD
686 /*
687 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to
688 * worry about tokens or the BGL.
689 */
344ad853 690 ++gd->gd_cnt.v_swtch;
4b5f931b
MD
691 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
692 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
8a8d5d85 693#endif
4b5f931b 694 } else {
3c23a41a 695 /*
60f945af
MD
696 * We have nothing to run but only let the idle loop halt
697 * the cpu if there are no pending interrupts.
3c23a41a 698 */
a2a5ad0d 699 ntd = &gd->gd_idlethread;
60f945af 700 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
3c23a41a 701 ntd->td_flags |= TDF_IDLE_NOHLT;
a453459d 702#ifdef SMP
df6b8ba0
MD
703using_idle_thread:
704 /*
705 * The idle thread should not be holding the MP lock unless we
706 * are trapping in the kernel or in a panic. Since we select the
707 * idle thread unconditionally when no other thread is available,
708 * if the MP lock is desired during a panic or kernel trap, we
709 * have to loop in the scheduler until we get it.
710 */
711 if (ntd->td_mpcount) {
712 mpheld = MP_LOCK_HELD();
713 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
714 panic("Idle thread %p was holding the BGL!", ntd);
715 else if (mpheld == 0)
716 goto again;
717 }
a453459d 718#endif
4b5f931b 719 }
f1d1c3fa 720 }
26a0694b
MD
721 KASSERT(ntd->td_pri >= TDPRI_CRIT,
722 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
8a8d5d85
MD
723
724 /*
725 * Do the actual switch. If the new target does not need the MP lock
726 * and we are holding it, release the MP lock. If the new target requires
727 * the MP lock we have already acquired it for the target.
728 */
729#ifdef SMP
730 if (ntd->td_mpcount == 0 ) {
731 if (MP_LOCK_HELD())
732 cpu_rel_mplock();
733 } else {
a453459d 734 ASSERT_MP_LOCK_HELD(ntd);
8a8d5d85
MD
735 }
736#endif
94f6d86e
MD
737 if (td != ntd) {
738 ++switch_count;
f1d1c3fa 739 td->td_switch(ntd);
94f6d86e 740 }
37af14fe
MD
741 /* NOTE: current cpu may have changed after switch */
742 crit_exit_quick(td);
8ad65e08
MD
743}
744
b68b7282 745/*
96728c05
MD
746 * Request that the target thread preempt the current thread. Preemption
747 * only works under a specific set of conditions:
b68b7282 748 *
96728c05
MD
749 * - We are not preempting ourselves
750 * - The target thread is owned by the current cpu
751 * - We are not currently being preempted
752 * - The target is not currently being preempted
753 * - We are able to satisfy the target's MP lock requirements (if any).
754 *
755 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
756 * this is called via lwkt_schedule() through the td_preemptable callback.
757 * critpri is the managed critical priority that we should ignore in order
758 * to determine whether preemption is possible (aka usually just the crit
759 * priority of lwkt_schedule() itself).
b68b7282 760 *
26a0694b
MD
761 * XXX at the moment we run the target thread in a critical section during
762 * the preemption in order to prevent the target from taking interrupts
763 * that *WE* can't. Preemption is strictly limited to interrupt threads
764 * and interrupt-like threads, outside of a critical section, and the
765 * preempted source thread will be resumed the instant the target blocks
766 * whether or not the source is scheduled (i.e. preemption is supposed to
767 * be as transparent as possible).
4b5f931b 768 *
8a8d5d85
MD
769 * The target thread inherits our MP count (added to its own) for the
770 * duration of the preemption in order to preserve the atomicy of the
96728c05
MD
771 * MP lock during the preemption. Therefore, any preempting targets must be
772 * careful in regards to MP assertions. Note that the MP count may be
71ef2f5c
MD
773 * out of sync with the physical mp_lock, but we do not have to preserve
774 * the original ownership of the lock if it was out of synch (that is, we
775 * can leave it synchronized on return).
b68b7282
MD
776 */
777void
96728c05 778lwkt_preempt(thread_t ntd, int critpri)
b68b7282 779{
46a3f46d 780 struct globaldata *gd = mycpu;
0a3f9b47 781 thread_t td;
8a8d5d85
MD
782#ifdef SMP
783 int mpheld;
57c254db 784 int savecnt;
8a8d5d85 785#endif
b68b7282 786
26a0694b 787 /*
96728c05
MD
788 * The caller has put us in a critical section. We can only preempt
789 * if the caller of the caller was not in a critical section (basically
d666840a
MD
790 * a local interrupt), as determined by the 'critpri' parameter. We
791 * also acn't preempt if the caller is holding any spinlocks (even if
792 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
793 *
794 * YYY The target thread must be in a critical section (else it must
795 * inherit our critical section? I dunno yet).
41a01a4d 796 *
0a3f9b47 797 * Set need_lwkt_resched() unconditionally for now YYY.
26a0694b
MD
798 */
799 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 800
0a3f9b47 801 td = gd->gd_curthread;
0a3f9b47 802 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) {
57c254db
MD
803 ++preempt_miss;
804 return;
805 }
96728c05
MD
806 if ((td->td_pri & ~TDPRI_MASK) > critpri) {
807 ++preempt_miss;
8ec60c3f 808 need_lwkt_resched();
96728c05
MD
809 return;
810 }
811#ifdef SMP
46a3f46d 812 if (ntd->td_gd != gd) {
96728c05 813 ++preempt_miss;
8ec60c3f 814 need_lwkt_resched();
96728c05
MD
815 return;
816 }
817#endif
41a01a4d
MD
818 /*
819 * Take the easy way out and do not preempt if the target is holding
d666840a 820 * any spinlocks. We could test whether the thread(s) being
41a01a4d
MD
821 * preempted interlock against the target thread's tokens and whether
822 * we can get all the target thread's tokens, but this situation
823 * should not occur very often so its easier to simply not preempt.
d666840a
MD
824 * Also, plain spinlocks are impossible to figure out at this point so
825 * just don't preempt.
41a01a4d 826 */
bbb31c5d 827 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) {
41a01a4d 828 ++preempt_miss;
8ec60c3f 829 need_lwkt_resched();
41a01a4d
MD
830 return;
831 }
26a0694b
MD
832 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
833 ++preempt_weird;
8ec60c3f 834 need_lwkt_resched();
26a0694b
MD
835 return;
836 }
837 if (ntd->td_preempted) {
4b5f931b 838 ++preempt_hit;
8ec60c3f 839 need_lwkt_resched();
26a0694b 840 return;
b68b7282 841 }
8a8d5d85 842#ifdef SMP
a2a5ad0d
MD
843 /*
844 * note: an interrupt might have occured just as we were transitioning
71ef2f5c
MD
845 * to or from the MP lock. In this case td_mpcount will be pre-disposed
846 * (non-zero) but not actually synchronized with the actual state of the
847 * lock. We can use it to imply an MP lock requirement for the
848 * preemption but we cannot use it to test whether we hold the MP lock
849 * or not.
a2a5ad0d 850 */
96728c05 851 savecnt = td->td_mpcount;
71ef2f5c 852 mpheld = MP_LOCK_HELD();
8a8d5d85
MD
853 ntd->td_mpcount += td->td_mpcount;
854 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) {
855 ntd->td_mpcount -= td->td_mpcount;
856 ++preempt_miss;
8ec60c3f 857 need_lwkt_resched();
8a8d5d85
MD
858 return;
859 }
860#endif
26a0694b 861
8ec60c3f
MD
862 /*
863 * Since we are able to preempt the current thread, there is no need to
864 * call need_lwkt_resched().
865 */
26a0694b
MD
866 ++preempt_hit;
867 ntd->td_preempted = td;
868 td->td_flags |= TDF_PREEMPT_LOCK;
869 td->td_switch(ntd);
870 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
96728c05
MD
871#ifdef SMP
872 KKASSERT(savecnt == td->td_mpcount);
71ef2f5c
MD
873 mpheld = MP_LOCK_HELD();
874 if (mpheld && td->td_mpcount == 0)
96728c05 875 cpu_rel_mplock();
71ef2f5c 876 else if (mpheld == 0 && td->td_mpcount)
96728c05
MD
877 panic("lwkt_preempt(): MP lock was not held through");
878#endif
26a0694b
MD
879 ntd->td_preempted = NULL;
880 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
881}
882
f1d1c3fa
MD
883/*
884 * Yield our thread while higher priority threads are pending. This is
885 * typically called when we leave a critical section but it can be safely
886 * called while we are in a critical section.
887 *
888 * This function will not generally yield to equal priority threads but it
889 * can occur as a side effect. Note that lwkt_switch() is called from
46a3f46d 890 * inside the critical section to prevent its own crit_exit() from reentering
f1d1c3fa
MD
891 * lwkt_yield_quick().
892 *
235957ed 893 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint
ef0fdad1
MD
894 * came along but was blocked and made pending.
895 *
f1d1c3fa
MD
896 * (self contained on a per cpu basis)
897 */
898void
899lwkt_yield_quick(void)
900{
7966cb69
MD
901 globaldata_t gd = mycpu;
902 thread_t td = gd->gd_curthread;
ef0fdad1 903
a2a5ad0d 904 /*
235957ed 905 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear
a2a5ad0d
MD
906 * it with a non-zero cpl then we might not wind up calling splz after
907 * a task switch when the critical section is exited even though the
46a3f46d 908 * new task could accept the interrupt.
a2a5ad0d
MD
909 *
910 * XXX from crit_exit() only called after last crit section is released.
911 * If called directly will run splz() even if in a critical section.
46a3f46d
MD
912 *
913 * td_nest_count prevent deep nesting via splz() or doreti(). Note that
914 * except for this special case, we MUST call splz() here to handle any
915 * pending ints, particularly after we switch, or we might accidently
916 * halt the cpu with interrupts pending.
a2a5ad0d 917 */
46a3f46d 918 if (gd->gd_reqflags && td->td_nest_count < 2)
f1d1c3fa 919 splz();
f1d1c3fa
MD
920
921 /*
922 * YYY enabling will cause wakeup() to task-switch, which really
923 * confused the old 4.x code. This is a good way to simulate
7d0bac62
MD
924 * preemption and MP without actually doing preemption or MP, because a
925 * lot of code assumes that wakeup() does not block.
f1d1c3fa 926 */
46a3f46d
MD
927 if (untimely_switch && td->td_nest_count == 0 &&
928 gd->gd_intr_nesting_level == 0
929 ) {
37af14fe 930 crit_enter_quick(td);
f1d1c3fa
MD
931 /*
932 * YYY temporary hacks until we disassociate the userland scheduler
933 * from the LWKT scheduler.
934 */
935 if (td->td_flags & TDF_RUNQ) {
936 lwkt_switch(); /* will not reenter yield function */
937 } else {
37af14fe 938 lwkt_schedule_self(td); /* make sure we are scheduled */
f1d1c3fa 939 lwkt_switch(); /* will not reenter yield function */
37af14fe 940 lwkt_deschedule_self(td); /* make sure we are descheduled */
f1d1c3fa 941 }
7966cb69 942 crit_exit_noyield(td);
f1d1c3fa 943 }
f1d1c3fa
MD
944}
945
8ad65e08 946/*
f1d1c3fa 947 * This implements a normal yield which, unlike _quick, will yield to equal
235957ed 948 * priority threads as well. Note that gd_reqflags tests will be handled by
f1d1c3fa
MD
949 * the crit_exit() call in lwkt_switch().
950 *
951 * (self contained on a per cpu basis)
8ad65e08
MD
952 */
953void
f1d1c3fa 954lwkt_yield(void)
8ad65e08 955{
37af14fe 956 lwkt_schedule_self(curthread);
f1d1c3fa
MD
957 lwkt_switch();
958}
959
8ad65e08 960/*
f1d1c3fa
MD
961 * Generic schedule. Possibly schedule threads belonging to other cpus and
962 * deal with threads that might be blocked on a wait queue.
963 *
0a3f9b47
MD
964 * We have a little helper inline function which does additional work after
965 * the thread has been enqueued, including dealing with preemption and
966 * setting need_lwkt_resched() (which prevents the kernel from returning
967 * to userland until it has processed higher priority threads).
6330a558
MD
968 *
969 * It is possible for this routine to be called after a failed _enqueue
970 * (due to the target thread migrating, sleeping, or otherwise blocked).
971 * We have to check that the thread is actually on the run queue!
8ad65e08 972 */
0a3f9b47
MD
973static __inline
974void
8ec60c3f 975_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri)
0a3f9b47 976{
6330a558
MD
977 if (ntd->td_flags & TDF_RUNQ) {
978 if (ntd->td_preemptable) {
979 ntd->td_preemptable(ntd, cpri); /* YYY +token */
980 } else if ((ntd->td_flags & TDF_NORESCHED) == 0 &&
981 (ntd->td_pri & TDPRI_MASK) > (gd->gd_curthread->td_pri & TDPRI_MASK)
982 ) {
983 need_lwkt_resched();
984 }
0a3f9b47
MD
985 }
986}
987
8ad65e08
MD
988void
989lwkt_schedule(thread_t td)
990{
37af14fe
MD
991 globaldata_t mygd = mycpu;
992
41a01a4d 993 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
37af14fe 994 crit_enter_gd(mygd);
344ad853 995 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
37af14fe 996 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
997 _lwkt_enqueue(td);
998 } else {
f1d1c3fa 999 /*
7cd8d145
MD
1000 * If we own the thread, there is no race (since we are in a
1001 * critical section). If we do not own the thread there might
1002 * be a race but the target cpu will deal with it.
f1d1c3fa 1003 */
0f7a3396 1004#ifdef SMP
7cd8d145 1005 if (td->td_gd == mygd) {
9d265729
MD
1006 _lwkt_enqueue(td);
1007 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
f1d1c3fa 1008 } else {
7cd8d145
MD
1009 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
1010 }
0f7a3396 1011#else
7cd8d145
MD
1012 _lwkt_enqueue(td);
1013 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
0f7a3396 1014#endif
8ad65e08 1015 }
37af14fe 1016 crit_exit_gd(mygd);
8ad65e08
MD
1017}
1018
52eedfb5
MD
1019#ifdef SMP
1020
d9eea1a5 1021/*
52eedfb5
MD
1022 * Thread migration using a 'Pull' method. The thread may or may not be
1023 * the current thread. It MUST be descheduled and in a stable state.
1024 * lwkt_giveaway() must be called on the cpu owning the thread.
1025 *
1026 * At any point after lwkt_giveaway() is called, the target cpu may
1027 * 'pull' the thread by calling lwkt_acquire().
1028 *
1029 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1030 */
52eedfb5
MD
1031void
1032lwkt_giveaway(thread_t td)
1033{
1034 globaldata_t gd = mycpu;
1035
1036 crit_enter_gd(gd);
1037 KKASSERT(td->td_gd == gd);
1038 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1039 td->td_flags |= TDF_MIGRATING;
1040 crit_exit_gd(gd);
1041}
1042
a2a5ad0d
MD
1043void
1044lwkt_acquire(thread_t td)
1045{
37af14fe
MD
1046 globaldata_t gd;
1047 globaldata_t mygd;
a2a5ad0d 1048
52eedfb5 1049 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1050 gd = td->td_gd;
37af14fe 1051 mygd = mycpu;
52eedfb5 1052 if (gd != mycpu) {
35238fa5 1053 cpu_lfence();
52eedfb5 1054 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1055 crit_enter_gd(mygd);
52eedfb5
MD
1056 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK))
1057 cpu_lfence();
37af14fe 1058 td->td_gd = mygd;
52eedfb5
MD
1059 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1060 td->td_flags &= ~TDF_MIGRATING;
1061 crit_exit_gd(mygd);
1062 } else {
1063 crit_enter_gd(mygd);
1064 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1065 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1066 crit_exit_gd(mygd);
a2a5ad0d
MD
1067 }
1068}
1069
52eedfb5
MD
1070#endif
1071
f1d1c3fa
MD
1072/*
1073 * Generic deschedule. Descheduling threads other then your own should be
1074 * done only in carefully controlled circumstances. Descheduling is
1075 * asynchronous.
1076 *
1077 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1078 */
1079void
1080lwkt_deschedule(thread_t td)
1081{
f1d1c3fa 1082 crit_enter();
b8a98473 1083#ifdef SMP
f1d1c3fa
MD
1084 if (td == curthread) {
1085 _lwkt_dequeue(td);
1086 } else {
a72187e9 1087 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1088 _lwkt_dequeue(td);
1089 } else {
b8a98473 1090 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1091 }
1092 }
b8a98473
MD
1093#else
1094 _lwkt_dequeue(td);
1095#endif
f1d1c3fa
MD
1096 crit_exit();
1097}
1098
4b5f931b
MD
1099/*
1100 * Set the target thread's priority. This routine does not automatically
1101 * switch to a higher priority thread, LWKT threads are not designed for
1102 * continuous priority changes. Yield if you want to switch.
1103 *
1104 * We have to retain the critical section count which uses the high bits
26a0694b
MD
1105 * of the td_pri field. The specified priority may also indicate zero or
1106 * more critical sections by adding TDPRI_CRIT*N.
18bbe476
MD
1107 *
1108 * Note that we requeue the thread whether it winds up on a different runq
1109 * or not. uio_yield() depends on this and the routine is not normally
1110 * called with the same priority otherwise.
4b5f931b
MD
1111 */
1112void
1113lwkt_setpri(thread_t td, int pri)
1114{
26a0694b 1115 KKASSERT(pri >= 0);
a72187e9 1116 KKASSERT(td->td_gd == mycpu);
26a0694b
MD
1117 crit_enter();
1118 if (td->td_flags & TDF_RUNQ) {
1119 _lwkt_dequeue(td);
1120 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1121 _lwkt_enqueue(td);
1122 } else {
1123 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1124 }
1125 crit_exit();
1126}
1127
1128void
1129lwkt_setpri_self(int pri)
1130{
1131 thread_t td = curthread;
1132
4b5f931b
MD
1133 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1134 crit_enter();
1135 if (td->td_flags & TDF_RUNQ) {
1136 _lwkt_dequeue(td);
1137 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1138 _lwkt_enqueue(td);
1139 } else {
1140 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1141 }
1142 crit_exit();
1143}
1144
8ec60c3f
MD
1145/*
1146 * Determine if there is a runnable thread at a higher priority then
1147 * the current thread. lwkt_setpri() does not check this automatically.
1148 * Return 1 if there is, 0 if there isn't.
1149 *
1150 * Example: if bit 31 of runqmask is set and the current thread is priority
1151 * 30, then we wind up checking the mask: 0x80000000 against 0x7fffffff.
1152 *
1153 * If nq reaches 31 the shift operation will overflow to 0 and we will wind
1154 * up comparing against 0xffffffff, a comparison that will always be false.
1155 */
1156int
1157lwkt_checkpri_self(void)
1158{
1159 globaldata_t gd = mycpu;
1160 thread_t td = gd->gd_curthread;
1161 int nq = td->td_pri & TDPRI_MASK;
1162
1163 while (gd->gd_runqmask > (__uint32_t)(2 << nq) - 1) {
1164 if (TAILQ_FIRST(&gd->gd_tdrunq[nq + 1]))
1165 return(1);
1166 ++nq;
1167 }
1168 return(0);
1169}
1170
5d21b981 1171/*
52eedfb5
MD
1172 * Migrate the current thread to the specified cpu.
1173 *
1174 * This is accomplished by descheduling ourselves from the current cpu,
1175 * moving our thread to the tdallq of the target cpu, IPI messaging the
1176 * target cpu, and switching out. TDF_MIGRATING prevents scheduling
1177 * races while the thread is being migrated.
5d21b981 1178 */
3d28ff59 1179#ifdef SMP
5d21b981 1180static void lwkt_setcpu_remote(void *arg);
3d28ff59 1181#endif
5d21b981
MD
1182
1183void
1184lwkt_setcpu_self(globaldata_t rgd)
1185{
1186#ifdef SMP
1187 thread_t td = curthread;
1188
1189 if (td->td_gd != rgd) {
1190 crit_enter_quick(td);
1191 td->td_flags |= TDF_MIGRATING;
1192 lwkt_deschedule_self(td);
52eedfb5 1193 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
b8a98473 1194 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td);
5d21b981
MD
1195 lwkt_switch();
1196 /* we are now on the target cpu */
52eedfb5 1197 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1198 crit_exit_quick(td);
1199 }
1200#endif
1201}
1202
ecdefdda
MD
1203void
1204lwkt_migratecpu(int cpuid)
1205{
1206#ifdef SMP
1207 globaldata_t rgd;
1208
1209 rgd = globaldata_find(cpuid);
1210 lwkt_setcpu_self(rgd);
1211#endif
1212}
1213
5d21b981
MD
1214/*
1215 * Remote IPI for cpu migration (called while in a critical section so we
1216 * do not have to enter another one). The thread has already been moved to
1217 * our cpu's allq, but we must wait for the thread to be completely switched
1218 * out on the originating cpu before we schedule it on ours or the stack
1219 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD
1220 * change to main memory.
1221 *
1222 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races
1223 * against wakeups. It is best if this interface is used only when there
1224 * are no pending events that might try to schedule the thread.
1225 */
3d28ff59 1226#ifdef SMP
5d21b981
MD
1227static void
1228lwkt_setcpu_remote(void *arg)
1229{
1230 thread_t td = arg;
1231 globaldata_t gd = mycpu;
1232
c1102e9f 1233 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK))
35238fa5 1234 cpu_lfence();
5d21b981 1235 td->td_gd = gd;
35238fa5 1236 cpu_sfence();
5d21b981 1237 td->td_flags &= ~TDF_MIGRATING;
344ad853 1238 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
5d21b981
MD
1239 _lwkt_enqueue(td);
1240}
3d28ff59 1241#endif
5d21b981 1242
553ea3c8 1243struct lwp *
4b5f931b
MD
1244lwkt_preempted_proc(void)
1245{
73e4f7b9 1246 thread_t td = curthread;
4b5f931b
MD
1247 while (td->td_preempted)
1248 td = td->td_preempted;
553ea3c8 1249 return(td->td_lwp);
4b5f931b
MD
1250}
1251
99df837e
MD
1252/*
1253 * Create a kernel process/thread/whatever. It shares it's address space
1254 * with proc0 - ie: kernel only.
1255 *
365fa13f
MD
1256 * NOTE! By default new threads are created with the MP lock held. A
1257 * thread which does not require the MP lock should release it by calling
1258 * rel_mplock() at the start of the new thread.
99df837e
MD
1259 */
1260int
1261lwkt_create(void (*func)(void *), void *arg,
75cdbe6c 1262 struct thread **tdp, thread_t template, int tdflags, int cpu,
ef0fdad1 1263 const char *fmt, ...)
99df837e 1264{
73e4f7b9 1265 thread_t td;
e2565a42 1266 __va_list ap;
99df837e 1267
d3d32139
MD
1268 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
1269 tdflags | TDF_VERBOSE);
a2a5ad0d
MD
1270 if (tdp)
1271 *tdp = td;
709799ea 1272 cpu_set_thread_handler(td, lwkt_exit, func, arg);
99df837e
MD
1273
1274 /*
1275 * Set up arg0 for 'ps' etc
1276 */
e2565a42 1277 __va_start(ap, fmt);
379210cb 1278 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1279 __va_end(ap);
99df837e
MD
1280
1281 /*
1282 * Schedule the thread to run
1283 */
ef0fdad1
MD
1284 if ((td->td_flags & TDF_STOPREQ) == 0)
1285 lwkt_schedule(td);
1286 else
1287 td->td_flags &= ~TDF_STOPREQ;
99df837e
MD
1288 return 0;
1289}
1290
2d93b37a 1291/*
2d93b37a
MD
1292 * kthread_* is specific to the kernel and is not needed by userland.
1293 */
1294#ifdef _KERNEL
1295
99df837e
MD
1296/*
1297 * Destroy an LWKT thread. Warning! This function is not called when
1298 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1299 * uses a different reaping mechanism.
1300 */
1301void
1302lwkt_exit(void)
1303{
1304 thread_t td = curthread;
8826f33a 1305 globaldata_t gd;
99df837e
MD
1306
1307 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1308 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1309 caps_exit(td);
37af14fe
MD
1310 crit_enter_quick(td);
1311 lwkt_deschedule_self(td);
8826f33a 1312 gd = mycpu;
e56e4dea 1313 lwkt_remove_tdallq(td);
8826f33a
MD
1314 if (td->td_flags & TDF_ALLOCATED_THREAD) {
1315 ++gd->gd_tdfreecount;
1316 TAILQ_INSERT_TAIL(&gd->gd_tdfreeq, td, td_threadq);
1317 }
99df837e
MD
1318 cpu_thread_exit();
1319}
1320
e56e4dea
MD
1321void
1322lwkt_remove_tdallq(thread_t td)
1323{
1324 KKASSERT(td->td_gd == mycpu);
1325 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1326}
1327
2d93b37a
MD
1328#endif /* _KERNEL */
1329
1330void
1331crit_panic(void)
1332{
1333 thread_t td = curthread;
1334 int lpri = td->td_pri;
1335
1336 td->td_pri = 0;
1337 panic("td_pri is/would-go negative! %p %d", td, lpri);
1338}
1339
d165e668
MD
1340#ifdef SMP
1341
bd8015ca
MD
1342/*
1343 * Called from debugger/panic on cpus which have been stopped. We must still
1344 * process the IPIQ while stopped, even if we were stopped while in a critical
1345 * section (XXX).
1346 *
1347 * If we are dumping also try to process any pending interrupts. This may
1348 * or may not work depending on the state of the cpu at the point it was
1349 * stopped.
1350 */
1351void
1352lwkt_smp_stopped(void)
1353{
1354 globaldata_t gd = mycpu;
1355
1356 crit_enter_gd(gd);
1357 if (dumping) {
1358 lwkt_process_ipiq();
1359 splz();
1360 } else {
1361 lwkt_process_ipiq();
1362 }
1363 crit_exit_gd(gd);
1364}
1365
57aa743c
MD
1366/*
1367 * get_mplock() calls this routine if it is unable to obtain the MP lock.
1368 * get_mplock() has already incremented td_mpcount. We must block and
1369 * not return until giant is held.
1370 *
1371 * All we have to do is lwkt_switch() away. The LWKT scheduler will not
1372 * reschedule the thread until it can obtain the giant lock for it.
1373 */
1374void
1375lwkt_mp_lock_contested(void)
1376{
1377#ifdef _KERNEL
1378 loggiant(beg);
1379#endif
1380 lwkt_switch();
1381#ifdef _KERNEL
1382 loggiant(end);
1383#endif
1384}
1385
d165e668 1386#endif