Make tsleep/wakeup MP SAFE part 1/2.
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
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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 *
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7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
8c10bfcf 10 *
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11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
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14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
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 *
b8a98473 34 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.84 2005/10/25 17:26:54 dillon Exp $
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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.
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42 */
43
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44#ifdef _KERNEL
45
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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>
f1d1c3fa 52#include <sys/thread2.h>
7d0bac62 53#include <sys/sysctl.h>
99df837e 54#include <sys/kthread.h>
f1d1c3fa 55#include <machine/cpu.h>
99df837e 56#include <sys/lock.h>
f6bf3af1 57#include <sys/caps.h>
f1d1c3fa 58
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59#include <vm/vm.h>
60#include <vm/vm_param.h>
61#include <vm/vm_kern.h>
62#include <vm/vm_object.h>
63#include <vm/vm_page.h>
64#include <vm/vm_map.h>
65#include <vm/vm_pager.h>
66#include <vm/vm_extern.h>
67#include <vm/vm_zone.h>
68
99df837e 69#include <machine/stdarg.h>
57c254db 70#include <machine/ipl.h>
96728c05 71#include <machine/smp.h>
99df837e 72
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73#else
74
75#include <sys/stdint.h>
fb04f4fd 76#include <libcaps/thread.h>
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77#include <sys/thread.h>
78#include <sys/msgport.h>
79#include <sys/errno.h>
fb04f4fd 80#include <libcaps/globaldata.h>
7e8303ad 81#include <machine/cpufunc.h>
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82#include <sys/thread2.h>
83#include <sys/msgport2.h>
709799ea 84#include <stdio.h>
05220613 85#include <stdlib.h>
709799ea 86#include <string.h>
709799ea 87#include <machine/lock.h>
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88#include <machine/atomic.h>
89#include <machine/cpu.h>
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90
91#endif
92
7d0bac62 93static int untimely_switch = 0;
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94#ifdef INVARIANTS
95static int panic_on_cscount = 0;
96#endif
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97static __int64_t switch_count = 0;
98static __int64_t preempt_hit = 0;
99static __int64_t preempt_miss = 0;
100static __int64_t preempt_weird = 0;
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101static __int64_t token_contention_count = 0;
102static __int64_t mplock_contention_count = 0;
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103
104#ifdef _KERNEL
105
106SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, "");
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107#ifdef INVARIANTS
108SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, "");
109#endif
4b5f931b 110SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
4b5f931b 111SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, "");
4b5f931b 112SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, "");
26a0694b 113SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
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114#ifdef INVARIANTS
115SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW,
116 &token_contention_count, 0, "spinning due to token contention");
117SYSCTL_QUAD(_lwkt, OID_AUTO, mplock_contention_count, CTLFLAG_RW,
118 &mplock_contention_count, 0, "spinning due to MPLOCK contention");
119#endif
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120#endif
121
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122/*
123 * These helper procedures handle the runq, they can only be called from
124 * within a critical section.
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125 *
126 * WARNING! Prior to SMP being brought up it is possible to enqueue and
127 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
128 * instead of 'mycpu' when referencing the globaldata structure. Once
129 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 130 */
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131static __inline
132void
133_lwkt_dequeue(thread_t td)
134{
135 if (td->td_flags & TDF_RUNQ) {
4b5f931b 136 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 137 struct globaldata *gd = td->td_gd;
4b5f931b 138
f1d1c3fa 139 td->td_flags &= ~TDF_RUNQ;
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140 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq);
141 /* runqmask is passively cleaned up by the switcher */
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142 }
143}
144
145static __inline
146void
147_lwkt_enqueue(thread_t td)
148{
5d21b981 149 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING)) == 0) {
4b5f931b 150 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 151 struct globaldata *gd = td->td_gd;
4b5f931b 152
f1d1c3fa 153 td->td_flags |= TDF_RUNQ;
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154 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq);
155 gd->gd_runqmask |= 1 << nq;
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156 }
157}
8ad65e08 158
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159/*
160 * Schedule a thread to run. As the current thread we can always safely
161 * schedule ourselves, and a shortcut procedure is provided for that
162 * function.
163 *
164 * (non-blocking, self contained on a per cpu basis)
165 */
166void
167lwkt_schedule_self(thread_t td)
168{
169 crit_enter_quick(td);
170 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
171 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
172 _lwkt_enqueue(td);
173#ifdef _KERNEL
174 if (td->td_proc && td->td_proc->p_stat == SSLEEP)
175 panic("SCHED SELF PANIC");
176#endif
177 crit_exit_quick(td);
178}
179
180/*
181 * Deschedule a thread.
182 *
183 * (non-blocking, self contained on a per cpu basis)
184 */
185void
186lwkt_deschedule_self(thread_t td)
187{
188 crit_enter_quick(td);
189 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
190 _lwkt_dequeue(td);
191 crit_exit_quick(td);
192}
193
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194#ifdef _KERNEL
195
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196/*
197 * LWKTs operate on a per-cpu basis
198 *
73e4f7b9 199 * WARNING! Called from early boot, 'mycpu' may not work yet.
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200 */
201void
202lwkt_gdinit(struct globaldata *gd)
203{
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204 int i;
205
206 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
207 TAILQ_INIT(&gd->gd_tdrunq[i]);
208 gd->gd_runqmask = 0;
73e4f7b9 209 TAILQ_INIT(&gd->gd_tdallq);
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210}
211
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212#endif /* _KERNEL */
213
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214/*
215 * Initialize a thread wait structure prior to first use.
216 *
217 * NOTE! called from low level boot code, we cannot do anything fancy!
218 */
219void
41a01a4d 220lwkt_wait_init(lwkt_wait_t w)
7d0bac62 221{
41a01a4d 222 lwkt_token_init(&w->wa_token);
7d0bac62 223 TAILQ_INIT(&w->wa_waitq);
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224 w->wa_gen = 0;
225 w->wa_count = 0;
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226}
227
228/*
229 * Create a new thread. The thread must be associated with a process context
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230 * or LWKT start address before it can be scheduled. If the target cpu is
231 * -1 the thread will be created on the current cpu.
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232 *
233 * If you intend to create a thread without a process context this function
234 * does everything except load the startup and switcher function.
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235 */
236thread_t
f470d0c8 237lwkt_alloc_thread(struct thread *td, int stksize, int cpu)
7d0bac62 238{
99df837e 239 void *stack;
ef0fdad1 240 int flags = 0;
37af14fe 241 globaldata_t gd = mycpu;
7d0bac62 242
ef0fdad1 243 if (td == NULL) {
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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"));
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250 TAILQ_REMOVE(&gd->gd_tdfreeq, td, td_threadq);
251 crit_exit_gd(gd);
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252 flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
253 } else {
37af14fe 254 crit_exit_gd(gd);
05220613 255#ifdef _KERNEL
ef0fdad1 256 td = zalloc(thread_zone);
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257#else
258 td = malloc(sizeof(struct thread));
259#endif
ef0fdad1 260 td->td_kstack = NULL;
f470d0c8 261 td->td_kstack_size = 0;
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262 flags |= TDF_ALLOCATED_THREAD;
263 }
264 }
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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);
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269#else
270 libcaps_free_stack(stack, td->td_kstack_size);
271#endif
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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);
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288}
289
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290#ifdef _KERNEL
291
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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 *
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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
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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 */
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306#ifdef SMP
307
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308static void
309lwkt_init_thread_remote(void *arg)
310{
311 thread_t td = arg;
312
313 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
314}
315
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316#endif
317
7d0bac62 318void
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319lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
320 struct globaldata *gd)
7d0bac62 321{
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322 globaldata_t mygd = mycpu;
323
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324 bzero(td, sizeof(struct thread));
325 td->td_kstack = stack;
f470d0c8 326 td->td_kstack_size = stksize;
99df837e 327 td->td_flags |= flags;
26a0694b 328 td->td_gd = gd;
f8c3996b 329 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT;
c95cd171 330 lwkt_initport(&td->td_msgport, td);
99df837e 331 pmap_init_thread(td);
0f7a3396 332#ifdef SMP
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333 /*
334 * Normally initializing a thread for a remote cpu requires sending an
335 * IPI. However, the idlethread is setup before the other cpus are
336 * activated so we have to treat it as a special case. XXX manipulation
337 * of gd_tdallq requires the BGL.
338 */
339 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 340 crit_enter_gd(mygd);
75cdbe6c 341 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 342 crit_exit_gd(mygd);
75cdbe6c 343 } else {
2db3b277 344 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 345 }
0f7a3396 346#else
37af14fe 347 crit_enter_gd(mygd);
0f7a3396 348 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 349 crit_exit_gd(mygd);
0f7a3396 350#endif
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351}
352
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353#endif /* _KERNEL */
354
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355void
356lwkt_set_comm(thread_t td, const char *ctl, ...)
357{
e2565a42 358 __va_list va;
73e4f7b9 359
e2565a42 360 __va_start(va, ctl);
73e4f7b9 361 vsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 362 __va_end(va);
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363}
364
99df837e 365void
73e4f7b9 366lwkt_hold(thread_t td)
99df837e 367{
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368 ++td->td_refs;
369}
370
371void
372lwkt_rele(thread_t td)
373{
374 KKASSERT(td->td_refs > 0);
375 --td->td_refs;
376}
377
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378#ifdef _KERNEL
379
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380void
381lwkt_wait_free(thread_t td)
382{
383 while (td->td_refs)
377d4740 384 tsleep(td, 0, "tdreap", hz);
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385}
386
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387#endif
388
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389void
390lwkt_free_thread(thread_t td)
391{
392 struct globaldata *gd = mycpu;
393
d9eea1a5 394 KASSERT((td->td_flags & TDF_RUNNING) == 0,
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395 ("lwkt_free_thread: did not exit! %p", td));
396
37af14fe 397 crit_enter_gd(gd);
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398 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
399 if (gd->gd_tdfreecount < CACHE_NTHREADS &&
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400 (td->td_flags & TDF_ALLOCATED_THREAD)
401 ) {
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402 ++gd->gd_tdfreecount;
403 TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq);
37af14fe 404 crit_exit_gd(gd);
99df837e 405 } else {
37af14fe 406 crit_exit_gd(gd);
99df837e 407 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
05220613 408#ifdef _KERNEL
f470d0c8 409 kmem_free(kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
05220613 410#else
f470d0c8 411 libcaps_free_stack(td->td_kstack, td->td_kstack_size);
05220613 412#endif
73e4f7b9 413 /* gd invalid */
99df837e 414 td->td_kstack = NULL;
f470d0c8 415 td->td_kstack_size = 0;
99df837e 416 }
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417 if (td->td_flags & TDF_ALLOCATED_THREAD) {
418#ifdef _KERNEL
99df837e 419 zfree(thread_zone, td);
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420#else
421 free(td);
422#endif
423 }
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424 }
425}
426
427
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428/*
429 * Switch to the next runnable lwkt. If no LWKTs are runnable then
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430 * switch to the idlethread. Switching must occur within a critical
431 * section to avoid races with the scheduling queue.
432 *
433 * We always have full control over our cpu's run queue. Other cpus
434 * that wish to manipulate our queue must use the cpu_*msg() calls to
435 * talk to our cpu, so a critical section is all that is needed and
436 * the result is very, very fast thread switching.
437 *
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438 * The LWKT scheduler uses a fixed priority model and round-robins at
439 * each priority level. User process scheduling is a totally
440 * different beast and LWKT priorities should not be confused with
441 * user process priorities.
f1d1c3fa 442 *
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443 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch()
444 * cleans it up. Note that the td_switch() function cannot do anything that
445 * requires the MP lock since the MP lock will have already been setup for
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446 * the target thread (not the current thread). It's nice to have a scheduler
447 * that does not need the MP lock to work because it allows us to do some
448 * really cool high-performance MP lock optimizations.
8ad65e08 449 */
96728c05 450
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451void
452lwkt_switch(void)
453{
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454 globaldata_t gd = mycpu;
455 thread_t td = gd->gd_curthread;
8ad65e08 456 thread_t ntd;
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457#ifdef SMP
458 int mpheld;
459#endif
8ad65e08 460
46a3f46d 461 /*
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462 * Switching from within a 'fast' (non thread switched) interrupt or IPI
463 * is illegal. However, we may have to do it anyway if we hit a fatal
464 * kernel trap or we have paniced.
465 *
466 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 467 */
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468 if (gd->gd_intr_nesting_level) {
469 int savegdnest;
470 int savegdtrap;
471
472 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) {
473 panic("lwkt_switch: cannot switch from within "
474 "a fast interrupt, yet, td %p\n", td);
475 } else {
476 savegdnest = gd->gd_intr_nesting_level;
477 savegdtrap = gd->gd_trap_nesting_level;
478 gd->gd_intr_nesting_level = 0;
479 gd->gd_trap_nesting_level = 0;
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480 if ((td->td_flags & TDF_PANICWARN) == 0) {
481 td->td_flags |= TDF_PANICWARN;
482 printf("Warning: thread switch from interrupt or IPI, "
483 "thread %p (%s)\n", td, td->td_comm);
484#ifdef DDB
485 db_print_backtrace();
486#endif
487 }
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488 lwkt_switch();
489 gd->gd_intr_nesting_level = savegdnest;
490 gd->gd_trap_nesting_level = savegdtrap;
491 return;
492 }
96728c05 493 }
ef0fdad1 494
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495 /*
496 * Passive release (used to transition from user to kernel mode
497 * when we block or switch rather then when we enter the kernel).
498 * This function is NOT called if we are switching into a preemption
499 * or returning from a preemption. Typically this causes us to lose
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500 * our current process designation (if we have one) and become a true
501 * LWKT thread, and may also hand the current process designation to
502 * another process and schedule thread.
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503 */
504 if (td->td_release)
505 td->td_release(td);
506
37af14fe 507 crit_enter_gd(gd);
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508
509#ifdef SMP
510 /*
511 * td_mpcount cannot be used to determine if we currently hold the
512 * MP lock because get_mplock() will increment it prior to attempting
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513 * to get the lock, and switch out if it can't. Our ownership of
514 * the actual lock will remain stable while we are in a critical section
515 * (but, of course, another cpu may own or release the lock so the
516 * actual value of mp_lock is not stable).
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517 */
518 mpheld = MP_LOCK_HELD();
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519#ifdef INVARIANTS
520 if (td->td_cscount) {
521 printf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
522 td);
523 if (panic_on_cscount)
524 panic("switching while mastering cpusync");
525 }
526#endif
8a8d5d85 527#endif
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528 if ((ntd = td->td_preempted) != NULL) {
529 /*
530 * We had preempted another thread on this cpu, resume the preempted
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531 * thread. This occurs transparently, whether the preempted thread
532 * was scheduled or not (it may have been preempted after descheduling
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533 * itself).
534 *
535 * We have to setup the MP lock for the original thread after backing
536 * out the adjustment that was made to curthread when the original
537 * was preempted.
99df837e 538 */
26a0694b 539 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
8a8d5d85 540#ifdef SMP
96728c05 541 if (ntd->td_mpcount && mpheld == 0) {
fc92d4aa 542 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d",
96728c05
MD
543 td, ntd, td->td_mpcount, ntd->td_mpcount);
544 }
8a8d5d85
MD
545 if (ntd->td_mpcount) {
546 td->td_mpcount -= ntd->td_mpcount;
547 KKASSERT(td->td_mpcount >= 0);
548 }
549#endif
26a0694b 550 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
551
552 /*
553 * XXX. The interrupt may have woken a thread up, we need to properly
554 * set the reschedule flag if the originally interrupted thread is at
555 * a lower priority.
556 */
557 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1)
558 need_lwkt_resched();
8a8d5d85 559 /* YYY release mp lock on switchback if original doesn't need it */
8ad65e08 560 } else {
4b5f931b
MD
561 /*
562 * Priority queue / round-robin at each priority. Note that user
563 * processes run at a fixed, low priority and the user process
564 * scheduler deals with interactions between user processes
565 * by scheduling and descheduling them from the LWKT queue as
566 * necessary.
8a8d5d85
MD
567 *
568 * We have to adjust the MP lock for the target thread. If we
569 * need the MP lock and cannot obtain it we try to locate a
41a01a4d
MD
570 * thread that does not need the MP lock. If we cannot, we spin
571 * instead of HLT.
572 *
573 * A similar issue exists for the tokens held by the target thread.
574 * If we cannot obtain ownership of the tokens we cannot immediately
575 * schedule the thread.
576 */
577
578 /*
579 * We are switching threads. If there are any pending requests for
580 * tokens we can satisfy all of them here.
4b5f931b 581 */
41a01a4d
MD
582#ifdef SMP
583 if (gd->gd_tokreqbase)
584 lwkt_drain_token_requests();
585#endif
586
8ec60c3f
MD
587 /*
588 * If an LWKT reschedule was requested, well that is what we are
589 * doing now so clear it.
590 */
591 clear_lwkt_resched();
4b5f931b
MD
592again:
593 if (gd->gd_runqmask) {
594 int nq = bsrl(gd->gd_runqmask);
595 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
596 gd->gd_runqmask &= ~(1 << nq);
597 goto again;
598 }
8a8d5d85 599#ifdef SMP
41a01a4d 600 /*
df6b8ba0
MD
601 * THREAD SELECTION FOR AN SMP MACHINE BUILD
602 *
41a01a4d
MD
603 * If the target needs the MP lock and we couldn't get it,
604 * or if the target is holding tokens and we could not
605 * gain ownership of the tokens, continue looking for a
606 * thread to schedule and spin instead of HLT if we can't.
a453459d
MD
607 *
608 * NOTE: the mpheld variable invalid after this conditional, it
609 * can change due to both cpu_try_mplock() returning success
610 * AND interactions in lwkt_chktokens() due to the fact that
611 * we are trying to check the mpcount of a thread other then
612 * the current thread. Because of this, if the current thread
613 * is not holding td_mpcount, an IPI indirectly run via
614 * lwkt_chktokens() can obtain and release the MP lock and
615 * cause the core MP lock to be released.
41a01a4d
MD
616 */
617 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) ||
618 (ntd->td_toks && lwkt_chktokens(ntd) == 0)
619 ) {
8a8d5d85 620 u_int32_t rqmask = gd->gd_runqmask;
a453459d
MD
621
622 mpheld = MP_LOCK_HELD();
623 ntd = NULL;
8a8d5d85
MD
624 while (rqmask) {
625 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) {
38717797 626 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) {
a453459d 627 /* spinning due to MP lock being held */
38717797 628#ifdef INVARIANTS
a453459d 629 ++mplock_contention_count;
38717797 630#endif
a453459d 631 /* mplock still not held, 'mpheld' still valid */
41a01a4d 632 continue;
38717797 633 }
a453459d
MD
634
635 /*
636 * mpheld state invalid after chktokens call returns
637 * failure, but the variable is only needed for
638 * the loop.
639 */
38717797 640 if (ntd->td_toks && !lwkt_chktokens(ntd)) {
a453459d 641 /* spinning due to token contention */
38717797 642#ifdef INVARIANTS
a453459d 643 ++token_contention_count;
38717797 644#endif
a453459d 645 mpheld = MP_LOCK_HELD();
41a01a4d 646 continue;
38717797 647 }
41a01a4d 648 break;
8a8d5d85
MD
649 }
650 if (ntd)
651 break;
652 rqmask &= ~(1 << nq);
653 nq = bsrl(rqmask);
654 }
655 if (ntd == NULL) {
a2a5ad0d
MD
656 ntd = &gd->gd_idlethread;
657 ntd->td_flags |= TDF_IDLE_NOHLT;
df6b8ba0 658 goto using_idle_thread;
8a8d5d85
MD
659 } else {
660 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
661 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
662 }
663 } else {
664 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
665 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
666 }
667#else
df6b8ba0
MD
668 /*
669 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to
670 * worry about tokens or the BGL.
671 */
4b5f931b
MD
672 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
673 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
8a8d5d85 674#endif
4b5f931b 675 } else {
3c23a41a 676 /*
60f945af
MD
677 * We have nothing to run but only let the idle loop halt
678 * the cpu if there are no pending interrupts.
3c23a41a 679 */
a2a5ad0d 680 ntd = &gd->gd_idlethread;
60f945af 681 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
3c23a41a 682 ntd->td_flags |= TDF_IDLE_NOHLT;
a453459d 683#ifdef SMP
df6b8ba0
MD
684using_idle_thread:
685 /*
686 * The idle thread should not be holding the MP lock unless we
687 * are trapping in the kernel or in a panic. Since we select the
688 * idle thread unconditionally when no other thread is available,
689 * if the MP lock is desired during a panic or kernel trap, we
690 * have to loop in the scheduler until we get it.
691 */
692 if (ntd->td_mpcount) {
693 mpheld = MP_LOCK_HELD();
694 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
695 panic("Idle thread %p was holding the BGL!", ntd);
696 else if (mpheld == 0)
697 goto again;
698 }
a453459d 699#endif
4b5f931b 700 }
f1d1c3fa 701 }
26a0694b
MD
702 KASSERT(ntd->td_pri >= TDPRI_CRIT,
703 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
8a8d5d85
MD
704
705 /*
706 * Do the actual switch. If the new target does not need the MP lock
707 * and we are holding it, release the MP lock. If the new target requires
708 * the MP lock we have already acquired it for the target.
709 */
710#ifdef SMP
711 if (ntd->td_mpcount == 0 ) {
712 if (MP_LOCK_HELD())
713 cpu_rel_mplock();
714 } else {
a453459d 715 ASSERT_MP_LOCK_HELD(ntd);
8a8d5d85
MD
716 }
717#endif
94f6d86e
MD
718 if (td != ntd) {
719 ++switch_count;
f1d1c3fa 720 td->td_switch(ntd);
94f6d86e 721 }
37af14fe
MD
722 /* NOTE: current cpu may have changed after switch */
723 crit_exit_quick(td);
8ad65e08
MD
724}
725
b68b7282 726/*
96728c05
MD
727 * Request that the target thread preempt the current thread. Preemption
728 * only works under a specific set of conditions:
b68b7282 729 *
96728c05
MD
730 * - We are not preempting ourselves
731 * - The target thread is owned by the current cpu
732 * - We are not currently being preempted
733 * - The target is not currently being preempted
734 * - We are able to satisfy the target's MP lock requirements (if any).
735 *
736 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
737 * this is called via lwkt_schedule() through the td_preemptable callback.
738 * critpri is the managed critical priority that we should ignore in order
739 * to determine whether preemption is possible (aka usually just the crit
740 * priority of lwkt_schedule() itself).
b68b7282 741 *
26a0694b
MD
742 * XXX at the moment we run the target thread in a critical section during
743 * the preemption in order to prevent the target from taking interrupts
744 * that *WE* can't. Preemption is strictly limited to interrupt threads
745 * and interrupt-like threads, outside of a critical section, and the
746 * preempted source thread will be resumed the instant the target blocks
747 * whether or not the source is scheduled (i.e. preemption is supposed to
748 * be as transparent as possible).
4b5f931b 749 *
8a8d5d85
MD
750 * The target thread inherits our MP count (added to its own) for the
751 * duration of the preemption in order to preserve the atomicy of the
96728c05
MD
752 * MP lock during the preemption. Therefore, any preempting targets must be
753 * careful in regards to MP assertions. Note that the MP count may be
71ef2f5c
MD
754 * out of sync with the physical mp_lock, but we do not have to preserve
755 * the original ownership of the lock if it was out of synch (that is, we
756 * can leave it synchronized on return).
b68b7282
MD
757 */
758void
96728c05 759lwkt_preempt(thread_t ntd, int critpri)
b68b7282 760{
46a3f46d 761 struct globaldata *gd = mycpu;
0a3f9b47 762 thread_t td;
8a8d5d85
MD
763#ifdef SMP
764 int mpheld;
57c254db 765 int savecnt;
8a8d5d85 766#endif
b68b7282 767
26a0694b 768 /*
96728c05
MD
769 * The caller has put us in a critical section. We can only preempt
770 * if the caller of the caller was not in a critical section (basically
0a3f9b47 771 * a local interrupt), as determined by the 'critpri' parameter.
96728c05
MD
772 *
773 * YYY The target thread must be in a critical section (else it must
774 * inherit our critical section? I dunno yet).
41a01a4d
MD
775 *
776 * Any tokens held by the target may not be held by thread(s) being
777 * preempted. We take the easy way out and do not preempt if
778 * the target is holding tokens.
0a3f9b47
MD
779 *
780 * Set need_lwkt_resched() unconditionally for now YYY.
26a0694b
MD
781 */
782 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 783
0a3f9b47 784 td = gd->gd_curthread;
0a3f9b47 785 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) {
57c254db
MD
786 ++preempt_miss;
787 return;
788 }
96728c05
MD
789 if ((td->td_pri & ~TDPRI_MASK) > critpri) {
790 ++preempt_miss;
8ec60c3f 791 need_lwkt_resched();
96728c05
MD
792 return;
793 }
794#ifdef SMP
46a3f46d 795 if (ntd->td_gd != gd) {
96728c05 796 ++preempt_miss;
8ec60c3f 797 need_lwkt_resched();
96728c05
MD
798 return;
799 }
800#endif
41a01a4d
MD
801 /*
802 * Take the easy way out and do not preempt if the target is holding
803 * one or more tokens. We could test whether the thread(s) being
804 * preempted interlock against the target thread's tokens and whether
805 * we can get all the target thread's tokens, but this situation
806 * should not occur very often so its easier to simply not preempt.
807 */
808 if (ntd->td_toks != NULL) {
809 ++preempt_miss;
8ec60c3f 810 need_lwkt_resched();
41a01a4d
MD
811 return;
812 }
26a0694b
MD
813 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
814 ++preempt_weird;
8ec60c3f 815 need_lwkt_resched();
26a0694b
MD
816 return;
817 }
818 if (ntd->td_preempted) {
4b5f931b 819 ++preempt_hit;
8ec60c3f 820 need_lwkt_resched();
26a0694b 821 return;
b68b7282 822 }
8a8d5d85 823#ifdef SMP
a2a5ad0d
MD
824 /*
825 * note: an interrupt might have occured just as we were transitioning
71ef2f5c
MD
826 * to or from the MP lock. In this case td_mpcount will be pre-disposed
827 * (non-zero) but not actually synchronized with the actual state of the
828 * lock. We can use it to imply an MP lock requirement for the
829 * preemption but we cannot use it to test whether we hold the MP lock
830 * or not.
a2a5ad0d 831 */
96728c05 832 savecnt = td->td_mpcount;
71ef2f5c 833 mpheld = MP_LOCK_HELD();
8a8d5d85
MD
834 ntd->td_mpcount += td->td_mpcount;
835 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) {
836 ntd->td_mpcount -= td->td_mpcount;
837 ++preempt_miss;
8ec60c3f 838 need_lwkt_resched();
8a8d5d85
MD
839 return;
840 }
841#endif
26a0694b 842
8ec60c3f
MD
843 /*
844 * Since we are able to preempt the current thread, there is no need to
845 * call need_lwkt_resched().
846 */
26a0694b
MD
847 ++preempt_hit;
848 ntd->td_preempted = td;
849 td->td_flags |= TDF_PREEMPT_LOCK;
850 td->td_switch(ntd);
851 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
96728c05
MD
852#ifdef SMP
853 KKASSERT(savecnt == td->td_mpcount);
71ef2f5c
MD
854 mpheld = MP_LOCK_HELD();
855 if (mpheld && td->td_mpcount == 0)
96728c05 856 cpu_rel_mplock();
71ef2f5c 857 else if (mpheld == 0 && td->td_mpcount)
96728c05
MD
858 panic("lwkt_preempt(): MP lock was not held through");
859#endif
26a0694b
MD
860 ntd->td_preempted = NULL;
861 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
862}
863
f1d1c3fa
MD
864/*
865 * Yield our thread while higher priority threads are pending. This is
866 * typically called when we leave a critical section but it can be safely
867 * called while we are in a critical section.
868 *
869 * This function will not generally yield to equal priority threads but it
870 * can occur as a side effect. Note that lwkt_switch() is called from
46a3f46d 871 * inside the critical section to prevent its own crit_exit() from reentering
f1d1c3fa
MD
872 * lwkt_yield_quick().
873 *
235957ed 874 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint
ef0fdad1
MD
875 * came along but was blocked and made pending.
876 *
f1d1c3fa
MD
877 * (self contained on a per cpu basis)
878 */
879void
880lwkt_yield_quick(void)
881{
7966cb69
MD
882 globaldata_t gd = mycpu;
883 thread_t td = gd->gd_curthread;
ef0fdad1 884
a2a5ad0d 885 /*
235957ed 886 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear
a2a5ad0d
MD
887 * it with a non-zero cpl then we might not wind up calling splz after
888 * a task switch when the critical section is exited even though the
46a3f46d 889 * new task could accept the interrupt.
a2a5ad0d
MD
890 *
891 * XXX from crit_exit() only called after last crit section is released.
892 * If called directly will run splz() even if in a critical section.
46a3f46d
MD
893 *
894 * td_nest_count prevent deep nesting via splz() or doreti(). Note that
895 * except for this special case, we MUST call splz() here to handle any
896 * pending ints, particularly after we switch, or we might accidently
897 * halt the cpu with interrupts pending.
a2a5ad0d 898 */
46a3f46d 899 if (gd->gd_reqflags && td->td_nest_count < 2)
f1d1c3fa 900 splz();
f1d1c3fa
MD
901
902 /*
903 * YYY enabling will cause wakeup() to task-switch, which really
904 * confused the old 4.x code. This is a good way to simulate
7d0bac62
MD
905 * preemption and MP without actually doing preemption or MP, because a
906 * lot of code assumes that wakeup() does not block.
f1d1c3fa 907 */
46a3f46d
MD
908 if (untimely_switch && td->td_nest_count == 0 &&
909 gd->gd_intr_nesting_level == 0
910 ) {
37af14fe 911 crit_enter_quick(td);
f1d1c3fa
MD
912 /*
913 * YYY temporary hacks until we disassociate the userland scheduler
914 * from the LWKT scheduler.
915 */
916 if (td->td_flags & TDF_RUNQ) {
917 lwkt_switch(); /* will not reenter yield function */
918 } else {
37af14fe 919 lwkt_schedule_self(td); /* make sure we are scheduled */
f1d1c3fa 920 lwkt_switch(); /* will not reenter yield function */
37af14fe 921 lwkt_deschedule_self(td); /* make sure we are descheduled */
f1d1c3fa 922 }
7966cb69 923 crit_exit_noyield(td);
f1d1c3fa 924 }
f1d1c3fa
MD
925}
926
8ad65e08 927/*
f1d1c3fa 928 * This implements a normal yield which, unlike _quick, will yield to equal
235957ed 929 * priority threads as well. Note that gd_reqflags tests will be handled by
f1d1c3fa
MD
930 * the crit_exit() call in lwkt_switch().
931 *
932 * (self contained on a per cpu basis)
8ad65e08
MD
933 */
934void
f1d1c3fa 935lwkt_yield(void)
8ad65e08 936{
37af14fe 937 lwkt_schedule_self(curthread);
f1d1c3fa
MD
938 lwkt_switch();
939}
940
8ad65e08 941/*
f1d1c3fa
MD
942 * Generic schedule. Possibly schedule threads belonging to other cpus and
943 * deal with threads that might be blocked on a wait queue.
944 *
0a3f9b47
MD
945 * We have a little helper inline function which does additional work after
946 * the thread has been enqueued, including dealing with preemption and
947 * setting need_lwkt_resched() (which prevents the kernel from returning
948 * to userland until it has processed higher priority threads).
8ad65e08 949 */
0a3f9b47
MD
950static __inline
951void
8ec60c3f 952_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri)
0a3f9b47
MD
953{
954 if (ntd->td_preemptable) {
955 ntd->td_preemptable(ntd, cpri); /* YYY +token */
8ec60c3f
MD
956 } else if ((ntd->td_flags & TDF_NORESCHED) == 0 &&
957 (ntd->td_pri & TDPRI_MASK) > (gd->gd_curthread->td_pri & TDPRI_MASK)
958 ) {
959 need_lwkt_resched();
0a3f9b47
MD
960 }
961}
962
8ad65e08
MD
963void
964lwkt_schedule(thread_t td)
965{
37af14fe
MD
966 globaldata_t mygd = mycpu;
967
96728c05 968#ifdef INVARIANTS
41a01a4d 969 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
26a0694b
MD
970 if ((td->td_flags & TDF_PREEMPT_LOCK) == 0 && td->td_proc
971 && td->td_proc->p_stat == SSLEEP
972 ) {
973 printf("PANIC schedule curtd = %p (%d %d) target %p (%d %d)\n",
974 curthread,
975 curthread->td_proc ? curthread->td_proc->p_pid : -1,
976 curthread->td_proc ? curthread->td_proc->p_stat : -1,
977 td,
df6b8ba0
MD
978 td->td_proc ? td->td_proc->p_pid : -1,
979 td->td_proc ? td->td_proc->p_stat : -1
26a0694b
MD
980 );
981 panic("SCHED PANIC");
982 }
96728c05 983#endif
37af14fe
MD
984 crit_enter_gd(mygd);
985 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
986 _lwkt_enqueue(td);
987 } else {
988 lwkt_wait_t w;
989
990 /*
991 * If the thread is on a wait list we have to send our scheduling
992 * request to the owner of the wait structure. Otherwise we send
993 * the scheduling request to the cpu owning the thread. Races
994 * are ok, the target will forward the message as necessary (the
995 * message may chase the thread around before it finally gets
996 * acted upon).
997 *
998 * (remember, wait structures use stable storage)
0a3f9b47 999 *
0c453950
MD
1000 * NOTE: we have to account for the number of critical sections
1001 * under our control when calling _lwkt_schedule_post() so it
1002 * can figure out whether preemption is allowed.
1003 *
1004 * NOTE: The wait structure algorithms are a mess and need to be
1005 * rewritten.
1006 *
1007 * NOTE: We cannot safely acquire or release a token, even
1008 * non-blocking, because this routine may be called in the context
1009 * of a thread already holding the token and thus not provide any
1010 * interlock protection. We cannot safely manipulate the td_toks
1011 * list for the same reason. Instead we depend on our critical
1012 * section if the token is owned by our cpu.
f1d1c3fa
MD
1013 */
1014 if ((w = td->td_wait) != NULL) {
0c453950 1015 if (w->wa_token.t_cpu == mygd) {
f1d1c3fa
MD
1016 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
1017 --w->wa_count;
1018 td->td_wait = NULL;
0f7a3396 1019#ifdef SMP
8ec60c3f 1020 if (td->td_gd == mygd) {
f1d1c3fa 1021 _lwkt_enqueue(td);
8ec60c3f 1022 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
f1d1c3fa 1023 } else {
b8a98473 1024 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
f1d1c3fa 1025 }
0f7a3396
MD
1026#else
1027 _lwkt_enqueue(td);
8ec60c3f 1028 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
0f7a3396 1029#endif
f1d1c3fa 1030 } else {
b8a98473
MD
1031#ifdef SMP
1032 lwkt_send_ipiq(w->wa_token.t_cpu, (ipifunc1_t)lwkt_schedule, td);
1033#else
1034 panic("bad token %p", &w->wa_token);
1035#endif
f1d1c3fa
MD
1036 }
1037 } else {
1038 /*
1039 * If the wait structure is NULL and we own the thread, there
1040 * is no race (since we are in a critical section). If we
1041 * do not own the thread there might be a race but the
1042 * target cpu will deal with it.
1043 */
0f7a3396 1044#ifdef SMP
37af14fe 1045 if (td->td_gd == mygd) {
f1d1c3fa 1046 _lwkt_enqueue(td);
8ec60c3f 1047 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
f1d1c3fa 1048 } else {
b8a98473 1049 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
f1d1c3fa 1050 }
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1051#else
1052 _lwkt_enqueue(td);
8ec60c3f 1053 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
0f7a3396 1054#endif
f1d1c3fa 1055 }
8ad65e08 1056 }
37af14fe 1057 crit_exit_gd(mygd);
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MD
1058}
1059
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1060/*
1061 * Managed acquisition. This code assumes that the MP lock is held for
1062 * the tdallq operation and that the thread has been descheduled from its
1063 * original cpu. We also have to wait for the thread to be entirely switched
1064 * out on its original cpu (this is usually fast enough that we never loop)
1065 * since the LWKT system does not have to hold the MP lock while switching
1066 * and the target may have released it before switching.
1067 */
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1068void
1069lwkt_acquire(thread_t td)
1070{
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1071 globaldata_t gd;
1072 globaldata_t mygd;
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1073
1074 gd = td->td_gd;
37af14fe 1075 mygd = mycpu;
35238fa5 1076 cpu_lfence();
a2a5ad0d 1077 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
d9eea1a5 1078 while (td->td_flags & TDF_RUNNING) /* XXX spin */
35238fa5 1079 cpu_lfence();
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1080 if (gd != mygd) {
1081 crit_enter_gd(mygd);
a2a5ad0d 1082 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); /* protected by BGL */
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1083 td->td_gd = mygd;
1084 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); /* protected by BGL */
1085 crit_exit_gd(mygd);
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1086 }
1087}
1088
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1089/*
1090 * Generic deschedule. Descheduling threads other then your own should be
1091 * done only in carefully controlled circumstances. Descheduling is
1092 * asynchronous.
1093 *
1094 * This function may block if the cpu has run out of messages.
8ad65e08
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1095 */
1096void
1097lwkt_deschedule(thread_t td)
1098{
f1d1c3fa 1099 crit_enter();
b8a98473 1100#ifdef SMP
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1101 if (td == curthread) {
1102 _lwkt_dequeue(td);
1103 } else {
a72187e9 1104 if (td->td_gd == mycpu) {
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MD
1105 _lwkt_dequeue(td);
1106 } else {
b8a98473 1107 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
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MD
1108 }
1109 }
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1110#else
1111 _lwkt_dequeue(td);
1112#endif
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1113 crit_exit();
1114}
1115
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1116/*
1117 * Set the target thread's priority. This routine does not automatically
1118 * switch to a higher priority thread, LWKT threads are not designed for
1119 * continuous priority changes. Yield if you want to switch.
1120 *
1121 * We have to retain the critical section count which uses the high bits
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1122 * of the td_pri field. The specified priority may also indicate zero or
1123 * more critical sections by adding TDPRI_CRIT*N.
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1124 *
1125 * Note that we requeue the thread whether it winds up on a different runq
1126 * or not. uio_yield() depends on this and the routine is not normally
1127 * called with the same priority otherwise.
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1128 */
1129void
1130lwkt_setpri(thread_t td, int pri)
1131{
26a0694b 1132 KKASSERT(pri >= 0);
a72187e9 1133 KKASSERT(td->td_gd == mycpu);
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MD
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
1145void
1146lwkt_setpri_self(int pri)
1147{
1148 thread_t td = curthread;
1149
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1150 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1151 crit_enter();
1152 if (td->td_flags & TDF_RUNQ) {
1153 _lwkt_dequeue(td);
1154 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1155 _lwkt_enqueue(td);
1156 } else {
1157 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1158 }
1159 crit_exit();
1160}
1161
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1162/*
1163 * Determine if there is a runnable thread at a higher priority then
1164 * the current thread. lwkt_setpri() does not check this automatically.
1165 * Return 1 if there is, 0 if there isn't.
1166 *
1167 * Example: if bit 31 of runqmask is set and the current thread is priority
1168 * 30, then we wind up checking the mask: 0x80000000 against 0x7fffffff.
1169 *
1170 * If nq reaches 31 the shift operation will overflow to 0 and we will wind
1171 * up comparing against 0xffffffff, a comparison that will always be false.
1172 */
1173int
1174lwkt_checkpri_self(void)
1175{
1176 globaldata_t gd = mycpu;
1177 thread_t td = gd->gd_curthread;
1178 int nq = td->td_pri & TDPRI_MASK;
1179
1180 while (gd->gd_runqmask > (__uint32_t)(2 << nq) - 1) {
1181 if (TAILQ_FIRST(&gd->gd_tdrunq[nq + 1]))
1182 return(1);
1183 ++nq;
1184 }
1185 return(0);
1186}
1187
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1188/*
1189 * Migrate the current thread to the specified cpu. The BGL must be held
1190 * (for the gd_tdallq manipulation XXX). This is accomplished by
1191 * descheduling ourselves from the current cpu, moving our thread to the
1192 * tdallq of the target cpu, IPI messaging the target cpu, and switching out.
1193 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1194 */
3d28ff59 1195#ifdef SMP
5d21b981 1196static void lwkt_setcpu_remote(void *arg);
3d28ff59 1197#endif
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1198
1199void
1200lwkt_setcpu_self(globaldata_t rgd)
1201{
1202#ifdef SMP
1203 thread_t td = curthread;
1204
1205 if (td->td_gd != rgd) {
1206 crit_enter_quick(td);
1207 td->td_flags |= TDF_MIGRATING;
1208 lwkt_deschedule_self(td);
1209 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); /* protected by BGL */
1210 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); /* protected by BGL */
b8a98473 1211 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td);
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1212 lwkt_switch();
1213 /* we are now on the target cpu */
1214 crit_exit_quick(td);
1215 }
1216#endif
1217}
1218
1219/*
1220 * Remote IPI for cpu migration (called while in a critical section so we
1221 * do not have to enter another one). The thread has already been moved to
1222 * our cpu's allq, but we must wait for the thread to be completely switched
1223 * out on the originating cpu before we schedule it on ours or the stack
1224 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD
1225 * change to main memory.
1226 *
1227 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races
1228 * against wakeups. It is best if this interface is used only when there
1229 * are no pending events that might try to schedule the thread.
1230 */
3d28ff59 1231#ifdef SMP
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1232static void
1233lwkt_setcpu_remote(void *arg)
1234{
1235 thread_t td = arg;
1236 globaldata_t gd = mycpu;
1237
1238 while (td->td_flags & TDF_RUNNING)
35238fa5 1239 cpu_lfence();
5d21b981 1240 td->td_gd = gd;
35238fa5 1241 cpu_sfence();
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1242 td->td_flags &= ~TDF_MIGRATING;
1243 _lwkt_enqueue(td);
1244}
3d28ff59 1245#endif
5d21b981 1246
553ea3c8 1247struct lwp *
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1248lwkt_preempted_proc(void)
1249{
73e4f7b9 1250 thread_t td = curthread;
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1251 while (td->td_preempted)
1252 td = td->td_preempted;
553ea3c8 1253 return(td->td_lwp);
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MD
1254}
1255
f1d1c3fa 1256/*
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1257 * Block on the specified wait queue until signaled. A generation number
1258 * must be supplied to interlock the wait queue. The function will
1259 * return immediately if the generation number does not match the wait
1260 * structure's generation number.
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MD
1261 */
1262void
ae8050a4 1263lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen)
f1d1c3fa
MD
1264{
1265 thread_t td = curthread;
41a01a4d 1266 lwkt_tokref ilock;
f1d1c3fa 1267
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MD
1268 lwkt_gettoken(&ilock, &w->wa_token);
1269 crit_enter();
ae8050a4 1270 if (w->wa_gen == *gen) {
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MD
1271 _lwkt_dequeue(td);
1272 TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq);
1273 ++w->wa_count;
1274 td->td_wait = w;
ae8050a4 1275 td->td_wmesg = wmesg;
41a01a4d 1276 again:
f1d1c3fa 1277 lwkt_switch();
ece04fd0
MD
1278 if (td->td_wmesg != NULL) {
1279 _lwkt_dequeue(td);
1280 goto again;
1281 }
8ad65e08 1282 }
41a01a4d 1283 crit_exit();
ae8050a4 1284 *gen = w->wa_gen;
41a01a4d 1285 lwkt_reltoken(&ilock);
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MD
1286}
1287
1288/*
1289 * Signal a wait queue. We gain ownership of the wait queue in order to
1290 * signal it. Once a thread is removed from the wait queue we have to
1291 * deal with the cpu owning the thread.
1292 *
1293 * Note: alternatively we could message the target cpu owning the wait
1294 * queue. YYY implement as sysctl.
1295 */
1296void
ece04fd0 1297lwkt_signal(lwkt_wait_t w, int count)
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MD
1298{
1299 thread_t td;
41a01a4d 1300 lwkt_tokref ilock;
f1d1c3fa 1301
41a01a4d 1302 lwkt_gettoken(&ilock, &w->wa_token);
f1d1c3fa 1303 ++w->wa_gen;
41a01a4d 1304 crit_enter();
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MD
1305 if (count < 0)
1306 count = w->wa_count;
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MD
1307 while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) {
1308 --count;
1309 --w->wa_count;
1310 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
1311 td->td_wait = NULL;
ae8050a4 1312 td->td_wmesg = NULL;
b8a98473 1313#ifdef SMP
a72187e9 1314 if (td->td_gd == mycpu) {
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MD
1315 _lwkt_enqueue(td);
1316 } else {
b8a98473 1317 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
f1d1c3fa 1318 }
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MD
1319#else
1320 _lwkt_enqueue(td);
1321#endif
f1d1c3fa 1322 }
41a01a4d
MD
1323 crit_exit();
1324 lwkt_reltoken(&ilock);
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MD
1325}
1326
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MD
1327/*
1328 * Create a kernel process/thread/whatever. It shares it's address space
1329 * with proc0 - ie: kernel only.
1330 *
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MD
1331 * NOTE! By default new threads are created with the MP lock held. A
1332 * thread which does not require the MP lock should release it by calling
1333 * rel_mplock() at the start of the new thread.
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MD
1334 */
1335int
1336lwkt_create(void (*func)(void *), void *arg,
75cdbe6c 1337 struct thread **tdp, thread_t template, int tdflags, int cpu,
ef0fdad1 1338 const char *fmt, ...)
99df837e 1339{
73e4f7b9 1340 thread_t td;
e2565a42 1341 __va_list ap;
99df837e 1342
f470d0c8 1343 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu);
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MD
1344 if (tdp)
1345 *tdp = td;
709799ea 1346 cpu_set_thread_handler(td, lwkt_exit, func, arg);
ef0fdad1 1347 td->td_flags |= TDF_VERBOSE | tdflags;
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MD
1348#ifdef SMP
1349 td->td_mpcount = 1;
1350#endif
99df837e
MD
1351
1352 /*
1353 * Set up arg0 for 'ps' etc
1354 */
e2565a42 1355 __va_start(ap, fmt);
99df837e 1356 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1357 __va_end(ap);
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MD
1358
1359 /*
1360 * Schedule the thread to run
1361 */
ef0fdad1
MD
1362 if ((td->td_flags & TDF_STOPREQ) == 0)
1363 lwkt_schedule(td);
1364 else
1365 td->td_flags &= ~TDF_STOPREQ;
99df837e
MD
1366 return 0;
1367}
1368
2d93b37a 1369/*
2d93b37a
MD
1370 * kthread_* is specific to the kernel and is not needed by userland.
1371 */
1372#ifdef _KERNEL
1373
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MD
1374/*
1375 * Destroy an LWKT thread. Warning! This function is not called when
1376 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1377 * uses a different reaping mechanism.
1378 */
1379void
1380lwkt_exit(void)
1381{
1382 thread_t td = curthread;
8826f33a 1383 globaldata_t gd;
99df837e
MD
1384
1385 if (td->td_flags & TDF_VERBOSE)
1386 printf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1387 caps_exit(td);
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MD
1388 crit_enter_quick(td);
1389 lwkt_deschedule_self(td);
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MD
1390 gd = mycpu;
1391 KKASSERT(gd == td->td_gd);
1392 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1393 if (td->td_flags & TDF_ALLOCATED_THREAD) {
1394 ++gd->gd_tdfreecount;
1395 TAILQ_INSERT_TAIL(&gd->gd_tdfreeq, td, td_threadq);
1396 }
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MD
1397 cpu_thread_exit();
1398}
1399
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MD
1400#endif /* _KERNEL */
1401
1402void
1403crit_panic(void)
1404{
1405 thread_t td = curthread;
1406 int lpri = td->td_pri;
1407
1408 td->td_pri = 0;
1409 panic("td_pri is/would-go negative! %p %d", td, lpri);
1410}
1411
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1412#ifdef SMP
1413
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MD
1414/*
1415 * Called from debugger/panic on cpus which have been stopped. We must still
1416 * process the IPIQ while stopped, even if we were stopped while in a critical
1417 * section (XXX).
1418 *
1419 * If we are dumping also try to process any pending interrupts. This may
1420 * or may not work depending on the state of the cpu at the point it was
1421 * stopped.
1422 */
1423void
1424lwkt_smp_stopped(void)
1425{
1426 globaldata_t gd = mycpu;
1427
1428 crit_enter_gd(gd);
1429 if (dumping) {
1430 lwkt_process_ipiq();
1431 splz();
1432 } else {
1433 lwkt_process_ipiq();
1434 }
1435 crit_exit_gd(gd);
1436}
1437
d165e668 1438#endif