Do not try to set up hardware vectors for software interrupts.
[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 *
c2fba90b 34 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.87 2005/11/21 18:49:26 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{
344ad853 149 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_TSLEEPQ|TDF_BLOCKQ)) == 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!"));
344ad853 172 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
37af14fe 173 _lwkt_enqueue(td);
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174 crit_exit_quick(td);
175}
176
177/*
178 * Deschedule a thread.
179 *
180 * (non-blocking, self contained on a per cpu basis)
181 */
182void
183lwkt_deschedule_self(thread_t td)
184{
185 crit_enter_quick(td);
186 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
187 _lwkt_dequeue(td);
188 crit_exit_quick(td);
189}
190
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191#ifdef _KERNEL
192
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193/*
194 * LWKTs operate on a per-cpu basis
195 *
73e4f7b9 196 * WARNING! Called from early boot, 'mycpu' may not work yet.
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197 */
198void
199lwkt_gdinit(struct globaldata *gd)
200{
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201 int i;
202
203 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
204 TAILQ_INIT(&gd->gd_tdrunq[i]);
205 gd->gd_runqmask = 0;
73e4f7b9 206 TAILQ_INIT(&gd->gd_tdallq);
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207}
208
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209#endif /* _KERNEL */
210
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211/*
212 * Initialize a thread wait structure prior to first use.
213 *
214 * NOTE! called from low level boot code, we cannot do anything fancy!
215 */
216void
41a01a4d 217lwkt_wait_init(lwkt_wait_t w)
7d0bac62 218{
41a01a4d 219 lwkt_token_init(&w->wa_token);
7d0bac62 220 TAILQ_INIT(&w->wa_waitq);
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221 w->wa_gen = 0;
222 w->wa_count = 0;
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223}
224
225/*
226 * Create a new thread. The thread must be associated with a process context
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227 * or LWKT start address before it can be scheduled. If the target cpu is
228 * -1 the thread will be created on the current cpu.
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229 *
230 * If you intend to create a thread without a process context this function
231 * does everything except load the startup and switcher function.
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232 */
233thread_t
f470d0c8 234lwkt_alloc_thread(struct thread *td, int stksize, int cpu)
7d0bac62 235{
99df837e 236 void *stack;
ef0fdad1 237 int flags = 0;
37af14fe 238 globaldata_t gd = mycpu;
7d0bac62 239
ef0fdad1 240 if (td == NULL) {
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241 crit_enter_gd(gd);
242 if (gd->gd_tdfreecount > 0) {
243 --gd->gd_tdfreecount;
244 td = TAILQ_FIRST(&gd->gd_tdfreeq);
d9eea1a5 245 KASSERT(td != NULL && (td->td_flags & TDF_RUNNING) == 0,
ef0fdad1 246 ("lwkt_alloc_thread: unexpected NULL or corrupted td"));
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247 TAILQ_REMOVE(&gd->gd_tdfreeq, td, td_threadq);
248 crit_exit_gd(gd);
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249 flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
250 } else {
37af14fe 251 crit_exit_gd(gd);
05220613 252#ifdef _KERNEL
ef0fdad1 253 td = zalloc(thread_zone);
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254#else
255 td = malloc(sizeof(struct thread));
256#endif
ef0fdad1 257 td->td_kstack = NULL;
f470d0c8 258 td->td_kstack_size = 0;
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259 flags |= TDF_ALLOCATED_THREAD;
260 }
261 }
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262 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
263 if (flags & TDF_ALLOCATED_STACK) {
a9e5ae82 264#ifdef _KERNEL
f470d0c8 265 kmem_free(kernel_map, (vm_offset_t)stack, td->td_kstack_size);
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266#else
267 libcaps_free_stack(stack, td->td_kstack_size);
268#endif
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269 stack = NULL;
270 }
271 }
272 if (stack == NULL) {
05220613 273#ifdef _KERNEL
f470d0c8 274 stack = (void *)kmem_alloc(kernel_map, stksize);
05220613 275#else
f470d0c8 276 stack = libcaps_alloc_stack(stksize);
05220613 277#endif
ef0fdad1 278 flags |= TDF_ALLOCATED_STACK;
99df837e 279 }
75cdbe6c 280 if (cpu < 0)
f470d0c8 281 lwkt_init_thread(td, stack, stksize, flags, mycpu);
75cdbe6c 282 else
f470d0c8 283 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 284 return(td);
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285}
286
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287#ifdef _KERNEL
288
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289/*
290 * Initialize a preexisting thread structure. This function is used by
291 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
292 *
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293 * All threads start out in a critical section at a priority of
294 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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295 * appropriate. This function may send an IPI message when the
296 * requested cpu is not the current cpu and consequently gd_tdallq may
297 * not be initialized synchronously from the point of view of the originating
298 * cpu.
299 *
300 * NOTE! we have to be careful in regards to creating threads for other cpus
301 * if SMP has not yet been activated.
7d0bac62 302 */
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303#ifdef SMP
304
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305static void
306lwkt_init_thread_remote(void *arg)
307{
308 thread_t td = arg;
309
310 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
311}
312
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313#endif
314
7d0bac62 315void
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316lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
317 struct globaldata *gd)
7d0bac62 318{
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319 globaldata_t mygd = mycpu;
320
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321 bzero(td, sizeof(struct thread));
322 td->td_kstack = stack;
f470d0c8 323 td->td_kstack_size = stksize;
99df837e 324 td->td_flags |= flags;
26a0694b 325 td->td_gd = gd;
f8c3996b 326 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT;
c95cd171 327 lwkt_initport(&td->td_msgport, td);
99df837e 328 pmap_init_thread(td);
0f7a3396 329#ifdef SMP
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330 /*
331 * Normally initializing a thread for a remote cpu requires sending an
332 * IPI. However, the idlethread is setup before the other cpus are
333 * activated so we have to treat it as a special case. XXX manipulation
334 * of gd_tdallq requires the BGL.
335 */
336 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 337 crit_enter_gd(mygd);
75cdbe6c 338 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 339 crit_exit_gd(mygd);
75cdbe6c 340 } else {
2db3b277 341 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 342 }
0f7a3396 343#else
37af14fe 344 crit_enter_gd(mygd);
0f7a3396 345 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 346 crit_exit_gd(mygd);
0f7a3396 347#endif
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348}
349
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350#endif /* _KERNEL */
351
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352void
353lwkt_set_comm(thread_t td, const char *ctl, ...)
354{
e2565a42 355 __va_list va;
73e4f7b9 356
e2565a42 357 __va_start(va, ctl);
73e4f7b9 358 vsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 359 __va_end(va);
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360}
361
99df837e 362void
73e4f7b9 363lwkt_hold(thread_t td)
99df837e 364{
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365 ++td->td_refs;
366}
367
368void
369lwkt_rele(thread_t td)
370{
371 KKASSERT(td->td_refs > 0);
372 --td->td_refs;
373}
374
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375#ifdef _KERNEL
376
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377void
378lwkt_wait_free(thread_t td)
379{
380 while (td->td_refs)
377d4740 381 tsleep(td, 0, "tdreap", hz);
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382}
383
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384#endif
385
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386void
387lwkt_free_thread(thread_t td)
388{
389 struct globaldata *gd = mycpu;
390
d9eea1a5 391 KASSERT((td->td_flags & TDF_RUNNING) == 0,
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392 ("lwkt_free_thread: did not exit! %p", td));
393
37af14fe 394 crit_enter_gd(gd);
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395 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
396 if (gd->gd_tdfreecount < CACHE_NTHREADS &&
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397 (td->td_flags & TDF_ALLOCATED_THREAD)
398 ) {
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399 ++gd->gd_tdfreecount;
400 TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq);
37af14fe 401 crit_exit_gd(gd);
99df837e 402 } else {
37af14fe 403 crit_exit_gd(gd);
99df837e 404 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
05220613 405#ifdef _KERNEL
f470d0c8 406 kmem_free(kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
05220613 407#else
f470d0c8 408 libcaps_free_stack(td->td_kstack, td->td_kstack_size);
05220613 409#endif
73e4f7b9 410 /* gd invalid */
99df837e 411 td->td_kstack = NULL;
f470d0c8 412 td->td_kstack_size = 0;
99df837e 413 }
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414 if (td->td_flags & TDF_ALLOCATED_THREAD) {
415#ifdef _KERNEL
99df837e 416 zfree(thread_zone, td);
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417#else
418 free(td);
419#endif
420 }
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421 }
422}
423
424
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425/*
426 * Switch to the next runnable lwkt. If no LWKTs are runnable then
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427 * switch to the idlethread. Switching must occur within a critical
428 * section to avoid races with the scheduling queue.
429 *
430 * We always have full control over our cpu's run queue. Other cpus
431 * that wish to manipulate our queue must use the cpu_*msg() calls to
432 * talk to our cpu, so a critical section is all that is needed and
433 * the result is very, very fast thread switching.
434 *
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435 * The LWKT scheduler uses a fixed priority model and round-robins at
436 * each priority level. User process scheduling is a totally
437 * different beast and LWKT priorities should not be confused with
438 * user process priorities.
f1d1c3fa 439 *
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440 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch()
441 * cleans it up. Note that the td_switch() function cannot do anything that
442 * requires the MP lock since the MP lock will have already been setup for
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443 * the target thread (not the current thread). It's nice to have a scheduler
444 * that does not need the MP lock to work because it allows us to do some
445 * really cool high-performance MP lock optimizations.
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446 *
447 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
448 * is not called by the current thread in the preemption case, only when
449 * the preempting thread blocks (in order to return to the original thread).
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450 */
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
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461 /*
462 * We had better not be holding any spin locks.
463 */
464 KKASSERT(td->td_spinlocks == 0);
465
46a3f46d 466 /*
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467 * Switching from within a 'fast' (non thread switched) interrupt or IPI
468 * is illegal. However, we may have to do it anyway if we hit a fatal
469 * kernel trap or we have paniced.
470 *
471 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 472 */
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473 if (gd->gd_intr_nesting_level) {
474 int savegdnest;
475 int savegdtrap;
476
477 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) {
478 panic("lwkt_switch: cannot switch from within "
479 "a fast interrupt, yet, td %p\n", td);
480 } else {
481 savegdnest = gd->gd_intr_nesting_level;
482 savegdtrap = gd->gd_trap_nesting_level;
483 gd->gd_intr_nesting_level = 0;
484 gd->gd_trap_nesting_level = 0;
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485 if ((td->td_flags & TDF_PANICWARN) == 0) {
486 td->td_flags |= TDF_PANICWARN;
487 printf("Warning: thread switch from interrupt or IPI, "
488 "thread %p (%s)\n", td, td->td_comm);
489#ifdef DDB
490 db_print_backtrace();
491#endif
492 }
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493 lwkt_switch();
494 gd->gd_intr_nesting_level = savegdnest;
495 gd->gd_trap_nesting_level = savegdtrap;
496 return;
497 }
96728c05 498 }
ef0fdad1 499
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500 /*
501 * Passive release (used to transition from user to kernel mode
502 * when we block or switch rather then when we enter the kernel).
503 * This function is NOT called if we are switching into a preemption
504 * or returning from a preemption. Typically this causes us to lose
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505 * our current process designation (if we have one) and become a true
506 * LWKT thread, and may also hand the current process designation to
507 * another process and schedule thread.
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508 */
509 if (td->td_release)
510 td->td_release(td);
511
37af14fe 512 crit_enter_gd(gd);
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513
514#ifdef SMP
515 /*
516 * td_mpcount cannot be used to determine if we currently hold the
517 * MP lock because get_mplock() will increment it prior to attempting
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518 * to get the lock, and switch out if it can't. Our ownership of
519 * the actual lock will remain stable while we are in a critical section
520 * (but, of course, another cpu may own or release the lock so the
521 * actual value of mp_lock is not stable).
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522 */
523 mpheld = MP_LOCK_HELD();
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524#ifdef INVARIANTS
525 if (td->td_cscount) {
526 printf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
527 td);
528 if (panic_on_cscount)
529 panic("switching while mastering cpusync");
530 }
531#endif
8a8d5d85 532#endif
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533 if ((ntd = td->td_preempted) != NULL) {
534 /*
535 * We had preempted another thread on this cpu, resume the preempted
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536 * thread. This occurs transparently, whether the preempted thread
537 * was scheduled or not (it may have been preempted after descheduling
8a8d5d85
MD
538 * itself).
539 *
540 * We have to setup the MP lock for the original thread after backing
541 * out the adjustment that was made to curthread when the original
542 * was preempted.
99df837e 543 */
26a0694b 544 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
8a8d5d85 545#ifdef SMP
96728c05 546 if (ntd->td_mpcount && mpheld == 0) {
fc92d4aa 547 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d",
96728c05
MD
548 td, ntd, td->td_mpcount, ntd->td_mpcount);
549 }
8a8d5d85
MD
550 if (ntd->td_mpcount) {
551 td->td_mpcount -= ntd->td_mpcount;
552 KKASSERT(td->td_mpcount >= 0);
553 }
554#endif
26a0694b 555 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
556
557 /*
558 * XXX. The interrupt may have woken a thread up, we need to properly
559 * set the reschedule flag if the originally interrupted thread is at
560 * a lower priority.
561 */
562 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1)
563 need_lwkt_resched();
8a8d5d85 564 /* YYY release mp lock on switchback if original doesn't need it */
8ad65e08 565 } else {
4b5f931b
MD
566 /*
567 * Priority queue / round-robin at each priority. Note that user
568 * processes run at a fixed, low priority and the user process
569 * scheduler deals with interactions between user processes
570 * by scheduling and descheduling them from the LWKT queue as
571 * necessary.
8a8d5d85
MD
572 *
573 * We have to adjust the MP lock for the target thread. If we
574 * need the MP lock and cannot obtain it we try to locate a
41a01a4d
MD
575 * thread that does not need the MP lock. If we cannot, we spin
576 * instead of HLT.
577 *
578 * A similar issue exists for the tokens held by the target thread.
579 * If we cannot obtain ownership of the tokens we cannot immediately
580 * schedule the thread.
581 */
582
583 /*
584 * We are switching threads. If there are any pending requests for
585 * tokens we can satisfy all of them here.
4b5f931b 586 */
41a01a4d
MD
587#ifdef SMP
588 if (gd->gd_tokreqbase)
589 lwkt_drain_token_requests();
590#endif
591
8ec60c3f
MD
592 /*
593 * If an LWKT reschedule was requested, well that is what we are
594 * doing now so clear it.
595 */
596 clear_lwkt_resched();
4b5f931b
MD
597again:
598 if (gd->gd_runqmask) {
599 int nq = bsrl(gd->gd_runqmask);
600 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
601 gd->gd_runqmask &= ~(1 << nq);
602 goto again;
603 }
8a8d5d85 604#ifdef SMP
41a01a4d 605 /*
df6b8ba0
MD
606 * THREAD SELECTION FOR AN SMP MACHINE BUILD
607 *
41a01a4d
MD
608 * If the target needs the MP lock and we couldn't get it,
609 * or if the target is holding tokens and we could not
610 * gain ownership of the tokens, continue looking for a
611 * thread to schedule and spin instead of HLT if we can't.
a453459d
MD
612 *
613 * NOTE: the mpheld variable invalid after this conditional, it
614 * can change due to both cpu_try_mplock() returning success
615 * AND interactions in lwkt_chktokens() due to the fact that
616 * we are trying to check the mpcount of a thread other then
617 * the current thread. Because of this, if the current thread
618 * is not holding td_mpcount, an IPI indirectly run via
619 * lwkt_chktokens() can obtain and release the MP lock and
620 * cause the core MP lock to be released.
41a01a4d
MD
621 */
622 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) ||
623 (ntd->td_toks && lwkt_chktokens(ntd) == 0)
624 ) {
8a8d5d85 625 u_int32_t rqmask = gd->gd_runqmask;
a453459d
MD
626
627 mpheld = MP_LOCK_HELD();
628 ntd = NULL;
8a8d5d85
MD
629 while (rqmask) {
630 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) {
38717797 631 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) {
a453459d 632 /* spinning due to MP lock being held */
38717797 633#ifdef INVARIANTS
a453459d 634 ++mplock_contention_count;
38717797 635#endif
a453459d 636 /* mplock still not held, 'mpheld' still valid */
41a01a4d 637 continue;
38717797 638 }
a453459d
MD
639
640 /*
641 * mpheld state invalid after chktokens call returns
642 * failure, but the variable is only needed for
643 * the loop.
644 */
38717797 645 if (ntd->td_toks && !lwkt_chktokens(ntd)) {
a453459d 646 /* spinning due to token contention */
38717797 647#ifdef INVARIANTS
a453459d 648 ++token_contention_count;
38717797 649#endif
a453459d 650 mpheld = MP_LOCK_HELD();
41a01a4d 651 continue;
38717797 652 }
41a01a4d 653 break;
8a8d5d85
MD
654 }
655 if (ntd)
656 break;
657 rqmask &= ~(1 << nq);
658 nq = bsrl(rqmask);
659 }
660 if (ntd == NULL) {
a2a5ad0d
MD
661 ntd = &gd->gd_idlethread;
662 ntd->td_flags |= TDF_IDLE_NOHLT;
df6b8ba0 663 goto using_idle_thread;
8a8d5d85 664 } else {
344ad853 665 ++gd->gd_cnt.v_swtch;
8a8d5d85
MD
666 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
667 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
668 }
669 } else {
344ad853 670 ++gd->gd_cnt.v_swtch;
8a8d5d85
MD
671 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
672 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
673 }
674#else
df6b8ba0
MD
675 /*
676 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to
677 * worry about tokens or the BGL.
678 */
344ad853 679 ++gd->gd_cnt.v_swtch;
4b5f931b
MD
680 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
681 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
8a8d5d85 682#endif
4b5f931b 683 } else {
3c23a41a 684 /*
60f945af
MD
685 * We have nothing to run but only let the idle loop halt
686 * the cpu if there are no pending interrupts.
3c23a41a 687 */
a2a5ad0d 688 ntd = &gd->gd_idlethread;
60f945af 689 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
3c23a41a 690 ntd->td_flags |= TDF_IDLE_NOHLT;
a453459d 691#ifdef SMP
df6b8ba0
MD
692using_idle_thread:
693 /*
694 * The idle thread should not be holding the MP lock unless we
695 * are trapping in the kernel or in a panic. Since we select the
696 * idle thread unconditionally when no other thread is available,
697 * if the MP lock is desired during a panic or kernel trap, we
698 * have to loop in the scheduler until we get it.
699 */
700 if (ntd->td_mpcount) {
701 mpheld = MP_LOCK_HELD();
702 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
703 panic("Idle thread %p was holding the BGL!", ntd);
704 else if (mpheld == 0)
705 goto again;
706 }
a453459d 707#endif
4b5f931b 708 }
f1d1c3fa 709 }
26a0694b
MD
710 KASSERT(ntd->td_pri >= TDPRI_CRIT,
711 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
8a8d5d85
MD
712
713 /*
714 * Do the actual switch. If the new target does not need the MP lock
715 * and we are holding it, release the MP lock. If the new target requires
716 * the MP lock we have already acquired it for the target.
717 */
718#ifdef SMP
719 if (ntd->td_mpcount == 0 ) {
720 if (MP_LOCK_HELD())
721 cpu_rel_mplock();
722 } else {
a453459d 723 ASSERT_MP_LOCK_HELD(ntd);
8a8d5d85
MD
724 }
725#endif
94f6d86e
MD
726 if (td != ntd) {
727 ++switch_count;
f1d1c3fa 728 td->td_switch(ntd);
94f6d86e 729 }
37af14fe
MD
730 /* NOTE: current cpu may have changed after switch */
731 crit_exit_quick(td);
8ad65e08
MD
732}
733
b68b7282 734/*
96728c05
MD
735 * Request that the target thread preempt the current thread. Preemption
736 * only works under a specific set of conditions:
b68b7282 737 *
96728c05
MD
738 * - We are not preempting ourselves
739 * - The target thread is owned by the current cpu
740 * - We are not currently being preempted
741 * - The target is not currently being preempted
742 * - We are able to satisfy the target's MP lock requirements (if any).
743 *
744 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
745 * this is called via lwkt_schedule() through the td_preemptable callback.
746 * critpri is the managed critical priority that we should ignore in order
747 * to determine whether preemption is possible (aka usually just the crit
748 * priority of lwkt_schedule() itself).
b68b7282 749 *
26a0694b
MD
750 * XXX at the moment we run the target thread in a critical section during
751 * the preemption in order to prevent the target from taking interrupts
752 * that *WE* can't. Preemption is strictly limited to interrupt threads
753 * and interrupt-like threads, outside of a critical section, and the
754 * preempted source thread will be resumed the instant the target blocks
755 * whether or not the source is scheduled (i.e. preemption is supposed to
756 * be as transparent as possible).
4b5f931b 757 *
8a8d5d85
MD
758 * The target thread inherits our MP count (added to its own) for the
759 * duration of the preemption in order to preserve the atomicy of the
96728c05
MD
760 * MP lock during the preemption. Therefore, any preempting targets must be
761 * careful in regards to MP assertions. Note that the MP count may be
71ef2f5c
MD
762 * out of sync with the physical mp_lock, but we do not have to preserve
763 * the original ownership of the lock if it was out of synch (that is, we
764 * can leave it synchronized on return).
b68b7282
MD
765 */
766void
96728c05 767lwkt_preempt(thread_t ntd, int critpri)
b68b7282 768{
46a3f46d 769 struct globaldata *gd = mycpu;
0a3f9b47 770 thread_t td;
8a8d5d85
MD
771#ifdef SMP
772 int mpheld;
57c254db 773 int savecnt;
8a8d5d85 774#endif
b68b7282 775
26a0694b 776 /*
96728c05
MD
777 * The caller has put us in a critical section. We can only preempt
778 * if the caller of the caller was not in a critical section (basically
0a3f9b47 779 * a local interrupt), as determined by the 'critpri' parameter.
96728c05
MD
780 *
781 * YYY The target thread must be in a critical section (else it must
782 * inherit our critical section? I dunno yet).
41a01a4d
MD
783 *
784 * Any tokens held by the target may not be held by thread(s) being
785 * preempted. We take the easy way out and do not preempt if
786 * the target is holding tokens.
0a3f9b47
MD
787 *
788 * Set need_lwkt_resched() unconditionally for now YYY.
26a0694b
MD
789 */
790 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 791
0a3f9b47 792 td = gd->gd_curthread;
0a3f9b47 793 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) {
57c254db
MD
794 ++preempt_miss;
795 return;
796 }
96728c05
MD
797 if ((td->td_pri & ~TDPRI_MASK) > critpri) {
798 ++preempt_miss;
8ec60c3f 799 need_lwkt_resched();
96728c05
MD
800 return;
801 }
802#ifdef SMP
46a3f46d 803 if (ntd->td_gd != gd) {
96728c05 804 ++preempt_miss;
8ec60c3f 805 need_lwkt_resched();
96728c05
MD
806 return;
807 }
808#endif
41a01a4d
MD
809 /*
810 * Take the easy way out and do not preempt if the target is holding
811 * one or more tokens. We could test whether the thread(s) being
812 * preempted interlock against the target thread's tokens and whether
813 * we can get all the target thread's tokens, but this situation
814 * should not occur very often so its easier to simply not preempt.
815 */
816 if (ntd->td_toks != NULL) {
817 ++preempt_miss;
8ec60c3f 818 need_lwkt_resched();
41a01a4d
MD
819 return;
820 }
26a0694b
MD
821 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
822 ++preempt_weird;
8ec60c3f 823 need_lwkt_resched();
26a0694b
MD
824 return;
825 }
826 if (ntd->td_preempted) {
4b5f931b 827 ++preempt_hit;
8ec60c3f 828 need_lwkt_resched();
26a0694b 829 return;
b68b7282 830 }
8a8d5d85 831#ifdef SMP
a2a5ad0d
MD
832 /*
833 * note: an interrupt might have occured just as we were transitioning
71ef2f5c
MD
834 * to or from the MP lock. In this case td_mpcount will be pre-disposed
835 * (non-zero) but not actually synchronized with the actual state of the
836 * lock. We can use it to imply an MP lock requirement for the
837 * preemption but we cannot use it to test whether we hold the MP lock
838 * or not.
a2a5ad0d 839 */
96728c05 840 savecnt = td->td_mpcount;
71ef2f5c 841 mpheld = MP_LOCK_HELD();
8a8d5d85
MD
842 ntd->td_mpcount += td->td_mpcount;
843 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) {
844 ntd->td_mpcount -= td->td_mpcount;
845 ++preempt_miss;
8ec60c3f 846 need_lwkt_resched();
8a8d5d85
MD
847 return;
848 }
849#endif
26a0694b 850
8ec60c3f
MD
851 /*
852 * Since we are able to preempt the current thread, there is no need to
853 * call need_lwkt_resched().
854 */
26a0694b
MD
855 ++preempt_hit;
856 ntd->td_preempted = td;
857 td->td_flags |= TDF_PREEMPT_LOCK;
858 td->td_switch(ntd);
859 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
96728c05
MD
860#ifdef SMP
861 KKASSERT(savecnt == td->td_mpcount);
71ef2f5c
MD
862 mpheld = MP_LOCK_HELD();
863 if (mpheld && td->td_mpcount == 0)
96728c05 864 cpu_rel_mplock();
71ef2f5c 865 else if (mpheld == 0 && td->td_mpcount)
96728c05
MD
866 panic("lwkt_preempt(): MP lock was not held through");
867#endif
26a0694b
MD
868 ntd->td_preempted = NULL;
869 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
870}
871
f1d1c3fa
MD
872/*
873 * Yield our thread while higher priority threads are pending. This is
874 * typically called when we leave a critical section but it can be safely
875 * called while we are in a critical section.
876 *
877 * This function will not generally yield to equal priority threads but it
878 * can occur as a side effect. Note that lwkt_switch() is called from
46a3f46d 879 * inside the critical section to prevent its own crit_exit() from reentering
f1d1c3fa
MD
880 * lwkt_yield_quick().
881 *
235957ed 882 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint
ef0fdad1
MD
883 * came along but was blocked and made pending.
884 *
f1d1c3fa
MD
885 * (self contained on a per cpu basis)
886 */
887void
888lwkt_yield_quick(void)
889{
7966cb69
MD
890 globaldata_t gd = mycpu;
891 thread_t td = gd->gd_curthread;
ef0fdad1 892
a2a5ad0d 893 /*
235957ed 894 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear
a2a5ad0d
MD
895 * it with a non-zero cpl then we might not wind up calling splz after
896 * a task switch when the critical section is exited even though the
46a3f46d 897 * new task could accept the interrupt.
a2a5ad0d
MD
898 *
899 * XXX from crit_exit() only called after last crit section is released.
900 * If called directly will run splz() even if in a critical section.
46a3f46d
MD
901 *
902 * td_nest_count prevent deep nesting via splz() or doreti(). Note that
903 * except for this special case, we MUST call splz() here to handle any
904 * pending ints, particularly after we switch, or we might accidently
905 * halt the cpu with interrupts pending.
a2a5ad0d 906 */
46a3f46d 907 if (gd->gd_reqflags && td->td_nest_count < 2)
f1d1c3fa 908 splz();
f1d1c3fa
MD
909
910 /*
911 * YYY enabling will cause wakeup() to task-switch, which really
912 * confused the old 4.x code. This is a good way to simulate
7d0bac62
MD
913 * preemption and MP without actually doing preemption or MP, because a
914 * lot of code assumes that wakeup() does not block.
f1d1c3fa 915 */
46a3f46d
MD
916 if (untimely_switch && td->td_nest_count == 0 &&
917 gd->gd_intr_nesting_level == 0
918 ) {
37af14fe 919 crit_enter_quick(td);
f1d1c3fa
MD
920 /*
921 * YYY temporary hacks until we disassociate the userland scheduler
922 * from the LWKT scheduler.
923 */
924 if (td->td_flags & TDF_RUNQ) {
925 lwkt_switch(); /* will not reenter yield function */
926 } else {
37af14fe 927 lwkt_schedule_self(td); /* make sure we are scheduled */
f1d1c3fa 928 lwkt_switch(); /* will not reenter yield function */
37af14fe 929 lwkt_deschedule_self(td); /* make sure we are descheduled */
f1d1c3fa 930 }
7966cb69 931 crit_exit_noyield(td);
f1d1c3fa 932 }
f1d1c3fa
MD
933}
934
8ad65e08 935/*
f1d1c3fa 936 * This implements a normal yield which, unlike _quick, will yield to equal
235957ed 937 * priority threads as well. Note that gd_reqflags tests will be handled by
f1d1c3fa
MD
938 * the crit_exit() call in lwkt_switch().
939 *
940 * (self contained on a per cpu basis)
8ad65e08
MD
941 */
942void
f1d1c3fa 943lwkt_yield(void)
8ad65e08 944{
37af14fe 945 lwkt_schedule_self(curthread);
f1d1c3fa
MD
946 lwkt_switch();
947}
948
8ad65e08 949/*
f1d1c3fa
MD
950 * Generic schedule. Possibly schedule threads belonging to other cpus and
951 * deal with threads that might be blocked on a wait queue.
952 *
0a3f9b47
MD
953 * We have a little helper inline function which does additional work after
954 * the thread has been enqueued, including dealing with preemption and
955 * setting need_lwkt_resched() (which prevents the kernel from returning
956 * to userland until it has processed higher priority threads).
8ad65e08 957 */
0a3f9b47
MD
958static __inline
959void
8ec60c3f 960_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri)
0a3f9b47
MD
961{
962 if (ntd->td_preemptable) {
963 ntd->td_preemptable(ntd, cpri); /* YYY +token */
8ec60c3f
MD
964 } else if ((ntd->td_flags & TDF_NORESCHED) == 0 &&
965 (ntd->td_pri & TDPRI_MASK) > (gd->gd_curthread->td_pri & TDPRI_MASK)
966 ) {
967 need_lwkt_resched();
0a3f9b47
MD
968 }
969}
970
8ad65e08
MD
971void
972lwkt_schedule(thread_t td)
973{
37af14fe
MD
974 globaldata_t mygd = mycpu;
975
41a01a4d 976 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
37af14fe 977 crit_enter_gd(mygd);
344ad853 978 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
37af14fe 979 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
980 _lwkt_enqueue(td);
981 } else {
982 lwkt_wait_t w;
983
984 /*
985 * If the thread is on a wait list we have to send our scheduling
986 * request to the owner of the wait structure. Otherwise we send
987 * the scheduling request to the cpu owning the thread. Races
988 * are ok, the target will forward the message as necessary (the
989 * message may chase the thread around before it finally gets
990 * acted upon).
991 *
992 * (remember, wait structures use stable storage)
0a3f9b47 993 *
0c453950
MD
994 * NOTE: we have to account for the number of critical sections
995 * under our control when calling _lwkt_schedule_post() so it
996 * can figure out whether preemption is allowed.
997 *
998 * NOTE: The wait structure algorithms are a mess and need to be
999 * rewritten.
1000 *
1001 * NOTE: We cannot safely acquire or release a token, even
1002 * non-blocking, because this routine may be called in the context
1003 * of a thread already holding the token and thus not provide any
1004 * interlock protection. We cannot safely manipulate the td_toks
1005 * list for the same reason. Instead we depend on our critical
1006 * section if the token is owned by our cpu.
f1d1c3fa
MD
1007 */
1008 if ((w = td->td_wait) != NULL) {
0c453950 1009 if (w->wa_token.t_cpu == mygd) {
f1d1c3fa
MD
1010 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
1011 --w->wa_count;
1012 td->td_wait = NULL;
0f7a3396 1013#ifdef SMP
8ec60c3f 1014 if (td->td_gd == mygd) {
f1d1c3fa 1015 _lwkt_enqueue(td);
8ec60c3f 1016 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
f1d1c3fa 1017 } else {
b8a98473 1018 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
f1d1c3fa 1019 }
0f7a3396
MD
1020#else
1021 _lwkt_enqueue(td);
8ec60c3f 1022 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
0f7a3396 1023#endif
f1d1c3fa 1024 } else {
b8a98473
MD
1025#ifdef SMP
1026 lwkt_send_ipiq(w->wa_token.t_cpu, (ipifunc1_t)lwkt_schedule, td);
1027#else
1028 panic("bad token %p", &w->wa_token);
1029#endif
f1d1c3fa
MD
1030 }
1031 } else {
1032 /*
1033 * If the wait structure is NULL and we own the thread, there
1034 * is no race (since we are in a critical section). If we
1035 * do not own the thread there might be a race but the
1036 * target cpu will deal with it.
1037 */
0f7a3396 1038#ifdef SMP
37af14fe 1039 if (td->td_gd == mygd) {
f1d1c3fa 1040 _lwkt_enqueue(td);
8ec60c3f 1041 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
f1d1c3fa 1042 } else {
b8a98473 1043 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
f1d1c3fa 1044 }
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1045#else
1046 _lwkt_enqueue(td);
8ec60c3f 1047 _lwkt_schedule_post(mygd, td, TDPRI_CRIT);
0f7a3396 1048#endif
f1d1c3fa 1049 }
8ad65e08 1050 }
37af14fe 1051 crit_exit_gd(mygd);
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MD
1052}
1053
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1054/*
1055 * Managed acquisition. This code assumes that the MP lock is held for
1056 * the tdallq operation and that the thread has been descheduled from its
1057 * original cpu. We also have to wait for the thread to be entirely switched
1058 * out on its original cpu (this is usually fast enough that we never loop)
1059 * since the LWKT system does not have to hold the MP lock while switching
1060 * and the target may have released it before switching.
1061 */
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1062void
1063lwkt_acquire(thread_t td)
1064{
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1065 globaldata_t gd;
1066 globaldata_t mygd;
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1067
1068 gd = td->td_gd;
37af14fe 1069 mygd = mycpu;
35238fa5 1070 cpu_lfence();
a2a5ad0d 1071 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
d9eea1a5 1072 while (td->td_flags & TDF_RUNNING) /* XXX spin */
35238fa5 1073 cpu_lfence();
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1074 if (gd != mygd) {
1075 crit_enter_gd(mygd);
a2a5ad0d 1076 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); /* protected by BGL */
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1077 td->td_gd = mygd;
1078 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq); /* protected by BGL */
1079 crit_exit_gd(mygd);
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1080 }
1081}
1082
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1083/*
1084 * Generic deschedule. Descheduling threads other then your own should be
1085 * done only in carefully controlled circumstances. Descheduling is
1086 * asynchronous.
1087 *
1088 * This function may block if the cpu has run out of messages.
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1089 */
1090void
1091lwkt_deschedule(thread_t td)
1092{
f1d1c3fa 1093 crit_enter();
b8a98473 1094#ifdef SMP
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1095 if (td == curthread) {
1096 _lwkt_dequeue(td);
1097 } else {
a72187e9 1098 if (td->td_gd == mycpu) {
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1099 _lwkt_dequeue(td);
1100 } else {
b8a98473 1101 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
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1102 }
1103 }
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1104#else
1105 _lwkt_dequeue(td);
1106#endif
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1107 crit_exit();
1108}
1109
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1110/*
1111 * Set the target thread's priority. This routine does not automatically
1112 * switch to a higher priority thread, LWKT threads are not designed for
1113 * continuous priority changes. Yield if you want to switch.
1114 *
1115 * We have to retain the critical section count which uses the high bits
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1116 * of the td_pri field. The specified priority may also indicate zero or
1117 * more critical sections by adding TDPRI_CRIT*N.
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1118 *
1119 * Note that we requeue the thread whether it winds up on a different runq
1120 * or not. uio_yield() depends on this and the routine is not normally
1121 * called with the same priority otherwise.
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1122 */
1123void
1124lwkt_setpri(thread_t td, int pri)
1125{
26a0694b 1126 KKASSERT(pri >= 0);
a72187e9 1127 KKASSERT(td->td_gd == mycpu);
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1128 crit_enter();
1129 if (td->td_flags & TDF_RUNQ) {
1130 _lwkt_dequeue(td);
1131 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1132 _lwkt_enqueue(td);
1133 } else {
1134 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1135 }
1136 crit_exit();
1137}
1138
1139void
1140lwkt_setpri_self(int pri)
1141{
1142 thread_t td = curthread;
1143
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1144 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1145 crit_enter();
1146 if (td->td_flags & TDF_RUNQ) {
1147 _lwkt_dequeue(td);
1148 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1149 _lwkt_enqueue(td);
1150 } else {
1151 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1152 }
1153 crit_exit();
1154}
1155
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1156/*
1157 * Determine if there is a runnable thread at a higher priority then
1158 * the current thread. lwkt_setpri() does not check this automatically.
1159 * Return 1 if there is, 0 if there isn't.
1160 *
1161 * Example: if bit 31 of runqmask is set and the current thread is priority
1162 * 30, then we wind up checking the mask: 0x80000000 against 0x7fffffff.
1163 *
1164 * If nq reaches 31 the shift operation will overflow to 0 and we will wind
1165 * up comparing against 0xffffffff, a comparison that will always be false.
1166 */
1167int
1168lwkt_checkpri_self(void)
1169{
1170 globaldata_t gd = mycpu;
1171 thread_t td = gd->gd_curthread;
1172 int nq = td->td_pri & TDPRI_MASK;
1173
1174 while (gd->gd_runqmask > (__uint32_t)(2 << nq) - 1) {
1175 if (TAILQ_FIRST(&gd->gd_tdrunq[nq + 1]))
1176 return(1);
1177 ++nq;
1178 }
1179 return(0);
1180}
1181
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1182/*
1183 * Migrate the current thread to the specified cpu. The BGL must be held
1184 * (for the gd_tdallq manipulation XXX). This is accomplished by
1185 * descheduling ourselves from the current cpu, moving our thread to the
1186 * tdallq of the target cpu, IPI messaging the target cpu, and switching out.
1187 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1188 */
3d28ff59 1189#ifdef SMP
5d21b981 1190static void lwkt_setcpu_remote(void *arg);
3d28ff59 1191#endif
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1192
1193void
1194lwkt_setcpu_self(globaldata_t rgd)
1195{
1196#ifdef SMP
1197 thread_t td = curthread;
1198
1199 if (td->td_gd != rgd) {
1200 crit_enter_quick(td);
1201 td->td_flags |= TDF_MIGRATING;
1202 lwkt_deschedule_self(td);
1203 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq); /* protected by BGL */
1204 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq); /* protected by BGL */
b8a98473 1205 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td);
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1206 lwkt_switch();
1207 /* we are now on the target cpu */
1208 crit_exit_quick(td);
1209 }
1210#endif
1211}
1212
1213/*
1214 * Remote IPI for cpu migration (called while in a critical section so we
1215 * do not have to enter another one). The thread has already been moved to
1216 * our cpu's allq, but we must wait for the thread to be completely switched
1217 * out on the originating cpu before we schedule it on ours or the stack
1218 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD
1219 * change to main memory.
1220 *
1221 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races
1222 * against wakeups. It is best if this interface is used only when there
1223 * are no pending events that might try to schedule the thread.
1224 */
3d28ff59 1225#ifdef SMP
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1226static void
1227lwkt_setcpu_remote(void *arg)
1228{
1229 thread_t td = arg;
1230 globaldata_t gd = mycpu;
1231
1232 while (td->td_flags & TDF_RUNNING)
35238fa5 1233 cpu_lfence();
5d21b981 1234 td->td_gd = gd;
35238fa5 1235 cpu_sfence();
5d21b981 1236 td->td_flags &= ~TDF_MIGRATING;
344ad853 1237 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
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MD
1238 _lwkt_enqueue(td);
1239}
3d28ff59 1240#endif
5d21b981 1241
553ea3c8 1242struct lwp *
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MD
1243lwkt_preempted_proc(void)
1244{
73e4f7b9 1245 thread_t td = curthread;
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1246 while (td->td_preempted)
1247 td = td->td_preempted;
553ea3c8 1248 return(td->td_lwp);
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MD
1249}
1250
f1d1c3fa 1251/*
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1252 * Block on the specified wait queue until signaled. A generation number
1253 * must be supplied to interlock the wait queue. The function will
1254 * return immediately if the generation number does not match the wait
1255 * structure's generation number.
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MD
1256 */
1257void
ae8050a4 1258lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen)
f1d1c3fa
MD
1259{
1260 thread_t td = curthread;
41a01a4d 1261 lwkt_tokref ilock;
f1d1c3fa 1262
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MD
1263 lwkt_gettoken(&ilock, &w->wa_token);
1264 crit_enter();
ae8050a4 1265 if (w->wa_gen == *gen) {
f1d1c3fa 1266 _lwkt_dequeue(td);
344ad853 1267 td->td_flags |= TDF_BLOCKQ;
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MD
1268 TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq);
1269 ++w->wa_count;
1270 td->td_wait = w;
ae8050a4 1271 td->td_wmesg = wmesg;
f1d1c3fa 1272 lwkt_switch();
344ad853
MD
1273 KKASSERT((td->td_flags & TDF_BLOCKQ) == 0);
1274 td->td_wmesg = NULL;
8ad65e08 1275 }
41a01a4d 1276 crit_exit();
ae8050a4 1277 *gen = w->wa_gen;
41a01a4d 1278 lwkt_reltoken(&ilock);
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MD
1279}
1280
1281/*
1282 * Signal a wait queue. We gain ownership of the wait queue in order to
1283 * signal it. Once a thread is removed from the wait queue we have to
1284 * deal with the cpu owning the thread.
1285 *
1286 * Note: alternatively we could message the target cpu owning the wait
1287 * queue. YYY implement as sysctl.
1288 */
1289void
ece04fd0 1290lwkt_signal(lwkt_wait_t w, int count)
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MD
1291{
1292 thread_t td;
41a01a4d 1293 lwkt_tokref ilock;
f1d1c3fa 1294
41a01a4d 1295 lwkt_gettoken(&ilock, &w->wa_token);
f1d1c3fa 1296 ++w->wa_gen;
41a01a4d 1297 crit_enter();
ece04fd0
MD
1298 if (count < 0)
1299 count = w->wa_count;
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MD
1300 while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) {
1301 --count;
1302 --w->wa_count;
344ad853 1303 KKASSERT(td->td_flags & TDF_BLOCKQ);
f1d1c3fa 1304 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
344ad853 1305 td->td_flags &= ~TDF_BLOCKQ;
f1d1c3fa 1306 td->td_wait = NULL;
344ad853 1307 KKASSERT(td->td_proc == NULL || (td->td_proc->p_flag & P_ONRUNQ) == 0);
b8a98473 1308#ifdef SMP
a72187e9 1309 if (td->td_gd == mycpu) {
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MD
1310 _lwkt_enqueue(td);
1311 } else {
b8a98473 1312 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_schedule, td);
f1d1c3fa 1313 }
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MD
1314#else
1315 _lwkt_enqueue(td);
1316#endif
f1d1c3fa 1317 }
41a01a4d
MD
1318 crit_exit();
1319 lwkt_reltoken(&ilock);
f1d1c3fa
MD
1320}
1321
99df837e
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1322/*
1323 * Create a kernel process/thread/whatever. It shares it's address space
1324 * with proc0 - ie: kernel only.
1325 *
365fa13f
MD
1326 * NOTE! By default new threads are created with the MP lock held. A
1327 * thread which does not require the MP lock should release it by calling
1328 * rel_mplock() at the start of the new thread.
99df837e
MD
1329 */
1330int
1331lwkt_create(void (*func)(void *), void *arg,
75cdbe6c 1332 struct thread **tdp, thread_t template, int tdflags, int cpu,
ef0fdad1 1333 const char *fmt, ...)
99df837e 1334{
73e4f7b9 1335 thread_t td;
e2565a42 1336 __va_list ap;
99df837e 1337
f470d0c8 1338 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu);
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MD
1339 if (tdp)
1340 *tdp = td;
709799ea 1341 cpu_set_thread_handler(td, lwkt_exit, func, arg);
ef0fdad1 1342 td->td_flags |= TDF_VERBOSE | tdflags;
8a8d5d85 1343#ifdef SMP
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MD
1344 if (td->td_flags & TDF_MPSAFE)
1345 td->td_mpcount = 0;
1346 else
1347 td->td_mpcount = 1;
8a8d5d85 1348#endif
99df837e
MD
1349
1350 /*
1351 * Set up arg0 for 'ps' etc
1352 */
e2565a42 1353 __va_start(ap, fmt);
99df837e 1354 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1355 __va_end(ap);
99df837e
MD
1356
1357 /*
1358 * Schedule the thread to run
1359 */
ef0fdad1
MD
1360 if ((td->td_flags & TDF_STOPREQ) == 0)
1361 lwkt_schedule(td);
1362 else
1363 td->td_flags &= ~TDF_STOPREQ;
99df837e
MD
1364 return 0;
1365}
1366
2d93b37a 1367/*
2d93b37a
MD
1368 * kthread_* is specific to the kernel and is not needed by userland.
1369 */
1370#ifdef _KERNEL
1371
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1372/*
1373 * Destroy an LWKT thread. Warning! This function is not called when
1374 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1375 * uses a different reaping mechanism.
1376 */
1377void
1378lwkt_exit(void)
1379{
1380 thread_t td = curthread;
8826f33a 1381 globaldata_t gd;
99df837e
MD
1382
1383 if (td->td_flags & TDF_VERBOSE)
1384 printf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1385 caps_exit(td);
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MD
1386 crit_enter_quick(td);
1387 lwkt_deschedule_self(td);
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MD
1388 gd = mycpu;
1389 KKASSERT(gd == td->td_gd);
1390 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1391 if (td->td_flags & TDF_ALLOCATED_THREAD) {
1392 ++gd->gd_tdfreecount;
1393 TAILQ_INSERT_TAIL(&gd->gd_tdfreeq, td, td_threadq);
1394 }
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MD
1395 cpu_thread_exit();
1396}
1397
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MD
1398#endif /* _KERNEL */
1399
1400void
1401crit_panic(void)
1402{
1403 thread_t td = curthread;
1404 int lpri = td->td_pri;
1405
1406 td->td_pri = 0;
1407 panic("td_pri is/would-go negative! %p %d", td, lpri);
1408}
1409
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MD
1410#ifdef SMP
1411
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MD
1412/*
1413 * Called from debugger/panic on cpus which have been stopped. We must still
1414 * process the IPIQ while stopped, even if we were stopped while in a critical
1415 * section (XXX).
1416 *
1417 * If we are dumping also try to process any pending interrupts. This may
1418 * or may not work depending on the state of the cpu at the point it was
1419 * stopped.
1420 */
1421void
1422lwkt_smp_stopped(void)
1423{
1424 globaldata_t gd = mycpu;
1425
1426 crit_enter_gd(gd);
1427 if (dumping) {
1428 lwkt_process_ipiq();
1429 splz();
1430 } else {
1431 lwkt_process_ipiq();
1432 }
1433 crit_exit_gd(gd);
1434}
1435
d165e668 1436#endif