kernel - SWAP CACHE part 15/many - Correct bug in vm.swapcache.maxfilesize
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
8c10bfcf 2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
60f60350 3 *
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4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
60f60350 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:
60f60350 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.
60f60350 20 *
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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.
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33 */
34
35/*
36 * Each cpu in a system has its own self-contained light weight kernel
37 * thread scheduler, which means that generally speaking we only need
38 * to use a critical section to avoid problems. Foreign thread
39 * scheduling is queued via (async) IPIs.
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40 */
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/kernel.h>
45#include <sys/proc.h>
46#include <sys/rtprio.h>
47#include <sys/queue.h>
7d0bac62 48#include <sys/sysctl.h>
99df837e 49#include <sys/kthread.h>
f1d1c3fa 50#include <machine/cpu.h>
99df837e 51#include <sys/lock.h>
f6bf3af1 52#include <sys/caps.h>
9d265729 53#include <sys/spinlock.h>
57aa743c 54#include <sys/ktr.h>
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55
56#include <sys/thread2.h>
57#include <sys/spinlock2.h>
684a93c4 58#include <sys/mplock2.h>
f1d1c3fa 59
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60#include <vm/vm.h>
61#include <vm/vm_param.h>
62#include <vm/vm_kern.h>
63#include <vm/vm_object.h>
64#include <vm/vm_page.h>
65#include <vm/vm_map.h>
66#include <vm/vm_pager.h>
67#include <vm/vm_extern.h>
7d0bac62 68
99df837e 69#include <machine/stdarg.h>
96728c05 70#include <machine/smp.h>
99df837e 71
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72#if !defined(KTR_CTXSW)
73#define KTR_CTXSW KTR_ALL
74#endif
75KTR_INFO_MASTER(ctxsw);
76KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "sw %p > %p", 2 * sizeof(struct thread *));
77KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "pre %p > %p", 2 * sizeof(struct thread *));
1541028a 78
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79static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
80
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81#ifdef INVARIANTS
82static int panic_on_cscount = 0;
83#endif
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84static __int64_t switch_count = 0;
85static __int64_t preempt_hit = 0;
86static __int64_t preempt_miss = 0;
87static __int64_t preempt_weird = 0;
f64b567c 88static __int64_t token_contention_count __debugvar = 0;
fb0f29c4 89static int lwkt_use_spin_port;
40aaf5fc 90static struct objcache *thread_cache;
05220613 91
88ebb169 92#ifdef SMP
e381e77c 93static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
88ebb169 94#endif
e381e77c 95
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96extern void cpu_heavy_restore(void);
97extern void cpu_lwkt_restore(void);
98extern void cpu_kthread_restore(void);
99extern void cpu_idle_restore(void);
100
b2b3ffcd 101#ifdef __x86_64__
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102
103static int
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104jg_tos_ok(struct thread *td)
105{
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106 void *tos;
107 int tos_ok;
108
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109 if (td == NULL) {
110 return 1;
111 }
112 KKASSERT(td->td_sp != NULL);
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113 tos = ((void **)td->td_sp)[0];
114 tos_ok = 0;
115 if ((tos == cpu_heavy_restore) || (tos == cpu_lwkt_restore) ||
116 (tos == cpu_kthread_restore) || (tos == cpu_idle_restore)) {
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117 tos_ok = 1;
118 }
119 return tos_ok;
120}
121
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122#endif
123
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124/*
125 * We can make all thread ports use the spin backend instead of the thread
126 * backend. This should only be set to debug the spin backend.
127 */
128TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
129
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130#ifdef INVARIANTS
131SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, "");
132#endif
4b5f931b 133SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
4b5f931b 134SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, "");
4b5f931b 135SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, "");
26a0694b 136SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
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137#ifdef INVARIANTS
138SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW,
139 &token_contention_count, 0, "spinning due to token contention");
38717797 140#endif
05220613 141
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142/*
143 * These helper procedures handle the runq, they can only be called from
144 * within a critical section.
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145 *
146 * WARNING! Prior to SMP being brought up it is possible to enqueue and
147 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
148 * instead of 'mycpu' when referencing the globaldata structure. Once
149 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 150 */
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151static __inline
152void
153_lwkt_dequeue(thread_t td)
154{
155 if (td->td_flags & TDF_RUNQ) {
4b5f931b 156 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 157 struct globaldata *gd = td->td_gd;
4b5f931b 158
f1d1c3fa 159 td->td_flags &= ~TDF_RUNQ;
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160 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq);
161 /* runqmask is passively cleaned up by the switcher */
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162 }
163}
164
165static __inline
166void
167_lwkt_enqueue(thread_t td)
168{
7f5d7ed7 169 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
4b5f931b 170 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 171 struct globaldata *gd = td->td_gd;
4b5f931b 172
f1d1c3fa 173 td->td_flags |= TDF_RUNQ;
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174 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq);
175 gd->gd_runqmask |= 1 << nq;
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176 }
177}
8ad65e08 178
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179static __boolean_t
180_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
181{
182 struct thread *td = (struct thread *)obj;
183
184 td->td_kstack = NULL;
185 td->td_kstack_size = 0;
186 td->td_flags = TDF_ALLOCATED_THREAD;
187 return (1);
188}
189
190static void
191_lwkt_thread_dtor(void *obj, void *privdata)
192{
193 struct thread *td = (struct thread *)obj;
194
195 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
196 ("_lwkt_thread_dtor: not allocated from objcache"));
197 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
198 td->td_kstack_size > 0,
199 ("_lwkt_thread_dtor: corrupted stack"));
200 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
201}
202
203/*
204 * Initialize the lwkt s/system.
205 */
206void
207lwkt_init(void)
208{
209 /* An objcache has 2 magazines per CPU so divide cache size by 2. */
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210 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread),
211 NULL, CACHE_NTHREADS/2,
212 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
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213}
214
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215/*
216 * Schedule a thread to run. As the current thread we can always safely
217 * schedule ourselves, and a shortcut procedure is provided for that
218 * function.
219 *
220 * (non-blocking, self contained on a per cpu basis)
221 */
222void
223lwkt_schedule_self(thread_t td)
224{
225 crit_enter_quick(td);
37af14fe 226 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
9388413d 227 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 228 _lwkt_enqueue(td);
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229 crit_exit_quick(td);
230}
231
232/*
233 * Deschedule a thread.
234 *
235 * (non-blocking, self contained on a per cpu basis)
236 */
237void
238lwkt_deschedule_self(thread_t td)
239{
240 crit_enter_quick(td);
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241 _lwkt_dequeue(td);
242 crit_exit_quick(td);
243}
244
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245/*
246 * LWKTs operate on a per-cpu basis
247 *
73e4f7b9 248 * WARNING! Called from early boot, 'mycpu' may not work yet.
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249 */
250void
251lwkt_gdinit(struct globaldata *gd)
252{
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253 int i;
254
255 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
256 TAILQ_INIT(&gd->gd_tdrunq[i]);
257 gd->gd_runqmask = 0;
73e4f7b9 258 TAILQ_INIT(&gd->gd_tdallq);
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259}
260
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261/*
262 * Create a new thread. The thread must be associated with a process context
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263 * or LWKT start address before it can be scheduled. If the target cpu is
264 * -1 the thread will be created on the current cpu.
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265 *
266 * If you intend to create a thread without a process context this function
267 * does everything except load the startup and switcher function.
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268 */
269thread_t
d3d32139 270lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 271{
c070746a 272 globaldata_t gd = mycpu;
99df837e 273 void *stack;
7d0bac62 274
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275 /*
276 * If static thread storage is not supplied allocate a thread. Reuse
277 * a cached free thread if possible. gd_freetd is used to keep an exiting
278 * thread intact through the exit.
279 */
ef0fdad1 280 if (td == NULL) {
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281 if ((td = gd->gd_freetd) != NULL)
282 gd->gd_freetd = NULL;
283 else
284 td = objcache_get(thread_cache, M_WAITOK);
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285 KASSERT((td->td_flags &
286 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD,
287 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
288 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 289 }
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290
291 /*
292 * Try to reuse cached stack.
293 */
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294 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
295 if (flags & TDF_ALLOCATED_STACK) {
e4846942 296 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
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297 stack = NULL;
298 }
299 }
300 if (stack == NULL) {
e4846942 301 stack = (void *)kmem_alloc(&kernel_map, stksize);
ef0fdad1 302 flags |= TDF_ALLOCATED_STACK;
99df837e 303 }
75cdbe6c 304 if (cpu < 0)
c070746a 305 lwkt_init_thread(td, stack, stksize, flags, gd);
75cdbe6c 306 else
f470d0c8 307 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 308 return(td);
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309}
310
311/*
312 * Initialize a preexisting thread structure. This function is used by
313 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
314 *
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315 * All threads start out in a critical section at a priority of
316 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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317 * appropriate. This function may send an IPI message when the
318 * requested cpu is not the current cpu and consequently gd_tdallq may
319 * not be initialized synchronously from the point of view of the originating
320 * cpu.
321 *
322 * NOTE! we have to be careful in regards to creating threads for other cpus
323 * if SMP has not yet been activated.
7d0bac62 324 */
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325#ifdef SMP
326
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327static void
328lwkt_init_thread_remote(void *arg)
329{
330 thread_t td = arg;
331
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332 /*
333 * Protected by critical section held by IPI dispatch
334 */
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335 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
336}
337
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338#endif
339
7d0bac62 340void
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341lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
342 struct globaldata *gd)
7d0bac62 343{
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344 globaldata_t mygd = mycpu;
345
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346 bzero(td, sizeof(struct thread));
347 td->td_kstack = stack;
f470d0c8 348 td->td_kstack_size = stksize;
d3d32139 349 td->td_flags = flags;
26a0694b 350 td->td_gd = gd;
f8c3996b 351 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT;
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352#ifdef SMP
353 if ((flags & TDF_MPSAFE) == 0)
354 td->td_mpcount = 1;
355#endif
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356 if (lwkt_use_spin_port)
357 lwkt_initport_spin(&td->td_msgport);
358 else
359 lwkt_initport_thread(&td->td_msgport, td);
99df837e 360 pmap_init_thread(td);
0f7a3396 361#ifdef SMP
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362 /*
363 * Normally initializing a thread for a remote cpu requires sending an
364 * IPI. However, the idlethread is setup before the other cpus are
365 * activated so we have to treat it as a special case. XXX manipulation
366 * of gd_tdallq requires the BGL.
367 */
368 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 369 crit_enter_gd(mygd);
75cdbe6c 370 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 371 crit_exit_gd(mygd);
75cdbe6c 372 } else {
2db3b277 373 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 374 }
0f7a3396 375#else
37af14fe 376 crit_enter_gd(mygd);
0f7a3396 377 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 378 crit_exit_gd(mygd);
0f7a3396 379#endif
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380}
381
382void
383lwkt_set_comm(thread_t td, const char *ctl, ...)
384{
e2565a42 385 __va_list va;
73e4f7b9 386
e2565a42 387 __va_start(va, ctl);
379210cb 388 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 389 __va_end(va);
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390}
391
99df837e 392void
73e4f7b9 393lwkt_hold(thread_t td)
99df837e 394{
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395 ++td->td_refs;
396}
397
398void
399lwkt_rele(thread_t td)
400{
401 KKASSERT(td->td_refs > 0);
402 --td->td_refs;
403}
404
405void
406lwkt_wait_free(thread_t td)
407{
408 while (td->td_refs)
377d4740 409 tsleep(td, 0, "tdreap", hz);
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410}
411
412void
413lwkt_free_thread(thread_t td)
414{
d9eea1a5 415 KASSERT((td->td_flags & TDF_RUNNING) == 0,
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416 ("lwkt_free_thread: did not exit! %p", td));
417
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418 if (td->td_flags & TDF_ALLOCATED_THREAD) {
419 objcache_put(thread_cache, td);
420 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
421 /* client-allocated struct with internally allocated stack */
422 KASSERT(td->td_kstack && td->td_kstack_size > 0,
423 ("lwkt_free_thread: corrupted stack"));
424 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
425 td->td_kstack = NULL;
426 td->td_kstack_size = 0;
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427 }
428}
429
430
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431/*
432 * Switch to the next runnable lwkt. If no LWKTs are runnable then
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433 * switch to the idlethread. Switching must occur within a critical
434 * section to avoid races with the scheduling queue.
435 *
436 * We always have full control over our cpu's run queue. Other cpus
437 * that wish to manipulate our queue must use the cpu_*msg() calls to
438 * talk to our cpu, so a critical section is all that is needed and
439 * the result is very, very fast thread switching.
440 *
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441 * The LWKT scheduler uses a fixed priority model and round-robins at
442 * each priority level. User process scheduling is a totally
443 * different beast and LWKT priorities should not be confused with
444 * user process priorities.
f1d1c3fa 445 *
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446 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch()
447 * cleans it up. Note that the td_switch() function cannot do anything that
448 * requires the MP lock since the MP lock will have already been setup for
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449 * the target thread (not the current thread). It's nice to have a scheduler
450 * that does not need the MP lock to work because it allows us to do some
451 * really cool high-performance MP lock optimizations.
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452 *
453 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
454 * is not called by the current thread in the preemption case, only when
455 * the preempting thread blocks (in order to return to the original thread).
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456 */
457void
458lwkt_switch(void)
459{
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460 globaldata_t gd = mycpu;
461 thread_t td = gd->gd_curthread;
8ad65e08 462 thread_t ntd;
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463#ifdef SMP
464 int mpheld;
465#endif
8ad65e08 466
46a3f46d 467 /*
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468 * Switching from within a 'fast' (non thread switched) interrupt or IPI
469 * is illegal. However, we may have to do it anyway if we hit a fatal
470 * kernel trap or we have paniced.
471 *
472 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 473 */
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474 if (gd->gd_intr_nesting_level) {
475 int savegdnest;
476 int savegdtrap;
477
478 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL) {
479 panic("lwkt_switch: cannot switch from within "
480 "a fast interrupt, yet, td %p\n", td);
481 } else {
482 savegdnest = gd->gd_intr_nesting_level;
483 savegdtrap = gd->gd_trap_nesting_level;
484 gd->gd_intr_nesting_level = 0;
485 gd->gd_trap_nesting_level = 0;
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486 if ((td->td_flags & TDF_PANICWARN) == 0) {
487 td->td_flags |= TDF_PANICWARN;
6ea70f76 488 kprintf("Warning: thread switch from interrupt or IPI, "
a7422615 489 "thread %p (%s)\n", td, td->td_comm);
1e5fb84b 490 print_backtrace();
a7422615 491 }
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492 lwkt_switch();
493 gd->gd_intr_nesting_level = savegdnest;
494 gd->gd_trap_nesting_level = savegdtrap;
495 return;
496 }
96728c05 497 }
ef0fdad1 498
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499 /*
500 * Passive release (used to transition from user to kernel mode
501 * when we block or switch rather then when we enter the kernel).
502 * This function is NOT called if we are switching into a preemption
503 * or returning from a preemption. Typically this causes us to lose
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504 * our current process designation (if we have one) and become a true
505 * LWKT thread, and may also hand the current process designation to
506 * another process and schedule thread.
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507 */
508 if (td->td_release)
509 td->td_release(td);
510
37af14fe 511 crit_enter_gd(gd);
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512 if (td->td_toks)
513 lwkt_relalltokens(td);
514
515 /*
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516 * We had better not be holding any spin locks, but don't get into an
517 * endless panic loop.
9d265729 518 */
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519 KASSERT(gd->gd_spinlock_rd == NULL || panicstr != NULL,
520 ("lwkt_switch: still holding a shared spinlock %p!",
521 gd->gd_spinlock_rd));
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522 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
523 ("lwkt_switch: still holding %d exclusive spinlocks!",
524 gd->gd_spinlocks_wr));
9d265729 525
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526
527#ifdef SMP
528 /*
529 * td_mpcount cannot be used to determine if we currently hold the
530 * MP lock because get_mplock() will increment it prior to attempting
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531 * to get the lock, and switch out if it can't. Our ownership of
532 * the actual lock will remain stable while we are in a critical section
533 * (but, of course, another cpu may own or release the lock so the
534 * actual value of mp_lock is not stable).
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535 */
536 mpheld = MP_LOCK_HELD();
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537#ifdef INVARIANTS
538 if (td->td_cscount) {
6ea70f76 539 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
540 td);
541 if (panic_on_cscount)
542 panic("switching while mastering cpusync");
543 }
544#endif
8a8d5d85 545#endif
99df837e
MD
546 if ((ntd = td->td_preempted) != NULL) {
547 /*
548 * We had preempted another thread on this cpu, resume the preempted
26a0694b
MD
549 * thread. This occurs transparently, whether the preempted thread
550 * was scheduled or not (it may have been preempted after descheduling
8a8d5d85
MD
551 * itself).
552 *
553 * We have to setup the MP lock for the original thread after backing
554 * out the adjustment that was made to curthread when the original
555 * was preempted.
99df837e 556 */
26a0694b 557 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
8a8d5d85 558#ifdef SMP
96728c05 559 if (ntd->td_mpcount && mpheld == 0) {
fc92d4aa 560 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d",
96728c05
MD
561 td, ntd, td->td_mpcount, ntd->td_mpcount);
562 }
8a8d5d85
MD
563 if (ntd->td_mpcount) {
564 td->td_mpcount -= ntd->td_mpcount;
565 KKASSERT(td->td_mpcount >= 0);
566 }
567#endif
26a0694b 568 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
569
570 /*
b9eb1c19
MD
571 * The interrupt may have woken a thread up, we need to properly
572 * set the reschedule flag if the originally interrupted thread is
573 * at a lower priority.
8ec60c3f
MD
574 */
575 if (gd->gd_runqmask > (2 << (ntd->td_pri & TDPRI_MASK)) - 1)
576 need_lwkt_resched();
8a8d5d85 577 /* YYY release mp lock on switchback if original doesn't need it */
8ad65e08 578 } else {
4b5f931b
MD
579 /*
580 * Priority queue / round-robin at each priority. Note that user
581 * processes run at a fixed, low priority and the user process
582 * scheduler deals with interactions between user processes
583 * by scheduling and descheduling them from the LWKT queue as
584 * necessary.
8a8d5d85
MD
585 *
586 * We have to adjust the MP lock for the target thread. If we
587 * need the MP lock and cannot obtain it we try to locate a
41a01a4d
MD
588 * thread that does not need the MP lock. If we cannot, we spin
589 * instead of HLT.
590 *
591 * A similar issue exists for the tokens held by the target thread.
592 * If we cannot obtain ownership of the tokens we cannot immediately
593 * schedule the thread.
594 */
595
8ec60c3f
MD
596 /*
597 * If an LWKT reschedule was requested, well that is what we are
598 * doing now so clear it.
599 */
600 clear_lwkt_resched();
4b5f931b
MD
601again:
602 if (gd->gd_runqmask) {
603 int nq = bsrl(gd->gd_runqmask);
604 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
605 gd->gd_runqmask &= ~(1 << nq);
606 goto again;
607 }
8a8d5d85 608#ifdef SMP
41a01a4d 609 /*
df6b8ba0
MD
610 * THREAD SELECTION FOR AN SMP MACHINE BUILD
611 *
41a01a4d
MD
612 * If the target needs the MP lock and we couldn't get it,
613 * or if the target is holding tokens and we could not
614 * gain ownership of the tokens, continue looking for a
615 * thread to schedule and spin instead of HLT if we can't.
a453459d
MD
616 *
617 * NOTE: the mpheld variable invalid after this conditional, it
618 * can change due to both cpu_try_mplock() returning success
9d265729 619 * AND interactions in lwkt_getalltokens() due to the fact that
a453459d
MD
620 * we are trying to check the mpcount of a thread other then
621 * the current thread. Because of this, if the current thread
622 * is not holding td_mpcount, an IPI indirectly run via
9d265729 623 * lwkt_getalltokens() can obtain and release the MP lock and
a453459d 624 * cause the core MP lock to be released.
41a01a4d
MD
625 */
626 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) ||
9d265729 627 (ntd->td_toks && lwkt_getalltokens(ntd) == 0)
41a01a4d 628 ) {
8a8d5d85 629 u_int32_t rqmask = gd->gd_runqmask;
a453459d
MD
630
631 mpheld = MP_LOCK_HELD();
632 ntd = NULL;
8a8d5d85
MD
633 while (rqmask) {
634 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) {
38717797 635 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock()) {
a453459d 636 /* spinning due to MP lock being held */
41a01a4d 637 continue;
38717797 638 }
a453459d
MD
639
640 /*
9d265729 641 * mpheld state invalid after getalltokens call returns
a453459d
MD
642 * failure, but the variable is only needed for
643 * the loop.
644 */
9d265729 645 if (ntd->td_toks && !lwkt_getalltokens(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);
b9eb1c19
MD
659
660 /*
661 * We have two choices. We can either refuse to run a
662 * user thread when a kernel thread needs the MP lock
663 * but could not get it, or we can allow it to run but
664 * then expect an IPI (hopefully) later on to force a
665 * reschedule when the MP lock might become available.
666 */
667 if (nq < TDPRI_KERN_LPSCHED) {
684a93c4
MD
668 break; /* for now refuse to run */
669#if 0
b9eb1c19
MD
670 if (chain_mplock == 0)
671 break;
b9eb1c19 672 /* continue loop, allow user threads to be scheduled */
684a93c4 673#endif
b9eb1c19 674 }
8a8d5d85 675 }
684a93c4
MD
676
677 /*
678 * Case where a (kernel) thread needed the MP lock and could
679 * not get one, and we may or may not have found another
680 * thread which does not need the MP lock to run while
681 * we wait (ntd).
682 */
8a8d5d85 683 if (ntd == NULL) {
a2a5ad0d
MD
684 ntd = &gd->gd_idlethread;
685 ntd->td_flags |= TDF_IDLE_NOHLT;
684a93c4
MD
686 set_mplock_contention_mask(gd);
687 cpu_mplock_contested();
df6b8ba0 688 goto using_idle_thread;
8a8d5d85 689 } else {
684a93c4 690 clr_mplock_contention_mask(gd);
344ad853 691 ++gd->gd_cnt.v_swtch;
8a8d5d85
MD
692 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
693 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
694 }
695 } else {
684a93c4 696 clr_mplock_contention_mask(gd);
344ad853 697 ++gd->gd_cnt.v_swtch;
8a8d5d85
MD
698 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
699 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
700 }
701#else
df6b8ba0
MD
702 /*
703 * THREAD SELECTION FOR A UP MACHINE BUILD. We don't have to
7eb611ef
MD
704 * worry about tokens or the BGL. However, we still have
705 * to call lwkt_getalltokens() in order to properly detect
706 * stale tokens. This call cannot fail for a UP build!
df6b8ba0 707 */
7eb611ef 708 lwkt_getalltokens(ntd);
344ad853 709 ++gd->gd_cnt.v_swtch;
4b5f931b
MD
710 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
711 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
8a8d5d85 712#endif
4b5f931b 713 } else {
3c23a41a 714 /*
60f945af
MD
715 * We have nothing to run but only let the idle loop halt
716 * the cpu if there are no pending interrupts.
3c23a41a 717 */
a2a5ad0d 718 ntd = &gd->gd_idlethread;
60f945af 719 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
3c23a41a 720 ntd->td_flags |= TDF_IDLE_NOHLT;
a453459d 721#ifdef SMP
df6b8ba0
MD
722using_idle_thread:
723 /*
724 * The idle thread should not be holding the MP lock unless we
725 * are trapping in the kernel or in a panic. Since we select the
726 * idle thread unconditionally when no other thread is available,
727 * if the MP lock is desired during a panic or kernel trap, we
728 * have to loop in the scheduler until we get it.
729 */
730 if (ntd->td_mpcount) {
731 mpheld = MP_LOCK_HELD();
684a93c4 732 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
df6b8ba0 733 panic("Idle thread %p was holding the BGL!", ntd);
684a93c4 734 if (mpheld == 0)
df6b8ba0
MD
735 goto again;
736 }
a453459d 737#endif
4b5f931b 738 }
f1d1c3fa 739 }
26a0694b
MD
740 KASSERT(ntd->td_pri >= TDPRI_CRIT,
741 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
8a8d5d85
MD
742
743 /*
744 * Do the actual switch. If the new target does not need the MP lock
745 * and we are holding it, release the MP lock. If the new target requires
746 * the MP lock we have already acquired it for the target.
747 */
748#ifdef SMP
749 if (ntd->td_mpcount == 0 ) {
750 if (MP_LOCK_HELD())
751 cpu_rel_mplock();
752 } else {
a453459d 753 ASSERT_MP_LOCK_HELD(ntd);
8a8d5d85
MD
754 }
755#endif
94f6d86e
MD
756 if (td != ntd) {
757 ++switch_count;
b2b3ffcd 758#ifdef __x86_64__
f64b567c
SW
759 {
760 int tos_ok __debugvar = jg_tos_ok(ntd);
761 KKASSERT(tos_ok);
762 }
85514115 763#endif
d850923c 764 KTR_LOG(ctxsw_sw, td, ntd);
f1d1c3fa 765 td->td_switch(ntd);
94f6d86e 766 }
37af14fe
MD
767 /* NOTE: current cpu may have changed after switch */
768 crit_exit_quick(td);
8ad65e08
MD
769}
770
b68b7282 771/*
96728c05
MD
772 * Request that the target thread preempt the current thread. Preemption
773 * only works under a specific set of conditions:
b68b7282 774 *
96728c05
MD
775 * - We are not preempting ourselves
776 * - The target thread is owned by the current cpu
777 * - We are not currently being preempted
778 * - The target is not currently being preempted
d3d1cbc8
MD
779 * - We are not holding any spin locks
780 * - The target thread is not holding any tokens
96728c05
MD
781 * - We are able to satisfy the target's MP lock requirements (if any).
782 *
783 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
784 * this is called via lwkt_schedule() through the td_preemptable callback.
785 * critpri is the managed critical priority that we should ignore in order
786 * to determine whether preemption is possible (aka usually just the crit
787 * priority of lwkt_schedule() itself).
b68b7282 788 *
26a0694b
MD
789 * XXX at the moment we run the target thread in a critical section during
790 * the preemption in order to prevent the target from taking interrupts
791 * that *WE* can't. Preemption is strictly limited to interrupt threads
792 * and interrupt-like threads, outside of a critical section, and the
793 * preempted source thread will be resumed the instant the target blocks
794 * whether or not the source is scheduled (i.e. preemption is supposed to
795 * be as transparent as possible).
4b5f931b 796 *
8a8d5d85
MD
797 * The target thread inherits our MP count (added to its own) for the
798 * duration of the preemption in order to preserve the atomicy of the
96728c05
MD
799 * MP lock during the preemption. Therefore, any preempting targets must be
800 * careful in regards to MP assertions. Note that the MP count may be
71ef2f5c
MD
801 * out of sync with the physical mp_lock, but we do not have to preserve
802 * the original ownership of the lock if it was out of synch (that is, we
803 * can leave it synchronized on return).
b68b7282
MD
804 */
805void
96728c05 806lwkt_preempt(thread_t ntd, int critpri)
b68b7282 807{
46a3f46d 808 struct globaldata *gd = mycpu;
0a3f9b47 809 thread_t td;
8a8d5d85
MD
810#ifdef SMP
811 int mpheld;
57c254db 812 int savecnt;
8a8d5d85 813#endif
b68b7282 814
26a0694b 815 /*
96728c05
MD
816 * The caller has put us in a critical section. We can only preempt
817 * if the caller of the caller was not in a critical section (basically
d666840a 818 * a local interrupt), as determined by the 'critpri' parameter. We
47737962 819 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 820 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
821 *
822 * YYY The target thread must be in a critical section (else it must
823 * inherit our critical section? I dunno yet).
41a01a4d 824 *
0a3f9b47 825 * Set need_lwkt_resched() unconditionally for now YYY.
26a0694b
MD
826 */
827 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 828
0a3f9b47 829 td = gd->gd_curthread;
0a3f9b47 830 if ((ntd->td_pri & TDPRI_MASK) <= (td->td_pri & TDPRI_MASK)) {
57c254db
MD
831 ++preempt_miss;
832 return;
833 }
96728c05
MD
834 if ((td->td_pri & ~TDPRI_MASK) > critpri) {
835 ++preempt_miss;
8ec60c3f 836 need_lwkt_resched();
96728c05
MD
837 return;
838 }
839#ifdef SMP
46a3f46d 840 if (ntd->td_gd != gd) {
96728c05 841 ++preempt_miss;
8ec60c3f 842 need_lwkt_resched();
96728c05
MD
843 return;
844 }
845#endif
41a01a4d 846 /*
d3d1cbc8 847 * Take the easy way out and do not preempt if we are holding
d666840a 848 * any spinlocks. We could test whether the thread(s) being
41a01a4d
MD
849 * preempted interlock against the target thread's tokens and whether
850 * we can get all the target thread's tokens, but this situation
851 * should not occur very often so its easier to simply not preempt.
d666840a
MD
852 * Also, plain spinlocks are impossible to figure out at this point so
853 * just don't preempt.
d3d1cbc8
MD
854 *
855 * Do not try to preempt if the target thread is holding any tokens.
856 * We could try to acquire the tokens but this case is so rare there
857 * is no need to support it.
41a01a4d 858 */
bbb31c5d 859 if (gd->gd_spinlock_rd || gd->gd_spinlocks_wr) {
41a01a4d 860 ++preempt_miss;
8ec60c3f 861 need_lwkt_resched();
41a01a4d
MD
862 return;
863 }
d3d1cbc8
MD
864 if (ntd->td_toks) {
865 ++preempt_miss;
866 need_lwkt_resched();
867 return;
868 }
26a0694b
MD
869 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
870 ++preempt_weird;
8ec60c3f 871 need_lwkt_resched();
26a0694b
MD
872 return;
873 }
874 if (ntd->td_preempted) {
4b5f931b 875 ++preempt_hit;
8ec60c3f 876 need_lwkt_resched();
26a0694b 877 return;
b68b7282 878 }
8a8d5d85 879#ifdef SMP
a2a5ad0d
MD
880 /*
881 * note: an interrupt might have occured just as we were transitioning
71ef2f5c
MD
882 * to or from the MP lock. In this case td_mpcount will be pre-disposed
883 * (non-zero) but not actually synchronized with the actual state of the
884 * lock. We can use it to imply an MP lock requirement for the
885 * preemption but we cannot use it to test whether we hold the MP lock
886 * or not.
a2a5ad0d 887 */
96728c05 888 savecnt = td->td_mpcount;
71ef2f5c 889 mpheld = MP_LOCK_HELD();
8a8d5d85
MD
890 ntd->td_mpcount += td->td_mpcount;
891 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) {
892 ntd->td_mpcount -= td->td_mpcount;
893 ++preempt_miss;
8ec60c3f 894 need_lwkt_resched();
8a8d5d85
MD
895 return;
896 }
897#endif
26a0694b 898
8ec60c3f
MD
899 /*
900 * Since we are able to preempt the current thread, there is no need to
901 * call need_lwkt_resched().
902 */
26a0694b
MD
903 ++preempt_hit;
904 ntd->td_preempted = td;
905 td->td_flags |= TDF_PREEMPT_LOCK;
d850923c 906 KTR_LOG(ctxsw_pre, td, ntd);
26a0694b 907 td->td_switch(ntd);
b9eb1c19 908
26a0694b 909 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
96728c05
MD
910#ifdef SMP
911 KKASSERT(savecnt == td->td_mpcount);
71ef2f5c
MD
912 mpheld = MP_LOCK_HELD();
913 if (mpheld && td->td_mpcount == 0)
96728c05 914 cpu_rel_mplock();
71ef2f5c 915 else if (mpheld == 0 && td->td_mpcount)
96728c05
MD
916 panic("lwkt_preempt(): MP lock was not held through");
917#endif
26a0694b
MD
918 ntd->td_preempted = NULL;
919 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
920}
921
f1d1c3fa 922/*
faaeffac 923 * Conditionally call splz() if gd_reqflags indicates work is pending.
f1d1c3fa 924 *
faaeffac
MD
925 * td_nest_count prevents deep nesting via splz() or doreti() which
926 * might otherwise blow out the kernel stack. Note that except for
927 * this special case, we MUST call splz() here to handle any
928 * pending ints, particularly after we switch, or we might accidently
929 * halt the cpu with interrupts pending.
ef0fdad1 930 *
f1d1c3fa
MD
931 * (self contained on a per cpu basis)
932 */
933void
faaeffac 934splz_check(void)
f1d1c3fa 935{
7966cb69
MD
936 globaldata_t gd = mycpu;
937 thread_t td = gd->gd_curthread;
ef0fdad1 938
46a3f46d 939 if (gd->gd_reqflags && td->td_nest_count < 2)
f1d1c3fa 940 splz();
f1d1c3fa
MD
941}
942
8ad65e08 943/*
faaeffac
MD
944 * This implements a normal yield which will yield to equal priority
945 * threads as well as higher priority threads. Note that gd_reqflags
946 * tests will be handled by the crit_exit() call in lwkt_switch().
f1d1c3fa
MD
947 *
948 * (self contained on a per cpu basis)
8ad65e08
MD
949 */
950void
f1d1c3fa 951lwkt_yield(void)
8ad65e08 952{
37af14fe 953 lwkt_schedule_self(curthread);
f1d1c3fa
MD
954 lwkt_switch();
955}
956
3824f392
MD
957/*
958 * This function is used along with the lwkt_passive_recover() inline
959 * by the trap code to negotiate a passive release of the current
960 * process/lwp designation with the user scheduler.
961 */
962void
963lwkt_passive_release(struct thread *td)
964{
965 struct lwp *lp = td->td_lwp;
966
967 td->td_release = NULL;
968 lwkt_setpri_self(TDPRI_KERN_USER);
969 lp->lwp_proc->p_usched->release_curproc(lp);
970}
971
972/*
973 * Make a kernel thread act as if it were in user mode with regards
974 * to scheduling, to avoid becoming cpu-bound in the kernel. Kernel
975 * loops which may be potentially cpu-bound can call lwkt_user_yield().
976 *
977 * The lwkt_user_yield() function is designed to have very low overhead
978 * if no yield is determined to be needed.
979 */
980void
981lwkt_user_yield(void)
982{
983 thread_t td = curthread;
984 struct lwp *lp = td->td_lwp;
985
986#ifdef SMP
987 /*
988 * XXX SEVERE TEMPORARY HACK. A cpu-bound operation running in the
989 * kernel can prevent other cpus from servicing interrupt threads
990 * which still require the MP lock (which is a lot of them). This
991 * has a chaining effect since if the interrupt is blocked, so is
992 * the event, so normal scheduling will not pick up on the problem.
993 */
684a93c4
MD
994 if (mp_lock_contention_mask && td->td_mpcount) {
995 yield_mplock(td);
3824f392
MD
996 }
997#endif
998
999 /*
1000 * Another kernel thread wants the cpu
1001 */
1002 if (lwkt_resched_wanted())
1003 lwkt_switch();
1004
1005 /*
1006 * If the user scheduler has asynchronously determined that the current
1007 * process (when running in user mode) needs to lose the cpu then make
1008 * sure we are released.
1009 */
1010 if (user_resched_wanted()) {
1011 if (td->td_release)
1012 td->td_release(td);
1013 }
1014
1015 /*
1016 * If we are released reduce our priority
1017 */
1018 if (td->td_release == NULL) {
1019 if (lwkt_check_resched(td) > 0)
1020 lwkt_switch();
e381e77c
MD
1021 if (lp) {
1022 lp->lwp_proc->p_usched->acquire_curproc(lp);
1023 td->td_release = lwkt_passive_release;
1024 lwkt_setpri_self(TDPRI_USER_NORM);
1025 }
3824f392
MD
1026 }
1027}
1028
b9eb1c19
MD
1029/*
1030 * Return 0 if no runnable threads are pending at the same or higher
1031 * priority as the passed thread.
1032 *
1033 * Return 1 if runnable threads are pending at the same priority.
1034 *
1035 * Return 2 if runnable threads are pending at a higher priority.
1036 */
1037int
1038lwkt_check_resched(thread_t td)
1039{
1040 int pri = td->td_pri & TDPRI_MASK;
1041
1042 if (td->td_gd->gd_runqmask > (2 << pri) - 1)
1043 return(2);
1044 if (TAILQ_NEXT(td, td_threadq))
1045 return(1);
1046 return(0);
1047}
1048
8ad65e08 1049/*
f1d1c3fa
MD
1050 * Generic schedule. Possibly schedule threads belonging to other cpus and
1051 * deal with threads that might be blocked on a wait queue.
1052 *
0a3f9b47
MD
1053 * We have a little helper inline function which does additional work after
1054 * the thread has been enqueued, including dealing with preemption and
1055 * setting need_lwkt_resched() (which prevents the kernel from returning
1056 * to userland until it has processed higher priority threads).
6330a558
MD
1057 *
1058 * It is possible for this routine to be called after a failed _enqueue
1059 * (due to the target thread migrating, sleeping, or otherwise blocked).
1060 * We have to check that the thread is actually on the run queue!
361d01dd
MD
1061 *
1062 * reschedok is an optimized constant propagated from lwkt_schedule() or
1063 * lwkt_schedule_noresched(). By default it is non-zero, causing a
1064 * reschedule to be requested if the target thread has a higher priority.
1065 * The port messaging code will set MSG_NORESCHED and cause reschedok to
1066 * be 0, prevented undesired reschedules.
8ad65e08 1067 */
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1068static __inline
1069void
361d01dd 1070_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int cpri, int reschedok)
0a3f9b47 1071{
b9eb1c19 1072 thread_t otd;
c730be20 1073
6330a558 1074 if (ntd->td_flags & TDF_RUNQ) {
361d01dd 1075 if (ntd->td_preemptable && reschedok) {
6330a558 1076 ntd->td_preemptable(ntd, cpri); /* YYY +token */
361d01dd 1077 } else if (reschedok) {
b9eb1c19
MD
1078 otd = curthread;
1079 if ((ntd->td_pri & TDPRI_MASK) > (otd->td_pri & TDPRI_MASK))
c730be20 1080 need_lwkt_resched();
6330a558 1081 }
0a3f9b47
MD
1082 }
1083}
1084
361d01dd 1085static __inline
8ad65e08 1086void
361d01dd 1087_lwkt_schedule(thread_t td, int reschedok)
8ad65e08 1088{
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MD
1089 globaldata_t mygd = mycpu;
1090
41a01a4d 1091 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
37af14fe 1092 crit_enter_gd(mygd);
9388413d 1093 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 1094 if (td == mygd->gd_curthread) {
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MD
1095 _lwkt_enqueue(td);
1096 } else {
f1d1c3fa 1097 /*
7cd8d145
MD
1098 * If we own the thread, there is no race (since we are in a
1099 * critical section). If we do not own the thread there might
1100 * be a race but the target cpu will deal with it.
f1d1c3fa 1101 */
0f7a3396 1102#ifdef SMP
7cd8d145 1103 if (td->td_gd == mygd) {
9d265729 1104 _lwkt_enqueue(td);
361d01dd 1105 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok);
f1d1c3fa 1106 } else {
e381e77c 1107 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1108 }
0f7a3396 1109#else
7cd8d145 1110 _lwkt_enqueue(td);
361d01dd 1111 _lwkt_schedule_post(mygd, td, TDPRI_CRIT, reschedok);
0f7a3396 1112#endif
8ad65e08 1113 }
37af14fe 1114 crit_exit_gd(mygd);
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MD
1115}
1116
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MD
1117void
1118lwkt_schedule(thread_t td)
1119{
1120 _lwkt_schedule(td, 1);
1121}
1122
1123void
1124lwkt_schedule_noresched(thread_t td)
1125{
1126 _lwkt_schedule(td, 0);
1127}
1128
88ebb169
SW
1129#ifdef SMP
1130
e381e77c
MD
1131/*
1132 * When scheduled remotely if frame != NULL the IPIQ is being
1133 * run via doreti or an interrupt then preemption can be allowed.
1134 *
1135 * To allow preemption we have to drop the critical section so only
1136 * one is present in _lwkt_schedule_post.
1137 */
1138static void
1139lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1140{
1141 thread_t td = curthread;
1142 thread_t ntd = arg;
1143
1144 if (frame && ntd->td_preemptable) {
1145 crit_exit_noyield(td);
1146 _lwkt_schedule(ntd, 1);
1147 crit_enter_quick(td);
1148 } else {
1149 _lwkt_schedule(ntd, 1);
1150 }
1151}
1152
d9eea1a5 1153/*
52eedfb5
MD
1154 * Thread migration using a 'Pull' method. The thread may or may not be
1155 * the current thread. It MUST be descheduled and in a stable state.
1156 * lwkt_giveaway() must be called on the cpu owning the thread.
1157 *
1158 * At any point after lwkt_giveaway() is called, the target cpu may
1159 * 'pull' the thread by calling lwkt_acquire().
1160 *
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MD
1161 * We have to make sure the thread is not sitting on a per-cpu tsleep
1162 * queue or it will blow up when it moves to another cpu.
1163 *
52eedfb5 1164 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1165 */
52eedfb5
MD
1166void
1167lwkt_giveaway(thread_t td)
1168{
3b4192fb 1169 globaldata_t gd = mycpu;
52eedfb5 1170
3b4192fb
MD
1171 crit_enter_gd(gd);
1172 if (td->td_flags & TDF_TSLEEPQ)
1173 tsleep_remove(td);
1174 KKASSERT(td->td_gd == gd);
1175 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1176 td->td_flags |= TDF_MIGRATING;
1177 crit_exit_gd(gd);
52eedfb5
MD
1178}
1179
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MD
1180void
1181lwkt_acquire(thread_t td)
1182{
37af14fe
MD
1183 globaldata_t gd;
1184 globaldata_t mygd;
a2a5ad0d 1185
52eedfb5 1186 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1187 gd = td->td_gd;
37af14fe 1188 mygd = mycpu;
52eedfb5 1189 if (gd != mycpu) {
35238fa5 1190 cpu_lfence();
52eedfb5 1191 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1192 crit_enter_gd(mygd);
df910c23
MD
1193 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1194#ifdef SMP
1195 lwkt_process_ipiq();
1196#endif
52eedfb5 1197 cpu_lfence();
df910c23 1198 }
37af14fe 1199 td->td_gd = mygd;
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MD
1200 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1201 td->td_flags &= ~TDF_MIGRATING;
1202 crit_exit_gd(mygd);
1203 } else {
1204 crit_enter_gd(mygd);
1205 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1206 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1207 crit_exit_gd(mygd);
a2a5ad0d
MD
1208 }
1209}
1210
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MD
1211#endif
1212
f1d1c3fa
MD
1213/*
1214 * Generic deschedule. Descheduling threads other then your own should be
1215 * done only in carefully controlled circumstances. Descheduling is
1216 * asynchronous.
1217 *
1218 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1219 */
1220void
1221lwkt_deschedule(thread_t td)
1222{
f1d1c3fa 1223 crit_enter();
b8a98473 1224#ifdef SMP
f1d1c3fa
MD
1225 if (td == curthread) {
1226 _lwkt_dequeue(td);
1227 } else {
a72187e9 1228 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1229 _lwkt_dequeue(td);
1230 } else {
b8a98473 1231 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1232 }
1233 }
b8a98473
MD
1234#else
1235 _lwkt_dequeue(td);
1236#endif
f1d1c3fa
MD
1237 crit_exit();
1238}
1239
4b5f931b
MD
1240/*
1241 * Set the target thread's priority. This routine does not automatically
1242 * switch to a higher priority thread, LWKT threads are not designed for
1243 * continuous priority changes. Yield if you want to switch.
1244 *
1245 * We have to retain the critical section count which uses the high bits
26a0694b
MD
1246 * of the td_pri field. The specified priority may also indicate zero or
1247 * more critical sections by adding TDPRI_CRIT*N.
18bbe476
MD
1248 *
1249 * Note that we requeue the thread whether it winds up on a different runq
1250 * or not. uio_yield() depends on this and the routine is not normally
1251 * called with the same priority otherwise.
4b5f931b
MD
1252 */
1253void
1254lwkt_setpri(thread_t td, int pri)
1255{
26a0694b 1256 KKASSERT(pri >= 0);
a72187e9 1257 KKASSERT(td->td_gd == mycpu);
26a0694b
MD
1258 crit_enter();
1259 if (td->td_flags & TDF_RUNQ) {
1260 _lwkt_dequeue(td);
1261 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1262 _lwkt_enqueue(td);
1263 } else {
1264 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1265 }
1266 crit_exit();
1267}
1268
03bd0a5e
MD
1269/*
1270 * Set the initial priority for a thread prior to it being scheduled for
1271 * the first time. The thread MUST NOT be scheduled before or during
1272 * this call. The thread may be assigned to a cpu other then the current
1273 * cpu.
1274 *
1275 * Typically used after a thread has been created with TDF_STOPPREQ,
1276 * and before the thread is initially scheduled.
1277 */
1278void
1279lwkt_setpri_initial(thread_t td, int pri)
1280{
1281 KKASSERT(pri >= 0);
1282 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
1283 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1284}
1285
26a0694b
MD
1286void
1287lwkt_setpri_self(int pri)
1288{
1289 thread_t td = curthread;
1290
4b5f931b
MD
1291 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1292 crit_enter();
1293 if (td->td_flags & TDF_RUNQ) {
1294 _lwkt_dequeue(td);
1295 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1296 _lwkt_enqueue(td);
1297 } else {
1298 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1299 }
1300 crit_exit();
1301}
1302
5d21b981 1303/*
52eedfb5
MD
1304 * Migrate the current thread to the specified cpu.
1305 *
1306 * This is accomplished by descheduling ourselves from the current cpu,
1307 * moving our thread to the tdallq of the target cpu, IPI messaging the
1308 * target cpu, and switching out. TDF_MIGRATING prevents scheduling
1309 * races while the thread is being migrated.
ae8e83e6
MD
1310 *
1311 * We must be sure to remove ourselves from the current cpu's tsleepq
1312 * before potentially moving to another queue. The thread can be on
1313 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1314 */
3d28ff59 1315#ifdef SMP
5d21b981 1316static void lwkt_setcpu_remote(void *arg);
3d28ff59 1317#endif
5d21b981
MD
1318
1319void
1320lwkt_setcpu_self(globaldata_t rgd)
1321{
1322#ifdef SMP
1323 thread_t td = curthread;
1324
1325 if (td->td_gd != rgd) {
1326 crit_enter_quick(td);
ae8e83e6 1327 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1328 tsleep_remove(td);
5d21b981
MD
1329 td->td_flags |= TDF_MIGRATING;
1330 lwkt_deschedule_self(td);
52eedfb5 1331 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
b8a98473 1332 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td);
5d21b981
MD
1333 lwkt_switch();
1334 /* we are now on the target cpu */
52eedfb5 1335 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1336 crit_exit_quick(td);
1337 }
1338#endif
1339}
1340
ecdefdda
MD
1341void
1342lwkt_migratecpu(int cpuid)
1343{
1344#ifdef SMP
1345 globaldata_t rgd;
1346
1347 rgd = globaldata_find(cpuid);
1348 lwkt_setcpu_self(rgd);
1349#endif
1350}
1351
5d21b981
MD
1352/*
1353 * Remote IPI for cpu migration (called while in a critical section so we
1354 * do not have to enter another one). The thread has already been moved to
1355 * our cpu's allq, but we must wait for the thread to be completely switched
1356 * out on the originating cpu before we schedule it on ours or the stack
1357 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD
1358 * change to main memory.
1359 *
1360 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races
1361 * against wakeups. It is best if this interface is used only when there
1362 * are no pending events that might try to schedule the thread.
1363 */
3d28ff59 1364#ifdef SMP
5d21b981
MD
1365static void
1366lwkt_setcpu_remote(void *arg)
1367{
1368 thread_t td = arg;
1369 globaldata_t gd = mycpu;
1370
df910c23
MD
1371 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1372#ifdef SMP
1373 lwkt_process_ipiq();
1374#endif
35238fa5 1375 cpu_lfence();
df910c23 1376 }
5d21b981 1377 td->td_gd = gd;
35238fa5 1378 cpu_sfence();
5d21b981 1379 td->td_flags &= ~TDF_MIGRATING;
9388413d 1380 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
5d21b981
MD
1381 _lwkt_enqueue(td);
1382}
3d28ff59 1383#endif
5d21b981 1384
553ea3c8 1385struct lwp *
4b5f931b
MD
1386lwkt_preempted_proc(void)
1387{
73e4f7b9 1388 thread_t td = curthread;
4b5f931b
MD
1389 while (td->td_preempted)
1390 td = td->td_preempted;
553ea3c8 1391 return(td->td_lwp);
4b5f931b
MD
1392}
1393
99df837e
MD
1394/*
1395 * Create a kernel process/thread/whatever. It shares it's address space
1396 * with proc0 - ie: kernel only.
1397 *
365fa13f
MD
1398 * NOTE! By default new threads are created with the MP lock held. A
1399 * thread which does not require the MP lock should release it by calling
1400 * rel_mplock() at the start of the new thread.
99df837e
MD
1401 */
1402int
1403lwkt_create(void (*func)(void *), void *arg,
75cdbe6c 1404 struct thread **tdp, thread_t template, int tdflags, int cpu,
ef0fdad1 1405 const char *fmt, ...)
99df837e 1406{
73e4f7b9 1407 thread_t td;
e2565a42 1408 __va_list ap;
99df837e 1409
d3d32139 1410 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1411 tdflags);
a2a5ad0d
MD
1412 if (tdp)
1413 *tdp = td;
709799ea 1414 cpu_set_thread_handler(td, lwkt_exit, func, arg);
99df837e
MD
1415
1416 /*
1417 * Set up arg0 for 'ps' etc
1418 */
e2565a42 1419 __va_start(ap, fmt);
379210cb 1420 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1421 __va_end(ap);
99df837e
MD
1422
1423 /*
1424 * Schedule the thread to run
1425 */
ef0fdad1
MD
1426 if ((td->td_flags & TDF_STOPREQ) == 0)
1427 lwkt_schedule(td);
1428 else
1429 td->td_flags &= ~TDF_STOPREQ;
99df837e
MD
1430 return 0;
1431}
1432
1433/*
1434 * Destroy an LWKT thread. Warning! This function is not called when
1435 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1436 * uses a different reaping mechanism.
1437 */
1438void
1439lwkt_exit(void)
1440{
1441 thread_t td = curthread;
c070746a 1442 thread_t std;
8826f33a 1443 globaldata_t gd;
99df837e
MD
1444
1445 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1446 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1447 caps_exit(td);
c070746a
MD
1448
1449 /*
1450 * Get us into a critical section to interlock gd_freetd and loop
1451 * until we can get it freed.
1452 *
1453 * We have to cache the current td in gd_freetd because objcache_put()ing
1454 * it would rip it out from under us while our thread is still active.
1455 */
1456 gd = mycpu;
37af14fe 1457 crit_enter_quick(td);
c070746a
MD
1458 while ((std = gd->gd_freetd) != NULL) {
1459 gd->gd_freetd = NULL;
1460 objcache_put(thread_cache, std);
1461 }
3b4192fb
MD
1462
1463 /*
1464 * Remove thread resources from kernel lists and deschedule us for
1465 * the last time.
1466 */
1467 if (td->td_flags & TDF_TSLEEPQ)
1468 tsleep_remove(td);
79eae878 1469 biosched_done(td);
37af14fe 1470 lwkt_deschedule_self(td);
e56e4dea 1471 lwkt_remove_tdallq(td);
c070746a
MD
1472 if (td->td_flags & TDF_ALLOCATED_THREAD)
1473 gd->gd_freetd = td;
99df837e
MD
1474 cpu_thread_exit();
1475}
1476
e56e4dea
MD
1477void
1478lwkt_remove_tdallq(thread_t td)
1479{
1480 KKASSERT(td->td_gd == mycpu);
1481 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1482}
1483
2d93b37a
MD
1484void
1485crit_panic(void)
1486{
1487 thread_t td = curthread;
1488 int lpri = td->td_pri;
1489
1490 td->td_pri = 0;
1491 panic("td_pri is/would-go negative! %p %d", td, lpri);
1492}
1493
d165e668
MD
1494#ifdef SMP
1495
bd8015ca
MD
1496/*
1497 * Called from debugger/panic on cpus which have been stopped. We must still
1498 * process the IPIQ while stopped, even if we were stopped while in a critical
1499 * section (XXX).
1500 *
1501 * If we are dumping also try to process any pending interrupts. This may
1502 * or may not work depending on the state of the cpu at the point it was
1503 * stopped.
1504 */
1505void
1506lwkt_smp_stopped(void)
1507{
1508 globaldata_t gd = mycpu;
1509
1510 crit_enter_gd(gd);
1511 if (dumping) {
1512 lwkt_process_ipiq();
1513 splz();
1514 } else {
1515 lwkt_process_ipiq();
1516 }
1517 crit_exit_gd(gd);
1518}
1519
d165e668 1520#endif