Install getopt_long.3
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
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1/*
2 * Copyright (c) 2003 Matthew Dillon <dillon@backplane.com>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
3b6b7bd1 26 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.54 2004/02/15 02:14:41 dillon Exp $
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27 */
28
29/*
30 * Each cpu in a system has its own self-contained light weight kernel
31 * thread scheduler, which means that generally speaking we only need
32 * to use a critical section to avoid problems. Foreign thread
33 * scheduling is queued via (async) IPIs.
f1d1c3fa 34 *
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35 * NOTE: on UP machines smp_active is defined to be 0. On SMP machines
36 * smp_active is 0 prior to SMP activation, then it is 1. The LWKT module
37 * uses smp_active to optimize UP builds and to avoid sending IPIs during
38 * early boot (primarily interrupt and network thread initialization).
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39 */
40
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41#ifdef _KERNEL
42
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43#include <sys/param.h>
44#include <sys/systm.h>
45#include <sys/kernel.h>
46#include <sys/proc.h>
47#include <sys/rtprio.h>
48#include <sys/queue.h>
f1d1c3fa 49#include <sys/thread2.h>
7d0bac62 50#include <sys/sysctl.h>
99df837e 51#include <sys/kthread.h>
f1d1c3fa 52#include <machine/cpu.h>
99df837e 53#include <sys/lock.h>
f6bf3af1 54#include <sys/caps.h>
f1d1c3fa 55
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56#include <vm/vm.h>
57#include <vm/vm_param.h>
58#include <vm/vm_kern.h>
59#include <vm/vm_object.h>
60#include <vm/vm_page.h>
61#include <vm/vm_map.h>
62#include <vm/vm_pager.h>
63#include <vm/vm_extern.h>
64#include <vm/vm_zone.h>
65
99df837e 66#include <machine/stdarg.h>
57c254db 67#include <machine/ipl.h>
96728c05 68#include <machine/smp.h>
99df837e 69
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70#define THREAD_STACK (UPAGES * PAGE_SIZE)
71
72#else
73
74#include <sys/stdint.h>
fb04f4fd 75#include <libcaps/thread.h>
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76#include <sys/thread.h>
77#include <sys/msgport.h>
78#include <sys/errno.h>
fb04f4fd 79#include <libcaps/globaldata.h>
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80#include <sys/thread2.h>
81#include <sys/msgport2.h>
709799ea 82#include <stdio.h>
05220613 83#include <stdlib.h>
709799ea 84#include <string.h>
c95cd171 85#include <machine/cpufunc.h>
709799ea 86#include <machine/lock.h>
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87
88#endif
89
7d0bac62 90static int untimely_switch = 0;
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91static __int64_t switch_count = 0;
92static __int64_t preempt_hit = 0;
93static __int64_t preempt_miss = 0;
94static __int64_t preempt_weird = 0;
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95
96#ifdef _KERNEL
97
98SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, "");
4b5f931b 99SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
4b5f931b 100SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, "");
4b5f931b 101SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, "");
26a0694b 102SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
7d0bac62 103
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104#endif
105
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106/*
107 * These helper procedures handle the runq, they can only be called from
108 * within a critical section.
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109 *
110 * WARNING! Prior to SMP being brought up it is possible to enqueue and
111 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
112 * instead of 'mycpu' when referencing the globaldata structure. Once
113 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 114 */
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115static __inline
116void
117_lwkt_dequeue(thread_t td)
118{
119 if (td->td_flags & TDF_RUNQ) {
4b5f931b 120 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 121 struct globaldata *gd = td->td_gd;
4b5f931b 122
f1d1c3fa 123 td->td_flags &= ~TDF_RUNQ;
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124 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq);
125 /* runqmask is passively cleaned up by the switcher */
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126 }
127}
128
129static __inline
130void
131_lwkt_enqueue(thread_t td)
132{
133 if ((td->td_flags & TDF_RUNQ) == 0) {
4b5f931b 134 int nq = td->td_pri & TDPRI_MASK;
75cdbe6c 135 struct globaldata *gd = td->td_gd;
4b5f931b 136
f1d1c3fa 137 td->td_flags |= TDF_RUNQ;
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138 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq);
139 gd->gd_runqmask |= 1 << nq;
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140 }
141}
8ad65e08 142
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143static __inline
144int
145_lwkt_wantresched(thread_t ntd, thread_t cur)
146{
147 return((ntd->td_pri & TDPRI_MASK) > (cur->td_pri & TDPRI_MASK));
148}
149
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150#ifdef _KERNEL
151
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152/*
153 * LWKTs operate on a per-cpu basis
154 *
73e4f7b9 155 * WARNING! Called from early boot, 'mycpu' may not work yet.
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156 */
157void
158lwkt_gdinit(struct globaldata *gd)
159{
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160 int i;
161
162 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
163 TAILQ_INIT(&gd->gd_tdrunq[i]);
164 gd->gd_runqmask = 0;
73e4f7b9 165 TAILQ_INIT(&gd->gd_tdallq);
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166}
167
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168#endif /* _KERNEL */
169
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170/*
171 * Initialize a thread wait structure prior to first use.
172 *
173 * NOTE! called from low level boot code, we cannot do anything fancy!
174 */
175void
176lwkt_init_wait(lwkt_wait_t w)
177{
178 TAILQ_INIT(&w->wa_waitq);
179}
180
181/*
182 * Create a new thread. The thread must be associated with a process context
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183 * or LWKT start address before it can be scheduled. If the target cpu is
184 * -1 the thread will be created on the current cpu.
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185 *
186 * If you intend to create a thread without a process context this function
187 * does everything except load the startup and switcher function.
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188 */
189thread_t
75cdbe6c 190lwkt_alloc_thread(struct thread *td, int cpu)
7d0bac62 191{
99df837e 192 void *stack;
ef0fdad1 193 int flags = 0;
7d0bac62 194
ef0fdad1 195 if (td == NULL) {
26a0694b 196 crit_enter();
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197 if (mycpu->gd_tdfreecount > 0) {
198 --mycpu->gd_tdfreecount;
199 td = TAILQ_FIRST(&mycpu->gd_tdfreeq);
d9eea1a5 200 KASSERT(td != NULL && (td->td_flags & TDF_RUNNING) == 0,
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201 ("lwkt_alloc_thread: unexpected NULL or corrupted td"));
202 TAILQ_REMOVE(&mycpu->gd_tdfreeq, td, td_threadq);
203 crit_exit();
204 stack = td->td_kstack;
205 flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
206 } else {
207 crit_exit();
05220613 208#ifdef _KERNEL
ef0fdad1 209 td = zalloc(thread_zone);
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210#else
211 td = malloc(sizeof(struct thread));
212#endif
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213 td->td_kstack = NULL;
214 flags |= TDF_ALLOCATED_THREAD;
215 }
216 }
217 if ((stack = td->td_kstack) == NULL) {
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218#ifdef _KERNEL
219 stack = (void *)kmem_alloc(kernel_map, THREAD_STACK);
220#else
fb04f4fd 221 stack = libcaps_alloc_stack(THREAD_STACK);
05220613 222#endif
ef0fdad1 223 flags |= TDF_ALLOCATED_STACK;
99df837e 224 }
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225 if (cpu < 0)
226 lwkt_init_thread(td, stack, flags, mycpu);
227 else
228 lwkt_init_thread(td, stack, flags, globaldata_find(cpu));
99df837e 229 return(td);
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230}
231
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232#ifdef _KERNEL
233
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234/*
235 * Initialize a preexisting thread structure. This function is used by
236 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
237 *
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238 * All threads start out in a critical section at a priority of
239 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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240 * appropriate. This function may send an IPI message when the
241 * requested cpu is not the current cpu and consequently gd_tdallq may
242 * not be initialized synchronously from the point of view of the originating
243 * cpu.
244 *
245 * NOTE! we have to be careful in regards to creating threads for other cpus
246 * if SMP has not yet been activated.
7d0bac62 247 */
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248static void
249lwkt_init_thread_remote(void *arg)
250{
251 thread_t td = arg;
252
253 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
254}
255
7d0bac62 256void
26a0694b 257lwkt_init_thread(thread_t td, void *stack, int flags, struct globaldata *gd)
7d0bac62 258{
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259 bzero(td, sizeof(struct thread));
260 td->td_kstack = stack;
261 td->td_flags |= flags;
26a0694b 262 td->td_gd = gd;
f8c3996b 263 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT;
c95cd171 264 lwkt_initport(&td->td_msgport, td);
99df837e 265 pmap_init_thread(td);
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266 if (smp_active == 0 || gd == mycpu) {
267 crit_enter();
268 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
269 crit_exit();
270 } else {
2db3b277 271 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 272 }
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273}
274
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275#endif /* _KERNEL */
276
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277void
278lwkt_set_comm(thread_t td, const char *ctl, ...)
279{
e2565a42 280 __va_list va;
73e4f7b9 281
e2565a42 282 __va_start(va, ctl);
73e4f7b9 283 vsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 284 __va_end(va);
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285}
286
99df837e 287void
73e4f7b9 288lwkt_hold(thread_t td)
99df837e 289{
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290 ++td->td_refs;
291}
292
293void
294lwkt_rele(thread_t td)
295{
296 KKASSERT(td->td_refs > 0);
297 --td->td_refs;
298}
299
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300#ifdef _KERNEL
301
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302void
303lwkt_wait_free(thread_t td)
304{
305 while (td->td_refs)
377d4740 306 tsleep(td, 0, "tdreap", hz);
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307}
308
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309#endif
310
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311void
312lwkt_free_thread(thread_t td)
313{
314 struct globaldata *gd = mycpu;
315
d9eea1a5 316 KASSERT((td->td_flags & TDF_RUNNING) == 0,
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317 ("lwkt_free_thread: did not exit! %p", td));
318
319 crit_enter();
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320 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
321 if (gd->gd_tdfreecount < CACHE_NTHREADS &&
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322 (td->td_flags & TDF_ALLOCATED_THREAD)
323 ) {
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324 ++gd->gd_tdfreecount;
325 TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq);
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326 crit_exit();
327 } else {
328 crit_exit();
329 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
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330#ifdef _KERNEL
331 kmem_free(kernel_map, (vm_offset_t)td->td_kstack, THREAD_STACK);
332#else
fb04f4fd 333 libcaps_free_stack(td->td_kstack, THREAD_STACK);
05220613 334#endif
73e4f7b9 335 /* gd invalid */
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336 td->td_kstack = NULL;
337 }
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338 if (td->td_flags & TDF_ALLOCATED_THREAD) {
339#ifdef _KERNEL
99df837e 340 zfree(thread_zone, td);
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341#else
342 free(td);
343#endif
344 }
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345 }
346}
347
348
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349/*
350 * Switch to the next runnable lwkt. If no LWKTs are runnable then
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351 * switch to the idlethread. Switching must occur within a critical
352 * section to avoid races with the scheduling queue.
353 *
354 * We always have full control over our cpu's run queue. Other cpus
355 * that wish to manipulate our queue must use the cpu_*msg() calls to
356 * talk to our cpu, so a critical section is all that is needed and
357 * the result is very, very fast thread switching.
358 *
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359 * The LWKT scheduler uses a fixed priority model and round-robins at
360 * each priority level. User process scheduling is a totally
361 * different beast and LWKT priorities should not be confused with
362 * user process priorities.
f1d1c3fa 363 *
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364 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch()
365 * cleans it up. Note that the td_switch() function cannot do anything that
366 * requires the MP lock since the MP lock will have already been setup for
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367 * the target thread (not the current thread). It's nice to have a scheduler
368 * that does not need the MP lock to work because it allows us to do some
369 * really cool high-performance MP lock optimizations.
8ad65e08 370 */
96728c05 371
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372void
373lwkt_switch(void)
374{
4b5f931b 375 struct globaldata *gd;
f1d1c3fa 376 thread_t td = curthread;
8ad65e08 377 thread_t ntd;
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378#ifdef SMP
379 int mpheld;
380#endif
8ad65e08 381
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382 /*
383 * Switching from within a 'fast' (non thread switched) interrupt is
384 * illegal.
385 */
386 if (mycpu->gd_intr_nesting_level && panicstr == NULL) {
03aa8d99 387 panic("lwkt_switch: cannot switch from within a fast interrupt, yet\n");
96728c05 388 }
ef0fdad1 389
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390 /*
391 * Passive release (used to transition from user to kernel mode
392 * when we block or switch rather then when we enter the kernel).
393 * This function is NOT called if we are switching into a preemption
394 * or returning from a preemption. Typically this causes us to lose
395 * our P_CURPROC designation (if we have one) and become a true LWKT
396 * thread, and may also hand P_CURPROC to another process and schedule
397 * its thread.
398 */
399 if (td->td_release)
400 td->td_release(td);
401
f1d1c3fa 402 crit_enter();
4b5f931b 403 ++switch_count;
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404
405#ifdef SMP
406 /*
407 * td_mpcount cannot be used to determine if we currently hold the
408 * MP lock because get_mplock() will increment it prior to attempting
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409 * to get the lock, and switch out if it can't. Our ownership of
410 * the actual lock will remain stable while we are in a critical section
411 * (but, of course, another cpu may own or release the lock so the
412 * actual value of mp_lock is not stable).
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413 */
414 mpheld = MP_LOCK_HELD();
415#endif
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416 if ((ntd = td->td_preempted) != NULL) {
417 /*
418 * We had preempted another thread on this cpu, resume the preempted
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419 * thread. This occurs transparently, whether the preempted thread
420 * was scheduled or not (it may have been preempted after descheduling
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421 * itself).
422 *
423 * We have to setup the MP lock for the original thread after backing
424 * out the adjustment that was made to curthread when the original
425 * was preempted.
99df837e 426 */
26a0694b 427 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
8a8d5d85 428#ifdef SMP
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429 if (ntd->td_mpcount && mpheld == 0) {
430 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d\n",
431 td, ntd, td->td_mpcount, ntd->td_mpcount);
432 }
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433 if (ntd->td_mpcount) {
434 td->td_mpcount -= ntd->td_mpcount;
435 KKASSERT(td->td_mpcount >= 0);
436 }
437#endif
26a0694b 438 ntd->td_flags |= TDF_PREEMPT_DONE;
8a8d5d85 439 /* YYY release mp lock on switchback if original doesn't need it */
8ad65e08 440 } else {
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441 /*
442 * Priority queue / round-robin at each priority. Note that user
443 * processes run at a fixed, low priority and the user process
444 * scheduler deals with interactions between user processes
445 * by scheduling and descheduling them from the LWKT queue as
446 * necessary.
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447 *
448 * We have to adjust the MP lock for the target thread. If we
449 * need the MP lock and cannot obtain it we try to locate a
450 * thread that does not need the MP lock.
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451 */
452 gd = mycpu;
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453again:
454 if (gd->gd_runqmask) {
455 int nq = bsrl(gd->gd_runqmask);
456 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
457 gd->gd_runqmask &= ~(1 << nq);
458 goto again;
459 }
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460#ifdef SMP
461 if (ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) {
462 /*
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463 * Target needs MP lock and we couldn't get it, try
464 * to locate a thread which does not need the MP lock
3c23a41a 465 * to run. If we cannot locate a thread spin in idle.
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466 */
467 u_int32_t rqmask = gd->gd_runqmask;
468 while (rqmask) {
469 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) {
470 if (ntd->td_mpcount == 0)
471 break;
472 }
473 if (ntd)
474 break;
475 rqmask &= ~(1 << nq);
476 nq = bsrl(rqmask);
477 }
478 if (ntd == NULL) {
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479 ntd = &gd->gd_idlethread;
480 ntd->td_flags |= TDF_IDLE_NOHLT;
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481 } else {
482 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
483 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
484 }
485 } else {
486 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
487 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
488 }
489#else
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490 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
491 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
8a8d5d85 492#endif
4b5f931b 493 } else {
3c23a41a 494 /*
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495 * We have nothing to run but only let the idle loop halt
496 * the cpu if there are no pending interrupts.
3c23a41a 497 */
a2a5ad0d 498 ntd = &gd->gd_idlethread;
60f945af 499 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
3c23a41a 500 ntd->td_flags |= TDF_IDLE_NOHLT;
4b5f931b 501 }
f1d1c3fa 502 }
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503 KASSERT(ntd->td_pri >= TDPRI_CRIT,
504 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
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505
506 /*
507 * Do the actual switch. If the new target does not need the MP lock
508 * and we are holding it, release the MP lock. If the new target requires
509 * the MP lock we have already acquired it for the target.
510 */
511#ifdef SMP
512 if (ntd->td_mpcount == 0 ) {
513 if (MP_LOCK_HELD())
514 cpu_rel_mplock();
515 } else {
516 ASSERT_MP_LOCK_HELD();
517 }
518#endif
8a8d5d85 519 if (td != ntd) {
f1d1c3fa 520 td->td_switch(ntd);
8a8d5d85 521 }
96728c05 522
f1d1c3fa 523 crit_exit();
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524}
525
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526/*
527 * Switch if another thread has a higher priority. Do not switch to other
528 * threads at the same priority.
529 */
530void
531lwkt_maybe_switch()
532{
533 struct globaldata *gd = mycpu;
534 struct thread *td = gd->gd_curthread;
535
536 if ((td->td_pri & TDPRI_MASK) < bsrl(gd->gd_runqmask)) {
537 lwkt_switch();
538 }
539}
540
b68b7282 541/*
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542 * Request that the target thread preempt the current thread. Preemption
543 * only works under a specific set of conditions:
b68b7282 544 *
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545 * - We are not preempting ourselves
546 * - The target thread is owned by the current cpu
547 * - We are not currently being preempted
548 * - The target is not currently being preempted
549 * - We are able to satisfy the target's MP lock requirements (if any).
550 *
551 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
552 * this is called via lwkt_schedule() through the td_preemptable callback.
553 * critpri is the managed critical priority that we should ignore in order
554 * to determine whether preemption is possible (aka usually just the crit
555 * priority of lwkt_schedule() itself).
b68b7282 556 *
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MD
557 * XXX at the moment we run the target thread in a critical section during
558 * the preemption in order to prevent the target from taking interrupts
559 * that *WE* can't. Preemption is strictly limited to interrupt threads
560 * and interrupt-like threads, outside of a critical section, and the
561 * preempted source thread will be resumed the instant the target blocks
562 * whether or not the source is scheduled (i.e. preemption is supposed to
563 * be as transparent as possible).
4b5f931b 564 *
8a8d5d85
MD
565 * The target thread inherits our MP count (added to its own) for the
566 * duration of the preemption in order to preserve the atomicy of the
96728c05
MD
567 * MP lock during the preemption. Therefore, any preempting targets must be
568 * careful in regards to MP assertions. Note that the MP count may be
71ef2f5c
MD
569 * out of sync with the physical mp_lock, but we do not have to preserve
570 * the original ownership of the lock if it was out of synch (that is, we
571 * can leave it synchronized on return).
b68b7282
MD
572 */
573void
96728c05 574lwkt_preempt(thread_t ntd, int critpri)
b68b7282 575{
46a3f46d
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576 struct globaldata *gd = mycpu;
577 thread_t td = gd->gd_curthread;
8a8d5d85
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578#ifdef SMP
579 int mpheld;
57c254db 580 int savecnt;
8a8d5d85 581#endif
b68b7282 582
26a0694b 583 /*
96728c05
MD
584 * The caller has put us in a critical section. We can only preempt
585 * if the caller of the caller was not in a critical section (basically
57c254db
MD
586 * a local interrupt), as determined by the 'critpri' parameter. If
587 * we are unable to preempt
96728c05
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588 *
589 * YYY The target thread must be in a critical section (else it must
590 * inherit our critical section? I dunno yet).
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MD
591 */
592 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 593
cb973d15 594 need_resched();
57c254db
MD
595 if (!_lwkt_wantresched(ntd, td)) {
596 ++preempt_miss;
597 return;
598 }
96728c05
MD
599 if ((td->td_pri & ~TDPRI_MASK) > critpri) {
600 ++preempt_miss;
601 return;
602 }
603#ifdef SMP
46a3f46d 604 if (ntd->td_gd != gd) {
96728c05
MD
605 ++preempt_miss;
606 return;
607 }
608#endif
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MD
609 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
610 ++preempt_weird;
611 return;
612 }
613 if (ntd->td_preempted) {
4b5f931b 614 ++preempt_hit;
26a0694b 615 return;
b68b7282 616 }
8a8d5d85 617#ifdef SMP
a2a5ad0d
MD
618 /*
619 * note: an interrupt might have occured just as we were transitioning
71ef2f5c
MD
620 * to or from the MP lock. In this case td_mpcount will be pre-disposed
621 * (non-zero) but not actually synchronized with the actual state of the
622 * lock. We can use it to imply an MP lock requirement for the
623 * preemption but we cannot use it to test whether we hold the MP lock
624 * or not.
a2a5ad0d 625 */
96728c05 626 savecnt = td->td_mpcount;
71ef2f5c 627 mpheld = MP_LOCK_HELD();
8a8d5d85
MD
628 ntd->td_mpcount += td->td_mpcount;
629 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) {
630 ntd->td_mpcount -= td->td_mpcount;
631 ++preempt_miss;
632 return;
633 }
634#endif
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MD
635
636 ++preempt_hit;
637 ntd->td_preempted = td;
638 td->td_flags |= TDF_PREEMPT_LOCK;
639 td->td_switch(ntd);
640 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
96728c05
MD
641#ifdef SMP
642 KKASSERT(savecnt == td->td_mpcount);
71ef2f5c
MD
643 mpheld = MP_LOCK_HELD();
644 if (mpheld && td->td_mpcount == 0)
96728c05 645 cpu_rel_mplock();
71ef2f5c 646 else if (mpheld == 0 && td->td_mpcount)
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MD
647 panic("lwkt_preempt(): MP lock was not held through");
648#endif
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649 ntd->td_preempted = NULL;
650 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
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651}
652
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653/*
654 * Yield our thread while higher priority threads are pending. This is
655 * typically called when we leave a critical section but it can be safely
656 * called while we are in a critical section.
657 *
658 * This function will not generally yield to equal priority threads but it
659 * can occur as a side effect. Note that lwkt_switch() is called from
46a3f46d 660 * inside the critical section to prevent its own crit_exit() from reentering
f1d1c3fa
MD
661 * lwkt_yield_quick().
662 *
235957ed 663 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint
ef0fdad1
MD
664 * came along but was blocked and made pending.
665 *
f1d1c3fa
MD
666 * (self contained on a per cpu basis)
667 */
668void
669lwkt_yield_quick(void)
670{
7966cb69
MD
671 globaldata_t gd = mycpu;
672 thread_t td = gd->gd_curthread;
ef0fdad1 673
a2a5ad0d 674 /*
235957ed 675 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear
a2a5ad0d
MD
676 * it with a non-zero cpl then we might not wind up calling splz after
677 * a task switch when the critical section is exited even though the
46a3f46d 678 * new task could accept the interrupt.
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MD
679 *
680 * XXX from crit_exit() only called after last crit section is released.
681 * If called directly will run splz() even if in a critical section.
46a3f46d
MD
682 *
683 * td_nest_count prevent deep nesting via splz() or doreti(). Note that
684 * except for this special case, we MUST call splz() here to handle any
685 * pending ints, particularly after we switch, or we might accidently
686 * halt the cpu with interrupts pending.
a2a5ad0d 687 */
46a3f46d 688 if (gd->gd_reqflags && td->td_nest_count < 2)
f1d1c3fa 689 splz();
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MD
690
691 /*
692 * YYY enabling will cause wakeup() to task-switch, which really
693 * confused the old 4.x code. This is a good way to simulate
7d0bac62
MD
694 * preemption and MP without actually doing preemption or MP, because a
695 * lot of code assumes that wakeup() does not block.
f1d1c3fa 696 */
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697 if (untimely_switch && td->td_nest_count == 0 &&
698 gd->gd_intr_nesting_level == 0
699 ) {
f1d1c3fa
MD
700 crit_enter();
701 /*
702 * YYY temporary hacks until we disassociate the userland scheduler
703 * from the LWKT scheduler.
704 */
705 if (td->td_flags & TDF_RUNQ) {
706 lwkt_switch(); /* will not reenter yield function */
707 } else {
708 lwkt_schedule_self(); /* make sure we are scheduled */
709 lwkt_switch(); /* will not reenter yield function */
710 lwkt_deschedule_self(); /* make sure we are descheduled */
711 }
7966cb69 712 crit_exit_noyield(td);
f1d1c3fa 713 }
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MD
714}
715
8ad65e08 716/*
f1d1c3fa 717 * This implements a normal yield which, unlike _quick, will yield to equal
235957ed 718 * priority threads as well. Note that gd_reqflags tests will be handled by
f1d1c3fa
MD
719 * the crit_exit() call in lwkt_switch().
720 *
721 * (self contained on a per cpu basis)
8ad65e08
MD
722 */
723void
f1d1c3fa 724lwkt_yield(void)
8ad65e08 725{
f1d1c3fa
MD
726 lwkt_schedule_self();
727 lwkt_switch();
728}
729
730/*
731 * Schedule a thread to run. As the current thread we can always safely
732 * schedule ourselves, and a shortcut procedure is provided for that
733 * function.
734 *
735 * (non-blocking, self contained on a per cpu basis)
736 */
737void
738lwkt_schedule_self(void)
739{
740 thread_t td = curthread;
741
742 crit_enter();
743 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
f1d1c3fa 744 _lwkt_enqueue(td);
05220613 745#ifdef _KERNEL
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746 if (td->td_proc && td->td_proc->p_stat == SSLEEP)
747 panic("SCHED SELF PANIC");
05220613 748#endif
f1d1c3fa 749 crit_exit();
8ad65e08 750}
8ad65e08
MD
751
752/*
f1d1c3fa
MD
753 * Generic schedule. Possibly schedule threads belonging to other cpus and
754 * deal with threads that might be blocked on a wait queue.
755 *
96728c05 756 * YYY this is one of the best places to implement load balancing code.
f1d1c3fa
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757 * Load balancing can be accomplished by requesting other sorts of actions
758 * for the thread in question.
8ad65e08
MD
759 */
760void
761lwkt_schedule(thread_t td)
762{
96728c05 763#ifdef INVARIANTS
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764 if ((td->td_flags & TDF_PREEMPT_LOCK) == 0 && td->td_proc
765 && td->td_proc->p_stat == SSLEEP
766 ) {
767 printf("PANIC schedule curtd = %p (%d %d) target %p (%d %d)\n",
768 curthread,
769 curthread->td_proc ? curthread->td_proc->p_pid : -1,
770 curthread->td_proc ? curthread->td_proc->p_stat : -1,
771 td,
772 td->td_proc ? curthread->td_proc->p_pid : -1,
773 td->td_proc ? curthread->td_proc->p_stat : -1
774 );
775 panic("SCHED PANIC");
776 }
96728c05 777#endif
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MD
778 crit_enter();
779 if (td == curthread) {
780 _lwkt_enqueue(td);
781 } else {
782 lwkt_wait_t w;
783
784 /*
785 * If the thread is on a wait list we have to send our scheduling
786 * request to the owner of the wait structure. Otherwise we send
787 * the scheduling request to the cpu owning the thread. Races
788 * are ok, the target will forward the message as necessary (the
789 * message may chase the thread around before it finally gets
790 * acted upon).
791 *
792 * (remember, wait structures use stable storage)
793 */
794 if ((w = td->td_wait) != NULL) {
96728c05 795 if (lwkt_trytoken(&w->wa_token)) {
f1d1c3fa
MD
796 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
797 --w->wa_count;
798 td->td_wait = NULL;
75cdbe6c 799 if (smp_active == 0 || td->td_gd == mycpu) {
f1d1c3fa 800 _lwkt_enqueue(td);
57c254db 801 if (td->td_preemptable) {
96728c05 802 td->td_preemptable(td, TDPRI_CRIT*2); /* YYY +token */
57c254db
MD
803 } else if (_lwkt_wantresched(td, curthread)) {
804 need_resched();
805 }
f1d1c3fa 806 } else {
2db3b277 807 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_schedule, td);
f1d1c3fa 808 }
96728c05 809 lwkt_reltoken(&w->wa_token);
f1d1c3fa 810 } else {
96728c05 811 lwkt_send_ipiq(w->wa_token.t_cpu, (ipifunc_t)lwkt_schedule, td);
f1d1c3fa
MD
812 }
813 } else {
814 /*
815 * If the wait structure is NULL and we own the thread, there
816 * is no race (since we are in a critical section). If we
817 * do not own the thread there might be a race but the
818 * target cpu will deal with it.
819 */
75cdbe6c 820 if (smp_active == 0 || td->td_gd == mycpu) {
f1d1c3fa 821 _lwkt_enqueue(td);
57c254db 822 if (td->td_preemptable) {
96728c05 823 td->td_preemptable(td, TDPRI_CRIT);
57c254db
MD
824 } else if (_lwkt_wantresched(td, curthread)) {
825 need_resched();
826 }
f1d1c3fa 827 } else {
2db3b277 828 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_schedule, td);
f1d1c3fa
MD
829 }
830 }
8ad65e08 831 }
f1d1c3fa 832 crit_exit();
8ad65e08
MD
833}
834
d9eea1a5
MD
835/*
836 * Managed acquisition. This code assumes that the MP lock is held for
837 * the tdallq operation and that the thread has been descheduled from its
838 * original cpu. We also have to wait for the thread to be entirely switched
839 * out on its original cpu (this is usually fast enough that we never loop)
840 * since the LWKT system does not have to hold the MP lock while switching
841 * and the target may have released it before switching.
842 */
a2a5ad0d
MD
843void
844lwkt_acquire(thread_t td)
845{
846 struct globaldata *gd;
847
848 gd = td->td_gd;
849 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
d9eea1a5
MD
850 while (td->td_flags & TDF_RUNNING) /* XXX spin */
851 ;
a2a5ad0d
MD
852 if (gd != mycpu) {
853 crit_enter();
854 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); /* protected by BGL */
855 gd = mycpu;
856 td->td_gd = gd;
a2a5ad0d
MD
857 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); /* protected by BGL */
858 crit_exit();
859 }
860}
861
8ad65e08 862/*
f1d1c3fa
MD
863 * Deschedule a thread.
864 *
865 * (non-blocking, self contained on a per cpu basis)
866 */
867void
868lwkt_deschedule_self(void)
869{
870 thread_t td = curthread;
871
872 crit_enter();
873 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
f1d1c3fa
MD
874 _lwkt_dequeue(td);
875 crit_exit();
876}
877
878/*
879 * Generic deschedule. Descheduling threads other then your own should be
880 * done only in carefully controlled circumstances. Descheduling is
881 * asynchronous.
882 *
883 * This function may block if the cpu has run out of messages.
8ad65e08
MD
884 */
885void
886lwkt_deschedule(thread_t td)
887{
f1d1c3fa
MD
888 crit_enter();
889 if (td == curthread) {
890 _lwkt_dequeue(td);
891 } else {
a72187e9 892 if (td->td_gd == mycpu) {
f1d1c3fa
MD
893 _lwkt_dequeue(td);
894 } else {
2db3b277 895 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_deschedule, td);
f1d1c3fa
MD
896 }
897 }
898 crit_exit();
899}
900
4b5f931b
MD
901/*
902 * Set the target thread's priority. This routine does not automatically
903 * switch to a higher priority thread, LWKT threads are not designed for
904 * continuous priority changes. Yield if you want to switch.
905 *
906 * We have to retain the critical section count which uses the high bits
26a0694b
MD
907 * of the td_pri field. The specified priority may also indicate zero or
908 * more critical sections by adding TDPRI_CRIT*N.
4b5f931b
MD
909 */
910void
911lwkt_setpri(thread_t td, int pri)
912{
26a0694b 913 KKASSERT(pri >= 0);
a72187e9 914 KKASSERT(td->td_gd == mycpu);
26a0694b
MD
915 crit_enter();
916 if (td->td_flags & TDF_RUNQ) {
917 _lwkt_dequeue(td);
918 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
919 _lwkt_enqueue(td);
920 } else {
921 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
922 }
923 crit_exit();
924}
925
926void
927lwkt_setpri_self(int pri)
928{
929 thread_t td = curthread;
930
4b5f931b
MD
931 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
932 crit_enter();
933 if (td->td_flags & TDF_RUNQ) {
934 _lwkt_dequeue(td);
935 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
936 _lwkt_enqueue(td);
937 } else {
938 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
939 }
940 crit_exit();
941}
942
943struct proc *
944lwkt_preempted_proc(void)
945{
73e4f7b9 946 thread_t td = curthread;
4b5f931b
MD
947 while (td->td_preempted)
948 td = td->td_preempted;
949 return(td->td_proc);
950}
951
ece04fd0 952#if 0
4b5f931b 953
f1d1c3fa
MD
954/*
955 * This function deschedules the current thread and blocks on the specified
956 * wait queue. We obtain ownership of the wait queue in order to block
957 * on it. A generation number is used to interlock the wait queue in case
958 * it gets signalled while we are blocked waiting on the token.
959 *
960 * Note: alternatively we could dequeue our thread and then message the
961 * target cpu owning the wait queue. YYY implement as sysctl.
962 *
963 * Note: wait queue signals normally ping-pong the cpu as an optimization.
964 */
96728c05 965
f1d1c3fa 966void
ae8050a4 967lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen)
f1d1c3fa
MD
968{
969 thread_t td = curthread;
f1d1c3fa 970
f1d1c3fa 971 lwkt_gettoken(&w->wa_token);
ae8050a4 972 if (w->wa_gen == *gen) {
f1d1c3fa
MD
973 _lwkt_dequeue(td);
974 TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq);
975 ++w->wa_count;
976 td->td_wait = w;
ae8050a4 977 td->td_wmesg = wmesg;
ece04fd0 978again:
f1d1c3fa 979 lwkt_switch();
ece04fd0
MD
980 lwkt_regettoken(&w->wa_token);
981 if (td->td_wmesg != NULL) {
982 _lwkt_dequeue(td);
983 goto again;
984 }
8ad65e08 985 }
ae8050a4
MD
986 /* token might be lost, doesn't matter for gen update */
987 *gen = w->wa_gen;
f1d1c3fa
MD
988 lwkt_reltoken(&w->wa_token);
989}
990
991/*
992 * Signal a wait queue. We gain ownership of the wait queue in order to
993 * signal it. Once a thread is removed from the wait queue we have to
994 * deal with the cpu owning the thread.
995 *
996 * Note: alternatively we could message the target cpu owning the wait
997 * queue. YYY implement as sysctl.
998 */
999void
ece04fd0 1000lwkt_signal(lwkt_wait_t w, int count)
f1d1c3fa
MD
1001{
1002 thread_t td;
1003 int count;
1004
1005 lwkt_gettoken(&w->wa_token);
1006 ++w->wa_gen;
ece04fd0
MD
1007 if (count < 0)
1008 count = w->wa_count;
f1d1c3fa
MD
1009 while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) {
1010 --count;
1011 --w->wa_count;
1012 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
1013 td->td_wait = NULL;
ae8050a4 1014 td->td_wmesg = NULL;
a72187e9 1015 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1016 _lwkt_enqueue(td);
1017 } else {
2db3b277 1018 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_schedule, td);
f1d1c3fa
MD
1019 }
1020 lwkt_regettoken(&w->wa_token);
1021 }
1022 lwkt_reltoken(&w->wa_token);
1023}
1024
ece04fd0
MD
1025#endif
1026
99df837e
MD
1027/*
1028 * Create a kernel process/thread/whatever. It shares it's address space
1029 * with proc0 - ie: kernel only.
1030 *
365fa13f
MD
1031 * NOTE! By default new threads are created with the MP lock held. A
1032 * thread which does not require the MP lock should release it by calling
1033 * rel_mplock() at the start of the new thread.
99df837e
MD
1034 */
1035int
1036lwkt_create(void (*func)(void *), void *arg,
75cdbe6c 1037 struct thread **tdp, thread_t template, int tdflags, int cpu,
ef0fdad1 1038 const char *fmt, ...)
99df837e 1039{
73e4f7b9 1040 thread_t td;
e2565a42 1041 __va_list ap;
99df837e 1042
75cdbe6c 1043 td = lwkt_alloc_thread(template, cpu);
a2a5ad0d
MD
1044 if (tdp)
1045 *tdp = td;
709799ea 1046 cpu_set_thread_handler(td, lwkt_exit, func, arg);
ef0fdad1 1047 td->td_flags |= TDF_VERBOSE | tdflags;
8a8d5d85
MD
1048#ifdef SMP
1049 td->td_mpcount = 1;
1050#endif
99df837e
MD
1051
1052 /*
1053 * Set up arg0 for 'ps' etc
1054 */
e2565a42 1055 __va_start(ap, fmt);
99df837e 1056 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1057 __va_end(ap);
99df837e
MD
1058
1059 /*
1060 * Schedule the thread to run
1061 */
ef0fdad1
MD
1062 if ((td->td_flags & TDF_STOPREQ) == 0)
1063 lwkt_schedule(td);
1064 else
1065 td->td_flags &= ~TDF_STOPREQ;
99df837e
MD
1066 return 0;
1067}
1068
2d93b37a 1069/*
2d93b37a
MD
1070 * kthread_* is specific to the kernel and is not needed by userland.
1071 */
1072#ifdef _KERNEL
1073
99df837e
MD
1074/*
1075 * Destroy an LWKT thread. Warning! This function is not called when
1076 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1077 * uses a different reaping mechanism.
1078 */
1079void
1080lwkt_exit(void)
1081{
1082 thread_t td = curthread;
1083
1084 if (td->td_flags & TDF_VERBOSE)
1085 printf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1086 caps_exit(td);
99df837e
MD
1087 crit_enter();
1088 lwkt_deschedule_self();
1089 ++mycpu->gd_tdfreecount;
1090 TAILQ_INSERT_TAIL(&mycpu->gd_tdfreeq, td, td_threadq);
1091 cpu_thread_exit();
1092}
1093
1094/*
1095 * Create a kernel process/thread/whatever. It shares it's address space
ef0fdad1 1096 * with proc0 - ie: kernel only. 5.x compatible.
365fa13f
MD
1097 *
1098 * NOTE! By default kthreads are created with the MP lock held. A
1099 * thread which does not require the MP lock should release it by calling
1100 * rel_mplock() at the start of the new thread.
99df837e
MD
1101 */
1102int
1103kthread_create(void (*func)(void *), void *arg,
1104 struct thread **tdp, const char *fmt, ...)
1105{
73e4f7b9 1106 thread_t td;
e2565a42 1107 __va_list ap;
99df837e 1108
75cdbe6c 1109 td = lwkt_alloc_thread(NULL, -1);
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1110 if (tdp)
1111 *tdp = td;
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1112 cpu_set_thread_handler(td, kthread_exit, func, arg);
1113 td->td_flags |= TDF_VERBOSE;
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1114#ifdef SMP
1115 td->td_mpcount = 1;
1116#endif
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1117
1118 /*
1119 * Set up arg0 for 'ps' etc
1120 */
e2565a42 1121 __va_start(ap, fmt);
99df837e 1122 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1123 __va_end(ap);
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1124
1125 /*
1126 * Schedule the thread to run
1127 */
1128 lwkt_schedule(td);
1129 return 0;
1130}
1131
1132/*
1133 * Destroy an LWKT thread. Warning! This function is not called when
1134 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1135 * uses a different reaping mechanism.
1136 *
1137 * XXX duplicates lwkt_exit()
1138 */
1139void
1140kthread_exit(void)
1141{
1142 lwkt_exit();
1143}
1144
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1145#endif /* _KERNEL */
1146
1147void
1148crit_panic(void)
1149{
1150 thread_t td = curthread;
1151 int lpri = td->td_pri;
1152
1153 td->td_pri = 0;
1154 panic("td_pri is/would-go negative! %p %d", td, lpri);
1155}
1156