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[dragonfly.git] / sys / kern / lwkt_thread.c
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8ad65e08 1/*
b12defdc 2 * Copyright (c) 2003-2011 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>
b37f18d6 47#include <sys/kinfo.h>
8ad65e08 48#include <sys/queue.h>
7d0bac62 49#include <sys/sysctl.h>
99df837e 50#include <sys/kthread.h>
f1d1c3fa 51#include <machine/cpu.h>
99df837e 52#include <sys/lock.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>
f1d1c3fa 58
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59#include <sys/dsched.h>
60
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61#include <vm/vm.h>
62#include <vm/vm_param.h>
63#include <vm/vm_kern.h>
64#include <vm/vm_object.h>
65#include <vm/vm_page.h>
66#include <vm/vm_map.h>
67#include <vm/vm_pager.h>
68#include <vm/vm_extern.h>
7d0bac62 69
99df837e 70#include <machine/stdarg.h>
96728c05 71#include <machine/smp.h>
3a06728e 72#include <machine/clock.h>
99df837e 73
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74#ifdef _KERNEL_VIRTUAL
75#include <pthread.h>
76#endif
77
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78#define LOOPMASK
79
d850923c
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80#if !defined(KTR_CTXSW)
81#define KTR_CTXSW KTR_ALL
82#endif
83KTR_INFO_MASTER(ctxsw);
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84KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td);
85KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td);
86KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm);
87KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td);
1541028a 88
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89static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
90
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91#ifdef INVARIANTS
92static int panic_on_cscount = 0;
93#endif
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94static int64_t switch_count = 0;
95static int64_t preempt_hit = 0;
96static int64_t preempt_miss = 0;
97static int64_t preempt_weird = 0;
fb0f29c4 98static int lwkt_use_spin_port;
40aaf5fc 99static struct objcache *thread_cache;
a46b4a23 100int cpu_mwait_spin = 0;
05220613 101
e381e77c 102static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 103static void lwkt_setcpu_remote(void *arg);
e381e77c 104
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105/*
106 * We can make all thread ports use the spin backend instead of the thread
107 * backend. This should only be set to debug the spin backend.
108 */
109TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
110
0f7a3396 111#ifdef INVARIANTS
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112SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
113 "Panic if attempting to switch lwkt's while mastering cpusync");
0f7a3396 114#endif
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115SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
116 "Number of switched threads");
9733f757 117SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 118 "Successful preemption events");
9733f757 119SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
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120 "Failed preemption events");
121SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
122 "Number of preempted threads.");
b12defdc 123static int fairq_enable = 0;
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124SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
125 &fairq_enable, 0, "Turn on fairq priority accumulators");
85946b6c 126static int fairq_bypass = -1;
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127SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
128 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
129extern int lwkt_sched_debug;
130int lwkt_sched_debug = 0;
131SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
132 &lwkt_sched_debug, 0, "Scheduler debug");
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133static u_int lwkt_spin_loops = 10;
134SYSCTL_UINT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
b12defdc 135 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
fbc024e4 136static int preempt_enable = 1;
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137SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
138 &preempt_enable, 0, "Enable preemption");
7b234d8c 139static int lwkt_cache_threads = 0;
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140SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
141 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 142
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143/*
144 * These helper procedures handle the runq, they can only be called from
145 * within a critical section.
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146 *
147 * WARNING! Prior to SMP being brought up it is possible to enqueue and
148 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
149 * instead of 'mycpu' when referencing the globaldata structure. Once
150 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 151 */
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152static __inline
153void
154_lwkt_dequeue(thread_t td)
155{
156 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 157 struct globaldata *gd = td->td_gd;
4b5f931b 158
f1d1c3fa 159 td->td_flags &= ~TDF_RUNQ;
f9235b6d 160 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
de4d4cb0 161 --gd->gd_tdrunqcount;
f9235b6d 162 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 163 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
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164 }
165}
166
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167/*
168 * Priority enqueue.
169 *
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170 * There are a limited number of lwkt threads runnable since user
171 * processes only schedule one at a time per cpu. However, there can
172 * be many user processes in kernel mode exiting from a tsleep() which
e3e6be1f 173 * become runnable.
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174 *
175 * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and
176 * will ignore user priority. This is to ensure that user threads in
177 * kernel mode get cpu at some point regardless of what the user
178 * scheduler thinks.
f9235b6d 179 */
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180static __inline
181void
182_lwkt_enqueue(thread_t td)
183{
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184 thread_t xtd;
185
7f5d7ed7 186 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 187 struct globaldata *gd = td->td_gd;
4b5f931b 188
f1d1c3fa 189 td->td_flags |= TDF_RUNQ;
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190 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
191 if (xtd == NULL) {
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192 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
193 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 194 } else {
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195 /*
196 * NOTE: td_upri - higher numbers more desireable, same sense
197 * as td_pri (typically reversed from lwp_upri).
198 *
199 * In the equal priority case we want the best selection
200 * at the beginning so the less desireable selections know
201 * that they have to setrunqueue/go-to-another-cpu, even
202 * though it means switching back to the 'best' selection.
203 * This also avoids degenerate situations when many threads
204 * are runnable or waking up at the same time.
205 *
206 * If upri matches exactly place at end/round-robin.
207 */
d992c377 208 while (xtd &&
e3e6be1f 209 (xtd->td_pri >= td->td_pri ||
d992c377 210 (xtd->td_pri == td->td_pri &&
e3e6be1f 211 xtd->td_upri >= td->td_upri))) {
85946b6c 212 xtd = TAILQ_NEXT(xtd, td_threadq);
d992c377 213 }
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214 if (xtd)
215 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
216 else
217 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 218 }
de4d4cb0 219 ++gd->gd_tdrunqcount;
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220
221 /*
85946b6c 222 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 223 */
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224 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
225 need_lwkt_resched();
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226 }
227}
8ad65e08 228
e28c8ef4 229static boolean_t
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230_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
231{
232 struct thread *td = (struct thread *)obj;
233
234 td->td_kstack = NULL;
235 td->td_kstack_size = 0;
236 td->td_flags = TDF_ALLOCATED_THREAD;
4643740a 237 td->td_mpflags = 0;
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238 return (1);
239}
240
241static void
242_lwkt_thread_dtor(void *obj, void *privdata)
243{
244 struct thread *td = (struct thread *)obj;
245
246 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
247 ("_lwkt_thread_dtor: not allocated from objcache"));
248 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
249 td->td_kstack_size > 0,
250 ("_lwkt_thread_dtor: corrupted stack"));
251 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
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252 td->td_kstack = NULL;
253 td->td_flags = 0;
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254}
255
256/*
257 * Initialize the lwkt s/system.
765b1ae0 258 *
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259 * Nominally cache up to 32 thread + kstack structures. Cache more on
260 * systems with a lot of cpu cores.
40aaf5fc 261 */
ced589cb 262static void
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263lwkt_init(void)
264{
765b1ae0 265 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
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266 if (lwkt_cache_threads == 0) {
267 lwkt_cache_threads = ncpus * 4;
268 if (lwkt_cache_threads < 32)
269 lwkt_cache_threads = 32;
270 }
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271 thread_cache = objcache_create_mbacked(
272 M_THREAD, sizeof(struct thread),
2fce2579 273 0, lwkt_cache_threads,
765b1ae0 274 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
40aaf5fc 275}
ced589cb 276SYSINIT(lwkt_init, SI_BOOT2_LWKT_INIT, SI_ORDER_FIRST, lwkt_init, NULL);
40aaf5fc 277
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278/*
279 * Schedule a thread to run. As the current thread we can always safely
280 * schedule ourselves, and a shortcut procedure is provided for that
281 * function.
282 *
283 * (non-blocking, self contained on a per cpu basis)
284 */
285void
286lwkt_schedule_self(thread_t td)
287{
cfaeae2a 288 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 289 crit_enter_quick(td);
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290 KASSERT(td != &td->td_gd->gd_idlethread,
291 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
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292 KKASSERT(td->td_lwp == NULL ||
293 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
37af14fe 294 _lwkt_enqueue(td);
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295 crit_exit_quick(td);
296}
297
298/*
299 * Deschedule a thread.
300 *
301 * (non-blocking, self contained on a per cpu basis)
302 */
303void
304lwkt_deschedule_self(thread_t td)
305{
306 crit_enter_quick(td);
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307 _lwkt_dequeue(td);
308 crit_exit_quick(td);
309}
310
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311/*
312 * LWKTs operate on a per-cpu basis
313 *
73e4f7b9 314 * WARNING! Called from early boot, 'mycpu' may not work yet.
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315 */
316void
317lwkt_gdinit(struct globaldata *gd)
318{
f9235b6d 319 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 320 TAILQ_INIT(&gd->gd_tdallq);
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321}
322
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323/*
324 * Create a new thread. The thread must be associated with a process context
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325 * or LWKT start address before it can be scheduled. If the target cpu is
326 * -1 the thread will be created on the current cpu.
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327 *
328 * If you intend to create a thread without a process context this function
329 * does everything except load the startup and switcher function.
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330 */
331thread_t
d3d32139 332lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 333{
d2d8515b 334 static int cpu_rotator;
c070746a 335 globaldata_t gd = mycpu;
99df837e 336 void *stack;
7d0bac62 337
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338 /*
339 * If static thread storage is not supplied allocate a thread. Reuse
340 * a cached free thread if possible. gd_freetd is used to keep an exiting
341 * thread intact through the exit.
342 */
ef0fdad1 343 if (td == NULL) {
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344 crit_enter_gd(gd);
345 if ((td = gd->gd_freetd) != NULL) {
346 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
347 TDF_RUNQ)) == 0);
c070746a 348 gd->gd_freetd = NULL;
cf709dd2 349 } else {
c070746a 350 td = objcache_get(thread_cache, M_WAITOK);
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351 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
352 TDF_RUNQ)) == 0);
353 }
354 crit_exit_gd(gd);
40aaf5fc 355 KASSERT((td->td_flags &
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MD
356 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
357 TDF_ALLOCATED_THREAD,
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358 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
359 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 360 }
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361
362 /*
363 * Try to reuse cached stack.
364 */
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365 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
366 if (flags & TDF_ALLOCATED_STACK) {
e4846942 367 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
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368 stack = NULL;
369 }
370 }
371 if (stack == NULL) {
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372 if (cpu < 0)
373 stack = (void *)kmem_alloc_stack(&kernel_map, stksize, 0);
374 else
375 stack = (void *)kmem_alloc_stack(&kernel_map, stksize,
376 KM_CPU(cpu));
ef0fdad1 377 flags |= TDF_ALLOCATED_STACK;
99df837e 378 }
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379 if (cpu < 0) {
380 cpu = ++cpu_rotator;
381 cpu_ccfence();
382 cpu %= ncpus;
383 }
384 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 385 return(td);
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386}
387
388/*
389 * Initialize a preexisting thread structure. This function is used by
390 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
391 *
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392 * All threads start out in a critical section at a priority of
393 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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394 * appropriate. This function may send an IPI message when the
395 * requested cpu is not the current cpu and consequently gd_tdallq may
396 * not be initialized synchronously from the point of view of the originating
397 * cpu.
398 *
399 * NOTE! we have to be careful in regards to creating threads for other cpus
400 * if SMP has not yet been activated.
7d0bac62 401 */
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402static void
403lwkt_init_thread_remote(void *arg)
404{
405 thread_t td = arg;
406
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407 /*
408 * Protected by critical section held by IPI dispatch
409 */
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410 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
411}
412
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413/*
414 * lwkt core thread structural initialization.
415 *
416 * NOTE: All threads are initialized as mpsafe threads.
417 */
7d0bac62 418void
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419lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
420 struct globaldata *gd)
7d0bac62 421{
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422 globaldata_t mygd = mycpu;
423
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424 bzero(td, sizeof(struct thread));
425 td->td_kstack = stack;
f470d0c8 426 td->td_kstack_size = stksize;
d3d32139 427 td->td_flags = flags;
4643740a 428 td->td_mpflags = 0;
f256b6c0 429 td->td_type = TD_TYPE_GENERIC;
26a0694b 430 td->td_gd = gd;
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431 td->td_pri = TDPRI_KERN_DAEMON;
432 td->td_critcount = 1;
54341a3b 433 td->td_toks_have = NULL;
3b998fa9 434 td->td_toks_stop = &td->td_toks_base;
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435 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT)) {
436 lwkt_initport_spin(&td->td_msgport, td,
437 (flags & TDF_FIXEDCPU) ? TRUE : FALSE);
438 } else {
fb0f29c4 439 lwkt_initport_thread(&td->td_msgport, td);
c068fb59 440 }
99df837e 441 pmap_init_thread(td);
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442 /*
443 * Normally initializing a thread for a remote cpu requires sending an
444 * IPI. However, the idlethread is setup before the other cpus are
445 * activated so we have to treat it as a special case. XXX manipulation
446 * of gd_tdallq requires the BGL.
447 */
448 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 449 crit_enter_gd(mygd);
75cdbe6c 450 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 451 crit_exit_gd(mygd);
75cdbe6c 452 } else {
2db3b277 453 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 454 }
3573cf7b 455 dsched_enter_thread(td);
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456}
457
458void
459lwkt_set_comm(thread_t td, const char *ctl, ...)
460{
e2565a42 461 __va_list va;
73e4f7b9 462
e2565a42 463 __va_start(va, ctl);
379210cb 464 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 465 __va_end(va);
5bf48697 466 KTR_LOG(ctxsw_newtd, td, td->td_comm);
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467}
468
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469/*
470 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
471 * this does not prevent the thread from migrating to another cpu so the
472 * gd_tdallq state is not protected by this.
473 */
99df837e 474void
73e4f7b9 475lwkt_hold(thread_t td)
99df837e 476{
74c9628e 477 atomic_add_int(&td->td_refs, 1);
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478}
479
480void
481lwkt_rele(thread_t td)
482{
483 KKASSERT(td->td_refs > 0);
74c9628e 484 atomic_add_int(&td->td_refs, -1);
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485}
486
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487void
488lwkt_free_thread(thread_t td)
489{
74c9628e 490 KKASSERT(td->td_refs == 0);
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491 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
492 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
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493 if (td->td_flags & TDF_ALLOCATED_THREAD) {
494 objcache_put(thread_cache, td);
495 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
496 /* client-allocated struct with internally allocated stack */
497 KASSERT(td->td_kstack && td->td_kstack_size > 0,
498 ("lwkt_free_thread: corrupted stack"));
499 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
500 td->td_kstack = NULL;
501 td->td_kstack_size = 0;
99df837e 502 }
a86ce0cd 503
e7c0dbba 504 KTR_LOG(ctxsw_deadtd, td);
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505}
506
507
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508/*
509 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
510 * switch to the idlethread. Switching must occur within a critical
511 * section to avoid races with the scheduling queue.
512 *
513 * We always have full control over our cpu's run queue. Other cpus
514 * that wish to manipulate our queue must use the cpu_*msg() calls to
515 * talk to our cpu, so a critical section is all that is needed and
516 * the result is very, very fast thread switching.
517 *
96728c05
MD
518 * The LWKT scheduler uses a fixed priority model and round-robins at
519 * each priority level. User process scheduling is a totally
520 * different beast and LWKT priorities should not be confused with
521 * user process priorities.
f1d1c3fa 522 *
69d78e99
MD
523 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
524 * is not called by the current thread in the preemption case, only when
525 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
526 *
527 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
528 * migration and tsleep deschedule the current lwkt thread and call
529 * lwkt_switch(). In particular, the target cpu of the migration fully
530 * expects the thread to become non-runnable and can deadlock against
531 * cpusync operations if we run any IPIs prior to switching the thread out.
532 *
533 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 534 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
535 */
536void
537lwkt_switch(void)
538{
37af14fe
MD
539 globaldata_t gd = mycpu;
540 thread_t td = gd->gd_curthread;
8ad65e08 541 thread_t ntd;
5411d8f1 542 int upri;
3a06728e
MD
543#ifdef LOOPMASK
544 uint64_t tsc_base = rdtsc();
545#endif
8ad65e08 546
da0b0e8b 547 KKASSERT(gd->gd_processing_ipiq == 0);
121f93bc 548 KKASSERT(td->td_flags & TDF_RUNNING);
da0b0e8b 549
46a3f46d 550 /*
27e88a6e
MD
551 * Switching from within a 'fast' (non thread switched) interrupt or IPI
552 * is illegal. However, we may have to do it anyway if we hit a fatal
553 * kernel trap or we have paniced.
554 *
555 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 556 */
27e88a6e
MD
557 if (gd->gd_intr_nesting_level) {
558 int savegdnest;
559 int savegdtrap;
560
5fddbda2 561 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22 562 panic("lwkt_switch: Attempt to switch from a "
5a8df152 563 "fast interrupt, ipi, or hard code section, "
4a28fe22
MD
564 "td %p\n",
565 td);
27e88a6e
MD
566 } else {
567 savegdnest = gd->gd_intr_nesting_level;
568 savegdtrap = gd->gd_trap_nesting_level;
569 gd->gd_intr_nesting_level = 0;
570 gd->gd_trap_nesting_level = 0;
a7422615
MD
571 if ((td->td_flags & TDF_PANICWARN) == 0) {
572 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
573 kprintf("Warning: thread switch from interrupt, IPI, "
574 "or hard code section.\n"
a7422615 575 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 576 print_backtrace(-1);
a7422615 577 }
27e88a6e
MD
578 lwkt_switch();
579 gd->gd_intr_nesting_level = savegdnest;
580 gd->gd_trap_nesting_level = savegdtrap;
581 return;
582 }
96728c05 583 }
ef0fdad1 584
cb973d15 585 /*
85946b6c
MD
586 * Release our current user process designation if we are blocking
587 * or if a user reschedule was requested.
588 *
589 * NOTE: This function is NOT called if we are switching into or
590 * returning from a preemption.
591 *
592 * NOTE: Releasing our current user process designation may cause
593 * it to be assigned to another thread, which in turn will
594 * cause us to block in the usched acquire code when we attempt
595 * to return to userland.
596 *
597 * NOTE: On SMP systems this can be very nasty when heavy token
598 * contention is present so we want to be careful not to
599 * release the designation gratuitously.
cb973d15 600 */
85946b6c
MD
601 if (td->td_release &&
602 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 603 td->td_release(td);
85946b6c 604 }
cb973d15 605
85946b6c 606 /*
5411d8f1
MD
607 * Release all tokens. Once we do this we must remain in the critical
608 * section and cannot run IPIs or other interrupts until we switch away
609 * because they may implode if they try to get a token using our thread
610 * context.
85946b6c 611 */
37af14fe 612 crit_enter_gd(gd);
3b998fa9 613 if (TD_TOKS_HELD(td))
9d265729
MD
614 lwkt_relalltokens(td);
615
616 /*
b02926de
MD
617 * We had better not be holding any spin locks, but don't get into an
618 * endless panic loop.
9d265729 619 */
0846e4ce 620 KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL,
d666840a 621 ("lwkt_switch: still holding %d exclusive spinlocks!",
0846e4ce 622 gd->gd_spinlocks));
9d265729 623
0f7a3396
MD
624#ifdef INVARIANTS
625 if (td->td_cscount) {
6ea70f76 626 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
627 td);
628 if (panic_on_cscount)
629 panic("switching while mastering cpusync");
630 }
8a8d5d85 631#endif
f9235b6d
MD
632
633 /*
634 * If we had preempted another thread on this cpu, resume the preempted
635 * thread. This occurs transparently, whether the preempted thread
636 * was scheduled or not (it may have been preempted after descheduling
637 * itself).
638 *
639 * We have to setup the MP lock for the original thread after backing
640 * out the adjustment that was made to curthread when the original
641 * was preempted.
642 */
99df837e 643 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
644 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
645 ntd->td_flags |= TDF_PREEMPT_DONE;
7fb451cb 646 ntd->td_contended = 0; /* reset contended */
8ec60c3f
MD
647
648 /*
b9eb1c19
MD
649 * The interrupt may have woken a thread up, we need to properly
650 * set the reschedule flag if the originally interrupted thread is
651 * at a lower priority.
85946b6c
MD
652 *
653 * The interrupt may not have descheduled.
8ec60c3f 654 */
85946b6c 655 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 656 need_lwkt_resched();
f9235b6d
MD
657 goto havethread_preempted;
658 }
659
b12defdc 660 /*
5411d8f1
MD
661 * Figure out switch target. If we cannot switch to our desired target
662 * look for a thread that we can switch to.
cfaeae2a 663 *
5411d8f1
MD
664 * NOTE! The limited spin loop and related parameters are extremely
665 * important for system performance, particularly for pipes and
666 * concurrent conflicting VM faults.
f9235b6d 667 */
5411d8f1
MD
668 clear_lwkt_resched();
669 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
670
671 if (ntd) {
672 do {
673 if (TD_TOKS_NOT_HELD(ntd) ||
674 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops)))
675 {
676 goto havethread;
677 }
678 ++gd->gd_cnt.v_lock_colls;
7fb451cb 679 ++ntd->td_contended; /* overflow ok */
3a06728e
MD
680#ifdef LOOPMASK
681 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
682 kprintf("lwkt_switch: excessive contended %d "
683 "thread %p\n", ntd->td_contended, ntd);
684 tsc_base = rdtsc();
685 }
686#endif
5411d8f1
MD
687 } while (ntd->td_contended < (lwkt_spin_loops >> 1));
688 upri = ntd->td_upri;
f9235b6d 689
f9235b6d 690 /*
5411d8f1
MD
691 * Bleh, the thread we wanted to switch to has a contended token.
692 * See if we can switch to another thread.
2a418930 693 *
5411d8f1
MD
694 * We generally don't want to do this because it represents a
695 * priority inversion. Do not allow the case if the thread
696 * is returning to userland (not a kernel thread) AND the thread
697 * has a lower upri.
f9235b6d 698 */
b12defdc 699 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
5411d8f1
MD
700 if (ntd->td_pri < TDPRI_KERN_LPSCHED && upri > ntd->td_upri)
701 break;
702 upri = ntd->td_upri;
b12defdc 703
5411d8f1
MD
704 /*
705 * Try this one.
706 */
707 if (TD_TOKS_NOT_HELD(ntd) ||
708 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops))) {
709 goto havethread;
710 }
7fb451cb 711 ++ntd->td_contended; /* overflow ok */
5411d8f1 712 ++gd->gd_cnt.v_lock_colls;
b12defdc 713 }
b12defdc
MD
714
715 /*
5411d8f1
MD
716 * Fall through, switch to idle thread to get us out of the current
717 * context. Since we were contended, prevent HLT by flagging a
718 * LWKT reschedule.
b12defdc 719 */
5411d8f1 720 need_lwkt_resched();
f1d1c3fa 721 }
8a8d5d85 722
5411d8f1
MD
723 /*
724 * We either contended on ntd or the runq is empty. We must switch
725 * through the idle thread to get out of the current context.
726 */
727 ntd = &gd->gd_idlethread;
728 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
729 ASSERT_NO_TOKENS_HELD(ntd);
730 cpu_time.cp_msg[0] = 0;
5411d8f1
MD
731 goto haveidle;
732
2a418930 733havethread:
b12defdc 734 /*
be71787b
MD
735 * Clear gd_idle_repeat when doing a normal switch to a non-idle
736 * thread.
f9235b6d 737 */
9ac1ee6e 738 ntd->td_wmesg = NULL;
7fb451cb 739 ntd->td_contended = 0; /* reset once scheduled */
b12defdc 740 ++gd->gd_cnt.v_swtch;
be71787b 741 gd->gd_idle_repeat = 0;
2a418930 742
f9235b6d 743havethread_preempted:
f9235b6d
MD
744 /*
745 * If the new target does not need the MP lock and we are holding it,
746 * release the MP lock. If the new target requires the MP lock we have
747 * already acquired it for the target.
8a8d5d85 748 */
2a418930 749 ;
f9235b6d
MD
750haveidle:
751 KASSERT(ntd->td_critcount,
b5d16701
MD
752 ("priority problem in lwkt_switch %d %d",
753 td->td_critcount, ntd->td_critcount));
754
94f6d86e 755 if (td != ntd) {
cc9b6223
MD
756 /*
757 * Execute the actual thread switch operation. This function
758 * returns to the current thread and returns the previous thread
759 * (which may be different from the thread we switched to).
760 *
761 * We are responsible for marking ntd as TDF_RUNNING.
762 */
121f93bc 763 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
94f6d86e 764 ++switch_count;
a1f0fb66 765 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
766 ntd->td_flags |= TDF_RUNNING;
767 lwkt_switch_return(td->td_switch(ntd));
768 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 769 }
b12defdc 770
b12defdc 771 /*
54341a3b 772 * catch-all. XXX is this strictly needed?
b12defdc
MD
773 */
774 splz_check();
54341a3b 775
37af14fe
MD
776 /* NOTE: current cpu may have changed after switch */
777 crit_exit_quick(td);
8ad65e08
MD
778}
779
cc9b6223
MD
780/*
781 * Called by assembly in the td_switch (thread restore path) for thread
782 * bootstrap cases which do not 'return' to lwkt_switch().
783 */
784void
785lwkt_switch_return(thread_t otd)
786{
cc9b6223 787 globaldata_t rgd;
3a06728e
MD
788#ifdef LOOPMASK
789 uint64_t tsc_base = rdtsc();
790#endif
791 int exiting;
792
793 exiting = otd->td_flags & TDF_EXITING;
794 cpu_ccfence();
cc9b6223
MD
795
796 /*
797 * Check if otd was migrating. Now that we are on ntd we can finish
798 * up the migration. This is a bit messy but it is the only place
799 * where td is known to be fully descheduled.
800 *
801 * We can only activate the migration if otd was migrating but not
802 * held on the cpu due to a preemption chain. We still have to
803 * clear TDF_RUNNING on the old thread either way.
804 *
805 * We are responsible for clearing the previously running thread's
806 * TDF_RUNNING.
807 */
808 if ((rgd = otd->td_migrate_gd) != NULL &&
809 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
810 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
811 (TDF_MIGRATING | TDF_RUNNING));
812 otd->td_migrate_gd = NULL;
813 otd->td_flags &= ~TDF_RUNNING;
814 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
815 } else {
816 otd->td_flags &= ~TDF_RUNNING;
817 }
2b07d9aa
MD
818
819 /*
820 * Final exit validations (see lwp_wait()). Note that otd becomes
821 * invalid the *instant* we set TDF_MP_EXITSIG.
3a06728e
MD
822 *
823 * Use the EXITING status loaded from before we clear TDF_RUNNING,
824 * because if it is not set otd becomes invalid the instant we clear
825 * TDF_RUNNING on it (otherwise, if the system is fast enough, we
826 * might 'steal' TDF_EXITING from another switch-return!).
2b07d9aa 827 */
3a06728e 828 while (exiting) {
2b07d9aa
MD
829 u_int mpflags;
830
831 mpflags = otd->td_mpflags;
832 cpu_ccfence();
833
834 if (mpflags & TDF_MP_EXITWAIT) {
835 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
836 mpflags | TDF_MP_EXITSIG)) {
837 wakeup(otd);
838 break;
839 }
840 } else {
841 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
842 mpflags | TDF_MP_EXITSIG)) {
843 wakeup(otd);
844 break;
845 }
846 }
3a06728e
MD
847
848#ifdef LOOPMASK
849 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
850 kprintf("lwkt_switch_return: excessive TDF_EXITING "
851 "thread %p\n", otd);
852 tsc_base = rdtsc();
853 }
854#endif
2b07d9aa 855 }
cc9b6223
MD
856}
857
b68b7282 858/*
96728c05 859 * Request that the target thread preempt the current thread. Preemption
54341a3b
MD
860 * can only occur if our only critical section is the one that we were called
861 * with, the relative priority of the target thread is higher, and the target
862 * thread holds no tokens. This also only works if we are not holding any
863 * spinlocks (obviously).
96728c05
MD
864 *
865 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
866 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 867 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
868 * to determine whether preemption is possible (aka usually just the crit
869 * priority of lwkt_schedule() itself).
b68b7282 870 *
54341a3b
MD
871 * Preemption is typically limited to interrupt threads.
872 *
873 * Operation works in a fairly straight-forward manner. The normal
874 * scheduling code is bypassed and we switch directly to the target
875 * thread. When the target thread attempts to block or switch away
876 * code at the base of lwkt_switch() will switch directly back to our
877 * thread. Our thread is able to retain whatever tokens it holds and
878 * if the target needs one of them the target will switch back to us
879 * and reschedule itself normally.
b68b7282
MD
880 */
881void
f9235b6d 882lwkt_preempt(thread_t ntd, int critcount)
b68b7282 883{
46a3f46d 884 struct globaldata *gd = mycpu;
cc9b6223 885 thread_t xtd;
0a3f9b47 886 thread_t td;
2d910aaf 887 int save_gd_intr_nesting_level;
b68b7282 888
26a0694b 889 /*
96728c05
MD
890 * The caller has put us in a critical section. We can only preempt
891 * if the caller of the caller was not in a critical section (basically
f9235b6d 892 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 893 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 894 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
895 *
896 * YYY The target thread must be in a critical section (else it must
897 * inherit our critical section? I dunno yet).
26a0694b 898 */
f9235b6d 899 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 900
b12defdc 901 td = gd->gd_curthread;
fbc024e4
MD
902 if (preempt_enable == 0) {
903 ++preempt_miss;
904 return;
905 }
f9235b6d 906 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
907 ++preempt_miss;
908 return;
909 }
f9235b6d 910 if (td->td_critcount > critcount) {
96728c05
MD
911 ++preempt_miss;
912 return;
913 }
121f93bc
MD
914 if (td->td_cscount) {
915 ++preempt_miss;
916 return;
917 }
46a3f46d 918 if (ntd->td_gd != gd) {
96728c05
MD
919 ++preempt_miss;
920 return;
921 }
ee89e80b 922
41a01a4d 923 /*
77912481
MD
924 * We don't have to check spinlocks here as they will also bump
925 * td_critcount.
d3d1cbc8
MD
926 *
927 * Do not try to preempt if the target thread is holding any tokens.
928 * We could try to acquire the tokens but this case is so rare there
929 * is no need to support it.
41a01a4d 930 */
0846e4ce 931 KKASSERT(gd->gd_spinlocks == 0);
77912481 932
3b998fa9 933 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 934 ++preempt_miss;
d3d1cbc8
MD
935 return;
936 }
26a0694b
MD
937 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
938 ++preempt_weird;
939 return;
940 }
941 if (ntd->td_preempted) {
4b5f931b 942 ++preempt_hit;
26a0694b 943 return;
b68b7282 944 }
da0b0e8b 945 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 946
8ec60c3f
MD
947 /*
948 * Since we are able to preempt the current thread, there is no need to
949 * call need_lwkt_resched().
2d910aaf
MD
950 *
951 * We must temporarily clear gd_intr_nesting_level around the switch
952 * since switchouts from the target thread are allowed (they will just
953 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
954 *
955 * A preemption must switch back to the original thread, assert the
956 * case.
8ec60c3f 957 */
26a0694b
MD
958 ++preempt_hit;
959 ntd->td_preempted = td;
960 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 961 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
962 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
963 gd->gd_intr_nesting_level = 0;
121f93bc
MD
964
965 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
cc9b6223
MD
966 ntd->td_flags |= TDF_RUNNING;
967 xtd = td->td_switch(ntd);
968 KKASSERT(xtd == ntd);
969 lwkt_switch_return(xtd);
2d910aaf 970 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 971
26a0694b
MD
972 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
973 ntd->td_preempted = NULL;
974 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
975}
976
f1d1c3fa 977/*
faaeffac 978 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
979 * This will work inside a critical section but not inside a hard code
980 * section.
ef0fdad1 981 *
f1d1c3fa
MD
982 * (self contained on a per cpu basis)
983 */
984void
faaeffac 985splz_check(void)
f1d1c3fa 986{
7966cb69
MD
987 globaldata_t gd = mycpu;
988 thread_t td = gd->gd_curthread;
ef0fdad1 989
4a28fe22
MD
990 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
991 gd->gd_intr_nesting_level == 0 &&
992 td->td_nest_count < 2)
993 {
f1d1c3fa 994 splz();
4a28fe22
MD
995 }
996}
997
998/*
999 * This version is integrated into crit_exit, reqflags has already
1000 * been tested but td_critcount has not.
1001 *
1002 * We only want to execute the splz() on the 1->0 transition of
1003 * critcount and not in a hard code section or if too deeply nested.
925040f2 1004 *
0846e4ce 1005 * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0.
4a28fe22
MD
1006 */
1007void
1008lwkt_maybe_splz(thread_t td)
1009{
1010 globaldata_t gd = td->td_gd;
1011
1012 if (td->td_critcount == 0 &&
1013 gd->gd_intr_nesting_level == 0 &&
1014 td->td_nest_count < 2)
1015 {
1016 splz();
1017 }
f1d1c3fa
MD
1018}
1019
e6546af9
MD
1020/*
1021 * Drivers which set up processing co-threads can call this function to
1022 * run the co-thread at a higher priority and to allow it to preempt
1023 * normal threads.
1024 */
1025void
1026lwkt_set_interrupt_support_thread(void)
1027{
1028 thread_t td = curthread;
1029
1030 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1031 td->td_flags |= TDF_INTTHREAD;
1032 td->td_preemptable = lwkt_preempt;
1033}
1034
1035
8ad65e08 1036/*
f9235b6d
MD
1037 * This function is used to negotiate a passive release of the current
1038 * process/lwp designation with the user scheduler, allowing the user
1039 * scheduler to schedule another user thread. The related kernel thread
1040 * (curthread) continues running in the released state.
8ad65e08
MD
1041 */
1042void
f9235b6d 1043lwkt_passive_release(struct thread *td)
8ad65e08 1044{
f9235b6d
MD
1045 struct lwp *lp = td->td_lwp;
1046
1047 td->td_release = NULL;
1048 lwkt_setpri_self(TDPRI_KERN_USER);
d992c377 1049
f9235b6d 1050 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1051}
1052
f9235b6d 1053
3824f392 1054/*
d2d8515b
MD
1055 * This implements a LWKT yield, allowing a kernel thread to yield to other
1056 * kernel threads at the same or higher priority. This function can be
1057 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1058 *
d2d8515b
MD
1059 * Most kernel threads run at the same priority in order to allow equal
1060 * sharing.
f9235b6d
MD
1061 *
1062 * (self contained on a per cpu basis)
3824f392
MD
1063 */
1064void
f9235b6d 1065lwkt_yield(void)
3824f392 1066{
f9235b6d
MD
1067 globaldata_t gd = mycpu;
1068 thread_t td = gd->gd_curthread;
3824f392 1069
fbe96076
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1070 /*
1071 * Should never be called with spinlocks held but there is a path
1072 * via ACPI where it might happen.
1073 */
1074 if (gd->gd_spinlocks)
1075 return;
1076
1077 /*
1078 * Safe to call splz if we are not too-heavily nested.
1079 */
f9235b6d
MD
1080 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1081 splz();
fbe96076
MD
1082
1083 /*
1084 * Caller allows switching
1085 */
85946b6c 1086 if (lwkt_resched_wanted()) {
f9235b6d
MD
1087 lwkt_schedule_self(curthread);
1088 lwkt_switch();
f9235b6d 1089 }
3824f392
MD
1090}
1091
40504122
MD
1092/*
1093 * The quick version processes pending interrupts and higher-priority
1094 * LWKT threads but will not round-robin same-priority LWKT threads.
de4d4cb0
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1095 *
1096 * When called while attempting to return to userland the only same-pri
1097 * threads are the ones which have already tried to become the current
1098 * user process.
40504122
MD
1099 */
1100void
1101lwkt_yield_quick(void)
1102{
1103 globaldata_t gd = mycpu;
1104 thread_t td = gd->gd_curthread;
1105
1106 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1107 splz();
1108 if (lwkt_resched_wanted()) {
9c99cb33 1109 crit_enter();
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1110 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1111 clear_lwkt_resched();
1112 } else {
1113 lwkt_schedule_self(curthread);
1114 lwkt_switch();
1115 }
9c99cb33 1116 crit_exit();
40504122
MD
1117 }
1118}
1119
3824f392 1120/*
f9235b6d
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1121 * This yield is designed for kernel threads with a user context.
1122 *
1123 * The kernel acting on behalf of the user is potentially cpu-bound,
1124 * this function will efficiently allow other threads to run and also
1125 * switch to other processes by releasing.
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1126 *
1127 * The lwkt_user_yield() function is designed to have very low overhead
1128 * if no yield is determined to be needed.
1129 */
1130void
1131lwkt_user_yield(void)
1132{
f9235b6d
MD
1133 globaldata_t gd = mycpu;
1134 thread_t td = gd->gd_curthread;
1135
fbe96076
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1136 /*
1137 * Should never be called with spinlocks held but there is a path
1138 * via ACPI where it might happen.
1139 */
1140 if (gd->gd_spinlocks)
1141 return;
1142
f9235b6d
MD
1143 /*
1144 * Always run any pending interrupts in case we are in a critical
1145 * section.
1146 */
1147 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1148 splz();
3824f392 1149
3824f392 1150 /*
f9235b6d
MD
1151 * Switch (which forces a release) if another kernel thread needs
1152 * the cpu, if userland wants us to resched, or if our kernel
1153 * quantum has run out.
3824f392 1154 */
f9235b6d 1155 if (lwkt_resched_wanted() ||
85946b6c 1156 user_resched_wanted())
f9235b6d 1157 {
3824f392 1158 lwkt_switch();
3824f392
MD
1159 }
1160
f9235b6d 1161#if 0
3824f392 1162 /*
f9235b6d
MD
1163 * Reacquire the current process if we are released.
1164 *
1165 * XXX not implemented atm. The kernel may be holding locks and such,
1166 * so we want the thread to continue to receive cpu.
3824f392 1167 */
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1168 if (td->td_release == NULL && lp) {
1169 lp->lwp_proc->p_usched->acquire_curproc(lp);
1170 td->td_release = lwkt_passive_release;
1171 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1172 }
f9235b6d 1173#endif
b9eb1c19
MD
1174}
1175
8ad65e08 1176/*
f1d1c3fa
MD
1177 * Generic schedule. Possibly schedule threads belonging to other cpus and
1178 * deal with threads that might be blocked on a wait queue.
1179 *
0a3f9b47
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1180 * We have a little helper inline function which does additional work after
1181 * the thread has been enqueued, including dealing with preemption and
1182 * setting need_lwkt_resched() (which prevents the kernel from returning
1183 * to userland until it has processed higher priority threads).
6330a558
MD
1184 *
1185 * It is possible for this routine to be called after a failed _enqueue
1186 * (due to the target thread migrating, sleeping, or otherwise blocked).
1187 * We have to check that the thread is actually on the run queue!
8ad65e08 1188 */
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MD
1189static __inline
1190void
85946b6c 1191_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1192{
6330a558 1193 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1194 if (ntd->td_preemptable) {
f9235b6d 1195 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1196 }
0a3f9b47
MD
1197 }
1198}
1199
361d01dd 1200static __inline
8ad65e08 1201void
85946b6c 1202_lwkt_schedule(thread_t td)
8ad65e08 1203{
37af14fe
MD
1204 globaldata_t mygd = mycpu;
1205
cf709dd2
MD
1206 KASSERT(td != &td->td_gd->gd_idlethread,
1207 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1208 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1209 crit_enter_gd(mygd);
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MD
1210 KKASSERT(td->td_lwp == NULL ||
1211 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1212
37af14fe 1213 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1214 _lwkt_enqueue(td);
1215 } else {
f1d1c3fa 1216 /*
7cd8d145
MD
1217 * If we own the thread, there is no race (since we are in a
1218 * critical section). If we do not own the thread there might
1219 * be a race but the target cpu will deal with it.
f1d1c3fa 1220 */
7cd8d145 1221 if (td->td_gd == mygd) {
9d265729 1222 _lwkt_enqueue(td);
85946b6c 1223 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1224 } else {
e381e77c 1225 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1226 }
8ad65e08 1227 }
37af14fe 1228 crit_exit_gd(mygd);
8ad65e08
MD
1229}
1230
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MD
1231void
1232lwkt_schedule(thread_t td)
1233{
85946b6c 1234 _lwkt_schedule(td);
361d01dd
MD
1235}
1236
1237void
85946b6c 1238lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1239{
85946b6c 1240 _lwkt_schedule(td);
361d01dd
MD
1241}
1242
e381e77c
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1243/*
1244 * When scheduled remotely if frame != NULL the IPIQ is being
1245 * run via doreti or an interrupt then preemption can be allowed.
1246 *
1247 * To allow preemption we have to drop the critical section so only
1248 * one is present in _lwkt_schedule_post.
1249 */
1250static void
1251lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1252{
1253 thread_t td = curthread;
1254 thread_t ntd = arg;
1255
1256 if (frame && ntd->td_preemptable) {
1257 crit_exit_noyield(td);
85946b6c 1258 _lwkt_schedule(ntd);
e381e77c
MD
1259 crit_enter_quick(td);
1260 } else {
85946b6c 1261 _lwkt_schedule(ntd);
e381e77c
MD
1262 }
1263}
1264
d9eea1a5 1265/*
52eedfb5
MD
1266 * Thread migration using a 'Pull' method. The thread may or may not be
1267 * the current thread. It MUST be descheduled and in a stable state.
1268 * lwkt_giveaway() must be called on the cpu owning the thread.
1269 *
1270 * At any point after lwkt_giveaway() is called, the target cpu may
1271 * 'pull' the thread by calling lwkt_acquire().
1272 *
ae8e83e6
MD
1273 * We have to make sure the thread is not sitting on a per-cpu tsleep
1274 * queue or it will blow up when it moves to another cpu.
1275 *
52eedfb5 1276 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1277 */
52eedfb5
MD
1278void
1279lwkt_giveaway(thread_t td)
1280{
3b4192fb 1281 globaldata_t gd = mycpu;
52eedfb5 1282
3b4192fb
MD
1283 crit_enter_gd(gd);
1284 if (td->td_flags & TDF_TSLEEPQ)
1285 tsleep_remove(td);
1286 KKASSERT(td->td_gd == gd);
1287 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1288 td->td_flags |= TDF_MIGRATING;
1289 crit_exit_gd(gd);
52eedfb5
MD
1290}
1291
a2a5ad0d
MD
1292void
1293lwkt_acquire(thread_t td)
1294{
37af14fe
MD
1295 globaldata_t gd;
1296 globaldata_t mygd;
a2a5ad0d 1297
52eedfb5 1298 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1299 gd = td->td_gd;
37af14fe 1300 mygd = mycpu;
52eedfb5 1301 if (gd != mycpu) {
3a06728e
MD
1302#ifdef LOOPMASK
1303 uint64_t tsc_base = rdtsc();
1304#endif
35238fa5 1305 cpu_lfence();
52eedfb5 1306 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1307 crit_enter_gd(mygd);
cfaeae2a 1308 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23 1309 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
df910c23 1310 lwkt_process_ipiq();
52eedfb5 1311 cpu_lfence();
a86ce0cd
MD
1312#ifdef _KERNEL_VIRTUAL
1313 pthread_yield();
3a06728e
MD
1314#endif
1315#ifdef LOOPMASK
1316 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
1317 kprintf("lwkt_acquire: stuck td %p td->td_flags %08x\n",
1318 td, td->td_flags);
1319 tsc_base = rdtsc();
1320 }
a86ce0cd 1321#endif
df910c23 1322 }
cfaeae2a 1323 DEBUG_POP_INFO();
562273ea 1324 cpu_mfence();
37af14fe 1325 td->td_gd = mygd;
52eedfb5
MD
1326 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1327 td->td_flags &= ~TDF_MIGRATING;
1328 crit_exit_gd(mygd);
1329 } else {
1330 crit_enter_gd(mygd);
1331 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1332 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1333 crit_exit_gd(mygd);
a2a5ad0d
MD
1334 }
1335}
1336
f1d1c3fa
MD
1337/*
1338 * Generic deschedule. Descheduling threads other then your own should be
1339 * done only in carefully controlled circumstances. Descheduling is
1340 * asynchronous.
1341 *
1342 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1343 */
1344void
1345lwkt_deschedule(thread_t td)
1346{
f1d1c3fa
MD
1347 crit_enter();
1348 if (td == curthread) {
1349 _lwkt_dequeue(td);
1350 } else {
a72187e9 1351 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1352 _lwkt_dequeue(td);
1353 } else {
b8a98473 1354 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1355 }
1356 }
1357 crit_exit();
1358}
1359
4b5f931b
MD
1360/*
1361 * Set the target thread's priority. This routine does not automatically
1362 * switch to a higher priority thread, LWKT threads are not designed for
1363 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1364 */
1365void
1366lwkt_setpri(thread_t td, int pri)
1367{
f9235b6d
MD
1368 if (td->td_pri != pri) {
1369 KKASSERT(pri >= 0);
1370 crit_enter();
1371 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1372 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1373 _lwkt_dequeue(td);
1374 td->td_pri = pri;
1375 _lwkt_enqueue(td);
1376 } else {
1377 td->td_pri = pri;
1378 }
1379 crit_exit();
26a0694b 1380 }
26a0694b
MD
1381}
1382
03bd0a5e
MD
1383/*
1384 * Set the initial priority for a thread prior to it being scheduled for
1385 * the first time. The thread MUST NOT be scheduled before or during
1386 * this call. The thread may be assigned to a cpu other then the current
1387 * cpu.
1388 *
1389 * Typically used after a thread has been created with TDF_STOPPREQ,
1390 * and before the thread is initially scheduled.
1391 */
1392void
1393lwkt_setpri_initial(thread_t td, int pri)
1394{
1395 KKASSERT(pri >= 0);
1396 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1397 td->td_pri = pri;
03bd0a5e
MD
1398}
1399
26a0694b
MD
1400void
1401lwkt_setpri_self(int pri)
1402{
1403 thread_t td = curthread;
1404
4b5f931b
MD
1405 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1406 crit_enter();
1407 if (td->td_flags & TDF_RUNQ) {
1408 _lwkt_dequeue(td);
f9235b6d 1409 td->td_pri = pri;
4b5f931b
MD
1410 _lwkt_enqueue(td);
1411 } else {
f9235b6d 1412 td->td_pri = pri;
4b5f931b
MD
1413 }
1414 crit_exit();
1415}
1416
f9235b6d 1417/*
85946b6c 1418 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1419 */
1420void
85946b6c 1421lwkt_schedulerclock(thread_t td)
f9235b6d 1422{
85946b6c
MD
1423 globaldata_t gd = td->td_gd;
1424 thread_t xtd;
2a418930 1425
85946b6c
MD
1426 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1427 /*
1428 * If the current thread is at the head of the runq shift it to the
1429 * end of any equal-priority threads and request a LWKT reschedule
1430 * if it moved.
d992c377
MD
1431 *
1432 * Ignore upri in this situation. There will only be one user thread
1433 * in user mode, all others will be user threads running in kernel
1434 * mode and we have to make sure they get some cpu.
85946b6c
MD
1435 */
1436 xtd = TAILQ_NEXT(td, td_threadq);
1437 if (xtd && xtd->td_pri == td->td_pri) {
1438 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1439 while (xtd && xtd->td_pri == td->td_pri)
1440 xtd = TAILQ_NEXT(xtd, td_threadq);
1441 if (xtd)
1442 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1443 else
1444 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1445 need_lwkt_resched();
f9235b6d 1446 }
85946b6c
MD
1447 } else {
1448 /*
1449 * If we scheduled a thread other than the one at the head of the
1450 * queue always request a reschedule every tick.
1451 */
1452 need_lwkt_resched();
f9235b6d
MD
1453 }
1454}
1455
5d21b981 1456/*
52eedfb5
MD
1457 * Migrate the current thread to the specified cpu.
1458 *
cc9b6223
MD
1459 * This is accomplished by descheduling ourselves from the current cpu
1460 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1461 * 'old' thread wants to migrate after it has been completely switched out
1462 * and will complete the migration.
1463 *
1464 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1465 *
1466 * We must be sure to release our current process designation (if a user
1467 * process) before clearing out any tsleepq we are on because the release
1468 * code may re-add us.
ae8e83e6
MD
1469 *
1470 * We must be sure to remove ourselves from the current cpu's tsleepq
1471 * before potentially moving to another queue. The thread can be on
1472 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1473 */
5d21b981
MD
1474
1475void
1476lwkt_setcpu_self(globaldata_t rgd)
1477{
5d21b981
MD
1478 thread_t td = curthread;
1479
1480 if (td->td_gd != rgd) {
1481 crit_enter_quick(td);
cc9b6223 1482
95858b91
MD
1483 if (td->td_release)
1484 td->td_release(td);
ae8e83e6 1485 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1486 tsleep_remove(td);
cc9b6223
MD
1487
1488 /*
1489 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1490 * trying to deschedule ourselves and switch away, then deschedule
1491 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1492 * call lwkt_switch() to complete the operation.
1493 */
5d21b981
MD
1494 td->td_flags |= TDF_MIGRATING;
1495 lwkt_deschedule_self(td);
52eedfb5 1496 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1497 td->td_migrate_gd = rgd;
5d21b981 1498 lwkt_switch();
cc9b6223
MD
1499
1500 /*
1501 * We are now on the target cpu
1502 */
1503 KKASSERT(rgd == mycpu);
52eedfb5 1504 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1505 crit_exit_quick(td);
1506 }
5d21b981
MD
1507}
1508
ecdefdda
MD
1509void
1510lwkt_migratecpu(int cpuid)
1511{
ecdefdda
MD
1512 globaldata_t rgd;
1513
1514 rgd = globaldata_find(cpuid);
1515 lwkt_setcpu_self(rgd);
ecdefdda
MD
1516}
1517
5d21b981
MD
1518/*
1519 * Remote IPI for cpu migration (called while in a critical section so we
cc9b6223
MD
1520 * do not have to enter another one).
1521 *
1522 * The thread (td) has already been completely descheduled from the
1523 * originating cpu and we can simply assert the case. The thread is
1524 * assigned to the new cpu and enqueued.
5d21b981 1525 *
cc9b6223 1526 * The thread will re-add itself to tdallq when it resumes execution.
5d21b981
MD
1527 */
1528static void
1529lwkt_setcpu_remote(void *arg)
1530{
1531 thread_t td = arg;
1532 globaldata_t gd = mycpu;
1533
cc9b6223 1534 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1535 td->td_gd = gd;
562273ea 1536 cpu_mfence();
5d21b981 1537 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1538 KKASSERT(td->td_migrate_gd == NULL);
4643740a
MD
1539 KKASSERT(td->td_lwp == NULL ||
1540 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
5d21b981
MD
1541 _lwkt_enqueue(td);
1542}
1543
553ea3c8 1544struct lwp *
4b5f931b
MD
1545lwkt_preempted_proc(void)
1546{
73e4f7b9 1547 thread_t td = curthread;
4b5f931b
MD
1548 while (td->td_preempted)
1549 td = td->td_preempted;
553ea3c8 1550 return(td->td_lwp);
4b5f931b
MD
1551}
1552
99df837e
MD
1553/*
1554 * Create a kernel process/thread/whatever. It shares it's address space
1555 * with proc0 - ie: kernel only.
1556 *
d2d8515b
MD
1557 * If the cpu is not specified one will be selected. In the future
1558 * specifying a cpu of -1 will enable kernel thread migration between
1559 * cpus.
99df837e
MD
1560 */
1561int
c9e9fb21
MD
1562lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1563 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1564{
73e4f7b9 1565 thread_t td;
e2565a42 1566 __va_list ap;
99df837e 1567
d3d32139 1568 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1569 tdflags);
a2a5ad0d
MD
1570 if (tdp)
1571 *tdp = td;
709799ea 1572 cpu_set_thread_handler(td, lwkt_exit, func, arg);
99df837e
MD
1573
1574 /*
1575 * Set up arg0 for 'ps' etc
1576 */
e2565a42 1577 __va_start(ap, fmt);
379210cb 1578 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1579 __va_end(ap);
99df837e
MD
1580
1581 /*
1582 * Schedule the thread to run
1583 */
4643740a
MD
1584 if (td->td_flags & TDF_NOSTART)
1585 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1586 else
4643740a 1587 lwkt_schedule(td);
99df837e
MD
1588 return 0;
1589}
1590
1591/*
1592 * Destroy an LWKT thread. Warning! This function is not called when
1593 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1594 * uses a different reaping mechanism.
1595 */
1596void
1597lwkt_exit(void)
1598{
1599 thread_t td = curthread;
c070746a 1600 thread_t std;
8826f33a 1601 globaldata_t gd;
99df837e 1602
2883d2d8
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1603 /*
1604 * Do any cleanup that might block here
1605 */
99df837e 1606 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1607 kprintf("kthread %p %s has exited\n", td, td->td_comm);
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1608 biosched_done(td);
1609 dsched_exit_thread(td);
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1610
1611 /*
1612 * Get us into a critical section to interlock gd_freetd and loop
1613 * until we can get it freed.
1614 *
1615 * We have to cache the current td in gd_freetd because objcache_put()ing
1616 * it would rip it out from under us while our thread is still active.
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1617 *
1618 * We are the current thread so of course our own TDF_RUNNING bit will
1619 * be set, so unlike the lwp reap code we don't wait for it to clear.
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1620 */
1621 gd = mycpu;
37af14fe 1622 crit_enter_quick(td);
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1623 for (;;) {
1624 if (td->td_refs) {
1625 tsleep(td, 0, "tdreap", 1);
1626 continue;
1627 }
1628 if ((std = gd->gd_freetd) != NULL) {
1629 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1630 gd->gd_freetd = NULL;
1631 objcache_put(thread_cache, std);
1632 continue;
1633 }
1634 break;
c070746a 1635 }
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1636
1637 /*
1638 * Remove thread resources from kernel lists and deschedule us for
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1639 * the last time. We cannot block after this point or we may end
1640 * up with a stale td on the tsleepq.
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1641 *
1642 * None of this may block, the critical section is the only thing
1643 * protecting tdallq and the only thing preventing new lwkt_hold()
1644 * thread refs now.
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1645 */
1646 if (td->td_flags & TDF_TSLEEPQ)
1647 tsleep_remove(td);
37af14fe 1648 lwkt_deschedule_self(td);
e56e4dea 1649 lwkt_remove_tdallq(td);
74c9628e 1650 KKASSERT(td->td_refs == 0);
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1651
1652 /*
1653 * Final cleanup
1654 */
1655 KKASSERT(gd->gd_freetd == NULL);
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1656 if (td->td_flags & TDF_ALLOCATED_THREAD)
1657 gd->gd_freetd = td;
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1658 cpu_thread_exit();
1659}
1660
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1661void
1662lwkt_remove_tdallq(thread_t td)
1663{
1664 KKASSERT(td->td_gd == mycpu);
1665 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1666}
1667
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1668/*
1669 * Code reduction and branch prediction improvements. Call/return
1670 * overhead on modern cpus often degenerates into 0 cycles due to
1671 * the cpu's branch prediction hardware and return pc cache. We
1672 * can take advantage of this by not inlining medium-complexity
1673 * functions and we can also reduce the branch prediction impact
1674 * by collapsing perfectly predictable branches into a single
1675 * procedure instead of duplicating it.
1676 *
1677 * Is any of this noticeable? Probably not, so I'll take the
1678 * smaller code size.
1679 */
1680void
b6468f56 1681crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1682{
b6468f56 1683 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1684}
1685
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1686void
1687crit_panic(void)
1688{
1689 thread_t td = curthread;
850634cc 1690 int lcrit = td->td_critcount;
2d93b37a 1691
850634cc
AH
1692 td->td_critcount = 0;
1693 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1694 /* NOT REACHED */
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1695}
1696
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1697/*
1698 * Called from debugger/panic on cpus which have been stopped. We must still
b19f40a4 1699 * process the IPIQ while stopped.
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1700 *
1701 * If we are dumping also try to process any pending interrupts. This may
1702 * or may not work depending on the state of the cpu at the point it was
1703 * stopped.
1704 */
1705void
1706lwkt_smp_stopped(void)
1707{
1708 globaldata_t gd = mycpu;
1709
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1710 if (dumping) {
1711 lwkt_process_ipiq();
b19f40a4 1712 --gd->gd_intr_nesting_level;
bd8015ca 1713 splz();
b19f40a4 1714 ++gd->gd_intr_nesting_level;
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1715 } else {
1716 lwkt_process_ipiq();
1717 }
63cff036 1718 cpu_smp_stopped();
bd8015ca 1719}