Disable making i915kms compilable into the kernel.
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
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>
684a93c4 58#include <sys/mplock2.h>
f1d1c3fa 59
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60#include <sys/dsched.h>
61
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62#include <vm/vm.h>
63#include <vm/vm_param.h>
64#include <vm/vm_kern.h>
65#include <vm/vm_object.h>
66#include <vm/vm_page.h>
67#include <vm/vm_map.h>
68#include <vm/vm_pager.h>
69#include <vm/vm_extern.h>
7d0bac62 70
99df837e 71#include <machine/stdarg.h>
96728c05 72#include <machine/smp.h>
99df837e 73
d850923c
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74#if !defined(KTR_CTXSW)
75#define KTR_CTXSW KTR_ALL
76#endif
77KTR_INFO_MASTER(ctxsw);
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78KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td);
79KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td);
80KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm);
81KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td);
1541028a 82
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83static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
84
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85#ifdef INVARIANTS
86static int panic_on_cscount = 0;
87#endif
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88static __int64_t switch_count = 0;
89static __int64_t preempt_hit = 0;
90static __int64_t preempt_miss = 0;
91static __int64_t preempt_weird = 0;
fb0f29c4 92static int lwkt_use_spin_port;
40aaf5fc 93static struct objcache *thread_cache;
a46b4a23 94int cpu_mwait_spin = 0;
05220613 95
e381e77c 96static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 97static void lwkt_setcpu_remote(void *arg);
e381e77c 98
0855a2af
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99extern void cpu_heavy_restore(void);
100extern void cpu_lwkt_restore(void);
101extern void cpu_kthread_restore(void);
102extern void cpu_idle_restore(void);
103
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104/*
105 * We can make all thread ports use the spin backend instead of the thread
106 * backend. This should only be set to debug the spin backend.
107 */
108TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
109
0f7a3396 110#ifdef INVARIANTS
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111SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
112 "Panic if attempting to switch lwkt's while mastering cpusync");
0f7a3396 113#endif
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114SYSCTL_INT(_hw, OID_AUTO, cpu_mwait_spin, CTLFLAG_RW, &cpu_mwait_spin, 0,
115 "monitor/mwait target state");
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116SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
117 "Number of switched threads");
9733f757 118SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 119 "Successful preemption events");
9733f757 120SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
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121 "Failed preemption events");
122SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
123 "Number of preempted threads.");
b12defdc 124static int fairq_enable = 0;
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125SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
126 &fairq_enable, 0, "Turn on fairq priority accumulators");
85946b6c 127static int fairq_bypass = -1;
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128SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
129 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
130extern int lwkt_sched_debug;
131int lwkt_sched_debug = 0;
132SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
133 &lwkt_sched_debug, 0, "Scheduler debug");
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134static int lwkt_spin_loops = 10;
135SYSCTL_INT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
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136 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
137static int lwkt_spin_reseq = 0;
138SYSCTL_INT(_lwkt, OID_AUTO, spin_reseq, CTLFLAG_RW,
139 &lwkt_spin_reseq, 0, "Scheduler resequencer enable");
140static int lwkt_spin_monitor = 0;
141SYSCTL_INT(_lwkt, OID_AUTO, spin_monitor, CTLFLAG_RW,
142 &lwkt_spin_monitor, 0, "Scheduler uses monitor/mwait");
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143static int lwkt_spin_fatal = 0; /* disabled */
144SYSCTL_INT(_lwkt, OID_AUTO, spin_fatal, CTLFLAG_RW,
145 &lwkt_spin_fatal, 0, "LWKT scheduler spin loops till fatal panic");
fbc024e4 146static int preempt_enable = 1;
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147SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
148 &preempt_enable, 0, "Enable preemption");
7b234d8c 149static int lwkt_cache_threads = 0;
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150SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
151 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 152
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153static __cachealign int lwkt_cseq_rindex;
154static __cachealign int lwkt_cseq_windex;
05220613 155
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156/*
157 * These helper procedures handle the runq, they can only be called from
158 * within a critical section.
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159 *
160 * WARNING! Prior to SMP being brought up it is possible to enqueue and
161 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
162 * instead of 'mycpu' when referencing the globaldata structure. Once
163 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 164 */
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165static __inline
166void
167_lwkt_dequeue(thread_t td)
168{
169 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 170 struct globaldata *gd = td->td_gd;
4b5f931b 171
f1d1c3fa 172 td->td_flags &= ~TDF_RUNQ;
f9235b6d 173 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
de4d4cb0 174 --gd->gd_tdrunqcount;
f9235b6d 175 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 176 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
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177 }
178}
179
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180/*
181 * Priority enqueue.
182 *
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183 * There are a limited number of lwkt threads runnable since user
184 * processes only schedule one at a time per cpu. However, there can
185 * be many user processes in kernel mode exiting from a tsleep() which
e3e6be1f 186 * become runnable.
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187 *
188 * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and
189 * will ignore user priority. This is to ensure that user threads in
190 * kernel mode get cpu at some point regardless of what the user
191 * scheduler thinks.
f9235b6d 192 */
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193static __inline
194void
195_lwkt_enqueue(thread_t td)
196{
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197 thread_t xtd;
198
7f5d7ed7 199 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 200 struct globaldata *gd = td->td_gd;
4b5f931b 201
f1d1c3fa 202 td->td_flags |= TDF_RUNQ;
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203 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
204 if (xtd == NULL) {
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205 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
206 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 207 } else {
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208 /*
209 * NOTE: td_upri - higher numbers more desireable, same sense
210 * as td_pri (typically reversed from lwp_upri).
211 *
212 * In the equal priority case we want the best selection
213 * at the beginning so the less desireable selections know
214 * that they have to setrunqueue/go-to-another-cpu, even
215 * though it means switching back to the 'best' selection.
216 * This also avoids degenerate situations when many threads
217 * are runnable or waking up at the same time.
218 *
219 * If upri matches exactly place at end/round-robin.
220 */
d992c377 221 while (xtd &&
e3e6be1f 222 (xtd->td_pri >= td->td_pri ||
d992c377 223 (xtd->td_pri == td->td_pri &&
e3e6be1f 224 xtd->td_upri >= td->td_upri))) {
85946b6c 225 xtd = TAILQ_NEXT(xtd, td_threadq);
d992c377 226 }
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227 if (xtd)
228 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
229 else
230 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 231 }
de4d4cb0 232 ++gd->gd_tdrunqcount;
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233
234 /*
85946b6c 235 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 236 */
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237 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
238 need_lwkt_resched();
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239 }
240}
8ad65e08 241
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242static __boolean_t
243_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
244{
245 struct thread *td = (struct thread *)obj;
246
247 td->td_kstack = NULL;
248 td->td_kstack_size = 0;
249 td->td_flags = TDF_ALLOCATED_THREAD;
4643740a 250 td->td_mpflags = 0;
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251 return (1);
252}
253
254static void
255_lwkt_thread_dtor(void *obj, void *privdata)
256{
257 struct thread *td = (struct thread *)obj;
258
259 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
260 ("_lwkt_thread_dtor: not allocated from objcache"));
261 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
262 td->td_kstack_size > 0,
263 ("_lwkt_thread_dtor: corrupted stack"));
264 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
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265 td->td_kstack = NULL;
266 td->td_flags = 0;
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267}
268
269/*
270 * Initialize the lwkt s/system.
765b1ae0 271 *
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272 * Nominally cache up to 32 thread + kstack structures. Cache more on
273 * systems with a lot of cpu cores.
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274 */
275void
276lwkt_init(void)
277{
765b1ae0 278 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
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279 if (lwkt_cache_threads == 0) {
280 lwkt_cache_threads = ncpus * 4;
281 if (lwkt_cache_threads < 32)
282 lwkt_cache_threads = 32;
283 }
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MD
284 thread_cache = objcache_create_mbacked(
285 M_THREAD, sizeof(struct thread),
2fce2579 286 0, lwkt_cache_threads,
765b1ae0 287 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
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NT
288}
289
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290/*
291 * Schedule a thread to run. As the current thread we can always safely
292 * schedule ourselves, and a shortcut procedure is provided for that
293 * function.
294 *
295 * (non-blocking, self contained on a per cpu basis)
296 */
297void
298lwkt_schedule_self(thread_t td)
299{
cfaeae2a 300 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 301 crit_enter_quick(td);
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302 KASSERT(td != &td->td_gd->gd_idlethread,
303 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
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304 KKASSERT(td->td_lwp == NULL ||
305 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
37af14fe 306 _lwkt_enqueue(td);
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307 crit_exit_quick(td);
308}
309
310/*
311 * Deschedule a thread.
312 *
313 * (non-blocking, self contained on a per cpu basis)
314 */
315void
316lwkt_deschedule_self(thread_t td)
317{
318 crit_enter_quick(td);
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319 _lwkt_dequeue(td);
320 crit_exit_quick(td);
321}
322
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323/*
324 * LWKTs operate on a per-cpu basis
325 *
73e4f7b9 326 * WARNING! Called from early boot, 'mycpu' may not work yet.
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327 */
328void
329lwkt_gdinit(struct globaldata *gd)
330{
f9235b6d 331 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 332 TAILQ_INIT(&gd->gd_tdallq);
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333}
334
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335/*
336 * Create a new thread. The thread must be associated with a process context
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337 * or LWKT start address before it can be scheduled. If the target cpu is
338 * -1 the thread will be created on the current cpu.
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339 *
340 * If you intend to create a thread without a process context this function
341 * does everything except load the startup and switcher function.
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342 */
343thread_t
d3d32139 344lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 345{
d2d8515b 346 static int cpu_rotator;
c070746a 347 globaldata_t gd = mycpu;
99df837e 348 void *stack;
7d0bac62 349
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MD
350 /*
351 * If static thread storage is not supplied allocate a thread. Reuse
352 * a cached free thread if possible. gd_freetd is used to keep an exiting
353 * thread intact through the exit.
354 */
ef0fdad1 355 if (td == NULL) {
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MD
356 crit_enter_gd(gd);
357 if ((td = gd->gd_freetd) != NULL) {
358 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
359 TDF_RUNQ)) == 0);
c070746a 360 gd->gd_freetd = NULL;
cf709dd2 361 } else {
c070746a 362 td = objcache_get(thread_cache, M_WAITOK);
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363 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
364 TDF_RUNQ)) == 0);
365 }
366 crit_exit_gd(gd);
40aaf5fc 367 KASSERT((td->td_flags &
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MD
368 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
369 TDF_ALLOCATED_THREAD,
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370 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
371 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 372 }
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373
374 /*
375 * Try to reuse cached stack.
376 */
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377 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
378 if (flags & TDF_ALLOCATED_STACK) {
e4846942 379 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
380 stack = NULL;
381 }
382 }
383 if (stack == NULL) {
e40cfbd7 384 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 385 flags |= TDF_ALLOCATED_STACK;
99df837e 386 }
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MD
387 if (cpu < 0) {
388 cpu = ++cpu_rotator;
389 cpu_ccfence();
390 cpu %= ncpus;
391 }
392 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 393 return(td);
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MD
394}
395
396/*
397 * Initialize a preexisting thread structure. This function is used by
398 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
399 *
f8c3996b
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400 * All threads start out in a critical section at a priority of
401 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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402 * appropriate. This function may send an IPI message when the
403 * requested cpu is not the current cpu and consequently gd_tdallq may
404 * not be initialized synchronously from the point of view of the originating
405 * cpu.
406 *
407 * NOTE! we have to be careful in regards to creating threads for other cpus
408 * if SMP has not yet been activated.
7d0bac62 409 */
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410static void
411lwkt_init_thread_remote(void *arg)
412{
413 thread_t td = arg;
414
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415 /*
416 * Protected by critical section held by IPI dispatch
417 */
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418 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
419}
420
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421/*
422 * lwkt core thread structural initialization.
423 *
424 * NOTE: All threads are initialized as mpsafe threads.
425 */
7d0bac62 426void
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427lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
428 struct globaldata *gd)
7d0bac62 429{
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430 globaldata_t mygd = mycpu;
431
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432 bzero(td, sizeof(struct thread));
433 td->td_kstack = stack;
f470d0c8 434 td->td_kstack_size = stksize;
d3d32139 435 td->td_flags = flags;
4643740a 436 td->td_mpflags = 0;
f256b6c0 437 td->td_type = TD_TYPE_GENERIC;
26a0694b 438 td->td_gd = gd;
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439 td->td_pri = TDPRI_KERN_DAEMON;
440 td->td_critcount = 1;
54341a3b 441 td->td_toks_have = NULL;
3b998fa9 442 td->td_toks_stop = &td->td_toks_base;
392cd266 443 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT))
d636cd48 444 lwkt_initport_spin(&td->td_msgport, td);
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445 else
446 lwkt_initport_thread(&td->td_msgport, td);
99df837e 447 pmap_init_thread(td);
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448 /*
449 * Normally initializing a thread for a remote cpu requires sending an
450 * IPI. However, the idlethread is setup before the other cpus are
451 * activated so we have to treat it as a special case. XXX manipulation
452 * of gd_tdallq requires the BGL.
453 */
454 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 455 crit_enter_gd(mygd);
75cdbe6c 456 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 457 crit_exit_gd(mygd);
75cdbe6c 458 } else {
2db3b277 459 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 460 }
8c72e3d5 461 dsched_new_thread(td);
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MD
462}
463
464void
465lwkt_set_comm(thread_t td, const char *ctl, ...)
466{
e2565a42 467 __va_list va;
73e4f7b9 468
e2565a42 469 __va_start(va, ctl);
379210cb 470 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 471 __va_end(va);
5bf48697 472 KTR_LOG(ctxsw_newtd, td, td->td_comm);
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473}
474
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475/*
476 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
477 * this does not prevent the thread from migrating to another cpu so the
478 * gd_tdallq state is not protected by this.
479 */
99df837e 480void
73e4f7b9 481lwkt_hold(thread_t td)
99df837e 482{
74c9628e 483 atomic_add_int(&td->td_refs, 1);
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MD
484}
485
486void
487lwkt_rele(thread_t td)
488{
489 KKASSERT(td->td_refs > 0);
74c9628e 490 atomic_add_int(&td->td_refs, -1);
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491}
492
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493void
494lwkt_free_thread(thread_t td)
495{
74c9628e 496 KKASSERT(td->td_refs == 0);
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497 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
498 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
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499 if (td->td_flags & TDF_ALLOCATED_THREAD) {
500 objcache_put(thread_cache, td);
501 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
502 /* client-allocated struct with internally allocated stack */
503 KASSERT(td->td_kstack && td->td_kstack_size > 0,
504 ("lwkt_free_thread: corrupted stack"));
505 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
506 td->td_kstack = NULL;
507 td->td_kstack_size = 0;
99df837e 508 }
e7c0dbba 509 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
510}
511
512
8ad65e08
MD
513/*
514 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
515 * switch to the idlethread. Switching must occur within a critical
516 * section to avoid races with the scheduling queue.
517 *
518 * We always have full control over our cpu's run queue. Other cpus
519 * that wish to manipulate our queue must use the cpu_*msg() calls to
520 * talk to our cpu, so a critical section is all that is needed and
521 * the result is very, very fast thread switching.
522 *
96728c05
MD
523 * The LWKT scheduler uses a fixed priority model and round-robins at
524 * each priority level. User process scheduling is a totally
525 * different beast and LWKT priorities should not be confused with
526 * user process priorities.
f1d1c3fa 527 *
69d78e99
MD
528 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
529 * is not called by the current thread in the preemption case, only when
530 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
531 *
532 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
533 * migration and tsleep deschedule the current lwkt thread and call
534 * lwkt_switch(). In particular, the target cpu of the migration fully
535 * expects the thread to become non-runnable and can deadlock against
536 * cpusync operations if we run any IPIs prior to switching the thread out.
537 *
538 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 539 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
540 */
541void
542lwkt_switch(void)
543{
37af14fe
MD
544 globaldata_t gd = mycpu;
545 thread_t td = gd->gd_curthread;
8ad65e08 546 thread_t ntd;
b12defdc 547 int spinning = 0;
8ad65e08 548
da0b0e8b 549 KKASSERT(gd->gd_processing_ipiq == 0);
121f93bc 550 KKASSERT(td->td_flags & TDF_RUNNING);
da0b0e8b 551
46a3f46d 552 /*
27e88a6e
MD
553 * Switching from within a 'fast' (non thread switched) interrupt or IPI
554 * is illegal. However, we may have to do it anyway if we hit a fatal
555 * kernel trap or we have paniced.
556 *
557 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 558 */
27e88a6e
MD
559 if (gd->gd_intr_nesting_level) {
560 int savegdnest;
561 int savegdtrap;
562
5fddbda2 563 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22 564 panic("lwkt_switch: Attempt to switch from a "
5a8df152 565 "fast interrupt, ipi, or hard code section, "
4a28fe22
MD
566 "td %p\n",
567 td);
27e88a6e
MD
568 } else {
569 savegdnest = gd->gd_intr_nesting_level;
570 savegdtrap = gd->gd_trap_nesting_level;
571 gd->gd_intr_nesting_level = 0;
572 gd->gd_trap_nesting_level = 0;
a7422615
MD
573 if ((td->td_flags & TDF_PANICWARN) == 0) {
574 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
575 kprintf("Warning: thread switch from interrupt, IPI, "
576 "or hard code section.\n"
a7422615 577 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 578 print_backtrace(-1);
a7422615 579 }
27e88a6e
MD
580 lwkt_switch();
581 gd->gd_intr_nesting_level = savegdnest;
582 gd->gd_trap_nesting_level = savegdtrap;
583 return;
584 }
96728c05 585 }
ef0fdad1 586
cb973d15 587 /*
85946b6c
MD
588 * Release our current user process designation if we are blocking
589 * or if a user reschedule was requested.
590 *
591 * NOTE: This function is NOT called if we are switching into or
592 * returning from a preemption.
593 *
594 * NOTE: Releasing our current user process designation may cause
595 * it to be assigned to another thread, which in turn will
596 * cause us to block in the usched acquire code when we attempt
597 * to return to userland.
598 *
599 * NOTE: On SMP systems this can be very nasty when heavy token
600 * contention is present so we want to be careful not to
601 * release the designation gratuitously.
cb973d15 602 */
85946b6c
MD
603 if (td->td_release &&
604 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 605 td->td_release(td);
85946b6c 606 }
cb973d15 607
85946b6c
MD
608 /*
609 * Release all tokens
610 */
37af14fe 611 crit_enter_gd(gd);
3b998fa9 612 if (TD_TOKS_HELD(td))
9d265729
MD
613 lwkt_relalltokens(td);
614
615 /*
b02926de
MD
616 * We had better not be holding any spin locks, but don't get into an
617 * endless panic loop.
9d265729 618 */
0846e4ce 619 KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL,
d666840a 620 ("lwkt_switch: still holding %d exclusive spinlocks!",
0846e4ce 621 gd->gd_spinlocks));
9d265729 622
8a8d5d85 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;
8ec60c3f
MD
646
647 /*
b9eb1c19
MD
648 * The interrupt may have woken a thread up, we need to properly
649 * set the reschedule flag if the originally interrupted thread is
650 * at a lower priority.
85946b6c
MD
651 *
652 * The interrupt may not have descheduled.
8ec60c3f 653 */
85946b6c 654 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 655 need_lwkt_resched();
f9235b6d
MD
656 goto havethread_preempted;
657 }
658
b12defdc 659 /*
f9235b6d 660 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
661 * schedule the target thread.
662 *
663 * Reminder: Again, we cannot afford to run any IPIs in this path if
664 * the current thread has been descheduled.
f9235b6d
MD
665 */
666 for (;;) {
b12defdc 667 clear_lwkt_resched();
f9235b6d 668
4b5f931b 669 /*
2a418930 670 * Hotpath - pull the head of the run queue and attempt to schedule
85946b6c 671 * it.
41a01a4d 672 */
7c3dd309
NA
673 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
674
675 if (ntd == NULL) {
676 /*
677 * Runq is empty, switch to idle to allow it to halt.
678 */
679 ntd = &gd->gd_idlethread;
7c3dd309
NA
680 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
681 ASSERT_NO_TOKENS_HELD(ntd);
7c3dd309
NA
682 cpu_time.cp_msg[0] = 0;
683 cpu_time.cp_stallpc = 0;
684 goto haveidle;
f9235b6d 685 }
41a01a4d 686
8ec60c3f 687 /*
b12defdc 688 * Hotpath - schedule ntd.
6f207a2c
MD
689 *
690 * NOTE: For UP there is no mplock and lwkt_getalltokens()
691 * always succeeds.
8ec60c3f 692 */
b12defdc
MD
693 if (TD_TOKS_NOT_HELD(ntd) ||
694 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops)))
695 {
f9235b6d 696 goto havethread;
b12defdc 697 }
f9235b6d 698
f9235b6d 699 /*
2a418930
MD
700 * Coldpath (SMP only since tokens always succeed on UP)
701 *
702 * We had some contention on the thread we wanted to schedule.
703 * What we do now is try to find a thread that we can schedule
b12defdc 704 * in its stead.
2a418930 705 *
85946b6c
MD
706 * The coldpath scan does NOT rearrange threads in the run list.
707 * The lwkt_schedulerclock() will assert need_lwkt_resched() on
708 * the next tick whenever the current head is not the current thread.
f9235b6d 709 */
b12defdc 710#ifdef INVARIANTS
85946b6c 711 ++ntd->td_contended;
b12defdc 712#endif
574339e6 713 ++gd->gd_cnt.v_token_colls;
b12defdc 714
85946b6c 715 if (fairq_bypass > 0)
b12defdc
MD
716 goto skip;
717
b12defdc 718 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
e3e6be1f 719#ifndef NO_LWKT_SPLIT_USERPRI
85946b6c
MD
720 /*
721 * Never schedule threads returning to userland or the
722 * user thread scheduler helper thread when higher priority
bb6860b5
NA
723 * threads are present. The runq is sorted by priority
724 * so we can give up traversing it when we find the first
725 * low priority thread.
85946b6c
MD
726 */
727 if (ntd->td_pri < TDPRI_KERN_LPSCHED) {
728 ntd = NULL;
729 break;
730 }
d992c377 731#endif
85946b6c
MD
732
733 /*
734 * Try this one.
735 */
b12defdc
MD
736 if (TD_TOKS_NOT_HELD(ntd) ||
737 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) {
738 goto havethread;
739 }
85946b6c 740#ifdef INVARIANTS
85946b6c 741 ++ntd->td_contended;
b12defdc 742#endif
574339e6 743 ++gd->gd_cnt.v_token_colls;
2a418930
MD
744 }
745
b12defdc 746skip:
2a418930
MD
747 /*
748 * We exhausted the run list, meaning that all runnable threads
b12defdc 749 * are contested.
2a418930
MD
750 */
751 cpu_pause();
752 ntd = &gd->gd_idlethread;
2a418930
MD
753 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
754 ASSERT_NO_TOKENS_HELD(ntd);
755 /* contention case, do not clear contention mask */
2a418930
MD
756
757 /*
b12defdc
MD
758 * We are going to have to retry but if the current thread is not
759 * on the runq we instead switch through the idle thread to get away
760 * from the current thread. We have to flag for lwkt reschedule
761 * to prevent the idle thread from halting.
2a418930 762 *
b12defdc
MD
763 * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to
764 * instruct it to deal with the potential for deadlocks by
765 * ordering the tokens by address.
2a418930 766 */
b12defdc 767 if ((td->td_flags & TDF_RUNQ) == 0) {
85946b6c 768 need_lwkt_resched(); /* prevent hlt */
2a418930 769 goto haveidle;
4b5f931b 770 }
dbefba87 771#if defined(INVARIANTS) && defined(__x86_64__)
d5b2d319
MD
772 if ((read_rflags() & PSL_I) == 0) {
773 cpu_enable_intr();
774 panic("lwkt_switch() called with interrupts disabled");
775 }
776#endif
b12defdc
MD
777
778 /*
779 * Number iterations so far. After a certain point we switch to
780 * a sorted-address/monitor/mwait version of lwkt_getalltokens()
781 */
782 if (spinning < 0x7FFFFFFF)
783 ++spinning;
784
b12defdc
MD
785 /*
786 * lwkt_getalltokens() failed in sorted token mode, we can use
787 * monitor/mwait in this case.
788 */
789 if (spinning >= lwkt_spin_loops &&
790 (cpu_mi_feature & CPU_MI_MONITOR) &&
791 lwkt_spin_monitor)
792 {
793 cpu_mmw_pause_int(&gd->gd_reqflags,
794 (gd->gd_reqflags | RQF_SPINNING) &
a46b4a23
MD
795 ~RQF_IDLECHECK_WK_MASK,
796 cpu_mwait_spin);
b12defdc 797 }
b12defdc
MD
798
799 /*
800 * We already checked that td is still scheduled so this should be
801 * safe.
802 */
803 splz_check();
804
805 /*
806 * This experimental resequencer is used as a fall-back to reduce
807 * hw cache line contention by placing each core's scheduler into a
808 * time-domain-multplexed slot.
809 *
810 * The resequencer is disabled by default. It's functionality has
811 * largely been superceeded by the token algorithm which limits races
812 * to a subset of cores.
813 *
814 * The resequencer algorithm tends to break down when more than
815 * 20 cores are contending. What appears to happen is that new
816 * tokens can be obtained out of address-sorted order by new cores
817 * while existing cores languish in long delays between retries and
818 * wind up being starved-out of the token acquisition.
819 */
820 if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) {
821 int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
822 int oseq;
823
824 while ((oseq = lwkt_cseq_rindex) != cseq) {
825 cpu_ccfence();
826#if 1
827 if (cpu_mi_feature & CPU_MI_MONITOR) {
a46b4a23 828 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq, cpu_mwait_spin);
b12defdc
MD
829 } else {
830#endif
831 cpu_pause();
832 cpu_lfence();
833#if 1
834 }
8b402283 835#endif
0f0466c0 836 }
b12defdc
MD
837 DELAY(1);
838 atomic_add_int(&lwkt_cseq_rindex, 1);
2a418930 839 }
2a418930 840 /* highest level for(;;) loop */
f1d1c3fa 841 }
8a8d5d85 842
2a418930 843havethread:
b12defdc 844 /*
be71787b
MD
845 * Clear gd_idle_repeat when doing a normal switch to a non-idle
846 * thread.
f9235b6d 847 */
9ac1ee6e 848 ntd->td_wmesg = NULL;
b12defdc 849 ++gd->gd_cnt.v_swtch;
be71787b 850 gd->gd_idle_repeat = 0;
2a418930 851
f9235b6d 852havethread_preempted:
f9235b6d
MD
853 /*
854 * If the new target does not need the MP lock and we are holding it,
855 * release the MP lock. If the new target requires the MP lock we have
856 * already acquired it for the target.
8a8d5d85 857 */
2a418930 858 ;
f9235b6d
MD
859haveidle:
860 KASSERT(ntd->td_critcount,
b5d16701
MD
861 ("priority problem in lwkt_switch %d %d",
862 td->td_critcount, ntd->td_critcount));
863
94f6d86e 864 if (td != ntd) {
cc9b6223
MD
865 /*
866 * Execute the actual thread switch operation. This function
867 * returns to the current thread and returns the previous thread
868 * (which may be different from the thread we switched to).
869 *
870 * We are responsible for marking ntd as TDF_RUNNING.
871 */
121f93bc 872 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
94f6d86e 873 ++switch_count;
a1f0fb66 874 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
875 ntd->td_flags |= TDF_RUNNING;
876 lwkt_switch_return(td->td_switch(ntd));
877 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 878 }
b12defdc 879
b12defdc 880 /*
54341a3b 881 * catch-all. XXX is this strictly needed?
b12defdc
MD
882 */
883 splz_check();
54341a3b 884
37af14fe
MD
885 /* NOTE: current cpu may have changed after switch */
886 crit_exit_quick(td);
8ad65e08
MD
887}
888
cc9b6223
MD
889/*
890 * Called by assembly in the td_switch (thread restore path) for thread
891 * bootstrap cases which do not 'return' to lwkt_switch().
892 */
893void
894lwkt_switch_return(thread_t otd)
895{
cc9b6223
MD
896 globaldata_t rgd;
897
898 /*
899 * Check if otd was migrating. Now that we are on ntd we can finish
900 * up the migration. This is a bit messy but it is the only place
901 * where td is known to be fully descheduled.
902 *
903 * We can only activate the migration if otd was migrating but not
904 * held on the cpu due to a preemption chain. We still have to
905 * clear TDF_RUNNING on the old thread either way.
906 *
907 * We are responsible for clearing the previously running thread's
908 * TDF_RUNNING.
909 */
910 if ((rgd = otd->td_migrate_gd) != NULL &&
911 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
912 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
913 (TDF_MIGRATING | TDF_RUNNING));
914 otd->td_migrate_gd = NULL;
915 otd->td_flags &= ~TDF_RUNNING;
916 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
917 } else {
918 otd->td_flags &= ~TDF_RUNNING;
919 }
2b07d9aa
MD
920
921 /*
922 * Final exit validations (see lwp_wait()). Note that otd becomes
923 * invalid the *instant* we set TDF_MP_EXITSIG.
924 */
925 while (otd->td_flags & TDF_EXITING) {
926 u_int mpflags;
927
928 mpflags = otd->td_mpflags;
929 cpu_ccfence();
930
931 if (mpflags & TDF_MP_EXITWAIT) {
932 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
933 mpflags | TDF_MP_EXITSIG)) {
934 wakeup(otd);
935 break;
936 }
937 } else {
938 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
939 mpflags | TDF_MP_EXITSIG)) {
940 wakeup(otd);
941 break;
942 }
943 }
944 }
cc9b6223
MD
945}
946
b68b7282 947/*
96728c05 948 * Request that the target thread preempt the current thread. Preemption
54341a3b
MD
949 * can only occur if our only critical section is the one that we were called
950 * with, the relative priority of the target thread is higher, and the target
951 * thread holds no tokens. This also only works if we are not holding any
952 * spinlocks (obviously).
96728c05
MD
953 *
954 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
955 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 956 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
957 * to determine whether preemption is possible (aka usually just the crit
958 * priority of lwkt_schedule() itself).
b68b7282 959 *
54341a3b
MD
960 * Preemption is typically limited to interrupt threads.
961 *
962 * Operation works in a fairly straight-forward manner. The normal
963 * scheduling code is bypassed and we switch directly to the target
964 * thread. When the target thread attempts to block or switch away
965 * code at the base of lwkt_switch() will switch directly back to our
966 * thread. Our thread is able to retain whatever tokens it holds and
967 * if the target needs one of them the target will switch back to us
968 * and reschedule itself normally.
b68b7282
MD
969 */
970void
f9235b6d 971lwkt_preempt(thread_t ntd, int critcount)
b68b7282 972{
46a3f46d 973 struct globaldata *gd = mycpu;
cc9b6223 974 thread_t xtd;
0a3f9b47 975 thread_t td;
2d910aaf 976 int save_gd_intr_nesting_level;
b68b7282 977
26a0694b 978 /*
96728c05
MD
979 * The caller has put us in a critical section. We can only preempt
980 * if the caller of the caller was not in a critical section (basically
f9235b6d 981 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 982 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 983 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
984 *
985 * YYY The target thread must be in a critical section (else it must
986 * inherit our critical section? I dunno yet).
26a0694b 987 */
f9235b6d 988 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 989
b12defdc 990 td = gd->gd_curthread;
fbc024e4
MD
991 if (preempt_enable == 0) {
992 ++preempt_miss;
993 return;
994 }
f9235b6d 995 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
996 ++preempt_miss;
997 return;
998 }
f9235b6d 999 if (td->td_critcount > critcount) {
96728c05
MD
1000 ++preempt_miss;
1001 return;
1002 }
121f93bc
MD
1003 if (td->td_cscount) {
1004 ++preempt_miss;
1005 return;
1006 }
46a3f46d 1007 if (ntd->td_gd != gd) {
96728c05
MD
1008 ++preempt_miss;
1009 return;
1010 }
41a01a4d 1011 /*
77912481
MD
1012 * We don't have to check spinlocks here as they will also bump
1013 * td_critcount.
d3d1cbc8
MD
1014 *
1015 * Do not try to preempt if the target thread is holding any tokens.
1016 * We could try to acquire the tokens but this case is so rare there
1017 * is no need to support it.
41a01a4d 1018 */
0846e4ce 1019 KKASSERT(gd->gd_spinlocks == 0);
77912481 1020
3b998fa9 1021 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 1022 ++preempt_miss;
d3d1cbc8
MD
1023 return;
1024 }
26a0694b
MD
1025 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1026 ++preempt_weird;
1027 return;
1028 }
1029 if (ntd->td_preempted) {
4b5f931b 1030 ++preempt_hit;
26a0694b 1031 return;
b68b7282 1032 }
da0b0e8b 1033 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1034
8ec60c3f
MD
1035 /*
1036 * Since we are able to preempt the current thread, there is no need to
1037 * call need_lwkt_resched().
2d910aaf
MD
1038 *
1039 * We must temporarily clear gd_intr_nesting_level around the switch
1040 * since switchouts from the target thread are allowed (they will just
1041 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1042 *
1043 * A preemption must switch back to the original thread, assert the
1044 * case.
8ec60c3f 1045 */
26a0694b
MD
1046 ++preempt_hit;
1047 ntd->td_preempted = td;
1048 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1049 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1050 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1051 gd->gd_intr_nesting_level = 0;
121f93bc
MD
1052
1053 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
cc9b6223
MD
1054 ntd->td_flags |= TDF_RUNNING;
1055 xtd = td->td_switch(ntd);
1056 KKASSERT(xtd == ntd);
1057 lwkt_switch_return(xtd);
2d910aaf 1058 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1059
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MD
1060 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1061 ntd->td_preempted = NULL;
1062 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1063}
1064
f1d1c3fa 1065/*
faaeffac 1066 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1067 * This will work inside a critical section but not inside a hard code
1068 * section.
ef0fdad1 1069 *
f1d1c3fa
MD
1070 * (self contained on a per cpu basis)
1071 */
1072void
faaeffac 1073splz_check(void)
f1d1c3fa 1074{
7966cb69
MD
1075 globaldata_t gd = mycpu;
1076 thread_t td = gd->gd_curthread;
ef0fdad1 1077
4a28fe22
MD
1078 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1079 gd->gd_intr_nesting_level == 0 &&
1080 td->td_nest_count < 2)
1081 {
f1d1c3fa 1082 splz();
4a28fe22
MD
1083 }
1084}
1085
1086/*
1087 * This version is integrated into crit_exit, reqflags has already
1088 * been tested but td_critcount has not.
1089 *
1090 * We only want to execute the splz() on the 1->0 transition of
1091 * critcount and not in a hard code section or if too deeply nested.
925040f2 1092 *
0846e4ce 1093 * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0.
4a28fe22
MD
1094 */
1095void
1096lwkt_maybe_splz(thread_t td)
1097{
1098 globaldata_t gd = td->td_gd;
1099
1100 if (td->td_critcount == 0 &&
1101 gd->gd_intr_nesting_level == 0 &&
1102 td->td_nest_count < 2)
1103 {
1104 splz();
1105 }
f1d1c3fa
MD
1106}
1107
e6546af9
MD
1108/*
1109 * Drivers which set up processing co-threads can call this function to
1110 * run the co-thread at a higher priority and to allow it to preempt
1111 * normal threads.
1112 */
1113void
1114lwkt_set_interrupt_support_thread(void)
1115{
1116 thread_t td = curthread;
1117
1118 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1119 td->td_flags |= TDF_INTTHREAD;
1120 td->td_preemptable = lwkt_preempt;
1121}
1122
1123
8ad65e08 1124/*
f9235b6d
MD
1125 * This function is used to negotiate a passive release of the current
1126 * process/lwp designation with the user scheduler, allowing the user
1127 * scheduler to schedule another user thread. The related kernel thread
1128 * (curthread) continues running in the released state.
8ad65e08
MD
1129 */
1130void
f9235b6d 1131lwkt_passive_release(struct thread *td)
8ad65e08 1132{
f9235b6d
MD
1133 struct lwp *lp = td->td_lwp;
1134
e3e6be1f 1135#ifndef NO_LWKT_SPLIT_USERPRI
f9235b6d
MD
1136 td->td_release = NULL;
1137 lwkt_setpri_self(TDPRI_KERN_USER);
d992c377
MD
1138#endif
1139
f9235b6d 1140 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1141}
1142
f9235b6d 1143
3824f392 1144/*
d2d8515b
MD
1145 * This implements a LWKT yield, allowing a kernel thread to yield to other
1146 * kernel threads at the same or higher priority. This function can be
1147 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1148 *
d2d8515b
MD
1149 * Most kernel threads run at the same priority in order to allow equal
1150 * sharing.
f9235b6d
MD
1151 *
1152 * (self contained on a per cpu basis)
3824f392
MD
1153 */
1154void
f9235b6d 1155lwkt_yield(void)
3824f392 1156{
f9235b6d
MD
1157 globaldata_t gd = mycpu;
1158 thread_t td = gd->gd_curthread;
3824f392 1159
f9235b6d
MD
1160 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1161 splz();
85946b6c 1162 if (lwkt_resched_wanted()) {
f9235b6d
MD
1163 lwkt_schedule_self(curthread);
1164 lwkt_switch();
f9235b6d 1165 }
3824f392
MD
1166}
1167
40504122
MD
1168/*
1169 * The quick version processes pending interrupts and higher-priority
1170 * LWKT threads but will not round-robin same-priority LWKT threads.
de4d4cb0
MD
1171 *
1172 * When called while attempting to return to userland the only same-pri
1173 * threads are the ones which have already tried to become the current
1174 * user process.
40504122
MD
1175 */
1176void
1177lwkt_yield_quick(void)
1178{
1179 globaldata_t gd = mycpu;
1180 thread_t td = gd->gd_curthread;
1181
1182 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1183 splz();
1184 if (lwkt_resched_wanted()) {
9c99cb33 1185 crit_enter();
40504122
MD
1186 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1187 clear_lwkt_resched();
1188 } else {
1189 lwkt_schedule_self(curthread);
1190 lwkt_switch();
1191 }
9c99cb33 1192 crit_exit();
40504122
MD
1193 }
1194}
1195
3824f392 1196/*
f9235b6d
MD
1197 * This yield is designed for kernel threads with a user context.
1198 *
1199 * The kernel acting on behalf of the user is potentially cpu-bound,
1200 * this function will efficiently allow other threads to run and also
1201 * switch to other processes by releasing.
3824f392
MD
1202 *
1203 * The lwkt_user_yield() function is designed to have very low overhead
1204 * if no yield is determined to be needed.
1205 */
1206void
1207lwkt_user_yield(void)
1208{
f9235b6d
MD
1209 globaldata_t gd = mycpu;
1210 thread_t td = gd->gd_curthread;
1211
1212 /*
1213 * Always run any pending interrupts in case we are in a critical
1214 * section.
1215 */
1216 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1217 splz();
3824f392 1218
3824f392 1219 /*
f9235b6d
MD
1220 * Switch (which forces a release) if another kernel thread needs
1221 * the cpu, if userland wants us to resched, or if our kernel
1222 * quantum has run out.
3824f392 1223 */
f9235b6d 1224 if (lwkt_resched_wanted() ||
85946b6c 1225 user_resched_wanted())
f9235b6d 1226 {
3824f392 1227 lwkt_switch();
3824f392
MD
1228 }
1229
f9235b6d 1230#if 0
3824f392 1231 /*
f9235b6d
MD
1232 * Reacquire the current process if we are released.
1233 *
1234 * XXX not implemented atm. The kernel may be holding locks and such,
1235 * so we want the thread to continue to receive cpu.
3824f392 1236 */
f9235b6d
MD
1237 if (td->td_release == NULL && lp) {
1238 lp->lwp_proc->p_usched->acquire_curproc(lp);
1239 td->td_release = lwkt_passive_release;
1240 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1241 }
f9235b6d 1242#endif
b9eb1c19
MD
1243}
1244
8ad65e08 1245/*
f1d1c3fa
MD
1246 * Generic schedule. Possibly schedule threads belonging to other cpus and
1247 * deal with threads that might be blocked on a wait queue.
1248 *
0a3f9b47
MD
1249 * We have a little helper inline function which does additional work after
1250 * the thread has been enqueued, including dealing with preemption and
1251 * setting need_lwkt_resched() (which prevents the kernel from returning
1252 * to userland until it has processed higher priority threads).
6330a558
MD
1253 *
1254 * It is possible for this routine to be called after a failed _enqueue
1255 * (due to the target thread migrating, sleeping, or otherwise blocked).
1256 * We have to check that the thread is actually on the run queue!
8ad65e08 1257 */
0a3f9b47
MD
1258static __inline
1259void
85946b6c 1260_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1261{
6330a558 1262 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1263 if (ntd->td_preemptable) {
f9235b6d 1264 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1265 }
0a3f9b47
MD
1266 }
1267}
1268
361d01dd 1269static __inline
8ad65e08 1270void
85946b6c 1271_lwkt_schedule(thread_t td)
8ad65e08 1272{
37af14fe
MD
1273 globaldata_t mygd = mycpu;
1274
cf709dd2
MD
1275 KASSERT(td != &td->td_gd->gd_idlethread,
1276 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1277 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1278 crit_enter_gd(mygd);
4643740a
MD
1279 KKASSERT(td->td_lwp == NULL ||
1280 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1281
37af14fe 1282 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1283 _lwkt_enqueue(td);
1284 } else {
f1d1c3fa 1285 /*
7cd8d145
MD
1286 * If we own the thread, there is no race (since we are in a
1287 * critical section). If we do not own the thread there might
1288 * be a race but the target cpu will deal with it.
f1d1c3fa 1289 */
7cd8d145 1290 if (td->td_gd == mygd) {
9d265729 1291 _lwkt_enqueue(td);
85946b6c 1292 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1293 } else {
e381e77c 1294 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1295 }
8ad65e08 1296 }
37af14fe 1297 crit_exit_gd(mygd);
8ad65e08
MD
1298}
1299
361d01dd
MD
1300void
1301lwkt_schedule(thread_t td)
1302{
85946b6c 1303 _lwkt_schedule(td);
361d01dd
MD
1304}
1305
1306void
85946b6c 1307lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1308{
85946b6c 1309 _lwkt_schedule(td);
361d01dd
MD
1310}
1311
e381e77c
MD
1312/*
1313 * When scheduled remotely if frame != NULL the IPIQ is being
1314 * run via doreti or an interrupt then preemption can be allowed.
1315 *
1316 * To allow preemption we have to drop the critical section so only
1317 * one is present in _lwkt_schedule_post.
1318 */
1319static void
1320lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1321{
1322 thread_t td = curthread;
1323 thread_t ntd = arg;
1324
1325 if (frame && ntd->td_preemptable) {
1326 crit_exit_noyield(td);
85946b6c 1327 _lwkt_schedule(ntd);
e381e77c
MD
1328 crit_enter_quick(td);
1329 } else {
85946b6c 1330 _lwkt_schedule(ntd);
e381e77c
MD
1331 }
1332}
1333
d9eea1a5 1334/*
52eedfb5
MD
1335 * Thread migration using a 'Pull' method. The thread may or may not be
1336 * the current thread. It MUST be descheduled and in a stable state.
1337 * lwkt_giveaway() must be called on the cpu owning the thread.
1338 *
1339 * At any point after lwkt_giveaway() is called, the target cpu may
1340 * 'pull' the thread by calling lwkt_acquire().
1341 *
ae8e83e6
MD
1342 * We have to make sure the thread is not sitting on a per-cpu tsleep
1343 * queue or it will blow up when it moves to another cpu.
1344 *
52eedfb5 1345 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1346 */
52eedfb5
MD
1347void
1348lwkt_giveaway(thread_t td)
1349{
3b4192fb 1350 globaldata_t gd = mycpu;
52eedfb5 1351
3b4192fb
MD
1352 crit_enter_gd(gd);
1353 if (td->td_flags & TDF_TSLEEPQ)
1354 tsleep_remove(td);
1355 KKASSERT(td->td_gd == gd);
1356 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1357 td->td_flags |= TDF_MIGRATING;
1358 crit_exit_gd(gd);
52eedfb5
MD
1359}
1360
a2a5ad0d
MD
1361void
1362lwkt_acquire(thread_t td)
1363{
37af14fe
MD
1364 globaldata_t gd;
1365 globaldata_t mygd;
cc9b6223 1366 int retry = 10000000;
a2a5ad0d 1367
52eedfb5 1368 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1369 gd = td->td_gd;
37af14fe 1370 mygd = mycpu;
52eedfb5 1371 if (gd != mycpu) {
35238fa5 1372 cpu_lfence();
52eedfb5 1373 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1374 crit_enter_gd(mygd);
cfaeae2a 1375 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23 1376 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
df910c23 1377 lwkt_process_ipiq();
52eedfb5 1378 cpu_lfence();
cc9b6223
MD
1379 if (--retry == 0) {
1380 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1381 td, td->td_flags);
1382 retry = 10000000;
1383 }
df910c23 1384 }
cfaeae2a 1385 DEBUG_POP_INFO();
562273ea 1386 cpu_mfence();
37af14fe 1387 td->td_gd = mygd;
52eedfb5
MD
1388 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1389 td->td_flags &= ~TDF_MIGRATING;
1390 crit_exit_gd(mygd);
1391 } else {
1392 crit_enter_gd(mygd);
1393 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1394 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1395 crit_exit_gd(mygd);
a2a5ad0d
MD
1396 }
1397}
1398
f1d1c3fa
MD
1399/*
1400 * Generic deschedule. Descheduling threads other then your own should be
1401 * done only in carefully controlled circumstances. Descheduling is
1402 * asynchronous.
1403 *
1404 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1405 */
1406void
1407lwkt_deschedule(thread_t td)
1408{
f1d1c3fa
MD
1409 crit_enter();
1410 if (td == curthread) {
1411 _lwkt_dequeue(td);
1412 } else {
a72187e9 1413 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1414 _lwkt_dequeue(td);
1415 } else {
b8a98473 1416 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1417 }
1418 }
1419 crit_exit();
1420}
1421
4b5f931b
MD
1422/*
1423 * Set the target thread's priority. This routine does not automatically
1424 * switch to a higher priority thread, LWKT threads are not designed for
1425 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1426 */
1427void
1428lwkt_setpri(thread_t td, int pri)
1429{
f9235b6d
MD
1430 if (td->td_pri != pri) {
1431 KKASSERT(pri >= 0);
1432 crit_enter();
1433 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1434 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1435 _lwkt_dequeue(td);
1436 td->td_pri = pri;
1437 _lwkt_enqueue(td);
1438 } else {
1439 td->td_pri = pri;
1440 }
1441 crit_exit();
26a0694b 1442 }
26a0694b
MD
1443}
1444
03bd0a5e
MD
1445/*
1446 * Set the initial priority for a thread prior to it being scheduled for
1447 * the first time. The thread MUST NOT be scheduled before or during
1448 * this call. The thread may be assigned to a cpu other then the current
1449 * cpu.
1450 *
1451 * Typically used after a thread has been created with TDF_STOPPREQ,
1452 * and before the thread is initially scheduled.
1453 */
1454void
1455lwkt_setpri_initial(thread_t td, int pri)
1456{
1457 KKASSERT(pri >= 0);
1458 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1459 td->td_pri = pri;
03bd0a5e
MD
1460}
1461
26a0694b
MD
1462void
1463lwkt_setpri_self(int pri)
1464{
1465 thread_t td = curthread;
1466
4b5f931b
MD
1467 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1468 crit_enter();
1469 if (td->td_flags & TDF_RUNQ) {
1470 _lwkt_dequeue(td);
f9235b6d 1471 td->td_pri = pri;
4b5f931b
MD
1472 _lwkt_enqueue(td);
1473 } else {
f9235b6d 1474 td->td_pri = pri;
4b5f931b
MD
1475 }
1476 crit_exit();
1477}
1478
f9235b6d 1479/*
85946b6c 1480 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1481 */
1482void
85946b6c 1483lwkt_schedulerclock(thread_t td)
f9235b6d 1484{
85946b6c
MD
1485 globaldata_t gd = td->td_gd;
1486 thread_t xtd;
2a418930 1487
85946b6c
MD
1488 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1489 /*
1490 * If the current thread is at the head of the runq shift it to the
1491 * end of any equal-priority threads and request a LWKT reschedule
1492 * if it moved.
d992c377
MD
1493 *
1494 * Ignore upri in this situation. There will only be one user thread
1495 * in user mode, all others will be user threads running in kernel
1496 * mode and we have to make sure they get some cpu.
85946b6c
MD
1497 */
1498 xtd = TAILQ_NEXT(td, td_threadq);
1499 if (xtd && xtd->td_pri == td->td_pri) {
1500 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1501 while (xtd && xtd->td_pri == td->td_pri)
1502 xtd = TAILQ_NEXT(xtd, td_threadq);
1503 if (xtd)
1504 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1505 else
1506 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1507 need_lwkt_resched();
f9235b6d 1508 }
85946b6c
MD
1509 } else {
1510 /*
1511 * If we scheduled a thread other than the one at the head of the
1512 * queue always request a reschedule every tick.
1513 */
1514 need_lwkt_resched();
f9235b6d
MD
1515 }
1516}
1517
5d21b981 1518/*
52eedfb5
MD
1519 * Migrate the current thread to the specified cpu.
1520 *
cc9b6223
MD
1521 * This is accomplished by descheduling ourselves from the current cpu
1522 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1523 * 'old' thread wants to migrate after it has been completely switched out
1524 * and will complete the migration.
1525 *
1526 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1527 *
1528 * We must be sure to release our current process designation (if a user
1529 * process) before clearing out any tsleepq we are on because the release
1530 * code may re-add us.
ae8e83e6
MD
1531 *
1532 * We must be sure to remove ourselves from the current cpu's tsleepq
1533 * before potentially moving to another queue. The thread can be on
1534 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1535 */
5d21b981
MD
1536
1537void
1538lwkt_setcpu_self(globaldata_t rgd)
1539{
5d21b981
MD
1540 thread_t td = curthread;
1541
1542 if (td->td_gd != rgd) {
1543 crit_enter_quick(td);
cc9b6223 1544
95858b91
MD
1545 if (td->td_release)
1546 td->td_release(td);
ae8e83e6 1547 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1548 tsleep_remove(td);
cc9b6223
MD
1549
1550 /*
1551 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1552 * trying to deschedule ourselves and switch away, then deschedule
1553 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1554 * call lwkt_switch() to complete the operation.
1555 */
5d21b981
MD
1556 td->td_flags |= TDF_MIGRATING;
1557 lwkt_deschedule_self(td);
52eedfb5 1558 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1559 td->td_migrate_gd = rgd;
5d21b981 1560 lwkt_switch();
cc9b6223
MD
1561
1562 /*
1563 * We are now on the target cpu
1564 */
1565 KKASSERT(rgd == mycpu);
52eedfb5 1566 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1567 crit_exit_quick(td);
1568 }
5d21b981
MD
1569}
1570
ecdefdda
MD
1571void
1572lwkt_migratecpu(int cpuid)
1573{
ecdefdda
MD
1574 globaldata_t rgd;
1575
1576 rgd = globaldata_find(cpuid);
1577 lwkt_setcpu_self(rgd);
ecdefdda
MD
1578}
1579
5d21b981
MD
1580/*
1581 * Remote IPI for cpu migration (called while in a critical section so we
cc9b6223
MD
1582 * do not have to enter another one).
1583 *
1584 * The thread (td) has already been completely descheduled from the
1585 * originating cpu and we can simply assert the case. The thread is
1586 * assigned to the new cpu and enqueued.
5d21b981 1587 *
cc9b6223 1588 * The thread will re-add itself to tdallq when it resumes execution.
5d21b981
MD
1589 */
1590static void
1591lwkt_setcpu_remote(void *arg)
1592{
1593 thread_t td = arg;
1594 globaldata_t gd = mycpu;
1595
cc9b6223 1596 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1597 td->td_gd = gd;
562273ea 1598 cpu_mfence();
5d21b981 1599 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1600 KKASSERT(td->td_migrate_gd == NULL);
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1601 KKASSERT(td->td_lwp == NULL ||
1602 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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1603 _lwkt_enqueue(td);
1604}
1605
553ea3c8 1606struct lwp *
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1607lwkt_preempted_proc(void)
1608{
73e4f7b9 1609 thread_t td = curthread;
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1610 while (td->td_preempted)
1611 td = td->td_preempted;
553ea3c8 1612 return(td->td_lwp);
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1613}
1614
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1615/*
1616 * Create a kernel process/thread/whatever. It shares it's address space
1617 * with proc0 - ie: kernel only.
1618 *
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1619 * If the cpu is not specified one will be selected. In the future
1620 * specifying a cpu of -1 will enable kernel thread migration between
1621 * cpus.
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1622 */
1623int
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1624lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1625 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1626{
73e4f7b9 1627 thread_t td;
e2565a42 1628 __va_list ap;
99df837e 1629
d3d32139 1630 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1631 tdflags);
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1632 if (tdp)
1633 *tdp = td;
709799ea 1634 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1635
1636 /*
1637 * Set up arg0 for 'ps' etc
1638 */
e2565a42 1639 __va_start(ap, fmt);
379210cb 1640 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1641 __va_end(ap);
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1642
1643 /*
1644 * Schedule the thread to run
1645 */
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1646 if (td->td_flags & TDF_NOSTART)
1647 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1648 else
4643740a 1649 lwkt_schedule(td);
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1650 return 0;
1651}
1652
1653/*
1654 * Destroy an LWKT thread. Warning! This function is not called when
1655 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1656 * uses a different reaping mechanism.
1657 */
1658void
1659lwkt_exit(void)
1660{
1661 thread_t td = curthread;
c070746a 1662 thread_t std;
8826f33a 1663 globaldata_t gd;
99df837e 1664
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1665 /*
1666 * Do any cleanup that might block here
1667 */
99df837e 1668 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1669 kprintf("kthread %p %s has exited\n", td, td->td_comm);
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1670 biosched_done(td);
1671 dsched_exit_thread(td);
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1672
1673 /*
1674 * Get us into a critical section to interlock gd_freetd and loop
1675 * until we can get it freed.
1676 *
1677 * We have to cache the current td in gd_freetd because objcache_put()ing
1678 * it would rip it out from under us while our thread is still active.
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1679 *
1680 * We are the current thread so of course our own TDF_RUNNING bit will
1681 * be set, so unlike the lwp reap code we don't wait for it to clear.
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1682 */
1683 gd = mycpu;
37af14fe 1684 crit_enter_quick(td);
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1685 for (;;) {
1686 if (td->td_refs) {
1687 tsleep(td, 0, "tdreap", 1);
1688 continue;
1689 }
1690 if ((std = gd->gd_freetd) != NULL) {
1691 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1692 gd->gd_freetd = NULL;
1693 objcache_put(thread_cache, std);
1694 continue;
1695 }
1696 break;
c070746a 1697 }
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1698
1699 /*
1700 * Remove thread resources from kernel lists and deschedule us for
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1701 * the last time. We cannot block after this point or we may end
1702 * up with a stale td on the tsleepq.
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1703 *
1704 * None of this may block, the critical section is the only thing
1705 * protecting tdallq and the only thing preventing new lwkt_hold()
1706 * thread refs now.
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1707 */
1708 if (td->td_flags & TDF_TSLEEPQ)
1709 tsleep_remove(td);
37af14fe 1710 lwkt_deschedule_self(td);
e56e4dea 1711 lwkt_remove_tdallq(td);
74c9628e 1712 KKASSERT(td->td_refs == 0);
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1713
1714 /*
1715 * Final cleanup
1716 */
1717 KKASSERT(gd->gd_freetd == NULL);
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1718 if (td->td_flags & TDF_ALLOCATED_THREAD)
1719 gd->gd_freetd = td;
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1720 cpu_thread_exit();
1721}
1722
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1723void
1724lwkt_remove_tdallq(thread_t td)
1725{
1726 KKASSERT(td->td_gd == mycpu);
1727 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1728}
1729
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1730/*
1731 * Code reduction and branch prediction improvements. Call/return
1732 * overhead on modern cpus often degenerates into 0 cycles due to
1733 * the cpu's branch prediction hardware and return pc cache. We
1734 * can take advantage of this by not inlining medium-complexity
1735 * functions and we can also reduce the branch prediction impact
1736 * by collapsing perfectly predictable branches into a single
1737 * procedure instead of duplicating it.
1738 *
1739 * Is any of this noticeable? Probably not, so I'll take the
1740 * smaller code size.
1741 */
1742void
b6468f56 1743crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1744{
b6468f56 1745 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1746}
1747
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1748void
1749crit_panic(void)
1750{
1751 thread_t td = curthread;
850634cc 1752 int lcrit = td->td_critcount;
2d93b37a 1753
850634cc
AH
1754 td->td_critcount = 0;
1755 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1756 /* NOT REACHED */
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1757}
1758
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1759/*
1760 * Called from debugger/panic on cpus which have been stopped. We must still
1761 * process the IPIQ while stopped, even if we were stopped while in a critical
1762 * section (XXX).
1763 *
1764 * If we are dumping also try to process any pending interrupts. This may
1765 * or may not work depending on the state of the cpu at the point it was
1766 * stopped.
1767 */
1768void
1769lwkt_smp_stopped(void)
1770{
1771 globaldata_t gd = mycpu;
1772
1773 crit_enter_gd(gd);
1774 if (dumping) {
1775 lwkt_process_ipiq();
1776 splz();
1777 } else {
1778 lwkt_process_ipiq();
1779 }
1780 crit_exit_gd(gd);
1781}