kernel - Add required vm_token back in to swaponvp()
[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
8c10bfcf
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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.
8ad65e08
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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>
f6bf3af1 53#include <sys/caps.h>
9d265729 54#include <sys/spinlock.h>
57aa743c 55#include <sys/ktr.h>
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56
57#include <sys/thread2.h>
58#include <sys/spinlock2.h>
684a93c4 59#include <sys/mplock2.h>
f1d1c3fa 60
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61#include <sys/dsched.h>
62
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63#include <vm/vm.h>
64#include <vm/vm_param.h>
65#include <vm/vm_kern.h>
66#include <vm/vm_object.h>
67#include <vm/vm_page.h>
68#include <vm/vm_map.h>
69#include <vm/vm_pager.h>
70#include <vm/vm_extern.h>
7d0bac62 71
99df837e 72#include <machine/stdarg.h>
96728c05 73#include <machine/smp.h>
99df837e 74
d850923c
AE
75#if !defined(KTR_CTXSW)
76#define KTR_CTXSW KTR_ALL
77#endif
78KTR_INFO_MASTER(ctxsw);
a1f0fb66
AE
79KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p",
80 sizeof(int) + sizeof(struct thread *));
81KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p",
82 sizeof(int) + sizeof(struct thread *));
83KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s",
84 sizeof (struct thread *) + sizeof(char *));
85KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", sizeof (struct thread *));
1541028a 86
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87static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
88
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89#ifdef INVARIANTS
90static int panic_on_cscount = 0;
91#endif
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92static __int64_t switch_count = 0;
93static __int64_t preempt_hit = 0;
94static __int64_t preempt_miss = 0;
95static __int64_t preempt_weird = 0;
85946b6c 96static __int64_t token_contention_count[TDPRI_MAX+1] __debugvar;
fb0f29c4 97static int lwkt_use_spin_port;
40aaf5fc 98static struct objcache *thread_cache;
05220613 99
88ebb169 100#ifdef SMP
e381e77c 101static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 102static void lwkt_setcpu_remote(void *arg);
88ebb169 103#endif
e381e77c 104
0855a2af
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105extern void cpu_heavy_restore(void);
106extern void cpu_lwkt_restore(void);
107extern void cpu_kthread_restore(void);
108extern void cpu_idle_restore(void);
109
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110/*
111 * We can make all thread ports use the spin backend instead of the thread
112 * backend. This should only be set to debug the spin backend.
113 */
114TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
115
0f7a3396 116#ifdef INVARIANTS
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117SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
118 "Panic if attempting to switch lwkt's while mastering cpusync");
0f7a3396 119#endif
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SG
120SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
121 "Number of switched threads");
9733f757 122SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 123 "Successful preemption events");
9733f757 124SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
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125 "Failed preemption events");
126SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
127 "Number of preempted threads.");
38717797 128#ifdef INVARIANTS
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129SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_00, CTLFLAG_RW,
130 &token_contention_count[0], 0, "spinning due to token contention");
131SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_01, CTLFLAG_RW,
132 &token_contention_count[1], 0, "spinning due to token contention");
133SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_02, CTLFLAG_RW,
134 &token_contention_count[2], 0, "spinning due to token contention");
135SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_03, CTLFLAG_RW,
136 &token_contention_count[3], 0, "spinning due to token contention");
137SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_04, CTLFLAG_RW,
138 &token_contention_count[4], 0, "spinning due to token contention");
139SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_05, CTLFLAG_RW,
140 &token_contention_count[5], 0, "spinning due to token contention");
141SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_06, CTLFLAG_RW,
142 &token_contention_count[6], 0, "spinning due to token contention");
143SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_07, CTLFLAG_RW,
144 &token_contention_count[7], 0, "spinning due to token contention");
145SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_08, CTLFLAG_RW,
146 &token_contention_count[8], 0, "spinning due to token contention");
147SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_09, CTLFLAG_RW,
148 &token_contention_count[9], 0, "spinning due to token contention");
149SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_10, CTLFLAG_RW,
150 &token_contention_count[10], 0, "spinning due to token contention");
151SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_11, CTLFLAG_RW,
152 &token_contention_count[11], 0, "spinning due to token contention");
153SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_12, CTLFLAG_RW,
154 &token_contention_count[12], 0, "spinning due to token contention");
155SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_13, CTLFLAG_RW,
156 &token_contention_count[13], 0, "spinning due to token contention");
157SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_14, CTLFLAG_RW,
158 &token_contention_count[14], 0, "spinning due to token contention");
159SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_15, CTLFLAG_RW,
160 &token_contention_count[15], 0, "spinning due to token contention");
161SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_16, CTLFLAG_RW,
162 &token_contention_count[16], 0, "spinning due to token contention");
163SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_17, CTLFLAG_RW,
164 &token_contention_count[17], 0, "spinning due to token contention");
165SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_18, CTLFLAG_RW,
166 &token_contention_count[18], 0, "spinning due to token contention");
167SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_19, CTLFLAG_RW,
168 &token_contention_count[19], 0, "spinning due to token contention");
169SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_20, CTLFLAG_RW,
170 &token_contention_count[20], 0, "spinning due to token contention");
171SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_21, CTLFLAG_RW,
172 &token_contention_count[21], 0, "spinning due to token contention");
173SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_22, CTLFLAG_RW,
174 &token_contention_count[22], 0, "spinning due to token contention");
175SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_23, CTLFLAG_RW,
176 &token_contention_count[23], 0, "spinning due to token contention");
177SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_24, CTLFLAG_RW,
178 &token_contention_count[24], 0, "spinning due to token contention");
179SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_25, CTLFLAG_RW,
180 &token_contention_count[25], 0, "spinning due to token contention");
181SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_26, CTLFLAG_RW,
182 &token_contention_count[26], 0, "spinning due to token contention");
183SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_27, CTLFLAG_RW,
184 &token_contention_count[27], 0, "spinning due to token contention");
185SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_28, CTLFLAG_RW,
186 &token_contention_count[28], 0, "spinning due to token contention");
187SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_29, CTLFLAG_RW,
188 &token_contention_count[29], 0, "spinning due to token contention");
189SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_30, CTLFLAG_RW,
190 &token_contention_count[30], 0, "spinning due to token contention");
191SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_31, CTLFLAG_RW,
192 &token_contention_count[31], 0, "spinning due to token contention");
38717797 193#endif
b12defdc 194static int fairq_enable = 0;
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195SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
196 &fairq_enable, 0, "Turn on fairq priority accumulators");
85946b6c 197static int fairq_bypass = -1;
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MD
198SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
199 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
200extern int lwkt_sched_debug;
201int lwkt_sched_debug = 0;
202SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
203 &lwkt_sched_debug, 0, "Scheduler debug");
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204static int lwkt_spin_loops = 10;
205SYSCTL_INT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
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206 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
207static int lwkt_spin_reseq = 0;
208SYSCTL_INT(_lwkt, OID_AUTO, spin_reseq, CTLFLAG_RW,
209 &lwkt_spin_reseq, 0, "Scheduler resequencer enable");
210static int lwkt_spin_monitor = 0;
211SYSCTL_INT(_lwkt, OID_AUTO, spin_monitor, CTLFLAG_RW,
212 &lwkt_spin_monitor, 0, "Scheduler uses monitor/mwait");
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213static int lwkt_spin_fatal = 0; /* disabled */
214SYSCTL_INT(_lwkt, OID_AUTO, spin_fatal, CTLFLAG_RW,
215 &lwkt_spin_fatal, 0, "LWKT scheduler spin loops till fatal panic");
fbc024e4 216static int preempt_enable = 1;
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217SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
218 &preempt_enable, 0, "Enable preemption");
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219static int lwkt_cache_threads = 32;
220SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
221 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 222
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223static __cachealign int lwkt_cseq_rindex;
224static __cachealign int lwkt_cseq_windex;
05220613 225
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226/*
227 * These helper procedures handle the runq, they can only be called from
228 * within a critical section.
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229 *
230 * WARNING! Prior to SMP being brought up it is possible to enqueue and
231 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
232 * instead of 'mycpu' when referencing the globaldata structure. Once
233 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 234 */
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MD
235static __inline
236void
237_lwkt_dequeue(thread_t td)
238{
239 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 240 struct globaldata *gd = td->td_gd;
4b5f931b 241
f1d1c3fa 242 td->td_flags &= ~TDF_RUNQ;
f9235b6d 243 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 244 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 245 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
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MD
246 }
247}
248
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249/*
250 * Priority enqueue.
251 *
252 * NOTE: There are a limited number of lwkt threads runnable since user
253 * processes only schedule one at a time per cpu.
254 */
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255static __inline
256void
257_lwkt_enqueue(thread_t td)
258{
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259 thread_t xtd;
260
7f5d7ed7 261 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 262 struct globaldata *gd = td->td_gd;
4b5f931b 263
f1d1c3fa 264 td->td_flags |= TDF_RUNQ;
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265 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
266 if (xtd == NULL) {
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MD
267 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
268 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 269 } else {
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MD
270 while (xtd && xtd->td_pri >= td->td_pri)
271 xtd = TAILQ_NEXT(xtd, td_threadq);
272 if (xtd)
273 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
274 else
275 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 276 }
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277
278 /*
85946b6c 279 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 280 */
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281 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
282 need_lwkt_resched();
f1d1c3fa
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283 }
284}
8ad65e08 285
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286static __boolean_t
287_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
288{
289 struct thread *td = (struct thread *)obj;
290
291 td->td_kstack = NULL;
292 td->td_kstack_size = 0;
293 td->td_flags = TDF_ALLOCATED_THREAD;
4643740a 294 td->td_mpflags = 0;
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NT
295 return (1);
296}
297
298static void
299_lwkt_thread_dtor(void *obj, void *privdata)
300{
301 struct thread *td = (struct thread *)obj;
302
303 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
304 ("_lwkt_thread_dtor: not allocated from objcache"));
305 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
306 td->td_kstack_size > 0,
307 ("_lwkt_thread_dtor: corrupted stack"));
308 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
309}
310
311/*
312 * Initialize the lwkt s/system.
765b1ae0
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313 *
314 * Nominally cache up to 32 thread + kstack structures.
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315 */
316void
317lwkt_init(void)
318{
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319 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
320 thread_cache = objcache_create_mbacked(
321 M_THREAD, sizeof(struct thread),
322 NULL, lwkt_cache_threads,
323 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
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NT
324}
325
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326/*
327 * Schedule a thread to run. As the current thread we can always safely
328 * schedule ourselves, and a shortcut procedure is provided for that
329 * function.
330 *
331 * (non-blocking, self contained on a per cpu basis)
332 */
333void
334lwkt_schedule_self(thread_t td)
335{
cfaeae2a 336 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 337 crit_enter_quick(td);
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338 KASSERT(td != &td->td_gd->gd_idlethread,
339 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
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340 KKASSERT(td->td_lwp == NULL ||
341 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
37af14fe 342 _lwkt_enqueue(td);
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343 crit_exit_quick(td);
344}
345
346/*
347 * Deschedule a thread.
348 *
349 * (non-blocking, self contained on a per cpu basis)
350 */
351void
352lwkt_deschedule_self(thread_t td)
353{
354 crit_enter_quick(td);
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355 _lwkt_dequeue(td);
356 crit_exit_quick(td);
357}
358
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359/*
360 * LWKTs operate on a per-cpu basis
361 *
73e4f7b9 362 * WARNING! Called from early boot, 'mycpu' may not work yet.
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363 */
364void
365lwkt_gdinit(struct globaldata *gd)
366{
f9235b6d 367 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 368 TAILQ_INIT(&gd->gd_tdallq);
8ad65e08
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369}
370
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371/*
372 * Create a new thread. The thread must be associated with a process context
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373 * or LWKT start address before it can be scheduled. If the target cpu is
374 * -1 the thread will be created on the current cpu.
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375 *
376 * If you intend to create a thread without a process context this function
377 * does everything except load the startup and switcher function.
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378 */
379thread_t
d3d32139 380lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 381{
d2d8515b 382 static int cpu_rotator;
c070746a 383 globaldata_t gd = mycpu;
99df837e 384 void *stack;
7d0bac62 385
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MD
386 /*
387 * If static thread storage is not supplied allocate a thread. Reuse
388 * a cached free thread if possible. gd_freetd is used to keep an exiting
389 * thread intact through the exit.
390 */
ef0fdad1 391 if (td == NULL) {
cf709dd2
MD
392 crit_enter_gd(gd);
393 if ((td = gd->gd_freetd) != NULL) {
394 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
395 TDF_RUNQ)) == 0);
c070746a 396 gd->gd_freetd = NULL;
cf709dd2 397 } else {
c070746a 398 td = objcache_get(thread_cache, M_WAITOK);
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399 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
400 TDF_RUNQ)) == 0);
401 }
402 crit_exit_gd(gd);
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403 KASSERT((td->td_flags &
404 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD,
405 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
406 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 407 }
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408
409 /*
410 * Try to reuse cached stack.
411 */
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412 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
413 if (flags & TDF_ALLOCATED_STACK) {
e4846942 414 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
415 stack = NULL;
416 }
417 }
418 if (stack == NULL) {
e40cfbd7 419 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 420 flags |= TDF_ALLOCATED_STACK;
99df837e 421 }
d2d8515b
MD
422 if (cpu < 0) {
423 cpu = ++cpu_rotator;
424 cpu_ccfence();
425 cpu %= ncpus;
426 }
427 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 428 return(td);
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MD
429}
430
431/*
432 * Initialize a preexisting thread structure. This function is used by
433 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
434 *
f8c3996b
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435 * All threads start out in a critical section at a priority of
436 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
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437 * appropriate. This function may send an IPI message when the
438 * requested cpu is not the current cpu and consequently gd_tdallq may
439 * not be initialized synchronously from the point of view of the originating
440 * cpu.
441 *
442 * NOTE! we have to be careful in regards to creating threads for other cpus
443 * if SMP has not yet been activated.
7d0bac62 444 */
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445#ifdef SMP
446
75cdbe6c
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447static void
448lwkt_init_thread_remote(void *arg)
449{
450 thread_t td = arg;
451
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452 /*
453 * Protected by critical section held by IPI dispatch
454 */
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455 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
456}
457
41a01a4d
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458#endif
459
fdce8919
MD
460/*
461 * lwkt core thread structural initialization.
462 *
463 * NOTE: All threads are initialized as mpsafe threads.
464 */
7d0bac62 465void
f470d0c8
MD
466lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
467 struct globaldata *gd)
7d0bac62 468{
37af14fe
MD
469 globaldata_t mygd = mycpu;
470
99df837e
MD
471 bzero(td, sizeof(struct thread));
472 td->td_kstack = stack;
f470d0c8 473 td->td_kstack_size = stksize;
d3d32139 474 td->td_flags = flags;
4643740a 475 td->td_mpflags = 0;
26a0694b 476 td->td_gd = gd;
f9235b6d
MD
477 td->td_pri = TDPRI_KERN_DAEMON;
478 td->td_critcount = 1;
54341a3b 479 td->td_toks_have = NULL;
3b998fa9 480 td->td_toks_stop = &td->td_toks_base;
392cd266 481 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT))
fb0f29c4
MD
482 lwkt_initport_spin(&td->td_msgport);
483 else
484 lwkt_initport_thread(&td->td_msgport, td);
99df837e 485 pmap_init_thread(td);
0f7a3396 486#ifdef SMP
5d21b981
MD
487 /*
488 * Normally initializing a thread for a remote cpu requires sending an
489 * IPI. However, the idlethread is setup before the other cpus are
490 * activated so we have to treat it as a special case. XXX manipulation
491 * of gd_tdallq requires the BGL.
492 */
493 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 494 crit_enter_gd(mygd);
75cdbe6c 495 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 496 crit_exit_gd(mygd);
75cdbe6c 497 } else {
2db3b277 498 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 499 }
0f7a3396 500#else
37af14fe 501 crit_enter_gd(mygd);
0f7a3396 502 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 503 crit_exit_gd(mygd);
0f7a3396 504#endif
8c72e3d5
AH
505
506 dsched_new_thread(td);
73e4f7b9
MD
507}
508
509void
510lwkt_set_comm(thread_t td, const char *ctl, ...)
511{
e2565a42 512 __va_list va;
73e4f7b9 513
e2565a42 514 __va_start(va, ctl);
379210cb 515 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 516 __va_end(va);
e7c0dbba 517 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]);
7d0bac62
MD
518}
519
eb2adbf5
MD
520/*
521 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
522 * this does not prevent the thread from migrating to another cpu so the
523 * gd_tdallq state is not protected by this.
524 */
99df837e 525void
73e4f7b9 526lwkt_hold(thread_t td)
99df837e 527{
74c9628e 528 atomic_add_int(&td->td_refs, 1);
73e4f7b9
MD
529}
530
531void
532lwkt_rele(thread_t td)
533{
534 KKASSERT(td->td_refs > 0);
74c9628e 535 atomic_add_int(&td->td_refs, -1);
73e4f7b9
MD
536}
537
538void
539lwkt_wait_free(thread_t td)
540{
541 while (td->td_refs)
377d4740 542 tsleep(td, 0, "tdreap", hz);
73e4f7b9
MD
543}
544
545void
546lwkt_free_thread(thread_t td)
547{
74c9628e 548 KKASSERT(td->td_refs == 0);
c17a6852
MD
549 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
550 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
40aaf5fc
NT
551 if (td->td_flags & TDF_ALLOCATED_THREAD) {
552 objcache_put(thread_cache, td);
553 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
554 /* client-allocated struct with internally allocated stack */
555 KASSERT(td->td_kstack && td->td_kstack_size > 0,
556 ("lwkt_free_thread: corrupted stack"));
557 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
558 td->td_kstack = NULL;
559 td->td_kstack_size = 0;
99df837e 560 }
e7c0dbba 561 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
562}
563
564
8ad65e08
MD
565/*
566 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
567 * switch to the idlethread. Switching must occur within a critical
568 * section to avoid races with the scheduling queue.
569 *
570 * We always have full control over our cpu's run queue. Other cpus
571 * that wish to manipulate our queue must use the cpu_*msg() calls to
572 * talk to our cpu, so a critical section is all that is needed and
573 * the result is very, very fast thread switching.
574 *
96728c05
MD
575 * The LWKT scheduler uses a fixed priority model and round-robins at
576 * each priority level. User process scheduling is a totally
577 * different beast and LWKT priorities should not be confused with
578 * user process priorities.
f1d1c3fa 579 *
69d78e99
MD
580 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
581 * is not called by the current thread in the preemption case, only when
582 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
583 *
584 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
585 * migration and tsleep deschedule the current lwkt thread and call
586 * lwkt_switch(). In particular, the target cpu of the migration fully
587 * expects the thread to become non-runnable and can deadlock against
588 * cpusync operations if we run any IPIs prior to switching the thread out.
589 *
590 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 591 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
592 */
593void
594lwkt_switch(void)
595{
37af14fe
MD
596 globaldata_t gd = mycpu;
597 thread_t td = gd->gd_curthread;
8ad65e08 598 thread_t ntd;
f9235b6d 599 thread_t xtd;
b12defdc 600 int spinning = 0;
8ad65e08 601
da0b0e8b
MD
602 KKASSERT(gd->gd_processing_ipiq == 0);
603
46a3f46d 604 /*
27e88a6e
MD
605 * Switching from within a 'fast' (non thread switched) interrupt or IPI
606 * is illegal. However, we may have to do it anyway if we hit a fatal
607 * kernel trap or we have paniced.
608 *
609 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 610 */
27e88a6e
MD
611 if (gd->gd_intr_nesting_level) {
612 int savegdnest;
613 int savegdtrap;
614
5fddbda2 615 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22
MD
616 panic("lwkt_switch: Attempt to switch from a "
617 "a fast interrupt, ipi, or hard code section, "
618 "td %p\n",
619 td);
27e88a6e
MD
620 } else {
621 savegdnest = gd->gd_intr_nesting_level;
622 savegdtrap = gd->gd_trap_nesting_level;
623 gd->gd_intr_nesting_level = 0;
624 gd->gd_trap_nesting_level = 0;
a7422615
MD
625 if ((td->td_flags & TDF_PANICWARN) == 0) {
626 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
627 kprintf("Warning: thread switch from interrupt, IPI, "
628 "or hard code section.\n"
a7422615 629 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 630 print_backtrace(-1);
a7422615 631 }
27e88a6e
MD
632 lwkt_switch();
633 gd->gd_intr_nesting_level = savegdnest;
634 gd->gd_trap_nesting_level = savegdtrap;
635 return;
636 }
96728c05 637 }
ef0fdad1 638
cb973d15 639 /*
85946b6c
MD
640 * Release our current user process designation if we are blocking
641 * or if a user reschedule was requested.
642 *
643 * NOTE: This function is NOT called if we are switching into or
644 * returning from a preemption.
645 *
646 * NOTE: Releasing our current user process designation may cause
647 * it to be assigned to another thread, which in turn will
648 * cause us to block in the usched acquire code when we attempt
649 * to return to userland.
650 *
651 * NOTE: On SMP systems this can be very nasty when heavy token
652 * contention is present so we want to be careful not to
653 * release the designation gratuitously.
cb973d15 654 */
85946b6c
MD
655 if (td->td_release &&
656 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 657 td->td_release(td);
85946b6c 658 }
cb973d15 659
85946b6c
MD
660 /*
661 * Release all tokens
662 */
37af14fe 663 crit_enter_gd(gd);
3b998fa9 664 if (TD_TOKS_HELD(td))
9d265729
MD
665 lwkt_relalltokens(td);
666
667 /*
b02926de
MD
668 * We had better not be holding any spin locks, but don't get into an
669 * endless panic loop.
9d265729 670 */
d666840a
MD
671 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
672 ("lwkt_switch: still holding %d exclusive spinlocks!",
673 gd->gd_spinlocks_wr));
9d265729 674
8a8d5d85
MD
675
676#ifdef SMP
0f7a3396
MD
677#ifdef INVARIANTS
678 if (td->td_cscount) {
6ea70f76 679 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
680 td);
681 if (panic_on_cscount)
682 panic("switching while mastering cpusync");
683 }
684#endif
8a8d5d85 685#endif
f9235b6d
MD
686
687 /*
688 * If we had preempted another thread on this cpu, resume the preempted
689 * thread. This occurs transparently, whether the preempted thread
690 * was scheduled or not (it may have been preempted after descheduling
691 * itself).
692 *
693 * We have to setup the MP lock for the original thread after backing
694 * out the adjustment that was made to curthread when the original
695 * was preempted.
696 */
99df837e 697 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
698 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
699 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
700
701 /*
b9eb1c19
MD
702 * The interrupt may have woken a thread up, we need to properly
703 * set the reschedule flag if the originally interrupted thread is
704 * at a lower priority.
85946b6c
MD
705 *
706 * The interrupt may not have descheduled.
8ec60c3f 707 */
85946b6c 708 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 709 need_lwkt_resched();
f9235b6d
MD
710 goto havethread_preempted;
711 }
712
b12defdc 713 /*
f9235b6d 714 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
715 * schedule the target thread.
716 *
717 * Reminder: Again, we cannot afford to run any IPIs in this path if
718 * the current thread has been descheduled.
f9235b6d
MD
719 */
720 for (;;) {
b12defdc 721 clear_lwkt_resched();
f9235b6d 722
4b5f931b 723 /*
2a418930 724 * Hotpath - pull the head of the run queue and attempt to schedule
85946b6c 725 * it.
41a01a4d 726 */
2a418930
MD
727 for (;;) {
728 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
729
730 if (ntd == NULL) {
731 /*
b12defdc 732 * Runq is empty, switch to idle to allow it to halt.
2a418930
MD
733 */
734 ntd = &gd->gd_idlethread;
6f207a2c 735#ifdef SMP
2a418930 736 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
b5d16701 737 ASSERT_NO_TOKENS_HELD(ntd);
6f207a2c 738#endif
2a418930
MD
739 cpu_time.cp_msg[0] = 0;
740 cpu_time.cp_stallpc = 0;
2a418930
MD
741 goto haveidle;
742 }
b12defdc 743 break;
f9235b6d 744 }
41a01a4d 745
8ec60c3f 746 /*
b12defdc 747 * Hotpath - schedule ntd.
6f207a2c
MD
748 *
749 * NOTE: For UP there is no mplock and lwkt_getalltokens()
750 * always succeeds.
8ec60c3f 751 */
b12defdc
MD
752 if (TD_TOKS_NOT_HELD(ntd) ||
753 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops)))
754 {
f9235b6d 755 goto havethread;
b12defdc 756 }
f9235b6d 757
f9235b6d 758 /*
2a418930
MD
759 * Coldpath (SMP only since tokens always succeed on UP)
760 *
761 * We had some contention on the thread we wanted to schedule.
762 * What we do now is try to find a thread that we can schedule
b12defdc 763 * in its stead.
2a418930 764 *
85946b6c
MD
765 * The coldpath scan does NOT rearrange threads in the run list.
766 * The lwkt_schedulerclock() will assert need_lwkt_resched() on
767 * the next tick whenever the current head is not the current thread.
f9235b6d 768 */
b12defdc 769#ifdef INVARIANTS
85946b6c
MD
770 ++token_contention_count[ntd->td_pri];
771 ++ntd->td_contended;
b12defdc
MD
772#endif
773
85946b6c 774 if (fairq_bypass > 0)
b12defdc
MD
775 goto skip;
776
b12defdc
MD
777 xtd = NULL;
778 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
85946b6c
MD
779 /*
780 * Never schedule threads returning to userland or the
781 * user thread scheduler helper thread when higher priority
782 * threads are present.
783 */
784 if (ntd->td_pri < TDPRI_KERN_LPSCHED) {
785 ntd = NULL;
786 break;
787 }
788
789 /*
790 * Try this one.
791 */
b12defdc
MD
792 if (TD_TOKS_NOT_HELD(ntd) ||
793 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) {
794 goto havethread;
795 }
85946b6c
MD
796#ifdef INVARIANTS
797 ++token_contention_count[ntd->td_pri];
798 ++ntd->td_contended;
b12defdc 799#endif
2a418930
MD
800 }
801
b12defdc 802skip:
2a418930
MD
803 /*
804 * We exhausted the run list, meaning that all runnable threads
b12defdc 805 * are contested.
2a418930
MD
806 */
807 cpu_pause();
808 ntd = &gd->gd_idlethread;
809#ifdef SMP
810 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
811 ASSERT_NO_TOKENS_HELD(ntd);
812 /* contention case, do not clear contention mask */
813#endif
814
815 /*
b12defdc
MD
816 * We are going to have to retry but if the current thread is not
817 * on the runq we instead switch through the idle thread to get away
818 * from the current thread. We have to flag for lwkt reschedule
819 * to prevent the idle thread from halting.
2a418930 820 *
b12defdc
MD
821 * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to
822 * instruct it to deal with the potential for deadlocks by
823 * ordering the tokens by address.
2a418930 824 */
b12defdc 825 if ((td->td_flags & TDF_RUNQ) == 0) {
85946b6c 826 need_lwkt_resched(); /* prevent hlt */
2a418930 827 goto haveidle;
4b5f931b 828 }
bd52bedf 829#if defined(INVARIANTS) && defined(__amd64__)
d5b2d319
MD
830 if ((read_rflags() & PSL_I) == 0) {
831 cpu_enable_intr();
832 panic("lwkt_switch() called with interrupts disabled");
833 }
834#endif
b12defdc
MD
835
836 /*
837 * Number iterations so far. After a certain point we switch to
838 * a sorted-address/monitor/mwait version of lwkt_getalltokens()
839 */
840 if (spinning < 0x7FFFFFFF)
841 ++spinning;
842
843#ifdef SMP
844 /*
845 * lwkt_getalltokens() failed in sorted token mode, we can use
846 * monitor/mwait in this case.
847 */
848 if (spinning >= lwkt_spin_loops &&
849 (cpu_mi_feature & CPU_MI_MONITOR) &&
850 lwkt_spin_monitor)
851 {
852 cpu_mmw_pause_int(&gd->gd_reqflags,
853 (gd->gd_reqflags | RQF_SPINNING) &
854 ~RQF_IDLECHECK_WK_MASK);
855 }
856#endif
857
858 /*
859 * We already checked that td is still scheduled so this should be
860 * safe.
861 */
862 splz_check();
863
864 /*
865 * This experimental resequencer is used as a fall-back to reduce
866 * hw cache line contention by placing each core's scheduler into a
867 * time-domain-multplexed slot.
868 *
869 * The resequencer is disabled by default. It's functionality has
870 * largely been superceeded by the token algorithm which limits races
871 * to a subset of cores.
872 *
873 * The resequencer algorithm tends to break down when more than
874 * 20 cores are contending. What appears to happen is that new
875 * tokens can be obtained out of address-sorted order by new cores
876 * while existing cores languish in long delays between retries and
877 * wind up being starved-out of the token acquisition.
878 */
879 if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) {
880 int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
881 int oseq;
882
883 while ((oseq = lwkt_cseq_rindex) != cseq) {
884 cpu_ccfence();
885#if 1
886 if (cpu_mi_feature & CPU_MI_MONITOR) {
887 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq);
888 } else {
889#endif
890 cpu_pause();
891 cpu_lfence();
892#if 1
893 }
8b402283 894#endif
0f0466c0 895 }
b12defdc
MD
896 DELAY(1);
897 atomic_add_int(&lwkt_cseq_rindex, 1);
2a418930 898 }
2a418930 899 /* highest level for(;;) loop */
f1d1c3fa 900 }
8a8d5d85 901
2a418930 902havethread:
b12defdc 903 /*
be71787b
MD
904 * Clear gd_idle_repeat when doing a normal switch to a non-idle
905 * thread.
f9235b6d 906 */
9ac1ee6e 907 ntd->td_wmesg = NULL;
b12defdc 908 ++gd->gd_cnt.v_swtch;
be71787b 909 gd->gd_idle_repeat = 0;
2a418930 910
f9235b6d 911havethread_preempted:
f9235b6d
MD
912 /*
913 * If the new target does not need the MP lock and we are holding it,
914 * release the MP lock. If the new target requires the MP lock we have
915 * already acquired it for the target.
8a8d5d85 916 */
2a418930 917 ;
f9235b6d
MD
918haveidle:
919 KASSERT(ntd->td_critcount,
b5d16701
MD
920 ("priority problem in lwkt_switch %d %d",
921 td->td_critcount, ntd->td_critcount));
922
94f6d86e 923 if (td != ntd) {
cc9b6223
MD
924 /*
925 * Execute the actual thread switch operation. This function
926 * returns to the current thread and returns the previous thread
927 * (which may be different from the thread we switched to).
928 *
929 * We are responsible for marking ntd as TDF_RUNNING.
930 */
94f6d86e 931 ++switch_count;
a1f0fb66 932 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
933 ntd->td_flags |= TDF_RUNNING;
934 lwkt_switch_return(td->td_switch(ntd));
935 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 936 }
b12defdc 937
b12defdc 938 /*
54341a3b 939 * catch-all. XXX is this strictly needed?
b12defdc
MD
940 */
941 splz_check();
54341a3b 942
37af14fe
MD
943 /* NOTE: current cpu may have changed after switch */
944 crit_exit_quick(td);
8ad65e08
MD
945}
946
cc9b6223
MD
947/*
948 * Called by assembly in the td_switch (thread restore path) for thread
949 * bootstrap cases which do not 'return' to lwkt_switch().
950 */
951void
952lwkt_switch_return(thread_t otd)
953{
954#ifdef SMP
955 globaldata_t rgd;
956
957 /*
958 * Check if otd was migrating. Now that we are on ntd we can finish
959 * up the migration. This is a bit messy but it is the only place
960 * where td is known to be fully descheduled.
961 *
962 * We can only activate the migration if otd was migrating but not
963 * held on the cpu due to a preemption chain. We still have to
964 * clear TDF_RUNNING on the old thread either way.
965 *
966 * We are responsible for clearing the previously running thread's
967 * TDF_RUNNING.
968 */
969 if ((rgd = otd->td_migrate_gd) != NULL &&
970 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
971 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
972 (TDF_MIGRATING | TDF_RUNNING));
973 otd->td_migrate_gd = NULL;
974 otd->td_flags &= ~TDF_RUNNING;
975 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
976 } else {
977 otd->td_flags &= ~TDF_RUNNING;
978 }
979#else
980 otd->td_flags &= ~TDF_RUNNING;
981#endif
982}
983
b68b7282 984/*
96728c05 985 * Request that the target thread preempt the current thread. Preemption
54341a3b
MD
986 * can only occur if our only critical section is the one that we were called
987 * with, the relative priority of the target thread is higher, and the target
988 * thread holds no tokens. This also only works if we are not holding any
989 * spinlocks (obviously).
96728c05
MD
990 *
991 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
992 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 993 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
994 * to determine whether preemption is possible (aka usually just the crit
995 * priority of lwkt_schedule() itself).
b68b7282 996 *
54341a3b
MD
997 * Preemption is typically limited to interrupt threads.
998 *
999 * Operation works in a fairly straight-forward manner. The normal
1000 * scheduling code is bypassed and we switch directly to the target
1001 * thread. When the target thread attempts to block or switch away
1002 * code at the base of lwkt_switch() will switch directly back to our
1003 * thread. Our thread is able to retain whatever tokens it holds and
1004 * if the target needs one of them the target will switch back to us
1005 * and reschedule itself normally.
b68b7282
MD
1006 */
1007void
f9235b6d 1008lwkt_preempt(thread_t ntd, int critcount)
b68b7282 1009{
46a3f46d 1010 struct globaldata *gd = mycpu;
cc9b6223 1011 thread_t xtd;
0a3f9b47 1012 thread_t td;
2d910aaf 1013 int save_gd_intr_nesting_level;
b68b7282 1014
26a0694b 1015 /*
96728c05
MD
1016 * The caller has put us in a critical section. We can only preempt
1017 * if the caller of the caller was not in a critical section (basically
f9235b6d 1018 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 1019 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 1020 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
1021 *
1022 * YYY The target thread must be in a critical section (else it must
1023 * inherit our critical section? I dunno yet).
26a0694b 1024 */
f9235b6d 1025 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 1026
b12defdc 1027 td = gd->gd_curthread;
fbc024e4
MD
1028 if (preempt_enable == 0) {
1029 ++preempt_miss;
1030 return;
1031 }
f9235b6d 1032 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
1033 ++preempt_miss;
1034 return;
1035 }
f9235b6d 1036 if (td->td_critcount > critcount) {
96728c05
MD
1037 ++preempt_miss;
1038 return;
1039 }
1040#ifdef SMP
46a3f46d 1041 if (ntd->td_gd != gd) {
96728c05
MD
1042 ++preempt_miss;
1043 return;
1044 }
1045#endif
41a01a4d 1046 /*
77912481
MD
1047 * We don't have to check spinlocks here as they will also bump
1048 * td_critcount.
d3d1cbc8
MD
1049 *
1050 * Do not try to preempt if the target thread is holding any tokens.
1051 * We could try to acquire the tokens but this case is so rare there
1052 * is no need to support it.
41a01a4d 1053 */
77912481
MD
1054 KKASSERT(gd->gd_spinlocks_wr == 0);
1055
3b998fa9 1056 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 1057 ++preempt_miss;
d3d1cbc8
MD
1058 return;
1059 }
26a0694b
MD
1060 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1061 ++preempt_weird;
1062 return;
1063 }
1064 if (ntd->td_preempted) {
4b5f931b 1065 ++preempt_hit;
26a0694b 1066 return;
b68b7282 1067 }
da0b0e8b 1068 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1069
8ec60c3f
MD
1070 /*
1071 * Since we are able to preempt the current thread, there is no need to
1072 * call need_lwkt_resched().
2d910aaf
MD
1073 *
1074 * We must temporarily clear gd_intr_nesting_level around the switch
1075 * since switchouts from the target thread are allowed (they will just
1076 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1077 *
1078 * A preemption must switch back to the original thread, assert the
1079 * case.
8ec60c3f 1080 */
26a0694b
MD
1081 ++preempt_hit;
1082 ntd->td_preempted = td;
1083 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1084 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1085 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1086 gd->gd_intr_nesting_level = 0;
cc9b6223
MD
1087 ntd->td_flags |= TDF_RUNNING;
1088 xtd = td->td_switch(ntd);
1089 KKASSERT(xtd == ntd);
1090 lwkt_switch_return(xtd);
2d910aaf 1091 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1092
26a0694b
MD
1093 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1094 ntd->td_preempted = NULL;
1095 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1096}
1097
f1d1c3fa 1098/*
faaeffac 1099 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1100 * This will work inside a critical section but not inside a hard code
1101 * section.
ef0fdad1 1102 *
f1d1c3fa
MD
1103 * (self contained on a per cpu basis)
1104 */
1105void
faaeffac 1106splz_check(void)
f1d1c3fa 1107{
7966cb69
MD
1108 globaldata_t gd = mycpu;
1109 thread_t td = gd->gd_curthread;
ef0fdad1 1110
4a28fe22
MD
1111 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1112 gd->gd_intr_nesting_level == 0 &&
1113 td->td_nest_count < 2)
1114 {
f1d1c3fa 1115 splz();
4a28fe22
MD
1116 }
1117}
1118
1119/*
1120 * This version is integrated into crit_exit, reqflags has already
1121 * been tested but td_critcount has not.
1122 *
1123 * We only want to execute the splz() on the 1->0 transition of
1124 * critcount and not in a hard code section or if too deeply nested.
1125 */
1126void
1127lwkt_maybe_splz(thread_t td)
1128{
1129 globaldata_t gd = td->td_gd;
1130
1131 if (td->td_critcount == 0 &&
1132 gd->gd_intr_nesting_level == 0 &&
1133 td->td_nest_count < 2)
1134 {
1135 splz();
1136 }
f1d1c3fa
MD
1137}
1138
e6546af9
MD
1139/*
1140 * Drivers which set up processing co-threads can call this function to
1141 * run the co-thread at a higher priority and to allow it to preempt
1142 * normal threads.
1143 */
1144void
1145lwkt_set_interrupt_support_thread(void)
1146{
1147 thread_t td = curthread;
1148
1149 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1150 td->td_flags |= TDF_INTTHREAD;
1151 td->td_preemptable = lwkt_preempt;
1152}
1153
1154
8ad65e08 1155/*
f9235b6d
MD
1156 * This function is used to negotiate a passive release of the current
1157 * process/lwp designation with the user scheduler, allowing the user
1158 * scheduler to schedule another user thread. The related kernel thread
1159 * (curthread) continues running in the released state.
8ad65e08
MD
1160 */
1161void
f9235b6d 1162lwkt_passive_release(struct thread *td)
8ad65e08 1163{
f9235b6d
MD
1164 struct lwp *lp = td->td_lwp;
1165
1166 td->td_release = NULL;
1167 lwkt_setpri_self(TDPRI_KERN_USER);
1168 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1169}
1170
f9235b6d 1171
3824f392 1172/*
d2d8515b
MD
1173 * This implements a LWKT yield, allowing a kernel thread to yield to other
1174 * kernel threads at the same or higher priority. This function can be
1175 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1176 *
d2d8515b
MD
1177 * Most kernel threads run at the same priority in order to allow equal
1178 * sharing.
f9235b6d
MD
1179 *
1180 * (self contained on a per cpu basis)
3824f392
MD
1181 */
1182void
f9235b6d 1183lwkt_yield(void)
3824f392 1184{
f9235b6d
MD
1185 globaldata_t gd = mycpu;
1186 thread_t td = gd->gd_curthread;
3824f392 1187
f9235b6d
MD
1188 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1189 splz();
85946b6c 1190 if (lwkt_resched_wanted()) {
f9235b6d
MD
1191 lwkt_schedule_self(curthread);
1192 lwkt_switch();
f9235b6d 1193 }
3824f392
MD
1194}
1195
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 */
0f7a3396 1290#ifdef SMP
7cd8d145 1291 if (td->td_gd == mygd) {
9d265729 1292 _lwkt_enqueue(td);
85946b6c 1293 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1294 } else {
e381e77c 1295 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1296 }
0f7a3396 1297#else
7cd8d145 1298 _lwkt_enqueue(td);
85946b6c 1299 _lwkt_schedule_post(mygd, td, 1);
0f7a3396 1300#endif
8ad65e08 1301 }
37af14fe 1302 crit_exit_gd(mygd);
8ad65e08
MD
1303}
1304
361d01dd
MD
1305void
1306lwkt_schedule(thread_t td)
1307{
85946b6c 1308 _lwkt_schedule(td);
361d01dd
MD
1309}
1310
1311void
85946b6c 1312lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1313{
85946b6c 1314 _lwkt_schedule(td);
361d01dd
MD
1315}
1316
88ebb169
SW
1317#ifdef SMP
1318
e381e77c
MD
1319/*
1320 * When scheduled remotely if frame != NULL the IPIQ is being
1321 * run via doreti or an interrupt then preemption can be allowed.
1322 *
1323 * To allow preemption we have to drop the critical section so only
1324 * one is present in _lwkt_schedule_post.
1325 */
1326static void
1327lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1328{
1329 thread_t td = curthread;
1330 thread_t ntd = arg;
1331
1332 if (frame && ntd->td_preemptable) {
1333 crit_exit_noyield(td);
85946b6c 1334 _lwkt_schedule(ntd);
e381e77c
MD
1335 crit_enter_quick(td);
1336 } else {
85946b6c 1337 _lwkt_schedule(ntd);
e381e77c
MD
1338 }
1339}
1340
d9eea1a5 1341/*
52eedfb5
MD
1342 * Thread migration using a 'Pull' method. The thread may or may not be
1343 * the current thread. It MUST be descheduled and in a stable state.
1344 * lwkt_giveaway() must be called on the cpu owning the thread.
1345 *
1346 * At any point after lwkt_giveaway() is called, the target cpu may
1347 * 'pull' the thread by calling lwkt_acquire().
1348 *
ae8e83e6
MD
1349 * We have to make sure the thread is not sitting on a per-cpu tsleep
1350 * queue or it will blow up when it moves to another cpu.
1351 *
52eedfb5 1352 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1353 */
52eedfb5
MD
1354void
1355lwkt_giveaway(thread_t td)
1356{
3b4192fb 1357 globaldata_t gd = mycpu;
52eedfb5 1358
3b4192fb
MD
1359 crit_enter_gd(gd);
1360 if (td->td_flags & TDF_TSLEEPQ)
1361 tsleep_remove(td);
1362 KKASSERT(td->td_gd == gd);
1363 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1364 td->td_flags |= TDF_MIGRATING;
1365 crit_exit_gd(gd);
52eedfb5
MD
1366}
1367
a2a5ad0d
MD
1368void
1369lwkt_acquire(thread_t td)
1370{
37af14fe
MD
1371 globaldata_t gd;
1372 globaldata_t mygd;
cc9b6223 1373 int retry = 10000000;
a2a5ad0d 1374
52eedfb5 1375 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1376 gd = td->td_gd;
37af14fe 1377 mygd = mycpu;
52eedfb5 1378 if (gd != mycpu) {
35238fa5 1379 cpu_lfence();
52eedfb5 1380 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1381 crit_enter_gd(mygd);
cfaeae2a 1382 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23
MD
1383 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1384#ifdef SMP
1385 lwkt_process_ipiq();
1386#endif
52eedfb5 1387 cpu_lfence();
cc9b6223
MD
1388 if (--retry == 0) {
1389 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1390 td, td->td_flags);
1391 retry = 10000000;
1392 }
df910c23 1393 }
cfaeae2a 1394 DEBUG_POP_INFO();
562273ea 1395 cpu_mfence();
37af14fe 1396 td->td_gd = mygd;
52eedfb5
MD
1397 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1398 td->td_flags &= ~TDF_MIGRATING;
1399 crit_exit_gd(mygd);
1400 } else {
1401 crit_enter_gd(mygd);
1402 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1403 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1404 crit_exit_gd(mygd);
a2a5ad0d
MD
1405 }
1406}
1407
52eedfb5
MD
1408#endif
1409
f1d1c3fa
MD
1410/*
1411 * Generic deschedule. Descheduling threads other then your own should be
1412 * done only in carefully controlled circumstances. Descheduling is
1413 * asynchronous.
1414 *
1415 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1416 */
1417void
1418lwkt_deschedule(thread_t td)
1419{
f1d1c3fa 1420 crit_enter();
b8a98473 1421#ifdef SMP
f1d1c3fa
MD
1422 if (td == curthread) {
1423 _lwkt_dequeue(td);
1424 } else {
a72187e9 1425 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1426 _lwkt_dequeue(td);
1427 } else {
b8a98473 1428 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1429 }
1430 }
b8a98473
MD
1431#else
1432 _lwkt_dequeue(td);
1433#endif
f1d1c3fa
MD
1434 crit_exit();
1435}
1436
4b5f931b
MD
1437/*
1438 * Set the target thread's priority. This routine does not automatically
1439 * switch to a higher priority thread, LWKT threads are not designed for
1440 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1441 */
1442void
1443lwkt_setpri(thread_t td, int pri)
1444{
f9235b6d
MD
1445 if (td->td_pri != pri) {
1446 KKASSERT(pri >= 0);
1447 crit_enter();
1448 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1449 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1450 _lwkt_dequeue(td);
1451 td->td_pri = pri;
1452 _lwkt_enqueue(td);
1453 } else {
1454 td->td_pri = pri;
1455 }
1456 crit_exit();
26a0694b 1457 }
26a0694b
MD
1458}
1459
03bd0a5e
MD
1460/*
1461 * Set the initial priority for a thread prior to it being scheduled for
1462 * the first time. The thread MUST NOT be scheduled before or during
1463 * this call. The thread may be assigned to a cpu other then the current
1464 * cpu.
1465 *
1466 * Typically used after a thread has been created with TDF_STOPPREQ,
1467 * and before the thread is initially scheduled.
1468 */
1469void
1470lwkt_setpri_initial(thread_t td, int pri)
1471{
1472 KKASSERT(pri >= 0);
1473 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1474 td->td_pri = pri;
03bd0a5e
MD
1475}
1476
26a0694b
MD
1477void
1478lwkt_setpri_self(int pri)
1479{
1480 thread_t td = curthread;
1481
4b5f931b
MD
1482 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1483 crit_enter();
1484 if (td->td_flags & TDF_RUNQ) {
1485 _lwkt_dequeue(td);
f9235b6d 1486 td->td_pri = pri;
4b5f931b
MD
1487 _lwkt_enqueue(td);
1488 } else {
f9235b6d 1489 td->td_pri = pri;
4b5f931b
MD
1490 }
1491 crit_exit();
1492}
1493
f9235b6d 1494/*
85946b6c 1495 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1496 */
1497void
85946b6c 1498lwkt_schedulerclock(thread_t td)
f9235b6d 1499{
85946b6c
MD
1500 globaldata_t gd = td->td_gd;
1501 thread_t xtd;
2a418930 1502
85946b6c
MD
1503 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1504 /*
1505 * If the current thread is at the head of the runq shift it to the
1506 * end of any equal-priority threads and request a LWKT reschedule
1507 * if it moved.
1508 */
1509 xtd = TAILQ_NEXT(td, td_threadq);
1510 if (xtd && xtd->td_pri == td->td_pri) {
1511 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1512 while (xtd && xtd->td_pri == td->td_pri)
1513 xtd = TAILQ_NEXT(xtd, td_threadq);
1514 if (xtd)
1515 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1516 else
1517 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1518 need_lwkt_resched();
f9235b6d 1519 }
85946b6c
MD
1520 } else {
1521 /*
1522 * If we scheduled a thread other than the one at the head of the
1523 * queue always request a reschedule every tick.
1524 */
1525 need_lwkt_resched();
f9235b6d
MD
1526 }
1527}
1528
5d21b981 1529/*
52eedfb5
MD
1530 * Migrate the current thread to the specified cpu.
1531 *
cc9b6223
MD
1532 * This is accomplished by descheduling ourselves from the current cpu
1533 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1534 * 'old' thread wants to migrate after it has been completely switched out
1535 * and will complete the migration.
1536 *
1537 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1538 *
1539 * We must be sure to release our current process designation (if a user
1540 * process) before clearing out any tsleepq we are on because the release
1541 * code may re-add us.
ae8e83e6
MD
1542 *
1543 * We must be sure to remove ourselves from the current cpu's tsleepq
1544 * before potentially moving to another queue. The thread can be on
1545 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1546 */
5d21b981
MD
1547
1548void
1549lwkt_setcpu_self(globaldata_t rgd)
1550{
1551#ifdef SMP
1552 thread_t td = curthread;
1553
1554 if (td->td_gd != rgd) {
1555 crit_enter_quick(td);
cc9b6223 1556
95858b91
MD
1557 if (td->td_release)
1558 td->td_release(td);
ae8e83e6 1559 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1560 tsleep_remove(td);
cc9b6223
MD
1561
1562 /*
1563 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1564 * trying to deschedule ourselves and switch away, then deschedule
1565 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1566 * call lwkt_switch() to complete the operation.
1567 */
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1568 td->td_flags |= TDF_MIGRATING;
1569 lwkt_deschedule_self(td);
52eedfb5 1570 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1571 td->td_migrate_gd = rgd;
5d21b981 1572 lwkt_switch();
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1573
1574 /*
1575 * We are now on the target cpu
1576 */
1577 KKASSERT(rgd == mycpu);
52eedfb5 1578 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
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1579 crit_exit_quick(td);
1580 }
1581#endif
1582}
1583
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1584void
1585lwkt_migratecpu(int cpuid)
1586{
1587#ifdef SMP
1588 globaldata_t rgd;
1589
1590 rgd = globaldata_find(cpuid);
1591 lwkt_setcpu_self(rgd);
1592#endif
1593}
1594
cc9b6223 1595#ifdef SMP
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1596/*
1597 * Remote IPI for cpu migration (called while in a critical section so we
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1598 * do not have to enter another one).
1599 *
1600 * The thread (td) has already been completely descheduled from the
1601 * originating cpu and we can simply assert the case. The thread is
1602 * assigned to the new cpu and enqueued.
5d21b981 1603 *
cc9b6223 1604 * The thread will re-add itself to tdallq when it resumes execution.
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1605 */
1606static void
1607lwkt_setcpu_remote(void *arg)
1608{
1609 thread_t td = arg;
1610 globaldata_t gd = mycpu;
1611
cc9b6223 1612 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1613 td->td_gd = gd;
562273ea 1614 cpu_mfence();
5d21b981 1615 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1616 KKASSERT(td->td_migrate_gd == NULL);
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1617 KKASSERT(td->td_lwp == NULL ||
1618 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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1619 _lwkt_enqueue(td);
1620}
3d28ff59 1621#endif
5d21b981 1622
553ea3c8 1623struct lwp *
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1624lwkt_preempted_proc(void)
1625{
73e4f7b9 1626 thread_t td = curthread;
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1627 while (td->td_preempted)
1628 td = td->td_preempted;
553ea3c8 1629 return(td->td_lwp);
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1630}
1631
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1632/*
1633 * Create a kernel process/thread/whatever. It shares it's address space
1634 * with proc0 - ie: kernel only.
1635 *
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1636 * If the cpu is not specified one will be selected. In the future
1637 * specifying a cpu of -1 will enable kernel thread migration between
1638 * cpus.
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1639 */
1640int
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1641lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1642 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1643{
73e4f7b9 1644 thread_t td;
e2565a42 1645 __va_list ap;
99df837e 1646
d3d32139 1647 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1648 tdflags);
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1649 if (tdp)
1650 *tdp = td;
709799ea 1651 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1652
1653 /*
1654 * Set up arg0 for 'ps' etc
1655 */
e2565a42 1656 __va_start(ap, fmt);
379210cb 1657 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1658 __va_end(ap);
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1659
1660 /*
1661 * Schedule the thread to run
1662 */
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1663 if (td->td_flags & TDF_NOSTART)
1664 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1665 else
4643740a 1666 lwkt_schedule(td);
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1667 return 0;
1668}
1669
1670/*
1671 * Destroy an LWKT thread. Warning! This function is not called when
1672 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1673 * uses a different reaping mechanism.
1674 */
1675void
1676lwkt_exit(void)
1677{
1678 thread_t td = curthread;
c070746a 1679 thread_t std;
8826f33a 1680 globaldata_t gd;
99df837e 1681
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1682 /*
1683 * Do any cleanup that might block here
1684 */
99df837e 1685 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1686 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1687 caps_exit(td);
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1688 biosched_done(td);
1689 dsched_exit_thread(td);
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1690
1691 /*
1692 * Get us into a critical section to interlock gd_freetd and loop
1693 * until we can get it freed.
1694 *
1695 * We have to cache the current td in gd_freetd because objcache_put()ing
1696 * it would rip it out from under us while our thread is still active.
1697 */
1698 gd = mycpu;
37af14fe 1699 crit_enter_quick(td);
eb2adbf5 1700 lwkt_wait_free(td);
c070746a 1701 while ((std = gd->gd_freetd) != NULL) {
cf709dd2 1702 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
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1703 gd->gd_freetd = NULL;
1704 objcache_put(thread_cache, std);
eb2adbf5 1705 lwkt_wait_free(td);
c070746a 1706 }
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1707
1708 /*
1709 * Remove thread resources from kernel lists and deschedule us for
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1710 * the last time. We cannot block after this point or we may end
1711 * up with a stale td on the tsleepq.
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1712 *
1713 * None of this may block, the critical section is the only thing
1714 * protecting tdallq and the only thing preventing new lwkt_hold()
1715 * thread refs now.
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1716 */
1717 if (td->td_flags & TDF_TSLEEPQ)
1718 tsleep_remove(td);
37af14fe 1719 lwkt_deschedule_self(td);
e56e4dea 1720 lwkt_remove_tdallq(td);
74c9628e 1721 KKASSERT(td->td_refs == 0);
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1722
1723 /*
1724 * Final cleanup
1725 */
1726 KKASSERT(gd->gd_freetd == NULL);
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1727 if (td->td_flags & TDF_ALLOCATED_THREAD)
1728 gd->gd_freetd = td;
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1729 cpu_thread_exit();
1730}
1731
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1732void
1733lwkt_remove_tdallq(thread_t td)
1734{
1735 KKASSERT(td->td_gd == mycpu);
1736 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1737}
1738
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1739/*
1740 * Code reduction and branch prediction improvements. Call/return
1741 * overhead on modern cpus often degenerates into 0 cycles due to
1742 * the cpu's branch prediction hardware and return pc cache. We
1743 * can take advantage of this by not inlining medium-complexity
1744 * functions and we can also reduce the branch prediction impact
1745 * by collapsing perfectly predictable branches into a single
1746 * procedure instead of duplicating it.
1747 *
1748 * Is any of this noticeable? Probably not, so I'll take the
1749 * smaller code size.
1750 */
1751void
b6468f56 1752crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1753{
b6468f56 1754 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1755}
1756
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1757void
1758crit_panic(void)
1759{
1760 thread_t td = curthread;
850634cc 1761 int lcrit = td->td_critcount;
2d93b37a 1762
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1763 td->td_critcount = 0;
1764 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1765 /* NOT REACHED */
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1766}
1767
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1768#ifdef SMP
1769
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1770/*
1771 * Called from debugger/panic on cpus which have been stopped. We must still
1772 * process the IPIQ while stopped, even if we were stopped while in a critical
1773 * section (XXX).
1774 *
1775 * If we are dumping also try to process any pending interrupts. This may
1776 * or may not work depending on the state of the cpu at the point it was
1777 * stopped.
1778 */
1779void
1780lwkt_smp_stopped(void)
1781{
1782 globaldata_t gd = mycpu;
1783
1784 crit_enter_gd(gd);
1785 if (dumping) {
1786 lwkt_process_ipiq();
1787 splz();
1788 } else {
1789 lwkt_process_ipiq();
1790 }
1791 crit_exit_gd(gd);
1792}
1793
d165e668 1794#endif