kernel - Fix alarm() timer race against exit
[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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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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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
MD
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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NT
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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MD
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.
0cfcada1
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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);
40aaf5fc 403 KASSERT((td->td_flags &
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MD
404 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
405 TDF_ALLOCATED_THREAD,
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406 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
407 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 408 }
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409
410 /*
411 * Try to reuse cached stack.
412 */
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413 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
414 if (flags & TDF_ALLOCATED_STACK) {
e4846942 415 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
416 stack = NULL;
417 }
418 }
419 if (stack == NULL) {
e40cfbd7 420 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 421 flags |= TDF_ALLOCATED_STACK;
99df837e 422 }
d2d8515b
MD
423 if (cpu < 0) {
424 cpu = ++cpu_rotator;
425 cpu_ccfence();
426 cpu %= ncpus;
427 }
428 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 429 return(td);
7d0bac62
MD
430}
431
432/*
433 * Initialize a preexisting thread structure. This function is used by
434 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
435 *
f8c3996b
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436 * All threads start out in a critical section at a priority of
437 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
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438 * appropriate. This function may send an IPI message when the
439 * requested cpu is not the current cpu and consequently gd_tdallq may
440 * not be initialized synchronously from the point of view of the originating
441 * cpu.
442 *
443 * NOTE! we have to be careful in regards to creating threads for other cpus
444 * if SMP has not yet been activated.
7d0bac62 445 */
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446#ifdef SMP
447
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448static void
449lwkt_init_thread_remote(void *arg)
450{
451 thread_t td = arg;
452
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453 /*
454 * Protected by critical section held by IPI dispatch
455 */
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456 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
457}
458
41a01a4d
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459#endif
460
fdce8919
MD
461/*
462 * lwkt core thread structural initialization.
463 *
464 * NOTE: All threads are initialized as mpsafe threads.
465 */
7d0bac62 466void
f470d0c8
MD
467lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
468 struct globaldata *gd)
7d0bac62 469{
37af14fe
MD
470 globaldata_t mygd = mycpu;
471
99df837e
MD
472 bzero(td, sizeof(struct thread));
473 td->td_kstack = stack;
f470d0c8 474 td->td_kstack_size = stksize;
d3d32139 475 td->td_flags = flags;
4643740a 476 td->td_mpflags = 0;
26a0694b 477 td->td_gd = gd;
f9235b6d
MD
478 td->td_pri = TDPRI_KERN_DAEMON;
479 td->td_critcount = 1;
54341a3b 480 td->td_toks_have = NULL;
3b998fa9 481 td->td_toks_stop = &td->td_toks_base;
392cd266 482 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT))
fb0f29c4
MD
483 lwkt_initport_spin(&td->td_msgport);
484 else
485 lwkt_initport_thread(&td->td_msgport, td);
99df837e 486 pmap_init_thread(td);
0f7a3396 487#ifdef SMP
5d21b981
MD
488 /*
489 * Normally initializing a thread for a remote cpu requires sending an
490 * IPI. However, the idlethread is setup before the other cpus are
491 * activated so we have to treat it as a special case. XXX manipulation
492 * of gd_tdallq requires the BGL.
493 */
494 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 495 crit_enter_gd(mygd);
75cdbe6c 496 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 497 crit_exit_gd(mygd);
75cdbe6c 498 } else {
2db3b277 499 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 500 }
0f7a3396 501#else
37af14fe 502 crit_enter_gd(mygd);
0f7a3396 503 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 504 crit_exit_gd(mygd);
0f7a3396 505#endif
8c72e3d5
AH
506
507 dsched_new_thread(td);
73e4f7b9
MD
508}
509
510void
511lwkt_set_comm(thread_t td, const char *ctl, ...)
512{
e2565a42 513 __va_list va;
73e4f7b9 514
e2565a42 515 __va_start(va, ctl);
379210cb 516 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 517 __va_end(va);
e7c0dbba 518 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]);
7d0bac62
MD
519}
520
eb2adbf5
MD
521/*
522 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
523 * this does not prevent the thread from migrating to another cpu so the
524 * gd_tdallq state is not protected by this.
525 */
99df837e 526void
73e4f7b9 527lwkt_hold(thread_t td)
99df837e 528{
74c9628e 529 atomic_add_int(&td->td_refs, 1);
73e4f7b9
MD
530}
531
532void
533lwkt_rele(thread_t td)
534{
535 KKASSERT(td->td_refs > 0);
74c9628e 536 atomic_add_int(&td->td_refs, -1);
73e4f7b9
MD
537}
538
73e4f7b9
MD
539void
540lwkt_free_thread(thread_t td)
541{
74c9628e 542 KKASSERT(td->td_refs == 0);
c17a6852
MD
543 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
544 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
40aaf5fc
NT
545 if (td->td_flags & TDF_ALLOCATED_THREAD) {
546 objcache_put(thread_cache, td);
547 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
548 /* client-allocated struct with internally allocated stack */
549 KASSERT(td->td_kstack && td->td_kstack_size > 0,
550 ("lwkt_free_thread: corrupted stack"));
551 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
552 td->td_kstack = NULL;
553 td->td_kstack_size = 0;
99df837e 554 }
e7c0dbba 555 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
556}
557
558
8ad65e08
MD
559/*
560 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
561 * switch to the idlethread. Switching must occur within a critical
562 * section to avoid races with the scheduling queue.
563 *
564 * We always have full control over our cpu's run queue. Other cpus
565 * that wish to manipulate our queue must use the cpu_*msg() calls to
566 * talk to our cpu, so a critical section is all that is needed and
567 * the result is very, very fast thread switching.
568 *
96728c05
MD
569 * The LWKT scheduler uses a fixed priority model and round-robins at
570 * each priority level. User process scheduling is a totally
571 * different beast and LWKT priorities should not be confused with
572 * user process priorities.
f1d1c3fa 573 *
69d78e99
MD
574 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
575 * is not called by the current thread in the preemption case, only when
576 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
577 *
578 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
579 * migration and tsleep deschedule the current lwkt thread and call
580 * lwkt_switch(). In particular, the target cpu of the migration fully
581 * expects the thread to become non-runnable and can deadlock against
582 * cpusync operations if we run any IPIs prior to switching the thread out.
583 *
584 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 585 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
586 */
587void
588lwkt_switch(void)
589{
37af14fe
MD
590 globaldata_t gd = mycpu;
591 thread_t td = gd->gd_curthread;
8ad65e08 592 thread_t ntd;
f9235b6d 593 thread_t xtd;
b12defdc 594 int spinning = 0;
8ad65e08 595
da0b0e8b
MD
596 KKASSERT(gd->gd_processing_ipiq == 0);
597
46a3f46d 598 /*
27e88a6e
MD
599 * Switching from within a 'fast' (non thread switched) interrupt or IPI
600 * is illegal. However, we may have to do it anyway if we hit a fatal
601 * kernel trap or we have paniced.
602 *
603 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 604 */
27e88a6e
MD
605 if (gd->gd_intr_nesting_level) {
606 int savegdnest;
607 int savegdtrap;
608
5fddbda2 609 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22
MD
610 panic("lwkt_switch: Attempt to switch from a "
611 "a fast interrupt, ipi, or hard code section, "
612 "td %p\n",
613 td);
27e88a6e
MD
614 } else {
615 savegdnest = gd->gd_intr_nesting_level;
616 savegdtrap = gd->gd_trap_nesting_level;
617 gd->gd_intr_nesting_level = 0;
618 gd->gd_trap_nesting_level = 0;
a7422615
MD
619 if ((td->td_flags & TDF_PANICWARN) == 0) {
620 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
621 kprintf("Warning: thread switch from interrupt, IPI, "
622 "or hard code section.\n"
a7422615 623 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 624 print_backtrace(-1);
a7422615 625 }
27e88a6e
MD
626 lwkt_switch();
627 gd->gd_intr_nesting_level = savegdnest;
628 gd->gd_trap_nesting_level = savegdtrap;
629 return;
630 }
96728c05 631 }
ef0fdad1 632
cb973d15 633 /*
85946b6c
MD
634 * Release our current user process designation if we are blocking
635 * or if a user reschedule was requested.
636 *
637 * NOTE: This function is NOT called if we are switching into or
638 * returning from a preemption.
639 *
640 * NOTE: Releasing our current user process designation may cause
641 * it to be assigned to another thread, which in turn will
642 * cause us to block in the usched acquire code when we attempt
643 * to return to userland.
644 *
645 * NOTE: On SMP systems this can be very nasty when heavy token
646 * contention is present so we want to be careful not to
647 * release the designation gratuitously.
cb973d15 648 */
85946b6c
MD
649 if (td->td_release &&
650 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 651 td->td_release(td);
85946b6c 652 }
cb973d15 653
85946b6c
MD
654 /*
655 * Release all tokens
656 */
37af14fe 657 crit_enter_gd(gd);
3b998fa9 658 if (TD_TOKS_HELD(td))
9d265729
MD
659 lwkt_relalltokens(td);
660
661 /*
b02926de
MD
662 * We had better not be holding any spin locks, but don't get into an
663 * endless panic loop.
9d265729 664 */
d666840a
MD
665 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
666 ("lwkt_switch: still holding %d exclusive spinlocks!",
667 gd->gd_spinlocks_wr));
9d265729 668
8a8d5d85
MD
669
670#ifdef SMP
0f7a3396
MD
671#ifdef INVARIANTS
672 if (td->td_cscount) {
6ea70f76 673 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
674 td);
675 if (panic_on_cscount)
676 panic("switching while mastering cpusync");
677 }
678#endif
8a8d5d85 679#endif
f9235b6d
MD
680
681 /*
682 * If we had preempted another thread on this cpu, resume the preempted
683 * thread. This occurs transparently, whether the preempted thread
684 * was scheduled or not (it may have been preempted after descheduling
685 * itself).
686 *
687 * We have to setup the MP lock for the original thread after backing
688 * out the adjustment that was made to curthread when the original
689 * was preempted.
690 */
99df837e 691 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
692 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
693 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
694
695 /*
b9eb1c19
MD
696 * The interrupt may have woken a thread up, we need to properly
697 * set the reschedule flag if the originally interrupted thread is
698 * at a lower priority.
85946b6c
MD
699 *
700 * The interrupt may not have descheduled.
8ec60c3f 701 */
85946b6c 702 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 703 need_lwkt_resched();
f9235b6d
MD
704 goto havethread_preempted;
705 }
706
b12defdc 707 /*
f9235b6d 708 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
709 * schedule the target thread.
710 *
711 * Reminder: Again, we cannot afford to run any IPIs in this path if
712 * the current thread has been descheduled.
f9235b6d
MD
713 */
714 for (;;) {
b12defdc 715 clear_lwkt_resched();
f9235b6d 716
4b5f931b 717 /*
2a418930 718 * Hotpath - pull the head of the run queue and attempt to schedule
85946b6c 719 * it.
41a01a4d 720 */
2a418930
MD
721 for (;;) {
722 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
723
724 if (ntd == NULL) {
725 /*
b12defdc 726 * Runq is empty, switch to idle to allow it to halt.
2a418930
MD
727 */
728 ntd = &gd->gd_idlethread;
6f207a2c 729#ifdef SMP
2a418930 730 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
b5d16701 731 ASSERT_NO_TOKENS_HELD(ntd);
6f207a2c 732#endif
2a418930
MD
733 cpu_time.cp_msg[0] = 0;
734 cpu_time.cp_stallpc = 0;
2a418930
MD
735 goto haveidle;
736 }
b12defdc 737 break;
f9235b6d 738 }
41a01a4d 739
8ec60c3f 740 /*
b12defdc 741 * Hotpath - schedule ntd.
6f207a2c
MD
742 *
743 * NOTE: For UP there is no mplock and lwkt_getalltokens()
744 * always succeeds.
8ec60c3f 745 */
b12defdc
MD
746 if (TD_TOKS_NOT_HELD(ntd) ||
747 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops)))
748 {
f9235b6d 749 goto havethread;
b12defdc 750 }
f9235b6d 751
f9235b6d 752 /*
2a418930
MD
753 * Coldpath (SMP only since tokens always succeed on UP)
754 *
755 * We had some contention on the thread we wanted to schedule.
756 * What we do now is try to find a thread that we can schedule
b12defdc 757 * in its stead.
2a418930 758 *
85946b6c
MD
759 * The coldpath scan does NOT rearrange threads in the run list.
760 * The lwkt_schedulerclock() will assert need_lwkt_resched() on
761 * the next tick whenever the current head is not the current thread.
f9235b6d 762 */
b12defdc 763#ifdef INVARIANTS
85946b6c
MD
764 ++token_contention_count[ntd->td_pri];
765 ++ntd->td_contended;
b12defdc
MD
766#endif
767
85946b6c 768 if (fairq_bypass > 0)
b12defdc
MD
769 goto skip;
770
b12defdc
MD
771 xtd = NULL;
772 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
85946b6c
MD
773 /*
774 * Never schedule threads returning to userland or the
775 * user thread scheduler helper thread when higher priority
776 * threads are present.
777 */
778 if (ntd->td_pri < TDPRI_KERN_LPSCHED) {
779 ntd = NULL;
780 break;
781 }
782
783 /*
784 * Try this one.
785 */
b12defdc
MD
786 if (TD_TOKS_NOT_HELD(ntd) ||
787 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) {
788 goto havethread;
789 }
85946b6c
MD
790#ifdef INVARIANTS
791 ++token_contention_count[ntd->td_pri];
792 ++ntd->td_contended;
b12defdc 793#endif
2a418930
MD
794 }
795
b12defdc 796skip:
2a418930
MD
797 /*
798 * We exhausted the run list, meaning that all runnable threads
b12defdc 799 * are contested.
2a418930
MD
800 */
801 cpu_pause();
802 ntd = &gd->gd_idlethread;
803#ifdef SMP
804 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
805 ASSERT_NO_TOKENS_HELD(ntd);
806 /* contention case, do not clear contention mask */
807#endif
808
809 /*
b12defdc
MD
810 * We are going to have to retry but if the current thread is not
811 * on the runq we instead switch through the idle thread to get away
812 * from the current thread. We have to flag for lwkt reschedule
813 * to prevent the idle thread from halting.
2a418930 814 *
b12defdc
MD
815 * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to
816 * instruct it to deal with the potential for deadlocks by
817 * ordering the tokens by address.
2a418930 818 */
b12defdc 819 if ((td->td_flags & TDF_RUNQ) == 0) {
85946b6c 820 need_lwkt_resched(); /* prevent hlt */
2a418930 821 goto haveidle;
4b5f931b 822 }
bd52bedf 823#if defined(INVARIANTS) && defined(__amd64__)
d5b2d319
MD
824 if ((read_rflags() & PSL_I) == 0) {
825 cpu_enable_intr();
826 panic("lwkt_switch() called with interrupts disabled");
827 }
828#endif
b12defdc
MD
829
830 /*
831 * Number iterations so far. After a certain point we switch to
832 * a sorted-address/monitor/mwait version of lwkt_getalltokens()
833 */
834 if (spinning < 0x7FFFFFFF)
835 ++spinning;
836
837#ifdef SMP
838 /*
839 * lwkt_getalltokens() failed in sorted token mode, we can use
840 * monitor/mwait in this case.
841 */
842 if (spinning >= lwkt_spin_loops &&
843 (cpu_mi_feature & CPU_MI_MONITOR) &&
844 lwkt_spin_monitor)
845 {
846 cpu_mmw_pause_int(&gd->gd_reqflags,
847 (gd->gd_reqflags | RQF_SPINNING) &
848 ~RQF_IDLECHECK_WK_MASK);
849 }
850#endif
851
852 /*
853 * We already checked that td is still scheduled so this should be
854 * safe.
855 */
856 splz_check();
857
858 /*
859 * This experimental resequencer is used as a fall-back to reduce
860 * hw cache line contention by placing each core's scheduler into a
861 * time-domain-multplexed slot.
862 *
863 * The resequencer is disabled by default. It's functionality has
864 * largely been superceeded by the token algorithm which limits races
865 * to a subset of cores.
866 *
867 * The resequencer algorithm tends to break down when more than
868 * 20 cores are contending. What appears to happen is that new
869 * tokens can be obtained out of address-sorted order by new cores
870 * while existing cores languish in long delays between retries and
871 * wind up being starved-out of the token acquisition.
872 */
873 if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) {
874 int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
875 int oseq;
876
877 while ((oseq = lwkt_cseq_rindex) != cseq) {
878 cpu_ccfence();
879#if 1
880 if (cpu_mi_feature & CPU_MI_MONITOR) {
881 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq);
882 } else {
883#endif
884 cpu_pause();
885 cpu_lfence();
886#if 1
887 }
8b402283 888#endif
0f0466c0 889 }
b12defdc
MD
890 DELAY(1);
891 atomic_add_int(&lwkt_cseq_rindex, 1);
2a418930 892 }
2a418930 893 /* highest level for(;;) loop */
f1d1c3fa 894 }
8a8d5d85 895
2a418930 896havethread:
b12defdc 897 /*
be71787b
MD
898 * Clear gd_idle_repeat when doing a normal switch to a non-idle
899 * thread.
f9235b6d 900 */
9ac1ee6e 901 ntd->td_wmesg = NULL;
b12defdc 902 ++gd->gd_cnt.v_swtch;
be71787b 903 gd->gd_idle_repeat = 0;
2a418930 904
f9235b6d 905havethread_preempted:
f9235b6d
MD
906 /*
907 * If the new target does not need the MP lock and we are holding it,
908 * release the MP lock. If the new target requires the MP lock we have
909 * already acquired it for the target.
8a8d5d85 910 */
2a418930 911 ;
f9235b6d
MD
912haveidle:
913 KASSERT(ntd->td_critcount,
b5d16701
MD
914 ("priority problem in lwkt_switch %d %d",
915 td->td_critcount, ntd->td_critcount));
916
94f6d86e 917 if (td != ntd) {
cc9b6223
MD
918 /*
919 * Execute the actual thread switch operation. This function
920 * returns to the current thread and returns the previous thread
921 * (which may be different from the thread we switched to).
922 *
923 * We are responsible for marking ntd as TDF_RUNNING.
924 */
94f6d86e 925 ++switch_count;
a1f0fb66 926 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
927 ntd->td_flags |= TDF_RUNNING;
928 lwkt_switch_return(td->td_switch(ntd));
929 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 930 }
b12defdc 931
b12defdc 932 /*
54341a3b 933 * catch-all. XXX is this strictly needed?
b12defdc
MD
934 */
935 splz_check();
54341a3b 936
37af14fe
MD
937 /* NOTE: current cpu may have changed after switch */
938 crit_exit_quick(td);
8ad65e08
MD
939}
940
cc9b6223
MD
941/*
942 * Called by assembly in the td_switch (thread restore path) for thread
943 * bootstrap cases which do not 'return' to lwkt_switch().
944 */
945void
946lwkt_switch_return(thread_t otd)
947{
948#ifdef SMP
949 globaldata_t rgd;
950
951 /*
952 * Check if otd was migrating. Now that we are on ntd we can finish
953 * up the migration. This is a bit messy but it is the only place
954 * where td is known to be fully descheduled.
955 *
956 * We can only activate the migration if otd was migrating but not
957 * held on the cpu due to a preemption chain. We still have to
958 * clear TDF_RUNNING on the old thread either way.
959 *
960 * We are responsible for clearing the previously running thread's
961 * TDF_RUNNING.
962 */
963 if ((rgd = otd->td_migrate_gd) != NULL &&
964 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
965 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
966 (TDF_MIGRATING | TDF_RUNNING));
967 otd->td_migrate_gd = NULL;
968 otd->td_flags &= ~TDF_RUNNING;
969 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
970 } else {
971 otd->td_flags &= ~TDF_RUNNING;
972 }
973#else
974 otd->td_flags &= ~TDF_RUNNING;
975#endif
976}
977
b68b7282 978/*
96728c05 979 * Request that the target thread preempt the current thread. Preemption
54341a3b
MD
980 * can only occur if our only critical section is the one that we were called
981 * with, the relative priority of the target thread is higher, and the target
982 * thread holds no tokens. This also only works if we are not holding any
983 * spinlocks (obviously).
96728c05
MD
984 *
985 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
986 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 987 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
988 * to determine whether preemption is possible (aka usually just the crit
989 * priority of lwkt_schedule() itself).
b68b7282 990 *
54341a3b
MD
991 * Preemption is typically limited to interrupt threads.
992 *
993 * Operation works in a fairly straight-forward manner. The normal
994 * scheduling code is bypassed and we switch directly to the target
995 * thread. When the target thread attempts to block or switch away
996 * code at the base of lwkt_switch() will switch directly back to our
997 * thread. Our thread is able to retain whatever tokens it holds and
998 * if the target needs one of them the target will switch back to us
999 * and reschedule itself normally.
b68b7282
MD
1000 */
1001void
f9235b6d 1002lwkt_preempt(thread_t ntd, int critcount)
b68b7282 1003{
46a3f46d 1004 struct globaldata *gd = mycpu;
cc9b6223 1005 thread_t xtd;
0a3f9b47 1006 thread_t td;
2d910aaf 1007 int save_gd_intr_nesting_level;
b68b7282 1008
26a0694b 1009 /*
96728c05
MD
1010 * The caller has put us in a critical section. We can only preempt
1011 * if the caller of the caller was not in a critical section (basically
f9235b6d 1012 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 1013 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 1014 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
1015 *
1016 * YYY The target thread must be in a critical section (else it must
1017 * inherit our critical section? I dunno yet).
26a0694b 1018 */
f9235b6d 1019 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 1020
b12defdc 1021 td = gd->gd_curthread;
fbc024e4
MD
1022 if (preempt_enable == 0) {
1023 ++preempt_miss;
1024 return;
1025 }
f9235b6d 1026 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
1027 ++preempt_miss;
1028 return;
1029 }
f9235b6d 1030 if (td->td_critcount > critcount) {
96728c05
MD
1031 ++preempt_miss;
1032 return;
1033 }
1034#ifdef SMP
46a3f46d 1035 if (ntd->td_gd != gd) {
96728c05
MD
1036 ++preempt_miss;
1037 return;
1038 }
1039#endif
41a01a4d 1040 /*
77912481
MD
1041 * We don't have to check spinlocks here as they will also bump
1042 * td_critcount.
d3d1cbc8
MD
1043 *
1044 * Do not try to preempt if the target thread is holding any tokens.
1045 * We could try to acquire the tokens but this case is so rare there
1046 * is no need to support it.
41a01a4d 1047 */
77912481
MD
1048 KKASSERT(gd->gd_spinlocks_wr == 0);
1049
3b998fa9 1050 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 1051 ++preempt_miss;
d3d1cbc8
MD
1052 return;
1053 }
26a0694b
MD
1054 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1055 ++preempt_weird;
1056 return;
1057 }
1058 if (ntd->td_preempted) {
4b5f931b 1059 ++preempt_hit;
26a0694b 1060 return;
b68b7282 1061 }
da0b0e8b 1062 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1063
8ec60c3f
MD
1064 /*
1065 * Since we are able to preempt the current thread, there is no need to
1066 * call need_lwkt_resched().
2d910aaf
MD
1067 *
1068 * We must temporarily clear gd_intr_nesting_level around the switch
1069 * since switchouts from the target thread are allowed (they will just
1070 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1071 *
1072 * A preemption must switch back to the original thread, assert the
1073 * case.
8ec60c3f 1074 */
26a0694b
MD
1075 ++preempt_hit;
1076 ntd->td_preempted = td;
1077 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1078 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1079 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1080 gd->gd_intr_nesting_level = 0;
cc9b6223
MD
1081 ntd->td_flags |= TDF_RUNNING;
1082 xtd = td->td_switch(ntd);
1083 KKASSERT(xtd == ntd);
1084 lwkt_switch_return(xtd);
2d910aaf 1085 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1086
26a0694b
MD
1087 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1088 ntd->td_preempted = NULL;
1089 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1090}
1091
f1d1c3fa 1092/*
faaeffac 1093 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1094 * This will work inside a critical section but not inside a hard code
1095 * section.
ef0fdad1 1096 *
f1d1c3fa
MD
1097 * (self contained on a per cpu basis)
1098 */
1099void
faaeffac 1100splz_check(void)
f1d1c3fa 1101{
7966cb69
MD
1102 globaldata_t gd = mycpu;
1103 thread_t td = gd->gd_curthread;
ef0fdad1 1104
4a28fe22
MD
1105 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1106 gd->gd_intr_nesting_level == 0 &&
1107 td->td_nest_count < 2)
1108 {
f1d1c3fa 1109 splz();
4a28fe22
MD
1110 }
1111}
1112
1113/*
1114 * This version is integrated into crit_exit, reqflags has already
1115 * been tested but td_critcount has not.
1116 *
1117 * We only want to execute the splz() on the 1->0 transition of
1118 * critcount and not in a hard code section or if too deeply nested.
1119 */
1120void
1121lwkt_maybe_splz(thread_t td)
1122{
1123 globaldata_t gd = td->td_gd;
1124
1125 if (td->td_critcount == 0 &&
1126 gd->gd_intr_nesting_level == 0 &&
1127 td->td_nest_count < 2)
1128 {
1129 splz();
1130 }
f1d1c3fa
MD
1131}
1132
e6546af9
MD
1133/*
1134 * Drivers which set up processing co-threads can call this function to
1135 * run the co-thread at a higher priority and to allow it to preempt
1136 * normal threads.
1137 */
1138void
1139lwkt_set_interrupt_support_thread(void)
1140{
1141 thread_t td = curthread;
1142
1143 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1144 td->td_flags |= TDF_INTTHREAD;
1145 td->td_preemptable = lwkt_preempt;
1146}
1147
1148
8ad65e08 1149/*
f9235b6d
MD
1150 * This function is used to negotiate a passive release of the current
1151 * process/lwp designation with the user scheduler, allowing the user
1152 * scheduler to schedule another user thread. The related kernel thread
1153 * (curthread) continues running in the released state.
8ad65e08
MD
1154 */
1155void
f9235b6d 1156lwkt_passive_release(struct thread *td)
8ad65e08 1157{
f9235b6d
MD
1158 struct lwp *lp = td->td_lwp;
1159
1160 td->td_release = NULL;
1161 lwkt_setpri_self(TDPRI_KERN_USER);
1162 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1163}
1164
f9235b6d 1165
3824f392 1166/*
d2d8515b
MD
1167 * This implements a LWKT yield, allowing a kernel thread to yield to other
1168 * kernel threads at the same or higher priority. This function can be
1169 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1170 *
d2d8515b
MD
1171 * Most kernel threads run at the same priority in order to allow equal
1172 * sharing.
f9235b6d
MD
1173 *
1174 * (self contained on a per cpu basis)
3824f392
MD
1175 */
1176void
f9235b6d 1177lwkt_yield(void)
3824f392 1178{
f9235b6d
MD
1179 globaldata_t gd = mycpu;
1180 thread_t td = gd->gd_curthread;
3824f392 1181
f9235b6d
MD
1182 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1183 splz();
85946b6c 1184 if (lwkt_resched_wanted()) {
f9235b6d
MD
1185 lwkt_schedule_self(curthread);
1186 lwkt_switch();
f9235b6d 1187 }
3824f392
MD
1188}
1189
1190/*
f9235b6d
MD
1191 * This yield is designed for kernel threads with a user context.
1192 *
1193 * The kernel acting on behalf of the user is potentially cpu-bound,
1194 * this function will efficiently allow other threads to run and also
1195 * switch to other processes by releasing.
3824f392
MD
1196 *
1197 * The lwkt_user_yield() function is designed to have very low overhead
1198 * if no yield is determined to be needed.
1199 */
1200void
1201lwkt_user_yield(void)
1202{
f9235b6d
MD
1203 globaldata_t gd = mycpu;
1204 thread_t td = gd->gd_curthread;
1205
1206 /*
1207 * Always run any pending interrupts in case we are in a critical
1208 * section.
1209 */
1210 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1211 splz();
3824f392 1212
3824f392 1213 /*
f9235b6d
MD
1214 * Switch (which forces a release) if another kernel thread needs
1215 * the cpu, if userland wants us to resched, or if our kernel
1216 * quantum has run out.
3824f392 1217 */
f9235b6d 1218 if (lwkt_resched_wanted() ||
85946b6c 1219 user_resched_wanted())
f9235b6d 1220 {
3824f392 1221 lwkt_switch();
3824f392
MD
1222 }
1223
f9235b6d 1224#if 0
3824f392 1225 /*
f9235b6d
MD
1226 * Reacquire the current process if we are released.
1227 *
1228 * XXX not implemented atm. The kernel may be holding locks and such,
1229 * so we want the thread to continue to receive cpu.
3824f392 1230 */
f9235b6d
MD
1231 if (td->td_release == NULL && lp) {
1232 lp->lwp_proc->p_usched->acquire_curproc(lp);
1233 td->td_release = lwkt_passive_release;
1234 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1235 }
f9235b6d 1236#endif
b9eb1c19
MD
1237}
1238
8ad65e08 1239/*
f1d1c3fa
MD
1240 * Generic schedule. Possibly schedule threads belonging to other cpus and
1241 * deal with threads that might be blocked on a wait queue.
1242 *
0a3f9b47
MD
1243 * We have a little helper inline function which does additional work after
1244 * the thread has been enqueued, including dealing with preemption and
1245 * setting need_lwkt_resched() (which prevents the kernel from returning
1246 * to userland until it has processed higher priority threads).
6330a558
MD
1247 *
1248 * It is possible for this routine to be called after a failed _enqueue
1249 * (due to the target thread migrating, sleeping, or otherwise blocked).
1250 * We have to check that the thread is actually on the run queue!
8ad65e08 1251 */
0a3f9b47
MD
1252static __inline
1253void
85946b6c 1254_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1255{
6330a558 1256 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1257 if (ntd->td_preemptable) {
f9235b6d 1258 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1259 }
0a3f9b47
MD
1260 }
1261}
1262
361d01dd 1263static __inline
8ad65e08 1264void
85946b6c 1265_lwkt_schedule(thread_t td)
8ad65e08 1266{
37af14fe
MD
1267 globaldata_t mygd = mycpu;
1268
cf709dd2
MD
1269 KASSERT(td != &td->td_gd->gd_idlethread,
1270 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1271 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1272 crit_enter_gd(mygd);
4643740a
MD
1273 KKASSERT(td->td_lwp == NULL ||
1274 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1275
37af14fe 1276 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1277 _lwkt_enqueue(td);
1278 } else {
f1d1c3fa 1279 /*
7cd8d145
MD
1280 * If we own the thread, there is no race (since we are in a
1281 * critical section). If we do not own the thread there might
1282 * be a race but the target cpu will deal with it.
f1d1c3fa 1283 */
0f7a3396 1284#ifdef SMP
7cd8d145 1285 if (td->td_gd == mygd) {
9d265729 1286 _lwkt_enqueue(td);
85946b6c 1287 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1288 } else {
e381e77c 1289 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1290 }
0f7a3396 1291#else
7cd8d145 1292 _lwkt_enqueue(td);
85946b6c 1293 _lwkt_schedule_post(mygd, td, 1);
0f7a3396 1294#endif
8ad65e08 1295 }
37af14fe 1296 crit_exit_gd(mygd);
8ad65e08
MD
1297}
1298
361d01dd
MD
1299void
1300lwkt_schedule(thread_t td)
1301{
85946b6c 1302 _lwkt_schedule(td);
361d01dd
MD
1303}
1304
1305void
85946b6c 1306lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1307{
85946b6c 1308 _lwkt_schedule(td);
361d01dd
MD
1309}
1310
88ebb169
SW
1311#ifdef SMP
1312
e381e77c
MD
1313/*
1314 * When scheduled remotely if frame != NULL the IPIQ is being
1315 * run via doreti or an interrupt then preemption can be allowed.
1316 *
1317 * To allow preemption we have to drop the critical section so only
1318 * one is present in _lwkt_schedule_post.
1319 */
1320static void
1321lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1322{
1323 thread_t td = curthread;
1324 thread_t ntd = arg;
1325
1326 if (frame && ntd->td_preemptable) {
1327 crit_exit_noyield(td);
85946b6c 1328 _lwkt_schedule(ntd);
e381e77c
MD
1329 crit_enter_quick(td);
1330 } else {
85946b6c 1331 _lwkt_schedule(ntd);
e381e77c
MD
1332 }
1333}
1334
d9eea1a5 1335/*
52eedfb5
MD
1336 * Thread migration using a 'Pull' method. The thread may or may not be
1337 * the current thread. It MUST be descheduled and in a stable state.
1338 * lwkt_giveaway() must be called on the cpu owning the thread.
1339 *
1340 * At any point after lwkt_giveaway() is called, the target cpu may
1341 * 'pull' the thread by calling lwkt_acquire().
1342 *
ae8e83e6
MD
1343 * We have to make sure the thread is not sitting on a per-cpu tsleep
1344 * queue or it will blow up when it moves to another cpu.
1345 *
52eedfb5 1346 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1347 */
52eedfb5
MD
1348void
1349lwkt_giveaway(thread_t td)
1350{
3b4192fb 1351 globaldata_t gd = mycpu;
52eedfb5 1352
3b4192fb
MD
1353 crit_enter_gd(gd);
1354 if (td->td_flags & TDF_TSLEEPQ)
1355 tsleep_remove(td);
1356 KKASSERT(td->td_gd == gd);
1357 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1358 td->td_flags |= TDF_MIGRATING;
1359 crit_exit_gd(gd);
52eedfb5
MD
1360}
1361
a2a5ad0d
MD
1362void
1363lwkt_acquire(thread_t td)
1364{
37af14fe
MD
1365 globaldata_t gd;
1366 globaldata_t mygd;
cc9b6223 1367 int retry = 10000000;
a2a5ad0d 1368
52eedfb5 1369 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1370 gd = td->td_gd;
37af14fe 1371 mygd = mycpu;
52eedfb5 1372 if (gd != mycpu) {
35238fa5 1373 cpu_lfence();
52eedfb5 1374 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1375 crit_enter_gd(mygd);
cfaeae2a 1376 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23
MD
1377 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1378#ifdef SMP
1379 lwkt_process_ipiq();
1380#endif
52eedfb5 1381 cpu_lfence();
cc9b6223
MD
1382 if (--retry == 0) {
1383 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1384 td, td->td_flags);
1385 retry = 10000000;
1386 }
df910c23 1387 }
cfaeae2a 1388 DEBUG_POP_INFO();
562273ea 1389 cpu_mfence();
37af14fe 1390 td->td_gd = mygd;
52eedfb5
MD
1391 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1392 td->td_flags &= ~TDF_MIGRATING;
1393 crit_exit_gd(mygd);
1394 } else {
1395 crit_enter_gd(mygd);
1396 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1397 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1398 crit_exit_gd(mygd);
a2a5ad0d
MD
1399 }
1400}
1401
52eedfb5
MD
1402#endif
1403
f1d1c3fa
MD
1404/*
1405 * Generic deschedule. Descheduling threads other then your own should be
1406 * done only in carefully controlled circumstances. Descheduling is
1407 * asynchronous.
1408 *
1409 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1410 */
1411void
1412lwkt_deschedule(thread_t td)
1413{
f1d1c3fa 1414 crit_enter();
b8a98473 1415#ifdef SMP
f1d1c3fa
MD
1416 if (td == curthread) {
1417 _lwkt_dequeue(td);
1418 } else {
a72187e9 1419 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1420 _lwkt_dequeue(td);
1421 } else {
b8a98473 1422 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1423 }
1424 }
b8a98473
MD
1425#else
1426 _lwkt_dequeue(td);
1427#endif
f1d1c3fa
MD
1428 crit_exit();
1429}
1430
4b5f931b
MD
1431/*
1432 * Set the target thread's priority. This routine does not automatically
1433 * switch to a higher priority thread, LWKT threads are not designed for
1434 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1435 */
1436void
1437lwkt_setpri(thread_t td, int pri)
1438{
f9235b6d
MD
1439 if (td->td_pri != pri) {
1440 KKASSERT(pri >= 0);
1441 crit_enter();
1442 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1443 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1444 _lwkt_dequeue(td);
1445 td->td_pri = pri;
1446 _lwkt_enqueue(td);
1447 } else {
1448 td->td_pri = pri;
1449 }
1450 crit_exit();
26a0694b 1451 }
26a0694b
MD
1452}
1453
03bd0a5e
MD
1454/*
1455 * Set the initial priority for a thread prior to it being scheduled for
1456 * the first time. The thread MUST NOT be scheduled before or during
1457 * this call. The thread may be assigned to a cpu other then the current
1458 * cpu.
1459 *
1460 * Typically used after a thread has been created with TDF_STOPPREQ,
1461 * and before the thread is initially scheduled.
1462 */
1463void
1464lwkt_setpri_initial(thread_t td, int pri)
1465{
1466 KKASSERT(pri >= 0);
1467 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1468 td->td_pri = pri;
03bd0a5e
MD
1469}
1470
26a0694b
MD
1471void
1472lwkt_setpri_self(int pri)
1473{
1474 thread_t td = curthread;
1475
4b5f931b
MD
1476 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1477 crit_enter();
1478 if (td->td_flags & TDF_RUNQ) {
1479 _lwkt_dequeue(td);
f9235b6d 1480 td->td_pri = pri;
4b5f931b
MD
1481 _lwkt_enqueue(td);
1482 } else {
f9235b6d 1483 td->td_pri = pri;
4b5f931b
MD
1484 }
1485 crit_exit();
1486}
1487
f9235b6d 1488/*
85946b6c 1489 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1490 */
1491void
85946b6c 1492lwkt_schedulerclock(thread_t td)
f9235b6d 1493{
85946b6c
MD
1494 globaldata_t gd = td->td_gd;
1495 thread_t xtd;
2a418930 1496
85946b6c
MD
1497 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1498 /*
1499 * If the current thread is at the head of the runq shift it to the
1500 * end of any equal-priority threads and request a LWKT reschedule
1501 * if it moved.
1502 */
1503 xtd = TAILQ_NEXT(td, td_threadq);
1504 if (xtd && xtd->td_pri == td->td_pri) {
1505 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1506 while (xtd && xtd->td_pri == td->td_pri)
1507 xtd = TAILQ_NEXT(xtd, td_threadq);
1508 if (xtd)
1509 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1510 else
1511 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1512 need_lwkt_resched();
f9235b6d 1513 }
85946b6c
MD
1514 } else {
1515 /*
1516 * If we scheduled a thread other than the one at the head of the
1517 * queue always request a reschedule every tick.
1518 */
1519 need_lwkt_resched();
f9235b6d
MD
1520 }
1521}
1522
5d21b981 1523/*
52eedfb5
MD
1524 * Migrate the current thread to the specified cpu.
1525 *
cc9b6223
MD
1526 * This is accomplished by descheduling ourselves from the current cpu
1527 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1528 * 'old' thread wants to migrate after it has been completely switched out
1529 * and will complete the migration.
1530 *
1531 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1532 *
1533 * We must be sure to release our current process designation (if a user
1534 * process) before clearing out any tsleepq we are on because the release
1535 * code may re-add us.
ae8e83e6
MD
1536 *
1537 * We must be sure to remove ourselves from the current cpu's tsleepq
1538 * before potentially moving to another queue. The thread can be on
1539 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1540 */
5d21b981
MD
1541
1542void
1543lwkt_setcpu_self(globaldata_t rgd)
1544{
1545#ifdef SMP
1546 thread_t td = curthread;
1547
1548 if (td->td_gd != rgd) {
1549 crit_enter_quick(td);
cc9b6223 1550
95858b91
MD
1551 if (td->td_release)
1552 td->td_release(td);
ae8e83e6 1553 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1554 tsleep_remove(td);
cc9b6223
MD
1555
1556 /*
1557 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1558 * trying to deschedule ourselves and switch away, then deschedule
1559 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1560 * call lwkt_switch() to complete the operation.
1561 */
5d21b981
MD
1562 td->td_flags |= TDF_MIGRATING;
1563 lwkt_deschedule_self(td);
52eedfb5 1564 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1565 td->td_migrate_gd = rgd;
5d21b981 1566 lwkt_switch();
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1567
1568 /*
1569 * We are now on the target cpu
1570 */
1571 KKASSERT(rgd == mycpu);
52eedfb5 1572 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
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1573 crit_exit_quick(td);
1574 }
1575#endif
1576}
1577
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1578void
1579lwkt_migratecpu(int cpuid)
1580{
1581#ifdef SMP
1582 globaldata_t rgd;
1583
1584 rgd = globaldata_find(cpuid);
1585 lwkt_setcpu_self(rgd);
1586#endif
1587}
1588
cc9b6223 1589#ifdef SMP
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1590/*
1591 * Remote IPI for cpu migration (called while in a critical section so we
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1592 * do not have to enter another one).
1593 *
1594 * The thread (td) has already been completely descheduled from the
1595 * originating cpu and we can simply assert the case. The thread is
1596 * assigned to the new cpu and enqueued.
5d21b981 1597 *
cc9b6223 1598 * The thread will re-add itself to tdallq when it resumes execution.
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1599 */
1600static void
1601lwkt_setcpu_remote(void *arg)
1602{
1603 thread_t td = arg;
1604 globaldata_t gd = mycpu;
1605
cc9b6223 1606 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1607 td->td_gd = gd;
562273ea 1608 cpu_mfence();
5d21b981 1609 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1610 KKASSERT(td->td_migrate_gd == NULL);
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1611 KKASSERT(td->td_lwp == NULL ||
1612 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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1613 _lwkt_enqueue(td);
1614}
3d28ff59 1615#endif
5d21b981 1616
553ea3c8 1617struct lwp *
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1618lwkt_preempted_proc(void)
1619{
73e4f7b9 1620 thread_t td = curthread;
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1621 while (td->td_preempted)
1622 td = td->td_preempted;
553ea3c8 1623 return(td->td_lwp);
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1624}
1625
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1626/*
1627 * Create a kernel process/thread/whatever. It shares it's address space
1628 * with proc0 - ie: kernel only.
1629 *
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1630 * If the cpu is not specified one will be selected. In the future
1631 * specifying a cpu of -1 will enable kernel thread migration between
1632 * cpus.
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1633 */
1634int
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1635lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1636 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1637{
73e4f7b9 1638 thread_t td;
e2565a42 1639 __va_list ap;
99df837e 1640
d3d32139 1641 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1642 tdflags);
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1643 if (tdp)
1644 *tdp = td;
709799ea 1645 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1646
1647 /*
1648 * Set up arg0 for 'ps' etc
1649 */
e2565a42 1650 __va_start(ap, fmt);
379210cb 1651 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1652 __va_end(ap);
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1653
1654 /*
1655 * Schedule the thread to run
1656 */
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1657 if (td->td_flags & TDF_NOSTART)
1658 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1659 else
4643740a 1660 lwkt_schedule(td);
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1661 return 0;
1662}
1663
1664/*
1665 * Destroy an LWKT thread. Warning! This function is not called when
1666 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1667 * uses a different reaping mechanism.
1668 */
1669void
1670lwkt_exit(void)
1671{
1672 thread_t td = curthread;
c070746a 1673 thread_t std;
8826f33a 1674 globaldata_t gd;
99df837e 1675
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1676 /*
1677 * Do any cleanup that might block here
1678 */
99df837e 1679 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1680 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1681 caps_exit(td);
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1682 biosched_done(td);
1683 dsched_exit_thread(td);
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1684
1685 /*
1686 * Get us into a critical section to interlock gd_freetd and loop
1687 * until we can get it freed.
1688 *
1689 * We have to cache the current td in gd_freetd because objcache_put()ing
1690 * it would rip it out from under us while our thread is still active.
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1691 *
1692 * We are the current thread so of course our own TDF_RUNNING bit will
1693 * be set, so unlike the lwp reap code we don't wait for it to clear.
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1694 */
1695 gd = mycpu;
37af14fe 1696 crit_enter_quick(td);
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1697 for (;;) {
1698 if (td->td_refs) {
1699 tsleep(td, 0, "tdreap", 1);
1700 continue;
1701 }
1702 if ((std = gd->gd_freetd) != NULL) {
1703 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1704 gd->gd_freetd = NULL;
1705 objcache_put(thread_cache, std);
1706 continue;
1707 }
1708 break;
c070746a 1709 }
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1710
1711 /*
1712 * Remove thread resources from kernel lists and deschedule us for
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1713 * the last time. We cannot block after this point or we may end
1714 * up with a stale td on the tsleepq.
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1715 *
1716 * None of this may block, the critical section is the only thing
1717 * protecting tdallq and the only thing preventing new lwkt_hold()
1718 * thread refs now.
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1719 */
1720 if (td->td_flags & TDF_TSLEEPQ)
1721 tsleep_remove(td);
37af14fe 1722 lwkt_deschedule_self(td);
e56e4dea 1723 lwkt_remove_tdallq(td);
74c9628e 1724 KKASSERT(td->td_refs == 0);
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1725
1726 /*
1727 * Final cleanup
1728 */
1729 KKASSERT(gd->gd_freetd == NULL);
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1730 if (td->td_flags & TDF_ALLOCATED_THREAD)
1731 gd->gd_freetd = td;
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1732 cpu_thread_exit();
1733}
1734
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1735void
1736lwkt_remove_tdallq(thread_t td)
1737{
1738 KKASSERT(td->td_gd == mycpu);
1739 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1740}
1741
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1742/*
1743 * Code reduction and branch prediction improvements. Call/return
1744 * overhead on modern cpus often degenerates into 0 cycles due to
1745 * the cpu's branch prediction hardware and return pc cache. We
1746 * can take advantage of this by not inlining medium-complexity
1747 * functions and we can also reduce the branch prediction impact
1748 * by collapsing perfectly predictable branches into a single
1749 * procedure instead of duplicating it.
1750 *
1751 * Is any of this noticeable? Probably not, so I'll take the
1752 * smaller code size.
1753 */
1754void
b6468f56 1755crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1756{
b6468f56 1757 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1758}
1759
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1760void
1761crit_panic(void)
1762{
1763 thread_t td = curthread;
850634cc 1764 int lcrit = td->td_critcount;
2d93b37a 1765
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1766 td->td_critcount = 0;
1767 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1768 /* NOT REACHED */
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1769}
1770
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1771#ifdef SMP
1772
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1773/*
1774 * Called from debugger/panic on cpus which have been stopped. We must still
1775 * process the IPIQ while stopped, even if we were stopped while in a critical
1776 * section (XXX).
1777 *
1778 * If we are dumping also try to process any pending interrupts. This may
1779 * or may not work depending on the state of the cpu at the point it was
1780 * stopped.
1781 */
1782void
1783lwkt_smp_stopped(void)
1784{
1785 globaldata_t gd = mycpu;
1786
1787 crit_enter_gd(gd);
1788 if (dumping) {
1789 lwkt_process_ipiq();
1790 splz();
1791 } else {
1792 lwkt_process_ipiq();
1793 }
1794 crit_exit_gd(gd);
1795}
1796
d165e668 1797#endif