kernel - add lwkt_set_interrupt_support_thread() API
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
b12defdc 2 * Copyright (c) 2003-2011 The DragonFly Project. All rights reserved.
60f60350 3 *
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4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
60f60350 6 *
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7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
60f60350 10 *
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11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
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14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
60f60350 20 *
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21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
8ad65e08 32 * SUCH DAMAGE.
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33 */
34
35/*
36 * Each cpu in a system has its own self-contained light weight kernel
37 * thread scheduler, which means that generally speaking we only need
38 * to use a critical section to avoid problems. Foreign thread
39 * scheduling is queued via (async) IPIs.
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40 */
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/kernel.h>
45#include <sys/proc.h>
46#include <sys/rtprio.h>
b37f18d6 47#include <sys/kinfo.h>
8ad65e08 48#include <sys/queue.h>
7d0bac62 49#include <sys/sysctl.h>
99df837e 50#include <sys/kthread.h>
f1d1c3fa 51#include <machine/cpu.h>
99df837e 52#include <sys/lock.h>
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
8c72e3d5
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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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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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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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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();
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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;
294 return (1);
295}
296
297static void
298_lwkt_thread_dtor(void *obj, void *privdata)
299{
300 struct thread *td = (struct thread *)obj;
301
302 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
303 ("_lwkt_thread_dtor: not allocated from objcache"));
304 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
305 td->td_kstack_size > 0,
306 ("_lwkt_thread_dtor: corrupted stack"));
307 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
308}
309
310/*
311 * Initialize the lwkt s/system.
765b1ae0
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312 *
313 * Nominally cache up to 32 thread + kstack structures.
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314 */
315void
316lwkt_init(void)
317{
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318 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
319 thread_cache = objcache_create_mbacked(
320 M_THREAD, sizeof(struct thread),
321 NULL, lwkt_cache_threads,
322 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
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NT
323}
324
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325/*
326 * Schedule a thread to run. As the current thread we can always safely
327 * schedule ourselves, and a shortcut procedure is provided for that
328 * function.
329 *
330 * (non-blocking, self contained on a per cpu basis)
331 */
332void
333lwkt_schedule_self(thread_t td)
334{
cfaeae2a 335 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 336 crit_enter_quick(td);
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MD
337 KASSERT(td != &td->td_gd->gd_idlethread,
338 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
9388413d 339 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 340 _lwkt_enqueue(td);
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341 crit_exit_quick(td);
342}
343
344/*
345 * Deschedule a thread.
346 *
347 * (non-blocking, self contained on a per cpu basis)
348 */
349void
350lwkt_deschedule_self(thread_t td)
351{
352 crit_enter_quick(td);
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353 _lwkt_dequeue(td);
354 crit_exit_quick(td);
355}
356
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357/*
358 * LWKTs operate on a per-cpu basis
359 *
73e4f7b9 360 * WARNING! Called from early boot, 'mycpu' may not work yet.
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361 */
362void
363lwkt_gdinit(struct globaldata *gd)
364{
f9235b6d 365 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 366 TAILQ_INIT(&gd->gd_tdallq);
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367}
368
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369/*
370 * Create a new thread. The thread must be associated with a process context
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371 * or LWKT start address before it can be scheduled. If the target cpu is
372 * -1 the thread will be created on the current cpu.
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373 *
374 * If you intend to create a thread without a process context this function
375 * does everything except load the startup and switcher function.
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376 */
377thread_t
d3d32139 378lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 379{
d2d8515b 380 static int cpu_rotator;
c070746a 381 globaldata_t gd = mycpu;
99df837e 382 void *stack;
7d0bac62 383
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384 /*
385 * If static thread storage is not supplied allocate a thread. Reuse
386 * a cached free thread if possible. gd_freetd is used to keep an exiting
387 * thread intact through the exit.
388 */
ef0fdad1 389 if (td == NULL) {
cf709dd2
MD
390 crit_enter_gd(gd);
391 if ((td = gd->gd_freetd) != NULL) {
392 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
393 TDF_RUNQ)) == 0);
c070746a 394 gd->gd_freetd = NULL;
cf709dd2 395 } else {
c070746a 396 td = objcache_get(thread_cache, M_WAITOK);
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397 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
398 TDF_RUNQ)) == 0);
399 }
400 crit_exit_gd(gd);
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401 KASSERT((td->td_flags &
402 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD,
403 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
404 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 405 }
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406
407 /*
408 * Try to reuse cached stack.
409 */
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410 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
411 if (flags & TDF_ALLOCATED_STACK) {
e4846942 412 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
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413 stack = NULL;
414 }
415 }
416 if (stack == NULL) {
e40cfbd7 417 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 418 flags |= TDF_ALLOCATED_STACK;
99df837e 419 }
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MD
420 if (cpu < 0) {
421 cpu = ++cpu_rotator;
422 cpu_ccfence();
423 cpu %= ncpus;
424 }
425 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 426 return(td);
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427}
428
429/*
430 * Initialize a preexisting thread structure. This function is used by
431 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
432 *
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433 * All threads start out in a critical section at a priority of
434 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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435 * appropriate. This function may send an IPI message when the
436 * requested cpu is not the current cpu and consequently gd_tdallq may
437 * not be initialized synchronously from the point of view of the originating
438 * cpu.
439 *
440 * NOTE! we have to be careful in regards to creating threads for other cpus
441 * if SMP has not yet been activated.
7d0bac62 442 */
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443#ifdef SMP
444
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445static void
446lwkt_init_thread_remote(void *arg)
447{
448 thread_t td = arg;
449
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450 /*
451 * Protected by critical section held by IPI dispatch
452 */
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453 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
454}
455
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456#endif
457
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458/*
459 * lwkt core thread structural initialization.
460 *
461 * NOTE: All threads are initialized as mpsafe threads.
462 */
7d0bac62 463void
f470d0c8
MD
464lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
465 struct globaldata *gd)
7d0bac62 466{
37af14fe
MD
467 globaldata_t mygd = mycpu;
468
99df837e
MD
469 bzero(td, sizeof(struct thread));
470 td->td_kstack = stack;
f470d0c8 471 td->td_kstack_size = stksize;
d3d32139 472 td->td_flags = flags;
26a0694b 473 td->td_gd = gd;
f9235b6d
MD
474 td->td_pri = TDPRI_KERN_DAEMON;
475 td->td_critcount = 1;
3b998fa9 476 td->td_toks_stop = &td->td_toks_base;
fb0f29c4
MD
477 if (lwkt_use_spin_port)
478 lwkt_initport_spin(&td->td_msgport);
479 else
480 lwkt_initport_thread(&td->td_msgport, td);
99df837e 481 pmap_init_thread(td);
0f7a3396 482#ifdef SMP
5d21b981
MD
483 /*
484 * Normally initializing a thread for a remote cpu requires sending an
485 * IPI. However, the idlethread is setup before the other cpus are
486 * activated so we have to treat it as a special case. XXX manipulation
487 * of gd_tdallq requires the BGL.
488 */
489 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 490 crit_enter_gd(mygd);
75cdbe6c 491 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 492 crit_exit_gd(mygd);
75cdbe6c 493 } else {
2db3b277 494 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 495 }
0f7a3396 496#else
37af14fe 497 crit_enter_gd(mygd);
0f7a3396 498 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 499 crit_exit_gd(mygd);
0f7a3396 500#endif
8c72e3d5
AH
501
502 dsched_new_thread(td);
73e4f7b9
MD
503}
504
505void
506lwkt_set_comm(thread_t td, const char *ctl, ...)
507{
e2565a42 508 __va_list va;
73e4f7b9 509
e2565a42 510 __va_start(va, ctl);
379210cb 511 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 512 __va_end(va);
e7c0dbba 513 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]);
7d0bac62
MD
514}
515
99df837e 516void
73e4f7b9 517lwkt_hold(thread_t td)
99df837e 518{
74c9628e 519 atomic_add_int(&td->td_refs, 1);
73e4f7b9
MD
520}
521
522void
523lwkt_rele(thread_t td)
524{
525 KKASSERT(td->td_refs > 0);
74c9628e 526 atomic_add_int(&td->td_refs, -1);
73e4f7b9
MD
527}
528
529void
530lwkt_wait_free(thread_t td)
531{
532 while (td->td_refs)
377d4740 533 tsleep(td, 0, "tdreap", hz);
73e4f7b9
MD
534}
535
536void
537lwkt_free_thread(thread_t td)
538{
74c9628e 539 KKASSERT(td->td_refs == 0);
cf709dd2 540 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|TDF_RUNQ)) == 0);
40aaf5fc
NT
541 if (td->td_flags & TDF_ALLOCATED_THREAD) {
542 objcache_put(thread_cache, td);
543 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
544 /* client-allocated struct with internally allocated stack */
545 KASSERT(td->td_kstack && td->td_kstack_size > 0,
546 ("lwkt_free_thread: corrupted stack"));
547 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
548 td->td_kstack = NULL;
549 td->td_kstack_size = 0;
99df837e 550 }
e7c0dbba 551 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
552}
553
554
8ad65e08
MD
555/*
556 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
557 * switch to the idlethread. Switching must occur within a critical
558 * section to avoid races with the scheduling queue.
559 *
560 * We always have full control over our cpu's run queue. Other cpus
561 * that wish to manipulate our queue must use the cpu_*msg() calls to
562 * talk to our cpu, so a critical section is all that is needed and
563 * the result is very, very fast thread switching.
564 *
96728c05
MD
565 * The LWKT scheduler uses a fixed priority model and round-robins at
566 * each priority level. User process scheduling is a totally
567 * different beast and LWKT priorities should not be confused with
568 * user process priorities.
f1d1c3fa 569 *
69d78e99
MD
570 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
571 * is not called by the current thread in the preemption case, only when
572 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
573 *
574 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
575 * migration and tsleep deschedule the current lwkt thread and call
576 * lwkt_switch(). In particular, the target cpu of the migration fully
577 * expects the thread to become non-runnable and can deadlock against
578 * cpusync operations if we run any IPIs prior to switching the thread out.
579 *
580 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 581 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
582 */
583void
584lwkt_switch(void)
585{
37af14fe
MD
586 globaldata_t gd = mycpu;
587 thread_t td = gd->gd_curthread;
8ad65e08 588 thread_t ntd;
f9235b6d 589 thread_t xtd;
b12defdc 590 int spinning = 0;
8ad65e08 591
da0b0e8b
MD
592 KKASSERT(gd->gd_processing_ipiq == 0);
593
46a3f46d 594 /*
27e88a6e
MD
595 * Switching from within a 'fast' (non thread switched) interrupt or IPI
596 * is illegal. However, we may have to do it anyway if we hit a fatal
597 * kernel trap or we have paniced.
598 *
599 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 600 */
27e88a6e
MD
601 if (gd->gd_intr_nesting_level) {
602 int savegdnest;
603 int savegdtrap;
604
5fddbda2 605 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22
MD
606 panic("lwkt_switch: Attempt to switch from a "
607 "a fast interrupt, ipi, or hard code section, "
608 "td %p\n",
609 td);
27e88a6e
MD
610 } else {
611 savegdnest = gd->gd_intr_nesting_level;
612 savegdtrap = gd->gd_trap_nesting_level;
613 gd->gd_intr_nesting_level = 0;
614 gd->gd_trap_nesting_level = 0;
a7422615
MD
615 if ((td->td_flags & TDF_PANICWARN) == 0) {
616 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
617 kprintf("Warning: thread switch from interrupt, IPI, "
618 "or hard code section.\n"
a7422615 619 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 620 print_backtrace(-1);
a7422615 621 }
27e88a6e
MD
622 lwkt_switch();
623 gd->gd_intr_nesting_level = savegdnest;
624 gd->gd_trap_nesting_level = savegdtrap;
625 return;
626 }
96728c05 627 }
ef0fdad1 628
cb973d15 629 /*
85946b6c
MD
630 * Release our current user process designation if we are blocking
631 * or if a user reschedule was requested.
632 *
633 * NOTE: This function is NOT called if we are switching into or
634 * returning from a preemption.
635 *
636 * NOTE: Releasing our current user process designation may cause
637 * it to be assigned to another thread, which in turn will
638 * cause us to block in the usched acquire code when we attempt
639 * to return to userland.
640 *
641 * NOTE: On SMP systems this can be very nasty when heavy token
642 * contention is present so we want to be careful not to
643 * release the designation gratuitously.
cb973d15 644 */
85946b6c
MD
645 if (td->td_release &&
646 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 647 td->td_release(td);
85946b6c 648 }
cb973d15 649
85946b6c
MD
650 /*
651 * Release all tokens
652 */
37af14fe 653 crit_enter_gd(gd);
3b998fa9 654 if (TD_TOKS_HELD(td))
9d265729
MD
655 lwkt_relalltokens(td);
656
657 /*
b02926de
MD
658 * We had better not be holding any spin locks, but don't get into an
659 * endless panic loop.
9d265729 660 */
d666840a
MD
661 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
662 ("lwkt_switch: still holding %d exclusive spinlocks!",
663 gd->gd_spinlocks_wr));
9d265729 664
8a8d5d85
MD
665
666#ifdef SMP
0f7a3396
MD
667#ifdef INVARIANTS
668 if (td->td_cscount) {
6ea70f76 669 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
670 td);
671 if (panic_on_cscount)
672 panic("switching while mastering cpusync");
673 }
674#endif
8a8d5d85 675#endif
f9235b6d
MD
676
677 /*
678 * If we had preempted another thread on this cpu, resume the preempted
679 * thread. This occurs transparently, whether the preempted thread
680 * was scheduled or not (it may have been preempted after descheduling
681 * itself).
682 *
683 * We have to setup the MP lock for the original thread after backing
684 * out the adjustment that was made to curthread when the original
685 * was preempted.
686 */
99df837e 687 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
688 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
689 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
690
691 /*
b9eb1c19
MD
692 * The interrupt may have woken a thread up, we need to properly
693 * set the reschedule flag if the originally interrupted thread is
694 * at a lower priority.
85946b6c
MD
695 *
696 * The interrupt may not have descheduled.
8ec60c3f 697 */
85946b6c 698 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 699 need_lwkt_resched();
f9235b6d
MD
700 goto havethread_preempted;
701 }
702
b12defdc 703 /*
f9235b6d 704 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
705 * schedule the target thread.
706 *
707 * Reminder: Again, we cannot afford to run any IPIs in this path if
708 * the current thread has been descheduled.
f9235b6d
MD
709 */
710 for (;;) {
b12defdc 711 clear_lwkt_resched();
f9235b6d 712
4b5f931b 713 /*
2a418930 714 * Hotpath - pull the head of the run queue and attempt to schedule
85946b6c 715 * it.
41a01a4d 716 */
2a418930
MD
717 for (;;) {
718 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
719
720 if (ntd == NULL) {
721 /*
b12defdc 722 * Runq is empty, switch to idle to allow it to halt.
2a418930
MD
723 */
724 ntd = &gd->gd_idlethread;
6f207a2c 725#ifdef SMP
2a418930 726 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
b5d16701 727 ASSERT_NO_TOKENS_HELD(ntd);
6f207a2c 728#endif
2a418930
MD
729 cpu_time.cp_msg[0] = 0;
730 cpu_time.cp_stallpc = 0;
2a418930
MD
731 goto haveidle;
732 }
b12defdc 733 break;
f9235b6d 734 }
41a01a4d 735
8ec60c3f 736 /*
b12defdc 737 * Hotpath - schedule ntd.
6f207a2c
MD
738 *
739 * NOTE: For UP there is no mplock and lwkt_getalltokens()
740 * always succeeds.
8ec60c3f 741 */
b12defdc
MD
742 if (TD_TOKS_NOT_HELD(ntd) ||
743 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops)))
744 {
f9235b6d 745 goto havethread;
b12defdc 746 }
f9235b6d 747
f9235b6d 748 /*
2a418930
MD
749 * Coldpath (SMP only since tokens always succeed on UP)
750 *
751 * We had some contention on the thread we wanted to schedule.
752 * What we do now is try to find a thread that we can schedule
b12defdc 753 * in its stead.
2a418930 754 *
85946b6c
MD
755 * The coldpath scan does NOT rearrange threads in the run list.
756 * The lwkt_schedulerclock() will assert need_lwkt_resched() on
757 * the next tick whenever the current head is not the current thread.
f9235b6d 758 */
b12defdc 759#ifdef INVARIANTS
85946b6c
MD
760 ++token_contention_count[ntd->td_pri];
761 ++ntd->td_contended;
b12defdc
MD
762#endif
763
85946b6c 764 if (fairq_bypass > 0)
b12defdc
MD
765 goto skip;
766
b12defdc
MD
767 xtd = NULL;
768 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
85946b6c
MD
769 /*
770 * Never schedule threads returning to userland or the
771 * user thread scheduler helper thread when higher priority
772 * threads are present.
773 */
774 if (ntd->td_pri < TDPRI_KERN_LPSCHED) {
775 ntd = NULL;
776 break;
777 }
778
779 /*
780 * Try this one.
781 */
b12defdc
MD
782 if (TD_TOKS_NOT_HELD(ntd) ||
783 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) {
784 goto havethread;
785 }
85946b6c
MD
786#ifdef INVARIANTS
787 ++token_contention_count[ntd->td_pri];
788 ++ntd->td_contended;
b12defdc 789#endif
2a418930
MD
790 }
791
b12defdc 792skip:
2a418930
MD
793 /*
794 * We exhausted the run list, meaning that all runnable threads
b12defdc 795 * are contested.
2a418930
MD
796 */
797 cpu_pause();
798 ntd = &gd->gd_idlethread;
799#ifdef SMP
800 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
801 ASSERT_NO_TOKENS_HELD(ntd);
802 /* contention case, do not clear contention mask */
803#endif
804
805 /*
b12defdc
MD
806 * We are going to have to retry but if the current thread is not
807 * on the runq we instead switch through the idle thread to get away
808 * from the current thread. We have to flag for lwkt reschedule
809 * to prevent the idle thread from halting.
2a418930 810 *
b12defdc
MD
811 * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to
812 * instruct it to deal with the potential for deadlocks by
813 * ordering the tokens by address.
2a418930 814 */
b12defdc 815 if ((td->td_flags & TDF_RUNQ) == 0) {
85946b6c 816 need_lwkt_resched(); /* prevent hlt */
2a418930 817 goto haveidle;
4b5f931b 818 }
bd52bedf 819#if defined(INVARIANTS) && defined(__amd64__)
d5b2d319
MD
820 if ((read_rflags() & PSL_I) == 0) {
821 cpu_enable_intr();
822 panic("lwkt_switch() called with interrupts disabled");
823 }
824#endif
b12defdc
MD
825
826 /*
827 * Number iterations so far. After a certain point we switch to
828 * a sorted-address/monitor/mwait version of lwkt_getalltokens()
829 */
830 if (spinning < 0x7FFFFFFF)
831 ++spinning;
832
833#ifdef SMP
834 /*
835 * lwkt_getalltokens() failed in sorted token mode, we can use
836 * monitor/mwait in this case.
837 */
838 if (spinning >= lwkt_spin_loops &&
839 (cpu_mi_feature & CPU_MI_MONITOR) &&
840 lwkt_spin_monitor)
841 {
842 cpu_mmw_pause_int(&gd->gd_reqflags,
843 (gd->gd_reqflags | RQF_SPINNING) &
844 ~RQF_IDLECHECK_WK_MASK);
845 }
846#endif
847
848 /*
849 * We already checked that td is still scheduled so this should be
850 * safe.
851 */
852 splz_check();
853
854 /*
855 * This experimental resequencer is used as a fall-back to reduce
856 * hw cache line contention by placing each core's scheduler into a
857 * time-domain-multplexed slot.
858 *
859 * The resequencer is disabled by default. It's functionality has
860 * largely been superceeded by the token algorithm which limits races
861 * to a subset of cores.
862 *
863 * The resequencer algorithm tends to break down when more than
864 * 20 cores are contending. What appears to happen is that new
865 * tokens can be obtained out of address-sorted order by new cores
866 * while existing cores languish in long delays between retries and
867 * wind up being starved-out of the token acquisition.
868 */
869 if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) {
870 int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
871 int oseq;
872
873 while ((oseq = lwkt_cseq_rindex) != cseq) {
874 cpu_ccfence();
875#if 1
876 if (cpu_mi_feature & CPU_MI_MONITOR) {
877 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq);
878 } else {
879#endif
880 cpu_pause();
881 cpu_lfence();
882#if 1
883 }
8b402283 884#endif
0f0466c0 885 }
b12defdc
MD
886 DELAY(1);
887 atomic_add_int(&lwkt_cseq_rindex, 1);
2a418930 888 }
2a418930 889 /* highest level for(;;) loop */
f1d1c3fa 890 }
8a8d5d85 891
2a418930 892havethread:
b12defdc 893 /*
f9235b6d
MD
894 * If the thread we came up with is a higher or equal priority verses
895 * the thread at the head of the queue we move our thread to the
896 * front. This way we can always check the front of the queue.
be71787b
MD
897 *
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;
85946b6c 903#if 0
f9235b6d
MD
904 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
905 if (ntd != xtd && ntd->td_pri >= xtd->td_pri) {
906 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq);
907 TAILQ_INSERT_HEAD(&gd->gd_tdrunq, ntd, td_threadq);
908 }
85946b6c 909#endif
be71787b 910 gd->gd_idle_repeat = 0;
2a418930 911
f9235b6d 912havethread_preempted:
f9235b6d
MD
913 /*
914 * If the new target does not need the MP lock and we are holding it,
915 * release the MP lock. If the new target requires the MP lock we have
916 * already acquired it for the target.
8a8d5d85 917 */
2a418930 918 ;
f9235b6d
MD
919haveidle:
920 KASSERT(ntd->td_critcount,
b5d16701
MD
921 ("priority problem in lwkt_switch %d %d",
922 td->td_critcount, ntd->td_critcount));
923
94f6d86e 924 if (td != ntd) {
cc9b6223
MD
925 /*
926 * Execute the actual thread switch operation. This function
927 * returns to the current thread and returns the previous thread
928 * (which may be different from the thread we switched to).
929 *
930 * We are responsible for marking ntd as TDF_RUNNING.
931 */
94f6d86e 932 ++switch_count;
a1f0fb66 933 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
934 ntd->td_flags |= TDF_RUNNING;
935 lwkt_switch_return(td->td_switch(ntd));
936 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 937 }
b12defdc
MD
938
939#if 1
940 /*
941 * catch-all
942 */
943 splz_check();
944#endif
37af14fe
MD
945 /* NOTE: current cpu may have changed after switch */
946 crit_exit_quick(td);
8ad65e08
MD
947}
948
cc9b6223
MD
949/*
950 * Called by assembly in the td_switch (thread restore path) for thread
951 * bootstrap cases which do not 'return' to lwkt_switch().
952 */
953void
954lwkt_switch_return(thread_t otd)
955{
956#ifdef SMP
957 globaldata_t rgd;
958
959 /*
960 * Check if otd was migrating. Now that we are on ntd we can finish
961 * up the migration. This is a bit messy but it is the only place
962 * where td is known to be fully descheduled.
963 *
964 * We can only activate the migration if otd was migrating but not
965 * held on the cpu due to a preemption chain. We still have to
966 * clear TDF_RUNNING on the old thread either way.
967 *
968 * We are responsible for clearing the previously running thread's
969 * TDF_RUNNING.
970 */
971 if ((rgd = otd->td_migrate_gd) != NULL &&
972 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
973 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
974 (TDF_MIGRATING | TDF_RUNNING));
975 otd->td_migrate_gd = NULL;
976 otd->td_flags &= ~TDF_RUNNING;
977 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
978 } else {
979 otd->td_flags &= ~TDF_RUNNING;
980 }
981#else
982 otd->td_flags &= ~TDF_RUNNING;
983#endif
984}
985
b68b7282 986/*
96728c05
MD
987 * Request that the target thread preempt the current thread. Preemption
988 * only works under a specific set of conditions:
b68b7282 989 *
96728c05
MD
990 * - We are not preempting ourselves
991 * - The target thread is owned by the current cpu
992 * - We are not currently being preempted
993 * - The target is not currently being preempted
d3d1cbc8
MD
994 * - We are not holding any spin locks
995 * - The target thread is not holding any tokens
96728c05
MD
996 * - We are able to satisfy the target's MP lock requirements (if any).
997 *
998 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
999 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 1000 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
1001 * to determine whether preemption is possible (aka usually just the crit
1002 * priority of lwkt_schedule() itself).
b68b7282 1003 *
26a0694b
MD
1004 * XXX at the moment we run the target thread in a critical section during
1005 * the preemption in order to prevent the target from taking interrupts
1006 * that *WE* can't. Preemption is strictly limited to interrupt threads
1007 * and interrupt-like threads, outside of a critical section, and the
1008 * preempted source thread will be resumed the instant the target blocks
1009 * whether or not the source is scheduled (i.e. preemption is supposed to
1010 * be as transparent as possible).
b68b7282
MD
1011 */
1012void
f9235b6d 1013lwkt_preempt(thread_t ntd, int critcount)
b68b7282 1014{
46a3f46d 1015 struct globaldata *gd = mycpu;
cc9b6223 1016 thread_t xtd;
0a3f9b47 1017 thread_t td;
2d910aaf 1018 int save_gd_intr_nesting_level;
b68b7282 1019
26a0694b 1020 /*
96728c05
MD
1021 * The caller has put us in a critical section. We can only preempt
1022 * if the caller of the caller was not in a critical section (basically
f9235b6d 1023 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 1024 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 1025 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
1026 *
1027 * YYY The target thread must be in a critical section (else it must
1028 * inherit our critical section? I dunno yet).
26a0694b 1029 */
f9235b6d 1030 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 1031
b12defdc 1032 td = gd->gd_curthread;
fbc024e4 1033 if (preempt_enable == 0) {
85946b6c 1034#if 0
b12defdc
MD
1035 if (ntd->td_pri > td->td_pri)
1036 need_lwkt_resched();
85946b6c 1037#endif
fbc024e4
MD
1038 ++preempt_miss;
1039 return;
1040 }
f9235b6d 1041 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
1042 ++preempt_miss;
1043 return;
1044 }
f9235b6d 1045 if (td->td_critcount > critcount) {
96728c05 1046 ++preempt_miss;
85946b6c 1047#if 0
8ec60c3f 1048 need_lwkt_resched();
85946b6c 1049#endif
96728c05
MD
1050 return;
1051 }
1052#ifdef SMP
46a3f46d 1053 if (ntd->td_gd != gd) {
96728c05 1054 ++preempt_miss;
85946b6c 1055#if 0
8ec60c3f 1056 need_lwkt_resched();
85946b6c 1057#endif
96728c05
MD
1058 return;
1059 }
1060#endif
41a01a4d 1061 /*
77912481
MD
1062 * We don't have to check spinlocks here as they will also bump
1063 * td_critcount.
d3d1cbc8
MD
1064 *
1065 * Do not try to preempt if the target thread is holding any tokens.
1066 * We could try to acquire the tokens but this case is so rare there
1067 * is no need to support it.
41a01a4d 1068 */
77912481
MD
1069 KKASSERT(gd->gd_spinlocks_wr == 0);
1070
3b998fa9 1071 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 1072 ++preempt_miss;
85946b6c 1073#if 0
d3d1cbc8 1074 need_lwkt_resched();
85946b6c 1075#endif
d3d1cbc8
MD
1076 return;
1077 }
26a0694b
MD
1078 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1079 ++preempt_weird;
85946b6c 1080#if 0
8ec60c3f 1081 need_lwkt_resched();
85946b6c 1082#endif
26a0694b
MD
1083 return;
1084 }
1085 if (ntd->td_preempted) {
4b5f931b 1086 ++preempt_hit;
85946b6c 1087#if 0
8ec60c3f 1088 need_lwkt_resched();
85946b6c 1089#endif
26a0694b 1090 return;
b68b7282 1091 }
da0b0e8b 1092 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1093
8ec60c3f
MD
1094 /*
1095 * Since we are able to preempt the current thread, there is no need to
1096 * call need_lwkt_resched().
2d910aaf
MD
1097 *
1098 * We must temporarily clear gd_intr_nesting_level around the switch
1099 * since switchouts from the target thread are allowed (they will just
1100 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1101 *
1102 * A preemption must switch back to the original thread, assert the
1103 * case.
8ec60c3f 1104 */
26a0694b
MD
1105 ++preempt_hit;
1106 ntd->td_preempted = td;
1107 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1108 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1109 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1110 gd->gd_intr_nesting_level = 0;
cc9b6223
MD
1111 ntd->td_flags |= TDF_RUNNING;
1112 xtd = td->td_switch(ntd);
1113 KKASSERT(xtd == ntd);
1114 lwkt_switch_return(xtd);
2d910aaf 1115 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1116
26a0694b
MD
1117 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1118 ntd->td_preempted = NULL;
1119 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1120}
1121
f1d1c3fa 1122/*
faaeffac 1123 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1124 * This will work inside a critical section but not inside a hard code
1125 * section.
ef0fdad1 1126 *
f1d1c3fa
MD
1127 * (self contained on a per cpu basis)
1128 */
1129void
faaeffac 1130splz_check(void)
f1d1c3fa 1131{
7966cb69
MD
1132 globaldata_t gd = mycpu;
1133 thread_t td = gd->gd_curthread;
ef0fdad1 1134
4a28fe22
MD
1135 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1136 gd->gd_intr_nesting_level == 0 &&
1137 td->td_nest_count < 2)
1138 {
f1d1c3fa 1139 splz();
4a28fe22
MD
1140 }
1141}
1142
1143/*
1144 * This version is integrated into crit_exit, reqflags has already
1145 * been tested but td_critcount has not.
1146 *
1147 * We only want to execute the splz() on the 1->0 transition of
1148 * critcount and not in a hard code section or if too deeply nested.
1149 */
1150void
1151lwkt_maybe_splz(thread_t td)
1152{
1153 globaldata_t gd = td->td_gd;
1154
1155 if (td->td_critcount == 0 &&
1156 gd->gd_intr_nesting_level == 0 &&
1157 td->td_nest_count < 2)
1158 {
1159 splz();
1160 }
f1d1c3fa
MD
1161}
1162
e6546af9
MD
1163/*
1164 * Drivers which set up processing co-threads can call this function to
1165 * run the co-thread at a higher priority and to allow it to preempt
1166 * normal threads.
1167 */
1168void
1169lwkt_set_interrupt_support_thread(void)
1170{
1171 thread_t td = curthread;
1172
1173 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1174 td->td_flags |= TDF_INTTHREAD;
1175 td->td_preemptable = lwkt_preempt;
1176}
1177
1178
8ad65e08 1179/*
f9235b6d
MD
1180 * This function is used to negotiate a passive release of the current
1181 * process/lwp designation with the user scheduler, allowing the user
1182 * scheduler to schedule another user thread. The related kernel thread
1183 * (curthread) continues running in the released state.
8ad65e08
MD
1184 */
1185void
f9235b6d 1186lwkt_passive_release(struct thread *td)
8ad65e08 1187{
f9235b6d
MD
1188 struct lwp *lp = td->td_lwp;
1189
1190 td->td_release = NULL;
1191 lwkt_setpri_self(TDPRI_KERN_USER);
1192 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1193}
1194
f9235b6d 1195
3824f392 1196/*
d2d8515b
MD
1197 * This implements a LWKT yield, allowing a kernel thread to yield to other
1198 * kernel threads at the same or higher priority. This function can be
1199 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1200 *
d2d8515b
MD
1201 * Most kernel threads run at the same priority in order to allow equal
1202 * sharing.
f9235b6d
MD
1203 *
1204 * (self contained on a per cpu basis)
3824f392
MD
1205 */
1206void
f9235b6d 1207lwkt_yield(void)
3824f392 1208{
f9235b6d
MD
1209 globaldata_t gd = mycpu;
1210 thread_t td = gd->gd_curthread;
3824f392 1211
f9235b6d
MD
1212 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1213 splz();
85946b6c 1214 if (lwkt_resched_wanted()) {
f9235b6d
MD
1215 lwkt_schedule_self(curthread);
1216 lwkt_switch();
f9235b6d 1217 }
3824f392
MD
1218}
1219
1220/*
f9235b6d
MD
1221 * This yield is designed for kernel threads with a user context.
1222 *
1223 * The kernel acting on behalf of the user is potentially cpu-bound,
1224 * this function will efficiently allow other threads to run and also
1225 * switch to other processes by releasing.
3824f392
MD
1226 *
1227 * The lwkt_user_yield() function is designed to have very low overhead
1228 * if no yield is determined to be needed.
1229 */
1230void
1231lwkt_user_yield(void)
1232{
f9235b6d
MD
1233 globaldata_t gd = mycpu;
1234 thread_t td = gd->gd_curthread;
1235
1236 /*
1237 * Always run any pending interrupts in case we are in a critical
1238 * section.
1239 */
1240 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1241 splz();
3824f392 1242
3824f392 1243 /*
f9235b6d
MD
1244 * Switch (which forces a release) if another kernel thread needs
1245 * the cpu, if userland wants us to resched, or if our kernel
1246 * quantum has run out.
3824f392 1247 */
f9235b6d 1248 if (lwkt_resched_wanted() ||
85946b6c 1249 user_resched_wanted())
f9235b6d 1250 {
3824f392 1251 lwkt_switch();
3824f392
MD
1252 }
1253
f9235b6d 1254#if 0
3824f392 1255 /*
f9235b6d
MD
1256 * Reacquire the current process if we are released.
1257 *
1258 * XXX not implemented atm. The kernel may be holding locks and such,
1259 * so we want the thread to continue to receive cpu.
3824f392 1260 */
f9235b6d
MD
1261 if (td->td_release == NULL && lp) {
1262 lp->lwp_proc->p_usched->acquire_curproc(lp);
1263 td->td_release = lwkt_passive_release;
1264 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1265 }
f9235b6d 1266#endif
b9eb1c19
MD
1267}
1268
8ad65e08 1269/*
f1d1c3fa
MD
1270 * Generic schedule. Possibly schedule threads belonging to other cpus and
1271 * deal with threads that might be blocked on a wait queue.
1272 *
0a3f9b47
MD
1273 * We have a little helper inline function which does additional work after
1274 * the thread has been enqueued, including dealing with preemption and
1275 * setting need_lwkt_resched() (which prevents the kernel from returning
1276 * to userland until it has processed higher priority threads).
6330a558
MD
1277 *
1278 * It is possible for this routine to be called after a failed _enqueue
1279 * (due to the target thread migrating, sleeping, or otherwise blocked).
1280 * We have to check that the thread is actually on the run queue!
8ad65e08 1281 */
0a3f9b47
MD
1282static __inline
1283void
85946b6c 1284_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1285{
6330a558 1286 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1287 if (ntd->td_preemptable) {
f9235b6d 1288 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1289 }
0a3f9b47
MD
1290 }
1291}
1292
361d01dd 1293static __inline
8ad65e08 1294void
85946b6c 1295_lwkt_schedule(thread_t td)
8ad65e08 1296{
37af14fe
MD
1297 globaldata_t mygd = mycpu;
1298
cf709dd2
MD
1299 KASSERT(td != &td->td_gd->gd_idlethread,
1300 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1301 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1302 crit_enter_gd(mygd);
9388413d 1303 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 1304 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1305 _lwkt_enqueue(td);
1306 } else {
f1d1c3fa 1307 /*
7cd8d145
MD
1308 * If we own the thread, there is no race (since we are in a
1309 * critical section). If we do not own the thread there might
1310 * be a race but the target cpu will deal with it.
f1d1c3fa 1311 */
0f7a3396 1312#ifdef SMP
7cd8d145 1313 if (td->td_gd == mygd) {
9d265729 1314 _lwkt_enqueue(td);
85946b6c 1315 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1316 } else {
e381e77c 1317 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1318 }
0f7a3396 1319#else
7cd8d145 1320 _lwkt_enqueue(td);
85946b6c 1321 _lwkt_schedule_post(mygd, td, 1);
0f7a3396 1322#endif
8ad65e08 1323 }
37af14fe 1324 crit_exit_gd(mygd);
8ad65e08
MD
1325}
1326
361d01dd
MD
1327void
1328lwkt_schedule(thread_t td)
1329{
85946b6c 1330 _lwkt_schedule(td);
361d01dd
MD
1331}
1332
1333void
85946b6c 1334lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1335{
85946b6c 1336 _lwkt_schedule(td);
361d01dd
MD
1337}
1338
88ebb169
SW
1339#ifdef SMP
1340
e381e77c
MD
1341/*
1342 * When scheduled remotely if frame != NULL the IPIQ is being
1343 * run via doreti or an interrupt then preemption can be allowed.
1344 *
1345 * To allow preemption we have to drop the critical section so only
1346 * one is present in _lwkt_schedule_post.
1347 */
1348static void
1349lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1350{
1351 thread_t td = curthread;
1352 thread_t ntd = arg;
1353
1354 if (frame && ntd->td_preemptable) {
1355 crit_exit_noyield(td);
85946b6c 1356 _lwkt_schedule(ntd);
e381e77c
MD
1357 crit_enter_quick(td);
1358 } else {
85946b6c 1359 _lwkt_schedule(ntd);
e381e77c
MD
1360 }
1361}
1362
d9eea1a5 1363/*
52eedfb5
MD
1364 * Thread migration using a 'Pull' method. The thread may or may not be
1365 * the current thread. It MUST be descheduled and in a stable state.
1366 * lwkt_giveaway() must be called on the cpu owning the thread.
1367 *
1368 * At any point after lwkt_giveaway() is called, the target cpu may
1369 * 'pull' the thread by calling lwkt_acquire().
1370 *
ae8e83e6
MD
1371 * We have to make sure the thread is not sitting on a per-cpu tsleep
1372 * queue or it will blow up when it moves to another cpu.
1373 *
52eedfb5 1374 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1375 */
52eedfb5
MD
1376void
1377lwkt_giveaway(thread_t td)
1378{
3b4192fb 1379 globaldata_t gd = mycpu;
52eedfb5 1380
3b4192fb
MD
1381 crit_enter_gd(gd);
1382 if (td->td_flags & TDF_TSLEEPQ)
1383 tsleep_remove(td);
1384 KKASSERT(td->td_gd == gd);
1385 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1386 td->td_flags |= TDF_MIGRATING;
1387 crit_exit_gd(gd);
52eedfb5
MD
1388}
1389
a2a5ad0d
MD
1390void
1391lwkt_acquire(thread_t td)
1392{
37af14fe
MD
1393 globaldata_t gd;
1394 globaldata_t mygd;
cc9b6223 1395 int retry = 10000000;
a2a5ad0d 1396
52eedfb5 1397 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1398 gd = td->td_gd;
37af14fe 1399 mygd = mycpu;
52eedfb5 1400 if (gd != mycpu) {
35238fa5 1401 cpu_lfence();
52eedfb5 1402 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1403 crit_enter_gd(mygd);
cfaeae2a 1404 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23
MD
1405 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1406#ifdef SMP
1407 lwkt_process_ipiq();
1408#endif
52eedfb5 1409 cpu_lfence();
cc9b6223
MD
1410 if (--retry == 0) {
1411 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1412 td, td->td_flags);
1413 retry = 10000000;
1414 }
df910c23 1415 }
cfaeae2a 1416 DEBUG_POP_INFO();
562273ea 1417 cpu_mfence();
37af14fe 1418 td->td_gd = mygd;
52eedfb5
MD
1419 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1420 td->td_flags &= ~TDF_MIGRATING;
1421 crit_exit_gd(mygd);
1422 } else {
1423 crit_enter_gd(mygd);
1424 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1425 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1426 crit_exit_gd(mygd);
a2a5ad0d
MD
1427 }
1428}
1429
52eedfb5
MD
1430#endif
1431
f1d1c3fa
MD
1432/*
1433 * Generic deschedule. Descheduling threads other then your own should be
1434 * done only in carefully controlled circumstances. Descheduling is
1435 * asynchronous.
1436 *
1437 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1438 */
1439void
1440lwkt_deschedule(thread_t td)
1441{
f1d1c3fa 1442 crit_enter();
b8a98473 1443#ifdef SMP
f1d1c3fa
MD
1444 if (td == curthread) {
1445 _lwkt_dequeue(td);
1446 } else {
a72187e9 1447 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1448 _lwkt_dequeue(td);
1449 } else {
b8a98473 1450 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1451 }
1452 }
b8a98473
MD
1453#else
1454 _lwkt_dequeue(td);
1455#endif
f1d1c3fa
MD
1456 crit_exit();
1457}
1458
4b5f931b
MD
1459/*
1460 * Set the target thread's priority. This routine does not automatically
1461 * switch to a higher priority thread, LWKT threads are not designed for
1462 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1463 */
1464void
1465lwkt_setpri(thread_t td, int pri)
1466{
f9235b6d
MD
1467 if (td->td_pri != pri) {
1468 KKASSERT(pri >= 0);
1469 crit_enter();
1470 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1471 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1472 _lwkt_dequeue(td);
1473 td->td_pri = pri;
1474 _lwkt_enqueue(td);
1475 } else {
1476 td->td_pri = pri;
1477 }
1478 crit_exit();
26a0694b 1479 }
26a0694b
MD
1480}
1481
03bd0a5e
MD
1482/*
1483 * Set the initial priority for a thread prior to it being scheduled for
1484 * the first time. The thread MUST NOT be scheduled before or during
1485 * this call. The thread may be assigned to a cpu other then the current
1486 * cpu.
1487 *
1488 * Typically used after a thread has been created with TDF_STOPPREQ,
1489 * and before the thread is initially scheduled.
1490 */
1491void
1492lwkt_setpri_initial(thread_t td, int pri)
1493{
1494 KKASSERT(pri >= 0);
1495 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1496 td->td_pri = pri;
03bd0a5e
MD
1497}
1498
26a0694b
MD
1499void
1500lwkt_setpri_self(int pri)
1501{
1502 thread_t td = curthread;
1503
4b5f931b
MD
1504 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1505 crit_enter();
1506 if (td->td_flags & TDF_RUNQ) {
1507 _lwkt_dequeue(td);
f9235b6d 1508 td->td_pri = pri;
4b5f931b
MD
1509 _lwkt_enqueue(td);
1510 } else {
f9235b6d 1511 td->td_pri = pri;
4b5f931b
MD
1512 }
1513 crit_exit();
1514}
1515
f9235b6d 1516/*
85946b6c 1517 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1518 */
1519void
85946b6c 1520lwkt_schedulerclock(thread_t td)
f9235b6d 1521{
85946b6c
MD
1522 globaldata_t gd = td->td_gd;
1523 thread_t xtd;
2a418930 1524
85946b6c
MD
1525 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1526 /*
1527 * If the current thread is at the head of the runq shift it to the
1528 * end of any equal-priority threads and request a LWKT reschedule
1529 * if it moved.
1530 */
1531 xtd = TAILQ_NEXT(td, td_threadq);
1532 if (xtd && xtd->td_pri == td->td_pri) {
1533 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1534 while (xtd && xtd->td_pri == td->td_pri)
1535 xtd = TAILQ_NEXT(xtd, td_threadq);
1536 if (xtd)
1537 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1538 else
1539 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1540 need_lwkt_resched();
f9235b6d 1541 }
85946b6c
MD
1542 } else {
1543 /*
1544 * If we scheduled a thread other than the one at the head of the
1545 * queue always request a reschedule every tick.
1546 */
1547 need_lwkt_resched();
f9235b6d
MD
1548 }
1549}
1550
5d21b981 1551/*
52eedfb5
MD
1552 * Migrate the current thread to the specified cpu.
1553 *
cc9b6223
MD
1554 * This is accomplished by descheduling ourselves from the current cpu
1555 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1556 * 'old' thread wants to migrate after it has been completely switched out
1557 * and will complete the migration.
1558 *
1559 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1560 *
1561 * We must be sure to release our current process designation (if a user
1562 * process) before clearing out any tsleepq we are on because the release
1563 * code may re-add us.
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1564 *
1565 * We must be sure to remove ourselves from the current cpu's tsleepq
1566 * before potentially moving to another queue. The thread can be on
1567 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1568 */
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1569
1570void
1571lwkt_setcpu_self(globaldata_t rgd)
1572{
1573#ifdef SMP
1574 thread_t td = curthread;
1575
1576 if (td->td_gd != rgd) {
1577 crit_enter_quick(td);
cc9b6223 1578
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1579 if (td->td_release)
1580 td->td_release(td);
ae8e83e6 1581 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1582 tsleep_remove(td);
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1583
1584 /*
1585 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1586 * trying to deschedule ourselves and switch away, then deschedule
1587 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1588 * call lwkt_switch() to complete the operation.
1589 */
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1590 td->td_flags |= TDF_MIGRATING;
1591 lwkt_deschedule_self(td);
52eedfb5 1592 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1593 td->td_migrate_gd = rgd;
5d21b981 1594 lwkt_switch();
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1595
1596 /*
1597 * We are now on the target cpu
1598 */
1599 KKASSERT(rgd == mycpu);
52eedfb5 1600 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
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1601 crit_exit_quick(td);
1602 }
1603#endif
1604}
1605
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1606void
1607lwkt_migratecpu(int cpuid)
1608{
1609#ifdef SMP
1610 globaldata_t rgd;
1611
1612 rgd = globaldata_find(cpuid);
1613 lwkt_setcpu_self(rgd);
1614#endif
1615}
1616
cc9b6223 1617#ifdef SMP
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1618/*
1619 * Remote IPI for cpu migration (called while in a critical section so we
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1620 * do not have to enter another one).
1621 *
1622 * The thread (td) has already been completely descheduled from the
1623 * originating cpu and we can simply assert the case. The thread is
1624 * assigned to the new cpu and enqueued.
5d21b981 1625 *
cc9b6223 1626 * The thread will re-add itself to tdallq when it resumes execution.
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1627 */
1628static void
1629lwkt_setcpu_remote(void *arg)
1630{
1631 thread_t td = arg;
1632 globaldata_t gd = mycpu;
1633
cc9b6223 1634 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1635 td->td_gd = gd;
562273ea 1636 cpu_mfence();
5d21b981 1637 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1638 KKASSERT(td->td_migrate_gd == NULL);
9388413d 1639 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
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1640 _lwkt_enqueue(td);
1641}
3d28ff59 1642#endif
5d21b981 1643
553ea3c8 1644struct lwp *
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1645lwkt_preempted_proc(void)
1646{
73e4f7b9 1647 thread_t td = curthread;
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1648 while (td->td_preempted)
1649 td = td->td_preempted;
553ea3c8 1650 return(td->td_lwp);
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1651}
1652
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1653/*
1654 * Create a kernel process/thread/whatever. It shares it's address space
1655 * with proc0 - ie: kernel only.
1656 *
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1657 * If the cpu is not specified one will be selected. In the future
1658 * specifying a cpu of -1 will enable kernel thread migration between
1659 * cpus.
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1660 */
1661int
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1662lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1663 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1664{
73e4f7b9 1665 thread_t td;
e2565a42 1666 __va_list ap;
99df837e 1667
d3d32139 1668 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1669 tdflags);
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1670 if (tdp)
1671 *tdp = td;
709799ea 1672 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1673
1674 /*
1675 * Set up arg0 for 'ps' etc
1676 */
e2565a42 1677 __va_start(ap, fmt);
379210cb 1678 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1679 __va_end(ap);
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1680
1681 /*
1682 * Schedule the thread to run
1683 */
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1684 if ((td->td_flags & TDF_STOPREQ) == 0)
1685 lwkt_schedule(td);
1686 else
1687 td->td_flags &= ~TDF_STOPREQ;
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1688 return 0;
1689}
1690
1691/*
1692 * Destroy an LWKT thread. Warning! This function is not called when
1693 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1694 * uses a different reaping mechanism.
1695 */
1696void
1697lwkt_exit(void)
1698{
1699 thread_t td = curthread;
c070746a 1700 thread_t std;
8826f33a 1701 globaldata_t gd;
99df837e 1702
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1703 /*
1704 * Do any cleanup that might block here
1705 */
99df837e 1706 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1707 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1708 caps_exit(td);
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1709 biosched_done(td);
1710 dsched_exit_thread(td);
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1711
1712 /*
1713 * Get us into a critical section to interlock gd_freetd and loop
1714 * until we can get it freed.
1715 *
1716 * We have to cache the current td in gd_freetd because objcache_put()ing
1717 * it would rip it out from under us while our thread is still active.
1718 */
1719 gd = mycpu;
37af14fe 1720 crit_enter_quick(td);
c070746a 1721 while ((std = gd->gd_freetd) != NULL) {
cf709dd2 1722 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
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1723 gd->gd_freetd = NULL;
1724 objcache_put(thread_cache, std);
1725 }
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1726
1727 /*
1728 * Remove thread resources from kernel lists and deschedule us for
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1729 * the last time. We cannot block after this point or we may end
1730 * up with a stale td on the tsleepq.
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1731 */
1732 if (td->td_flags & TDF_TSLEEPQ)
1733 tsleep_remove(td);
37af14fe 1734 lwkt_deschedule_self(td);
e56e4dea 1735 lwkt_remove_tdallq(td);
74c9628e 1736 KKASSERT(td->td_refs == 0);
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1737
1738 /*
1739 * Final cleanup
1740 */
1741 KKASSERT(gd->gd_freetd == NULL);
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1742 if (td->td_flags & TDF_ALLOCATED_THREAD)
1743 gd->gd_freetd = td;
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1744 cpu_thread_exit();
1745}
1746
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1747void
1748lwkt_remove_tdallq(thread_t td)
1749{
1750 KKASSERT(td->td_gd == mycpu);
1751 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1752}
1753
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1754/*
1755 * Code reduction and branch prediction improvements. Call/return
1756 * overhead on modern cpus often degenerates into 0 cycles due to
1757 * the cpu's branch prediction hardware and return pc cache. We
1758 * can take advantage of this by not inlining medium-complexity
1759 * functions and we can also reduce the branch prediction impact
1760 * by collapsing perfectly predictable branches into a single
1761 * procedure instead of duplicating it.
1762 *
1763 * Is any of this noticeable? Probably not, so I'll take the
1764 * smaller code size.
1765 */
1766void
b6468f56 1767crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1768{
b6468f56 1769 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1770}
1771
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1772void
1773crit_panic(void)
1774{
1775 thread_t td = curthread;
850634cc 1776 int lcrit = td->td_critcount;
2d93b37a 1777
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1778 td->td_critcount = 0;
1779 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1780 /* NOT REACHED */
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1781}
1782
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1783#ifdef SMP
1784
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1785/*
1786 * Called from debugger/panic on cpus which have been stopped. We must still
1787 * process the IPIQ while stopped, even if we were stopped while in a critical
1788 * section (XXX).
1789 *
1790 * If we are dumping also try to process any pending interrupts. This may
1791 * or may not work depending on the state of the cpu at the point it was
1792 * stopped.
1793 */
1794void
1795lwkt_smp_stopped(void)
1796{
1797 globaldata_t gd = mycpu;
1798
1799 crit_enter_gd(gd);
1800 if (dumping) {
1801 lwkt_process_ipiq();
1802 splz();
1803 } else {
1804 lwkt_process_ipiq();
1805 }
1806 crit_exit_gd(gd);
1807}
1808
d165e668 1809#endif