kernel - Add vfs.repurpose_enable, adjust B_HASBOGUS
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
b12defdc 2 * Copyright (c) 2003-2011 The DragonFly Project. All rights reserved.
60f60350 3 *
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4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
60f60350 6 *
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7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
60f60350 10 *
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11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
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14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
60f60350 20 *
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21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
8ad65e08 32 * SUCH DAMAGE.
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33 */
34
35/*
36 * Each cpu in a system has its own self-contained light weight kernel
37 * thread scheduler, which means that generally speaking we only need
38 * to use a critical section to avoid problems. Foreign thread
39 * scheduling is queued via (async) IPIs.
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40 */
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/kernel.h>
45#include <sys/proc.h>
46#include <sys/rtprio.h>
b37f18d6 47#include <sys/kinfo.h>
8ad65e08 48#include <sys/queue.h>
7d0bac62 49#include <sys/sysctl.h>
99df837e 50#include <sys/kthread.h>
f1d1c3fa 51#include <machine/cpu.h>
99df837e 52#include <sys/lock.h>
9d265729 53#include <sys/spinlock.h>
57aa743c 54#include <sys/ktr.h>
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55
56#include <sys/thread2.h>
57#include <sys/spinlock2.h>
684a93c4 58#include <sys/mplock2.h>
f1d1c3fa 59
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60#include <sys/dsched.h>
61
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62#include <vm/vm.h>
63#include <vm/vm_param.h>
64#include <vm/vm_kern.h>
65#include <vm/vm_object.h>
66#include <vm/vm_page.h>
67#include <vm/vm_map.h>
68#include <vm/vm_pager.h>
69#include <vm/vm_extern.h>
7d0bac62 70
99df837e 71#include <machine/stdarg.h>
96728c05 72#include <machine/smp.h>
99df837e 73
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74#ifdef _KERNEL_VIRTUAL
75#include <pthread.h>
76#endif
77
d850923c
AE
78#if !defined(KTR_CTXSW)
79#define KTR_CTXSW KTR_ALL
80#endif
81KTR_INFO_MASTER(ctxsw);
5bf48697
AE
82KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td);
83KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td);
84KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm);
85KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td);
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
e28c8ef4
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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;
fb0f29c4 96static int lwkt_use_spin_port;
40aaf5fc 97static struct objcache *thread_cache;
a46b4a23 98int cpu_mwait_spin = 0;
05220613 99
e381e77c 100static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 101static void lwkt_setcpu_remote(void *arg);
e381e77c 102
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103/*
104 * We can make all thread ports use the spin backend instead of the thread
105 * backend. This should only be set to debug the spin backend.
106 */
107TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
108
0f7a3396 109#ifdef INVARIANTS
0c52fa62
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110SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
111 "Panic if attempting to switch lwkt's while mastering cpusync");
0f7a3396 112#endif
0c52fa62
SG
113SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
114 "Number of switched threads");
9733f757 115SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 116 "Successful preemption events");
9733f757 117SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
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118 "Failed preemption events");
119SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
120 "Number of preempted threads.");
b12defdc 121static int fairq_enable = 0;
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122SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
123 &fairq_enable, 0, "Turn on fairq priority accumulators");
85946b6c 124static int fairq_bypass = -1;
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125SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
126 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
127extern int lwkt_sched_debug;
128int lwkt_sched_debug = 0;
129SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
130 &lwkt_sched_debug, 0, "Scheduler debug");
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131static u_int lwkt_spin_loops = 10;
132SYSCTL_UINT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
b12defdc 133 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
fbc024e4 134static int preempt_enable = 1;
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135SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
136 &preempt_enable, 0, "Enable preemption");
7b234d8c 137static int lwkt_cache_threads = 0;
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138SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
139 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 140
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141/*
142 * These helper procedures handle the runq, they can only be called from
143 * within a critical section.
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144 *
145 * WARNING! Prior to SMP being brought up it is possible to enqueue and
146 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
147 * instead of 'mycpu' when referencing the globaldata structure. Once
148 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 149 */
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150static __inline
151void
152_lwkt_dequeue(thread_t td)
153{
154 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 155 struct globaldata *gd = td->td_gd;
4b5f931b 156
f1d1c3fa 157 td->td_flags &= ~TDF_RUNQ;
f9235b6d 158 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
de4d4cb0 159 --gd->gd_tdrunqcount;
f9235b6d 160 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 161 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
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162 }
163}
164
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165/*
166 * Priority enqueue.
167 *
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168 * There are a limited number of lwkt threads runnable since user
169 * processes only schedule one at a time per cpu. However, there can
170 * be many user processes in kernel mode exiting from a tsleep() which
e3e6be1f 171 * become runnable.
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172 *
173 * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and
174 * will ignore user priority. This is to ensure that user threads in
175 * kernel mode get cpu at some point regardless of what the user
176 * scheduler thinks.
f9235b6d 177 */
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178static __inline
179void
180_lwkt_enqueue(thread_t td)
181{
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182 thread_t xtd;
183
7f5d7ed7 184 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 185 struct globaldata *gd = td->td_gd;
4b5f931b 186
f1d1c3fa 187 td->td_flags |= TDF_RUNQ;
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188 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
189 if (xtd == NULL) {
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190 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
191 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 192 } else {
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193 /*
194 * NOTE: td_upri - higher numbers more desireable, same sense
195 * as td_pri (typically reversed from lwp_upri).
196 *
197 * In the equal priority case we want the best selection
198 * at the beginning so the less desireable selections know
199 * that they have to setrunqueue/go-to-another-cpu, even
200 * though it means switching back to the 'best' selection.
201 * This also avoids degenerate situations when many threads
202 * are runnable or waking up at the same time.
203 *
204 * If upri matches exactly place at end/round-robin.
205 */
d992c377 206 while (xtd &&
e3e6be1f 207 (xtd->td_pri >= td->td_pri ||
d992c377 208 (xtd->td_pri == td->td_pri &&
e3e6be1f 209 xtd->td_upri >= td->td_upri))) {
85946b6c 210 xtd = TAILQ_NEXT(xtd, td_threadq);
d992c377 211 }
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212 if (xtd)
213 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
214 else
215 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 216 }
de4d4cb0 217 ++gd->gd_tdrunqcount;
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218
219 /*
85946b6c 220 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 221 */
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222 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
223 need_lwkt_resched();
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224 }
225}
8ad65e08 226
e28c8ef4 227static boolean_t
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228_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
229{
230 struct thread *td = (struct thread *)obj;
231
232 td->td_kstack = NULL;
233 td->td_kstack_size = 0;
234 td->td_flags = TDF_ALLOCATED_THREAD;
4643740a 235 td->td_mpflags = 0;
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236 return (1);
237}
238
239static void
240_lwkt_thread_dtor(void *obj, void *privdata)
241{
242 struct thread *td = (struct thread *)obj;
243
244 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
245 ("_lwkt_thread_dtor: not allocated from objcache"));
246 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
247 td->td_kstack_size > 0,
248 ("_lwkt_thread_dtor: corrupted stack"));
249 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
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250 td->td_kstack = NULL;
251 td->td_flags = 0;
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252}
253
254/*
255 * Initialize the lwkt s/system.
765b1ae0 256 *
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257 * Nominally cache up to 32 thread + kstack structures. Cache more on
258 * systems with a lot of cpu cores.
40aaf5fc 259 */
ced589cb 260static void
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261lwkt_init(void)
262{
765b1ae0 263 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
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264 if (lwkt_cache_threads == 0) {
265 lwkt_cache_threads = ncpus * 4;
266 if (lwkt_cache_threads < 32)
267 lwkt_cache_threads = 32;
268 }
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MD
269 thread_cache = objcache_create_mbacked(
270 M_THREAD, sizeof(struct thread),
2fce2579 271 0, lwkt_cache_threads,
765b1ae0 272 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
40aaf5fc 273}
ced589cb 274SYSINIT(lwkt_init, SI_BOOT2_LWKT_INIT, SI_ORDER_FIRST, lwkt_init, NULL);
40aaf5fc 275
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276/*
277 * Schedule a thread to run. As the current thread we can always safely
278 * schedule ourselves, and a shortcut procedure is provided for that
279 * function.
280 *
281 * (non-blocking, self contained on a per cpu basis)
282 */
283void
284lwkt_schedule_self(thread_t td)
285{
cfaeae2a 286 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 287 crit_enter_quick(td);
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288 KASSERT(td != &td->td_gd->gd_idlethread,
289 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
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290 KKASSERT(td->td_lwp == NULL ||
291 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
37af14fe 292 _lwkt_enqueue(td);
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MD
293 crit_exit_quick(td);
294}
295
296/*
297 * Deschedule a thread.
298 *
299 * (non-blocking, self contained on a per cpu basis)
300 */
301void
302lwkt_deschedule_self(thread_t td)
303{
304 crit_enter_quick(td);
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305 _lwkt_dequeue(td);
306 crit_exit_quick(td);
307}
308
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309/*
310 * LWKTs operate on a per-cpu basis
311 *
73e4f7b9 312 * WARNING! Called from early boot, 'mycpu' may not work yet.
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313 */
314void
315lwkt_gdinit(struct globaldata *gd)
316{
f9235b6d 317 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 318 TAILQ_INIT(&gd->gd_tdallq);
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319}
320
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321/*
322 * Create a new thread. The thread must be associated with a process context
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323 * or LWKT start address before it can be scheduled. If the target cpu is
324 * -1 the thread will be created on the current cpu.
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325 *
326 * If you intend to create a thread without a process context this function
327 * does everything except load the startup and switcher function.
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328 */
329thread_t
d3d32139 330lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 331{
d2d8515b 332 static int cpu_rotator;
c070746a 333 globaldata_t gd = mycpu;
99df837e 334 void *stack;
7d0bac62 335
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336 /*
337 * If static thread storage is not supplied allocate a thread. Reuse
338 * a cached free thread if possible. gd_freetd is used to keep an exiting
339 * thread intact through the exit.
340 */
ef0fdad1 341 if (td == NULL) {
cf709dd2
MD
342 crit_enter_gd(gd);
343 if ((td = gd->gd_freetd) != NULL) {
344 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
345 TDF_RUNQ)) == 0);
c070746a 346 gd->gd_freetd = NULL;
cf709dd2 347 } else {
c070746a 348 td = objcache_get(thread_cache, M_WAITOK);
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MD
349 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
350 TDF_RUNQ)) == 0);
351 }
352 crit_exit_gd(gd);
40aaf5fc 353 KASSERT((td->td_flags &
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MD
354 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
355 TDF_ALLOCATED_THREAD,
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356 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
357 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 358 }
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359
360 /*
361 * Try to reuse cached stack.
362 */
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MD
363 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
364 if (flags & TDF_ALLOCATED_STACK) {
e4846942 365 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
366 stack = NULL;
367 }
368 }
369 if (stack == NULL) {
e40cfbd7 370 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 371 flags |= TDF_ALLOCATED_STACK;
99df837e 372 }
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MD
373 if (cpu < 0) {
374 cpu = ++cpu_rotator;
375 cpu_ccfence();
376 cpu %= ncpus;
377 }
378 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 379 return(td);
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MD
380}
381
382/*
383 * Initialize a preexisting thread structure. This function is used by
384 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
385 *
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386 * All threads start out in a critical section at a priority of
387 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
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388 * appropriate. This function may send an IPI message when the
389 * requested cpu is not the current cpu and consequently gd_tdallq may
390 * not be initialized synchronously from the point of view of the originating
391 * cpu.
392 *
393 * NOTE! we have to be careful in regards to creating threads for other cpus
394 * if SMP has not yet been activated.
7d0bac62 395 */
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396static void
397lwkt_init_thread_remote(void *arg)
398{
399 thread_t td = arg;
400
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401 /*
402 * Protected by critical section held by IPI dispatch
403 */
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404 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
405}
406
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407/*
408 * lwkt core thread structural initialization.
409 *
410 * NOTE: All threads are initialized as mpsafe threads.
411 */
7d0bac62 412void
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413lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
414 struct globaldata *gd)
7d0bac62 415{
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416 globaldata_t mygd = mycpu;
417
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418 bzero(td, sizeof(struct thread));
419 td->td_kstack = stack;
f470d0c8 420 td->td_kstack_size = stksize;
d3d32139 421 td->td_flags = flags;
4643740a 422 td->td_mpflags = 0;
f256b6c0 423 td->td_type = TD_TYPE_GENERIC;
26a0694b 424 td->td_gd = gd;
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425 td->td_pri = TDPRI_KERN_DAEMON;
426 td->td_critcount = 1;
54341a3b 427 td->td_toks_have = NULL;
3b998fa9 428 td->td_toks_stop = &td->td_toks_base;
c068fb59
SZ
429 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT)) {
430 lwkt_initport_spin(&td->td_msgport, td,
431 (flags & TDF_FIXEDCPU) ? TRUE : FALSE);
432 } else {
fb0f29c4 433 lwkt_initport_thread(&td->td_msgport, td);
c068fb59 434 }
99df837e 435 pmap_init_thread(td);
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436 /*
437 * Normally initializing a thread for a remote cpu requires sending an
438 * IPI. However, the idlethread is setup before the other cpus are
439 * activated so we have to treat it as a special case. XXX manipulation
440 * of gd_tdallq requires the BGL.
441 */
442 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 443 crit_enter_gd(mygd);
75cdbe6c 444 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 445 crit_exit_gd(mygd);
75cdbe6c 446 } else {
2db3b277 447 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 448 }
3573cf7b 449 dsched_enter_thread(td);
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450}
451
452void
453lwkt_set_comm(thread_t td, const char *ctl, ...)
454{
e2565a42 455 __va_list va;
73e4f7b9 456
e2565a42 457 __va_start(va, ctl);
379210cb 458 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 459 __va_end(va);
5bf48697 460 KTR_LOG(ctxsw_newtd, td, td->td_comm);
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MD
461}
462
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463/*
464 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
465 * this does not prevent the thread from migrating to another cpu so the
466 * gd_tdallq state is not protected by this.
467 */
99df837e 468void
73e4f7b9 469lwkt_hold(thread_t td)
99df837e 470{
74c9628e 471 atomic_add_int(&td->td_refs, 1);
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472}
473
474void
475lwkt_rele(thread_t td)
476{
477 KKASSERT(td->td_refs > 0);
74c9628e 478 atomic_add_int(&td->td_refs, -1);
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479}
480
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481void
482lwkt_free_thread(thread_t td)
483{
74c9628e 484 KKASSERT(td->td_refs == 0);
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485 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
486 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
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487 if (td->td_flags & TDF_ALLOCATED_THREAD) {
488 objcache_put(thread_cache, td);
489 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
490 /* client-allocated struct with internally allocated stack */
491 KASSERT(td->td_kstack && td->td_kstack_size > 0,
492 ("lwkt_free_thread: corrupted stack"));
493 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
494 td->td_kstack = NULL;
495 td->td_kstack_size = 0;
99df837e 496 }
a86ce0cd 497
e7c0dbba 498 KTR_LOG(ctxsw_deadtd, td);
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499}
500
501
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502/*
503 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
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504 * switch to the idlethread. Switching must occur within a critical
505 * section to avoid races with the scheduling queue.
506 *
507 * We always have full control over our cpu's run queue. Other cpus
508 * that wish to manipulate our queue must use the cpu_*msg() calls to
509 * talk to our cpu, so a critical section is all that is needed and
510 * the result is very, very fast thread switching.
511 *
96728c05
MD
512 * The LWKT scheduler uses a fixed priority model and round-robins at
513 * each priority level. User process scheduling is a totally
514 * different beast and LWKT priorities should not be confused with
515 * user process priorities.
f1d1c3fa 516 *
69d78e99
MD
517 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
518 * is not called by the current thread in the preemption case, only when
519 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
520 *
521 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
522 * migration and tsleep deschedule the current lwkt thread and call
523 * lwkt_switch(). In particular, the target cpu of the migration fully
524 * expects the thread to become non-runnable and can deadlock against
525 * cpusync operations if we run any IPIs prior to switching the thread out.
526 *
527 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 528 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
529 */
530void
531lwkt_switch(void)
532{
37af14fe
MD
533 globaldata_t gd = mycpu;
534 thread_t td = gd->gd_curthread;
8ad65e08 535 thread_t ntd;
5411d8f1 536 int upri;
8ad65e08 537
da0b0e8b 538 KKASSERT(gd->gd_processing_ipiq == 0);
121f93bc 539 KKASSERT(td->td_flags & TDF_RUNNING);
da0b0e8b 540
46a3f46d 541 /*
27e88a6e
MD
542 * Switching from within a 'fast' (non thread switched) interrupt or IPI
543 * is illegal. However, we may have to do it anyway if we hit a fatal
544 * kernel trap or we have paniced.
545 *
546 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 547 */
27e88a6e
MD
548 if (gd->gd_intr_nesting_level) {
549 int savegdnest;
550 int savegdtrap;
551
5fddbda2 552 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22 553 panic("lwkt_switch: Attempt to switch from a "
5a8df152 554 "fast interrupt, ipi, or hard code section, "
4a28fe22
MD
555 "td %p\n",
556 td);
27e88a6e
MD
557 } else {
558 savegdnest = gd->gd_intr_nesting_level;
559 savegdtrap = gd->gd_trap_nesting_level;
560 gd->gd_intr_nesting_level = 0;
561 gd->gd_trap_nesting_level = 0;
a7422615
MD
562 if ((td->td_flags & TDF_PANICWARN) == 0) {
563 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
564 kprintf("Warning: thread switch from interrupt, IPI, "
565 "or hard code section.\n"
a7422615 566 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 567 print_backtrace(-1);
a7422615 568 }
27e88a6e
MD
569 lwkt_switch();
570 gd->gd_intr_nesting_level = savegdnest;
571 gd->gd_trap_nesting_level = savegdtrap;
572 return;
573 }
96728c05 574 }
ef0fdad1 575
cb973d15 576 /*
85946b6c
MD
577 * Release our current user process designation if we are blocking
578 * or if a user reschedule was requested.
579 *
580 * NOTE: This function is NOT called if we are switching into or
581 * returning from a preemption.
582 *
583 * NOTE: Releasing our current user process designation may cause
584 * it to be assigned to another thread, which in turn will
585 * cause us to block in the usched acquire code when we attempt
586 * to return to userland.
587 *
588 * NOTE: On SMP systems this can be very nasty when heavy token
589 * contention is present so we want to be careful not to
590 * release the designation gratuitously.
cb973d15 591 */
85946b6c
MD
592 if (td->td_release &&
593 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 594 td->td_release(td);
85946b6c 595 }
cb973d15 596
85946b6c 597 /*
5411d8f1
MD
598 * Release all tokens. Once we do this we must remain in the critical
599 * section and cannot run IPIs or other interrupts until we switch away
600 * because they may implode if they try to get a token using our thread
601 * context.
85946b6c 602 */
37af14fe 603 crit_enter_gd(gd);
3b998fa9 604 if (TD_TOKS_HELD(td))
9d265729
MD
605 lwkt_relalltokens(td);
606
607 /*
b02926de
MD
608 * We had better not be holding any spin locks, but don't get into an
609 * endless panic loop.
9d265729 610 */
0846e4ce 611 KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL,
d666840a 612 ("lwkt_switch: still holding %d exclusive spinlocks!",
0846e4ce 613 gd->gd_spinlocks));
9d265729 614
0f7a3396
MD
615#ifdef INVARIANTS
616 if (td->td_cscount) {
6ea70f76 617 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
618 td);
619 if (panic_on_cscount)
620 panic("switching while mastering cpusync");
621 }
8a8d5d85 622#endif
f9235b6d
MD
623
624 /*
625 * If we had preempted another thread on this cpu, resume the preempted
626 * thread. This occurs transparently, whether the preempted thread
627 * was scheduled or not (it may have been preempted after descheduling
628 * itself).
629 *
630 * We have to setup the MP lock for the original thread after backing
631 * out the adjustment that was made to curthread when the original
632 * was preempted.
633 */
99df837e 634 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
635 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
636 ntd->td_flags |= TDF_PREEMPT_DONE;
7fb451cb 637 ntd->td_contended = 0; /* reset contended */
8ec60c3f
MD
638
639 /*
b9eb1c19
MD
640 * The interrupt may have woken a thread up, we need to properly
641 * set the reschedule flag if the originally interrupted thread is
642 * at a lower priority.
85946b6c
MD
643 *
644 * The interrupt may not have descheduled.
8ec60c3f 645 */
85946b6c 646 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 647 need_lwkt_resched();
f9235b6d
MD
648 goto havethread_preempted;
649 }
650
b12defdc 651 /*
5411d8f1
MD
652 * Figure out switch target. If we cannot switch to our desired target
653 * look for a thread that we can switch to.
cfaeae2a 654 *
5411d8f1
MD
655 * NOTE! The limited spin loop and related parameters are extremely
656 * important for system performance, particularly for pipes and
657 * concurrent conflicting VM faults.
f9235b6d 658 */
5411d8f1
MD
659 clear_lwkt_resched();
660 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
661
662 if (ntd) {
663 do {
664 if (TD_TOKS_NOT_HELD(ntd) ||
665 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops)))
666 {
667 goto havethread;
668 }
669 ++gd->gd_cnt.v_lock_colls;
7fb451cb 670 ++ntd->td_contended; /* overflow ok */
5411d8f1
MD
671 } while (ntd->td_contended < (lwkt_spin_loops >> 1));
672 upri = ntd->td_upri;
f9235b6d 673
f9235b6d 674 /*
5411d8f1
MD
675 * Bleh, the thread we wanted to switch to has a contended token.
676 * See if we can switch to another thread.
2a418930 677 *
5411d8f1
MD
678 * We generally don't want to do this because it represents a
679 * priority inversion. Do not allow the case if the thread
680 * is returning to userland (not a kernel thread) AND the thread
681 * has a lower upri.
f9235b6d 682 */
b12defdc 683 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
5411d8f1
MD
684 if (ntd->td_pri < TDPRI_KERN_LPSCHED && upri > ntd->td_upri)
685 break;
686 upri = ntd->td_upri;
b12defdc 687
5411d8f1
MD
688 /*
689 * Try this one.
690 */
691 if (TD_TOKS_NOT_HELD(ntd) ||
692 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops))) {
693 goto havethread;
694 }
7fb451cb 695 ++ntd->td_contended; /* overflow ok */
5411d8f1 696 ++gd->gd_cnt.v_lock_colls;
b12defdc 697 }
b12defdc
MD
698
699 /*
5411d8f1
MD
700 * Fall through, switch to idle thread to get us out of the current
701 * context. Since we were contended, prevent HLT by flagging a
702 * LWKT reschedule.
b12defdc 703 */
5411d8f1 704 need_lwkt_resched();
f1d1c3fa 705 }
8a8d5d85 706
5411d8f1
MD
707 /*
708 * We either contended on ntd or the runq is empty. We must switch
709 * through the idle thread to get out of the current context.
710 */
711 ntd = &gd->gd_idlethread;
712 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
713 ASSERT_NO_TOKENS_HELD(ntd);
714 cpu_time.cp_msg[0] = 0;
5411d8f1
MD
715 goto haveidle;
716
2a418930 717havethread:
b12defdc 718 /*
be71787b
MD
719 * Clear gd_idle_repeat when doing a normal switch to a non-idle
720 * thread.
f9235b6d 721 */
9ac1ee6e 722 ntd->td_wmesg = NULL;
7fb451cb 723 ntd->td_contended = 0; /* reset once scheduled */
b12defdc 724 ++gd->gd_cnt.v_swtch;
be71787b 725 gd->gd_idle_repeat = 0;
2a418930 726
f9235b6d 727havethread_preempted:
f9235b6d
MD
728 /*
729 * If the new target does not need the MP lock and we are holding it,
730 * release the MP lock. If the new target requires the MP lock we have
731 * already acquired it for the target.
8a8d5d85 732 */
2a418930 733 ;
f9235b6d
MD
734haveidle:
735 KASSERT(ntd->td_critcount,
b5d16701
MD
736 ("priority problem in lwkt_switch %d %d",
737 td->td_critcount, ntd->td_critcount));
738
94f6d86e 739 if (td != ntd) {
cc9b6223
MD
740 /*
741 * Execute the actual thread switch operation. This function
742 * returns to the current thread and returns the previous thread
743 * (which may be different from the thread we switched to).
744 *
745 * We are responsible for marking ntd as TDF_RUNNING.
746 */
121f93bc 747 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
94f6d86e 748 ++switch_count;
a1f0fb66 749 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
750 ntd->td_flags |= TDF_RUNNING;
751 lwkt_switch_return(td->td_switch(ntd));
752 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 753 }
b12defdc 754
b12defdc 755 /*
54341a3b 756 * catch-all. XXX is this strictly needed?
b12defdc
MD
757 */
758 splz_check();
54341a3b 759
37af14fe
MD
760 /* NOTE: current cpu may have changed after switch */
761 crit_exit_quick(td);
8ad65e08
MD
762}
763
cc9b6223
MD
764/*
765 * Called by assembly in the td_switch (thread restore path) for thread
766 * bootstrap cases which do not 'return' to lwkt_switch().
767 */
768void
769lwkt_switch_return(thread_t otd)
770{
cc9b6223
MD
771 globaldata_t rgd;
772
773 /*
774 * Check if otd was migrating. Now that we are on ntd we can finish
775 * up the migration. This is a bit messy but it is the only place
776 * where td is known to be fully descheduled.
777 *
778 * We can only activate the migration if otd was migrating but not
779 * held on the cpu due to a preemption chain. We still have to
780 * clear TDF_RUNNING on the old thread either way.
781 *
782 * We are responsible for clearing the previously running thread's
783 * TDF_RUNNING.
784 */
785 if ((rgd = otd->td_migrate_gd) != NULL &&
786 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
787 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
788 (TDF_MIGRATING | TDF_RUNNING));
789 otd->td_migrate_gd = NULL;
790 otd->td_flags &= ~TDF_RUNNING;
791 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
792 } else {
793 otd->td_flags &= ~TDF_RUNNING;
794 }
2b07d9aa
MD
795
796 /*
797 * Final exit validations (see lwp_wait()). Note that otd becomes
798 * invalid the *instant* we set TDF_MP_EXITSIG.
799 */
800 while (otd->td_flags & TDF_EXITING) {
801 u_int mpflags;
802
803 mpflags = otd->td_mpflags;
804 cpu_ccfence();
805
806 if (mpflags & TDF_MP_EXITWAIT) {
807 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
808 mpflags | TDF_MP_EXITSIG)) {
809 wakeup(otd);
810 break;
811 }
812 } else {
813 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
814 mpflags | TDF_MP_EXITSIG)) {
815 wakeup(otd);
816 break;
817 }
818 }
819 }
cc9b6223
MD
820}
821
b68b7282 822/*
96728c05 823 * Request that the target thread preempt the current thread. Preemption
54341a3b
MD
824 * can only occur if our only critical section is the one that we were called
825 * with, the relative priority of the target thread is higher, and the target
826 * thread holds no tokens. This also only works if we are not holding any
827 * spinlocks (obviously).
96728c05
MD
828 *
829 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
830 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 831 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
832 * to determine whether preemption is possible (aka usually just the crit
833 * priority of lwkt_schedule() itself).
b68b7282 834 *
54341a3b
MD
835 * Preemption is typically limited to interrupt threads.
836 *
837 * Operation works in a fairly straight-forward manner. The normal
838 * scheduling code is bypassed and we switch directly to the target
839 * thread. When the target thread attempts to block or switch away
840 * code at the base of lwkt_switch() will switch directly back to our
841 * thread. Our thread is able to retain whatever tokens it holds and
842 * if the target needs one of them the target will switch back to us
843 * and reschedule itself normally.
b68b7282
MD
844 */
845void
f9235b6d 846lwkt_preempt(thread_t ntd, int critcount)
b68b7282 847{
46a3f46d 848 struct globaldata *gd = mycpu;
cc9b6223 849 thread_t xtd;
0a3f9b47 850 thread_t td;
2d910aaf 851 int save_gd_intr_nesting_level;
b68b7282 852
26a0694b 853 /*
96728c05
MD
854 * The caller has put us in a critical section. We can only preempt
855 * if the caller of the caller was not in a critical section (basically
f9235b6d 856 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 857 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 858 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
859 *
860 * YYY The target thread must be in a critical section (else it must
861 * inherit our critical section? I dunno yet).
26a0694b 862 */
f9235b6d 863 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 864
b12defdc 865 td = gd->gd_curthread;
fbc024e4
MD
866 if (preempt_enable == 0) {
867 ++preempt_miss;
868 return;
869 }
f9235b6d 870 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
871 ++preempt_miss;
872 return;
873 }
f9235b6d 874 if (td->td_critcount > critcount) {
96728c05
MD
875 ++preempt_miss;
876 return;
877 }
121f93bc
MD
878 if (td->td_cscount) {
879 ++preempt_miss;
880 return;
881 }
46a3f46d 882 if (ntd->td_gd != gd) {
96728c05
MD
883 ++preempt_miss;
884 return;
885 }
41a01a4d 886 /*
77912481
MD
887 * We don't have to check spinlocks here as they will also bump
888 * td_critcount.
d3d1cbc8
MD
889 *
890 * Do not try to preempt if the target thread is holding any tokens.
891 * We could try to acquire the tokens but this case is so rare there
892 * is no need to support it.
41a01a4d 893 */
0846e4ce 894 KKASSERT(gd->gd_spinlocks == 0);
77912481 895
3b998fa9 896 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 897 ++preempt_miss;
d3d1cbc8
MD
898 return;
899 }
26a0694b
MD
900 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
901 ++preempt_weird;
902 return;
903 }
904 if (ntd->td_preempted) {
4b5f931b 905 ++preempt_hit;
26a0694b 906 return;
b68b7282 907 }
da0b0e8b 908 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 909
8ec60c3f
MD
910 /*
911 * Since we are able to preempt the current thread, there is no need to
912 * call need_lwkt_resched().
2d910aaf
MD
913 *
914 * We must temporarily clear gd_intr_nesting_level around the switch
915 * since switchouts from the target thread are allowed (they will just
916 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
917 *
918 * A preemption must switch back to the original thread, assert the
919 * case.
8ec60c3f 920 */
26a0694b
MD
921 ++preempt_hit;
922 ntd->td_preempted = td;
923 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 924 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
925 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
926 gd->gd_intr_nesting_level = 0;
121f93bc
MD
927
928 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
cc9b6223
MD
929 ntd->td_flags |= TDF_RUNNING;
930 xtd = td->td_switch(ntd);
931 KKASSERT(xtd == ntd);
932 lwkt_switch_return(xtd);
2d910aaf 933 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 934
26a0694b
MD
935 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
936 ntd->td_preempted = NULL;
937 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
938}
939
f1d1c3fa 940/*
faaeffac 941 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
942 * This will work inside a critical section but not inside a hard code
943 * section.
ef0fdad1 944 *
f1d1c3fa
MD
945 * (self contained on a per cpu basis)
946 */
947void
faaeffac 948splz_check(void)
f1d1c3fa 949{
7966cb69
MD
950 globaldata_t gd = mycpu;
951 thread_t td = gd->gd_curthread;
ef0fdad1 952
4a28fe22
MD
953 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
954 gd->gd_intr_nesting_level == 0 &&
955 td->td_nest_count < 2)
956 {
f1d1c3fa 957 splz();
4a28fe22
MD
958 }
959}
960
961/*
962 * This version is integrated into crit_exit, reqflags has already
963 * been tested but td_critcount has not.
964 *
965 * We only want to execute the splz() on the 1->0 transition of
966 * critcount and not in a hard code section or if too deeply nested.
925040f2 967 *
0846e4ce 968 * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0.
4a28fe22
MD
969 */
970void
971lwkt_maybe_splz(thread_t td)
972{
973 globaldata_t gd = td->td_gd;
974
975 if (td->td_critcount == 0 &&
976 gd->gd_intr_nesting_level == 0 &&
977 td->td_nest_count < 2)
978 {
979 splz();
980 }
f1d1c3fa
MD
981}
982
e6546af9
MD
983/*
984 * Drivers which set up processing co-threads can call this function to
985 * run the co-thread at a higher priority and to allow it to preempt
986 * normal threads.
987 */
988void
989lwkt_set_interrupt_support_thread(void)
990{
991 thread_t td = curthread;
992
993 lwkt_setpri_self(TDPRI_INT_SUPPORT);
994 td->td_flags |= TDF_INTTHREAD;
995 td->td_preemptable = lwkt_preempt;
996}
997
998
8ad65e08 999/*
f9235b6d
MD
1000 * This function is used to negotiate a passive release of the current
1001 * process/lwp designation with the user scheduler, allowing the user
1002 * scheduler to schedule another user thread. The related kernel thread
1003 * (curthread) continues running in the released state.
8ad65e08
MD
1004 */
1005void
f9235b6d 1006lwkt_passive_release(struct thread *td)
8ad65e08 1007{
f9235b6d
MD
1008 struct lwp *lp = td->td_lwp;
1009
1010 td->td_release = NULL;
1011 lwkt_setpri_self(TDPRI_KERN_USER);
d992c377 1012
f9235b6d 1013 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1014}
1015
f9235b6d 1016
3824f392 1017/*
d2d8515b
MD
1018 * This implements a LWKT yield, allowing a kernel thread to yield to other
1019 * kernel threads at the same or higher priority. This function can be
1020 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1021 *
d2d8515b
MD
1022 * Most kernel threads run at the same priority in order to allow equal
1023 * sharing.
f9235b6d
MD
1024 *
1025 * (self contained on a per cpu basis)
3824f392
MD
1026 */
1027void
f9235b6d 1028lwkt_yield(void)
3824f392 1029{
f9235b6d
MD
1030 globaldata_t gd = mycpu;
1031 thread_t td = gd->gd_curthread;
3824f392 1032
f9235b6d
MD
1033 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1034 splz();
85946b6c 1035 if (lwkt_resched_wanted()) {
f9235b6d
MD
1036 lwkt_schedule_self(curthread);
1037 lwkt_switch();
f9235b6d 1038 }
3824f392
MD
1039}
1040
40504122
MD
1041/*
1042 * The quick version processes pending interrupts and higher-priority
1043 * LWKT threads but will not round-robin same-priority LWKT threads.
de4d4cb0
MD
1044 *
1045 * When called while attempting to return to userland the only same-pri
1046 * threads are the ones which have already tried to become the current
1047 * user process.
40504122
MD
1048 */
1049void
1050lwkt_yield_quick(void)
1051{
1052 globaldata_t gd = mycpu;
1053 thread_t td = gd->gd_curthread;
1054
1055 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1056 splz();
1057 if (lwkt_resched_wanted()) {
9c99cb33 1058 crit_enter();
40504122
MD
1059 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1060 clear_lwkt_resched();
1061 } else {
1062 lwkt_schedule_self(curthread);
1063 lwkt_switch();
1064 }
9c99cb33 1065 crit_exit();
40504122
MD
1066 }
1067}
1068
3824f392 1069/*
f9235b6d
MD
1070 * This yield is designed for kernel threads with a user context.
1071 *
1072 * The kernel acting on behalf of the user is potentially cpu-bound,
1073 * this function will efficiently allow other threads to run and also
1074 * switch to other processes by releasing.
3824f392
MD
1075 *
1076 * The lwkt_user_yield() function is designed to have very low overhead
1077 * if no yield is determined to be needed.
1078 */
1079void
1080lwkt_user_yield(void)
1081{
f9235b6d
MD
1082 globaldata_t gd = mycpu;
1083 thread_t td = gd->gd_curthread;
1084
1085 /*
1086 * Always run any pending interrupts in case we are in a critical
1087 * section.
1088 */
1089 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1090 splz();
3824f392 1091
3824f392 1092 /*
f9235b6d
MD
1093 * Switch (which forces a release) if another kernel thread needs
1094 * the cpu, if userland wants us to resched, or if our kernel
1095 * quantum has run out.
3824f392 1096 */
f9235b6d 1097 if (lwkt_resched_wanted() ||
85946b6c 1098 user_resched_wanted())
f9235b6d 1099 {
3824f392 1100 lwkt_switch();
3824f392
MD
1101 }
1102
f9235b6d 1103#if 0
3824f392 1104 /*
f9235b6d
MD
1105 * Reacquire the current process if we are released.
1106 *
1107 * XXX not implemented atm. The kernel may be holding locks and such,
1108 * so we want the thread to continue to receive cpu.
3824f392 1109 */
f9235b6d
MD
1110 if (td->td_release == NULL && lp) {
1111 lp->lwp_proc->p_usched->acquire_curproc(lp);
1112 td->td_release = lwkt_passive_release;
1113 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1114 }
f9235b6d 1115#endif
b9eb1c19
MD
1116}
1117
8ad65e08 1118/*
f1d1c3fa
MD
1119 * Generic schedule. Possibly schedule threads belonging to other cpus and
1120 * deal with threads that might be blocked on a wait queue.
1121 *
0a3f9b47
MD
1122 * We have a little helper inline function which does additional work after
1123 * the thread has been enqueued, including dealing with preemption and
1124 * setting need_lwkt_resched() (which prevents the kernel from returning
1125 * to userland until it has processed higher priority threads).
6330a558
MD
1126 *
1127 * It is possible for this routine to be called after a failed _enqueue
1128 * (due to the target thread migrating, sleeping, or otherwise blocked).
1129 * We have to check that the thread is actually on the run queue!
8ad65e08 1130 */
0a3f9b47
MD
1131static __inline
1132void
85946b6c 1133_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1134{
6330a558 1135 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1136 if (ntd->td_preemptable) {
f9235b6d 1137 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1138 }
0a3f9b47
MD
1139 }
1140}
1141
361d01dd 1142static __inline
8ad65e08 1143void
85946b6c 1144_lwkt_schedule(thread_t td)
8ad65e08 1145{
37af14fe
MD
1146 globaldata_t mygd = mycpu;
1147
cf709dd2
MD
1148 KASSERT(td != &td->td_gd->gd_idlethread,
1149 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1150 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1151 crit_enter_gd(mygd);
4643740a
MD
1152 KKASSERT(td->td_lwp == NULL ||
1153 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1154
37af14fe 1155 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1156 _lwkt_enqueue(td);
1157 } else {
f1d1c3fa 1158 /*
7cd8d145
MD
1159 * If we own the thread, there is no race (since we are in a
1160 * critical section). If we do not own the thread there might
1161 * be a race but the target cpu will deal with it.
f1d1c3fa 1162 */
7cd8d145 1163 if (td->td_gd == mygd) {
9d265729 1164 _lwkt_enqueue(td);
85946b6c 1165 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1166 } else {
e381e77c 1167 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1168 }
8ad65e08 1169 }
37af14fe 1170 crit_exit_gd(mygd);
8ad65e08
MD
1171}
1172
361d01dd
MD
1173void
1174lwkt_schedule(thread_t td)
1175{
85946b6c 1176 _lwkt_schedule(td);
361d01dd
MD
1177}
1178
1179void
85946b6c 1180lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1181{
85946b6c 1182 _lwkt_schedule(td);
361d01dd
MD
1183}
1184
e381e77c
MD
1185/*
1186 * When scheduled remotely if frame != NULL the IPIQ is being
1187 * run via doreti or an interrupt then preemption can be allowed.
1188 *
1189 * To allow preemption we have to drop the critical section so only
1190 * one is present in _lwkt_schedule_post.
1191 */
1192static void
1193lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1194{
1195 thread_t td = curthread;
1196 thread_t ntd = arg;
1197
1198 if (frame && ntd->td_preemptable) {
1199 crit_exit_noyield(td);
85946b6c 1200 _lwkt_schedule(ntd);
e381e77c
MD
1201 crit_enter_quick(td);
1202 } else {
85946b6c 1203 _lwkt_schedule(ntd);
e381e77c
MD
1204 }
1205}
1206
d9eea1a5 1207/*
52eedfb5
MD
1208 * Thread migration using a 'Pull' method. The thread may or may not be
1209 * the current thread. It MUST be descheduled and in a stable state.
1210 * lwkt_giveaway() must be called on the cpu owning the thread.
1211 *
1212 * At any point after lwkt_giveaway() is called, the target cpu may
1213 * 'pull' the thread by calling lwkt_acquire().
1214 *
ae8e83e6
MD
1215 * We have to make sure the thread is not sitting on a per-cpu tsleep
1216 * queue or it will blow up when it moves to another cpu.
1217 *
52eedfb5 1218 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1219 */
52eedfb5
MD
1220void
1221lwkt_giveaway(thread_t td)
1222{
3b4192fb 1223 globaldata_t gd = mycpu;
52eedfb5 1224
3b4192fb
MD
1225 crit_enter_gd(gd);
1226 if (td->td_flags & TDF_TSLEEPQ)
1227 tsleep_remove(td);
1228 KKASSERT(td->td_gd == gd);
1229 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1230 td->td_flags |= TDF_MIGRATING;
1231 crit_exit_gd(gd);
52eedfb5
MD
1232}
1233
a2a5ad0d
MD
1234void
1235lwkt_acquire(thread_t td)
1236{
37af14fe
MD
1237 globaldata_t gd;
1238 globaldata_t mygd;
cc9b6223 1239 int retry = 10000000;
a2a5ad0d 1240
52eedfb5 1241 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1242 gd = td->td_gd;
37af14fe 1243 mygd = mycpu;
52eedfb5 1244 if (gd != mycpu) {
35238fa5 1245 cpu_lfence();
52eedfb5 1246 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1247 crit_enter_gd(mygd);
cfaeae2a 1248 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23 1249 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
df910c23 1250 lwkt_process_ipiq();
52eedfb5 1251 cpu_lfence();
cc9b6223
MD
1252 if (--retry == 0) {
1253 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1254 td, td->td_flags);
1255 retry = 10000000;
1256 }
a86ce0cd
MD
1257#ifdef _KERNEL_VIRTUAL
1258 pthread_yield();
1259#endif
df910c23 1260 }
cfaeae2a 1261 DEBUG_POP_INFO();
562273ea 1262 cpu_mfence();
37af14fe 1263 td->td_gd = mygd;
52eedfb5
MD
1264 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1265 td->td_flags &= ~TDF_MIGRATING;
1266 crit_exit_gd(mygd);
1267 } else {
1268 crit_enter_gd(mygd);
1269 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1270 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1271 crit_exit_gd(mygd);
a2a5ad0d
MD
1272 }
1273}
1274
f1d1c3fa
MD
1275/*
1276 * Generic deschedule. Descheduling threads other then your own should be
1277 * done only in carefully controlled circumstances. Descheduling is
1278 * asynchronous.
1279 *
1280 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1281 */
1282void
1283lwkt_deschedule(thread_t td)
1284{
f1d1c3fa
MD
1285 crit_enter();
1286 if (td == curthread) {
1287 _lwkt_dequeue(td);
1288 } else {
a72187e9 1289 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1290 _lwkt_dequeue(td);
1291 } else {
b8a98473 1292 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1293 }
1294 }
1295 crit_exit();
1296}
1297
4b5f931b
MD
1298/*
1299 * Set the target thread's priority. This routine does not automatically
1300 * switch to a higher priority thread, LWKT threads are not designed for
1301 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1302 */
1303void
1304lwkt_setpri(thread_t td, int pri)
1305{
f9235b6d
MD
1306 if (td->td_pri != pri) {
1307 KKASSERT(pri >= 0);
1308 crit_enter();
1309 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1310 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1311 _lwkt_dequeue(td);
1312 td->td_pri = pri;
1313 _lwkt_enqueue(td);
1314 } else {
1315 td->td_pri = pri;
1316 }
1317 crit_exit();
26a0694b 1318 }
26a0694b
MD
1319}
1320
03bd0a5e
MD
1321/*
1322 * Set the initial priority for a thread prior to it being scheduled for
1323 * the first time. The thread MUST NOT be scheduled before or during
1324 * this call. The thread may be assigned to a cpu other then the current
1325 * cpu.
1326 *
1327 * Typically used after a thread has been created with TDF_STOPPREQ,
1328 * and before the thread is initially scheduled.
1329 */
1330void
1331lwkt_setpri_initial(thread_t td, int pri)
1332{
1333 KKASSERT(pri >= 0);
1334 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1335 td->td_pri = pri;
03bd0a5e
MD
1336}
1337
26a0694b
MD
1338void
1339lwkt_setpri_self(int pri)
1340{
1341 thread_t td = curthread;
1342
4b5f931b
MD
1343 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1344 crit_enter();
1345 if (td->td_flags & TDF_RUNQ) {
1346 _lwkt_dequeue(td);
f9235b6d 1347 td->td_pri = pri;
4b5f931b
MD
1348 _lwkt_enqueue(td);
1349 } else {
f9235b6d 1350 td->td_pri = pri;
4b5f931b
MD
1351 }
1352 crit_exit();
1353}
1354
f9235b6d 1355/*
85946b6c 1356 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1357 */
1358void
85946b6c 1359lwkt_schedulerclock(thread_t td)
f9235b6d 1360{
85946b6c
MD
1361 globaldata_t gd = td->td_gd;
1362 thread_t xtd;
2a418930 1363
85946b6c
MD
1364 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1365 /*
1366 * If the current thread is at the head of the runq shift it to the
1367 * end of any equal-priority threads and request a LWKT reschedule
1368 * if it moved.
d992c377
MD
1369 *
1370 * Ignore upri in this situation. There will only be one user thread
1371 * in user mode, all others will be user threads running in kernel
1372 * mode and we have to make sure they get some cpu.
85946b6c
MD
1373 */
1374 xtd = TAILQ_NEXT(td, td_threadq);
1375 if (xtd && xtd->td_pri == td->td_pri) {
1376 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1377 while (xtd && xtd->td_pri == td->td_pri)
1378 xtd = TAILQ_NEXT(xtd, td_threadq);
1379 if (xtd)
1380 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1381 else
1382 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1383 need_lwkt_resched();
f9235b6d 1384 }
85946b6c
MD
1385 } else {
1386 /*
1387 * If we scheduled a thread other than the one at the head of the
1388 * queue always request a reschedule every tick.
1389 */
1390 need_lwkt_resched();
f9235b6d
MD
1391 }
1392}
1393
5d21b981 1394/*
52eedfb5
MD
1395 * Migrate the current thread to the specified cpu.
1396 *
cc9b6223
MD
1397 * This is accomplished by descheduling ourselves from the current cpu
1398 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1399 * 'old' thread wants to migrate after it has been completely switched out
1400 * and will complete the migration.
1401 *
1402 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1403 *
1404 * We must be sure to release our current process designation (if a user
1405 * process) before clearing out any tsleepq we are on because the release
1406 * code may re-add us.
ae8e83e6
MD
1407 *
1408 * We must be sure to remove ourselves from the current cpu's tsleepq
1409 * before potentially moving to another queue. The thread can be on
1410 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1411 */
5d21b981
MD
1412
1413void
1414lwkt_setcpu_self(globaldata_t rgd)
1415{
5d21b981
MD
1416 thread_t td = curthread;
1417
1418 if (td->td_gd != rgd) {
1419 crit_enter_quick(td);
cc9b6223 1420
95858b91
MD
1421 if (td->td_release)
1422 td->td_release(td);
ae8e83e6 1423 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1424 tsleep_remove(td);
cc9b6223
MD
1425
1426 /*
1427 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1428 * trying to deschedule ourselves and switch away, then deschedule
1429 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1430 * call lwkt_switch() to complete the operation.
1431 */
5d21b981
MD
1432 td->td_flags |= TDF_MIGRATING;
1433 lwkt_deschedule_self(td);
52eedfb5 1434 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1435 td->td_migrate_gd = rgd;
5d21b981 1436 lwkt_switch();
cc9b6223
MD
1437
1438 /*
1439 * We are now on the target cpu
1440 */
1441 KKASSERT(rgd == mycpu);
52eedfb5 1442 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1443 crit_exit_quick(td);
1444 }
5d21b981
MD
1445}
1446
ecdefdda
MD
1447void
1448lwkt_migratecpu(int cpuid)
1449{
ecdefdda
MD
1450 globaldata_t rgd;
1451
1452 rgd = globaldata_find(cpuid);
1453 lwkt_setcpu_self(rgd);
ecdefdda
MD
1454}
1455
5d21b981
MD
1456/*
1457 * Remote IPI for cpu migration (called while in a critical section so we
cc9b6223
MD
1458 * do not have to enter another one).
1459 *
1460 * The thread (td) has already been completely descheduled from the
1461 * originating cpu and we can simply assert the case. The thread is
1462 * assigned to the new cpu and enqueued.
5d21b981 1463 *
cc9b6223 1464 * The thread will re-add itself to tdallq when it resumes execution.
5d21b981
MD
1465 */
1466static void
1467lwkt_setcpu_remote(void *arg)
1468{
1469 thread_t td = arg;
1470 globaldata_t gd = mycpu;
1471
cc9b6223 1472 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1473 td->td_gd = gd;
562273ea 1474 cpu_mfence();
5d21b981 1475 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1476 KKASSERT(td->td_migrate_gd == NULL);
4643740a
MD
1477 KKASSERT(td->td_lwp == NULL ||
1478 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
5d21b981
MD
1479 _lwkt_enqueue(td);
1480}
1481
553ea3c8 1482struct lwp *
4b5f931b
MD
1483lwkt_preempted_proc(void)
1484{
73e4f7b9 1485 thread_t td = curthread;
4b5f931b
MD
1486 while (td->td_preempted)
1487 td = td->td_preempted;
553ea3c8 1488 return(td->td_lwp);
4b5f931b
MD
1489}
1490
99df837e
MD
1491/*
1492 * Create a kernel process/thread/whatever. It shares it's address space
1493 * with proc0 - ie: kernel only.
1494 *
d2d8515b
MD
1495 * If the cpu is not specified one will be selected. In the future
1496 * specifying a cpu of -1 will enable kernel thread migration between
1497 * cpus.
99df837e
MD
1498 */
1499int
c9e9fb21
MD
1500lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1501 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1502{
73e4f7b9 1503 thread_t td;
e2565a42 1504 __va_list ap;
99df837e 1505
d3d32139 1506 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1507 tdflags);
a2a5ad0d
MD
1508 if (tdp)
1509 *tdp = td;
709799ea 1510 cpu_set_thread_handler(td, lwkt_exit, func, arg);
99df837e
MD
1511
1512 /*
1513 * Set up arg0 for 'ps' etc
1514 */
e2565a42 1515 __va_start(ap, fmt);
379210cb 1516 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1517 __va_end(ap);
99df837e
MD
1518
1519 /*
1520 * Schedule the thread to run
1521 */
4643740a
MD
1522 if (td->td_flags & TDF_NOSTART)
1523 td->td_flags &= ~TDF_NOSTART;
ef0fdad1 1524 else
4643740a 1525 lwkt_schedule(td);
99df837e
MD
1526 return 0;
1527}
1528
1529/*
1530 * Destroy an LWKT thread. Warning! This function is not called when
1531 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1532 * uses a different reaping mechanism.
1533 */
1534void
1535lwkt_exit(void)
1536{
1537 thread_t td = curthread;
c070746a 1538 thread_t std;
8826f33a 1539 globaldata_t gd;
99df837e 1540
2883d2d8
MD
1541 /*
1542 * Do any cleanup that might block here
1543 */
99df837e 1544 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1545 kprintf("kthread %p %s has exited\n", td, td->td_comm);
2883d2d8
MD
1546 biosched_done(td);
1547 dsched_exit_thread(td);
c070746a
MD
1548
1549 /*
1550 * Get us into a critical section to interlock gd_freetd and loop
1551 * until we can get it freed.
1552 *
1553 * We have to cache the current td in gd_freetd because objcache_put()ing
1554 * it would rip it out from under us while our thread is still active.
2af9d75d
MD
1555 *
1556 * We are the current thread so of course our own TDF_RUNNING bit will
1557 * be set, so unlike the lwp reap code we don't wait for it to clear.
c070746a
MD
1558 */
1559 gd = mycpu;
37af14fe 1560 crit_enter_quick(td);
2af9d75d
MD
1561 for (;;) {
1562 if (td->td_refs) {
1563 tsleep(td, 0, "tdreap", 1);
1564 continue;
1565 }
1566 if ((std = gd->gd_freetd) != NULL) {
1567 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1568 gd->gd_freetd = NULL;
1569 objcache_put(thread_cache, std);
1570 continue;
1571 }
1572 break;
c070746a 1573 }
3b4192fb
MD
1574
1575 /*
1576 * Remove thread resources from kernel lists and deschedule us for
2883d2d8
MD
1577 * the last time. We cannot block after this point or we may end
1578 * up with a stale td on the tsleepq.
eb2adbf5
MD
1579 *
1580 * None of this may block, the critical section is the only thing
1581 * protecting tdallq and the only thing preventing new lwkt_hold()
1582 * thread refs now.
3b4192fb
MD
1583 */
1584 if (td->td_flags & TDF_TSLEEPQ)
1585 tsleep_remove(td);
37af14fe 1586 lwkt_deschedule_self(td);
e56e4dea 1587 lwkt_remove_tdallq(td);
74c9628e 1588 KKASSERT(td->td_refs == 0);
2883d2d8
MD
1589
1590 /*
1591 * Final cleanup
1592 */
1593 KKASSERT(gd->gd_freetd == NULL);
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1594 if (td->td_flags & TDF_ALLOCATED_THREAD)
1595 gd->gd_freetd = td;
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1596 cpu_thread_exit();
1597}
1598
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1599void
1600lwkt_remove_tdallq(thread_t td)
1601{
1602 KKASSERT(td->td_gd == mycpu);
1603 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1604}
1605
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1606/*
1607 * Code reduction and branch prediction improvements. Call/return
1608 * overhead on modern cpus often degenerates into 0 cycles due to
1609 * the cpu's branch prediction hardware and return pc cache. We
1610 * can take advantage of this by not inlining medium-complexity
1611 * functions and we can also reduce the branch prediction impact
1612 * by collapsing perfectly predictable branches into a single
1613 * procedure instead of duplicating it.
1614 *
1615 * Is any of this noticeable? Probably not, so I'll take the
1616 * smaller code size.
1617 */
1618void
b6468f56 1619crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1620{
b6468f56 1621 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1622}
1623
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1624void
1625crit_panic(void)
1626{
1627 thread_t td = curthread;
850634cc 1628 int lcrit = td->td_critcount;
2d93b37a 1629
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1630 td->td_critcount = 0;
1631 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1632 /* NOT REACHED */
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1633}
1634
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1635/*
1636 * Called from debugger/panic on cpus which have been stopped. We must still
b19f40a4 1637 * process the IPIQ while stopped.
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1638 *
1639 * If we are dumping also try to process any pending interrupts. This may
1640 * or may not work depending on the state of the cpu at the point it was
1641 * stopped.
1642 */
1643void
1644lwkt_smp_stopped(void)
1645{
1646 globaldata_t gd = mycpu;
1647
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1648 if (dumping) {
1649 lwkt_process_ipiq();
b19f40a4 1650 --gd->gd_intr_nesting_level;
bd8015ca 1651 splz();
b19f40a4 1652 ++gd->gd_intr_nesting_level;
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1653 } else {
1654 lwkt_process_ipiq();
1655 }
bd8015ca 1656}