kernel - Make sure thread is released before migrating
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
3b998fa9 2 * Copyright (c) 2003-2010 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
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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
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AE
75#if !defined(KTR_CTXSW)
76#define KTR_CTXSW KTR_ALL
77#endif
78KTR_INFO_MASTER(ctxsw);
a1f0fb66
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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;
f64b567c 96static __int64_t token_contention_count __debugvar = 0;
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);
88ebb169 102#endif
f9235b6d 103static void lwkt_fairq_accumulate(globaldata_t gd, thread_t td);
e381e77c 104
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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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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.");
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128#ifdef INVARIANTS
129SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW,
130 &token_contention_count, 0, "spinning due to token contention");
38717797 131#endif
f9235b6d 132static int fairq_enable = 1;
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133SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
134 &fairq_enable, 0, "Turn on fairq priority accumulators");
135static int lwkt_spin_loops = 10;
136SYSCTL_INT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
137 &lwkt_spin_loops, 0, "");
138static int lwkt_spin_delay = 1;
139SYSCTL_INT(_lwkt, OID_AUTO, spin_delay, CTLFLAG_RW,
140 &lwkt_spin_delay, 0, "Scheduler spin delay in microseconds 0=auto");
141static int lwkt_spin_method = 1;
142SYSCTL_INT(_lwkt, OID_AUTO, spin_method, CTLFLAG_RW,
143 &lwkt_spin_method, 0, "LWKT scheduler behavior when contended");
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144static int lwkt_spin_fatal = 0; /* disabled */
145SYSCTL_INT(_lwkt, OID_AUTO, spin_fatal, CTLFLAG_RW,
146 &lwkt_spin_fatal, 0, "LWKT scheduler spin loops till fatal panic");
fbc024e4 147static int preempt_enable = 1;
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148SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
149 &preempt_enable, 0, "Enable preemption");
fbc024e4 150
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151static __cachealign int lwkt_cseq_rindex;
152static __cachealign int lwkt_cseq_windex;
05220613 153
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154/*
155 * These helper procedures handle the runq, they can only be called from
156 * within a critical section.
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157 *
158 * WARNING! Prior to SMP being brought up it is possible to enqueue and
159 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
160 * instead of 'mycpu' when referencing the globaldata structure. Once
161 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 162 */
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163static __inline
164void
165_lwkt_dequeue(thread_t td)
166{
167 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 168 struct globaldata *gd = td->td_gd;
4b5f931b 169
f1d1c3fa 170 td->td_flags &= ~TDF_RUNQ;
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171 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
172 gd->gd_fairq_total_pri -= td->td_pri;
173 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 174 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
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175 }
176}
177
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178/*
179 * Priority enqueue.
180 *
181 * NOTE: There are a limited number of lwkt threads runnable since user
182 * processes only schedule one at a time per cpu.
183 */
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184static __inline
185void
186_lwkt_enqueue(thread_t td)
187{
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188 thread_t xtd;
189
7f5d7ed7 190 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 191 struct globaldata *gd = td->td_gd;
4b5f931b 192
f1d1c3fa 193 td->td_flags |= TDF_RUNQ;
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194 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
195 if (xtd == NULL) {
196 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
2a418930 197 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
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198 } else {
199 while (xtd && xtd->td_pri > td->td_pri)
200 xtd = TAILQ_NEXT(xtd, td_threadq);
201 if (xtd)
202 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
203 else
204 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
205 }
206 gd->gd_fairq_total_pri += td->td_pri;
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207 }
208}
8ad65e08 209
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210static __boolean_t
211_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
212{
213 struct thread *td = (struct thread *)obj;
214
215 td->td_kstack = NULL;
216 td->td_kstack_size = 0;
217 td->td_flags = TDF_ALLOCATED_THREAD;
218 return (1);
219}
220
221static void
222_lwkt_thread_dtor(void *obj, void *privdata)
223{
224 struct thread *td = (struct thread *)obj;
225
226 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
227 ("_lwkt_thread_dtor: not allocated from objcache"));
228 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
229 td->td_kstack_size > 0,
230 ("_lwkt_thread_dtor: corrupted stack"));
231 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
232}
233
234/*
235 * Initialize the lwkt s/system.
236 */
237void
238lwkt_init(void)
239{
240 /* An objcache has 2 magazines per CPU so divide cache size by 2. */
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241 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread),
242 NULL, CACHE_NTHREADS/2,
243 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
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244}
245
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246/*
247 * Schedule a thread to run. As the current thread we can always safely
248 * schedule ourselves, and a shortcut procedure is provided for that
249 * function.
250 *
251 * (non-blocking, self contained on a per cpu basis)
252 */
253void
254lwkt_schedule_self(thread_t td)
255{
cfaeae2a 256 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 257 crit_enter_quick(td);
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258 KASSERT(td != &td->td_gd->gd_idlethread,
259 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
9388413d 260 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 261 _lwkt_enqueue(td);
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262 crit_exit_quick(td);
263}
264
265/*
266 * Deschedule a thread.
267 *
268 * (non-blocking, self contained on a per cpu basis)
269 */
270void
271lwkt_deschedule_self(thread_t td)
272{
273 crit_enter_quick(td);
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274 _lwkt_dequeue(td);
275 crit_exit_quick(td);
276}
277
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278/*
279 * LWKTs operate on a per-cpu basis
280 *
73e4f7b9 281 * WARNING! Called from early boot, 'mycpu' may not work yet.
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282 */
283void
284lwkt_gdinit(struct globaldata *gd)
285{
f9235b6d 286 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 287 TAILQ_INIT(&gd->gd_tdallq);
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288}
289
290/*
7d0bac62 291 * Create a new thread. The thread must be associated with a process context
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292 * or LWKT start address before it can be scheduled. If the target cpu is
293 * -1 the thread will be created on the current cpu.
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294 *
295 * If you intend to create a thread without a process context this function
296 * does everything except load the startup and switcher function.
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297 */
298thread_t
d3d32139 299lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 300{
c070746a 301 globaldata_t gd = mycpu;
99df837e 302 void *stack;
7d0bac62 303
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304 /*
305 * If static thread storage is not supplied allocate a thread. Reuse
306 * a cached free thread if possible. gd_freetd is used to keep an exiting
307 * thread intact through the exit.
308 */
ef0fdad1 309 if (td == NULL) {
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MD
310 crit_enter_gd(gd);
311 if ((td = gd->gd_freetd) != NULL) {
312 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
313 TDF_RUNQ)) == 0);
c070746a 314 gd->gd_freetd = NULL;
cf709dd2 315 } else {
c070746a 316 td = objcache_get(thread_cache, M_WAITOK);
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317 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
318 TDF_RUNQ)) == 0);
319 }
320 crit_exit_gd(gd);
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321 KASSERT((td->td_flags &
322 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD,
323 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
324 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 325 }
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326
327 /*
328 * Try to reuse cached stack.
329 */
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330 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
331 if (flags & TDF_ALLOCATED_STACK) {
e4846942 332 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
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333 stack = NULL;
334 }
335 }
336 if (stack == NULL) {
e40cfbd7 337 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 338 flags |= TDF_ALLOCATED_STACK;
99df837e 339 }
75cdbe6c 340 if (cpu < 0)
c070746a 341 lwkt_init_thread(td, stack, stksize, flags, gd);
75cdbe6c 342 else
f470d0c8 343 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 344 return(td);
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345}
346
347/*
348 * Initialize a preexisting thread structure. This function is used by
349 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
350 *
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351 * All threads start out in a critical section at a priority of
352 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
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353 * appropriate. This function may send an IPI message when the
354 * requested cpu is not the current cpu and consequently gd_tdallq may
355 * not be initialized synchronously from the point of view of the originating
356 * cpu.
357 *
358 * NOTE! we have to be careful in regards to creating threads for other cpus
359 * if SMP has not yet been activated.
7d0bac62 360 */
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361#ifdef SMP
362
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363static void
364lwkt_init_thread_remote(void *arg)
365{
366 thread_t td = arg;
367
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368 /*
369 * Protected by critical section held by IPI dispatch
370 */
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371 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
372}
373
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374#endif
375
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376/*
377 * lwkt core thread structural initialization.
378 *
379 * NOTE: All threads are initialized as mpsafe threads.
380 */
7d0bac62 381void
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382lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
383 struct globaldata *gd)
7d0bac62 384{
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385 globaldata_t mygd = mycpu;
386
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387 bzero(td, sizeof(struct thread));
388 td->td_kstack = stack;
f470d0c8 389 td->td_kstack_size = stksize;
d3d32139 390 td->td_flags = flags;
26a0694b 391 td->td_gd = gd;
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392 td->td_pri = TDPRI_KERN_DAEMON;
393 td->td_critcount = 1;
3b998fa9 394 td->td_toks_stop = &td->td_toks_base;
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395 if (lwkt_use_spin_port)
396 lwkt_initport_spin(&td->td_msgport);
397 else
398 lwkt_initport_thread(&td->td_msgport, td);
99df837e 399 pmap_init_thread(td);
0f7a3396 400#ifdef SMP
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401 /*
402 * Normally initializing a thread for a remote cpu requires sending an
403 * IPI. However, the idlethread is setup before the other cpus are
404 * activated so we have to treat it as a special case. XXX manipulation
405 * of gd_tdallq requires the BGL.
406 */
407 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 408 crit_enter_gd(mygd);
75cdbe6c 409 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 410 crit_exit_gd(mygd);
75cdbe6c 411 } else {
2db3b277 412 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 413 }
0f7a3396 414#else
37af14fe 415 crit_enter_gd(mygd);
0f7a3396 416 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 417 crit_exit_gd(mygd);
0f7a3396 418#endif
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419
420 dsched_new_thread(td);
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421}
422
423void
424lwkt_set_comm(thread_t td, const char *ctl, ...)
425{
e2565a42 426 __va_list va;
73e4f7b9 427
e2565a42 428 __va_start(va, ctl);
379210cb 429 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 430 __va_end(va);
e7c0dbba 431 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]);
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432}
433
99df837e 434void
73e4f7b9 435lwkt_hold(thread_t td)
99df837e 436{
74c9628e 437 atomic_add_int(&td->td_refs, 1);
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438}
439
440void
441lwkt_rele(thread_t td)
442{
443 KKASSERT(td->td_refs > 0);
74c9628e 444 atomic_add_int(&td->td_refs, -1);
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445}
446
447void
448lwkt_wait_free(thread_t td)
449{
450 while (td->td_refs)
377d4740 451 tsleep(td, 0, "tdreap", hz);
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452}
453
454void
455lwkt_free_thread(thread_t td)
456{
74c9628e 457 KKASSERT(td->td_refs == 0);
cf709dd2 458 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|TDF_RUNQ)) == 0);
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459 if (td->td_flags & TDF_ALLOCATED_THREAD) {
460 objcache_put(thread_cache, td);
461 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
462 /* client-allocated struct with internally allocated stack */
463 KASSERT(td->td_kstack && td->td_kstack_size > 0,
464 ("lwkt_free_thread: corrupted stack"));
465 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
466 td->td_kstack = NULL;
467 td->td_kstack_size = 0;
99df837e 468 }
e7c0dbba 469 KTR_LOG(ctxsw_deadtd, td);
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470}
471
472
7d0bac62 473/*
8ad65e08 474 * Switch to the next runnable lwkt. If no LWKTs are runnable then
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475 * switch to the idlethread. Switching must occur within a critical
476 * section to avoid races with the scheduling queue.
477 *
478 * We always have full control over our cpu's run queue. Other cpus
479 * that wish to manipulate our queue must use the cpu_*msg() calls to
480 * talk to our cpu, so a critical section is all that is needed and
481 * the result is very, very fast thread switching.
482 *
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483 * The LWKT scheduler uses a fixed priority model and round-robins at
484 * each priority level. User process scheduling is a totally
485 * different beast and LWKT priorities should not be confused with
486 * user process priorities.
f1d1c3fa 487 *
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488 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
489 * is not called by the current thread in the preemption case, only when
490 * the preempting thread blocks (in order to return to the original thread).
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491 *
492 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
493 * migration and tsleep deschedule the current lwkt thread and call
494 * lwkt_switch(). In particular, the target cpu of the migration fully
495 * expects the thread to become non-runnable and can deadlock against
496 * cpusync operations if we run any IPIs prior to switching the thread out.
497 *
498 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 499 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
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500 */
501void
502lwkt_switch(void)
503{
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504 globaldata_t gd = mycpu;
505 thread_t td = gd->gd_curthread;
8ad65e08 506 thread_t ntd;
f9235b6d 507 thread_t xtd;
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508 int spinning = lwkt_spin_loops; /* loops before HLTing */
509 int reqflags;
510 int cseq;
0f0466c0 511 int oseq;
d5b2d319 512 int fatal_count;
8ad65e08 513
46a3f46d 514 /*
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MD
515 * Switching from within a 'fast' (non thread switched) interrupt or IPI
516 * is illegal. However, we may have to do it anyway if we hit a fatal
517 * kernel trap or we have paniced.
518 *
519 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 520 */
27e88a6e
MD
521 if (gd->gd_intr_nesting_level) {
522 int savegdnest;
523 int savegdtrap;
524
5fddbda2 525 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22
MD
526 panic("lwkt_switch: Attempt to switch from a "
527 "a fast interrupt, ipi, or hard code section, "
528 "td %p\n",
529 td);
27e88a6e
MD
530 } else {
531 savegdnest = gd->gd_intr_nesting_level;
532 savegdtrap = gd->gd_trap_nesting_level;
533 gd->gd_intr_nesting_level = 0;
534 gd->gd_trap_nesting_level = 0;
a7422615
MD
535 if ((td->td_flags & TDF_PANICWARN) == 0) {
536 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
537 kprintf("Warning: thread switch from interrupt, IPI, "
538 "or hard code section.\n"
a7422615 539 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 540 print_backtrace(-1);
a7422615 541 }
27e88a6e
MD
542 lwkt_switch();
543 gd->gd_intr_nesting_level = savegdnest;
544 gd->gd_trap_nesting_level = savegdtrap;
545 return;
546 }
96728c05 547 }
ef0fdad1 548
cb973d15
MD
549 /*
550 * Passive release (used to transition from user to kernel mode
551 * when we block or switch rather then when we enter the kernel).
552 * This function is NOT called if we are switching into a preemption
553 * or returning from a preemption. Typically this causes us to lose
0a3f9b47
MD
554 * our current process designation (if we have one) and become a true
555 * LWKT thread, and may also hand the current process designation to
556 * another process and schedule thread.
cb973d15
MD
557 */
558 if (td->td_release)
559 td->td_release(td);
560
37af14fe 561 crit_enter_gd(gd);
3b998fa9 562 if (TD_TOKS_HELD(td))
9d265729
MD
563 lwkt_relalltokens(td);
564
565 /*
b02926de
MD
566 * We had better not be holding any spin locks, but don't get into an
567 * endless panic loop.
9d265729 568 */
d666840a
MD
569 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
570 ("lwkt_switch: still holding %d exclusive spinlocks!",
571 gd->gd_spinlocks_wr));
9d265729 572
8a8d5d85
MD
573
574#ifdef SMP
0f7a3396
MD
575#ifdef INVARIANTS
576 if (td->td_cscount) {
6ea70f76 577 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
578 td);
579 if (panic_on_cscount)
580 panic("switching while mastering cpusync");
581 }
582#endif
8a8d5d85 583#endif
f9235b6d
MD
584
585 /*
586 * If we had preempted another thread on this cpu, resume the preempted
587 * thread. This occurs transparently, whether the preempted thread
588 * was scheduled or not (it may have been preempted after descheduling
589 * itself).
590 *
591 * We have to setup the MP lock for the original thread after backing
592 * out the adjustment that was made to curthread when the original
593 * was preempted.
594 */
99df837e 595 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
596 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
597 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
598
599 /*
b9eb1c19
MD
600 * The interrupt may have woken a thread up, we need to properly
601 * set the reschedule flag if the originally interrupted thread is
602 * at a lower priority.
8ec60c3f 603 */
f9235b6d
MD
604 if (TAILQ_FIRST(&gd->gd_tdrunq) &&
605 TAILQ_FIRST(&gd->gd_tdrunq)->td_pri > ntd->td_pri) {
8ec60c3f 606 need_lwkt_resched();
f9235b6d 607 }
8a8d5d85 608 /* YYY release mp lock on switchback if original doesn't need it */
f9235b6d
MD
609 goto havethread_preempted;
610 }
611
612 /*
613 * Implement round-robin fairq with priority insertion. The priority
614 * insertion is handled by _lwkt_enqueue()
615 *
f9235b6d 616 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
617 * schedule the target thread.
618 *
619 * Reminder: Again, we cannot afford to run any IPIs in this path if
620 * the current thread has been descheduled.
f9235b6d
MD
621 */
622 for (;;) {
2a418930
MD
623 /*
624 * Clear RQF_AST_LWKT_RESCHED (we handle the reschedule request)
625 * and set RQF_WAKEUP (prevent unnecessary IPIs from being
626 * received).
627 */
628 for (;;) {
629 reqflags = gd->gd_reqflags;
630 if (atomic_cmpset_int(&gd->gd_reqflags, reqflags,
631 (reqflags & ~RQF_AST_LWKT_RESCHED) |
632 RQF_WAKEUP)) {
633 break;
634 }
635 }
f9235b6d 636
4b5f931b 637 /*
2a418930
MD
638 * Hotpath - pull the head of the run queue and attempt to schedule
639 * it. Fairq exhaustion moves the task to the end of the list. If
640 * no threads are runnable we switch to the idle thread.
41a01a4d 641 */
2a418930
MD
642 for (;;) {
643 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
644
645 if (ntd == NULL) {
646 /*
647 * Runq is empty, switch to idle and clear RQF_WAKEUP
648 * to allow it to halt.
649 */
650 ntd = &gd->gd_idlethread;
6f207a2c 651#ifdef SMP
2a418930 652 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
b5d16701 653 ASSERT_NO_TOKENS_HELD(ntd);
6f207a2c 654#endif
2a418930
MD
655 cpu_time.cp_msg[0] = 0;
656 cpu_time.cp_stallpc = 0;
657 atomic_clear_int(&gd->gd_reqflags, RQF_WAKEUP);
658 goto haveidle;
659 }
660
661 if (ntd->td_fairq_accum >= 0)
662 break;
663
cfaeae2a 664 /*splz_check(); cannot do this here, see above */
2a418930
MD
665 lwkt_fairq_accumulate(gd, ntd);
666 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq);
667 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, ntd, td_threadq);
f9235b6d 668 }
41a01a4d
MD
669
670 /*
2a418930
MD
671 * Hotpath - schedule ntd. Leaves RQF_WAKEUP set to prevent
672 * unwanted decontention IPIs.
6f207a2c
MD
673 *
674 * NOTE: For UP there is no mplock and lwkt_getalltokens()
675 * always succeeds.
8ec60c3f 676 */
2a418930 677 if (TD_TOKS_NOT_HELD(ntd) || lwkt_getalltokens(ntd))
f9235b6d 678 goto havethread;
f9235b6d 679
f9235b6d 680 /*
2a418930
MD
681 * Coldpath (SMP only since tokens always succeed on UP)
682 *
683 * We had some contention on the thread we wanted to schedule.
684 * What we do now is try to find a thread that we can schedule
685 * in its stead until decontention reschedules on our cpu.
686 *
687 * The coldpath scan does NOT rearrange threads in the run list
688 * and it also ignores the accumulator.
689 *
690 * We do not immediately schedule a user priority thread, instead
691 * we record it in xtd and continue looking for kernel threads.
692 * A cpu can only have one user priority thread (normally) so just
693 * record the first one.
694 *
695 * NOTE: This scan will also include threads whos fairq's were
696 * accumulated in the first loop.
f9235b6d 697 */
2a418930
MD
698 ++token_contention_count;
699 xtd = NULL;
700 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
41a01a4d 701 /*
2a418930
MD
702 * Try to switch to this thread. If the thread is running at
703 * user priority we clear WAKEUP to allow decontention IPIs
704 * (since this thread is simply running until the one we wanted
705 * decontends), and we make sure that LWKT_RESCHED is not set.
df6b8ba0 706 *
2a418930
MD
707 * Otherwise for kernel threads we leave WAKEUP set to avoid
708 * unnecessary decontention IPIs.
41a01a4d 709 */
2a418930
MD
710 if (ntd->td_pri < TDPRI_KERN_LPSCHED) {
711 if (xtd == NULL)
712 xtd = ntd;
713 continue;
f9235b6d 714 }
a453459d 715
f9235b6d 716 /*
2a418930
MD
717 * Do not let the fairq get too negative. Even though we are
718 * ignoring it atm once the scheduler decontends a very negative
719 * thread will get moved to the end of the queue.
f9235b6d 720 */
2a418930
MD
721 if (TD_TOKS_NOT_HELD(ntd) || lwkt_getalltokens(ntd)) {
722 if (ntd->td_fairq_accum < -TDFAIRQ_MAX(gd))
723 ntd->td_fairq_accum = -TDFAIRQ_MAX(gd);
724 goto havethread;
8a8d5d85 725 }
f9235b6d 726
df6b8ba0 727 /*
2a418930 728 * Well fubar, this thread is contended as well, loop
df6b8ba0 729 */
2a418930
MD
730 /* */
731 }
732
733 /*
734 * We exhausted the run list but we may have recorded a user
735 * thread to try. We have three choices based on
736 * lwkt.decontention_method.
737 *
738 * (0) Atomically clear RQF_WAKEUP in order to receive decontention
739 * IPIs (to interrupt the user process) and test
740 * RQF_AST_LWKT_RESCHED at the same time.
741 *
742 * This results in significant decontention IPI traffic but may
743 * be more responsive.
744 *
745 * (1) Leave RQF_WAKEUP set so we do not receive a decontention IPI.
746 * An automatic LWKT reschedule will occur on the next hardclock
747 * (typically 100hz).
748 *
749 * This results in no decontention IPI traffic but may be less
750 * responsive. This is the default.
751 *
752 * (2) Refuse to schedule the user process at this time.
753 *
754 * This is highly experimental and should not be used under
755 * normal circumstances. This can cause a user process to
756 * get starved out in situations where kernel threads are
757 * fighting each other for tokens.
758 */
759 if (xtd) {
760 ntd = xtd;
761
762 switch(lwkt_spin_method) {
763 case 0:
764 for (;;) {
765 reqflags = gd->gd_reqflags;
766 if (atomic_cmpset_int(&gd->gd_reqflags,
767 reqflags,
768 reqflags & ~RQF_WAKEUP)) {
769 break;
770 }
771 }
772 break;
773 case 1:
774 reqflags = gd->gd_reqflags;
775 break;
776 default:
777 goto skip;
778 break;
779 }
780 if ((reqflags & RQF_AST_LWKT_RESCHED) == 0 &&
b5d16701 781 (TD_TOKS_NOT_HELD(ntd) || lwkt_getalltokens(ntd))
f9235b6d 782 ) {
2a418930
MD
783 if (ntd->td_fairq_accum < -TDFAIRQ_MAX(gd))
784 ntd->td_fairq_accum = -TDFAIRQ_MAX(gd);
785 goto havethread;
df6b8ba0 786 }
9ac1ee6e 787
2a418930 788skip:
9ac1ee6e 789 /*
2a418930
MD
790 * Make sure RQF_WAKEUP is set if we failed to schedule the
791 * user thread to prevent the idle thread from halting.
9ac1ee6e 792 */
2a418930
MD
793 atomic_set_int(&gd->gd_reqflags, RQF_WAKEUP);
794 }
795
796 /*
797 * We exhausted the run list, meaning that all runnable threads
798 * are contended.
799 */
800 cpu_pause();
801 ntd = &gd->gd_idlethread;
802#ifdef SMP
803 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
804 ASSERT_NO_TOKENS_HELD(ntd);
805 /* contention case, do not clear contention mask */
806#endif
807
808 /*
809 * Ok, we might want to spin a few times as some tokens are held for
810 * very short periods of time and IPI overhead is 1uS or worse
811 * (meaning it is usually better to spin). Regardless we have to
812 * call splz_check() to be sure to service any interrupts blocked
813 * by our critical section, otherwise we could livelock e.g. IPIs.
814 *
815 * The IPI mechanic is really a last resort. In nearly all other
816 * cases RQF_WAKEUP is left set to prevent decontention IPIs.
817 *
818 * When we decide not to spin we clear RQF_WAKEUP and switch to
819 * the idle thread. Clearing RQF_WEAKEUP allows the idle thread
820 * to halt and decontended tokens will issue an IPI to us. The
821 * idle thread will check for pending reschedules already set
822 * (RQF_AST_LWKT_RESCHED) before actually halting so we don't have
823 * to here.
cfaeae2a
MD
824 *
825 * Also, if TDF_RUNQ is not set the current thread is trying to
826 * deschedule, possibly in an atomic fashion. We cannot afford to
827 * stay here.
2a418930 828 */
cfaeae2a 829 if (spinning <= 0 || (td->td_flags & TDF_RUNQ) == 0) {
2a418930
MD
830 atomic_clear_int(&gd->gd_reqflags, RQF_WAKEUP);
831 goto haveidle;
4b5f931b 832 }
2a418930 833 --spinning;
c5724852
MD
834
835 /*
2a418930
MD
836 * When spinning a delay is required both to avoid livelocks from
837 * token order reversals (a thread may be trying to acquire multiple
838 * tokens), and also to reduce cpu cache management traffic.
839 *
840 * In order to scale to a large number of CPUs we use a time slot
841 * resequencer to force contending cpus into non-contending
842 * time-slots. The scheduler may still contend with the lock holder
843 * but will not (generally) contend with all the other cpus trying
844 * trying to get the same token.
845 *
846 * The resequencer uses a FIFO counter mechanic. The owner of the
847 * rindex at the head of the FIFO is allowed to pull itself off
848 * the FIFO and fetchadd is used to enter into the FIFO. This bit
849 * of code is VERY cache friendly and forces all spinning schedulers
850 * into their own time slots.
c5724852 851 *
2a418930
MD
852 * This code has been tested to 48-cpus and caps the cache
853 * contention load at ~1uS intervals regardless of the number of
854 * cpus. Scaling beyond 64 cpus might require additional smarts
855 * (such as separate FIFOs for specific token cases).
856 *
857 * WARNING! We can't call splz_check() or anything else here as
858 * it could cause a deadlock.
c5724852 859 */
bd52bedf 860#if defined(INVARIANTS) && defined(__amd64__)
d5b2d319
MD
861 if ((read_rflags() & PSL_I) == 0) {
862 cpu_enable_intr();
863 panic("lwkt_switch() called with interrupts disabled");
864 }
865#endif
2a418930 866 cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
d5b2d319 867 fatal_count = lwkt_spin_fatal;
0f0466c0
MD
868 while ((oseq = lwkt_cseq_rindex) != cseq) {
869 cpu_ccfence();
8b402283 870#if !defined(_KERNEL_VIRTUAL)
0f0466c0
MD
871 if (cpu_mi_feature & CPU_MI_MONITOR) {
872 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq);
8b402283
SW
873 } else
874#endif
875 {
0f0466c0
MD
876 DELAY(1);
877 cpu_lfence();
878 }
d5b2d319
MD
879 if (fatal_count && --fatal_count == 0)
880 panic("lwkt_switch: fatal spin wait");
2a418930
MD
881 }
882 cseq = lwkt_spin_delay; /* don't trust the system operator */
883 cpu_ccfence();
884 if (cseq < 1)
885 cseq = 1;
886 if (cseq > 1000)
887 cseq = 1000;
888 DELAY(cseq);
889 atomic_add_int(&lwkt_cseq_rindex, 1);
cfaeae2a 890 splz_check(); /* ok, we already checked that td is still scheduled */
2a418930 891 /* highest level for(;;) loop */
f1d1c3fa 892 }
8a8d5d85 893
2a418930 894havethread:
8a8d5d85 895 /*
f9235b6d
MD
896 * We must always decrement td_fairq_accum on non-idle threads just
897 * in case a thread never gets a tick due to being in a continuous
2a418930 898 * critical section. The page-zeroing code does this, for example.
f9235b6d
MD
899 *
900 * If the thread we came up with is a higher or equal priority verses
901 * the thread at the head of the queue we move our thread to the
902 * front. This way we can always check the front of the queue.
be71787b
MD
903 *
904 * Clear gd_idle_repeat when doing a normal switch to a non-idle
905 * thread.
f9235b6d 906 */
f9235b6d
MD
907 ++gd->gd_cnt.v_swtch;
908 --ntd->td_fairq_accum;
9ac1ee6e 909 ntd->td_wmesg = NULL;
f9235b6d
MD
910 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
911 if (ntd != xtd && ntd->td_pri >= xtd->td_pri) {
912 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq);
913 TAILQ_INSERT_HEAD(&gd->gd_tdrunq, ntd, td_threadq);
914 }
be71787b 915 gd->gd_idle_repeat = 0;
2a418930 916
f9235b6d 917havethread_preempted:
f9235b6d
MD
918 /*
919 * If the new target does not need the MP lock and we are holding it,
920 * release the MP lock. If the new target requires the MP lock we have
921 * already acquired it for the target.
8a8d5d85 922 */
2a418930 923 ;
f9235b6d
MD
924haveidle:
925 KASSERT(ntd->td_critcount,
b5d16701
MD
926 ("priority problem in lwkt_switch %d %d",
927 td->td_critcount, ntd->td_critcount));
928
94f6d86e
MD
929 if (td != ntd) {
930 ++switch_count;
a1f0fb66 931 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
f1d1c3fa 932 td->td_switch(ntd);
94f6d86e 933 }
37af14fe
MD
934 /* NOTE: current cpu may have changed after switch */
935 crit_exit_quick(td);
8ad65e08
MD
936}
937
f1d1c3fa 938/*
96728c05
MD
939 * Request that the target thread preempt the current thread. Preemption
940 * only works under a specific set of conditions:
b68b7282 941 *
96728c05
MD
942 * - We are not preempting ourselves
943 * - The target thread is owned by the current cpu
944 * - We are not currently being preempted
945 * - The target is not currently being preempted
d3d1cbc8
MD
946 * - We are not holding any spin locks
947 * - The target thread is not holding any tokens
96728c05
MD
948 * - We are able to satisfy the target's MP lock requirements (if any).
949 *
950 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
951 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 952 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
953 * to determine whether preemption is possible (aka usually just the crit
954 * priority of lwkt_schedule() itself).
b68b7282 955 *
26a0694b
MD
956 * XXX at the moment we run the target thread in a critical section during
957 * the preemption in order to prevent the target from taking interrupts
958 * that *WE* can't. Preemption is strictly limited to interrupt threads
959 * and interrupt-like threads, outside of a critical section, and the
960 * preempted source thread will be resumed the instant the target blocks
961 * whether or not the source is scheduled (i.e. preemption is supposed to
962 * be as transparent as possible).
b68b7282
MD
963 */
964void
f9235b6d 965lwkt_preempt(thread_t ntd, int critcount)
b68b7282 966{
46a3f46d 967 struct globaldata *gd = mycpu;
0a3f9b47 968 thread_t td;
2d910aaf 969 int save_gd_intr_nesting_level;
b68b7282 970
26a0694b 971 /*
96728c05
MD
972 * The caller has put us in a critical section. We can only preempt
973 * if the caller of the caller was not in a critical section (basically
f9235b6d 974 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 975 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 976 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
977 *
978 * YYY The target thread must be in a critical section (else it must
979 * inherit our critical section? I dunno yet).
41a01a4d 980 *
0a3f9b47 981 * Set need_lwkt_resched() unconditionally for now YYY.
26a0694b 982 */
f9235b6d 983 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 984
fbc024e4
MD
985 if (preempt_enable == 0) {
986 ++preempt_miss;
987 return;
988 }
989
0a3f9b47 990 td = gd->gd_curthread;
f9235b6d 991 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
992 ++preempt_miss;
993 return;
994 }
f9235b6d 995 if (td->td_critcount > critcount) {
96728c05 996 ++preempt_miss;
8ec60c3f 997 need_lwkt_resched();
96728c05
MD
998 return;
999 }
1000#ifdef SMP
46a3f46d 1001 if (ntd->td_gd != gd) {
96728c05 1002 ++preempt_miss;
8ec60c3f 1003 need_lwkt_resched();
96728c05
MD
1004 return;
1005 }
1006#endif
41a01a4d 1007 /*
77912481
MD
1008 * We don't have to check spinlocks here as they will also bump
1009 * td_critcount.
d3d1cbc8
MD
1010 *
1011 * Do not try to preempt if the target thread is holding any tokens.
1012 * We could try to acquire the tokens but this case is so rare there
1013 * is no need to support it.
41a01a4d 1014 */
77912481
MD
1015 KKASSERT(gd->gd_spinlocks_wr == 0);
1016
3b998fa9 1017 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8
MD
1018 ++preempt_miss;
1019 need_lwkt_resched();
1020 return;
1021 }
26a0694b
MD
1022 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1023 ++preempt_weird;
8ec60c3f 1024 need_lwkt_resched();
26a0694b
MD
1025 return;
1026 }
1027 if (ntd->td_preempted) {
4b5f931b 1028 ++preempt_hit;
8ec60c3f 1029 need_lwkt_resched();
26a0694b 1030 return;
b68b7282 1031 }
26a0694b 1032
8ec60c3f
MD
1033 /*
1034 * Since we are able to preempt the current thread, there is no need to
1035 * call need_lwkt_resched().
2d910aaf
MD
1036 *
1037 * We must temporarily clear gd_intr_nesting_level around the switch
1038 * since switchouts from the target thread are allowed (they will just
1039 * return to our thread), and since the target thread has its own stack.
8ec60c3f 1040 */
26a0694b
MD
1041 ++preempt_hit;
1042 ntd->td_preempted = td;
1043 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1044 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1045 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1046 gd->gd_intr_nesting_level = 0;
26a0694b 1047 td->td_switch(ntd);
2d910aaf 1048 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1049
26a0694b
MD
1050 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1051 ntd->td_preempted = NULL;
1052 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1053}
1054
1055/*
faaeffac 1056 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1057 * This will work inside a critical section but not inside a hard code
1058 * section.
ef0fdad1 1059 *
f1d1c3fa
MD
1060 * (self contained on a per cpu basis)
1061 */
1062void
faaeffac 1063splz_check(void)
f1d1c3fa 1064{
7966cb69
MD
1065 globaldata_t gd = mycpu;
1066 thread_t td = gd->gd_curthread;
ef0fdad1 1067
4a28fe22
MD
1068 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1069 gd->gd_intr_nesting_level == 0 &&
1070 td->td_nest_count < 2)
1071 {
f1d1c3fa 1072 splz();
4a28fe22
MD
1073 }
1074}
1075
1076/*
1077 * This version is integrated into crit_exit, reqflags has already
1078 * been tested but td_critcount has not.
1079 *
1080 * We only want to execute the splz() on the 1->0 transition of
1081 * critcount and not in a hard code section or if too deeply nested.
1082 */
1083void
1084lwkt_maybe_splz(thread_t td)
1085{
1086 globaldata_t gd = td->td_gd;
1087
1088 if (td->td_critcount == 0 &&
1089 gd->gd_intr_nesting_level == 0 &&
1090 td->td_nest_count < 2)
1091 {
1092 splz();
1093 }
f1d1c3fa
MD
1094}
1095
8ad65e08 1096/*
f9235b6d
MD
1097 * This function is used to negotiate a passive release of the current
1098 * process/lwp designation with the user scheduler, allowing the user
1099 * scheduler to schedule another user thread. The related kernel thread
1100 * (curthread) continues running in the released state.
8ad65e08
MD
1101 */
1102void
f9235b6d 1103lwkt_passive_release(struct thread *td)
8ad65e08 1104{
f9235b6d
MD
1105 struct lwp *lp = td->td_lwp;
1106
1107 td->td_release = NULL;
1108 lwkt_setpri_self(TDPRI_KERN_USER);
1109 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1110}
1111
f9235b6d 1112
f1d1c3fa 1113/*
f9235b6d
MD
1114 * This implements a normal yield. This routine is virtually a nop if
1115 * there is nothing to yield to but it will always run any pending interrupts
1116 * if called from a critical section.
1117 *
1118 * This yield is designed for kernel threads without a user context.
1119 *
1120 * (self contained on a per cpu basis)
3824f392
MD
1121 */
1122void
f9235b6d 1123lwkt_yield(void)
3824f392 1124{
f9235b6d
MD
1125 globaldata_t gd = mycpu;
1126 thread_t td = gd->gd_curthread;
1127 thread_t xtd;
3824f392 1128
f9235b6d
MD
1129 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1130 splz();
1131 if (td->td_fairq_accum < 0) {
1132 lwkt_schedule_self(curthread);
1133 lwkt_switch();
1134 } else {
1135 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
1136 if (xtd && xtd->td_pri > td->td_pri) {
1137 lwkt_schedule_self(curthread);
1138 lwkt_switch();
1139 }
1140 }
3824f392
MD
1141}
1142
1143/*
f9235b6d
MD
1144 * This yield is designed for kernel threads with a user context.
1145 *
1146 * The kernel acting on behalf of the user is potentially cpu-bound,
1147 * this function will efficiently allow other threads to run and also
1148 * switch to other processes by releasing.
3824f392
MD
1149 *
1150 * The lwkt_user_yield() function is designed to have very low overhead
1151 * if no yield is determined to be needed.
1152 */
1153void
1154lwkt_user_yield(void)
1155{
f9235b6d
MD
1156 globaldata_t gd = mycpu;
1157 thread_t td = gd->gd_curthread;
1158
1159 /*
1160 * Always run any pending interrupts in case we are in a critical
1161 * section.
1162 */
1163 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1164 splz();
3824f392 1165
3824f392 1166 /*
f9235b6d
MD
1167 * Switch (which forces a release) if another kernel thread needs
1168 * the cpu, if userland wants us to resched, or if our kernel
1169 * quantum has run out.
3824f392 1170 */
f9235b6d
MD
1171 if (lwkt_resched_wanted() ||
1172 user_resched_wanted() ||
1173 td->td_fairq_accum < 0)
1174 {
3824f392 1175 lwkt_switch();
3824f392
MD
1176 }
1177
f9235b6d 1178#if 0
3824f392 1179 /*
f9235b6d
MD
1180 * Reacquire the current process if we are released.
1181 *
1182 * XXX not implemented atm. The kernel may be holding locks and such,
1183 * so we want the thread to continue to receive cpu.
3824f392 1184 */
f9235b6d
MD
1185 if (td->td_release == NULL && lp) {
1186 lp->lwp_proc->p_usched->acquire_curproc(lp);
1187 td->td_release = lwkt_passive_release;
1188 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1189 }
f9235b6d 1190#endif
b9eb1c19
MD
1191}
1192
1193/*
f1d1c3fa
MD
1194 * Generic schedule. Possibly schedule threads belonging to other cpus and
1195 * deal with threads that might be blocked on a wait queue.
1196 *
0a3f9b47
MD
1197 * We have a little helper inline function which does additional work after
1198 * the thread has been enqueued, including dealing with preemption and
1199 * setting need_lwkt_resched() (which prevents the kernel from returning
1200 * to userland until it has processed higher priority threads).
6330a558
MD
1201 *
1202 * It is possible for this routine to be called after a failed _enqueue
1203 * (due to the target thread migrating, sleeping, or otherwise blocked).
1204 * We have to check that the thread is actually on the run queue!
361d01dd
MD
1205 *
1206 * reschedok is an optimized constant propagated from lwkt_schedule() or
1207 * lwkt_schedule_noresched(). By default it is non-zero, causing a
1208 * reschedule to be requested if the target thread has a higher priority.
1209 * The port messaging code will set MSG_NORESCHED and cause reschedok to
1210 * be 0, prevented undesired reschedules.
8ad65e08 1211 */
0a3f9b47
MD
1212static __inline
1213void
f9235b6d 1214_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount, int reschedok)
0a3f9b47 1215{
b9eb1c19 1216 thread_t otd;
c730be20 1217
6330a558 1218 if (ntd->td_flags & TDF_RUNQ) {
361d01dd 1219 if (ntd->td_preemptable && reschedok) {
f9235b6d 1220 ntd->td_preemptable(ntd, ccount); /* YYY +token */
361d01dd 1221 } else if (reschedok) {
b9eb1c19 1222 otd = curthread;
f9235b6d 1223 if (ntd->td_pri > otd->td_pri)
c730be20 1224 need_lwkt_resched();
6330a558 1225 }
f9235b6d
MD
1226
1227 /*
1228 * Give the thread a little fair share scheduler bump if it
1229 * has been asleep for a while. This is primarily to avoid
1230 * a degenerate case for interrupt threads where accumulator
1231 * crosses into negative territory unnecessarily.
1232 */
1233 if (ntd->td_fairq_lticks != ticks) {
1234 ntd->td_fairq_lticks = ticks;
1235 ntd->td_fairq_accum += gd->gd_fairq_total_pri;
1236 if (ntd->td_fairq_accum > TDFAIRQ_MAX(gd))
1237 ntd->td_fairq_accum = TDFAIRQ_MAX(gd);
1238 }
0a3f9b47
MD
1239 }
1240}
1241
361d01dd 1242static __inline
8ad65e08 1243void
361d01dd 1244_lwkt_schedule(thread_t td, int reschedok)
8ad65e08 1245{
37af14fe
MD
1246 globaldata_t mygd = mycpu;
1247
cf709dd2
MD
1248 KASSERT(td != &td->td_gd->gd_idlethread,
1249 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1250 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1251 crit_enter_gd(mygd);
9388413d 1252 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 1253 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1254 _lwkt_enqueue(td);
1255 } else {
f1d1c3fa 1256 /*
7cd8d145
MD
1257 * If we own the thread, there is no race (since we are in a
1258 * critical section). If we do not own the thread there might
1259 * be a race but the target cpu will deal with it.
f1d1c3fa 1260 */
0f7a3396 1261#ifdef SMP
7cd8d145 1262 if (td->td_gd == mygd) {
9d265729 1263 _lwkt_enqueue(td);
f9235b6d 1264 _lwkt_schedule_post(mygd, td, 1, reschedok);
f1d1c3fa 1265 } else {
e381e77c 1266 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1267 }
0f7a3396 1268#else
7cd8d145 1269 _lwkt_enqueue(td);
f9235b6d 1270 _lwkt_schedule_post(mygd, td, 1, reschedok);
0f7a3396 1271#endif
8ad65e08 1272 }
37af14fe 1273 crit_exit_gd(mygd);
8ad65e08
MD
1274}
1275
361d01dd
MD
1276void
1277lwkt_schedule(thread_t td)
1278{
1279 _lwkt_schedule(td, 1);
1280}
1281
1282void
1283lwkt_schedule_noresched(thread_t td)
1284{
1285 _lwkt_schedule(td, 0);
1286}
1287
88ebb169
SW
1288#ifdef SMP
1289
e381e77c
MD
1290/*
1291 * When scheduled remotely if frame != NULL the IPIQ is being
1292 * run via doreti or an interrupt then preemption can be allowed.
1293 *
1294 * To allow preemption we have to drop the critical section so only
1295 * one is present in _lwkt_schedule_post.
1296 */
1297static void
1298lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1299{
1300 thread_t td = curthread;
1301 thread_t ntd = arg;
1302
1303 if (frame && ntd->td_preemptable) {
1304 crit_exit_noyield(td);
1305 _lwkt_schedule(ntd, 1);
1306 crit_enter_quick(td);
1307 } else {
1308 _lwkt_schedule(ntd, 1);
1309 }
1310}
1311
d9eea1a5 1312/*
52eedfb5
MD
1313 * Thread migration using a 'Pull' method. The thread may or may not be
1314 * the current thread. It MUST be descheduled and in a stable state.
1315 * lwkt_giveaway() must be called on the cpu owning the thread.
1316 *
1317 * At any point after lwkt_giveaway() is called, the target cpu may
1318 * 'pull' the thread by calling lwkt_acquire().
1319 *
ae8e83e6
MD
1320 * We have to make sure the thread is not sitting on a per-cpu tsleep
1321 * queue or it will blow up when it moves to another cpu.
1322 *
52eedfb5 1323 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1324 */
a2a5ad0d 1325void
52eedfb5
MD
1326lwkt_giveaway(thread_t td)
1327{
3b4192fb 1328 globaldata_t gd = mycpu;
52eedfb5 1329
3b4192fb
MD
1330 crit_enter_gd(gd);
1331 if (td->td_flags & TDF_TSLEEPQ)
1332 tsleep_remove(td);
1333 KKASSERT(td->td_gd == gd);
1334 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1335 td->td_flags |= TDF_MIGRATING;
1336 crit_exit_gd(gd);
52eedfb5
MD
1337}
1338
1339void
a2a5ad0d
MD
1340lwkt_acquire(thread_t td)
1341{
37af14fe
MD
1342 globaldata_t gd;
1343 globaldata_t mygd;
a2a5ad0d 1344
52eedfb5 1345 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1346 gd = td->td_gd;
37af14fe 1347 mygd = mycpu;
52eedfb5 1348 if (gd != mycpu) {
35238fa5 1349 cpu_lfence();
52eedfb5 1350 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1351 crit_enter_gd(mygd);
cfaeae2a 1352 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23
MD
1353 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1354#ifdef SMP
1355 lwkt_process_ipiq();
1356#endif
52eedfb5 1357 cpu_lfence();
df910c23 1358 }
cfaeae2a 1359 DEBUG_POP_INFO();
562273ea 1360 cpu_mfence();
37af14fe 1361 td->td_gd = mygd;
52eedfb5
MD
1362 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1363 td->td_flags &= ~TDF_MIGRATING;
1364 crit_exit_gd(mygd);
1365 } else {
1366 crit_enter_gd(mygd);
1367 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1368 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1369 crit_exit_gd(mygd);
a2a5ad0d
MD
1370 }
1371}
1372
52eedfb5
MD
1373#endif
1374
8ad65e08 1375/*
f1d1c3fa
MD
1376 * Generic deschedule. Descheduling threads other then your own should be
1377 * done only in carefully controlled circumstances. Descheduling is
1378 * asynchronous.
1379 *
1380 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1381 */
1382void
1383lwkt_deschedule(thread_t td)
1384{
f1d1c3fa 1385 crit_enter();
b8a98473 1386#ifdef SMP
f1d1c3fa
MD
1387 if (td == curthread) {
1388 _lwkt_dequeue(td);
1389 } else {
a72187e9 1390 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1391 _lwkt_dequeue(td);
1392 } else {
b8a98473 1393 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1394 }
1395 }
b8a98473
MD
1396#else
1397 _lwkt_dequeue(td);
1398#endif
f1d1c3fa
MD
1399 crit_exit();
1400}
1401
1402/*
4b5f931b
MD
1403 * Set the target thread's priority. This routine does not automatically
1404 * switch to a higher priority thread, LWKT threads are not designed for
1405 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1406 */
1407void
1408lwkt_setpri(thread_t td, int pri)
1409{
a72187e9 1410 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1411 if (td->td_pri != pri) {
1412 KKASSERT(pri >= 0);
1413 crit_enter();
1414 if (td->td_flags & TDF_RUNQ) {
1415 _lwkt_dequeue(td);
1416 td->td_pri = pri;
1417 _lwkt_enqueue(td);
1418 } else {
1419 td->td_pri = pri;
1420 }
1421 crit_exit();
26a0694b 1422 }
26a0694b
MD
1423}
1424
03bd0a5e
MD
1425/*
1426 * Set the initial priority for a thread prior to it being scheduled for
1427 * the first time. The thread MUST NOT be scheduled before or during
1428 * this call. The thread may be assigned to a cpu other then the current
1429 * cpu.
1430 *
1431 * Typically used after a thread has been created with TDF_STOPPREQ,
1432 * and before the thread is initially scheduled.
1433 */
1434void
1435lwkt_setpri_initial(thread_t td, int pri)
1436{
1437 KKASSERT(pri >= 0);
1438 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1439 td->td_pri = pri;
03bd0a5e
MD
1440}
1441
26a0694b
MD
1442void
1443lwkt_setpri_self(int pri)
1444{
1445 thread_t td = curthread;
1446
4b5f931b
MD
1447 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1448 crit_enter();
1449 if (td->td_flags & TDF_RUNQ) {
1450 _lwkt_dequeue(td);
f9235b6d 1451 td->td_pri = pri;
4b5f931b
MD
1452 _lwkt_enqueue(td);
1453 } else {
f9235b6d 1454 td->td_pri = pri;
4b5f931b
MD
1455 }
1456 crit_exit();
1457}
1458
5d21b981 1459/*
f9235b6d
MD
1460 * 1/hz tick (typically 10ms) x TDFAIRQ_SCALE (typ 8) = 80ms full cycle.
1461 *
1462 * Example: two competing threads, same priority N. decrement by (2*N)
1463 * increment by N*8, each thread will get 4 ticks.
1464 */
1465void
1466lwkt_fairq_schedulerclock(thread_t td)
1467{
2a418930
MD
1468 globaldata_t gd;
1469
f9235b6d
MD
1470 if (fairq_enable) {
1471 while (td) {
2a418930
MD
1472 gd = td->td_gd;
1473 if (td != &gd->gd_idlethread) {
1474 td->td_fairq_accum -= gd->gd_fairq_total_pri;
1475 if (td->td_fairq_accum < -TDFAIRQ_MAX(gd))
1476 td->td_fairq_accum = -TDFAIRQ_MAX(gd);
f9235b6d
MD
1477 if (td->td_fairq_accum < 0)
1478 need_lwkt_resched();
1479 td->td_fairq_lticks = ticks;
1480 }
1481 td = td->td_preempted;
1482 }
1483 }
1484}
1485
1486static void
1487lwkt_fairq_accumulate(globaldata_t gd, thread_t td)
1488{
1489 td->td_fairq_accum += td->td_pri * TDFAIRQ_SCALE;
1490 if (td->td_fairq_accum > TDFAIRQ_MAX(td->td_gd))
1491 td->td_fairq_accum = TDFAIRQ_MAX(td->td_gd);
1492}
1493
1494/*
52eedfb5
MD
1495 * Migrate the current thread to the specified cpu.
1496 *
1497 * This is accomplished by descheduling ourselves from the current cpu,
1498 * moving our thread to the tdallq of the target cpu, IPI messaging the
1499 * target cpu, and switching out. TDF_MIGRATING prevents scheduling
1500 * races while the thread is being migrated.
ae8e83e6
MD
1501 *
1502 * We must be sure to remove ourselves from the current cpu's tsleepq
1503 * before potentially moving to another queue. The thread can be on
1504 * a tsleepq due to a left-over tsleep_interlock().
95858b91
MD
1505 *
1506 * We also have to make sure that the switch code doesn't allow an IPI
1507 * processing operation to leak in between our send and our switch, or
1508 * any other potential livelock such that might occur when we release the
1509 * current process designation, so do that first.
5d21b981 1510 */
3d28ff59 1511#ifdef SMP
5d21b981 1512static void lwkt_setcpu_remote(void *arg);
3d28ff59 1513#endif
5d21b981
MD
1514
1515void
1516lwkt_setcpu_self(globaldata_t rgd)
1517{
1518#ifdef SMP
1519 thread_t td = curthread;
1520
1521 if (td->td_gd != rgd) {
1522 crit_enter_quick(td);
95858b91
MD
1523 if (td->td_release)
1524 td->td_release(td);
ae8e83e6 1525 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1526 tsleep_remove(td);
5d21b981
MD
1527 td->td_flags |= TDF_MIGRATING;
1528 lwkt_deschedule_self(td);
52eedfb5 1529 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
b8a98473 1530 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td);
5d21b981
MD
1531 lwkt_switch();
1532 /* we are now on the target cpu */
52eedfb5 1533 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1534 crit_exit_quick(td);
1535 }
1536#endif
1537}
1538
ecdefdda
MD
1539void
1540lwkt_migratecpu(int cpuid)
1541{
1542#ifdef SMP
1543 globaldata_t rgd;
1544
1545 rgd = globaldata_find(cpuid);
1546 lwkt_setcpu_self(rgd);
1547#endif
1548}
1549
5d21b981
MD
1550/*
1551 * Remote IPI for cpu migration (called while in a critical section so we
1552 * do not have to enter another one). The thread has already been moved to
1553 * our cpu's allq, but we must wait for the thread to be completely switched
1554 * out on the originating cpu before we schedule it on ours or the stack
1555 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD
1556 * change to main memory.
1557 *
1558 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races
1559 * against wakeups. It is best if this interface is used only when there
1560 * are no pending events that might try to schedule the thread.
1561 */
3d28ff59 1562#ifdef SMP
5d21b981
MD
1563static void
1564lwkt_setcpu_remote(void *arg)
1565{
1566 thread_t td = arg;
1567 globaldata_t gd = mycpu;
cfaeae2a 1568 int retry = 10000000;
5d21b981 1569
cfaeae2a 1570 DEBUG_PUSH_INFO("lwkt_setcpu_remote");
df910c23
MD
1571 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1572#ifdef SMP
1573 lwkt_process_ipiq();
1574#endif
35238fa5 1575 cpu_lfence();
562273ea 1576 cpu_pause();
cfaeae2a
MD
1577 if (--retry == 0) {
1578 kprintf("lwkt_setcpu_remote: td->td_flags %08x\n",
1579 td->td_flags);
1580 retry = 10000000;
1581 }
df910c23 1582 }
cfaeae2a 1583 DEBUG_POP_INFO();
5d21b981 1584 td->td_gd = gd;
562273ea 1585 cpu_mfence();
5d21b981 1586 td->td_flags &= ~TDF_MIGRATING;
9388413d 1587 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
5d21b981
MD
1588 _lwkt_enqueue(td);
1589}
3d28ff59 1590#endif
5d21b981 1591
553ea3c8 1592struct lwp *
4b5f931b
MD
1593lwkt_preempted_proc(void)
1594{
73e4f7b9 1595 thread_t td = curthread;
4b5f931b
MD
1596 while (td->td_preempted)
1597 td = td->td_preempted;
553ea3c8 1598 return(td->td_lwp);
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1599}
1600
4b5f931b 1601/*
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1602 * Create a kernel process/thread/whatever. It shares it's address space
1603 * with proc0 - ie: kernel only.
1604 *
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1605 * NOTE! By default new threads are created with the MP lock held. A
1606 * thread which does not require the MP lock should release it by calling
1607 * rel_mplock() at the start of the new thread.
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1608 */
1609int
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1610lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1611 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1612{
73e4f7b9 1613 thread_t td;
e2565a42 1614 __va_list ap;
99df837e 1615
d3d32139 1616 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1617 tdflags);
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1618 if (tdp)
1619 *tdp = td;
709799ea 1620 cpu_set_thread_handler(td, lwkt_exit, func, arg);
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1621
1622 /*
1623 * Set up arg0 for 'ps' etc
1624 */
e2565a42 1625 __va_start(ap, fmt);
379210cb 1626 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1627 __va_end(ap);
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1628
1629 /*
1630 * Schedule the thread to run
1631 */
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1632 if ((td->td_flags & TDF_STOPREQ) == 0)
1633 lwkt_schedule(td);
1634 else
1635 td->td_flags &= ~TDF_STOPREQ;
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1636 return 0;
1637}
1638
1639/*
1640 * Destroy an LWKT thread. Warning! This function is not called when
1641 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1642 * uses a different reaping mechanism.
1643 */
1644void
1645lwkt_exit(void)
1646{
1647 thread_t td = curthread;
c070746a 1648 thread_t std;
8826f33a 1649 globaldata_t gd;
99df837e 1650
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1651 /*
1652 * Do any cleanup that might block here
1653 */
99df837e 1654 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1655 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1656 caps_exit(td);
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1657 biosched_done(td);
1658 dsched_exit_thread(td);
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1659
1660 /*
1661 * Get us into a critical section to interlock gd_freetd and loop
1662 * until we can get it freed.
1663 *
1664 * We have to cache the current td in gd_freetd because objcache_put()ing
1665 * it would rip it out from under us while our thread is still active.
1666 */
1667 gd = mycpu;
37af14fe 1668 crit_enter_quick(td);
c070746a 1669 while ((std = gd->gd_freetd) != NULL) {
cf709dd2 1670 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
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1671 gd->gd_freetd = NULL;
1672 objcache_put(thread_cache, std);
1673 }
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1674
1675 /*
1676 * Remove thread resources from kernel lists and deschedule us for
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1677 * the last time. We cannot block after this point or we may end
1678 * up with a stale td on the tsleepq.
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1679 */
1680 if (td->td_flags & TDF_TSLEEPQ)
1681 tsleep_remove(td);
37af14fe 1682 lwkt_deschedule_self(td);
e56e4dea 1683 lwkt_remove_tdallq(td);
74c9628e 1684 KKASSERT(td->td_refs == 0);
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1685
1686 /*
1687 * Final cleanup
1688 */
1689 KKASSERT(gd->gd_freetd == NULL);
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1690 if (td->td_flags & TDF_ALLOCATED_THREAD)
1691 gd->gd_freetd = td;
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1692 cpu_thread_exit();
1693}
1694
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1695void
1696lwkt_remove_tdallq(thread_t td)
1697{
1698 KKASSERT(td->td_gd == mycpu);
1699 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1700}
1701
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1702/*
1703 * Code reduction and branch prediction improvements. Call/return
1704 * overhead on modern cpus often degenerates into 0 cycles due to
1705 * the cpu's branch prediction hardware and return pc cache. We
1706 * can take advantage of this by not inlining medium-complexity
1707 * functions and we can also reduce the branch prediction impact
1708 * by collapsing perfectly predictable branches into a single
1709 * procedure instead of duplicating it.
1710 *
1711 * Is any of this noticeable? Probably not, so I'll take the
1712 * smaller code size.
1713 */
1714void
b6468f56 1715crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1716{
b6468f56 1717 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
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1718}
1719
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1720void
1721crit_panic(void)
1722{
1723 thread_t td = curthread;
850634cc 1724 int lcrit = td->td_critcount;
2d93b37a 1725
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1726 td->td_critcount = 0;
1727 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1728 /* NOT REACHED */
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1729}
1730
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1731#ifdef SMP
1732
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1733/*
1734 * Called from debugger/panic on cpus which have been stopped. We must still
1735 * process the IPIQ while stopped, even if we were stopped while in a critical
1736 * section (XXX).
1737 *
1738 * If we are dumping also try to process any pending interrupts. This may
1739 * or may not work depending on the state of the cpu at the point it was
1740 * stopped.
1741 */
1742void
1743lwkt_smp_stopped(void)
1744{
1745 globaldata_t gd = mycpu;
1746
1747 crit_enter_gd(gd);
1748 if (dumping) {
1749 lwkt_process_ipiq();
1750 splz();
1751 } else {
1752 lwkt_process_ipiq();
1753 }
1754 crit_exit_gd(gd);
1755}
1756
d165e668 1757#endif