vkernel: Remove unused variable.
[dragonfly.git] / sys / kern / lwkt_thread.c
CommitLineData
8ad65e08 1/*
b12defdc 2 * Copyright (c) 2003-2011 The DragonFly Project. All rights reserved.
60f60350 3 *
8c10bfcf
MD
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
60f60350 6 *
8ad65e08
MD
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 *
8ad65e08
MD
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
8c10bfcf
MD
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 *
8c10bfcf
MD
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.
75cdbe6c
MD
33 */
34
35/*
36 * Each cpu in a system has its own self-contained light weight kernel
37 * thread scheduler, which means that generally speaking we only need
38 * to use a critical section to avoid problems. Foreign thread
39 * scheduling is queued via (async) IPIs.
8ad65e08
MD
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>
9d265729
MD
56
57#include <sys/thread2.h>
58#include <sys/spinlock2.h>
684a93c4 59#include <sys/mplock2.h>
f1d1c3fa 60
8c72e3d5
AH
61#include <sys/dsched.h>
62
7d0bac62
MD
63#include <vm/vm.h>
64#include <vm/vm_param.h>
65#include <vm/vm_kern.h>
66#include <vm/vm_object.h>
67#include <vm/vm_page.h>
68#include <vm/vm_map.h>
69#include <vm/vm_pager.h>
70#include <vm/vm_extern.h>
7d0bac62 71
99df837e 72#include <machine/stdarg.h>
96728c05 73#include <machine/smp.h>
99df837e 74
d850923c
AE
75#if !defined(KTR_CTXSW)
76#define KTR_CTXSW KTR_ALL
77#endif
78KTR_INFO_MASTER(ctxsw);
a1f0fb66
AE
79KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p",
80 sizeof(int) + sizeof(struct thread *));
81KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p",
82 sizeof(int) + sizeof(struct thread *));
83KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s",
84 sizeof (struct thread *) + sizeof(char *));
85KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", sizeof (struct thread *));
1541028a 86
40aaf5fc
NT
87static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
88
0f7a3396
MD
89#ifdef INVARIANTS
90static int panic_on_cscount = 0;
91#endif
05220613
MD
92static __int64_t switch_count = 0;
93static __int64_t preempt_hit = 0;
94static __int64_t preempt_miss = 0;
95static __int64_t preempt_weird = 0;
85946b6c 96static __int64_t token_contention_count[TDPRI_MAX+1] __debugvar;
fb0f29c4 97static int lwkt_use_spin_port;
40aaf5fc 98static struct objcache *thread_cache;
05220613 99
88ebb169 100#ifdef SMP
e381e77c 101static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
cc9b6223 102static void lwkt_setcpu_remote(void *arg);
88ebb169 103#endif
e381e77c 104
0855a2af
JG
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
fb0f29c4
MD
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
0c52fa62
SG
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
0c52fa62
SG
120SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
121 "Number of switched threads");
9733f757 122SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
0c52fa62 123 "Successful preemption events");
9733f757 124SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
0c52fa62
SG
125 "Failed preemption events");
126SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
127 "Number of preempted threads.");
38717797 128#ifdef INVARIANTS
85946b6c
MD
129SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_00, CTLFLAG_RW,
130 &token_contention_count[0], 0, "spinning due to token contention");
131SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_01, CTLFLAG_RW,
132 &token_contention_count[1], 0, "spinning due to token contention");
133SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_02, CTLFLAG_RW,
134 &token_contention_count[2], 0, "spinning due to token contention");
135SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_03, CTLFLAG_RW,
136 &token_contention_count[3], 0, "spinning due to token contention");
137SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_04, CTLFLAG_RW,
138 &token_contention_count[4], 0, "spinning due to token contention");
139SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_05, CTLFLAG_RW,
140 &token_contention_count[5], 0, "spinning due to token contention");
141SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_06, CTLFLAG_RW,
142 &token_contention_count[6], 0, "spinning due to token contention");
143SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_07, CTLFLAG_RW,
144 &token_contention_count[7], 0, "spinning due to token contention");
145SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_08, CTLFLAG_RW,
146 &token_contention_count[8], 0, "spinning due to token contention");
147SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_09, CTLFLAG_RW,
148 &token_contention_count[9], 0, "spinning due to token contention");
149SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_10, CTLFLAG_RW,
150 &token_contention_count[10], 0, "spinning due to token contention");
151SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_11, CTLFLAG_RW,
152 &token_contention_count[11], 0, "spinning due to token contention");
153SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_12, CTLFLAG_RW,
154 &token_contention_count[12], 0, "spinning due to token contention");
155SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_13, CTLFLAG_RW,
156 &token_contention_count[13], 0, "spinning due to token contention");
157SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_14, CTLFLAG_RW,
158 &token_contention_count[14], 0, "spinning due to token contention");
159SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_15, CTLFLAG_RW,
160 &token_contention_count[15], 0, "spinning due to token contention");
161SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_16, CTLFLAG_RW,
162 &token_contention_count[16], 0, "spinning due to token contention");
163SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_17, CTLFLAG_RW,
164 &token_contention_count[17], 0, "spinning due to token contention");
165SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_18, CTLFLAG_RW,
166 &token_contention_count[18], 0, "spinning due to token contention");
167SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_19, CTLFLAG_RW,
168 &token_contention_count[19], 0, "spinning due to token contention");
169SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_20, CTLFLAG_RW,
170 &token_contention_count[20], 0, "spinning due to token contention");
171SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_21, CTLFLAG_RW,
172 &token_contention_count[21], 0, "spinning due to token contention");
173SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_22, CTLFLAG_RW,
174 &token_contention_count[22], 0, "spinning due to token contention");
175SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_23, CTLFLAG_RW,
176 &token_contention_count[23], 0, "spinning due to token contention");
177SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_24, CTLFLAG_RW,
178 &token_contention_count[24], 0, "spinning due to token contention");
179SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_25, CTLFLAG_RW,
180 &token_contention_count[25], 0, "spinning due to token contention");
181SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_26, CTLFLAG_RW,
182 &token_contention_count[26], 0, "spinning due to token contention");
183SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_27, CTLFLAG_RW,
184 &token_contention_count[27], 0, "spinning due to token contention");
185SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_28, CTLFLAG_RW,
186 &token_contention_count[28], 0, "spinning due to token contention");
187SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_29, CTLFLAG_RW,
188 &token_contention_count[29], 0, "spinning due to token contention");
189SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_30, CTLFLAG_RW,
190 &token_contention_count[30], 0, "spinning due to token contention");
191SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count_31, CTLFLAG_RW,
192 &token_contention_count[31], 0, "spinning due to token contention");
38717797 193#endif
b12defdc 194static int fairq_enable = 0;
2a418930
MD
195SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
196 &fairq_enable, 0, "Turn on fairq priority accumulators");
85946b6c 197static int fairq_bypass = -1;
b12defdc
MD
198SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
199 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
200extern int lwkt_sched_debug;
201int lwkt_sched_debug = 0;
202SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
203 &lwkt_sched_debug, 0, "Scheduler debug");
2a418930
MD
204static int lwkt_spin_loops = 10;
205SYSCTL_INT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
b12defdc
MD
206 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
207static int lwkt_spin_reseq = 0;
208SYSCTL_INT(_lwkt, OID_AUTO, spin_reseq, CTLFLAG_RW,
209 &lwkt_spin_reseq, 0, "Scheduler resequencer enable");
210static int lwkt_spin_monitor = 0;
211SYSCTL_INT(_lwkt, OID_AUTO, spin_monitor, CTLFLAG_RW,
212 &lwkt_spin_monitor, 0, "Scheduler uses monitor/mwait");
d5b2d319
MD
213static int lwkt_spin_fatal = 0; /* disabled */
214SYSCTL_INT(_lwkt, OID_AUTO, spin_fatal, CTLFLAG_RW,
215 &lwkt_spin_fatal, 0, "LWKT scheduler spin loops till fatal panic");
fbc024e4 216static int preempt_enable = 1;
2a418930
MD
217SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
218 &preempt_enable, 0, "Enable preemption");
765b1ae0
MD
219static int lwkt_cache_threads = 32;
220SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
221 &lwkt_cache_threads, 0, "thread+kstack cache");
fbc024e4 222
2a418930
MD
223static __cachealign int lwkt_cseq_rindex;
224static __cachealign int lwkt_cseq_windex;
05220613 225
4b5f931b
MD
226/*
227 * These helper procedures handle the runq, they can only be called from
228 * within a critical section.
75cdbe6c
MD
229 *
230 * WARNING! Prior to SMP being brought up it is possible to enqueue and
231 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
232 * instead of 'mycpu' when referencing the globaldata structure. Once
233 * SMP live enqueuing and dequeueing only occurs on the current cpu.
4b5f931b 234 */
f1d1c3fa
MD
235static __inline
236void
237_lwkt_dequeue(thread_t td)
238{
239 if (td->td_flags & TDF_RUNQ) {
75cdbe6c 240 struct globaldata *gd = td->td_gd;
4b5f931b 241
f1d1c3fa 242 td->td_flags &= ~TDF_RUNQ;
f9235b6d 243 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 244 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
2a418930 245 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
f1d1c3fa
MD
246 }
247}
248
f9235b6d
MD
249/*
250 * Priority enqueue.
251 *
252 * NOTE: There are a limited number of lwkt threads runnable since user
253 * processes only schedule one at a time per cpu.
254 */
f1d1c3fa
MD
255static __inline
256void
257_lwkt_enqueue(thread_t td)
258{
f9235b6d
MD
259 thread_t xtd;
260
7f5d7ed7 261 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
75cdbe6c 262 struct globaldata *gd = td->td_gd;
4b5f931b 263
f1d1c3fa 264 td->td_flags |= TDF_RUNQ;
f9235b6d
MD
265 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
266 if (xtd == NULL) {
85946b6c
MD
267 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
268 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
f9235b6d 269 } else {
85946b6c
MD
270 while (xtd && xtd->td_pri >= td->td_pri)
271 xtd = TAILQ_NEXT(xtd, td_threadq);
272 if (xtd)
273 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
274 else
275 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
f9235b6d 276 }
b12defdc
MD
277
278 /*
85946b6c 279 * Request a LWKT reschedule if we are now at the head of the queue.
b12defdc 280 */
85946b6c
MD
281 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
282 need_lwkt_resched();
f1d1c3fa
MD
283 }
284}
8ad65e08 285
40aaf5fc
NT
286static __boolean_t
287_lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
288{
289 struct thread *td = (struct thread *)obj;
290
291 td->td_kstack = NULL;
292 td->td_kstack_size = 0;
293 td->td_flags = TDF_ALLOCATED_THREAD;
294 return (1);
295}
296
297static void
298_lwkt_thread_dtor(void *obj, void *privdata)
299{
300 struct thread *td = (struct thread *)obj;
301
302 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
303 ("_lwkt_thread_dtor: not allocated from objcache"));
304 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
305 td->td_kstack_size > 0,
306 ("_lwkt_thread_dtor: corrupted stack"));
307 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
308}
309
310/*
311 * Initialize the lwkt s/system.
765b1ae0
MD
312 *
313 * Nominally cache up to 32 thread + kstack structures.
40aaf5fc
NT
314 */
315void
316lwkt_init(void)
317{
765b1ae0
MD
318 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
319 thread_cache = objcache_create_mbacked(
320 M_THREAD, sizeof(struct thread),
321 NULL, lwkt_cache_threads,
322 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
40aaf5fc
NT
323}
324
37af14fe
MD
325/*
326 * Schedule a thread to run. As the current thread we can always safely
327 * schedule ourselves, and a shortcut procedure is provided for that
328 * function.
329 *
330 * (non-blocking, self contained on a per cpu basis)
331 */
332void
333lwkt_schedule_self(thread_t td)
334{
cfaeae2a 335 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 336 crit_enter_quick(td);
f9235b6d
MD
337 KASSERT(td != &td->td_gd->gd_idlethread,
338 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
9388413d 339 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 340 _lwkt_enqueue(td);
37af14fe
MD
341 crit_exit_quick(td);
342}
343
344/*
345 * Deschedule a thread.
346 *
347 * (non-blocking, self contained on a per cpu basis)
348 */
349void
350lwkt_deschedule_self(thread_t td)
351{
352 crit_enter_quick(td);
37af14fe
MD
353 _lwkt_dequeue(td);
354 crit_exit_quick(td);
355}
356
8ad65e08
MD
357/*
358 * LWKTs operate on a per-cpu basis
359 *
73e4f7b9 360 * WARNING! Called from early boot, 'mycpu' may not work yet.
8ad65e08
MD
361 */
362void
363lwkt_gdinit(struct globaldata *gd)
364{
f9235b6d 365 TAILQ_INIT(&gd->gd_tdrunq);
73e4f7b9 366 TAILQ_INIT(&gd->gd_tdallq);
8ad65e08
MD
367}
368
7d0bac62
MD
369/*
370 * Create a new thread. The thread must be associated with a process context
75cdbe6c
MD
371 * or LWKT start address before it can be scheduled. If the target cpu is
372 * -1 the thread will be created on the current cpu.
0cfcada1
MD
373 *
374 * If you intend to create a thread without a process context this function
375 * does everything except load the startup and switcher function.
7d0bac62
MD
376 */
377thread_t
d3d32139 378lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
7d0bac62 379{
d2d8515b 380 static int cpu_rotator;
c070746a 381 globaldata_t gd = mycpu;
99df837e 382 void *stack;
7d0bac62 383
c070746a
MD
384 /*
385 * If static thread storage is not supplied allocate a thread. Reuse
386 * a cached free thread if possible. gd_freetd is used to keep an exiting
387 * thread intact through the exit.
388 */
ef0fdad1 389 if (td == NULL) {
cf709dd2
MD
390 crit_enter_gd(gd);
391 if ((td = gd->gd_freetd) != NULL) {
392 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
393 TDF_RUNQ)) == 0);
c070746a 394 gd->gd_freetd = NULL;
cf709dd2 395 } else {
c070746a 396 td = objcache_get(thread_cache, M_WAITOK);
cf709dd2
MD
397 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
398 TDF_RUNQ)) == 0);
399 }
400 crit_exit_gd(gd);
40aaf5fc
NT
401 KASSERT((td->td_flags &
402 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD,
403 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
404 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
ef0fdad1 405 }
c070746a
MD
406
407 /*
408 * Try to reuse cached stack.
409 */
f470d0c8
MD
410 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
411 if (flags & TDF_ALLOCATED_STACK) {
e4846942 412 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
f470d0c8
MD
413 stack = NULL;
414 }
415 }
416 if (stack == NULL) {
e40cfbd7 417 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
ef0fdad1 418 flags |= TDF_ALLOCATED_STACK;
99df837e 419 }
d2d8515b
MD
420 if (cpu < 0) {
421 cpu = ++cpu_rotator;
422 cpu_ccfence();
423 cpu %= ncpus;
424 }
425 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
99df837e 426 return(td);
7d0bac62
MD
427}
428
429/*
430 * Initialize a preexisting thread structure. This function is used by
431 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
432 *
f8c3996b
MD
433 * All threads start out in a critical section at a priority of
434 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
75cdbe6c
MD
435 * appropriate. This function may send an IPI message when the
436 * requested cpu is not the current cpu and consequently gd_tdallq may
437 * not be initialized synchronously from the point of view of the originating
438 * cpu.
439 *
440 * NOTE! we have to be careful in regards to creating threads for other cpus
441 * if SMP has not yet been activated.
7d0bac62 442 */
41a01a4d
MD
443#ifdef SMP
444
75cdbe6c
MD
445static void
446lwkt_init_thread_remote(void *arg)
447{
448 thread_t td = arg;
449
52eedfb5
MD
450 /*
451 * Protected by critical section held by IPI dispatch
452 */
75cdbe6c
MD
453 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
454}
455
41a01a4d
MD
456#endif
457
fdce8919
MD
458/*
459 * lwkt core thread structural initialization.
460 *
461 * NOTE: All threads are initialized as mpsafe threads.
462 */
7d0bac62 463void
f470d0c8
MD
464lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
465 struct globaldata *gd)
7d0bac62 466{
37af14fe
MD
467 globaldata_t mygd = mycpu;
468
99df837e
MD
469 bzero(td, sizeof(struct thread));
470 td->td_kstack = stack;
f470d0c8 471 td->td_kstack_size = stksize;
d3d32139 472 td->td_flags = flags;
26a0694b 473 td->td_gd = gd;
f9235b6d
MD
474 td->td_pri = TDPRI_KERN_DAEMON;
475 td->td_critcount = 1;
3b998fa9 476 td->td_toks_stop = &td->td_toks_base;
392cd266 477 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT))
fb0f29c4
MD
478 lwkt_initport_spin(&td->td_msgport);
479 else
480 lwkt_initport_thread(&td->td_msgport, td);
99df837e 481 pmap_init_thread(td);
0f7a3396 482#ifdef SMP
5d21b981
MD
483 /*
484 * Normally initializing a thread for a remote cpu requires sending an
485 * IPI. However, the idlethread is setup before the other cpus are
486 * activated so we have to treat it as a special case. XXX manipulation
487 * of gd_tdallq requires the BGL.
488 */
489 if (gd == mygd || td == &gd->gd_idlethread) {
37af14fe 490 crit_enter_gd(mygd);
75cdbe6c 491 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 492 crit_exit_gd(mygd);
75cdbe6c 493 } else {
2db3b277 494 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
75cdbe6c 495 }
0f7a3396 496#else
37af14fe 497 crit_enter_gd(mygd);
0f7a3396 498 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
37af14fe 499 crit_exit_gd(mygd);
0f7a3396 500#endif
8c72e3d5
AH
501
502 dsched_new_thread(td);
73e4f7b9
MD
503}
504
505void
506lwkt_set_comm(thread_t td, const char *ctl, ...)
507{
e2565a42 508 __va_list va;
73e4f7b9 509
e2565a42 510 __va_start(va, ctl);
379210cb 511 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
e2565a42 512 __va_end(va);
e7c0dbba 513 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]);
7d0bac62
MD
514}
515
99df837e 516void
73e4f7b9 517lwkt_hold(thread_t td)
99df837e 518{
74c9628e 519 atomic_add_int(&td->td_refs, 1);
73e4f7b9
MD
520}
521
522void
523lwkt_rele(thread_t td)
524{
525 KKASSERT(td->td_refs > 0);
74c9628e 526 atomic_add_int(&td->td_refs, -1);
73e4f7b9
MD
527}
528
529void
530lwkt_wait_free(thread_t td)
531{
532 while (td->td_refs)
377d4740 533 tsleep(td, 0, "tdreap", hz);
73e4f7b9
MD
534}
535
536void
537lwkt_free_thread(thread_t td)
538{
74c9628e 539 KKASSERT(td->td_refs == 0);
c17a6852
MD
540 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
541 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
40aaf5fc
NT
542 if (td->td_flags & TDF_ALLOCATED_THREAD) {
543 objcache_put(thread_cache, td);
544 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
545 /* client-allocated struct with internally allocated stack */
546 KASSERT(td->td_kstack && td->td_kstack_size > 0,
547 ("lwkt_free_thread: corrupted stack"));
548 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
549 td->td_kstack = NULL;
550 td->td_kstack_size = 0;
99df837e 551 }
e7c0dbba 552 KTR_LOG(ctxsw_deadtd, td);
99df837e
MD
553}
554
555
8ad65e08
MD
556/*
557 * Switch to the next runnable lwkt. If no LWKTs are runnable then
f1d1c3fa
MD
558 * switch to the idlethread. Switching must occur within a critical
559 * section to avoid races with the scheduling queue.
560 *
561 * We always have full control over our cpu's run queue. Other cpus
562 * that wish to manipulate our queue must use the cpu_*msg() calls to
563 * talk to our cpu, so a critical section is all that is needed and
564 * the result is very, very fast thread switching.
565 *
96728c05
MD
566 * The LWKT scheduler uses a fixed priority model and round-robins at
567 * each priority level. User process scheduling is a totally
568 * different beast and LWKT priorities should not be confused with
569 * user process priorities.
f1d1c3fa 570 *
69d78e99
MD
571 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
572 * is not called by the current thread in the preemption case, only when
573 * the preempting thread blocks (in order to return to the original thread).
cfaeae2a
MD
574 *
575 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
576 * migration and tsleep deschedule the current lwkt thread and call
577 * lwkt_switch(). In particular, the target cpu of the migration fully
578 * expects the thread to become non-runnable and can deadlock against
579 * cpusync operations if we run any IPIs prior to switching the thread out.
580 *
581 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
95858b91 582 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
8ad65e08
MD
583 */
584void
585lwkt_switch(void)
586{
37af14fe
MD
587 globaldata_t gd = mycpu;
588 thread_t td = gd->gd_curthread;
8ad65e08 589 thread_t ntd;
f9235b6d 590 thread_t xtd;
b12defdc 591 int spinning = 0;
8ad65e08 592
da0b0e8b
MD
593 KKASSERT(gd->gd_processing_ipiq == 0);
594
46a3f46d 595 /*
27e88a6e
MD
596 * Switching from within a 'fast' (non thread switched) interrupt or IPI
597 * is illegal. However, we may have to do it anyway if we hit a fatal
598 * kernel trap or we have paniced.
599 *
600 * If this case occurs save and restore the interrupt nesting level.
46a3f46d 601 */
27e88a6e
MD
602 if (gd->gd_intr_nesting_level) {
603 int savegdnest;
604 int savegdtrap;
605
5fddbda2 606 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
4a28fe22
MD
607 panic("lwkt_switch: Attempt to switch from a "
608 "a fast interrupt, ipi, or hard code section, "
609 "td %p\n",
610 td);
27e88a6e
MD
611 } else {
612 savegdnest = gd->gd_intr_nesting_level;
613 savegdtrap = gd->gd_trap_nesting_level;
614 gd->gd_intr_nesting_level = 0;
615 gd->gd_trap_nesting_level = 0;
a7422615
MD
616 if ((td->td_flags & TDF_PANICWARN) == 0) {
617 td->td_flags |= TDF_PANICWARN;
4a28fe22
MD
618 kprintf("Warning: thread switch from interrupt, IPI, "
619 "or hard code section.\n"
a7422615 620 "thread %p (%s)\n", td, td->td_comm);
7ce2998e 621 print_backtrace(-1);
a7422615 622 }
27e88a6e
MD
623 lwkt_switch();
624 gd->gd_intr_nesting_level = savegdnest;
625 gd->gd_trap_nesting_level = savegdtrap;
626 return;
627 }
96728c05 628 }
ef0fdad1 629
cb973d15 630 /*
85946b6c
MD
631 * Release our current user process designation if we are blocking
632 * or if a user reschedule was requested.
633 *
634 * NOTE: This function is NOT called if we are switching into or
635 * returning from a preemption.
636 *
637 * NOTE: Releasing our current user process designation may cause
638 * it to be assigned to another thread, which in turn will
639 * cause us to block in the usched acquire code when we attempt
640 * to return to userland.
641 *
642 * NOTE: On SMP systems this can be very nasty when heavy token
643 * contention is present so we want to be careful not to
644 * release the designation gratuitously.
cb973d15 645 */
85946b6c
MD
646 if (td->td_release &&
647 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
cb973d15 648 td->td_release(td);
85946b6c 649 }
cb973d15 650
85946b6c
MD
651 /*
652 * Release all tokens
653 */
37af14fe 654 crit_enter_gd(gd);
3b998fa9 655 if (TD_TOKS_HELD(td))
9d265729
MD
656 lwkt_relalltokens(td);
657
658 /*
b02926de
MD
659 * We had better not be holding any spin locks, but don't get into an
660 * endless panic loop.
9d265729 661 */
d666840a
MD
662 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
663 ("lwkt_switch: still holding %d exclusive spinlocks!",
664 gd->gd_spinlocks_wr));
9d265729 665
8a8d5d85
MD
666
667#ifdef SMP
0f7a3396
MD
668#ifdef INVARIANTS
669 if (td->td_cscount) {
6ea70f76 670 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
0f7a3396
MD
671 td);
672 if (panic_on_cscount)
673 panic("switching while mastering cpusync");
674 }
675#endif
8a8d5d85 676#endif
f9235b6d
MD
677
678 /*
679 * If we had preempted another thread on this cpu, resume the preempted
680 * thread. This occurs transparently, whether the preempted thread
681 * was scheduled or not (it may have been preempted after descheduling
682 * itself).
683 *
684 * We have to setup the MP lock for the original thread after backing
685 * out the adjustment that was made to curthread when the original
686 * was preempted.
687 */
99df837e 688 if ((ntd = td->td_preempted) != NULL) {
26a0694b
MD
689 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
690 ntd->td_flags |= TDF_PREEMPT_DONE;
8ec60c3f
MD
691
692 /*
b9eb1c19
MD
693 * The interrupt may have woken a thread up, we need to properly
694 * set the reschedule flag if the originally interrupted thread is
695 * at a lower priority.
85946b6c
MD
696 *
697 * The interrupt may not have descheduled.
8ec60c3f 698 */
85946b6c 699 if (TAILQ_FIRST(&gd->gd_tdrunq) != ntd)
8ec60c3f 700 need_lwkt_resched();
f9235b6d
MD
701 goto havethread_preempted;
702 }
703
b12defdc 704 /*
f9235b6d 705 * If we cannot obtain ownership of the tokens we cannot immediately
cfaeae2a
MD
706 * schedule the target thread.
707 *
708 * Reminder: Again, we cannot afford to run any IPIs in this path if
709 * the current thread has been descheduled.
f9235b6d
MD
710 */
711 for (;;) {
b12defdc 712 clear_lwkt_resched();
f9235b6d 713
4b5f931b 714 /*
2a418930 715 * Hotpath - pull the head of the run queue and attempt to schedule
85946b6c 716 * it.
41a01a4d 717 */
2a418930
MD
718 for (;;) {
719 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
720
721 if (ntd == NULL) {
722 /*
b12defdc 723 * Runq is empty, switch to idle to allow it to halt.
2a418930
MD
724 */
725 ntd = &gd->gd_idlethread;
6f207a2c 726#ifdef SMP
2a418930 727 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
b5d16701 728 ASSERT_NO_TOKENS_HELD(ntd);
6f207a2c 729#endif
2a418930
MD
730 cpu_time.cp_msg[0] = 0;
731 cpu_time.cp_stallpc = 0;
2a418930
MD
732 goto haveidle;
733 }
b12defdc 734 break;
f9235b6d 735 }
41a01a4d 736
8ec60c3f 737 /*
b12defdc 738 * Hotpath - schedule ntd.
6f207a2c
MD
739 *
740 * NOTE: For UP there is no mplock and lwkt_getalltokens()
741 * always succeeds.
8ec60c3f 742 */
b12defdc
MD
743 if (TD_TOKS_NOT_HELD(ntd) ||
744 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops)))
745 {
f9235b6d 746 goto havethread;
b12defdc 747 }
f9235b6d 748
f9235b6d 749 /*
2a418930
MD
750 * Coldpath (SMP only since tokens always succeed on UP)
751 *
752 * We had some contention on the thread we wanted to schedule.
753 * What we do now is try to find a thread that we can schedule
b12defdc 754 * in its stead.
2a418930 755 *
85946b6c
MD
756 * The coldpath scan does NOT rearrange threads in the run list.
757 * The lwkt_schedulerclock() will assert need_lwkt_resched() on
758 * the next tick whenever the current head is not the current thread.
f9235b6d 759 */
b12defdc 760#ifdef INVARIANTS
85946b6c
MD
761 ++token_contention_count[ntd->td_pri];
762 ++ntd->td_contended;
b12defdc
MD
763#endif
764
85946b6c 765 if (fairq_bypass > 0)
b12defdc
MD
766 goto skip;
767
b12defdc
MD
768 xtd = NULL;
769 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
85946b6c
MD
770 /*
771 * Never schedule threads returning to userland or the
772 * user thread scheduler helper thread when higher priority
773 * threads are present.
774 */
775 if (ntd->td_pri < TDPRI_KERN_LPSCHED) {
776 ntd = NULL;
777 break;
778 }
779
780 /*
781 * Try this one.
782 */
b12defdc
MD
783 if (TD_TOKS_NOT_HELD(ntd) ||
784 lwkt_getalltokens(ntd, (spinning >= lwkt_spin_loops))) {
785 goto havethread;
786 }
85946b6c
MD
787#ifdef INVARIANTS
788 ++token_contention_count[ntd->td_pri];
789 ++ntd->td_contended;
b12defdc 790#endif
2a418930
MD
791 }
792
b12defdc 793skip:
2a418930
MD
794 /*
795 * We exhausted the run list, meaning that all runnable threads
b12defdc 796 * are contested.
2a418930
MD
797 */
798 cpu_pause();
799 ntd = &gd->gd_idlethread;
800#ifdef SMP
801 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
802 ASSERT_NO_TOKENS_HELD(ntd);
803 /* contention case, do not clear contention mask */
804#endif
805
806 /*
b12defdc
MD
807 * We are going to have to retry but if the current thread is not
808 * on the runq we instead switch through the idle thread to get away
809 * from the current thread. We have to flag for lwkt reschedule
810 * to prevent the idle thread from halting.
2a418930 811 *
b12defdc
MD
812 * NOTE: A non-zero spinning is passed to lwkt_getalltokens() to
813 * instruct it to deal with the potential for deadlocks by
814 * ordering the tokens by address.
2a418930 815 */
b12defdc 816 if ((td->td_flags & TDF_RUNQ) == 0) {
85946b6c 817 need_lwkt_resched(); /* prevent hlt */
2a418930 818 goto haveidle;
4b5f931b 819 }
bd52bedf 820#if defined(INVARIANTS) && defined(__amd64__)
d5b2d319
MD
821 if ((read_rflags() & PSL_I) == 0) {
822 cpu_enable_intr();
823 panic("lwkt_switch() called with interrupts disabled");
824 }
825#endif
b12defdc
MD
826
827 /*
828 * Number iterations so far. After a certain point we switch to
829 * a sorted-address/monitor/mwait version of lwkt_getalltokens()
830 */
831 if (spinning < 0x7FFFFFFF)
832 ++spinning;
833
834#ifdef SMP
835 /*
836 * lwkt_getalltokens() failed in sorted token mode, we can use
837 * monitor/mwait in this case.
838 */
839 if (spinning >= lwkt_spin_loops &&
840 (cpu_mi_feature & CPU_MI_MONITOR) &&
841 lwkt_spin_monitor)
842 {
843 cpu_mmw_pause_int(&gd->gd_reqflags,
844 (gd->gd_reqflags | RQF_SPINNING) &
845 ~RQF_IDLECHECK_WK_MASK);
846 }
847#endif
848
849 /*
850 * We already checked that td is still scheduled so this should be
851 * safe.
852 */
853 splz_check();
854
855 /*
856 * This experimental resequencer is used as a fall-back to reduce
857 * hw cache line contention by placing each core's scheduler into a
858 * time-domain-multplexed slot.
859 *
860 * The resequencer is disabled by default. It's functionality has
861 * largely been superceeded by the token algorithm which limits races
862 * to a subset of cores.
863 *
864 * The resequencer algorithm tends to break down when more than
865 * 20 cores are contending. What appears to happen is that new
866 * tokens can be obtained out of address-sorted order by new cores
867 * while existing cores languish in long delays between retries and
868 * wind up being starved-out of the token acquisition.
869 */
870 if (lwkt_spin_reseq && spinning >= lwkt_spin_reseq) {
871 int cseq = atomic_fetchadd_int(&lwkt_cseq_windex, 1);
872 int oseq;
873
874 while ((oseq = lwkt_cseq_rindex) != cseq) {
875 cpu_ccfence();
876#if 1
877 if (cpu_mi_feature & CPU_MI_MONITOR) {
878 cpu_mmw_pause_int(&lwkt_cseq_rindex, oseq);
879 } else {
880#endif
881 cpu_pause();
882 cpu_lfence();
883#if 1
884 }
8b402283 885#endif
0f0466c0 886 }
b12defdc
MD
887 DELAY(1);
888 atomic_add_int(&lwkt_cseq_rindex, 1);
2a418930 889 }
2a418930 890 /* highest level for(;;) loop */
f1d1c3fa 891 }
8a8d5d85 892
2a418930 893havethread:
b12defdc 894 /*
f9235b6d
MD
895 * If the thread we came up with is a higher or equal priority verses
896 * the thread at the head of the queue we move our thread to the
897 * front. This way we can always check the front of the queue.
be71787b
MD
898 *
899 * Clear gd_idle_repeat when doing a normal switch to a non-idle
900 * thread.
f9235b6d 901 */
9ac1ee6e 902 ntd->td_wmesg = NULL;
b12defdc 903 ++gd->gd_cnt.v_swtch;
85946b6c 904#if 0
f9235b6d
MD
905 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
906 if (ntd != xtd && ntd->td_pri >= xtd->td_pri) {
907 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq);
908 TAILQ_INSERT_HEAD(&gd->gd_tdrunq, ntd, td_threadq);
909 }
85946b6c 910#endif
be71787b 911 gd->gd_idle_repeat = 0;
2a418930 912
f9235b6d 913havethread_preempted:
f9235b6d
MD
914 /*
915 * If the new target does not need the MP lock and we are holding it,
916 * release the MP lock. If the new target requires the MP lock we have
917 * already acquired it for the target.
8a8d5d85 918 */
2a418930 919 ;
f9235b6d
MD
920haveidle:
921 KASSERT(ntd->td_critcount,
b5d16701
MD
922 ("priority problem in lwkt_switch %d %d",
923 td->td_critcount, ntd->td_critcount));
924
94f6d86e 925 if (td != ntd) {
cc9b6223
MD
926 /*
927 * Execute the actual thread switch operation. This function
928 * returns to the current thread and returns the previous thread
929 * (which may be different from the thread we switched to).
930 *
931 * We are responsible for marking ntd as TDF_RUNNING.
932 */
94f6d86e 933 ++switch_count;
a1f0fb66 934 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
cc9b6223
MD
935 ntd->td_flags |= TDF_RUNNING;
936 lwkt_switch_return(td->td_switch(ntd));
937 /* ntd invalid, td_switch() can return a different thread_t */
94f6d86e 938 }
b12defdc
MD
939
940#if 1
941 /*
942 * catch-all
943 */
944 splz_check();
945#endif
37af14fe
MD
946 /* NOTE: current cpu may have changed after switch */
947 crit_exit_quick(td);
8ad65e08
MD
948}
949
cc9b6223
MD
950/*
951 * Called by assembly in the td_switch (thread restore path) for thread
952 * bootstrap cases which do not 'return' to lwkt_switch().
953 */
954void
955lwkt_switch_return(thread_t otd)
956{
957#ifdef SMP
958 globaldata_t rgd;
959
960 /*
961 * Check if otd was migrating. Now that we are on ntd we can finish
962 * up the migration. This is a bit messy but it is the only place
963 * where td is known to be fully descheduled.
964 *
965 * We can only activate the migration if otd was migrating but not
966 * held on the cpu due to a preemption chain. We still have to
967 * clear TDF_RUNNING on the old thread either way.
968 *
969 * We are responsible for clearing the previously running thread's
970 * TDF_RUNNING.
971 */
972 if ((rgd = otd->td_migrate_gd) != NULL &&
973 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
974 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
975 (TDF_MIGRATING | TDF_RUNNING));
976 otd->td_migrate_gd = NULL;
977 otd->td_flags &= ~TDF_RUNNING;
978 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
979 } else {
980 otd->td_flags &= ~TDF_RUNNING;
981 }
982#else
983 otd->td_flags &= ~TDF_RUNNING;
984#endif
985}
986
b68b7282 987/*
96728c05
MD
988 * Request that the target thread preempt the current thread. Preemption
989 * only works under a specific set of conditions:
b68b7282 990 *
96728c05
MD
991 * - We are not preempting ourselves
992 * - The target thread is owned by the current cpu
993 * - We are not currently being preempted
994 * - The target is not currently being preempted
d3d1cbc8
MD
995 * - We are not holding any spin locks
996 * - The target thread is not holding any tokens
96728c05
MD
997 * - We are able to satisfy the target's MP lock requirements (if any).
998 *
999 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
1000 * this is called via lwkt_schedule() through the td_preemptable callback.
f9235b6d 1001 * critcount is the managed critical priority that we should ignore in order
96728c05
MD
1002 * to determine whether preemption is possible (aka usually just the crit
1003 * priority of lwkt_schedule() itself).
b68b7282 1004 *
26a0694b
MD
1005 * XXX at the moment we run the target thread in a critical section during
1006 * the preemption in order to prevent the target from taking interrupts
1007 * that *WE* can't. Preemption is strictly limited to interrupt threads
1008 * and interrupt-like threads, outside of a critical section, and the
1009 * preempted source thread will be resumed the instant the target blocks
1010 * whether or not the source is scheduled (i.e. preemption is supposed to
1011 * be as transparent as possible).
b68b7282
MD
1012 */
1013void
f9235b6d 1014lwkt_preempt(thread_t ntd, int critcount)
b68b7282 1015{
46a3f46d 1016 struct globaldata *gd = mycpu;
cc9b6223 1017 thread_t xtd;
0a3f9b47 1018 thread_t td;
2d910aaf 1019 int save_gd_intr_nesting_level;
b68b7282 1020
26a0694b 1021 /*
96728c05
MD
1022 * The caller has put us in a critical section. We can only preempt
1023 * if the caller of the caller was not in a critical section (basically
f9235b6d 1024 * a local interrupt), as determined by the 'critcount' parameter. We
47737962 1025 * also can't preempt if the caller is holding any spinlocks (even if
d666840a 1026 * he isn't in a critical section). This also handles the tokens test.
96728c05
MD
1027 *
1028 * YYY The target thread must be in a critical section (else it must
1029 * inherit our critical section? I dunno yet).
26a0694b 1030 */
f9235b6d 1031 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
26a0694b 1032
b12defdc 1033 td = gd->gd_curthread;
fbc024e4 1034 if (preempt_enable == 0) {
85946b6c 1035#if 0
b12defdc
MD
1036 if (ntd->td_pri > td->td_pri)
1037 need_lwkt_resched();
85946b6c 1038#endif
fbc024e4
MD
1039 ++preempt_miss;
1040 return;
1041 }
f9235b6d 1042 if (ntd->td_pri <= td->td_pri) {
57c254db
MD
1043 ++preempt_miss;
1044 return;
1045 }
f9235b6d 1046 if (td->td_critcount > critcount) {
96728c05 1047 ++preempt_miss;
85946b6c 1048#if 0
8ec60c3f 1049 need_lwkt_resched();
85946b6c 1050#endif
96728c05
MD
1051 return;
1052 }
1053#ifdef SMP
46a3f46d 1054 if (ntd->td_gd != gd) {
96728c05 1055 ++preempt_miss;
85946b6c 1056#if 0
8ec60c3f 1057 need_lwkt_resched();
85946b6c 1058#endif
96728c05
MD
1059 return;
1060 }
1061#endif
41a01a4d 1062 /*
77912481
MD
1063 * We don't have to check spinlocks here as they will also bump
1064 * td_critcount.
d3d1cbc8
MD
1065 *
1066 * Do not try to preempt if the target thread is holding any tokens.
1067 * We could try to acquire the tokens but this case is so rare there
1068 * is no need to support it.
41a01a4d 1069 */
77912481
MD
1070 KKASSERT(gd->gd_spinlocks_wr == 0);
1071
3b998fa9 1072 if (TD_TOKS_HELD(ntd)) {
d3d1cbc8 1073 ++preempt_miss;
85946b6c 1074#if 0
d3d1cbc8 1075 need_lwkt_resched();
85946b6c 1076#endif
d3d1cbc8
MD
1077 return;
1078 }
26a0694b
MD
1079 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
1080 ++preempt_weird;
85946b6c 1081#if 0
8ec60c3f 1082 need_lwkt_resched();
85946b6c 1083#endif
26a0694b
MD
1084 return;
1085 }
1086 if (ntd->td_preempted) {
4b5f931b 1087 ++preempt_hit;
85946b6c 1088#if 0
8ec60c3f 1089 need_lwkt_resched();
85946b6c 1090#endif
26a0694b 1091 return;
b68b7282 1092 }
da0b0e8b 1093 KKASSERT(gd->gd_processing_ipiq == 0);
26a0694b 1094
8ec60c3f
MD
1095 /*
1096 * Since we are able to preempt the current thread, there is no need to
1097 * call need_lwkt_resched().
2d910aaf
MD
1098 *
1099 * We must temporarily clear gd_intr_nesting_level around the switch
1100 * since switchouts from the target thread are allowed (they will just
1101 * return to our thread), and since the target thread has its own stack.
cc9b6223
MD
1102 *
1103 * A preemption must switch back to the original thread, assert the
1104 * case.
8ec60c3f 1105 */
26a0694b
MD
1106 ++preempt_hit;
1107 ntd->td_preempted = td;
1108 td->td_flags |= TDF_PREEMPT_LOCK;
a1f0fb66 1109 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
2d910aaf
MD
1110 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1111 gd->gd_intr_nesting_level = 0;
cc9b6223
MD
1112 ntd->td_flags |= TDF_RUNNING;
1113 xtd = td->td_switch(ntd);
1114 KKASSERT(xtd == ntd);
1115 lwkt_switch_return(xtd);
2d910aaf 1116 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
b9eb1c19 1117
26a0694b
MD
1118 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1119 ntd->td_preempted = NULL;
1120 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
b68b7282
MD
1121}
1122
f1d1c3fa 1123/*
faaeffac 1124 * Conditionally call splz() if gd_reqflags indicates work is pending.
4a28fe22
MD
1125 * This will work inside a critical section but not inside a hard code
1126 * section.
ef0fdad1 1127 *
f1d1c3fa
MD
1128 * (self contained on a per cpu basis)
1129 */
1130void
faaeffac 1131splz_check(void)
f1d1c3fa 1132{
7966cb69
MD
1133 globaldata_t gd = mycpu;
1134 thread_t td = gd->gd_curthread;
ef0fdad1 1135
4a28fe22
MD
1136 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1137 gd->gd_intr_nesting_level == 0 &&
1138 td->td_nest_count < 2)
1139 {
f1d1c3fa 1140 splz();
4a28fe22
MD
1141 }
1142}
1143
1144/*
1145 * This version is integrated into crit_exit, reqflags has already
1146 * been tested but td_critcount has not.
1147 *
1148 * We only want to execute the splz() on the 1->0 transition of
1149 * critcount and not in a hard code section or if too deeply nested.
1150 */
1151void
1152lwkt_maybe_splz(thread_t td)
1153{
1154 globaldata_t gd = td->td_gd;
1155
1156 if (td->td_critcount == 0 &&
1157 gd->gd_intr_nesting_level == 0 &&
1158 td->td_nest_count < 2)
1159 {
1160 splz();
1161 }
f1d1c3fa
MD
1162}
1163
e6546af9
MD
1164/*
1165 * Drivers which set up processing co-threads can call this function to
1166 * run the co-thread at a higher priority and to allow it to preempt
1167 * normal threads.
1168 */
1169void
1170lwkt_set_interrupt_support_thread(void)
1171{
1172 thread_t td = curthread;
1173
1174 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1175 td->td_flags |= TDF_INTTHREAD;
1176 td->td_preemptable = lwkt_preempt;
1177}
1178
1179
8ad65e08 1180/*
f9235b6d
MD
1181 * This function is used to negotiate a passive release of the current
1182 * process/lwp designation with the user scheduler, allowing the user
1183 * scheduler to schedule another user thread. The related kernel thread
1184 * (curthread) continues running in the released state.
8ad65e08
MD
1185 */
1186void
f9235b6d 1187lwkt_passive_release(struct thread *td)
8ad65e08 1188{
f9235b6d
MD
1189 struct lwp *lp = td->td_lwp;
1190
1191 td->td_release = NULL;
1192 lwkt_setpri_self(TDPRI_KERN_USER);
1193 lp->lwp_proc->p_usched->release_curproc(lp);
f1d1c3fa
MD
1194}
1195
f9235b6d 1196
3824f392 1197/*
d2d8515b
MD
1198 * This implements a LWKT yield, allowing a kernel thread to yield to other
1199 * kernel threads at the same or higher priority. This function can be
1200 * called in a tight loop and will typically only yield once per tick.
f9235b6d 1201 *
d2d8515b
MD
1202 * Most kernel threads run at the same priority in order to allow equal
1203 * sharing.
f9235b6d
MD
1204 *
1205 * (self contained on a per cpu basis)
3824f392
MD
1206 */
1207void
f9235b6d 1208lwkt_yield(void)
3824f392 1209{
f9235b6d
MD
1210 globaldata_t gd = mycpu;
1211 thread_t td = gd->gd_curthread;
3824f392 1212
f9235b6d
MD
1213 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1214 splz();
85946b6c 1215 if (lwkt_resched_wanted()) {
f9235b6d
MD
1216 lwkt_schedule_self(curthread);
1217 lwkt_switch();
f9235b6d 1218 }
3824f392
MD
1219}
1220
1221/*
f9235b6d
MD
1222 * This yield is designed for kernel threads with a user context.
1223 *
1224 * The kernel acting on behalf of the user is potentially cpu-bound,
1225 * this function will efficiently allow other threads to run and also
1226 * switch to other processes by releasing.
3824f392
MD
1227 *
1228 * The lwkt_user_yield() function is designed to have very low overhead
1229 * if no yield is determined to be needed.
1230 */
1231void
1232lwkt_user_yield(void)
1233{
f9235b6d
MD
1234 globaldata_t gd = mycpu;
1235 thread_t td = gd->gd_curthread;
1236
1237 /*
1238 * Always run any pending interrupts in case we are in a critical
1239 * section.
1240 */
1241 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1242 splz();
3824f392 1243
3824f392 1244 /*
f9235b6d
MD
1245 * Switch (which forces a release) if another kernel thread needs
1246 * the cpu, if userland wants us to resched, or if our kernel
1247 * quantum has run out.
3824f392 1248 */
f9235b6d 1249 if (lwkt_resched_wanted() ||
85946b6c 1250 user_resched_wanted())
f9235b6d 1251 {
3824f392 1252 lwkt_switch();
3824f392
MD
1253 }
1254
f9235b6d 1255#if 0
3824f392 1256 /*
f9235b6d
MD
1257 * Reacquire the current process if we are released.
1258 *
1259 * XXX not implemented atm. The kernel may be holding locks and such,
1260 * so we want the thread to continue to receive cpu.
3824f392 1261 */
f9235b6d
MD
1262 if (td->td_release == NULL && lp) {
1263 lp->lwp_proc->p_usched->acquire_curproc(lp);
1264 td->td_release = lwkt_passive_release;
1265 lwkt_setpri_self(TDPRI_USER_NORM);
3824f392 1266 }
f9235b6d 1267#endif
b9eb1c19
MD
1268}
1269
8ad65e08 1270/*
f1d1c3fa
MD
1271 * Generic schedule. Possibly schedule threads belonging to other cpus and
1272 * deal with threads that might be blocked on a wait queue.
1273 *
0a3f9b47
MD
1274 * We have a little helper inline function which does additional work after
1275 * the thread has been enqueued, including dealing with preemption and
1276 * setting need_lwkt_resched() (which prevents the kernel from returning
1277 * to userland until it has processed higher priority threads).
6330a558
MD
1278 *
1279 * It is possible for this routine to be called after a failed _enqueue
1280 * (due to the target thread migrating, sleeping, or otherwise blocked).
1281 * We have to check that the thread is actually on the run queue!
8ad65e08 1282 */
0a3f9b47
MD
1283static __inline
1284void
85946b6c 1285_lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
0a3f9b47 1286{
6330a558 1287 if (ntd->td_flags & TDF_RUNQ) {
85946b6c 1288 if (ntd->td_preemptable) {
f9235b6d 1289 ntd->td_preemptable(ntd, ccount); /* YYY +token */
6330a558 1290 }
0a3f9b47
MD
1291 }
1292}
1293
361d01dd 1294static __inline
8ad65e08 1295void
85946b6c 1296_lwkt_schedule(thread_t td)
8ad65e08 1297{
37af14fe
MD
1298 globaldata_t mygd = mycpu;
1299
cf709dd2
MD
1300 KASSERT(td != &td->td_gd->gd_idlethread,
1301 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
cfaeae2a 1302 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
37af14fe 1303 crit_enter_gd(mygd);
9388413d 1304 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
37af14fe 1305 if (td == mygd->gd_curthread) {
f1d1c3fa
MD
1306 _lwkt_enqueue(td);
1307 } else {
f1d1c3fa 1308 /*
7cd8d145
MD
1309 * If we own the thread, there is no race (since we are in a
1310 * critical section). If we do not own the thread there might
1311 * be a race but the target cpu will deal with it.
f1d1c3fa 1312 */
0f7a3396 1313#ifdef SMP
7cd8d145 1314 if (td->td_gd == mygd) {
9d265729 1315 _lwkt_enqueue(td);
85946b6c 1316 _lwkt_schedule_post(mygd, td, 1);
f1d1c3fa 1317 } else {
e381e77c 1318 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
7cd8d145 1319 }
0f7a3396 1320#else
7cd8d145 1321 _lwkt_enqueue(td);
85946b6c 1322 _lwkt_schedule_post(mygd, td, 1);
0f7a3396 1323#endif
8ad65e08 1324 }
37af14fe 1325 crit_exit_gd(mygd);
8ad65e08
MD
1326}
1327
361d01dd
MD
1328void
1329lwkt_schedule(thread_t td)
1330{
85946b6c 1331 _lwkt_schedule(td);
361d01dd
MD
1332}
1333
1334void
85946b6c 1335lwkt_schedule_noresched(thread_t td) /* XXX not impl */
361d01dd 1336{
85946b6c 1337 _lwkt_schedule(td);
361d01dd
MD
1338}
1339
88ebb169
SW
1340#ifdef SMP
1341
e381e77c
MD
1342/*
1343 * When scheduled remotely if frame != NULL the IPIQ is being
1344 * run via doreti or an interrupt then preemption can be allowed.
1345 *
1346 * To allow preemption we have to drop the critical section so only
1347 * one is present in _lwkt_schedule_post.
1348 */
1349static void
1350lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1351{
1352 thread_t td = curthread;
1353 thread_t ntd = arg;
1354
1355 if (frame && ntd->td_preemptable) {
1356 crit_exit_noyield(td);
85946b6c 1357 _lwkt_schedule(ntd);
e381e77c
MD
1358 crit_enter_quick(td);
1359 } else {
85946b6c 1360 _lwkt_schedule(ntd);
e381e77c
MD
1361 }
1362}
1363
d9eea1a5 1364/*
52eedfb5
MD
1365 * Thread migration using a 'Pull' method. The thread may or may not be
1366 * the current thread. It MUST be descheduled and in a stable state.
1367 * lwkt_giveaway() must be called on the cpu owning the thread.
1368 *
1369 * At any point after lwkt_giveaway() is called, the target cpu may
1370 * 'pull' the thread by calling lwkt_acquire().
1371 *
ae8e83e6
MD
1372 * We have to make sure the thread is not sitting on a per-cpu tsleep
1373 * queue or it will blow up when it moves to another cpu.
1374 *
52eedfb5 1375 * MPSAFE - must be called under very specific conditions.
d9eea1a5 1376 */
52eedfb5
MD
1377void
1378lwkt_giveaway(thread_t td)
1379{
3b4192fb 1380 globaldata_t gd = mycpu;
52eedfb5 1381
3b4192fb
MD
1382 crit_enter_gd(gd);
1383 if (td->td_flags & TDF_TSLEEPQ)
1384 tsleep_remove(td);
1385 KKASSERT(td->td_gd == gd);
1386 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1387 td->td_flags |= TDF_MIGRATING;
1388 crit_exit_gd(gd);
52eedfb5
MD
1389}
1390
a2a5ad0d
MD
1391void
1392lwkt_acquire(thread_t td)
1393{
37af14fe
MD
1394 globaldata_t gd;
1395 globaldata_t mygd;
cc9b6223 1396 int retry = 10000000;
a2a5ad0d 1397
52eedfb5 1398 KKASSERT(td->td_flags & TDF_MIGRATING);
a2a5ad0d 1399 gd = td->td_gd;
37af14fe 1400 mygd = mycpu;
52eedfb5 1401 if (gd != mycpu) {
35238fa5 1402 cpu_lfence();
52eedfb5 1403 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
37af14fe 1404 crit_enter_gd(mygd);
cfaeae2a 1405 DEBUG_PUSH_INFO("lwkt_acquire");
df910c23
MD
1406 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1407#ifdef SMP
1408 lwkt_process_ipiq();
1409#endif
52eedfb5 1410 cpu_lfence();
cc9b6223
MD
1411 if (--retry == 0) {
1412 kprintf("lwkt_acquire: stuck: td %p td->td_flags %08x\n",
1413 td, td->td_flags);
1414 retry = 10000000;
1415 }
df910c23 1416 }
cfaeae2a 1417 DEBUG_POP_INFO();
562273ea 1418 cpu_mfence();
37af14fe 1419 td->td_gd = mygd;
52eedfb5
MD
1420 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1421 td->td_flags &= ~TDF_MIGRATING;
1422 crit_exit_gd(mygd);
1423 } else {
1424 crit_enter_gd(mygd);
1425 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1426 td->td_flags &= ~TDF_MIGRATING;
37af14fe 1427 crit_exit_gd(mygd);
a2a5ad0d
MD
1428 }
1429}
1430
52eedfb5
MD
1431#endif
1432
f1d1c3fa
MD
1433/*
1434 * Generic deschedule. Descheduling threads other then your own should be
1435 * done only in carefully controlled circumstances. Descheduling is
1436 * asynchronous.
1437 *
1438 * This function may block if the cpu has run out of messages.
8ad65e08
MD
1439 */
1440void
1441lwkt_deschedule(thread_t td)
1442{
f1d1c3fa 1443 crit_enter();
b8a98473 1444#ifdef SMP
f1d1c3fa
MD
1445 if (td == curthread) {
1446 _lwkt_dequeue(td);
1447 } else {
a72187e9 1448 if (td->td_gd == mycpu) {
f1d1c3fa
MD
1449 _lwkt_dequeue(td);
1450 } else {
b8a98473 1451 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
f1d1c3fa
MD
1452 }
1453 }
b8a98473
MD
1454#else
1455 _lwkt_dequeue(td);
1456#endif
f1d1c3fa
MD
1457 crit_exit();
1458}
1459
4b5f931b
MD
1460/*
1461 * Set the target thread's priority. This routine does not automatically
1462 * switch to a higher priority thread, LWKT threads are not designed for
1463 * continuous priority changes. Yield if you want to switch.
4b5f931b
MD
1464 */
1465void
1466lwkt_setpri(thread_t td, int pri)
1467{
f9235b6d
MD
1468 if (td->td_pri != pri) {
1469 KKASSERT(pri >= 0);
1470 crit_enter();
1471 if (td->td_flags & TDF_RUNQ) {
d2d8515b 1472 KKASSERT(td->td_gd == mycpu);
f9235b6d
MD
1473 _lwkt_dequeue(td);
1474 td->td_pri = pri;
1475 _lwkt_enqueue(td);
1476 } else {
1477 td->td_pri = pri;
1478 }
1479 crit_exit();
26a0694b 1480 }
26a0694b
MD
1481}
1482
03bd0a5e
MD
1483/*
1484 * Set the initial priority for a thread prior to it being scheduled for
1485 * the first time. The thread MUST NOT be scheduled before or during
1486 * this call. The thread may be assigned to a cpu other then the current
1487 * cpu.
1488 *
1489 * Typically used after a thread has been created with TDF_STOPPREQ,
1490 * and before the thread is initially scheduled.
1491 */
1492void
1493lwkt_setpri_initial(thread_t td, int pri)
1494{
1495 KKASSERT(pri >= 0);
1496 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
f9235b6d 1497 td->td_pri = pri;
03bd0a5e
MD
1498}
1499
26a0694b
MD
1500void
1501lwkt_setpri_self(int pri)
1502{
1503 thread_t td = curthread;
1504
4b5f931b
MD
1505 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1506 crit_enter();
1507 if (td->td_flags & TDF_RUNQ) {
1508 _lwkt_dequeue(td);
f9235b6d 1509 td->td_pri = pri;
4b5f931b
MD
1510 _lwkt_enqueue(td);
1511 } else {
f9235b6d 1512 td->td_pri = pri;
4b5f931b
MD
1513 }
1514 crit_exit();
1515}
1516
f9235b6d 1517/*
85946b6c 1518 * hz tick scheduler clock for LWKT threads
f9235b6d
MD
1519 */
1520void
85946b6c 1521lwkt_schedulerclock(thread_t td)
f9235b6d 1522{
85946b6c
MD
1523 globaldata_t gd = td->td_gd;
1524 thread_t xtd;
2a418930 1525
85946b6c
MD
1526 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1527 /*
1528 * If the current thread is at the head of the runq shift it to the
1529 * end of any equal-priority threads and request a LWKT reschedule
1530 * if it moved.
1531 */
1532 xtd = TAILQ_NEXT(td, td_threadq);
1533 if (xtd && xtd->td_pri == td->td_pri) {
1534 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1535 while (xtd && xtd->td_pri == td->td_pri)
1536 xtd = TAILQ_NEXT(xtd, td_threadq);
1537 if (xtd)
1538 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1539 else
1540 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1541 need_lwkt_resched();
f9235b6d 1542 }
85946b6c
MD
1543 } else {
1544 /*
1545 * If we scheduled a thread other than the one at the head of the
1546 * queue always request a reschedule every tick.
1547 */
1548 need_lwkt_resched();
f9235b6d
MD
1549 }
1550}
1551
5d21b981 1552/*
52eedfb5
MD
1553 * Migrate the current thread to the specified cpu.
1554 *
cc9b6223
MD
1555 * This is accomplished by descheduling ourselves from the current cpu
1556 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1557 * 'old' thread wants to migrate after it has been completely switched out
1558 * and will complete the migration.
1559 *
1560 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1561 *
1562 * We must be sure to release our current process designation (if a user
1563 * process) before clearing out any tsleepq we are on because the release
1564 * code may re-add us.
ae8e83e6
MD
1565 *
1566 * We must be sure to remove ourselves from the current cpu's tsleepq
1567 * before potentially moving to another queue. The thread can be on
1568 * a tsleepq due to a left-over tsleep_interlock().
5d21b981 1569 */
5d21b981
MD
1570
1571void
1572lwkt_setcpu_self(globaldata_t rgd)
1573{
1574#ifdef SMP
1575 thread_t td = curthread;
1576
1577 if (td->td_gd != rgd) {
1578 crit_enter_quick(td);
cc9b6223 1579
95858b91
MD
1580 if (td->td_release)
1581 td->td_release(td);
ae8e83e6 1582 if (td->td_flags & TDF_TSLEEPQ)
3b4192fb 1583 tsleep_remove(td);
cc9b6223
MD
1584
1585 /*
1586 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1587 * trying to deschedule ourselves and switch away, then deschedule
1588 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1589 * call lwkt_switch() to complete the operation.
1590 */
5d21b981
MD
1591 td->td_flags |= TDF_MIGRATING;
1592 lwkt_deschedule_self(td);
52eedfb5 1593 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
cc9b6223 1594 td->td_migrate_gd = rgd;
5d21b981 1595 lwkt_switch();
cc9b6223
MD
1596
1597 /*
1598 * We are now on the target cpu
1599 */
1600 KKASSERT(rgd == mycpu);
52eedfb5 1601 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
5d21b981
MD
1602 crit_exit_quick(td);
1603 }
1604#endif
1605}
1606
ecdefdda
MD
1607void
1608lwkt_migratecpu(int cpuid)
1609{
1610#ifdef SMP
1611 globaldata_t rgd;
1612
1613 rgd = globaldata_find(cpuid);
1614 lwkt_setcpu_self(rgd);
1615#endif
1616}
1617
cc9b6223 1618#ifdef SMP
5d21b981
MD
1619/*
1620 * Remote IPI for cpu migration (called while in a critical section so we
cc9b6223
MD
1621 * do not have to enter another one).
1622 *
1623 * The thread (td) has already been completely descheduled from the
1624 * originating cpu and we can simply assert the case. The thread is
1625 * assigned to the new cpu and enqueued.
5d21b981 1626 *
cc9b6223 1627 * The thread will re-add itself to tdallq when it resumes execution.
5d21b981
MD
1628 */
1629static void
1630lwkt_setcpu_remote(void *arg)
1631{
1632 thread_t td = arg;
1633 globaldata_t gd = mycpu;
1634
cc9b6223 1635 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
5d21b981 1636 td->td_gd = gd;
562273ea 1637 cpu_mfence();
5d21b981 1638 td->td_flags &= ~TDF_MIGRATING;
cc9b6223 1639 KKASSERT(td->td_migrate_gd == NULL);
9388413d 1640 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
5d21b981
MD
1641 _lwkt_enqueue(td);
1642}
3d28ff59 1643#endif
5d21b981 1644
553ea3c8 1645struct lwp *
4b5f931b
MD
1646lwkt_preempted_proc(void)
1647{
73e4f7b9 1648 thread_t td = curthread;
4b5f931b
MD
1649 while (td->td_preempted)
1650 td = td->td_preempted;
553ea3c8 1651 return(td->td_lwp);
4b5f931b
MD
1652}
1653
99df837e
MD
1654/*
1655 * Create a kernel process/thread/whatever. It shares it's address space
1656 * with proc0 - ie: kernel only.
1657 *
d2d8515b
MD
1658 * If the cpu is not specified one will be selected. In the future
1659 * specifying a cpu of -1 will enable kernel thread migration between
1660 * cpus.
99df837e
MD
1661 */
1662int
c9e9fb21
MD
1663lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1664 thread_t template, int tdflags, int cpu, const char *fmt, ...)
99df837e 1665{
73e4f7b9 1666 thread_t td;
e2565a42 1667 __va_list ap;
99df837e 1668
d3d32139 1669 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
dbcd0c9b 1670 tdflags);
a2a5ad0d
MD
1671 if (tdp)
1672 *tdp = td;
709799ea 1673 cpu_set_thread_handler(td, lwkt_exit, func, arg);
99df837e
MD
1674
1675 /*
1676 * Set up arg0 for 'ps' etc
1677 */
e2565a42 1678 __va_start(ap, fmt);
379210cb 1679 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
e2565a42 1680 __va_end(ap);
99df837e
MD
1681
1682 /*
1683 * Schedule the thread to run
1684 */
ef0fdad1
MD
1685 if ((td->td_flags & TDF_STOPREQ) == 0)
1686 lwkt_schedule(td);
1687 else
1688 td->td_flags &= ~TDF_STOPREQ;
99df837e
MD
1689 return 0;
1690}
1691
1692/*
1693 * Destroy an LWKT thread. Warning! This function is not called when
1694 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1695 * uses a different reaping mechanism.
1696 */
1697void
1698lwkt_exit(void)
1699{
1700 thread_t td = curthread;
c070746a 1701 thread_t std;
8826f33a 1702 globaldata_t gd;
99df837e 1703
2883d2d8
MD
1704 /*
1705 * Do any cleanup that might block here
1706 */
99df837e 1707 if (td->td_flags & TDF_VERBOSE)
6ea70f76 1708 kprintf("kthread %p %s has exited\n", td, td->td_comm);
f6bf3af1 1709 caps_exit(td);
2883d2d8
MD
1710 biosched_done(td);
1711 dsched_exit_thread(td);
c070746a
MD
1712
1713 /*
1714 * Get us into a critical section to interlock gd_freetd and loop
1715 * until we can get it freed.
1716 *
1717 * We have to cache the current td in gd_freetd because objcache_put()ing
1718 * it would rip it out from under us while our thread is still active.
1719 */
1720 gd = mycpu;
37af14fe 1721 crit_enter_quick(td);
c070746a 1722 while ((std = gd->gd_freetd) != NULL) {
cf709dd2 1723 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
c070746a
MD
1724 gd->gd_freetd = NULL;
1725 objcache_put(thread_cache, std);
1726 }
3b4192fb
MD
1727
1728 /*
1729 * Remove thread resources from kernel lists and deschedule us for
2883d2d8
MD
1730 * the last time. We cannot block after this point or we may end
1731 * up with a stale td on the tsleepq.
3b4192fb
MD
1732 */
1733 if (td->td_flags & TDF_TSLEEPQ)
1734 tsleep_remove(td);
37af14fe 1735 lwkt_deschedule_self(td);
e56e4dea 1736 lwkt_remove_tdallq(td);
74c9628e 1737 KKASSERT(td->td_refs == 0);
2883d2d8
MD
1738
1739 /*
1740 * Final cleanup
1741 */
1742 KKASSERT(gd->gd_freetd == NULL);
c070746a
MD
1743 if (td->td_flags & TDF_ALLOCATED_THREAD)
1744 gd->gd_freetd = td;
99df837e
MD
1745 cpu_thread_exit();
1746}
1747
e56e4dea
MD
1748void
1749lwkt_remove_tdallq(thread_t td)
1750{
1751 KKASSERT(td->td_gd == mycpu);
1752 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1753}
1754
9cf43f91
MD
1755/*
1756 * Code reduction and branch prediction improvements. Call/return
1757 * overhead on modern cpus often degenerates into 0 cycles due to
1758 * the cpu's branch prediction hardware and return pc cache. We
1759 * can take advantage of this by not inlining medium-complexity
1760 * functions and we can also reduce the branch prediction impact
1761 * by collapsing perfectly predictable branches into a single
1762 * procedure instead of duplicating it.
1763 *
1764 * Is any of this noticeable? Probably not, so I'll take the
1765 * smaller code size.
1766 */
1767void
b6468f56 1768crit_exit_wrapper(__DEBUG_CRIT_ARG__)
9cf43f91 1769{
b6468f56 1770 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
9cf43f91
MD
1771}
1772
2d93b37a
MD
1773void
1774crit_panic(void)
1775{
1776 thread_t td = curthread;
850634cc 1777 int lcrit = td->td_critcount;
2d93b37a 1778
850634cc
AH
1779 td->td_critcount = 0;
1780 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
4a28fe22 1781 /* NOT REACHED */
2d93b37a
MD
1782}
1783
d165e668
MD
1784#ifdef SMP
1785
bd8015ca
MD
1786/*
1787 * Called from debugger/panic on cpus which have been stopped. We must still
1788 * process the IPIQ while stopped, even if we were stopped while in a critical
1789 * section (XXX).
1790 *
1791 * If we are dumping also try to process any pending interrupts. This may
1792 * or may not work depending on the state of the cpu at the point it was
1793 * stopped.
1794 */
1795void
1796lwkt_smp_stopped(void)
1797{
1798 globaldata_t gd = mycpu;
1799
1800 crit_enter_gd(gd);
1801 if (dumping) {
1802 lwkt_process_ipiq();
1803 splz();
1804 } else {
1805 lwkt_process_ipiq();
1806 }
1807 crit_exit_gd(gd);
1808}
1809
d165e668 1810#endif