2 * Copyright (c) 2003-2011 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
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.
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
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.
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
46 #include <sys/rtprio.h>
47 #include <sys/kinfo.h>
48 #include <sys/queue.h>
49 #include <sys/sysctl.h>
50 #include <sys/kthread.h>
51 #include <machine/cpu.h>
53 #include <sys/spinlock.h>
55 #include <sys/indefinite.h>
57 #include <sys/thread2.h>
58 #include <sys/spinlock2.h>
59 #include <sys/indefinite2.h>
61 #include <sys/dsched.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>
72 #include <machine/stdarg.h>
73 #include <machine/smp.h>
74 #include <machine/clock.h>
76 #ifdef _KERNEL_VIRTUAL
82 #if !defined(KTR_CTXSW)
83 #define KTR_CTXSW KTR_ALL
85 KTR_INFO_MASTER(ctxsw);
86 KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p", int cpu, struct thread *td);
87 KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p", int cpu, struct thread *td);
88 KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s", struct thread *td, char *comm);
89 KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", struct thread *td);
91 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
94 static int panic_on_cscount = 0;
96 static int64_t switch_count = 0;
97 static int64_t preempt_hit = 0;
98 static int64_t preempt_miss = 0;
99 static int64_t preempt_weird = 0;
100 static int lwkt_use_spin_port;
101 static struct objcache *thread_cache;
102 int cpu_mwait_spin = 0;
104 static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
105 static void lwkt_setcpu_remote(void *arg);
108 * We can make all thread ports use the spin backend instead of the thread
109 * backend. This should only be set to debug the spin backend.
111 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
114 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0,
115 "Panic if attempting to switch lwkt's while mastering cpusync");
117 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0,
118 "Number of switched threads");
119 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
120 "Successful preemption events");
121 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
122 "Failed preemption events");
123 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0,
124 "Number of preempted threads.");
125 static int fairq_enable = 0;
126 SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW,
127 &fairq_enable, 0, "Turn on fairq priority accumulators");
128 static int fairq_bypass = -1;
129 SYSCTL_INT(_lwkt, OID_AUTO, fairq_bypass, CTLFLAG_RW,
130 &fairq_bypass, 0, "Allow fairq to bypass td on token failure");
131 extern int lwkt_sched_debug;
132 int lwkt_sched_debug = 0;
133 SYSCTL_INT(_lwkt, OID_AUTO, sched_debug, CTLFLAG_RW,
134 &lwkt_sched_debug, 0, "Scheduler debug");
135 static u_int lwkt_spin_loops = 10;
136 SYSCTL_UINT(_lwkt, OID_AUTO, spin_loops, CTLFLAG_RW,
137 &lwkt_spin_loops, 0, "Scheduler spin loops until sorted decon");
138 static int preempt_enable = 1;
139 SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW,
140 &preempt_enable, 0, "Enable preemption");
141 static int lwkt_cache_threads = 0;
142 SYSCTL_INT(_lwkt, OID_AUTO, cache_threads, CTLFLAG_RD,
143 &lwkt_cache_threads, 0, "thread+kstack cache");
146 * These helper procedures handle the runq, they can only be called from
147 * within a critical section.
149 * WARNING! Prior to SMP being brought up it is possible to enqueue and
150 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
151 * instead of 'mycpu' when referencing the globaldata structure. Once
152 * SMP live enqueuing and dequeueing only occurs on the current cpu.
156 _lwkt_dequeue(thread_t td)
158 if (td->td_flags & TDF_RUNQ) {
159 struct globaldata *gd = td->td_gd;
161 td->td_flags &= ~TDF_RUNQ;
162 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
163 --gd->gd_tdrunqcount;
164 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
165 atomic_clear_int(&gd->gd_reqflags, RQF_RUNNING);
172 * There are a limited number of lwkt threads runnable since user
173 * processes only schedule one at a time per cpu. However, there can
174 * be many user processes in kernel mode exiting from a tsleep() which
177 * We scan the queue in both directions to help deal with degenerate
178 * situations when hundreds or thousands (or more) threads are runnable.
180 * NOTE: lwkt_schedulerclock() will force a round-robin based on td_pri and
181 * will ignore user priority. This is to ensure that user threads in
182 * kernel mode get cpu at some point regardless of what the user
187 _lwkt_enqueue(thread_t td)
189 thread_t xtd; /* forward scan */
190 thread_t rtd; /* reverse scan */
192 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
193 struct globaldata *gd = td->td_gd;
195 td->td_flags |= TDF_RUNQ;
196 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
198 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
199 atomic_set_int(&gd->gd_reqflags, RQF_RUNNING);
202 * NOTE: td_upri - higher numbers more desireable, same sense
203 * as td_pri (typically reversed from lwp_upri).
205 * In the equal priority case we want the best selection
206 * at the beginning so the less desireable selections know
207 * that they have to setrunqueue/go-to-another-cpu, even
208 * though it means switching back to the 'best' selection.
209 * This also avoids degenerate situations when many threads
210 * are runnable or waking up at the same time.
212 * If upri matches exactly place at end/round-robin.
214 rtd = TAILQ_LAST(&gd->gd_tdrunq, lwkt_queue);
217 (xtd->td_pri > td->td_pri ||
218 (xtd->td_pri == td->td_pri &&
219 xtd->td_upri >= td->td_upri))) {
220 xtd = TAILQ_NEXT(xtd, td_threadq);
223 * Doing a reverse scan at the same time is an optimization
224 * for the insert-closer-to-tail case that avoids having to
225 * scan the entire list. This situation can occur when
226 * thousands of threads are woken up at the same time.
228 if (rtd->td_pri > td->td_pri ||
229 (rtd->td_pri == td->td_pri &&
230 rtd->td_upri >= td->td_upri)) {
231 TAILQ_INSERT_AFTER(&gd->gd_tdrunq, rtd, td, td_threadq);
234 rtd = TAILQ_PREV(rtd, lwkt_queue, td_threadq);
237 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
239 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
242 ++gd->gd_tdrunqcount;
245 * Request a LWKT reschedule if we are now at the head of the queue.
247 if (TAILQ_FIRST(&gd->gd_tdrunq) == td)
253 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
255 struct thread *td = (struct thread *)obj;
257 td->td_kstack = NULL;
258 td->td_kstack_size = 0;
259 td->td_flags = TDF_ALLOCATED_THREAD;
265 _lwkt_thread_dtor(void *obj, void *privdata)
267 struct thread *td = (struct thread *)obj;
269 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
270 ("_lwkt_thread_dtor: not allocated from objcache"));
271 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
272 td->td_kstack_size > 0,
273 ("_lwkt_thread_dtor: corrupted stack"));
274 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
275 td->td_kstack = NULL;
280 * Initialize the lwkt s/system.
282 * Nominally cache up to 32 thread + kstack structures. Cache more on
283 * systems with a lot of cpu cores.
288 TUNABLE_INT("lwkt.cache_threads", &lwkt_cache_threads);
289 if (lwkt_cache_threads == 0) {
290 lwkt_cache_threads = ncpus * 4;
291 if (lwkt_cache_threads < 32)
292 lwkt_cache_threads = 32;
294 thread_cache = objcache_create_mbacked(
295 M_THREAD, sizeof(struct thread),
296 0, lwkt_cache_threads,
297 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
299 SYSINIT(lwkt_init, SI_BOOT2_LWKT_INIT, SI_ORDER_FIRST, lwkt_init, NULL);
302 * Schedule a thread to run. As the current thread we can always safely
303 * schedule ourselves, and a shortcut procedure is provided for that
306 * (non-blocking, self contained on a per cpu basis)
309 lwkt_schedule_self(thread_t td)
311 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
312 crit_enter_quick(td);
313 KASSERT(td != &td->td_gd->gd_idlethread,
314 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
315 KKASSERT(td->td_lwp == NULL ||
316 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
322 * Deschedule a thread.
324 * (non-blocking, self contained on a per cpu basis)
327 lwkt_deschedule_self(thread_t td)
329 crit_enter_quick(td);
335 * LWKTs operate on a per-cpu basis
337 * WARNING! Called from early boot, 'mycpu' may not work yet.
340 lwkt_gdinit(struct globaldata *gd)
342 TAILQ_INIT(&gd->gd_tdrunq);
343 TAILQ_INIT(&gd->gd_tdallq);
347 * Create a new thread. The thread must be associated with a process context
348 * or LWKT start address before it can be scheduled. If the target cpu is
349 * -1 the thread will be created on the current cpu.
351 * If you intend to create a thread without a process context this function
352 * does everything except load the startup and switcher function.
355 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
357 static int cpu_rotator;
358 globaldata_t gd = mycpu;
362 * If static thread storage is not supplied allocate a thread. Reuse
363 * a cached free thread if possible. gd_freetd is used to keep an exiting
364 * thread intact through the exit.
368 if ((td = gd->gd_freetd) != NULL) {
369 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
371 gd->gd_freetd = NULL;
373 td = objcache_get(thread_cache, M_WAITOK);
374 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
378 KASSERT((td->td_flags &
379 (TDF_ALLOCATED_THREAD|TDF_RUNNING|TDF_PREEMPT_LOCK)) ==
380 TDF_ALLOCATED_THREAD,
381 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
382 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
386 * Try to reuse cached stack.
388 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
389 if (flags & TDF_ALLOCATED_STACK) {
390 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
396 stack = (void *)kmem_alloc_stack(&kernel_map, stksize, 0);
398 stack = (void *)kmem_alloc_stack(&kernel_map, stksize,
400 flags |= TDF_ALLOCATED_STACK;
405 cpu = (uint32_t)cpu % (uint32_t)ncpus;
407 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
412 * Initialize a preexisting thread structure. This function is used by
413 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
415 * All threads start out in a critical section at a priority of
416 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
417 * appropriate. This function may send an IPI message when the
418 * requested cpu is not the current cpu and consequently gd_tdallq may
419 * not be initialized synchronously from the point of view of the originating
422 * NOTE! we have to be careful in regards to creating threads for other cpus
423 * if SMP has not yet been activated.
426 lwkt_init_thread_remote(void *arg)
431 * Protected by critical section held by IPI dispatch
433 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
437 * lwkt core thread structural initialization.
439 * NOTE: All threads are initialized as mpsafe threads.
442 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
443 struct globaldata *gd)
445 globaldata_t mygd = mycpu;
447 bzero(td, sizeof(struct thread));
448 td->td_kstack = stack;
449 td->td_kstack_size = stksize;
450 td->td_flags = flags;
452 td->td_type = TD_TYPE_GENERIC;
454 td->td_pri = TDPRI_KERN_DAEMON;
455 td->td_critcount = 1;
456 td->td_toks_have = NULL;
457 td->td_toks_stop = &td->td_toks_base;
458 if (lwkt_use_spin_port || (flags & TDF_FORCE_SPINPORT)) {
459 lwkt_initport_spin(&td->td_msgport, td,
460 (flags & TDF_FIXEDCPU) ? TRUE : FALSE);
462 lwkt_initport_thread(&td->td_msgport, td);
464 pmap_init_thread(td);
466 * Normally initializing a thread for a remote cpu requires sending an
467 * IPI. However, the idlethread is setup before the other cpus are
468 * activated so we have to treat it as a special case. XXX manipulation
469 * of gd_tdallq requires the BGL.
471 if (gd == mygd || td == &gd->gd_idlethread) {
473 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
476 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
478 dsched_enter_thread(td);
482 lwkt_set_comm(thread_t td, const char *ctl, ...)
487 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
489 KTR_LOG(ctxsw_newtd, td, td->td_comm);
493 * Prevent the thread from getting destroyed. Note that unlike PHOLD/PRELE
494 * this does not prevent the thread from migrating to another cpu so the
495 * gd_tdallq state is not protected by this.
498 lwkt_hold(thread_t td)
500 atomic_add_int(&td->td_refs, 1);
504 lwkt_rele(thread_t td)
506 KKASSERT(td->td_refs > 0);
507 atomic_add_int(&td->td_refs, -1);
511 lwkt_free_thread(thread_t td)
513 KKASSERT(td->td_refs == 0);
514 KKASSERT((td->td_flags & (TDF_RUNNING | TDF_PREEMPT_LOCK |
515 TDF_RUNQ | TDF_TSLEEPQ)) == 0);
516 if (td->td_flags & TDF_ALLOCATED_THREAD) {
517 objcache_put(thread_cache, td);
518 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
519 /* client-allocated struct with internally allocated stack */
520 KASSERT(td->td_kstack && td->td_kstack_size > 0,
521 ("lwkt_free_thread: corrupted stack"));
522 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
523 td->td_kstack = NULL;
524 td->td_kstack_size = 0;
527 KTR_LOG(ctxsw_deadtd, td);
532 * Switch to the next runnable lwkt. If no LWKTs are runnable then
533 * switch to the idlethread. Switching must occur within a critical
534 * section to avoid races with the scheduling queue.
536 * We always have full control over our cpu's run queue. Other cpus
537 * that wish to manipulate our queue must use the cpu_*msg() calls to
538 * talk to our cpu, so a critical section is all that is needed and
539 * the result is very, very fast thread switching.
541 * The LWKT scheduler uses a fixed priority model and round-robins at
542 * each priority level. User process scheduling is a totally
543 * different beast and LWKT priorities should not be confused with
544 * user process priorities.
546 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
547 * is not called by the current thread in the preemption case, only when
548 * the preempting thread blocks (in order to return to the original thread).
550 * SPECIAL NOTE ON SWITCH ATOMICY: Certain operations such as thread
551 * migration and tsleep deschedule the current lwkt thread and call
552 * lwkt_switch(). In particular, the target cpu of the migration fully
553 * expects the thread to become non-runnable and can deadlock against
554 * cpusync operations if we run any IPIs prior to switching the thread out.
556 * WE MUST BE VERY CAREFUL NOT TO RUN SPLZ DIRECTLY OR INDIRECTLY IF
557 * THE CURRENT THREAD HAS BEEN DESCHEDULED!
562 globaldata_t gd = mycpu;
563 thread_t td = gd->gd_curthread;
568 uint64_t tsc_base = rdtsc();
571 KKASSERT(gd->gd_processing_ipiq == 0);
572 KKASSERT(td->td_flags & TDF_RUNNING);
575 * Switching from within a 'fast' (non thread switched) interrupt or IPI
576 * is illegal. However, we may have to do it anyway if we hit a fatal
577 * kernel trap or we have paniced.
579 * If this case occurs save and restore the interrupt nesting level.
581 if (gd->gd_intr_nesting_level) {
585 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
586 panic("lwkt_switch: Attempt to switch from a "
587 "fast interrupt, ipi, or hard code section, "
591 savegdnest = gd->gd_intr_nesting_level;
592 savegdtrap = gd->gd_trap_nesting_level;
593 gd->gd_intr_nesting_level = 0;
594 gd->gd_trap_nesting_level = 0;
595 if ((td->td_flags & TDF_PANICWARN) == 0) {
596 td->td_flags |= TDF_PANICWARN;
597 kprintf("Warning: thread switch from interrupt, IPI, "
598 "or hard code section.\n"
599 "thread %p (%s)\n", td, td->td_comm);
603 gd->gd_intr_nesting_level = savegdnest;
604 gd->gd_trap_nesting_level = savegdtrap;
610 * Release our current user process designation if we are blocking
611 * or if a user reschedule was requested.
613 * NOTE: This function is NOT called if we are switching into or
614 * returning from a preemption.
616 * NOTE: Releasing our current user process designation may cause
617 * it to be assigned to another thread, which in turn will
618 * cause us to block in the usched acquire code when we attempt
619 * to return to userland.
621 * NOTE: On SMP systems this can be very nasty when heavy token
622 * contention is present so we want to be careful not to
623 * release the designation gratuitously.
625 if (td->td_release &&
626 (user_resched_wanted() || (td->td_flags & TDF_RUNQ) == 0)) {
631 * Release all tokens. Once we do this we must remain in the critical
632 * section and cannot run IPIs or other interrupts until we switch away
633 * because they may implode if they try to get a token using our thread
637 if (TD_TOKS_HELD(td))
638 lwkt_relalltokens(td);
641 * We had better not be holding any spin locks, but don't get into an
642 * endless panic loop.
644 KASSERT(gd->gd_spinlocks == 0 || panicstr != NULL,
645 ("lwkt_switch: still holding %d exclusive spinlocks!",
649 if (td->td_cscount) {
650 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
652 if (panic_on_cscount)
653 panic("switching while mastering cpusync");
658 * If we had preempted another thread on this cpu, resume the preempted
659 * thread. This occurs transparently, whether the preempted thread
660 * was scheduled or not (it may have been preempted after descheduling
663 * We have to setup the MP lock for the original thread after backing
664 * out the adjustment that was made to curthread when the original
667 if ((ntd = td->td_preempted) != NULL) {
668 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
669 ntd->td_flags |= TDF_PREEMPT_DONE;
670 ntd->td_contended = 0; /* reset contended */
673 * The interrupt may have woken a thread up, we need to properly
674 * set the reschedule flag if the originally interrupted thread is
675 * at a lower priority.
677 * NOTE: The interrupt may not have descheduled ntd.
679 * NOTE: We do not reschedule if there are no threads on the runq.
680 * (ntd could be the idlethread).
682 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
683 if (xtd && xtd != ntd)
685 goto havethread_preempted;
689 * Figure out switch target. If we cannot switch to our desired target
690 * look for a thread that we can switch to.
692 * NOTE! The limited spin loop and related parameters are extremely
693 * important for system performance, particularly for pipes and
694 * concurrent conflicting VM faults.
696 clear_lwkt_resched();
697 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
701 if (TD_TOKS_NOT_HELD(ntd) ||
702 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops)))
706 ++ntd->td_contended; /* overflow ok */
707 if (gd->gd_indefinite.type == 0)
708 indefinite_init(&gd->gd_indefinite, NULL, 0, 't');
710 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
711 kprintf("lwkt_switch: excessive contended %d "
712 "thread %p\n", ntd->td_contended, ntd);
716 } while (ntd->td_contended < (lwkt_spin_loops >> 1));
720 * Bleh, the thread we wanted to switch to has a contended token.
721 * See if we can switch to another thread.
723 * We generally don't want to do this because it represents a
724 * priority inversion. Do not allow the case if the thread
725 * is returning to userland (not a kernel thread) AND the thread
728 while ((ntd = TAILQ_NEXT(ntd, td_threadq)) != NULL) {
729 if (ntd->td_pri < TDPRI_KERN_LPSCHED && upri > ntd->td_upri)
736 if (TD_TOKS_NOT_HELD(ntd) ||
737 lwkt_getalltokens(ntd, (ntd->td_contended > lwkt_spin_loops))) {
740 ++ntd->td_contended; /* overflow ok */
744 * Fall through, switch to idle thread to get us out of the current
745 * context. Since we were contended, prevent HLT by flagging a
752 * We either contended on ntd or the runq is empty. We must switch
753 * through the idle thread to get out of the current context.
755 ntd = &gd->gd_idlethread;
756 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
757 ASSERT_NO_TOKENS_HELD(ntd);
758 cpu_time.cp_msg[0] = 0;
763 * Clear gd_idle_repeat when doing a normal switch to a non-idle
766 ntd->td_wmesg = NULL;
767 ntd->td_contended = 0; /* reset once scheduled */
768 ++gd->gd_cnt.v_swtch;
769 gd->gd_idle_repeat = 0;
772 * If we were busy waiting record final disposition
774 if (gd->gd_indefinite.type)
775 indefinite_done(&gd->gd_indefinite);
777 havethread_preempted:
779 * If the new target does not need the MP lock and we are holding it,
780 * release the MP lock. If the new target requires the MP lock we have
781 * already acquired it for the target.
785 KASSERT(ntd->td_critcount,
786 ("priority problem in lwkt_switch %d %d",
787 td->td_critcount, ntd->td_critcount));
791 * Execute the actual thread switch operation. This function
792 * returns to the current thread and returns the previous thread
793 * (which may be different from the thread we switched to).
795 * We are responsible for marking ntd as TDF_RUNNING.
797 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
799 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
800 ntd->td_flags |= TDF_RUNNING;
801 lwkt_switch_return(td->td_switch(ntd));
802 /* ntd invalid, td_switch() can return a different thread_t */
806 * catch-all. XXX is this strictly needed?
810 /* NOTE: current cpu may have changed after switch */
815 * Called by assembly in the td_switch (thread restore path) for thread
816 * bootstrap cases which do not 'return' to lwkt_switch().
819 lwkt_switch_return(thread_t otd)
823 uint64_t tsc_base = rdtsc();
827 exiting = otd->td_flags & TDF_EXITING;
831 * Check if otd was migrating. Now that we are on ntd we can finish
832 * up the migration. This is a bit messy but it is the only place
833 * where td is known to be fully descheduled.
835 * We can only activate the migration if otd was migrating but not
836 * held on the cpu due to a preemption chain. We still have to
837 * clear TDF_RUNNING on the old thread either way.
839 * We are responsible for clearing the previously running thread's
842 if ((rgd = otd->td_migrate_gd) != NULL &&
843 (otd->td_flags & TDF_PREEMPT_LOCK) == 0) {
844 KKASSERT((otd->td_flags & (TDF_MIGRATING | TDF_RUNNING)) ==
845 (TDF_MIGRATING | TDF_RUNNING));
846 otd->td_migrate_gd = NULL;
847 otd->td_flags &= ~TDF_RUNNING;
848 lwkt_send_ipiq(rgd, lwkt_setcpu_remote, otd);
850 otd->td_flags &= ~TDF_RUNNING;
854 * Final exit validations (see lwp_wait()). Note that otd becomes
855 * invalid the *instant* we set TDF_MP_EXITSIG.
857 * Use the EXITING status loaded from before we clear TDF_RUNNING,
858 * because if it is not set otd becomes invalid the instant we clear
859 * TDF_RUNNING on it (otherwise, if the system is fast enough, we
860 * might 'steal' TDF_EXITING from another switch-return!).
865 mpflags = otd->td_mpflags;
868 if (mpflags & TDF_MP_EXITWAIT) {
869 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
870 mpflags | TDF_MP_EXITSIG)) {
875 if (atomic_cmpset_int(&otd->td_mpflags, mpflags,
876 mpflags | TDF_MP_EXITSIG)) {
883 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
884 kprintf("lwkt_switch_return: excessive TDF_EXITING "
893 * Request that the target thread preempt the current thread. Preemption
894 * can only occur only:
896 * - If our critical section is the one that we were called with
897 * - The relative priority of the target thread is higher
898 * - The target is not excessively interrupt-nested via td_nest_count
899 * - The target thread holds no tokens.
900 * - The target thread is not already scheduled and belongs to the
902 * - The current thread is not holding any spin-locks.
904 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
905 * this is called via lwkt_schedule() through the td_preemptable callback.
906 * critcount is the managed critical priority that we should ignore in order
907 * to determine whether preemption is possible (aka usually just the crit
908 * priority of lwkt_schedule() itself).
910 * Preemption is typically limited to interrupt threads.
912 * Operation works in a fairly straight-forward manner. The normal
913 * scheduling code is bypassed and we switch directly to the target
914 * thread. When the target thread attempts to block or switch away
915 * code at the base of lwkt_switch() will switch directly back to our
916 * thread. Our thread is able to retain whatever tokens it holds and
917 * if the target needs one of them the target will switch back to us
918 * and reschedule itself normally.
921 lwkt_preempt(thread_t ntd, int critcount)
923 struct globaldata *gd = mycpu;
926 int save_gd_intr_nesting_level;
929 * The caller has put us in a critical section. We can only preempt
930 * if the caller of the caller was not in a critical section (basically
931 * a local interrupt), as determined by the 'critcount' parameter. We
932 * also can't preempt if the caller is holding any spinlocks (even if
933 * he isn't in a critical section). This also handles the tokens test.
935 * YYY The target thread must be in a critical section (else it must
936 * inherit our critical section? I dunno yet).
938 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
940 td = gd->gd_curthread;
941 if (preempt_enable == 0) {
945 if (ntd->td_pri <= td->td_pri) {
949 if (td->td_critcount > critcount) {
953 if (td->td_nest_count >= 2) {
957 if (td->td_cscount) {
961 if (ntd->td_gd != gd) {
967 * We don't have to check spinlocks here as they will also bump
970 * Do not try to preempt if the target thread is holding any tokens.
971 * We could try to acquire the tokens but this case is so rare there
972 * is no need to support it.
974 KKASSERT(gd->gd_spinlocks == 0);
976 if (TD_TOKS_HELD(ntd)) {
980 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
984 if (ntd->td_preempted) {
988 KKASSERT(gd->gd_processing_ipiq == 0);
991 * Since we are able to preempt the current thread, there is no need to
992 * call need_lwkt_resched().
994 * We must temporarily clear gd_intr_nesting_level around the switch
995 * since switchouts from the target thread are allowed (they will just
996 * return to our thread), and since the target thread has its own stack.
998 * A preemption must switch back to the original thread, assert the
1002 ntd->td_preempted = td;
1003 td->td_flags |= TDF_PREEMPT_LOCK;
1004 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
1005 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1006 gd->gd_intr_nesting_level = 0;
1008 KKASSERT((ntd->td_flags & TDF_RUNNING) == 0);
1009 ntd->td_flags |= TDF_RUNNING;
1010 xtd = td->td_switch(ntd);
1011 KKASSERT(xtd == ntd);
1012 lwkt_switch_return(xtd);
1013 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
1015 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1016 ntd->td_preempted = NULL;
1017 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
1021 * Conditionally call splz() if gd_reqflags indicates work is pending.
1022 * This will work inside a critical section but not inside a hard code
1025 * (self contained on a per cpu basis)
1030 globaldata_t gd = mycpu;
1031 thread_t td = gd->gd_curthread;
1033 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1034 gd->gd_intr_nesting_level == 0 &&
1035 td->td_nest_count < 2)
1042 * This version is integrated into crit_exit, reqflags has already
1043 * been tested but td_critcount has not.
1045 * We only want to execute the splz() on the 1->0 transition of
1046 * critcount and not in a hard code section or if too deeply nested.
1048 * NOTE: gd->gd_spinlocks is implied to be 0 when td_critcount is 0.
1051 lwkt_maybe_splz(thread_t td)
1053 globaldata_t gd = td->td_gd;
1055 if (td->td_critcount == 0 &&
1056 gd->gd_intr_nesting_level == 0 &&
1057 td->td_nest_count < 2)
1064 * Drivers which set up processing co-threads can call this function to
1065 * run the co-thread at a higher priority and to allow it to preempt
1069 lwkt_set_interrupt_support_thread(void)
1071 thread_t td = curthread;
1073 lwkt_setpri_self(TDPRI_INT_SUPPORT);
1074 td->td_flags |= TDF_INTTHREAD;
1075 td->td_preemptable = lwkt_preempt;
1080 * This function is used to negotiate a passive release of the current
1081 * process/lwp designation with the user scheduler, allowing the user
1082 * scheduler to schedule another user thread. The related kernel thread
1083 * (curthread) continues running in the released state.
1086 lwkt_passive_release(struct thread *td)
1088 struct lwp *lp = td->td_lwp;
1090 td->td_release = NULL;
1091 lwkt_setpri_self(TDPRI_KERN_USER);
1093 lp->lwp_proc->p_usched->release_curproc(lp);
1098 * This implements a LWKT yield, allowing a kernel thread to yield to other
1099 * kernel threads at the same or higher priority. This function can be
1100 * called in a tight loop and will typically only yield once per tick.
1102 * Most kernel threads run at the same priority in order to allow equal
1105 * (self contained on a per cpu basis)
1110 globaldata_t gd = mycpu;
1111 thread_t td = gd->gd_curthread;
1114 * Should never be called with spinlocks held but there is a path
1115 * via ACPI where it might happen.
1117 if (gd->gd_spinlocks)
1121 * Safe to call splz if we are not too-heavily nested.
1123 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1127 * Caller allows switching
1129 if (lwkt_resched_wanted()) {
1130 lwkt_schedule_self(curthread);
1136 * The quick version processes pending interrupts and higher-priority
1137 * LWKT threads but will not round-robin same-priority LWKT threads.
1139 * When called while attempting to return to userland the only same-pri
1140 * threads are the ones which have already tried to become the current
1144 lwkt_yield_quick(void)
1146 globaldata_t gd = mycpu;
1147 thread_t td = gd->gd_curthread;
1149 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1151 if (lwkt_resched_wanted()) {
1153 if (TAILQ_FIRST(&gd->gd_tdrunq) == td) {
1154 clear_lwkt_resched();
1156 lwkt_schedule_self(curthread);
1164 * This yield is designed for kernel threads with a user context.
1166 * The kernel acting on behalf of the user is potentially cpu-bound,
1167 * this function will efficiently allow other threads to run and also
1168 * switch to other processes by releasing.
1170 * The lwkt_user_yield() function is designed to have very low overhead
1171 * if no yield is determined to be needed.
1174 lwkt_user_yield(void)
1176 globaldata_t gd = mycpu;
1177 thread_t td = gd->gd_curthread;
1180 * Should never be called with spinlocks held but there is a path
1181 * via ACPI where it might happen.
1183 if (gd->gd_spinlocks)
1187 * Always run any pending interrupts in case we are in a critical
1190 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1194 * Switch (which forces a release) if another kernel thread needs
1195 * the cpu, if userland wants us to resched, or if our kernel
1196 * quantum has run out.
1198 if (lwkt_resched_wanted() ||
1199 user_resched_wanted())
1206 * Reacquire the current process if we are released.
1208 * XXX not implemented atm. The kernel may be holding locks and such,
1209 * so we want the thread to continue to receive cpu.
1211 if (td->td_release == NULL && lp) {
1212 lp->lwp_proc->p_usched->acquire_curproc(lp);
1213 td->td_release = lwkt_passive_release;
1214 lwkt_setpri_self(TDPRI_USER_NORM);
1220 * Generic schedule. Possibly schedule threads belonging to other cpus and
1221 * deal with threads that might be blocked on a wait queue.
1223 * We have a little helper inline function which does additional work after
1224 * the thread has been enqueued, including dealing with preemption and
1225 * setting need_lwkt_resched() (which prevents the kernel from returning
1226 * to userland until it has processed higher priority threads).
1228 * It is possible for this routine to be called after a failed _enqueue
1229 * (due to the target thread migrating, sleeping, or otherwise blocked).
1230 * We have to check that the thread is actually on the run queue!
1234 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount)
1236 if (ntd->td_flags & TDF_RUNQ) {
1237 if (ntd->td_preemptable) {
1238 ntd->td_preemptable(ntd, ccount); /* YYY +token */
1245 _lwkt_schedule(thread_t td)
1247 globaldata_t mygd = mycpu;
1249 KASSERT(td != &td->td_gd->gd_idlethread,
1250 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
1251 KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
1252 crit_enter_gd(mygd);
1253 KKASSERT(td->td_lwp == NULL ||
1254 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1256 if (td == mygd->gd_curthread) {
1260 * If we own the thread, there is no race (since we are in a
1261 * critical section). If we do not own the thread there might
1262 * be a race but the target cpu will deal with it.
1264 if (td->td_gd == mygd) {
1266 _lwkt_schedule_post(mygd, td, 1);
1268 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
1275 lwkt_schedule(thread_t td)
1281 lwkt_schedule_noresched(thread_t td) /* XXX not impl */
1287 * When scheduled remotely if frame != NULL the IPIQ is being
1288 * run via doreti or an interrupt then preemption can be allowed.
1290 * To allow preemption we have to drop the critical section so only
1291 * one is present in _lwkt_schedule_post.
1294 lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1296 thread_t td = curthread;
1299 if (frame && ntd->td_preemptable) {
1300 crit_exit_noyield(td);
1301 _lwkt_schedule(ntd);
1302 crit_enter_quick(td);
1304 _lwkt_schedule(ntd);
1309 * Thread migration using a 'Pull' method. The thread may or may not be
1310 * the current thread. It MUST be descheduled and in a stable state.
1311 * lwkt_giveaway() must be called on the cpu owning the thread.
1313 * At any point after lwkt_giveaway() is called, the target cpu may
1314 * 'pull' the thread by calling lwkt_acquire().
1316 * We have to make sure the thread is not sitting on a per-cpu tsleep
1317 * queue or it will blow up when it moves to another cpu.
1319 * MPSAFE - must be called under very specific conditions.
1322 lwkt_giveaway(thread_t td)
1324 globaldata_t gd = mycpu;
1327 if (td->td_flags & TDF_TSLEEPQ)
1329 KKASSERT(td->td_gd == gd);
1330 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1331 td->td_flags |= TDF_MIGRATING;
1336 lwkt_acquire(thread_t td)
1341 KKASSERT(td->td_flags & TDF_MIGRATING);
1346 uint64_t tsc_base = rdtsc();
1349 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
1350 crit_enter_gd(mygd);
1351 DEBUG_PUSH_INFO("lwkt_acquire");
1352 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1353 lwkt_process_ipiq();
1355 #ifdef _KERNEL_VIRTUAL
1359 if (tsc_frequency && rdtsc() - tsc_base > tsc_frequency) {
1360 kprintf("lwkt_acquire: stuck td %p td->td_flags %08x\n",
1369 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1370 td->td_flags &= ~TDF_MIGRATING;
1373 crit_enter_gd(mygd);
1374 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1375 td->td_flags &= ~TDF_MIGRATING;
1381 * Generic deschedule. Descheduling threads other then your own should be
1382 * done only in carefully controlled circumstances. Descheduling is
1385 * This function may block if the cpu has run out of messages.
1388 lwkt_deschedule(thread_t td)
1391 if (td == curthread) {
1394 if (td->td_gd == mycpu) {
1397 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
1404 * Set the target thread's priority. This routine does not automatically
1405 * switch to a higher priority thread, LWKT threads are not designed for
1406 * continuous priority changes. Yield if you want to switch.
1409 lwkt_setpri(thread_t td, int pri)
1411 if (td->td_pri != pri) {
1414 if (td->td_flags & TDF_RUNQ) {
1415 KKASSERT(td->td_gd == mycpu);
1427 * Set the initial priority for a thread prior to it being scheduled for
1428 * the first time. The thread MUST NOT be scheduled before or during
1429 * this call. The thread may be assigned to a cpu other then the current
1432 * Typically used after a thread has been created with TDF_STOPPREQ,
1433 * and before the thread is initially scheduled.
1436 lwkt_setpri_initial(thread_t td, int pri)
1439 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
1444 lwkt_setpri_self(int pri)
1446 thread_t td = curthread;
1448 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1450 if (td->td_flags & TDF_RUNQ) {
1461 * hz tick scheduler clock for LWKT threads
1464 lwkt_schedulerclock(thread_t td)
1466 globaldata_t gd = td->td_gd;
1469 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
1472 * If the current thread is at the head of the runq shift it to the
1473 * end of any equal-priority threads and request a LWKT reschedule
1476 * Ignore upri in this situation. There will only be one user thread
1477 * in user mode, all others will be user threads running in kernel
1478 * mode and we have to make sure they get some cpu.
1480 xtd = TAILQ_NEXT(td, td_threadq);
1481 if (xtd && xtd->td_pri == td->td_pri) {
1482 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
1483 while (xtd && xtd->td_pri == td->td_pri)
1484 xtd = TAILQ_NEXT(xtd, td_threadq);
1486 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
1488 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
1489 need_lwkt_resched();
1493 * If we scheduled a thread other than the one at the head of the
1494 * queue always request a reschedule every tick.
1496 need_lwkt_resched();
1498 /* else curthread probably the idle thread, no need to reschedule */
1502 * Migrate the current thread to the specified cpu.
1504 * This is accomplished by descheduling ourselves from the current cpu
1505 * and setting td_migrate_gd. The lwkt_switch() code will detect that the
1506 * 'old' thread wants to migrate after it has been completely switched out
1507 * and will complete the migration.
1509 * TDF_MIGRATING prevents scheduling races while the thread is being migrated.
1511 * We must be sure to release our current process designation (if a user
1512 * process) before clearing out any tsleepq we are on because the release
1513 * code may re-add us.
1515 * We must be sure to remove ourselves from the current cpu's tsleepq
1516 * before potentially moving to another queue. The thread can be on
1517 * a tsleepq due to a left-over tsleep_interlock().
1521 lwkt_setcpu_self(globaldata_t rgd)
1523 thread_t td = curthread;
1525 if (td->td_gd != rgd) {
1526 crit_enter_quick(td);
1530 if (td->td_flags & TDF_TSLEEPQ)
1534 * Set TDF_MIGRATING to prevent a spurious reschedule while we are
1535 * trying to deschedule ourselves and switch away, then deschedule
1536 * ourself, remove us from tdallq, and set td_migrate_gd. Finally,
1537 * call lwkt_switch() to complete the operation.
1539 td->td_flags |= TDF_MIGRATING;
1540 lwkt_deschedule_self(td);
1541 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1542 td->td_migrate_gd = rgd;
1546 * We are now on the target cpu
1548 KKASSERT(rgd == mycpu);
1549 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
1550 crit_exit_quick(td);
1555 lwkt_migratecpu(int cpuid)
1559 rgd = globaldata_find(cpuid);
1560 lwkt_setcpu_self(rgd);
1564 * Remote IPI for cpu migration (called while in a critical section so we
1565 * do not have to enter another one).
1567 * The thread (td) has already been completely descheduled from the
1568 * originating cpu and we can simply assert the case. The thread is
1569 * assigned to the new cpu and enqueued.
1571 * The thread will re-add itself to tdallq when it resumes execution.
1574 lwkt_setcpu_remote(void *arg)
1577 globaldata_t gd = mycpu;
1579 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1582 td->td_flags &= ~TDF_MIGRATING;
1583 KKASSERT(td->td_migrate_gd == NULL);
1584 KKASSERT(td->td_lwp == NULL ||
1585 (td->td_lwp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1590 lwkt_preempted_proc(void)
1592 thread_t td = curthread;
1593 while (td->td_preempted)
1594 td = td->td_preempted;
1599 * Create a kernel process/thread/whatever. It shares it's address space
1600 * with proc0 - ie: kernel only.
1602 * If the cpu is not specified one will be selected. In the future
1603 * specifying a cpu of -1 will enable kernel thread migration between
1607 lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1608 thread_t template, int tdflags, int cpu, const char *fmt, ...)
1613 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
1617 cpu_set_thread_handler(td, lwkt_exit, func, arg);
1620 * Set up arg0 for 'ps' etc
1622 __va_start(ap, fmt);
1623 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
1627 * Schedule the thread to run
1629 if (td->td_flags & TDF_NOSTART)
1630 td->td_flags &= ~TDF_NOSTART;
1637 * Destroy an LWKT thread. Warning! This function is not called when
1638 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1639 * uses a different reaping mechanism.
1644 thread_t td = curthread;
1649 * Do any cleanup that might block here
1651 if (td->td_flags & TDF_VERBOSE)
1652 kprintf("kthread %p %s has exited\n", td, td->td_comm);
1654 dsched_exit_thread(td);
1657 * Get us into a critical section to interlock gd_freetd and loop
1658 * until we can get it freed.
1660 * We have to cache the current td in gd_freetd because objcache_put()ing
1661 * it would rip it out from under us while our thread is still active.
1663 * We are the current thread so of course our own TDF_RUNNING bit will
1664 * be set, so unlike the lwp reap code we don't wait for it to clear.
1667 crit_enter_quick(td);
1670 tsleep(td, 0, "tdreap", 1);
1673 if ((std = gd->gd_freetd) != NULL) {
1674 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1675 gd->gd_freetd = NULL;
1676 objcache_put(thread_cache, std);
1683 * Remove thread resources from kernel lists and deschedule us for
1684 * the last time. We cannot block after this point or we may end
1685 * up with a stale td on the tsleepq.
1687 * None of this may block, the critical section is the only thing
1688 * protecting tdallq and the only thing preventing new lwkt_hold()
1691 if (td->td_flags & TDF_TSLEEPQ)
1693 lwkt_deschedule_self(td);
1694 lwkt_remove_tdallq(td);
1695 KKASSERT(td->td_refs == 0);
1700 KKASSERT(gd->gd_freetd == NULL);
1701 if (td->td_flags & TDF_ALLOCATED_THREAD)
1707 lwkt_remove_tdallq(thread_t td)
1709 KKASSERT(td->td_gd == mycpu);
1710 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1714 * Code reduction and branch prediction improvements. Call/return
1715 * overhead on modern cpus often degenerates into 0 cycles due to
1716 * the cpu's branch prediction hardware and return pc cache. We
1717 * can take advantage of this by not inlining medium-complexity
1718 * functions and we can also reduce the branch prediction impact
1719 * by collapsing perfectly predictable branches into a single
1720 * procedure instead of duplicating it.
1722 * Is any of this noticeable? Probably not, so I'll take the
1723 * smaller code size.
1726 crit_exit_wrapper(__DEBUG_CRIT_ARG__)
1728 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
1734 thread_t td = curthread;
1735 int lcrit = td->td_critcount;
1737 td->td_critcount = 0;
1739 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
1744 * Called from debugger/panic on cpus which have been stopped. We must still
1745 * process the IPIQ while stopped.
1747 * If we are dumping also try to process any pending interrupts. This may
1748 * or may not work depending on the state of the cpu at the point it was
1752 lwkt_smp_stopped(void)
1754 globaldata_t gd = mycpu;
1757 lwkt_process_ipiq();
1758 --gd->gd_intr_nesting_level;
1760 ++gd->gd_intr_nesting_level;
1762 lwkt_process_ipiq();