2 * Copyright (c) 2003-2010 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>
54 #include <sys/spinlock.h>
57 #include <sys/thread2.h>
58 #include <sys/spinlock2.h>
59 #include <sys/mplock2.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>
75 #if !defined(KTR_CTXSW)
76 #define KTR_CTXSW KTR_ALL
78 KTR_INFO_MASTER(ctxsw);
79 KTR_INFO(KTR_CTXSW, ctxsw, sw, 0, "#cpu[%d].td = %p",
80 sizeof(int) + sizeof(struct thread *));
81 KTR_INFO(KTR_CTXSW, ctxsw, pre, 1, "#cpu[%d].td = %p",
82 sizeof(int) + sizeof(struct thread *));
83 KTR_INFO(KTR_CTXSW, ctxsw, newtd, 2, "#threads[%p].name = %s",
84 sizeof (struct thread *) + sizeof(char *));
85 KTR_INFO(KTR_CTXSW, ctxsw, deadtd, 3, "#threads[%p].name = <dead>", sizeof (struct thread *));
87 static MALLOC_DEFINE(M_THREAD, "thread", "lwkt threads");
90 static int panic_on_cscount = 0;
92 static __int64_t switch_count = 0;
93 static __int64_t preempt_hit = 0;
94 static __int64_t preempt_miss = 0;
95 static __int64_t preempt_weird = 0;
96 static __int64_t token_contention_count __debugvar = 0;
97 static int lwkt_use_spin_port;
98 static struct objcache *thread_cache;
101 static void lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame);
103 static void lwkt_fairq_accumulate(globaldata_t gd, thread_t td);
105 extern void cpu_heavy_restore(void);
106 extern void cpu_lwkt_restore(void);
107 extern void cpu_kthread_restore(void);
108 extern void cpu_idle_restore(void);
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.
114 TUNABLE_INT("lwkt.use_spin_port", &lwkt_use_spin_port);
117 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, "");
119 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
120 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0,
121 "Successful preemption events");
122 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0,
123 "Failed preemption events");
124 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
126 SYSCTL_QUAD(_lwkt, OID_AUTO, token_contention_count, CTLFLAG_RW,
127 &token_contention_count, 0, "spinning due to token contention");
129 static int fairq_enable = 1;
130 SYSCTL_INT(_lwkt, OID_AUTO, fairq_enable, CTLFLAG_RW, &fairq_enable, 0, "");
131 static int user_pri_sched = 0;
132 SYSCTL_INT(_lwkt, OID_AUTO, user_pri_sched, CTLFLAG_RW, &user_pri_sched, 0, "");
133 static int preempt_enable = 1;
134 SYSCTL_INT(_lwkt, OID_AUTO, preempt_enable, CTLFLAG_RW, &preempt_enable, 0, "");
138 * These helper procedures handle the runq, they can only be called from
139 * within a critical section.
141 * WARNING! Prior to SMP being brought up it is possible to enqueue and
142 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
143 * instead of 'mycpu' when referencing the globaldata structure. Once
144 * SMP live enqueuing and dequeueing only occurs on the current cpu.
148 _lwkt_dequeue(thread_t td)
150 if (td->td_flags & TDF_RUNQ) {
151 struct globaldata *gd = td->td_gd;
153 td->td_flags &= ~TDF_RUNQ;
154 TAILQ_REMOVE(&gd->gd_tdrunq, td, td_threadq);
155 gd->gd_fairq_total_pri -= td->td_pri;
156 if (TAILQ_FIRST(&gd->gd_tdrunq) == NULL)
157 atomic_clear_int_nonlocked(&gd->gd_reqflags, RQF_RUNNING);
164 * NOTE: There are a limited number of lwkt threads runnable since user
165 * processes only schedule one at a time per cpu.
169 _lwkt_enqueue(thread_t td)
173 if ((td->td_flags & (TDF_RUNQ|TDF_MIGRATING|TDF_BLOCKQ)) == 0) {
174 struct globaldata *gd = td->td_gd;
176 td->td_flags |= TDF_RUNQ;
177 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
179 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
180 atomic_set_int_nonlocked(&gd->gd_reqflags, RQF_RUNNING);
182 while (xtd && xtd->td_pri > td->td_pri)
183 xtd = TAILQ_NEXT(xtd, td_threadq);
185 TAILQ_INSERT_BEFORE(xtd, td, td_threadq);
187 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, td, td_threadq);
189 gd->gd_fairq_total_pri += td->td_pri;
194 _lwkt_thread_ctor(void *obj, void *privdata, int ocflags)
196 struct thread *td = (struct thread *)obj;
198 td->td_kstack = NULL;
199 td->td_kstack_size = 0;
200 td->td_flags = TDF_ALLOCATED_THREAD;
205 _lwkt_thread_dtor(void *obj, void *privdata)
207 struct thread *td = (struct thread *)obj;
209 KASSERT(td->td_flags & TDF_ALLOCATED_THREAD,
210 ("_lwkt_thread_dtor: not allocated from objcache"));
211 KASSERT((td->td_flags & TDF_ALLOCATED_STACK) && td->td_kstack &&
212 td->td_kstack_size > 0,
213 ("_lwkt_thread_dtor: corrupted stack"));
214 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
218 * Initialize the lwkt s/system.
223 /* An objcache has 2 magazines per CPU so divide cache size by 2. */
224 thread_cache = objcache_create_mbacked(M_THREAD, sizeof(struct thread),
225 NULL, CACHE_NTHREADS/2,
226 _lwkt_thread_ctor, _lwkt_thread_dtor, NULL);
230 * Schedule a thread to run. As the current thread we can always safely
231 * schedule ourselves, and a shortcut procedure is provided for that
234 * (non-blocking, self contained on a per cpu basis)
237 lwkt_schedule_self(thread_t td)
239 crit_enter_quick(td);
240 KASSERT(td != &td->td_gd->gd_idlethread,
241 ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
242 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
248 * Deschedule a thread.
250 * (non-blocking, self contained on a per cpu basis)
253 lwkt_deschedule_self(thread_t td)
255 crit_enter_quick(td);
261 * LWKTs operate on a per-cpu basis
263 * WARNING! Called from early boot, 'mycpu' may not work yet.
266 lwkt_gdinit(struct globaldata *gd)
268 TAILQ_INIT(&gd->gd_tdrunq);
269 TAILQ_INIT(&gd->gd_tdallq);
273 * Create a new thread. The thread must be associated with a process context
274 * or LWKT start address before it can be scheduled. If the target cpu is
275 * -1 the thread will be created on the current cpu.
277 * If you intend to create a thread without a process context this function
278 * does everything except load the startup and switcher function.
281 lwkt_alloc_thread(struct thread *td, int stksize, int cpu, int flags)
283 globaldata_t gd = mycpu;
287 * If static thread storage is not supplied allocate a thread. Reuse
288 * a cached free thread if possible. gd_freetd is used to keep an exiting
289 * thread intact through the exit.
293 if ((td = gd->gd_freetd) != NULL) {
294 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
296 gd->gd_freetd = NULL;
298 td = objcache_get(thread_cache, M_WAITOK);
299 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|
303 KASSERT((td->td_flags &
304 (TDF_ALLOCATED_THREAD|TDF_RUNNING)) == TDF_ALLOCATED_THREAD,
305 ("lwkt_alloc_thread: corrupted td flags 0x%X", td->td_flags));
306 flags |= td->td_flags & (TDF_ALLOCATED_THREAD|TDF_ALLOCATED_STACK);
310 * Try to reuse cached stack.
312 if ((stack = td->td_kstack) != NULL && td->td_kstack_size != stksize) {
313 if (flags & TDF_ALLOCATED_STACK) {
314 kmem_free(&kernel_map, (vm_offset_t)stack, td->td_kstack_size);
319 stack = (void *)kmem_alloc_stack(&kernel_map, stksize);
320 flags |= TDF_ALLOCATED_STACK;
323 lwkt_init_thread(td, stack, stksize, flags, gd);
325 lwkt_init_thread(td, stack, stksize, flags, globaldata_find(cpu));
330 * Initialize a preexisting thread structure. This function is used by
331 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
333 * All threads start out in a critical section at a priority of
334 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
335 * appropriate. This function may send an IPI message when the
336 * requested cpu is not the current cpu and consequently gd_tdallq may
337 * not be initialized synchronously from the point of view of the originating
340 * NOTE! we have to be careful in regards to creating threads for other cpus
341 * if SMP has not yet been activated.
346 lwkt_init_thread_remote(void *arg)
351 * Protected by critical section held by IPI dispatch
353 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
359 * lwkt core thread structural initialization.
361 * NOTE: All threads are initialized as mpsafe threads.
364 lwkt_init_thread(thread_t td, void *stack, int stksize, int flags,
365 struct globaldata *gd)
367 globaldata_t mygd = mycpu;
369 bzero(td, sizeof(struct thread));
370 td->td_kstack = stack;
371 td->td_kstack_size = stksize;
372 td->td_flags = flags;
374 td->td_pri = TDPRI_KERN_DAEMON;
375 td->td_critcount = 1;
376 td->td_toks_stop = &td->td_toks_base;
377 if (lwkt_use_spin_port)
378 lwkt_initport_spin(&td->td_msgport);
380 lwkt_initport_thread(&td->td_msgport, td);
381 pmap_init_thread(td);
384 * Normally initializing a thread for a remote cpu requires sending an
385 * IPI. However, the idlethread is setup before the other cpus are
386 * activated so we have to treat it as a special case. XXX manipulation
387 * of gd_tdallq requires the BGL.
389 if (gd == mygd || td == &gd->gd_idlethread) {
391 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
394 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
398 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
402 dsched_new_thread(td);
406 lwkt_set_comm(thread_t td, const char *ctl, ...)
411 kvsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
413 KTR_LOG(ctxsw_newtd, td, &td->td_comm[0]);
417 lwkt_hold(thread_t td)
423 lwkt_rele(thread_t td)
425 KKASSERT(td->td_refs > 0);
430 lwkt_wait_free(thread_t td)
433 tsleep(td, 0, "tdreap", hz);
437 lwkt_free_thread(thread_t td)
439 KKASSERT((td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK|TDF_RUNQ)) == 0);
440 if (td->td_flags & TDF_ALLOCATED_THREAD) {
441 objcache_put(thread_cache, td);
442 } else if (td->td_flags & TDF_ALLOCATED_STACK) {
443 /* client-allocated struct with internally allocated stack */
444 KASSERT(td->td_kstack && td->td_kstack_size > 0,
445 ("lwkt_free_thread: corrupted stack"));
446 kmem_free(&kernel_map, (vm_offset_t)td->td_kstack, td->td_kstack_size);
447 td->td_kstack = NULL;
448 td->td_kstack_size = 0;
450 KTR_LOG(ctxsw_deadtd, td);
455 * Switch to the next runnable lwkt. If no LWKTs are runnable then
456 * switch to the idlethread. Switching must occur within a critical
457 * section to avoid races with the scheduling queue.
459 * We always have full control over our cpu's run queue. Other cpus
460 * that wish to manipulate our queue must use the cpu_*msg() calls to
461 * talk to our cpu, so a critical section is all that is needed and
462 * the result is very, very fast thread switching.
464 * The LWKT scheduler uses a fixed priority model and round-robins at
465 * each priority level. User process scheduling is a totally
466 * different beast and LWKT priorities should not be confused with
467 * user process priorities.
469 * The MP lock may be out of sync with the thread's td_mpcount + td_xpcount.
470 * lwkt_switch() cleans it up.
472 * Note that the td_switch() function cannot do anything that requires
473 * the MP lock since the MP lock will have already been setup for
474 * the target thread (not the current thread). It's nice to have a scheduler
475 * that does not need the MP lock to work because it allows us to do some
476 * really cool high-performance MP lock optimizations.
478 * PREEMPTION NOTE: Preemption occurs via lwkt_preempt(). lwkt_switch()
479 * is not called by the current thread in the preemption case, only when
480 * the preempting thread blocks (in order to return to the original thread).
485 globaldata_t gd = mycpu;
486 thread_t td = gd->gd_curthread;
495 const char *lmsg; /* diagnostic - 'systat -pv 1' */
499 * Switching from within a 'fast' (non thread switched) interrupt or IPI
500 * is illegal. However, we may have to do it anyway if we hit a fatal
501 * kernel trap or we have paniced.
503 * If this case occurs save and restore the interrupt nesting level.
505 if (gd->gd_intr_nesting_level) {
509 if (gd->gd_trap_nesting_level == 0 && panic_cpu_gd != mycpu) {
510 panic("lwkt_switch: Attempt to switch from a "
511 "a fast interrupt, ipi, or hard code section, "
515 savegdnest = gd->gd_intr_nesting_level;
516 savegdtrap = gd->gd_trap_nesting_level;
517 gd->gd_intr_nesting_level = 0;
518 gd->gd_trap_nesting_level = 0;
519 if ((td->td_flags & TDF_PANICWARN) == 0) {
520 td->td_flags |= TDF_PANICWARN;
521 kprintf("Warning: thread switch from interrupt, IPI, "
522 "or hard code section.\n"
523 "thread %p (%s)\n", td, td->td_comm);
527 gd->gd_intr_nesting_level = savegdnest;
528 gd->gd_trap_nesting_level = savegdtrap;
534 * Passive release (used to transition from user to kernel mode
535 * when we block or switch rather then when we enter the kernel).
536 * This function is NOT called if we are switching into a preemption
537 * or returning from a preemption. Typically this causes us to lose
538 * our current process designation (if we have one) and become a true
539 * LWKT thread, and may also hand the current process designation to
540 * another process and schedule thread.
546 if (TD_TOKS_HELD(td))
547 lwkt_relalltokens(td);
550 * We had better not be holding any spin locks, but don't get into an
551 * endless panic loop.
553 KASSERT(gd->gd_spinlocks_wr == 0 || panicstr != NULL,
554 ("lwkt_switch: still holding %d exclusive spinlocks!",
555 gd->gd_spinlocks_wr));
560 * td_mpcount + td_xpcount cannot be used to determine if we currently
561 * hold the MP lock because get_mplock() will increment it prior to
562 * attempting to get the lock, and switch out if it can't. Our
563 * ownership of the actual lock will remain stable while we are
564 * in a critical section, and once we actually acquire the underlying
565 * lock as long as the count is greater than 0.
567 mpheld = MP_LOCK_HELD(gd);
569 if (td->td_cscount) {
570 kprintf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
572 if (panic_on_cscount)
573 panic("switching while mastering cpusync");
579 * If we had preempted another thread on this cpu, resume the preempted
580 * thread. This occurs transparently, whether the preempted thread
581 * was scheduled or not (it may have been preempted after descheduling
584 * We have to setup the MP lock for the original thread after backing
585 * out the adjustment that was made to curthread when the original
588 if ((ntd = td->td_preempted) != NULL) {
589 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
591 if (ntd->td_mpcount + ntd->td_xpcount && mpheld == 0) {
592 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d",
593 td, ntd, td->td_mpcount, ntd->td_mpcount + ntd->td_xpcount);
597 ntd->td_flags |= TDF_PREEMPT_DONE;
600 * The interrupt may have woken a thread up, we need to properly
601 * set the reschedule flag if the originally interrupted thread is
602 * at a lower priority.
604 if (TAILQ_FIRST(&gd->gd_tdrunq) &&
605 TAILQ_FIRST(&gd->gd_tdrunq)->td_pri > ntd->td_pri) {
608 /* YYY release mp lock on switchback if original doesn't need it */
609 goto havethread_preempted;
613 * Implement round-robin fairq with priority insertion. The priority
614 * insertion is handled by _lwkt_enqueue()
616 * We have to adjust the MP lock for the target thread. If we
617 * need the MP lock and cannot obtain it we try to locate a
618 * thread that does not need the MP lock. If we cannot, we spin
621 * A similar issue exists for the tokens held by the target thread.
622 * If we cannot obtain ownership of the tokens we cannot immediately
623 * schedule the thread.
626 clear_lwkt_resched();
628 ntd = TAILQ_FIRST(&gd->gd_tdrunq);
631 * Hotpath if we can get all necessary resources.
633 * If nothing is runnable switch to the idle thread
636 ntd = &gd->gd_idlethread;
637 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
638 ntd->td_flags |= TDF_IDLE_NOHLT;
640 KKASSERT(ntd->td_xpcount == 0);
641 if (ntd->td_mpcount) {
642 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
643 panic("Idle thread %p was holding the BGL!", ntd);
645 set_cpu_contention_mask(gd);
646 handle_cpu_contention_mask();
648 mpheld = MP_LOCK_HELD(gd);
653 clr_cpu_contention_mask(gd);
655 cpu_time.cp_msg[0] = 0;
656 cpu_time.cp_stallpc = 0;
663 * NOTE: For UP there is no mplock and lwkt_getalltokens()
666 if (ntd->td_fairq_accum >= 0 &&
668 (ntd->td_mpcount + ntd->td_xpcount == 0 ||
669 mpheld || cpu_try_mplock()) &&
671 (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd, &lmsg, &laddr))
674 clr_cpu_contention_mask(gd);
683 if (ntd->td_fairq_accum >= 0)
684 set_cpu_contention_mask(gd);
685 /* Reload mpheld (it become stale after mplock/token ops) */
686 mpheld = MP_LOCK_HELD(gd);
687 if (ntd->td_mpcount + ntd->td_xpcount && mpheld == 0) {
689 laddr = ntd->td_mplock_stallpc;
694 * Coldpath - unable to schedule ntd, continue looking for threads
695 * to schedule. This is only allowed of the (presumably) kernel
696 * thread exhausted its fair share. A kernel thread stuck on
697 * resources does not currently allow a user thread to get in
701 nquserok = ((ntd->td_pri < TDPRI_KERN_LPSCHED) ||
702 (ntd->td_fairq_accum < 0));
710 * If the fair-share scheduler ran out ntd gets moved to the
711 * end and its accumulator will be bumped, if it didn't we
712 * maintain the same queue position.
714 * nlast keeps track of the last element prior to any moves.
716 if (ntd->td_fairq_accum < 0) {
717 lwkt_fairq_accumulate(gd, ntd);
723 xtd = TAILQ_NEXT(ntd, td_threadq);
724 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq);
725 TAILQ_INSERT_TAIL(&gd->gd_tdrunq, ntd, td_threadq);
728 * Set terminal element (nlast)
737 ntd = TAILQ_NEXT(ntd, td_threadq);
741 * If we exhausted the run list switch to the idle thread.
742 * Since one or more threads had resource acquisition issues
743 * we do not allow the idle thread to halt.
745 * NOTE: nlast can be NULL.
749 ntd = &gd->gd_idlethread;
750 ntd->td_flags |= TDF_IDLE_NOHLT;
752 KKASSERT(ntd->td_xpcount == 0);
753 if (ntd->td_mpcount) {
754 mpheld = MP_LOCK_HELD(gd);
755 if (gd->gd_trap_nesting_level == 0 && panicstr == NULL)
756 panic("Idle thread %p was holding the BGL!", ntd);
758 set_cpu_contention_mask(gd);
759 handle_cpu_contention_mask();
761 mpheld = MP_LOCK_HELD(gd);
763 break; /* try again from the top, almost */
769 * If fairq accumulations occured we do not schedule the
770 * idle thread. This will cause us to try again from
774 break; /* try again from the top, almost */
776 strlcpy(cpu_time.cp_msg, lmsg, sizeof(cpu_time.cp_msg));
777 cpu_time.cp_stallpc = (uintptr_t)laddr;
782 * Try to switch to this thread.
784 * NOTE: For UP there is no mplock and lwkt_getalltokens()
787 if ((ntd->td_pri >= TDPRI_KERN_LPSCHED || nquserok ||
788 user_pri_sched) && ntd->td_fairq_accum >= 0 &&
790 (ntd->td_mpcount + ntd->td_xpcount == 0 ||
791 mpheld || cpu_try_mplock()) &&
793 (!TD_TOKS_HELD(ntd) || lwkt_getalltokens(ntd, &lmsg, &laddr))
796 clr_cpu_contention_mask(gd);
801 if (ntd->td_fairq_accum >= 0)
802 set_cpu_contention_mask(gd);
804 * Reload mpheld (it become stale after mplock/token ops).
806 mpheld = MP_LOCK_HELD(gd);
807 if (ntd->td_mpcount + ntd->td_xpcount && mpheld == 0) {
809 laddr = ntd->td_mplock_stallpc;
811 if (ntd->td_pri >= TDPRI_KERN_LPSCHED && ntd->td_fairq_accum >= 0)
817 * All threads exhausted but we can loop due to a negative
820 * While we are looping in the scheduler be sure to service
821 * any interrupts which were made pending due to our critical
822 * section, otherwise we could livelock (e.g.) IPIs.
824 * NOTE: splz can enter and exit the mplock so mpheld is
825 * stale after this call.
831 * Our mplock can be cached and cause other cpus to livelock
832 * if we loop due to e.g. not being able to acquire tokens.
834 if (MP_LOCK_HELD(gd))
835 cpu_rel_mplock(gd->gd_cpuid);
841 * Do the actual switch. WARNING: mpheld is stale here.
843 * We must always decrement td_fairq_accum on non-idle threads just
844 * in case a thread never gets a tick due to being in a continuous
845 * critical section. The page-zeroing code does that.
847 * If the thread we came up with is a higher or equal priority verses
848 * the thread at the head of the queue we move our thread to the
849 * front. This way we can always check the front of the queue.
852 ++gd->gd_cnt.v_swtch;
853 --ntd->td_fairq_accum;
854 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
855 if (ntd != xtd && ntd->td_pri >= xtd->td_pri) {
856 TAILQ_REMOVE(&gd->gd_tdrunq, ntd, td_threadq);
857 TAILQ_INSERT_HEAD(&gd->gd_tdrunq, ntd, td_threadq);
859 havethread_preempted:
862 * If the new target does not need the MP lock and we are holding it,
863 * release the MP lock. If the new target requires the MP lock we have
864 * already acquired it for the target.
866 * WARNING: mpheld is stale here.
869 KASSERT(ntd->td_critcount,
870 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
872 if (ntd->td_mpcount + ntd->td_xpcount == 0 ) {
873 if (MP_LOCK_HELD(gd))
874 cpu_rel_mplock(gd->gd_cpuid);
876 ASSERT_MP_LOCK_HELD(ntd);
881 KTR_LOG(ctxsw_sw, gd->gd_cpuid, ntd);
884 /* NOTE: current cpu may have changed after switch */
889 * Request that the target thread preempt the current thread. Preemption
890 * only works under a specific set of conditions:
892 * - We are not preempting ourselves
893 * - The target thread is owned by the current cpu
894 * - We are not currently being preempted
895 * - The target is not currently being preempted
896 * - We are not holding any spin locks
897 * - The target thread is not holding any tokens
898 * - We are able to satisfy the target's MP lock requirements (if any).
900 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
901 * this is called via lwkt_schedule() through the td_preemptable callback.
902 * critcount is the managed critical priority that we should ignore in order
903 * to determine whether preemption is possible (aka usually just the crit
904 * priority of lwkt_schedule() itself).
906 * XXX at the moment we run the target thread in a critical section during
907 * the preemption in order to prevent the target from taking interrupts
908 * that *WE* can't. Preemption is strictly limited to interrupt threads
909 * and interrupt-like threads, outside of a critical section, and the
910 * preempted source thread will be resumed the instant the target blocks
911 * whether or not the source is scheduled (i.e. preemption is supposed to
912 * be as transparent as possible).
914 * The target thread inherits our MP count (added to its own) for the
915 * duration of the preemption in order to preserve the atomicy of the
916 * MP lock during the preemption. Therefore, any preempting targets must be
917 * careful in regards to MP assertions. Note that the MP count may be
918 * out of sync with the physical mp_lock, but we do not have to preserve
919 * the original ownership of the lock if it was out of synch (that is, we
920 * can leave it synchronized on return).
923 lwkt_preempt(thread_t ntd, int critcount)
925 struct globaldata *gd = mycpu;
931 int save_gd_intr_nesting_level;
934 * The caller has put us in a critical section. We can only preempt
935 * if the caller of the caller was not in a critical section (basically
936 * a local interrupt), as determined by the 'critcount' parameter. We
937 * also can't preempt if the caller is holding any spinlocks (even if
938 * he isn't in a critical section). This also handles the tokens test.
940 * YYY The target thread must be in a critical section (else it must
941 * inherit our critical section? I dunno yet).
943 * Set need_lwkt_resched() unconditionally for now YYY.
945 KASSERT(ntd->td_critcount, ("BADCRIT0 %d", ntd->td_pri));
947 if (preempt_enable == 0) {
952 td = gd->gd_curthread;
953 if (ntd->td_pri <= td->td_pri) {
957 if (td->td_critcount > critcount) {
963 if (ntd->td_gd != gd) {
970 * We don't have to check spinlocks here as they will also bump
973 * Do not try to preempt if the target thread is holding any tokens.
974 * We could try to acquire the tokens but this case is so rare there
975 * is no need to support it.
977 KKASSERT(gd->gd_spinlocks_wr == 0);
979 if (TD_TOKS_HELD(ntd)) {
984 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
989 if (ntd->td_preempted) {
996 * NOTE: An interrupt might have occured just as we were transitioning
997 * to or from the MP lock. In this case td_mpcount will be pre-disposed
998 * (non-zero) but not actually synchronized with the mp_lock itself.
999 * We can use it to imply an MP lock requirement for the preemption but
1000 * we cannot use it to test whether we hold the MP lock or not.
1002 savecnt = td->td_mpcount;
1003 mpheld = MP_LOCK_HELD(gd);
1004 ntd->td_xpcount = td->td_mpcount + td->td_xpcount;
1005 if (mpheld == 0 && ntd->td_mpcount + ntd->td_xpcount && !cpu_try_mplock()) {
1006 ntd->td_xpcount = 0;
1008 need_lwkt_resched();
1014 * Since we are able to preempt the current thread, there is no need to
1015 * call need_lwkt_resched().
1017 * We must temporarily clear gd_intr_nesting_level around the switch
1018 * since switchouts from the target thread are allowed (they will just
1019 * return to our thread), and since the target thread has its own stack.
1022 ntd->td_preempted = td;
1023 td->td_flags |= TDF_PREEMPT_LOCK;
1024 KTR_LOG(ctxsw_pre, gd->gd_cpuid, ntd);
1025 save_gd_intr_nesting_level = gd->gd_intr_nesting_level;
1026 gd->gd_intr_nesting_level = 0;
1028 gd->gd_intr_nesting_level = save_gd_intr_nesting_level;
1030 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
1032 KKASSERT(savecnt == td->td_mpcount);
1033 mpheld = MP_LOCK_HELD(gd);
1034 if (mpheld && td->td_mpcount == 0)
1035 cpu_rel_mplock(gd->gd_cpuid);
1036 else if (mpheld == 0 && td->td_mpcount + td->td_xpcount)
1037 panic("lwkt_preempt(): MP lock was not held through");
1039 ntd->td_preempted = NULL;
1040 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
1044 * Conditionally call splz() if gd_reqflags indicates work is pending.
1045 * This will work inside a critical section but not inside a hard code
1048 * (self contained on a per cpu basis)
1053 globaldata_t gd = mycpu;
1054 thread_t td = gd->gd_curthread;
1056 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) &&
1057 gd->gd_intr_nesting_level == 0 &&
1058 td->td_nest_count < 2)
1065 * This version is integrated into crit_exit, reqflags has already
1066 * been tested but td_critcount has not.
1068 * We only want to execute the splz() on the 1->0 transition of
1069 * critcount and not in a hard code section or if too deeply nested.
1072 lwkt_maybe_splz(thread_t td)
1074 globaldata_t gd = td->td_gd;
1076 if (td->td_critcount == 0 &&
1077 gd->gd_intr_nesting_level == 0 &&
1078 td->td_nest_count < 2)
1085 * This function is used to negotiate a passive release of the current
1086 * process/lwp designation with the user scheduler, allowing the user
1087 * scheduler to schedule another user thread. The related kernel thread
1088 * (curthread) continues running in the released state.
1091 lwkt_passive_release(struct thread *td)
1093 struct lwp *lp = td->td_lwp;
1095 td->td_release = NULL;
1096 lwkt_setpri_self(TDPRI_KERN_USER);
1097 lp->lwp_proc->p_usched->release_curproc(lp);
1102 * This implements a normal yield. This routine is virtually a nop if
1103 * there is nothing to yield to but it will always run any pending interrupts
1104 * if called from a critical section.
1106 * This yield is designed for kernel threads without a user context.
1108 * (self contained on a per cpu basis)
1113 globaldata_t gd = mycpu;
1114 thread_t td = gd->gd_curthread;
1117 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1119 if (td->td_fairq_accum < 0) {
1120 lwkt_schedule_self(curthread);
1123 xtd = TAILQ_FIRST(&gd->gd_tdrunq);
1124 if (xtd && xtd->td_pri > td->td_pri) {
1125 lwkt_schedule_self(curthread);
1132 * This yield is designed for kernel threads with a user context.
1134 * The kernel acting on behalf of the user is potentially cpu-bound,
1135 * this function will efficiently allow other threads to run and also
1136 * switch to other processes by releasing.
1138 * The lwkt_user_yield() function is designed to have very low overhead
1139 * if no yield is determined to be needed.
1142 lwkt_user_yield(void)
1144 globaldata_t gd = mycpu;
1145 thread_t td = gd->gd_curthread;
1148 * Always run any pending interrupts in case we are in a critical
1151 if ((gd->gd_reqflags & RQF_IDLECHECK_MASK) && td->td_nest_count < 2)
1156 * XXX SEVERE TEMPORARY HACK. A cpu-bound operation running in the
1157 * kernel can prevent other cpus from servicing interrupt threads
1158 * which still require the MP lock (which is a lot of them). This
1159 * has a chaining effect since if the interrupt is blocked, so is
1160 * the event, so normal scheduling will not pick up on the problem.
1162 if (cpu_contention_mask && td->td_mpcount + td->td_xpcount) {
1168 * Switch (which forces a release) if another kernel thread needs
1169 * the cpu, if userland wants us to resched, or if our kernel
1170 * quantum has run out.
1172 if (lwkt_resched_wanted() ||
1173 user_resched_wanted() ||
1174 td->td_fairq_accum < 0)
1181 * Reacquire the current process if we are released.
1183 * XXX not implemented atm. The kernel may be holding locks and such,
1184 * so we want the thread to continue to receive cpu.
1186 if (td->td_release == NULL && lp) {
1187 lp->lwp_proc->p_usched->acquire_curproc(lp);
1188 td->td_release = lwkt_passive_release;
1189 lwkt_setpri_self(TDPRI_USER_NORM);
1195 * Generic schedule. Possibly schedule threads belonging to other cpus and
1196 * deal with threads that might be blocked on a wait queue.
1198 * We have a little helper inline function which does additional work after
1199 * the thread has been enqueued, including dealing with preemption and
1200 * setting need_lwkt_resched() (which prevents the kernel from returning
1201 * to userland until it has processed higher priority threads).
1203 * It is possible for this routine to be called after a failed _enqueue
1204 * (due to the target thread migrating, sleeping, or otherwise blocked).
1205 * We have to check that the thread is actually on the run queue!
1207 * reschedok is an optimized constant propagated from lwkt_schedule() or
1208 * lwkt_schedule_noresched(). By default it is non-zero, causing a
1209 * reschedule to be requested if the target thread has a higher priority.
1210 * The port messaging code will set MSG_NORESCHED and cause reschedok to
1211 * be 0, prevented undesired reschedules.
1215 _lwkt_schedule_post(globaldata_t gd, thread_t ntd, int ccount, int reschedok)
1219 if (ntd->td_flags & TDF_RUNQ) {
1220 if (ntd->td_preemptable && reschedok) {
1221 ntd->td_preemptable(ntd, ccount); /* YYY +token */
1222 } else if (reschedok) {
1224 if (ntd->td_pri > otd->td_pri)
1225 need_lwkt_resched();
1229 * Give the thread a little fair share scheduler bump if it
1230 * has been asleep for a while. This is primarily to avoid
1231 * a degenerate case for interrupt threads where accumulator
1232 * crosses into negative territory unnecessarily.
1234 if (ntd->td_fairq_lticks != ticks) {
1235 ntd->td_fairq_lticks = ticks;
1236 ntd->td_fairq_accum += gd->gd_fairq_total_pri;
1237 if (ntd->td_fairq_accum > TDFAIRQ_MAX(gd))
1238 ntd->td_fairq_accum = TDFAIRQ_MAX(gd);
1245 _lwkt_schedule(thread_t td, int reschedok)
1247 globaldata_t mygd = mycpu;
1249 KASSERT(td != &td->td_gd->gd_idlethread,
1250 ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
1251 crit_enter_gd(mygd);
1252 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
1253 if (td == mygd->gd_curthread) {
1257 * If we own the thread, there is no race (since we are in a
1258 * critical section). If we do not own the thread there might
1259 * be a race but the target cpu will deal with it.
1262 if (td->td_gd == mygd) {
1264 _lwkt_schedule_post(mygd, td, 1, reschedok);
1266 lwkt_send_ipiq3(td->td_gd, lwkt_schedule_remote, td, 0);
1270 _lwkt_schedule_post(mygd, td, 1, reschedok);
1277 lwkt_schedule(thread_t td)
1279 _lwkt_schedule(td, 1);
1283 lwkt_schedule_noresched(thread_t td)
1285 _lwkt_schedule(td, 0);
1291 * When scheduled remotely if frame != NULL the IPIQ is being
1292 * run via doreti or an interrupt then preemption can be allowed.
1294 * To allow preemption we have to drop the critical section so only
1295 * one is present in _lwkt_schedule_post.
1298 lwkt_schedule_remote(void *arg, int arg2, struct intrframe *frame)
1300 thread_t td = curthread;
1303 if (frame && ntd->td_preemptable) {
1304 crit_exit_noyield(td);
1305 _lwkt_schedule(ntd, 1);
1306 crit_enter_quick(td);
1308 _lwkt_schedule(ntd, 1);
1313 * Thread migration using a 'Pull' method. The thread may or may not be
1314 * the current thread. It MUST be descheduled and in a stable state.
1315 * lwkt_giveaway() must be called on the cpu owning the thread.
1317 * At any point after lwkt_giveaway() is called, the target cpu may
1318 * 'pull' the thread by calling lwkt_acquire().
1320 * We have to make sure the thread is not sitting on a per-cpu tsleep
1321 * queue or it will blow up when it moves to another cpu.
1323 * MPSAFE - must be called under very specific conditions.
1326 lwkt_giveaway(thread_t td)
1328 globaldata_t gd = mycpu;
1331 if (td->td_flags & TDF_TSLEEPQ)
1333 KKASSERT(td->td_gd == gd);
1334 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
1335 td->td_flags |= TDF_MIGRATING;
1340 lwkt_acquire(thread_t td)
1345 KKASSERT(td->td_flags & TDF_MIGRATING);
1350 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
1351 crit_enter_gd(mygd);
1352 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1354 lwkt_process_ipiq();
1360 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1361 td->td_flags &= ~TDF_MIGRATING;
1364 crit_enter_gd(mygd);
1365 TAILQ_INSERT_TAIL(&mygd->gd_tdallq, td, td_allq);
1366 td->td_flags &= ~TDF_MIGRATING;
1374 * Generic deschedule. Descheduling threads other then your own should be
1375 * done only in carefully controlled circumstances. Descheduling is
1378 * This function may block if the cpu has run out of messages.
1381 lwkt_deschedule(thread_t td)
1385 if (td == curthread) {
1388 if (td->td_gd == mycpu) {
1391 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)lwkt_deschedule, td);
1401 * Set the target thread's priority. This routine does not automatically
1402 * switch to a higher priority thread, LWKT threads are not designed for
1403 * continuous priority changes. Yield if you want to switch.
1406 lwkt_setpri(thread_t td, int pri)
1408 KKASSERT(td->td_gd == mycpu);
1409 if (td->td_pri != pri) {
1412 if (td->td_flags & TDF_RUNQ) {
1424 * Set the initial priority for a thread prior to it being scheduled for
1425 * the first time. The thread MUST NOT be scheduled before or during
1426 * this call. The thread may be assigned to a cpu other then the current
1429 * Typically used after a thread has been created with TDF_STOPPREQ,
1430 * and before the thread is initially scheduled.
1433 lwkt_setpri_initial(thread_t td, int pri)
1436 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
1441 lwkt_setpri_self(int pri)
1443 thread_t td = curthread;
1445 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1447 if (td->td_flags & TDF_RUNQ) {
1458 * 1/hz tick (typically 10ms) x TDFAIRQ_SCALE (typ 8) = 80ms full cycle.
1460 * Example: two competing threads, same priority N. decrement by (2*N)
1461 * increment by N*8, each thread will get 4 ticks.
1464 lwkt_fairq_schedulerclock(thread_t td)
1468 if (td != &td->td_gd->gd_idlethread) {
1469 td->td_fairq_accum -= td->td_gd->gd_fairq_total_pri;
1470 if (td->td_fairq_accum < -TDFAIRQ_MAX(td->td_gd))
1471 td->td_fairq_accum = -TDFAIRQ_MAX(td->td_gd);
1472 if (td->td_fairq_accum < 0)
1473 need_lwkt_resched();
1474 td->td_fairq_lticks = ticks;
1476 td = td->td_preempted;
1482 lwkt_fairq_accumulate(globaldata_t gd, thread_t td)
1484 td->td_fairq_accum += td->td_pri * TDFAIRQ_SCALE;
1485 if (td->td_fairq_accum > TDFAIRQ_MAX(td->td_gd))
1486 td->td_fairq_accum = TDFAIRQ_MAX(td->td_gd);
1490 * Migrate the current thread to the specified cpu.
1492 * This is accomplished by descheduling ourselves from the current cpu,
1493 * moving our thread to the tdallq of the target cpu, IPI messaging the
1494 * target cpu, and switching out. TDF_MIGRATING prevents scheduling
1495 * races while the thread is being migrated.
1497 * We must be sure to remove ourselves from the current cpu's tsleepq
1498 * before potentially moving to another queue. The thread can be on
1499 * a tsleepq due to a left-over tsleep_interlock().
1502 static void lwkt_setcpu_remote(void *arg);
1506 lwkt_setcpu_self(globaldata_t rgd)
1509 thread_t td = curthread;
1511 if (td->td_gd != rgd) {
1512 crit_enter_quick(td);
1513 if (td->td_flags & TDF_TSLEEPQ)
1515 td->td_flags |= TDF_MIGRATING;
1516 lwkt_deschedule_self(td);
1517 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1518 lwkt_send_ipiq(rgd, (ipifunc1_t)lwkt_setcpu_remote, td);
1520 /* we are now on the target cpu */
1521 TAILQ_INSERT_TAIL(&rgd->gd_tdallq, td, td_allq);
1522 crit_exit_quick(td);
1528 lwkt_migratecpu(int cpuid)
1533 rgd = globaldata_find(cpuid);
1534 lwkt_setcpu_self(rgd);
1539 * Remote IPI for cpu migration (called while in a critical section so we
1540 * do not have to enter another one). The thread has already been moved to
1541 * our cpu's allq, but we must wait for the thread to be completely switched
1542 * out on the originating cpu before we schedule it on ours or the stack
1543 * state may be corrupt. We clear TDF_MIGRATING after flushing the GD
1544 * change to main memory.
1546 * XXX The use of TDF_MIGRATING might not be sufficient to avoid races
1547 * against wakeups. It is best if this interface is used only when there
1548 * are no pending events that might try to schedule the thread.
1552 lwkt_setcpu_remote(void *arg)
1555 globaldata_t gd = mycpu;
1557 while (td->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) {
1559 lwkt_process_ipiq();
1566 td->td_flags &= ~TDF_MIGRATING;
1567 KKASSERT(td->td_lwp == NULL || (td->td_lwp->lwp_flag & LWP_ONRUNQ) == 0);
1573 lwkt_preempted_proc(void)
1575 thread_t td = curthread;
1576 while (td->td_preempted)
1577 td = td->td_preempted;
1582 * Create a kernel process/thread/whatever. It shares it's address space
1583 * with proc0 - ie: kernel only.
1585 * NOTE! By default new threads are created with the MP lock held. A
1586 * thread which does not require the MP lock should release it by calling
1587 * rel_mplock() at the start of the new thread.
1590 lwkt_create(void (*func)(void *), void *arg, struct thread **tdp,
1591 thread_t template, int tdflags, int cpu, const char *fmt, ...)
1596 td = lwkt_alloc_thread(template, LWKT_THREAD_STACK, cpu,
1600 cpu_set_thread_handler(td, lwkt_exit, func, arg);
1603 * Set up arg0 for 'ps' etc
1605 __va_start(ap, fmt);
1606 kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
1610 * Schedule the thread to run
1612 if ((td->td_flags & TDF_STOPREQ) == 0)
1615 td->td_flags &= ~TDF_STOPREQ;
1620 * Destroy an LWKT thread. Warning! This function is not called when
1621 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1622 * uses a different reaping mechanism.
1627 thread_t td = curthread;
1632 * Do any cleanup that might block here
1634 if (td->td_flags & TDF_VERBOSE)
1635 kprintf("kthread %p %s has exited\n", td, td->td_comm);
1638 dsched_exit_thread(td);
1641 * Get us into a critical section to interlock gd_freetd and loop
1642 * until we can get it freed.
1644 * We have to cache the current td in gd_freetd because objcache_put()ing
1645 * it would rip it out from under us while our thread is still active.
1648 crit_enter_quick(td);
1649 while ((std = gd->gd_freetd) != NULL) {
1650 KKASSERT((std->td_flags & (TDF_RUNNING|TDF_PREEMPT_LOCK)) == 0);
1651 gd->gd_freetd = NULL;
1652 objcache_put(thread_cache, std);
1656 * Remove thread resources from kernel lists and deschedule us for
1657 * the last time. We cannot block after this point or we may end
1658 * up with a stale td on the tsleepq.
1660 if (td->td_flags & TDF_TSLEEPQ)
1662 lwkt_deschedule_self(td);
1663 lwkt_remove_tdallq(td);
1668 KKASSERT(gd->gd_freetd == NULL);
1669 if (td->td_flags & TDF_ALLOCATED_THREAD)
1675 lwkt_remove_tdallq(thread_t td)
1677 KKASSERT(td->td_gd == mycpu);
1678 TAILQ_REMOVE(&td->td_gd->gd_tdallq, td, td_allq);
1682 * Code reduction and branch prediction improvements. Call/return
1683 * overhead on modern cpus often degenerates into 0 cycles due to
1684 * the cpu's branch prediction hardware and return pc cache. We
1685 * can take advantage of this by not inlining medium-complexity
1686 * functions and we can also reduce the branch prediction impact
1687 * by collapsing perfectly predictable branches into a single
1688 * procedure instead of duplicating it.
1690 * Is any of this noticeable? Probably not, so I'll take the
1691 * smaller code size.
1694 crit_exit_wrapper(__DEBUG_CRIT_ARG__)
1696 _crit_exit(mycpu __DEBUG_CRIT_PASS_ARG__);
1702 thread_t td = curthread;
1703 int lcrit = td->td_critcount;
1705 td->td_critcount = 0;
1706 panic("td_critcount is/would-go negative! %p %d", td, lcrit);
1713 * Called from debugger/panic on cpus which have been stopped. We must still
1714 * process the IPIQ while stopped, even if we were stopped while in a critical
1717 * If we are dumping also try to process any pending interrupts. This may
1718 * or may not work depending on the state of the cpu at the point it was
1722 lwkt_smp_stopped(void)
1724 globaldata_t gd = mycpu;
1728 lwkt_process_ipiq();
1731 lwkt_process_ipiq();