2 * Copyright (c) 2003 Matthew Dillon <dillon@backplane.com>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.56 2004/03/01 06:33:17 dillon Exp $
30 * Each cpu in a system has its own self-contained light weight kernel
31 * thread scheduler, which means that generally speaking we only need
32 * to use a critical section to avoid problems. Foreign thread
33 * scheduling is queued via (async) IPIs.
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/kernel.h>
42 #include <sys/rtprio.h>
43 #include <sys/queue.h>
44 #include <sys/thread2.h>
45 #include <sys/sysctl.h>
46 #include <sys/kthread.h>
47 #include <machine/cpu.h>
52 #include <vm/vm_param.h>
53 #include <vm/vm_kern.h>
54 #include <vm/vm_object.h>
55 #include <vm/vm_page.h>
56 #include <vm/vm_map.h>
57 #include <vm/vm_pager.h>
58 #include <vm/vm_extern.h>
59 #include <vm/vm_zone.h>
61 #include <machine/stdarg.h>
62 #include <machine/ipl.h>
63 #include <machine/smp.h>
65 #define THREAD_STACK (UPAGES * PAGE_SIZE)
69 #include <sys/stdint.h>
70 #include <libcaps/thread.h>
71 #include <sys/thread.h>
72 #include <sys/msgport.h>
73 #include <sys/errno.h>
74 #include <libcaps/globaldata.h>
75 #include <sys/thread2.h>
76 #include <sys/msgport2.h>
80 #include <machine/cpufunc.h>
81 #include <machine/lock.h>
85 static int untimely_switch = 0;
87 static int panic_on_cscount = 0;
89 static __int64_t switch_count = 0;
90 static __int64_t preempt_hit = 0;
91 static __int64_t preempt_miss = 0;
92 static __int64_t preempt_weird = 0;
96 SYSCTL_INT(_lwkt, OID_AUTO, untimely_switch, CTLFLAG_RW, &untimely_switch, 0, "");
98 SYSCTL_INT(_lwkt, OID_AUTO, panic_on_cscount, CTLFLAG_RW, &panic_on_cscount, 0, "");
100 SYSCTL_QUAD(_lwkt, OID_AUTO, switch_count, CTLFLAG_RW, &switch_count, 0, "");
101 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_hit, CTLFLAG_RW, &preempt_hit, 0, "");
102 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_miss, CTLFLAG_RW, &preempt_miss, 0, "");
103 SYSCTL_QUAD(_lwkt, OID_AUTO, preempt_weird, CTLFLAG_RW, &preempt_weird, 0, "");
108 * These helper procedures handle the runq, they can only be called from
109 * within a critical section.
111 * WARNING! Prior to SMP being brought up it is possible to enqueue and
112 * dequeue threads belonging to other cpus, so be sure to use td->td_gd
113 * instead of 'mycpu' when referencing the globaldata structure. Once
114 * SMP live enqueuing and dequeueing only occurs on the current cpu.
118 _lwkt_dequeue(thread_t td)
120 if (td->td_flags & TDF_RUNQ) {
121 int nq = td->td_pri & TDPRI_MASK;
122 struct globaldata *gd = td->td_gd;
124 td->td_flags &= ~TDF_RUNQ;
125 TAILQ_REMOVE(&gd->gd_tdrunq[nq], td, td_threadq);
126 /* runqmask is passively cleaned up by the switcher */
132 _lwkt_enqueue(thread_t td)
134 if ((td->td_flags & TDF_RUNQ) == 0) {
135 int nq = td->td_pri & TDPRI_MASK;
136 struct globaldata *gd = td->td_gd;
138 td->td_flags |= TDF_RUNQ;
139 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], td, td_threadq);
140 gd->gd_runqmask |= 1 << nq;
146 _lwkt_wantresched(thread_t ntd, thread_t cur)
148 return((ntd->td_pri & TDPRI_MASK) > (cur->td_pri & TDPRI_MASK));
154 * LWKTs operate on a per-cpu basis
156 * WARNING! Called from early boot, 'mycpu' may not work yet.
159 lwkt_gdinit(struct globaldata *gd)
163 for (i = 0; i < sizeof(gd->gd_tdrunq)/sizeof(gd->gd_tdrunq[0]); ++i)
164 TAILQ_INIT(&gd->gd_tdrunq[i]);
166 TAILQ_INIT(&gd->gd_tdallq);
172 * Initialize a thread wait structure prior to first use.
174 * NOTE! called from low level boot code, we cannot do anything fancy!
177 lwkt_wait_init(lwkt_wait_t w)
179 lwkt_token_init(&w->wa_token);
180 TAILQ_INIT(&w->wa_waitq);
186 * Create a new thread. The thread must be associated with a process context
187 * or LWKT start address before it can be scheduled. If the target cpu is
188 * -1 the thread will be created on the current cpu.
190 * If you intend to create a thread without a process context this function
191 * does everything except load the startup and switcher function.
194 lwkt_alloc_thread(struct thread *td, int cpu)
201 if (mycpu->gd_tdfreecount > 0) {
202 --mycpu->gd_tdfreecount;
203 td = TAILQ_FIRST(&mycpu->gd_tdfreeq);
204 KASSERT(td != NULL && (td->td_flags & TDF_RUNNING) == 0,
205 ("lwkt_alloc_thread: unexpected NULL or corrupted td"));
206 TAILQ_REMOVE(&mycpu->gd_tdfreeq, td, td_threadq);
208 stack = td->td_kstack;
209 flags = td->td_flags & (TDF_ALLOCATED_STACK|TDF_ALLOCATED_THREAD);
213 td = zalloc(thread_zone);
215 td = malloc(sizeof(struct thread));
217 td->td_kstack = NULL;
218 flags |= TDF_ALLOCATED_THREAD;
221 if ((stack = td->td_kstack) == NULL) {
223 stack = (void *)kmem_alloc(kernel_map, THREAD_STACK);
225 stack = libcaps_alloc_stack(THREAD_STACK);
227 flags |= TDF_ALLOCATED_STACK;
230 lwkt_init_thread(td, stack, flags, mycpu);
232 lwkt_init_thread(td, stack, flags, globaldata_find(cpu));
239 * Initialize a preexisting thread structure. This function is used by
240 * lwkt_alloc_thread() and also used to initialize the per-cpu idlethread.
242 * All threads start out in a critical section at a priority of
243 * TDPRI_KERN_DAEMON. Higher level code will modify the priority as
244 * appropriate. This function may send an IPI message when the
245 * requested cpu is not the current cpu and consequently gd_tdallq may
246 * not be initialized synchronously from the point of view of the originating
249 * NOTE! we have to be careful in regards to creating threads for other cpus
250 * if SMP has not yet been activated.
255 lwkt_init_thread_remote(void *arg)
259 TAILQ_INSERT_TAIL(&td->td_gd->gd_tdallq, td, td_allq);
265 lwkt_init_thread(thread_t td, void *stack, int flags, struct globaldata *gd)
267 bzero(td, sizeof(struct thread));
268 td->td_kstack = stack;
269 td->td_flags |= flags;
271 td->td_pri = TDPRI_KERN_DAEMON + TDPRI_CRIT;
272 lwkt_initport(&td->td_msgport, td);
273 pmap_init_thread(td);
277 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
280 lwkt_send_ipiq(gd, lwkt_init_thread_remote, td);
284 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq);
292 lwkt_set_comm(thread_t td, const char *ctl, ...)
297 vsnprintf(td->td_comm, sizeof(td->td_comm), ctl, va);
302 lwkt_hold(thread_t td)
308 lwkt_rele(thread_t td)
310 KKASSERT(td->td_refs > 0);
317 lwkt_wait_free(thread_t td)
320 tsleep(td, 0, "tdreap", hz);
326 lwkt_free_thread(thread_t td)
328 struct globaldata *gd = mycpu;
330 KASSERT((td->td_flags & TDF_RUNNING) == 0,
331 ("lwkt_free_thread: did not exit! %p", td));
334 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq);
335 if (gd->gd_tdfreecount < CACHE_NTHREADS &&
336 (td->td_flags & TDF_ALLOCATED_THREAD)
338 ++gd->gd_tdfreecount;
339 TAILQ_INSERT_HEAD(&gd->gd_tdfreeq, td, td_threadq);
343 if (td->td_kstack && (td->td_flags & TDF_ALLOCATED_STACK)) {
345 kmem_free(kernel_map, (vm_offset_t)td->td_kstack, THREAD_STACK);
347 libcaps_free_stack(td->td_kstack, THREAD_STACK);
350 td->td_kstack = NULL;
352 if (td->td_flags & TDF_ALLOCATED_THREAD) {
354 zfree(thread_zone, td);
364 * Switch to the next runnable lwkt. If no LWKTs are runnable then
365 * switch to the idlethread. Switching must occur within a critical
366 * section to avoid races with the scheduling queue.
368 * We always have full control over our cpu's run queue. Other cpus
369 * that wish to manipulate our queue must use the cpu_*msg() calls to
370 * talk to our cpu, so a critical section is all that is needed and
371 * the result is very, very fast thread switching.
373 * The LWKT scheduler uses a fixed priority model and round-robins at
374 * each priority level. User process scheduling is a totally
375 * different beast and LWKT priorities should not be confused with
376 * user process priorities.
378 * The MP lock may be out of sync with the thread's td_mpcount. lwkt_switch()
379 * cleans it up. Note that the td_switch() function cannot do anything that
380 * requires the MP lock since the MP lock will have already been setup for
381 * the target thread (not the current thread). It's nice to have a scheduler
382 * that does not need the MP lock to work because it allows us to do some
383 * really cool high-performance MP lock optimizations.
390 thread_t td = curthread;
397 * Switching from within a 'fast' (non thread switched) interrupt is
400 if (mycpu->gd_intr_nesting_level && panicstr == NULL) {
401 panic("lwkt_switch: cannot switch from within a fast interrupt, yet\n");
405 * Passive release (used to transition from user to kernel mode
406 * when we block or switch rather then when we enter the kernel).
407 * This function is NOT called if we are switching into a preemption
408 * or returning from a preemption. Typically this causes us to lose
409 * our P_CURPROC designation (if we have one) and become a true LWKT
410 * thread, and may also hand P_CURPROC to another process and schedule
421 * td_mpcount cannot be used to determine if we currently hold the
422 * MP lock because get_mplock() will increment it prior to attempting
423 * to get the lock, and switch out if it can't. Our ownership of
424 * the actual lock will remain stable while we are in a critical section
425 * (but, of course, another cpu may own or release the lock so the
426 * actual value of mp_lock is not stable).
428 mpheld = MP_LOCK_HELD();
430 if (td->td_cscount) {
431 printf("Diagnostic: attempt to switch while mastering cpusync: %p\n",
433 if (panic_on_cscount)
434 panic("switching while mastering cpusync");
438 if ((ntd = td->td_preempted) != NULL) {
440 * We had preempted another thread on this cpu, resume the preempted
441 * thread. This occurs transparently, whether the preempted thread
442 * was scheduled or not (it may have been preempted after descheduling
445 * We have to setup the MP lock for the original thread after backing
446 * out the adjustment that was made to curthread when the original
449 KKASSERT(ntd->td_flags & TDF_PREEMPT_LOCK);
451 if (ntd->td_mpcount && mpheld == 0) {
452 panic("MPLOCK NOT HELD ON RETURN: %p %p %d %d\n",
453 td, ntd, td->td_mpcount, ntd->td_mpcount);
455 if (ntd->td_mpcount) {
456 td->td_mpcount -= ntd->td_mpcount;
457 KKASSERT(td->td_mpcount >= 0);
460 ntd->td_flags |= TDF_PREEMPT_DONE;
461 /* YYY release mp lock on switchback if original doesn't need it */
464 * Priority queue / round-robin at each priority. Note that user
465 * processes run at a fixed, low priority and the user process
466 * scheduler deals with interactions between user processes
467 * by scheduling and descheduling them from the LWKT queue as
470 * We have to adjust the MP lock for the target thread. If we
471 * need the MP lock and cannot obtain it we try to locate a
472 * thread that does not need the MP lock. If we cannot, we spin
475 * A similar issue exists for the tokens held by the target thread.
476 * If we cannot obtain ownership of the tokens we cannot immediately
477 * schedule the thread.
481 * We are switching threads. If there are any pending requests for
482 * tokens we can satisfy all of them here.
486 if (gd->gd_tokreqbase)
487 lwkt_drain_token_requests();
491 if (gd->gd_runqmask) {
492 int nq = bsrl(gd->gd_runqmask);
493 if ((ntd = TAILQ_FIRST(&gd->gd_tdrunq[nq])) == NULL) {
494 gd->gd_runqmask &= ~(1 << nq);
499 * If the target needs the MP lock and we couldn't get it,
500 * or if the target is holding tokens and we could not
501 * gain ownership of the tokens, continue looking for a
502 * thread to schedule and spin instead of HLT if we can't.
504 if ((ntd->td_mpcount && mpheld == 0 && !cpu_try_mplock()) ||
505 (ntd->td_toks && lwkt_chktokens(ntd) == 0)
507 u_int32_t rqmask = gd->gd_runqmask;
509 TAILQ_FOREACH(ntd, &gd->gd_tdrunq[nq], td_threadq) {
510 if (ntd->td_mpcount && !mpheld && !cpu_try_mplock())
512 mpheld = MP_LOCK_HELD();
513 if (ntd->td_toks && !lwkt_chktokens(ntd))
519 rqmask &= ~(1 << nq);
523 ntd = &gd->gd_idlethread;
524 ntd->td_flags |= TDF_IDLE_NOHLT;
526 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
527 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
530 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
531 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
534 TAILQ_REMOVE(&gd->gd_tdrunq[nq], ntd, td_threadq);
535 TAILQ_INSERT_TAIL(&gd->gd_tdrunq[nq], ntd, td_threadq);
539 * We have nothing to run but only let the idle loop halt
540 * the cpu if there are no pending interrupts.
542 ntd = &gd->gd_idlethread;
543 if (gd->gd_reqflags & RQF_IDLECHECK_MASK)
544 ntd->td_flags |= TDF_IDLE_NOHLT;
547 KASSERT(ntd->td_pri >= TDPRI_CRIT,
548 ("priority problem in lwkt_switch %d %d", td->td_pri, ntd->td_pri));
551 * Do the actual switch. If the new target does not need the MP lock
552 * and we are holding it, release the MP lock. If the new target requires
553 * the MP lock we have already acquired it for the target.
556 if (ntd->td_mpcount == 0 ) {
560 ASSERT_MP_LOCK_HELD();
571 * Switch if another thread has a higher priority. Do not switch to other
572 * threads at the same priority.
577 struct globaldata *gd = mycpu;
578 struct thread *td = gd->gd_curthread;
580 if ((td->td_pri & TDPRI_MASK) < bsrl(gd->gd_runqmask)) {
586 * Request that the target thread preempt the current thread. Preemption
587 * only works under a specific set of conditions:
589 * - We are not preempting ourselves
590 * - The target thread is owned by the current cpu
591 * - We are not currently being preempted
592 * - The target is not currently being preempted
593 * - We are able to satisfy the target's MP lock requirements (if any).
595 * THE CALLER OF LWKT_PREEMPT() MUST BE IN A CRITICAL SECTION. Typically
596 * this is called via lwkt_schedule() through the td_preemptable callback.
597 * critpri is the managed critical priority that we should ignore in order
598 * to determine whether preemption is possible (aka usually just the crit
599 * priority of lwkt_schedule() itself).
601 * XXX at the moment we run the target thread in a critical section during
602 * the preemption in order to prevent the target from taking interrupts
603 * that *WE* can't. Preemption is strictly limited to interrupt threads
604 * and interrupt-like threads, outside of a critical section, and the
605 * preempted source thread will be resumed the instant the target blocks
606 * whether or not the source is scheduled (i.e. preemption is supposed to
607 * be as transparent as possible).
609 * The target thread inherits our MP count (added to its own) for the
610 * duration of the preemption in order to preserve the atomicy of the
611 * MP lock during the preemption. Therefore, any preempting targets must be
612 * careful in regards to MP assertions. Note that the MP count may be
613 * out of sync with the physical mp_lock, but we do not have to preserve
614 * the original ownership of the lock if it was out of synch (that is, we
615 * can leave it synchronized on return).
618 lwkt_preempt(thread_t ntd, int critpri)
620 struct globaldata *gd = mycpu;
621 thread_t td = gd->gd_curthread;
628 * The caller has put us in a critical section. We can only preempt
629 * if the caller of the caller was not in a critical section (basically
630 * a local interrupt), as determined by the 'critpri' parameter. If
631 * we are unable to preempt
633 * YYY The target thread must be in a critical section (else it must
634 * inherit our critical section? I dunno yet).
636 * Any tokens held by the target may not be held by thread(s) being
637 * preempted. We take the easy way out and do not preempt if
638 * the target is holding tokens.
640 KASSERT(ntd->td_pri >= TDPRI_CRIT, ("BADCRIT0 %d", ntd->td_pri));
643 if (!_lwkt_wantresched(ntd, td)) {
647 if ((td->td_pri & ~TDPRI_MASK) > critpri) {
652 if (ntd->td_gd != gd) {
658 * Take the easy way out and do not preempt if the target is holding
659 * one or more tokens. We could test whether the thread(s) being
660 * preempted interlock against the target thread's tokens and whether
661 * we can get all the target thread's tokens, but this situation
662 * should not occur very often so its easier to simply not preempt.
664 if (ntd->td_toks != NULL) {
668 if (td == ntd || ((td->td_flags | ntd->td_flags) & TDF_PREEMPT_LOCK)) {
672 if (ntd->td_preempted) {
678 * note: an interrupt might have occured just as we were transitioning
679 * to or from the MP lock. In this case td_mpcount will be pre-disposed
680 * (non-zero) but not actually synchronized with the actual state of the
681 * lock. We can use it to imply an MP lock requirement for the
682 * preemption but we cannot use it to test whether we hold the MP lock
685 savecnt = td->td_mpcount;
686 mpheld = MP_LOCK_HELD();
687 ntd->td_mpcount += td->td_mpcount;
688 if (mpheld == 0 && ntd->td_mpcount && !cpu_try_mplock()) {
689 ntd->td_mpcount -= td->td_mpcount;
696 ntd->td_preempted = td;
697 td->td_flags |= TDF_PREEMPT_LOCK;
699 KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
701 KKASSERT(savecnt == td->td_mpcount);
702 mpheld = MP_LOCK_HELD();
703 if (mpheld && td->td_mpcount == 0)
705 else if (mpheld == 0 && td->td_mpcount)
706 panic("lwkt_preempt(): MP lock was not held through");
708 ntd->td_preempted = NULL;
709 td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
713 * Yield our thread while higher priority threads are pending. This is
714 * typically called when we leave a critical section but it can be safely
715 * called while we are in a critical section.
717 * This function will not generally yield to equal priority threads but it
718 * can occur as a side effect. Note that lwkt_switch() is called from
719 * inside the critical section to prevent its own crit_exit() from reentering
720 * lwkt_yield_quick().
722 * gd_reqflags indicates that *something* changed, e.g. an interrupt or softint
723 * came along but was blocked and made pending.
725 * (self contained on a per cpu basis)
728 lwkt_yield_quick(void)
730 globaldata_t gd = mycpu;
731 thread_t td = gd->gd_curthread;
734 * gd_reqflags is cleared in splz if the cpl is 0. If we were to clear
735 * it with a non-zero cpl then we might not wind up calling splz after
736 * a task switch when the critical section is exited even though the
737 * new task could accept the interrupt.
739 * XXX from crit_exit() only called after last crit section is released.
740 * If called directly will run splz() even if in a critical section.
742 * td_nest_count prevent deep nesting via splz() or doreti(). Note that
743 * except for this special case, we MUST call splz() here to handle any
744 * pending ints, particularly after we switch, or we might accidently
745 * halt the cpu with interrupts pending.
747 if (gd->gd_reqflags && td->td_nest_count < 2)
751 * YYY enabling will cause wakeup() to task-switch, which really
752 * confused the old 4.x code. This is a good way to simulate
753 * preemption and MP without actually doing preemption or MP, because a
754 * lot of code assumes that wakeup() does not block.
756 if (untimely_switch && td->td_nest_count == 0 &&
757 gd->gd_intr_nesting_level == 0
761 * YYY temporary hacks until we disassociate the userland scheduler
762 * from the LWKT scheduler.
764 if (td->td_flags & TDF_RUNQ) {
765 lwkt_switch(); /* will not reenter yield function */
767 lwkt_schedule_self(); /* make sure we are scheduled */
768 lwkt_switch(); /* will not reenter yield function */
769 lwkt_deschedule_self(); /* make sure we are descheduled */
771 crit_exit_noyield(td);
776 * This implements a normal yield which, unlike _quick, will yield to equal
777 * priority threads as well. Note that gd_reqflags tests will be handled by
778 * the crit_exit() call in lwkt_switch().
780 * (self contained on a per cpu basis)
785 lwkt_schedule_self();
790 * Schedule a thread to run. As the current thread we can always safely
791 * schedule ourselves, and a shortcut procedure is provided for that
794 * (non-blocking, self contained on a per cpu basis)
797 lwkt_schedule_self(void)
799 thread_t td = curthread;
801 crit_enter_quick(td);
802 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
803 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule_self(): scheduling gd_idlethread is illegal!"));
806 if (td->td_proc && td->td_proc->p_stat == SSLEEP)
807 panic("SCHED SELF PANIC");
813 * Generic schedule. Possibly schedule threads belonging to other cpus and
814 * deal with threads that might be blocked on a wait queue.
816 * YYY this is one of the best places to implement load balancing code.
817 * Load balancing can be accomplished by requesting other sorts of actions
818 * for the thread in question.
821 lwkt_schedule(thread_t td)
824 KASSERT(td != &td->td_gd->gd_idlethread, ("lwkt_schedule(): scheduling gd_idlethread is illegal!"));
825 if ((td->td_flags & TDF_PREEMPT_LOCK) == 0 && td->td_proc
826 && td->td_proc->p_stat == SSLEEP
828 printf("PANIC schedule curtd = %p (%d %d) target %p (%d %d)\n",
830 curthread->td_proc ? curthread->td_proc->p_pid : -1,
831 curthread->td_proc ? curthread->td_proc->p_stat : -1,
833 td->td_proc ? curthread->td_proc->p_pid : -1,
834 td->td_proc ? curthread->td_proc->p_stat : -1
836 panic("SCHED PANIC");
840 if (td == curthread) {
846 * If the thread is on a wait list we have to send our scheduling
847 * request to the owner of the wait structure. Otherwise we send
848 * the scheduling request to the cpu owning the thread. Races
849 * are ok, the target will forward the message as necessary (the
850 * message may chase the thread around before it finally gets
853 * (remember, wait structures use stable storage)
855 if ((w = td->td_wait) != NULL) {
858 if (lwkt_trytoken(&wref, &w->wa_token)) {
859 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
863 if (td->td_gd == mycpu) {
865 if (td->td_preemptable)
866 td->td_preemptable(td, TDPRI_CRIT*2); /* YYY +token */
867 else if (_lwkt_wantresched(td, curthread))
870 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_schedule, td);
874 if (td->td_preemptable)
875 td->td_preemptable(td, TDPRI_CRIT*2); /* YYY +token */
876 else if (_lwkt_wantresched(td, curthread))
879 lwkt_reltoken(&wref);
881 lwkt_send_ipiq(w->wa_token.t_cpu, (ipifunc_t)lwkt_schedule, td);
885 * If the wait structure is NULL and we own the thread, there
886 * is no race (since we are in a critical section). If we
887 * do not own the thread there might be a race but the
888 * target cpu will deal with it.
891 if (td->td_gd == mycpu) {
893 if (td->td_preemptable) {
894 td->td_preemptable(td, TDPRI_CRIT);
895 } else if (_lwkt_wantresched(td, curthread)) {
899 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_schedule, td);
903 if (td->td_preemptable) {
904 td->td_preemptable(td, TDPRI_CRIT);
905 } else if (_lwkt_wantresched(td, curthread)) {
915 * Managed acquisition. This code assumes that the MP lock is held for
916 * the tdallq operation and that the thread has been descheduled from its
917 * original cpu. We also have to wait for the thread to be entirely switched
918 * out on its original cpu (this is usually fast enough that we never loop)
919 * since the LWKT system does not have to hold the MP lock while switching
920 * and the target may have released it before switching.
923 lwkt_acquire(thread_t td)
925 struct globaldata *gd;
928 KKASSERT((td->td_flags & TDF_RUNQ) == 0);
929 while (td->td_flags & TDF_RUNNING) /* XXX spin */
933 TAILQ_REMOVE(&gd->gd_tdallq, td, td_allq); /* protected by BGL */
936 TAILQ_INSERT_TAIL(&gd->gd_tdallq, td, td_allq); /* protected by BGL */
942 * Deschedule a thread.
944 * (non-blocking, self contained on a per cpu basis)
947 lwkt_deschedule_self(void)
949 thread_t td = curthread;
952 KASSERT(td->td_wait == NULL, ("lwkt_schedule_self(): td_wait not NULL!"));
958 * Generic deschedule. Descheduling threads other then your own should be
959 * done only in carefully controlled circumstances. Descheduling is
962 * This function may block if the cpu has run out of messages.
965 lwkt_deschedule(thread_t td)
968 if (td == curthread) {
971 if (td->td_gd == mycpu) {
974 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_deschedule, td);
981 * Set the target thread's priority. This routine does not automatically
982 * switch to a higher priority thread, LWKT threads are not designed for
983 * continuous priority changes. Yield if you want to switch.
985 * We have to retain the critical section count which uses the high bits
986 * of the td_pri field. The specified priority may also indicate zero or
987 * more critical sections by adding TDPRI_CRIT*N.
990 lwkt_setpri(thread_t td, int pri)
993 KKASSERT(td->td_gd == mycpu);
995 if (td->td_flags & TDF_RUNQ) {
997 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1000 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1006 lwkt_setpri_self(int pri)
1008 thread_t td = curthread;
1010 KKASSERT(pri >= 0 && pri <= TDPRI_MAX);
1012 if (td->td_flags & TDF_RUNQ) {
1014 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1017 td->td_pri = (td->td_pri & ~TDPRI_MASK) + pri;
1023 lwkt_preempted_proc(void)
1025 thread_t td = curthread;
1026 while (td->td_preempted)
1027 td = td->td_preempted;
1028 return(td->td_proc);
1032 * Block on the specified wait queue until signaled. A generation number
1033 * must be supplied to interlock the wait queue. The function will
1034 * return immediately if the generation number does not match the wait
1035 * structure's generation number.
1038 lwkt_block(lwkt_wait_t w, const char *wmesg, int *gen)
1040 thread_t td = curthread;
1043 lwkt_gettoken(&ilock, &w->wa_token);
1045 if (w->wa_gen == *gen) {
1047 TAILQ_INSERT_TAIL(&w->wa_waitq, td, td_threadq);
1050 td->td_wmesg = wmesg;
1053 if (td->td_wmesg != NULL) {
1060 lwkt_reltoken(&ilock);
1064 * Signal a wait queue. We gain ownership of the wait queue in order to
1065 * signal it. Once a thread is removed from the wait queue we have to
1066 * deal with the cpu owning the thread.
1068 * Note: alternatively we could message the target cpu owning the wait
1069 * queue. YYY implement as sysctl.
1072 lwkt_signal(lwkt_wait_t w, int count)
1077 lwkt_gettoken(&ilock, &w->wa_token);
1081 count = w->wa_count;
1082 while ((td = TAILQ_FIRST(&w->wa_waitq)) != NULL && count) {
1085 TAILQ_REMOVE(&w->wa_waitq, td, td_threadq);
1087 td->td_wmesg = NULL;
1088 if (td->td_gd == mycpu) {
1091 lwkt_send_ipiq(td->td_gd, (ipifunc_t)lwkt_schedule, td);
1095 lwkt_reltoken(&ilock);
1099 * Create a kernel process/thread/whatever. It shares it's address space
1100 * with proc0 - ie: kernel only.
1102 * NOTE! By default new threads are created with the MP lock held. A
1103 * thread which does not require the MP lock should release it by calling
1104 * rel_mplock() at the start of the new thread.
1107 lwkt_create(void (*func)(void *), void *arg,
1108 struct thread **tdp, thread_t template, int tdflags, int cpu,
1109 const char *fmt, ...)
1114 td = lwkt_alloc_thread(template, cpu);
1117 cpu_set_thread_handler(td, lwkt_exit, func, arg);
1118 td->td_flags |= TDF_VERBOSE | tdflags;
1124 * Set up arg0 for 'ps' etc
1126 __va_start(ap, fmt);
1127 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
1131 * Schedule the thread to run
1133 if ((td->td_flags & TDF_STOPREQ) == 0)
1136 td->td_flags &= ~TDF_STOPREQ;
1141 * kthread_* is specific to the kernel and is not needed by userland.
1146 * Destroy an LWKT thread. Warning! This function is not called when
1147 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1148 * uses a different reaping mechanism.
1153 thread_t td = curthread;
1155 if (td->td_flags & TDF_VERBOSE)
1156 printf("kthread %p %s has exited\n", td, td->td_comm);
1159 lwkt_deschedule_self();
1160 ++mycpu->gd_tdfreecount;
1161 TAILQ_INSERT_TAIL(&mycpu->gd_tdfreeq, td, td_threadq);
1166 * Create a kernel process/thread/whatever. It shares it's address space
1167 * with proc0 - ie: kernel only. 5.x compatible.
1169 * NOTE! By default kthreads are created with the MP lock held. A
1170 * thread which does not require the MP lock should release it by calling
1171 * rel_mplock() at the start of the new thread.
1174 kthread_create(void (*func)(void *), void *arg,
1175 struct thread **tdp, const char *fmt, ...)
1180 td = lwkt_alloc_thread(NULL, -1);
1183 cpu_set_thread_handler(td, kthread_exit, func, arg);
1184 td->td_flags |= TDF_VERBOSE;
1190 * Set up arg0 for 'ps' etc
1192 __va_start(ap, fmt);
1193 vsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
1197 * Schedule the thread to run
1204 * Destroy an LWKT thread. Warning! This function is not called when
1205 * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
1206 * uses a different reaping mechanism.
1208 * XXX duplicates lwkt_exit()
1216 #endif /* _KERNEL */
1221 thread_t td = curthread;
1222 int lpri = td->td_pri;
1225 panic("td_pri is/would-go negative! %p %d", td, lpri);