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[dragonfly.git] / sys / kern / lwkt_token.c
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1 /*
2 * Copyright (c) 2003,2004,2009 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
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
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
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
32 * SUCH DAMAGE.
36 * lwkt_token - Implement soft token locks.
38 * Tokens are locks which serialize a thread only while the thread is
39 * running. If the thread blocks all tokens are released, then reacquired
40 * when the thread resumes.
42 * This implementation requires no critical sections or spin locks, but
43 * does use atomic_cmpset_ptr().
45 * Tokens may be recursively acquired by the same thread. However the
46 * caller must be sure to release such tokens in reverse order.
48 #include <sys/param.h>
49 #include <sys/systm.h>
50 #include <sys/kernel.h>
51 #include <sys/proc.h>
52 #include <sys/rtprio.h>
53 #include <sys/queue.h>
54 #include <sys/sysctl.h>
55 #include <sys/ktr.h>
56 #include <sys/kthread.h>
57 #include <machine/cpu.h>
58 #include <sys/lock.h>
59 #include <sys/spinlock.h>
61 #include <sys/thread2.h>
62 #include <sys/spinlock2.h>
63 #include <sys/mplock2.h>
65 #include <vm/vm.h>
66 #include <vm/vm_param.h>
67 #include <vm/vm_kern.h>
68 #include <vm/vm_object.h>
69 #include <vm/vm_page.h>
70 #include <vm/vm_map.h>
71 #include <vm/vm_pager.h>
72 #include <vm/vm_extern.h>
73 #include <vm/vm_zone.h>
75 #include <machine/stdarg.h>
76 #include <machine/smp.h>
78 #include "opt_ddb.h"
79 #ifdef DDB
80 #include <ddb/ddb.h>
81 #endif
83 extern int lwkt_sched_debug;
85 #ifndef LWKT_NUM_POOL_TOKENS
86 #define LWKT_NUM_POOL_TOKENS 16661
87 #endif
89 struct lwkt_pool_token {
90 struct lwkt_token token;
91 } __cachealign;
93 static struct lwkt_pool_token pool_tokens[LWKT_NUM_POOL_TOKENS];
94 struct spinlock tok_debug_spin = SPINLOCK_INITIALIZER(&tok_debug_spin,
95 "tok_debug_spin");
97 #define TOKEN_STRING "REF=%p TOK=%p TD=%p"
98 #define TOKEN_ARGS lwkt_tokref_t ref, lwkt_token_t tok, struct thread *td
99 #define CONTENDED_STRING TOKEN_STRING " (contention started)"
100 #define UNCONTENDED_STRING TOKEN_STRING " (contention stopped)"
101 #if !defined(KTR_TOKENS)
102 #define KTR_TOKENS KTR_ALL
103 #endif
105 KTR_INFO_MASTER(tokens);
106 KTR_INFO(KTR_TOKENS, tokens, fail, 0, TOKEN_STRING, TOKEN_ARGS);
107 KTR_INFO(KTR_TOKENS, tokens, succ, 1, TOKEN_STRING, TOKEN_ARGS);
108 #if 0
109 KTR_INFO(KTR_TOKENS, tokens, release, 2, TOKEN_STRING, TOKEN_ARGS);
110 KTR_INFO(KTR_TOKENS, tokens, remote, 3, TOKEN_STRING, TOKEN_ARGS);
111 KTR_INFO(KTR_TOKENS, tokens, reqremote, 4, TOKEN_STRING, TOKEN_ARGS);
112 KTR_INFO(KTR_TOKENS, tokens, reqfail, 5, TOKEN_STRING, TOKEN_ARGS);
113 KTR_INFO(KTR_TOKENS, tokens, drain, 6, TOKEN_STRING, TOKEN_ARGS);
114 KTR_INFO(KTR_TOKENS, tokens, contention_start, 7, CONTENDED_STRING, TOKEN_ARGS);
115 KTR_INFO(KTR_TOKENS, tokens, contention_stop, 7, UNCONTENDED_STRING, TOKEN_ARGS);
116 #endif
118 #define logtoken(name, ref) \
119 KTR_LOG(tokens_ ## name, ref, ref->tr_tok, curthread)
122 * Global tokens. These replace the MP lock for major subsystem locking.
123 * These tokens are initially used to lockup both global and individual
124 * operations.
126 * Once individual structures get their own locks these tokens are used
127 * only to protect global lists & other variables and to interlock
128 * allocations and teardowns and such.
130 * The UP initializer causes token acquisition to also acquire the MP lock
131 * for maximum compatibility. The feature may be enabled and disabled at
132 * any time, the MP state is copied to the tokref when the token is acquired
133 * and will not race against sysctl changes.
135 struct lwkt_token mp_token = LWKT_TOKEN_INITIALIZER(mp_token);
136 struct lwkt_token pmap_token = LWKT_TOKEN_INITIALIZER(pmap_token);
137 struct lwkt_token dev_token = LWKT_TOKEN_INITIALIZER(dev_token);
138 struct lwkt_token vm_token = LWKT_TOKEN_INITIALIZER(vm_token);
139 struct lwkt_token vmspace_token = LWKT_TOKEN_INITIALIZER(vmspace_token);
140 struct lwkt_token kvm_token = LWKT_TOKEN_INITIALIZER(kvm_token);
141 struct lwkt_token sigio_token = LWKT_TOKEN_INITIALIZER(sigio_token);
142 struct lwkt_token tty_token = LWKT_TOKEN_INITIALIZER(tty_token);
143 struct lwkt_token vnode_token = LWKT_TOKEN_INITIALIZER(vnode_token);
146 * Exponential backoff (exclusive tokens) and TSC windowing (shared tokens)
147 * parameters. Remember that tokens backoff to the scheduler, large values
148 * not recommended.
150 static int token_backoff_max __cachealign = 4096;
151 SYSCTL_INT(_lwkt, OID_AUTO, token_backoff_max, CTLFLAG_RW,
152 &token_backoff_max, 0, "Tokens exponential backoff");
153 static int token_window_shift __cachealign = 8;
154 SYSCTL_INT(_lwkt, OID_AUTO, token_window_shift, CTLFLAG_RW,
155 &token_window_shift, 0, "Tokens TSC windowing shift");
158 * The collision count is bumped every time the LWKT scheduler fails
159 * to acquire needed tokens in addition to a normal lwkt_gettoken()
160 * stall.
162 SYSCTL_LONG(_lwkt, OID_AUTO, mp_collisions, CTLFLAG_RW,
163 &mp_token.t_collisions, 0, "Collision counter of mp_token");
164 SYSCTL_LONG(_lwkt, OID_AUTO, pmap_collisions, CTLFLAG_RW,
165 &pmap_token.t_collisions, 0, "Collision counter of pmap_token");
166 SYSCTL_LONG(_lwkt, OID_AUTO, dev_collisions, CTLFLAG_RW,
167 &dev_token.t_collisions, 0, "Collision counter of dev_token");
168 SYSCTL_LONG(_lwkt, OID_AUTO, vm_collisions, CTLFLAG_RW,
169 &vm_token.t_collisions, 0, "Collision counter of vm_token");
170 SYSCTL_LONG(_lwkt, OID_AUTO, vmspace_collisions, CTLFLAG_RW,
171 &vmspace_token.t_collisions, 0, "Collision counter of vmspace_token");
172 SYSCTL_LONG(_lwkt, OID_AUTO, kvm_collisions, CTLFLAG_RW,
173 &kvm_token.t_collisions, 0, "Collision counter of kvm_token");
174 SYSCTL_LONG(_lwkt, OID_AUTO, sigio_collisions, CTLFLAG_RW,
175 &sigio_token.t_collisions, 0, "Collision counter of sigio_token");
176 SYSCTL_LONG(_lwkt, OID_AUTO, tty_collisions, CTLFLAG_RW,
177 &tty_token.t_collisions, 0, "Collision counter of tty_token");
178 SYSCTL_LONG(_lwkt, OID_AUTO, vnode_collisions, CTLFLAG_RW,
179 &vnode_token.t_collisions, 0, "Collision counter of vnode_token");
181 int tokens_debug_output;
182 SYSCTL_INT(_lwkt, OID_AUTO, tokens_debug_output, CTLFLAG_RW,
183 &tokens_debug_output, 0, "Generate stack trace N times");
185 static int _lwkt_getalltokens_sorted(thread_t td);
188 * Acquire the initial mplock
190 * (low level boot only)
192 void
193 cpu_get_initial_mplock(void)
195 KKASSERT(mp_token.t_ref == NULL);
196 if (lwkt_trytoken(&mp_token) == FALSE)
197 panic("cpu_get_initial_mplock");
201 * Return a pool token given an address. Use a prime number to reduce
202 * overlaps.
204 static __inline
205 lwkt_token_t
206 _lwkt_token_pool_lookup(void *ptr)
208 uint32_t i;
210 i = (uint32_t)(uintptr_t)ptr % LWKT_NUM_POOL_TOKENS;
211 return (&pool_tokens[i].token);
215 * Initialize a tokref_t prior to making it visible in the thread's
216 * token array.
218 static __inline
219 void
220 _lwkt_tokref_init(lwkt_tokref_t ref, lwkt_token_t tok, thread_t td, long excl)
222 ref->tr_tok = tok;
223 ref->tr_count = excl;
224 ref->tr_owner = td;
228 * Attempt to acquire a shared or exclusive token. Returns TRUE on success,
229 * FALSE on failure.
231 * If TOK_EXCLUSIVE is set in mode we are attempting to get an exclusive
232 * token, otherwise are attempting to get a shared token.
234 * If TOK_EXCLREQ is set in mode this is a blocking operation, otherwise
235 * it is a non-blocking operation (for both exclusive or shared acquisions).
237 static __inline
239 _lwkt_trytokref(lwkt_tokref_t ref, thread_t td, long mode)
241 lwkt_token_t tok;
242 lwkt_tokref_t oref;
243 long count;
245 tok = ref->tr_tok;
246 KASSERT(((mode & TOK_EXCLREQ) == 0 || /* non blocking */
247 td->td_gd->gd_intr_nesting_level == 0 ||
248 panic_cpu_gd == mycpu),
249 ("Attempt to acquire token %p not already "
250 "held in hard code section", tok));
252 if (mode & TOK_EXCLUSIVE) {
254 * Attempt to get an exclusive token
256 count = tok->t_count;
258 for (;;) {
259 oref = tok->t_ref; /* can be NULL */
260 cpu_ccfence();
261 if ((count & ~TOK_EXCLREQ) == 0) {
263 * It is possible to get the exclusive bit.
264 * We must clear TOK_EXCLREQ on successful
265 * acquisition.
267 if (atomic_fcmpset_long(&tok->t_count, &count,
268 (count & ~TOK_EXCLREQ) |
269 TOK_EXCLUSIVE)) {
270 KKASSERT(tok->t_ref == NULL);
271 tok->t_ref = ref;
272 return TRUE;
274 /* retry */
275 } else if ((count & TOK_EXCLUSIVE) &&
276 oref >= &td->td_toks_base &&
277 oref < td->td_toks_stop) {
279 * Our thread already holds the exclusive
280 * bit, we treat this tokref as a shared
281 * token (sorta) to make the token release
282 * code easier. Treating this as a shared
283 * token allows us to simply increment the
284 * count field.
286 * NOTE: oref cannot race above if it
287 * happens to be ours, so we're good.
288 * But we must still have a stable
289 * variable for both parts of the
290 * comparison.
292 * NOTE: Since we already have an exclusive
293 * lock and don't need to check EXCLREQ
294 * we can just use an atomic_add here
296 atomic_add_long(&tok->t_count, TOK_INCR);
297 ref->tr_count &= ~TOK_EXCLUSIVE;
298 return TRUE;
299 } else if ((mode & TOK_EXCLREQ) &&
300 (count & TOK_EXCLREQ) == 0) {
302 * Unable to get the exclusive bit but being
303 * asked to set the exclusive-request bit.
304 * Since we are going to retry anyway just
305 * set the bit unconditionally.
307 atomic_set_long(&tok->t_count, TOK_EXCLREQ);
308 return FALSE;
309 } else {
311 * Unable to get the exclusive bit and not
312 * being asked to set the exclusive-request
313 * (aka lwkt_trytoken()), or EXCLREQ was
314 * already set.
316 cpu_pause();
317 return FALSE;
319 /* retry */
321 } else {
323 * Attempt to get a shared token. Note that TOK_EXCLREQ
324 * for shared tokens simply means the caller intends to
325 * block. We never actually set the bit in tok->t_count.
327 * Due to the token's no-deadlock guarantee, and complications
328 * created by the sorted reacquisition code, we can only
329 * give exclusive requests priority over shared requests
330 * in situations where the thread holds only one token.
332 count = tok->t_count;
334 for (;;) {
335 oref = tok->t_ref; /* can be NULL */
336 cpu_ccfence();
337 if ((count & (TOK_EXCLUSIVE|mode)) == 0 ||
338 ((count & TOK_EXCLUSIVE) == 0 &&
339 td->td_toks_stop != &td->td_toks_base + 1)
342 * It may be possible to get the token shared.
344 if ((atomic_fetchadd_long(&tok->t_count, TOK_INCR) & TOK_EXCLUSIVE) == 0) {
345 return TRUE;
347 count = atomic_fetchadd_long(&tok->t_count,
348 -TOK_INCR);
349 count -= TOK_INCR;
350 /* retry */
351 } else if ((count & TOK_EXCLUSIVE) &&
352 oref >= &td->td_toks_base &&
353 oref < td->td_toks_stop) {
355 * We own the exclusive bit on the token so
356 * we can in fact also get it shared.
358 atomic_add_long(&tok->t_count, TOK_INCR);
359 return TRUE;
360 } else {
362 * We failed to get the token shared
364 return FALSE;
366 /* retry */
371 static __inline
373 _lwkt_trytokref_spin(lwkt_tokref_t ref, thread_t td, long mode)
375 if (_lwkt_trytokref(ref, td, mode))
376 return TRUE;
378 if (mode & TOK_EXCLUSIVE) {
380 * Contested exclusive token, use exponential backoff
381 * algorithm.
383 long expbackoff;
384 long loop;
386 expbackoff = 0;
387 while (expbackoff < 6 + token_backoff_max) {
388 expbackoff = (expbackoff + 1) * 3 / 2;
389 if ((rdtsc() >> token_window_shift) % ncpus != mycpuid) {
390 for (loop = expbackoff; loop; --loop)
391 cpu_pause();
393 if (_lwkt_trytokref(ref, td, mode))
394 return TRUE;
396 } else {
398 * Contested shared token, use TSC windowing. Note that
399 * exclusive tokens have priority over shared tokens only
400 * for the first token.
402 if ((rdtsc() >> token_window_shift) % ncpus == mycpuid) {
403 if (_lwkt_trytokref(ref, td, mode & ~TOK_EXCLREQ))
404 return TRUE;
405 } else {
406 if (_lwkt_trytokref(ref, td, mode))
407 return TRUE;
411 ++mycpu->gd_cnt.v_lock_colls;
413 return FALSE;
417 * Release a token that we hold.
419 * Since tokens are polled, we don't have to deal with wakeups and releasing
420 * is really easy.
422 static __inline
423 void
424 _lwkt_reltokref(lwkt_tokref_t ref, thread_t td)
426 lwkt_token_t tok;
427 long count;
429 tok = ref->tr_tok;
430 if (tok->t_ref == ref) {
432 * We are an exclusive holder. We must clear tr_ref
433 * before we clear the TOK_EXCLUSIVE bit. If we are
434 * unable to clear the bit we must restore
435 * tok->t_ref.
437 #if 0
438 KKASSERT(count & TOK_EXCLUSIVE);
439 #endif
440 tok->t_ref = NULL;
441 atomic_clear_long(&tok->t_count, TOK_EXCLUSIVE);
442 } else {
444 * We are a shared holder
446 count = atomic_fetchadd_long(&tok->t_count, -TOK_INCR);
447 KKASSERT(count & TOK_COUNTMASK); /* count prior */
452 * Obtain all the tokens required by the specified thread on the current
453 * cpu, return 0 on failure and non-zero on success. If a failure occurs
454 * any partially acquired tokens will be released prior to return.
456 * lwkt_getalltokens is called by the LWKT scheduler to re-acquire all
457 * tokens that the thread had to release when it switched away.
459 * If spinning is non-zero this function acquires the tokens in a particular
460 * order to deal with potential deadlocks. We simply use address order for
461 * the case.
463 * Called from a critical section.
466 lwkt_getalltokens(thread_t td, int spinning)
468 lwkt_tokref_t scan;
469 lwkt_token_t tok;
471 if (spinning)
472 return(_lwkt_getalltokens_sorted(td));
475 * Acquire tokens in forward order, assign or validate tok->t_ref.
477 for (scan = &td->td_toks_base; scan < td->td_toks_stop; ++scan) {
478 tok = scan->tr_tok;
479 for (;;) {
481 * Only try really hard on the last token
483 if (scan == td->td_toks_stop - 1) {
484 if (_lwkt_trytokref_spin(scan, td, scan->tr_count))
485 break;
486 } else {
487 if (_lwkt_trytokref(scan, td, scan->tr_count))
488 break;
492 * Otherwise we failed to acquire all the tokens.
493 * Release whatever we did get.
495 KASSERT(tok->t_desc,
496 ("token %p is not initialized", tok));
497 td->td_gd->gd_cnt.v_lock_name[0] = 't';
498 strncpy(td->td_gd->gd_cnt.v_lock_name + 1,
499 tok->t_desc,
500 sizeof(td->td_gd->gd_cnt.v_lock_name) - 2);
501 if (lwkt_sched_debug > 0) {
502 --lwkt_sched_debug;
503 kprintf("toka %p %s %s\n",
504 tok, tok->t_desc, td->td_comm);
506 td->td_wmesg = tok->t_desc;
507 ++tok->t_collisions;
508 while (--scan >= &td->td_toks_base)
509 _lwkt_reltokref(scan, td);
510 return(FALSE);
513 return (TRUE);
517 * Release all tokens owned by the specified thread on the current cpu.
519 * This code is really simple. Even in cases where we own all the tokens
520 * note that t_ref may not match the scan for recursively held tokens which
521 * are held deeper in the stack, or for the case where a lwkt_getalltokens()
522 * failed.
524 * Tokens are released in reverse order to reduce chasing race failures.
526 * Called from a critical section.
528 void
529 lwkt_relalltokens(thread_t td)
531 lwkt_tokref_t scan;
534 * Weird order is to try to avoid a panic loop
536 if (td->td_toks_have) {
537 scan = td->td_toks_have;
538 td->td_toks_have = NULL;
539 } else {
540 scan = td->td_toks_stop;
542 while (--scan >= &td->td_toks_base)
543 _lwkt_reltokref(scan, td);
547 * This is the decontention version of lwkt_getalltokens(). The tokens are
548 * acquired in address-sorted order to deal with any deadlocks. Ultimately
549 * token failures will spin into the scheduler and get here.
551 * Called from critical section
553 static
555 _lwkt_getalltokens_sorted(thread_t td)
557 lwkt_tokref_t sort_array[LWKT_MAXTOKENS];
558 lwkt_tokref_t scan;
559 lwkt_token_t tok;
560 int i;
561 int j;
562 int n;
565 * Sort the token array. Yah yah, I know this isn't fun.
567 * NOTE: Recursively acquired tokens are ordered the same as in the
568 * td_toks_array so we can always get the earliest one first.
569 * This is particularly important when a token is acquired
570 * exclusively multiple times, as only the first acquisition
571 * is treated as an exclusive token.
573 i = 0;
574 scan = &td->td_toks_base;
575 while (scan < td->td_toks_stop) {
576 for (j = 0; j < i; ++j) {
577 if (scan->tr_tok < sort_array[j]->tr_tok)
578 break;
580 if (j != i) {
581 bcopy(sort_array + j, sort_array + j + 1,
582 (i - j) * sizeof(lwkt_tokref_t));
584 sort_array[j] = scan;
585 ++scan;
586 ++i;
588 n = i;
591 * Acquire tokens in forward order, assign or validate tok->t_ref.
593 for (i = 0; i < n; ++i) {
594 scan = sort_array[i];
595 tok = scan->tr_tok;
596 for (;;) {
598 * Only try really hard on the last token
600 if (scan == td->td_toks_stop - 1) {
601 if (_lwkt_trytokref_spin(scan, td, scan->tr_count))
602 break;
603 } else {
604 if (_lwkt_trytokref(scan, td, scan->tr_count))
605 break;
609 * Otherwise we failed to acquire all the tokens.
610 * Release whatever we did get.
612 td->td_gd->gd_cnt.v_lock_name[0] = 't';
613 strncpy(td->td_gd->gd_cnt.v_lock_name + 1,
614 tok->t_desc,
615 sizeof(td->td_gd->gd_cnt.v_lock_name) - 2);
616 if (lwkt_sched_debug > 0) {
617 --lwkt_sched_debug;
618 kprintf("tokb %p %s %s\n",
619 tok, tok->t_desc, td->td_comm);
621 td->td_wmesg = tok->t_desc;
622 ++tok->t_collisions;
623 while (--i >= 0) {
624 scan = sort_array[i];
625 _lwkt_reltokref(scan, td);
627 return(FALSE);
632 * We were successful, there is no need for another core to signal
633 * us.
635 return (TRUE);
639 * Get a serializing token. This routine can block.
641 void
642 lwkt_gettoken(lwkt_token_t tok)
644 thread_t td = curthread;
645 lwkt_tokref_t ref;
647 ref = td->td_toks_stop;
648 KKASSERT(ref < &td->td_toks_end);
649 ++td->td_toks_stop;
650 cpu_ccfence();
651 _lwkt_tokref_init(ref, tok, td, TOK_EXCLUSIVE|TOK_EXCLREQ);
653 #ifdef DEBUG_LOCKS
655 * Taking an exclusive token after holding it shared will
656 * livelock. Scan for that case and assert.
658 lwkt_tokref_t tk;
659 int found = 0;
660 for (tk = &td->td_toks_base; tk < ref; tk++) {
661 if (tk->tr_tok != tok)
662 continue;
664 found++;
665 if (tk->tr_count & TOK_EXCLUSIVE)
666 goto good;
668 /* We found only shared instances of this token if found >0 here */
669 KASSERT((found == 0), ("Token %p s/x livelock", tok));
670 good:
671 #endif
673 if (_lwkt_trytokref_spin(ref, td, TOK_EXCLUSIVE|TOK_EXCLREQ))
674 return;
677 * Give up running if we can't acquire the token right now.
679 * Since the tokref is already active the scheduler now
680 * takes care of acquisition, so we need only call
681 * lwkt_switch().
683 * Since we failed this was not a recursive token so upon
684 * return tr_tok->t_ref should be assigned to this specific
685 * ref.
687 td->td_wmesg = tok->t_desc;
688 ++tok->t_collisions;
689 logtoken(fail, ref);
690 td->td_toks_have = td->td_toks_stop - 1;
692 if (tokens_debug_output > 0) {
693 --tokens_debug_output;
694 spin_lock(&tok_debug_spin);
695 kprintf("Excl Token thread %p %s %s\n",
696 td, tok->t_desc, td->td_comm);
697 print_backtrace(6);
698 kprintf("\n");
699 spin_unlock(&tok_debug_spin);
702 atomic_set_int(&td->td_mpflags, TDF_MP_DIDYIELD);
703 lwkt_switch();
704 logtoken(succ, ref);
705 KKASSERT(tok->t_ref == ref);
709 * Similar to gettoken but we acquire a shared token instead of an exclusive
710 * token.
712 void
713 lwkt_gettoken_shared(lwkt_token_t tok)
715 thread_t td = curthread;
716 lwkt_tokref_t ref;
718 ref = td->td_toks_stop;
719 KKASSERT(ref < &td->td_toks_end);
720 ++td->td_toks_stop;
721 cpu_ccfence();
722 _lwkt_tokref_init(ref, tok, td, TOK_EXCLREQ);
724 #ifdef DEBUG_LOCKS
726 * Taking a pool token in shared mode is a bad idea; other
727 * addresses deeper in the call stack may hash to the same pool
728 * token and you may end up with an exclusive-shared livelock.
729 * Warn in this condition.
731 if ((tok >= &pool_tokens[0].token) &&
732 (tok < &pool_tokens[LWKT_NUM_POOL_TOKENS].token))
733 kprintf("Warning! Taking pool token %p in shared mode\n", tok);
734 #endif
737 if (_lwkt_trytokref_spin(ref, td, TOK_EXCLREQ))
738 return;
741 * Give up running if we can't acquire the token right now.
743 * Since the tokref is already active the scheduler now
744 * takes care of acquisition, so we need only call
745 * lwkt_switch().
747 * Since we failed this was not a recursive token so upon
748 * return tr_tok->t_ref should be assigned to this specific
749 * ref.
751 td->td_wmesg = tok->t_desc;
752 ++tok->t_collisions;
753 logtoken(fail, ref);
754 td->td_toks_have = td->td_toks_stop - 1;
756 if (tokens_debug_output > 0) {
757 --tokens_debug_output;
758 spin_lock(&tok_debug_spin);
759 kprintf("Shar Token thread %p %s %s\n",
760 td, tok->t_desc, td->td_comm);
761 print_backtrace(6);
762 kprintf("\n");
763 spin_unlock(&tok_debug_spin);
766 atomic_set_int(&td->td_mpflags, TDF_MP_DIDYIELD);
767 lwkt_switch();
768 logtoken(succ, ref);
772 * Attempt to acquire a token, return TRUE on success, FALSE on failure.
774 * We setup the tokref in case we actually get the token (if we switch later
775 * it becomes mandatory so we set TOK_EXCLREQ), but we call trytokref without
776 * TOK_EXCLREQ in case we fail.
779 lwkt_trytoken(lwkt_token_t tok)
781 thread_t td = curthread;
782 lwkt_tokref_t ref;
784 ref = td->td_toks_stop;
785 KKASSERT(ref < &td->td_toks_end);
786 ++td->td_toks_stop;
787 cpu_ccfence();
788 _lwkt_tokref_init(ref, tok, td, TOK_EXCLUSIVE|TOK_EXCLREQ);
790 if (_lwkt_trytokref(ref, td, TOK_EXCLUSIVE))
791 return TRUE;
794 * Failed, unpend the request
796 cpu_ccfence();
797 --td->td_toks_stop;
798 ++tok->t_collisions;
799 return FALSE;
802 lwkt_token_t
803 lwkt_getpooltoken(void *ptr)
805 lwkt_token_t tok;
807 tok = _lwkt_token_pool_lookup(ptr);
808 lwkt_gettoken(tok);
809 return (tok);
813 * Release a serializing token.
815 * WARNING! All tokens must be released in reverse order. This will be
816 * asserted.
818 void
819 lwkt_reltoken(lwkt_token_t tok)
821 thread_t td = curthread;
822 lwkt_tokref_t ref;
825 * Remove ref from thread token list and assert that it matches
826 * the token passed in. Tokens must be released in reverse order.
828 ref = td->td_toks_stop - 1;
829 KKASSERT(ref >= &td->td_toks_base && ref->tr_tok == tok);
830 _lwkt_reltokref(ref, td);
831 cpu_sfence();
832 td->td_toks_stop = ref;
836 * It is faster for users of lwkt_getpooltoken() to use the returned
837 * token and just call lwkt_reltoken(), but for convenience we provide
838 * this function which looks the token up based on the ident.
840 void
841 lwkt_relpooltoken(void *ptr)
843 lwkt_token_t tok = _lwkt_token_pool_lookup(ptr);
844 lwkt_reltoken(tok);
848 * Return a count of the number of token refs the thread has to the
849 * specified token, whether it currently owns the token or not.
852 lwkt_cnttoken(lwkt_token_t tok, thread_t td)
854 lwkt_tokref_t scan;
855 int count = 0;
857 for (scan = &td->td_toks_base; scan < td->td_toks_stop; ++scan) {
858 if (scan->tr_tok == tok)
859 ++count;
861 return(count);
865 * Pool tokens are used to provide a type-stable serializing token
866 * pointer that does not race against disappearing data structures.
868 * This routine is called in early boot just after we setup the BSP's
869 * globaldata structure.
871 void
872 lwkt_token_pool_init(void)
874 int i;
876 for (i = 0; i < LWKT_NUM_POOL_TOKENS; ++i)
877 lwkt_token_init(&pool_tokens[i].token, "pool");
880 lwkt_token_t
881 lwkt_token_pool_lookup(void *ptr)
883 return (_lwkt_token_pool_lookup(ptr));
887 * Initialize a token.
889 void
890 lwkt_token_init(lwkt_token_t tok, const char *desc)
892 tok->t_count = 0;
893 tok->t_ref = NULL;
894 tok->t_collisions = 0;
895 tok->t_desc = desc;
898 void
899 lwkt_token_uninit(lwkt_token_t tok)
901 /* empty */
905 * Exchange the two most recent tokens on the tokref stack. This allows
906 * you to release a token out of order.
908 * We have to be careful about the case where the top two tokens are
909 * the same token. In this case tok->t_ref will point to the deeper
910 * ref and must remain pointing to the deeper ref. If we were to swap
911 * it the first release would clear the token even though a second
912 * ref is still present.
914 * Only exclusively held tokens contain a reference to the tokref which
915 * has to be flipped along with the swap.
917 void
918 lwkt_token_swap(void)
920 lwkt_tokref_t ref1, ref2;
921 lwkt_token_t tok1, tok2;
922 long count1, count2;
923 thread_t td = curthread;
925 crit_enter();
927 ref1 = td->td_toks_stop - 1;
928 ref2 = td->td_toks_stop - 2;
929 KKASSERT(ref1 >= &td->td_toks_base);
930 KKASSERT(ref2 >= &td->td_toks_base);
932 tok1 = ref1->tr_tok;
933 tok2 = ref2->tr_tok;
934 count1 = ref1->tr_count;
935 count2 = ref2->tr_count;
937 if (tok1 != tok2) {
938 ref1->tr_tok = tok2;
939 ref1->tr_count = count2;
940 ref2->tr_tok = tok1;
941 ref2->tr_count = count1;
942 if (tok1->t_ref == ref1)
943 tok1->t_ref = ref2;
944 if (tok2->t_ref == ref2)
945 tok2->t_ref = ref1;
948 crit_exit();
951 #ifdef DDB
952 DB_SHOW_COMMAND(tokens, db_tok_all)
954 struct lwkt_token *tok, **ptr;
955 struct lwkt_token *toklist[16] = {
956 &mp_token,
957 &pmap_token,
958 &dev_token,
959 &vm_token,
960 &vmspace_token,
961 &kvm_token,
962 &sigio_token,
963 &tty_token,
964 &vnode_token,
965 NULL
968 ptr = toklist;
969 for (tok = *ptr; tok; tok = *(++ptr)) {
970 db_printf("tok=%p tr_owner=%p t_colissions=%ld t_desc=%s\n", tok,
971 (tok->t_ref ? tok->t_ref->tr_owner : NULL),
972 tok->t_collisions, tok->t_desc);
975 #endif /* DDB */