1 /*
2 * Copyright (c) 2004 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:
10 *
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.
20 *
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.
33 */
34 /*
35 * Copyright (c) 1982, 1986, 1991, 1993
36 * The Regents of the University of California. All rights reserved.
37 * (c) UNIX System Laboratories, Inc.
38 * All or some portions of this file are derived from material licensed
39 * to the University of California by American Telephone and Telegraph
40 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
41 * the permission of UNIX System Laboratories, Inc.
42 *
43 * Redistribution and use in source and binary forms, with or without
44 * modification, are permitted provided that the following conditions
45 * are met:
46 * 1. Redistributions of source code must retain the above copyright
47 * notice, this list of conditions and the following disclaimer.
48 * 2. Redistributions in binary form must reproduce the above copyright
49 * notice, this list of conditions and the following disclaimer in the
50 * documentation and/or other materials provided with the distribution.
51 * 3. Neither the name of the University nor the names of its contributors
52 * may be used to endorse or promote products derived from this software
53 * without specific prior written permission.
54 *
55 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
56 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
57 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
58 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
59 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
60 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
61 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
62 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
63 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
64 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
65 * SUCH DAMAGE.
66 *
67 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
68 * $FreeBSD: src/sys/kern/kern_timeout.c,v 1.59.2.1 2001/11/13 18:24:52 archie Exp $
69 */
70 /*
71 * DRAGONFLY BGL STATUS
72 *
73 * All the API functions should be MP safe.
74 *
75 * The callback functions will be flagged as being MP safe if the
76 * timeout structure is initialized with callout_init_mp() instead of
77 * callout_init().
78 *
79 * The helper threads cannot be made preempt-capable until after we
80 * clean up all the uses of splsoftclock() and related interlocks (which
81 * require the related functions to be MP safe as well).
82 */
83 /*
84 * The callout mechanism is based on the work of Adam M. Costello and
85 * George Varghese, published in a technical report entitled "Redesigning
86 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
87 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
88 * used in this implementation was published by G. Varghese and T. Lauck in
89 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
90 * the Efficient Implementation of a Timer Facility" in the Proceedings of
91 * the 11th ACM Annual Symposium on Operating Systems Principles,
92 * Austin, Texas Nov 1987.
93 *
94 * The per-cpu augmentation was done by Matthew Dillon.
95 */
96
97 #include <sys/param.h>
98 #include <sys/systm.h>
99 #include <sys/callout.h>
100 #include <sys/kernel.h>
101 #include <sys/interrupt.h>
102 #include <sys/thread.h>
103
104 #include <sys/thread2.h>
105 #include <sys/mplock2.h>
106
107 #ifndef MAX_SOFTCLOCK_STEPS
108 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
109 #endif
110
111
112 struct softclock_pcpu {
113 struct callout_tailq *callwheel;
114 struct callout * volatile next;
115 struct callout *running;/* currently running callout */
116 int softticks; /* softticks index */
117 int curticks; /* per-cpu ticks counter */
118 int isrunning;
119 struct thread thread;
120
121 };
122
123 typedef struct softclock_pcpu *softclock_pcpu_t;
124
125 /*
126 * TODO:
127 * allocate more timeout table slots when table overflows.
128 */
129 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures");
130 static int callwheelsize;
131 static int callwheelmask;
132 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU];
133
134 static void softclock_handler(void *arg);
135 static void slotimer_callback(void *arg);
136
137 static void
138 swi_softclock_setup(void *arg)
139 {
140 int cpu;
141 int i;
142 int target;
143
144 /*
145 * Figure out how large a callwheel we need. It must be a power of 2.
146 *
147 * ncallout is primarily based on available memory, don't explode
148 * the allocations if the system has a lot of cpus.
149 */
150 target = ncallout / ncpus + 16;
151
152 callwheelsize = 1;
153 while (callwheelsize < target)
154 callwheelsize <<= 1;
155 callwheelmask = callwheelsize - 1;
156
157 /*
158 * Initialize per-cpu data structures.
159 */
160 for (cpu = 0; cpu < ncpus; ++cpu) {
161 softclock_pcpu_t sc;
162
163 sc = &softclock_pcpu_ary[cpu];
164
165 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize,
166 M_CALLOUT, M_WAITOK|M_ZERO);
167 for (i = 0; i < callwheelsize; ++i)
168 TAILQ_INIT(&sc->callwheel[i]);
169
170 /*
171 * Mark the softclock handler as being an interrupt thread
172 * even though it really isn't, but do not allow it to
173 * preempt other threads (do not assign td_preemptable).
174 *
175 * Kernel code now assumes that callouts do not preempt
176 * the cpu they were scheduled on.
177 */
178 lwkt_create(softclock_handler, sc, NULL,
179 &sc->thread, TDF_NOSTART | TDF_INTTHREAD,
180 cpu, "softclock %d", cpu);
181 }
182 }
183
184 /*
185 * Must occur after ncpus has been initialized.
186 */
187 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND,
188 swi_softclock_setup, NULL);
189
190 /*
191 * This routine is called from the hardclock() (basically a FASTint/IPI) on
192 * each cpu in the system. sc->curticks is this cpu's notion of the timebase.
193 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where
194 * the callwheel is currently indexed.
195 *
196 * WARNING! The MP lock is not necessarily held on call, nor can it be
197 * safely obtained.
198 *
199 * sc->softticks is adjusted by either this routine or our helper thread
200 * depending on whether the helper thread is running or not.
201 */
202 void
203 hardclock_softtick(globaldata_t gd)
204 {
205 softclock_pcpu_t sc;
206
207 sc = &softclock_pcpu_ary[gd->gd_cpuid];
208 ++sc->curticks;
209 if (sc->isrunning)
210 return;
211 if (sc->softticks == sc->curticks) {
212 /*
213 * in sync, only wakeup the thread if there is something to
214 * do.
215 */
216 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask]))
217 {
218 sc->isrunning = 1;
219 lwkt_schedule(&sc->thread);
220 } else {
221 ++sc->softticks;
222 }
223 } else {
224 /*
225 * out of sync, wakeup the thread unconditionally so it can
226 * catch up.
227 */
228 sc->isrunning = 1;
229 lwkt_schedule(&sc->thread);
230 }
231 }
232
233 /*
234 * This procedure is the main loop of our per-cpu helper thread. The
235 * sc->isrunning flag prevents us from racing hardclock_softtick() and
236 * a critical section is sufficient to interlock sc->curticks and protect
237 * us from remote IPI's / list removal.
238 *
239 * The thread starts with the MP lock released and not in a critical
240 * section. The loop itself is MP safe while individual callbacks
241 * may or may not be, so we obtain or release the MP lock as appropriate.
242 */
243 static void
244 softclock_handler(void *arg)
245 {
246 softclock_pcpu_t sc;
247 struct callout *c;
248 struct callout_tailq *bucket;
249 struct callout slotimer;
250 void (*c_func)(void *);
251 void *c_arg;
252 int mpsafe = 1;
253
254 /*
255 * Setup pcpu slow clocks which we want to run from the callout
256 * thread.
257 */
258 callout_init_mp(&slotimer);
259 callout_reset(&slotimer, hz * 10, slotimer_callback, &slotimer);
260
261 /*
262 * Run the callout thread at the same priority as other kernel
263 * threads so it can be round-robined.
264 */
265 /*lwkt_setpri_self(TDPRI_SOFT_NORM);*/
266
267 sc = arg;
268 crit_enter();
269 loop:
270 while (sc->softticks != (int)(sc->curticks + 1)) {
271 bucket = &sc->callwheel[sc->softticks & callwheelmask];
272
273 for (c = TAILQ_FIRST(bucket); c; c = sc->next) {
274 if (c->c_time != sc->softticks) {
275 sc->next = TAILQ_NEXT(c, c_links.tqe);
276 continue;
277 }
278 if (c->c_flags & CALLOUT_MPSAFE) {
279 if (mpsafe == 0) {
280 mpsafe = 1;
281 rel_mplock();
282 }
283 } else {
284 /*
285 * The request might be removed while we
286 * are waiting to get the MP lock. If it
287 * was removed sc->next will point to the
288 * next valid request or NULL, loop up.
289 */
290 if (mpsafe) {
291 mpsafe = 0;
292 sc->next = c;
293 get_mplock();
294 if (c != sc->next)
295 continue;
296 }
297 }
298 sc->next = TAILQ_NEXT(c, c_links.tqe);
299 TAILQ_REMOVE(bucket, c, c_links.tqe);
300
301 sc->running = c;
302 c_func = c->c_func;
303 c_arg = c->c_arg;
304 c->c_func = NULL;
305 KKASSERT(c->c_flags & CALLOUT_DID_INIT);
306 c->c_flags &= ~CALLOUT_PENDING;
307 crit_exit();
308 c_func(c_arg);
309 crit_enter();
310 sc->running = NULL;
311 /* NOTE: list may have changed */
312 }
313 ++sc->softticks;
314 }
315
316 /*
317 * Don't leave us holding the MP lock when we deschedule ourselves.
318 */
319 if (mpsafe == 0) {
320 mpsafe = 1;
321 rel_mplock();
322 }
323 sc->isrunning = 0;
324 lwkt_deschedule_self(&sc->thread); /* == curthread */
325 lwkt_switch();
326 goto loop;
327 /* NOT REACHED */
328 }
329
330 /*
331 * A very slow system cleanup timer (10 second interval),
332 * per-cpu.
333 */
334 void
335 slotimer_callback(void *arg)
336 {
337 struct callout *c = arg;
338
339 slab_cleanup();
340 callout_reset(c, hz * 10, slotimer_callback, c);
341 }
342
343 /*
344 * New interface; clients allocate their own callout structures.
345 *
346 * callout_reset() - establish or change a timeout
347 * callout_stop() - disestablish a timeout
348 * callout_init() - initialize a callout structure so that it can
349 * safely be passed to callout_reset() and callout_stop()
350 * callout_init_mp() - same but any installed functions must be MP safe.
351 *
352 * <sys/callout.h> defines three convenience macros:
353 *
354 * callout_active() - returns truth if callout has not been serviced
355 * callout_pending() - returns truth if callout is still waiting for timeout
356 * callout_deactivate() - marks the callout as having been serviced
357 */
358
359 /*
360 * Start or restart a timeout. Install the callout structure in the
361 * callwheel. Callers may legally pass any value, even if 0 or negative,
362 * but since the sc->curticks index may have already been processed a
363 * minimum timeout of 1 tick will be enforced.
364 *
365 * The callout is installed on and will be processed on the current cpu's
366 * callout wheel.
367 *
368 * WARNING! This function may be called from any cpu but the caller must
369 * serialize callout_stop() and callout_reset() calls on the passed
370 * structure regardless of cpu.
371 */
372 void
373 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
374 void *arg)
375 {
376 softclock_pcpu_t sc;
377 globaldata_t gd;
378
379 #ifdef INVARIANTS
380 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
381 callout_init(c);
382 kprintf(
383 "callout_reset(%p) from %p: callout was not initialized\n",
384 c, ((int **)&c)[-1]);
385 print_backtrace(-1);
386 }
387 #endif
388 gd = mycpu;
389 sc = &softclock_pcpu_ary[gd->gd_cpuid];
390 crit_enter_gd(gd);
391
392 if (c->c_flags & CALLOUT_ACTIVE)
393 callout_stop(c);
394
395 if (to_ticks <= 0)
396 to_ticks = 1;
397
398 c->c_arg = arg;
399 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
400 c->c_func = ftn;
401 c->c_time = sc->curticks + to_ticks;
402 c->c_gd = gd;
403
404 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask],
405 c, c_links.tqe);
406 crit_exit_gd(gd);
407 }
408
409 struct callout_remote_arg {
410 struct callout *c;
411 void (*ftn)(void *);
412 void *arg;
413 int to_ticks;
414 };
415
416 static void
417 callout_reset_ipi(void *arg)
418 {
419 struct callout_remote_arg *rmt = arg;
420
421 callout_reset(rmt->c, rmt->to_ticks, rmt->ftn, rmt->arg);
422 }
423
424 void
425 callout_reset_bycpu(struct callout *c, int to_ticks, void (*ftn)(void *),
426 void *arg, int cpuid)
427 {
428 KASSERT(cpuid >= 0 && cpuid < ncpus, ("invalid cpuid %d", cpuid));
429
430 if (cpuid == mycpuid) {
431 callout_reset(c, to_ticks, ftn, arg);
432 } else {
433 struct globaldata *target_gd;
434 struct callout_remote_arg rmt;
435 int seq;
436
437 rmt.c = c;
438 rmt.ftn = ftn;
439 rmt.arg = arg;
440 rmt.to_ticks = to_ticks;
441
442 target_gd = globaldata_find(cpuid);
443
444 seq = lwkt_send_ipiq(target_gd, callout_reset_ipi, &rmt);
445 lwkt_wait_ipiq(target_gd, seq);
446 }
447 }
448
449 /*
450 * Stop a running timer. WARNING! If called on a cpu other then the one
451 * the callout was started on this function will liveloop on its IPI to
452 * the target cpu to process the request. It is possible for the callout
453 * to execute in that case.
454 *
455 * WARNING! This function may be called from any cpu but the caller must
456 * serialize callout_stop() and callout_reset() calls on the passed
457 * structure regardless of cpu.
458 *
459 * WARNING! This routine may be called from an IPI
460 *
461 * WARNING! This function can return while it's c_func is still running
462 * in the callout thread, a secondary check may be needed.
463 * Use callout_stop_sync() to wait for any callout function to
464 * complete before returning, being sure that no deadlock is
465 * possible if you do.
466 */
467 int
468 callout_stop(struct callout *c)
469 {
470 globaldata_t gd = mycpu;
471 globaldata_t tgd;
472 softclock_pcpu_t sc;
473
474 #ifdef INVARIANTS
475 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
476 callout_init(c);
477 kprintf(
478 "callout_stop(%p) from %p: callout was not initialized\n",
479 c, ((int **)&c)[-1]);
480 print_backtrace(-1);
481 }
482 #endif
483 crit_enter_gd(gd);
484
485 /*
486 * Don't attempt to delete a callout that's not on the queue. The
487 * callout may not have a cpu assigned to it. Callers do not have
488 * to be on the issuing cpu but must still serialize access to the
489 * callout structure.
490 *
491 * We are not cpu-localized here and cannot safely modify the
492 * flags field in the callout structure. Note that most of the
493 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
494 *
495 * If we race another cpu's dispatch of this callout it is possible
496 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
497 * will cause us to fall through and synchronize with the other
498 * cpu.
499 */
500 if ((c->c_flags & CALLOUT_PENDING) == 0) {
501 if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
502 crit_exit_gd(gd);
503 return (0);
504 }
505 if (c->c_gd == NULL || c->c_gd == gd) {
506 c->c_flags &= ~CALLOUT_ACTIVE;
507 crit_exit_gd(gd);
508 return (0);
509 }
510 }
511 if ((tgd = c->c_gd) != gd) {
512 /*
513 * If the callout is owned by a different CPU we have to
514 * execute the function synchronously on the target cpu.
515 */
516 int seq;
517
518 cpu_ccfence(); /* don't let tgd alias c_gd */
519 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
520 lwkt_wait_ipiq(tgd, seq);
521 } else {
522 /*
523 * If the callout is owned by the same CPU we can
524 * process it directly, but if we are racing our helper
525 * thread (sc->next), we have to adjust sc->next. The
526 * race is interlocked by a critical section.
527 */
528 sc = &softclock_pcpu_ary[gd->gd_cpuid];
529
530 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
531 if (sc->next == c)
532 sc->next = TAILQ_NEXT(c, c_links.tqe);
533
534 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
535 c, c_links.tqe);
536 c->c_func = NULL;
537 }
538 crit_exit_gd(gd);
539 return (1);
540 }
541
542 /*
543 * Issue a callout_stop() and ensure that any callout race completes
544 * before returning. Does NOT de-initialized the callout.
545 */
546 void
547 callout_stop_sync(struct callout *c)
548 {
549 softclock_pcpu_t sc;
550
551 while (c->c_flags & CALLOUT_DID_INIT) {
552 callout_stop(c);
553 if (c->c_gd) {
554 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
555 if (sc->running == c) {
556 while (sc->running == c)
557 tsleep(&sc->running, 0, "crace", 1);
558 }
559 }
560 if ((c->c_flags & (CALLOUT_PENDING | CALLOUT_ACTIVE)) == 0)
561 break;
562 kprintf("Warning: %s: callout race\n", curthread->td_comm);
563 }
564 }
565
566 /*
567 * Terminate a callout
568 *
569 * This function will stop any pending callout and also block while the
570 * callout's function is running. It should only be used in cases where
571 * no deadlock is possible (due to the callout function acquiring locks
572 * that the current caller of callout_terminate() already holds), when
573 * the caller is ready to destroy the callout structure.
574 *
575 * This function clears the CALLOUT_DID_INIT flag.
576 *
577 * lwkt_token locks are ok.
578 */
579 void
580 callout_terminate(struct callout *c)
581 {
582 softclock_pcpu_t sc;
583
584 if (c->c_flags & CALLOUT_DID_INIT) {
585 callout_stop(c);
586 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
587 if (sc->running == c) {
588 while (sc->running == c)
589 tsleep(&sc->running, 0, "crace", 1);
590 }
591 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
592 c->c_flags &= ~CALLOUT_DID_INIT;
593 }
594 }
595
596 /*
597 * Prepare a callout structure for use by callout_reset() and/or
598 * callout_stop(). The MP version of this routine requires that the callback
599 * function installed by callout_reset() be MP safe.
600 *
601 * The init functions can be called from any cpu and do not have to be
602 * called from the cpu that the timer will eventually run on.
603 */
604 void
605 callout_init(struct callout *c)
606 {
607 bzero(c, sizeof *c);
608 c->c_flags = CALLOUT_DID_INIT;
609 }
610
611 void
612 callout_init_mp(struct callout *c)
613 {
614 callout_init(c);
615 c->c_flags |= CALLOUT_MPSAFE;
616 }
Cache object: 4946960f4e8751d352c7e50f2f1f109a
|