kernel - Major signal path adjustments to fix races, tsleep race fixes, +more
[dragonfly.git] / sys / kern / kern_timeout.c
CommitLineData
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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/*
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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. All advertising materials mentioning features or use of this software
52 * must display the following acknowledgement:
53 * This product includes software developed by the University of
54 * California, Berkeley and its contributors.
55 * 4. Neither the name of the University nor the names of its contributors
56 * may be used to endorse or promote products derived from this software
57 * without specific prior written permission.
58 *
59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
69 * SUCH DAMAGE.
70 *
71 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
72 * $FreeBSD: src/sys/kern/kern_timeout.c,v 1.59.2.1 2001/11/13 18:24:52 archie Exp $
bb1a3ed4 73 * $DragonFly: src/sys/kern/kern_timeout.c,v 1.27 2007/11/14 18:27:52 swildner Exp $
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74 */
75/*
76 * DRAGONFLY BGL STATUS
77 *
78 * All the API functions should be MP safe.
79 *
80 * The callback functions will be flagged as being MP safe if the
81 * timeout structure is initialized with callout_init_mp() instead of
82 * callout_init().
83 *
84 * The helper threads cannot be made preempt-capable until after we
85 * clean up all the uses of splsoftclock() and related interlocks (which
86 * require the related functions to be MP safe as well).
87 */
88/*
89 * The callout mechanism is based on the work of Adam M. Costello and
90 * George Varghese, published in a technical report entitled "Redesigning
91 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
92 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
93 * used in this implementation was published by G. Varghese and T. Lauck in
94 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
95 * the Efficient Implementation of a Timer Facility" in the Proceedings of
96 * the 11th ACM Annual Symposium on Operating Systems Principles,
97 * Austin, Texas Nov 1987.
98 *
99 * The per-cpu augmentation was done by Matthew Dillon.
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100 */
101
102#include <sys/param.h>
103#include <sys/systm.h>
104#include <sys/callout.h>
105#include <sys/kernel.h>
ef0fdad1 106#include <sys/interrupt.h>
4b5f931b 107#include <sys/thread.h>
684a93c4 108
88c4d2f6 109#include <sys/thread2.h>
684a93c4 110#include <sys/mplock2.h>
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111
112#ifndef MAX_SOFTCLOCK_STEPS
113#define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
114#endif
115
116
117struct softclock_pcpu {
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118 struct callout_tailq *callwheel;
119 struct callout * volatile next;
b90e37ec 120 struct callout *running;/* currently running callout */
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121 int softticks; /* softticks index */
122 int curticks; /* per-cpu ticks counter */
123 int isrunning;
124 struct thread thread;
125
126};
127
128typedef struct softclock_pcpu *softclock_pcpu_t;
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129
130/*
131 * TODO:
132 * allocate more timeout table slots when table overflows.
133 */
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134static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures");
135static int callwheelsize;
136static int callwheelbits;
137static int callwheelmask;
138static struct softclock_pcpu softclock_pcpu_ary[MAXCPU];
139
140static void softclock_handler(void *arg);
141
142static void
143swi_softclock_setup(void *arg)
144{
145 int cpu;
146 int i;
984263bc 147
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148 /*
149 * Figure out how large a callwheel we need. It must be a power of 2.
150 */
151 callwheelsize = 1;
152 callwheelbits = 0;
153 while (callwheelsize < ncallout) {
154 callwheelsize <<= 1;
155 ++callwheelbits;
156 }
157 callwheelmask = callwheelsize - 1;
984263bc 158
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159 /*
160 * Initialize per-cpu data structures.
161 */
162 for (cpu = 0; cpu < ncpus; ++cpu) {
163 softclock_pcpu_t sc;
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164
165 sc = &softclock_pcpu_ary[cpu];
166
77652cad 167 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize,
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168 M_CALLOUT, M_WAITOK|M_ZERO);
169 for (i = 0; i < callwheelsize; ++i)
170 TAILQ_INIT(&sc->callwheel[i]);
171
92b561b7 172 /*
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173 * Mark the softclock handler as being an interrupt thread
174 * even though it really isn't, but do not allow it to
175 * preempt other threads (do not assign td_preemptable).
176 *
177 * Kernel code now assumes that callouts do not preempt
178 * the cpu they were scheduled on.
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179 */
180 lwkt_create(softclock_handler, sc, NULL,
4643740a 181 &sc->thread, TDF_NOSTART | TDF_INTTHREAD,
c9e9fb21 182 cpu, "softclock %d", cpu);
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183 }
184}
185
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186/*
187 * Must occur after ncpus has been initialized.
188 */
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189SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND,
190 swi_softclock_setup, NULL);
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191
192/*
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193 * This routine is called from the hardclock() (basically a FASTint/IPI) on
194 * each cpu in the system. sc->curticks is this cpu's notion of the timebase.
195 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where
196 * the callwheel is currently indexed.
197 *
198 * WARNING! The MP lock is not necessarily held on call, nor can it be
199 * safely obtained.
200 *
201 * sc->softticks is adjusted by either this routine or our helper thread
202 * depending on whether the helper thread is running or not.
984263bc 203 */
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204void
205hardclock_softtick(globaldata_t gd)
206{
207 softclock_pcpu_t sc;
208
209 sc = &softclock_pcpu_ary[gd->gd_cpuid];
210 ++sc->curticks;
211 if (sc->isrunning)
212 return;
213 if (sc->softticks == sc->curticks) {
214 /*
215 * in sync, only wakeup the thread if there is something to
216 * do.
217 */
218 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask]))
219 {
220 sc->isrunning = 1;
221 lwkt_schedule(&sc->thread);
222 } else {
223 ++sc->softticks;
224 }
225 } else {
226 /*
227 * out of sync, wakeup the thread unconditionally so it can
228 * catch up.
229 */
230 sc->isrunning = 1;
231 lwkt_schedule(&sc->thread);
232 }
233}
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234
235/*
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236 * This procedure is the main loop of our per-cpu helper thread. The
237 * sc->isrunning flag prevents us from racing hardclock_softtick() and
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238 * a critical section is sufficient to interlock sc->curticks and protect
239 * us from remote IPI's / list removal.
92b561b7 240 *
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241 * The thread starts with the MP lock released and not in a critical
242 * section. The loop itself is MP safe while individual callbacks
243 * may or may not be, so we obtain or release the MP lock as appropriate.
984263bc 244 */
ef0fdad1 245static void
92b561b7 246softclock_handler(void *arg)
984263bc 247{
92b561b7 248 softclock_pcpu_t sc;
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249 struct callout *c;
250 struct callout_tailq *bucket;
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251 void (*c_func)(void *);
252 void *c_arg;
92b561b7 253#ifdef SMP
c9e9fb21 254 int mpsafe = 1;
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255#endif
256
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257 /*
258 * Run the callout thread at the same priority as other kernel
259 * threads so it can be round-robined.
260 */
261 /*lwkt_setpri_self(TDPRI_SOFT_NORM);*/
abb6f10a 262
92b561b7 263 sc = arg;
88c4d2f6 264 crit_enter();
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265loop:
266 while (sc->softticks != (int)(sc->curticks + 1)) {
267 bucket = &sc->callwheel[sc->softticks & callwheelmask];
268
269 for (c = TAILQ_FIRST(bucket); c; c = sc->next) {
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270 if (c->c_time != sc->softticks) {
271 sc->next = TAILQ_NEXT(c, c_links.tqe);
92b561b7 272 continue;
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273 }
274#ifdef SMP
275 if (c->c_flags & CALLOUT_MPSAFE) {
276 if (mpsafe == 0) {
277 mpsafe = 1;
278 rel_mplock();
279 }
280 } else {
281 /*
282 * The request might be removed while we
283 * are waiting to get the MP lock. If it
284 * was removed sc->next will point to the
285 * next valid request or NULL, loop up.
286 */
287 if (mpsafe) {
288 mpsafe = 0;
289 sc->next = c;
290 get_mplock();
291 if (c != sc->next)
292 continue;
293 }
294 }
295#endif
296 sc->next = TAILQ_NEXT(c, c_links.tqe);
92b561b7 297 TAILQ_REMOVE(bucket, c, c_links.tqe);
4ac1a4cd 298
b90e37ec 299 sc->running = c;
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300 c_func = c->c_func;
301 c_arg = c->c_arg;
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302 c->c_func = NULL;
303 KKASSERT(c->c_flags & CALLOUT_DID_INIT);
7eb3b2ae 304 c->c_flags &= ~CALLOUT_PENDING;
92b561b7 305 crit_exit();
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306 c_func(c_arg);
307 crit_enter();
b90e37ec 308 sc->running = NULL;
92b561b7 309 /* NOTE: list may have changed */
984263bc 310 }
92b561b7 311 ++sc->softticks;
984263bc 312 }
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313 sc->isrunning = 0;
314 lwkt_deschedule_self(&sc->thread); /* == curthread */
315 lwkt_switch();
316 goto loop;
317 /* NOT REACHED */
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318}
319
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320/*
321 * New interface; clients allocate their own callout structures.
322 *
323 * callout_reset() - establish or change a timeout
324 * callout_stop() - disestablish a timeout
325 * callout_init() - initialize a callout structure so that it can
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326 * safely be passed to callout_reset() and callout_stop()
327 * callout_init_mp() - same but any installed functions must be MP safe.
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328 *
329 * <sys/callout.h> defines three convenience macros:
330 *
331 * callout_active() - returns truth if callout has not been serviced
332 * callout_pending() - returns truth if callout is still waiting for timeout
333 * callout_deactivate() - marks the callout as having been serviced
334 */
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335
336/*
337 * Start or restart a timeout. Install the callout structure in the
338 * callwheel. Callers may legally pass any value, even if 0 or negative,
339 * but since the sc->curticks index may have already been processed a
340 * minimum timeout of 1 tick will be enforced.
341 *
342 * The callout is installed on and will be processed on the current cpu's
343 * callout wheel.
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344 *
345 * WARNING! This function may be called from any cpu but the caller must
346 * serialize callout_stop() and callout_reset() calls on the passed
347 * structure regardless of cpu.
92b561b7 348 */
984263bc 349void
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350callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
351 void *arg)
984263bc 352{
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353 softclock_pcpu_t sc;
354 globaldata_t gd;
355
356#ifdef INVARIANTS
357 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
358 callout_init(c);
6ea70f76 359 kprintf(
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360 "callout_reset(%p) from %p: callout was not initialized\n",
361 c, ((int **)&c)[-1]);
7ce2998e 362 print_backtrace(-1);
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363 }
364#endif
365 gd = mycpu;
366 sc = &softclock_pcpu_ary[gd->gd_cpuid];
367 crit_enter_gd(gd);
984263bc 368
b90e37ec 369 if (c->c_flags & CALLOUT_ACTIVE)
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370 callout_stop(c);
371
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372 if (to_ticks <= 0)
373 to_ticks = 1;
374
375 c->c_arg = arg;
376 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
377 c->c_func = ftn;
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378 c->c_time = sc->curticks + to_ticks;
379#ifdef SMP
380 c->c_gd = gd;
381#endif
382
383 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask],
984263bc 384 c, c_links.tqe);
92b561b7 385 crit_exit_gd(gd);
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386}
387
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388/*
389 * Stop a running timer. WARNING! If called on a cpu other then the one
390 * the callout was started on this function will liveloop on its IPI to
391 * the target cpu to process the request. It is possible for the callout
392 * to execute in that case.
393 *
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394 * WARNING! This function may be called from any cpu but the caller must
395 * serialize callout_stop() and callout_reset() calls on the passed
396 * structure regardless of cpu.
397 *
92b561b7 398 * WARNING! This routine may be called from an IPI
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399 *
400 * WARNING! This function can return while it's c_func is still running
401 * in the callout thread, a secondary check may be needed.
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402 * Use callout_stop_sync() to wait for any callout function to
403 * complete before returning, being sure that no deadlock is
404 * possible if you do.
92b561b7 405 */
984263bc 406int
216ffe3f 407callout_stop(struct callout *c)
984263bc 408{
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409 globaldata_t gd = mycpu;
410#ifdef SMP
411 globaldata_t tgd;
412#endif
413 softclock_pcpu_t sc;
414
415#ifdef INVARIANTS
416 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
417 callout_init(c);
6ea70f76 418 kprintf(
634056cf 419 "callout_stop(%p) from %p: callout was not initialized\n",
92b561b7 420 c, ((int **)&c)[-1]);
7ce2998e 421 print_backtrace(-1);
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422 }
423#endif
424 crit_enter_gd(gd);
984263bc 425
984263bc 426 /*
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427 * Don't attempt to delete a callout that's not on the queue. The
428 * callout may not have a cpu assigned to it. Callers do not have
429 * to be on the issuing cpu but must still serialize access to the
430 * callout structure.
431 *
432 * We are not cpu-localized here and cannot safely modify the
433 * flags field in the callout structure. Note that most of the
434 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
435 *
436 * If we race another cpu's dispatch of this callout it is possible
437 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
438 * will cause us to fall through and synchronize with the other
439 * cpu.
984263bc 440 */
92b561b7 441 if ((c->c_flags & CALLOUT_PENDING) == 0) {
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442#ifdef SMP
443 if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
444 crit_exit_gd(gd);
445 return (0);
446 }
447 if (c->c_gd == NULL || c->c_gd == gd) {
448 c->c_flags &= ~CALLOUT_ACTIVE;
449 crit_exit_gd(gd);
450 return (0);
451 }
452 /* fall-through to the cpu-localization code. */
453#else
984263bc 454 c->c_flags &= ~CALLOUT_ACTIVE;
92b561b7 455 crit_exit_gd(gd);
984263bc 456 return (0);
7ac978db 457#endif
984263bc 458 }
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459#ifdef SMP
460 if ((tgd = c->c_gd) != gd) {
461 /*
462 * If the callout is owned by a different CPU we have to
463 * execute the function synchronously on the target cpu.
464 */
465 int seq;
466
35238fa5 467 cpu_ccfence(); /* don't let tgd alias c_gd */
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468 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
469 lwkt_wait_ipiq(tgd, seq);
470 } else
471#endif
472 {
473 /*
474 * If the callout is owned by the same CPU we can
475 * process it directly, but if we are racing our helper
476 * thread (sc->next), we have to adjust sc->next. The
477 * race is interlocked by a critical section.
478 */
479 sc = &softclock_pcpu_ary[gd->gd_cpuid];
984263bc 480
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481 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
482 if (sc->next == c)
483 sc->next = TAILQ_NEXT(c, c_links.tqe);
484
485 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
486 c, c_links.tqe);
487 c->c_func = NULL;
984263bc 488 }
92b561b7 489 crit_exit_gd(gd);
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490 return (1);
491}
492
92b561b7 493/*
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494 * Issue a callout_stop() and ensure that any callout race completes
495 * before returning. Does NOT de-initialized the callout.
496 */
497void
498callout_stop_sync(struct callout *c)
499{
500 softclock_pcpu_t sc;
501
502 if (c->c_flags & CALLOUT_DID_INIT) {
503 callout_stop(c);
504#ifdef SMP
505 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
506#else
507 sc = &softclock_pcpu_ary[0];
508#endif
509 if (sc->running == c) {
510 while (sc->running == c)
511 tsleep(&sc->running, 0, "crace", 1);
512 }
513 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
514 }
515}
516
517/*
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518 * Terminate a callout
519 *
520 * This function will stop any pending callout and also block while the
521 * callout's function is running. It should only be used in cases where
522 * no deadlock is possible (due to the callout function acquiring locks
523 * that the current caller of callout_terminate() already holds), when
524 * the caller is ready to destroy the callout structure.
525 *
526 * This function clears the CALLOUT_DID_INIT flag.
527 *
528 * lwkt_token locks are ok.
529 */
530void
531callout_terminate(struct callout *c)
532{
533 softclock_pcpu_t sc;
534
535 if (c->c_flags & CALLOUT_DID_INIT) {
536 callout_stop(c);
2e393ab4 537#ifdef SMP
b90e37ec 538 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
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539#else
540 sc = &softclock_pcpu_ary[0];
541#endif
b90e37ec 542 if (sc->running == c) {
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543 while (sc->running == c)
544 tsleep(&sc->running, 0, "crace", 1);
545 }
546 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
547 c->c_flags &= ~CALLOUT_DID_INIT;
548 }
549}
550
551/*
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552 * Prepare a callout structure for use by callout_reset() and/or
553 * callout_stop(). The MP version of this routine requires that the callback
986d8a07 554 * function installed by callout_reset() be MP safe.
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555 *
556 * The init functions can be called from any cpu and do not have to be
557 * called from the cpu that the timer will eventually run on.
92b561b7 558 */
984263bc 559void
216ffe3f 560callout_init(struct callout *c)
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561{
562 bzero(c, sizeof *c);
92b561b7 563 c->c_flags = CALLOUT_DID_INIT;
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564}
565
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566void
567callout_init_mp(struct callout *c)
ef0fdad1 568{
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569 callout_init(c);
570 c->c_flags |= CALLOUT_MPSAFE;
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571}
572
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573/* What, are you joking? This is nuts! -Matt */
574#if 0
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575#ifdef APM_FIXUP_CALLTODO
576/*
577 * Adjust the kernel calltodo timeout list. This routine is used after
578 * an APM resume to recalculate the calltodo timer list values with the
579 * number of hz's we have been sleeping. The next hardclock() will detect
580 * that there are fired timers and run softclock() to execute them.
581 *
582 * Please note, I have not done an exhaustive analysis of what code this
583 * might break. I am motivated to have my select()'s and alarm()'s that
584 * have expired during suspend firing upon resume so that the applications
585 * which set the timer can do the maintanence the timer was for as close
586 * as possible to the originally intended time. Testing this code for a
587 * week showed that resuming from a suspend resulted in 22 to 25 timers
588 * firing, which seemed independant on whether the suspend was 2 hours or
589 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
590 */
591void
216ffe3f 592adjust_timeout_calltodo(struct timeval *time_change)
984263bc 593{
1fd87d54 594 struct callout *p;
984263bc 595 unsigned long delta_ticks;
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596
597 /*
598 * How many ticks were we asleep?
599 * (stolen from tvtohz()).
600 */
601
602 /* Don't do anything */
603 if (time_change->tv_sec < 0)
604 return;
605 else if (time_change->tv_sec <= LONG_MAX / 1000000)
606 delta_ticks = (time_change->tv_sec * 1000000 +
607 time_change->tv_usec + (tick - 1)) / tick + 1;
608 else if (time_change->tv_sec <= LONG_MAX / hz)
609 delta_ticks = time_change->tv_sec * hz +
610 (time_change->tv_usec + (tick - 1)) / tick + 1;
611 else
612 delta_ticks = LONG_MAX;
613
614 if (delta_ticks > INT_MAX)
615 delta_ticks = INT_MAX;
616
617 /*
618 * Now rip through the timer calltodo list looking for timers
619 * to expire.
620 */
621
622 /* don't collide with softclock() */
e43a034f 623 crit_enter();
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624 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
625 p->c_time -= delta_ticks;
626
627 /* Break if the timer had more time on it than delta_ticks */
628 if (p->c_time > 0)
629 break;
630
631 /* take back the ticks the timer didn't use (p->c_time <= 0) */
632 delta_ticks = -p->c_time;
633 }
e43a034f 634 crit_exit();
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635
636 return;
637}
638#endif /* APM_FIXUP_CALLTODO */
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639#endif
640