FreeBSD/Linux Kernel Cross Reference
sys/kern/lwkt_ipiq.c
1 /*
2 * Copyright (c) 2003,2004 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 /*
36 * This module implements IPI message queueing and the MI portion of IPI
37 * message processing.
38 */
39
40 #include "opt_ddb.h"
41
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
45 #include <sys/proc.h>
46 #include <sys/rtprio.h>
47 #include <sys/queue.h>
48 #include <sys/thread2.h>
49 #include <sys/sysctl.h>
50 #include <sys/ktr.h>
51 #include <sys/kthread.h>
52 #include <machine/cpu.h>
53 #include <sys/lock.h>
54
55 #include <vm/vm.h>
56 #include <vm/vm_param.h>
57 #include <vm/vm_kern.h>
58 #include <vm/vm_object.h>
59 #include <vm/vm_page.h>
60 #include <vm/vm_map.h>
61 #include <vm/vm_pager.h>
62 #include <vm/vm_extern.h>
63 #include <vm/vm_zone.h>
64
65 #include <machine/stdarg.h>
66 #include <machine/smp.h>
67 #include <machine/atomic.h>
68
69 #ifdef _KERNEL_VIRTUAL
70 #include <pthread.h>
71 #endif
72
73 struct ipiq_stats {
74 __int64_t ipiq_count; /* total calls to lwkt_send_ipiq*() */
75 __int64_t ipiq_fifofull; /* number of fifo full conditions detected */
76 __int64_t ipiq_avoided; /* interlock with target avoids cpu ipi */
77 __int64_t ipiq_passive; /* passive IPI messages */
78 __int64_t ipiq_cscount; /* number of cpu synchronizations */
79 } __cachealign;
80
81 static struct ipiq_stats ipiq_stats_percpu[MAXCPU];
82 #define ipiq_stat(gd) ipiq_stats_percpu[(gd)->gd_cpuid]
83
84 static int ipiq_debug; /* set to 1 for debug */
85 #ifdef PANIC_DEBUG
86 static int panic_ipiq_cpu = -1;
87 static int panic_ipiq_count = 100;
88 #endif
89
90 SYSCTL_INT(_lwkt, OID_AUTO, ipiq_debug, CTLFLAG_RW, &ipiq_debug, 0,
91 "");
92 #ifdef PANIC_DEBUG
93 SYSCTL_INT(_lwkt, OID_AUTO, panic_ipiq_cpu, CTLFLAG_RW, &panic_ipiq_cpu, 0, "");
94 SYSCTL_INT(_lwkt, OID_AUTO, panic_ipiq_count, CTLFLAG_RW, &panic_ipiq_count, 0, "");
95 #endif
96
97 #define IPIQ_STRING "func=%p arg1=%p arg2=%d scpu=%d dcpu=%d"
98 #define IPIQ_ARGS void *func, void *arg1, int arg2, int scpu, int dcpu
99
100 #if !defined(KTR_IPIQ)
101 #define KTR_IPIQ KTR_ALL
102 #endif
103 KTR_INFO_MASTER(ipiq);
104 KTR_INFO(KTR_IPIQ, ipiq, send_norm, 0, IPIQ_STRING, IPIQ_ARGS);
105 KTR_INFO(KTR_IPIQ, ipiq, send_pasv, 1, IPIQ_STRING, IPIQ_ARGS);
106 KTR_INFO(KTR_IPIQ, ipiq, send_nbio, 2, IPIQ_STRING, IPIQ_ARGS);
107 KTR_INFO(KTR_IPIQ, ipiq, send_fail, 3, IPIQ_STRING, IPIQ_ARGS);
108 KTR_INFO(KTR_IPIQ, ipiq, receive, 4, IPIQ_STRING, IPIQ_ARGS);
109 KTR_INFO(KTR_IPIQ, ipiq, sync_start, 5, "cpumask=%08lx", unsigned long mask);
110 KTR_INFO(KTR_IPIQ, ipiq, sync_end, 6, "cpumask=%08lx", unsigned long mask);
111 KTR_INFO(KTR_IPIQ, ipiq, cpu_send, 7, IPIQ_STRING, IPIQ_ARGS);
112 KTR_INFO(KTR_IPIQ, ipiq, send_end, 8, IPIQ_STRING, IPIQ_ARGS);
113
114 #define logipiq(name, func, arg1, arg2, sgd, dgd) \
115 KTR_LOG(ipiq_ ## name, func, arg1, arg2, sgd->gd_cpuid, dgd->gd_cpuid)
116 #define logipiq2(name, arg) \
117 KTR_LOG(ipiq_ ## name, arg)
118
119 static int lwkt_process_ipiq_core(globaldata_t sgd, lwkt_ipiq_t ip,
120 struct intrframe *frame);
121 static void lwkt_cpusync_remote1(lwkt_cpusync_t cs);
122 static void lwkt_cpusync_remote2(lwkt_cpusync_t cs);
123
124 #define IPIQ_SYSCTL(name) \
125 static int \
126 sysctl_##name(SYSCTL_HANDLER_ARGS) \
127 { \
128 __int64_t val = 0; \
129 int cpu, error; \
130 \
131 for (cpu = 0; cpu < ncpus; ++cpu) \
132 val += ipiq_stats_percpu[cpu].name; \
133 \
134 error = sysctl_handle_quad(oidp, &val, 0, req); \
135 if (error || req->newptr == NULL) \
136 return error; \
137 \
138 for (cpu = 0; cpu < ncpus; ++cpu) \
139 ipiq_stats_percpu[cpu].name = val; \
140 \
141 return 0; \
142 }
143
144 IPIQ_SYSCTL(ipiq_count);
145 IPIQ_SYSCTL(ipiq_fifofull);
146 IPIQ_SYSCTL(ipiq_avoided);
147 IPIQ_SYSCTL(ipiq_passive);
148 IPIQ_SYSCTL(ipiq_cscount);
149
150 SYSCTL_PROC(_lwkt, OID_AUTO, ipiq_count, (CTLTYPE_QUAD | CTLFLAG_RW),
151 0, 0, sysctl_ipiq_count, "Q", "Number of IPI's sent");
152 SYSCTL_PROC(_lwkt, OID_AUTO, ipiq_fifofull, (CTLTYPE_QUAD | CTLFLAG_RW),
153 0, 0, sysctl_ipiq_fifofull, "Q",
154 "Number of fifo full conditions detected");
155 SYSCTL_PROC(_lwkt, OID_AUTO, ipiq_avoided, (CTLTYPE_QUAD | CTLFLAG_RW),
156 0, 0, sysctl_ipiq_avoided, "Q",
157 "Number of IPI's avoided by interlock with target cpu");
158 SYSCTL_PROC(_lwkt, OID_AUTO, ipiq_passive, (CTLTYPE_QUAD | CTLFLAG_RW),
159 0, 0, sysctl_ipiq_passive, "Q",
160 "Number of passive IPI messages sent");
161 SYSCTL_PROC(_lwkt, OID_AUTO, ipiq_cscount, (CTLTYPE_QUAD | CTLFLAG_RW),
162 0, 0, sysctl_ipiq_cscount, "Q",
163 "Number of cpu synchronizations");
164
165 /*
166 * Send a function execution request to another cpu. The request is queued
167 * on the cpu<->cpu ipiq matrix. Each cpu owns a unique ipiq FIFO for every
168 * possible target cpu. The FIFO can be written.
169 *
170 * If the FIFO fills up we have to enable interrupts to avoid an APIC
171 * deadlock and process pending IPIQs while waiting for it to empty.
172 * Otherwise we may soft-deadlock with another cpu whos FIFO is also full.
173 *
174 * We can safely bump gd_intr_nesting_level because our crit_exit() at the
175 * end will take care of any pending interrupts.
176 *
177 * The actual hardware IPI is avoided if the target cpu is already processing
178 * the queue from a prior IPI. It is possible to pipeline IPI messages
179 * very quickly between cpus due to the FIFO hysteresis.
180 *
181 * Need not be called from a critical section.
182 */
183 int
184 lwkt_send_ipiq3(globaldata_t target, ipifunc3_t func, void *arg1, int arg2)
185 {
186 lwkt_ipiq_t ip;
187 int windex;
188 #ifdef _KERNEL_VIRTUAL
189 int repeating = 0;
190 #endif
191 struct globaldata *gd = mycpu;
192
193 logipiq(send_norm, func, arg1, arg2, gd, target);
194
195 if (target == gd) {
196 func(arg1, arg2, NULL);
197 logipiq(send_end, func, arg1, arg2, gd, target);
198 return(0);
199 }
200 crit_enter();
201 ++gd->gd_intr_nesting_level;
202 #ifdef INVARIANTS
203 if (gd->gd_intr_nesting_level > 20)
204 panic("lwkt_send_ipiq: TOO HEAVILY NESTED!");
205 #endif
206 KKASSERT(curthread->td_critcount);
207 ++ipiq_stat(gd).ipiq_count;
208 ip = &gd->gd_ipiq[target->gd_cpuid];
209
210 /*
211 * Do not allow the FIFO to become full. Interrupts must be physically
212 * enabled while we liveloop to avoid deadlocking the APIC.
213 *
214 * The target ipiq may have gotten filled up due to passive IPIs and thus
215 * not be aware that its queue is too full, so be sure to issue an
216 * ipiq interrupt to the target cpu.
217 */
218 if (ip->ip_windex - ip->ip_rindex > MAXCPUFIFO / 2) {
219 #if defined(__i386__)
220 unsigned int eflags = read_eflags();
221 #elif defined(__x86_64__)
222 unsigned long rflags = read_rflags();
223 #endif
224
225 cpu_enable_intr();
226 ++ipiq_stat(gd).ipiq_fifofull;
227 DEBUG_PUSH_INFO("send_ipiq3");
228 while (ip->ip_windex - ip->ip_rindex > MAXCPUFIFO / 4) {
229 if (atomic_poll_acquire_int(&target->gd_npoll)) {
230 logipiq(cpu_send, func, arg1, arg2, gd, target);
231 cpu_send_ipiq(target->gd_cpuid);
232 }
233 KKASSERT(ip->ip_windex - ip->ip_rindex != MAXCPUFIFO - 1);
234 lwkt_process_ipiq();
235 cpu_pause();
236 #ifdef _KERNEL_VIRTUAL
237 if (repeating++ > 10)
238 pthread_yield();
239 #endif
240 }
241 DEBUG_POP_INFO();
242 #if defined(__i386__)
243 write_eflags(eflags);
244 #elif defined(__x86_64__)
245 write_rflags(rflags);
246 #endif
247 }
248
249 /*
250 * Queue the new message
251 */
252 windex = ip->ip_windex & MAXCPUFIFO_MASK;
253 ip->ip_info[windex].func = func;
254 ip->ip_info[windex].arg1 = arg1;
255 ip->ip_info[windex].arg2 = arg2;
256 cpu_sfence();
257 ++ip->ip_windex;
258 atomic_set_cpumask(&target->gd_ipimask, gd->gd_cpumask);
259
260 /*
261 * signal the target cpu that there is work pending.
262 */
263 if (atomic_poll_acquire_int(&target->gd_npoll)) {
264 logipiq(cpu_send, func, arg1, arg2, gd, target);
265 cpu_send_ipiq(target->gd_cpuid);
266 } else {
267 ++ipiq_stat(gd).ipiq_avoided;
268 }
269 --gd->gd_intr_nesting_level;
270 crit_exit();
271 logipiq(send_end, func, arg1, arg2, gd, target);
272
273 return(ip->ip_windex);
274 }
275
276 /*
277 * Similar to lwkt_send_ipiq() but this function does not actually initiate
278 * the IPI to the target cpu unless the FIFO has become too full, so it is
279 * very fast.
280 *
281 * This function is used for non-critical IPI messages, such as memory
282 * deallocations. The queue will typically be flushed by the target cpu at
283 * the next clock interrupt.
284 *
285 * Need not be called from a critical section.
286 */
287 int
288 lwkt_send_ipiq3_passive(globaldata_t target, ipifunc3_t func,
289 void *arg1, int arg2)
290 {
291 lwkt_ipiq_t ip;
292 int windex;
293 #ifdef _KERNEL_VIRTUAL
294 int repeating = 0;
295 #endif
296 struct globaldata *gd = mycpu;
297
298 KKASSERT(target != gd);
299 crit_enter();
300 ++gd->gd_intr_nesting_level;
301 logipiq(send_pasv, func, arg1, arg2, gd, target);
302 #ifdef INVARIANTS
303 if (gd->gd_intr_nesting_level > 20)
304 panic("lwkt_send_ipiq: TOO HEAVILY NESTED!");
305 #endif
306 KKASSERT(curthread->td_critcount);
307 ++ipiq_stat(gd).ipiq_count;
308 ++ipiq_stat(gd).ipiq_passive;
309 ip = &gd->gd_ipiq[target->gd_cpuid];
310
311 /*
312 * Do not allow the FIFO to become full. Interrupts must be physically
313 * enabled while we liveloop to avoid deadlocking the APIC.
314 */
315 if (ip->ip_windex - ip->ip_rindex > MAXCPUFIFO / 2) {
316 #if defined(__i386__)
317 unsigned int eflags = read_eflags();
318 #elif defined(__x86_64__)
319 unsigned long rflags = read_rflags();
320 #endif
321
322 cpu_enable_intr();
323 ++ipiq_stat(gd).ipiq_fifofull;
324 DEBUG_PUSH_INFO("send_ipiq3_passive");
325 while (ip->ip_windex - ip->ip_rindex > MAXCPUFIFO / 4) {
326 if (atomic_poll_acquire_int(&target->gd_npoll)) {
327 logipiq(cpu_send, func, arg1, arg2, gd, target);
328 cpu_send_ipiq(target->gd_cpuid);
329 }
330 KKASSERT(ip->ip_windex - ip->ip_rindex != MAXCPUFIFO - 1);
331 lwkt_process_ipiq();
332 cpu_pause();
333 #ifdef _KERNEL_VIRTUAL
334 if (repeating++ > 10)
335 pthread_yield();
336 #endif
337 }
338 DEBUG_POP_INFO();
339 #if defined(__i386__)
340 write_eflags(eflags);
341 #elif defined(__x86_64__)
342 write_rflags(rflags);
343 #endif
344 }
345
346 /*
347 * Queue the new message
348 */
349 windex = ip->ip_windex & MAXCPUFIFO_MASK;
350 ip->ip_info[windex].func = func;
351 ip->ip_info[windex].arg1 = arg1;
352 ip->ip_info[windex].arg2 = arg2;
353 cpu_sfence();
354 ++ip->ip_windex;
355 atomic_set_cpumask(&target->gd_ipimask, gd->gd_cpumask);
356 --gd->gd_intr_nesting_level;
357
358 /*
359 * Do not signal the target cpu, it will pick up the IPI when it next
360 * polls (typically on the next tick).
361 */
362 crit_exit();
363 logipiq(send_end, func, arg1, arg2, gd, target);
364
365 return(ip->ip_windex);
366 }
367
368 /*
369 * Send an IPI request without blocking, return 0 on success, ENOENT on
370 * failure. The actual queueing of the hardware IPI may still force us
371 * to spin and process incoming IPIs but that will eventually go away
372 * when we've gotten rid of the other general IPIs.
373 */
374 int
375 lwkt_send_ipiq3_nowait(globaldata_t target, ipifunc3_t func,
376 void *arg1, int arg2)
377 {
378 lwkt_ipiq_t ip;
379 int windex;
380 struct globaldata *gd = mycpu;
381
382 logipiq(send_nbio, func, arg1, arg2, gd, target);
383 KKASSERT(curthread->td_critcount);
384 if (target == gd) {
385 func(arg1, arg2, NULL);
386 logipiq(send_end, func, arg1, arg2, gd, target);
387 return(0);
388 }
389 crit_enter();
390 ++gd->gd_intr_nesting_level;
391 ++ipiq_stat(gd).ipiq_count;
392 ip = &gd->gd_ipiq[target->gd_cpuid];
393
394 if (ip->ip_windex - ip->ip_rindex >= MAXCPUFIFO * 2 / 3) {
395 logipiq(send_fail, func, arg1, arg2, gd, target);
396 --gd->gd_intr_nesting_level;
397 crit_exit();
398 return(ENOENT);
399 }
400 windex = ip->ip_windex & MAXCPUFIFO_MASK;
401 ip->ip_info[windex].func = func;
402 ip->ip_info[windex].arg1 = arg1;
403 ip->ip_info[windex].arg2 = arg2;
404 cpu_sfence();
405 ++ip->ip_windex;
406 atomic_set_cpumask(&target->gd_ipimask, gd->gd_cpumask);
407
408 /*
409 * This isn't a passive IPI, we still have to signal the target cpu.
410 */
411 if (atomic_poll_acquire_int(&target->gd_npoll)) {
412 logipiq(cpu_send, func, arg1, arg2, gd, target);
413 cpu_send_ipiq(target->gd_cpuid);
414 } else {
415 ++ipiq_stat(gd).ipiq_avoided;
416 }
417 --gd->gd_intr_nesting_level;
418 crit_exit();
419
420 logipiq(send_end, func, arg1, arg2, gd, target);
421 return(0);
422 }
423
424 /*
425 * deprecated, used only by fast int forwarding.
426 */
427 int
428 lwkt_send_ipiq3_bycpu(int dcpu, ipifunc3_t func, void *arg1, int arg2)
429 {
430 return(lwkt_send_ipiq3(globaldata_find(dcpu), func, arg1, arg2));
431 }
432
433 /*
434 * Send a message to several target cpus. Typically used for scheduling.
435 * The message will not be sent to stopped cpus.
436 */
437 int
438 lwkt_send_ipiq3_mask(cpumask_t mask, ipifunc3_t func, void *arg1, int arg2)
439 {
440 int cpuid;
441 int count = 0;
442
443 mask &= ~stopped_cpus;
444 while (mask) {
445 cpuid = BSFCPUMASK(mask);
446 lwkt_send_ipiq3(globaldata_find(cpuid), func, arg1, arg2);
447 mask &= ~CPUMASK(cpuid);
448 ++count;
449 }
450 return(count);
451 }
452
453 /*
454 * Wait for the remote cpu to finish processing a function.
455 *
456 * YYY we have to enable interrupts and process the IPIQ while waiting
457 * for it to empty or we may deadlock with another cpu. Create a CPU_*()
458 * function to do this! YYY we really should 'block' here.
459 *
460 * MUST be called from a critical section. This routine may be called
461 * from an interrupt (for example, if an interrupt wakes a foreign thread
462 * up).
463 */
464 void
465 lwkt_wait_ipiq(globaldata_t target, int seq)
466 {
467 lwkt_ipiq_t ip;
468
469 if (target != mycpu) {
470 ip = &mycpu->gd_ipiq[target->gd_cpuid];
471 if ((int)(ip->ip_xindex - seq) < 0) {
472 #if defined(__i386__)
473 unsigned int eflags = read_eflags();
474 #elif defined(__x86_64__)
475 unsigned long rflags = read_rflags();
476 #endif
477 int64_t time_tgt = tsc_get_target(1000000000LL);
478 int time_loops = 10;
479 int benice = 0;
480 #ifdef _KERNEL_VIRTUAL
481 int repeating = 0;
482 #endif
483
484 cpu_enable_intr();
485 DEBUG_PUSH_INFO("wait_ipiq");
486 while ((int)(ip->ip_xindex - seq) < 0) {
487 crit_enter();
488 lwkt_process_ipiq();
489 crit_exit();
490 #ifdef _KERNEL_VIRTUAL
491 if (repeating++ > 10)
492 pthread_yield();
493 #endif
494
495 /*
496 * IPIQs must be handled within 10 seconds and this code
497 * will warn after one second.
498 */
499 if ((benice & 255) == 0 && tsc_test_target(time_tgt) > 0) {
500 kprintf("LWKT_WAIT_IPIQ WARNING! %d wait %d (%d)\n",
501 mycpu->gd_cpuid, target->gd_cpuid,
502 ip->ip_xindex - seq);
503 if (--time_loops == 0)
504 panic("LWKT_WAIT_IPIQ");
505 time_tgt = tsc_get_target(1000000000LL);
506 }
507 ++benice;
508
509 /*
510 * xindex may be modified by another cpu, use a load fence
511 * to ensure that the loop does not use a speculative value
512 * (which may improve performance).
513 */
514 cpu_lfence();
515 }
516 DEBUG_POP_INFO();
517 #if defined(__i386__)
518 write_eflags(eflags);
519 #elif defined(__x86_64__)
520 write_rflags(rflags);
521 #endif
522 }
523 }
524 }
525
526 int
527 lwkt_seq_ipiq(globaldata_t target)
528 {
529 lwkt_ipiq_t ip;
530
531 ip = &mycpu->gd_ipiq[target->gd_cpuid];
532 return(ip->ip_windex);
533 }
534
535 /*
536 * Called from IPI interrupt (like a fast interrupt), which has placed
537 * us in a critical section. The MP lock may or may not be held.
538 * May also be called from doreti or splz, or be reentrantly called
539 * indirectly through the ip_info[].func we run.
540 *
541 * There are two versions, one where no interrupt frame is available (when
542 * called from the send code and from splz, and one where an interrupt
543 * frame is available.
544 *
545 * When the current cpu is mastering a cpusync we do NOT internally loop
546 * on the cpusyncq poll. We also do not re-flag a pending ipi due to
547 * the cpusyncq poll because this can cause doreti/splz to loop internally.
548 * The cpusync master's own loop must be allowed to run to avoid a deadlock.
549 */
550 void
551 lwkt_process_ipiq(void)
552 {
553 globaldata_t gd = mycpu;
554 globaldata_t sgd;
555 lwkt_ipiq_t ip;
556 cpumask_t mask;
557 int n;
558
559 ++gd->gd_processing_ipiq;
560 again:
561 cpu_lfence();
562 mask = gd->gd_ipimask;
563 atomic_clear_cpumask(&gd->gd_ipimask, mask);
564 while (mask) {
565 n = BSFCPUMASK(mask);
566 if (n != gd->gd_cpuid) {
567 sgd = globaldata_find(n);
568 ip = sgd->gd_ipiq;
569 if (ip != NULL) {
570 while (lwkt_process_ipiq_core(sgd, &ip[gd->gd_cpuid], NULL))
571 ;
572 }
573 }
574 mask &= ~CPUMASK(n);
575 }
576
577 /*
578 * Process pending cpusyncs. If the current thread has a cpusync
579 * active cpusync we only run the list once and do not re-flag
580 * as the thread itself is processing its interlock.
581 */
582 if (lwkt_process_ipiq_core(gd, &gd->gd_cpusyncq, NULL)) {
583 if (gd->gd_curthread->td_cscount == 0)
584 goto again;
585 /* need_ipiq(); do not reflag */
586 }
587
588 /*
589 * Interlock to allow more IPI interrupts. Recheck ipimask after
590 * releasing gd_npoll.
591 */
592 if (gd->gd_ipimask)
593 goto again;
594 atomic_poll_release_int(&gd->gd_npoll);
595 cpu_mfence();
596 if (gd->gd_ipimask)
597 goto again;
598 --gd->gd_processing_ipiq;
599 }
600
601 void
602 lwkt_process_ipiq_frame(struct intrframe *frame)
603 {
604 globaldata_t gd = mycpu;
605 globaldata_t sgd;
606 lwkt_ipiq_t ip;
607 cpumask_t mask;
608 int n;
609
610 again:
611 cpu_lfence();
612 mask = gd->gd_ipimask;
613 atomic_clear_cpumask(&gd->gd_ipimask, mask);
614 while (mask) {
615 n = BSFCPUMASK(mask);
616 if (n != gd->gd_cpuid) {
617 sgd = globaldata_find(n);
618 ip = sgd->gd_ipiq;
619 if (ip != NULL) {
620 while (lwkt_process_ipiq_core(sgd, &ip[gd->gd_cpuid], frame))
621 ;
622 }
623 }
624 mask &= ~CPUMASK(n);
625 }
626 if (gd->gd_cpusyncq.ip_rindex != gd->gd_cpusyncq.ip_windex) {
627 if (lwkt_process_ipiq_core(gd, &gd->gd_cpusyncq, frame)) {
628 if (gd->gd_curthread->td_cscount == 0)
629 goto again;
630 /* need_ipiq(); do not reflag */
631 }
632 }
633
634 /*
635 * Interlock to allow more IPI interrupts. Recheck ipimask after
636 * releasing gd_npoll.
637 */
638 if (gd->gd_ipimask)
639 goto again;
640 atomic_poll_release_int(&gd->gd_npoll);
641 cpu_mfence();
642 if (gd->gd_ipimask)
643 goto again;
644 }
645
646 #if 0
647 static int iqticks[SMP_MAXCPU];
648 static int iqcount[SMP_MAXCPU];
649 #endif
650 #if 0
651 static int iqterm[SMP_MAXCPU];
652 #endif
653
654 static int
655 lwkt_process_ipiq_core(globaldata_t sgd, lwkt_ipiq_t ip,
656 struct intrframe *frame)
657 {
658 globaldata_t mygd = mycpu;
659 int ri;
660 int wi;
661 ipifunc3_t copy_func;
662 void *copy_arg1;
663 int copy_arg2;
664
665 #if 0
666 if (iqticks[mygd->gd_cpuid] != ticks) {
667 iqticks[mygd->gd_cpuid] = ticks;
668 iqcount[mygd->gd_cpuid] = 0;
669 }
670 if (++iqcount[mygd->gd_cpuid] > 3000000) {
671 kprintf("cpu %d ipiq maxed cscount %d spin %d\n",
672 mygd->gd_cpuid,
673 mygd->gd_curthread->td_cscount,
674 mygd->gd_spinlocks);
675 iqcount[mygd->gd_cpuid] = 0;
676 #if 0
677 if (++iqterm[mygd->gd_cpuid] > 10)
678 panic("cpu %d ipiq maxed", mygd->gd_cpuid);
679 #endif
680 int i;
681 for (i = 0; i < ncpus; ++i) {
682 if (globaldata_find(i)->gd_infomsg)
683 kprintf(" %s", globaldata_find(i)->gd_infomsg);
684 }
685 kprintf("\n");
686 }
687 #endif
688
689 /*
690 * Clear the originating core from our ipimask, we will process all
691 * incoming messages.
692 *
693 * Obtain the current write index, which is modified by a remote cpu.
694 * Issue a load fence to prevent speculative reads of e.g. data written
695 * by the other cpu prior to it updating the index.
696 */
697 KKASSERT(curthread->td_critcount);
698 wi = ip->ip_windex;
699 cpu_lfence();
700 ++mygd->gd_intr_nesting_level;
701
702 /*
703 * NOTE: xindex is only updated after we are sure the function has
704 * finished execution. Beware lwkt_process_ipiq() reentrancy!
705 * The function may send an IPI which may block/drain.
706 *
707 * NOTE: Due to additional IPI operations that the callback function
708 * may make, it is possible for both rindex and windex to advance and
709 * thus for rindex to advance passed our cached windex.
710 *
711 * NOTE: A load fence is required to prevent speculative loads prior
712 * to the loading of ip_rindex. Even though stores might be
713 * ordered, loads are probably not. A memory fence is required
714 * to prevent reordering of the loads after the ip_rindex update.
715 *
716 * NOTE: Single pass only. Returns non-zero if the queue is not empty
717 * on return.
718 */
719 while (wi - (ri = ip->ip_rindex) > 0) {
720 ri &= MAXCPUFIFO_MASK;
721 cpu_lfence();
722 copy_func = ip->ip_info[ri].func;
723 copy_arg1 = ip->ip_info[ri].arg1;
724 copy_arg2 = ip->ip_info[ri].arg2;
725 cpu_mfence();
726 ++ip->ip_rindex;
727 KKASSERT((ip->ip_rindex & MAXCPUFIFO_MASK) ==
728 ((ri + 1) & MAXCPUFIFO_MASK));
729 logipiq(receive, copy_func, copy_arg1, copy_arg2, sgd, mycpu);
730 #ifdef INVARIANTS
731 if (ipiq_debug && (ip->ip_rindex & 0xFFFFFF) == 0) {
732 kprintf("cpu %d ipifunc %p %p %d (frame %p)\n",
733 mycpu->gd_cpuid,
734 copy_func, copy_arg1, copy_arg2,
735 #if defined(__i386__)
736 (frame ? (void *)frame->if_eip : NULL));
737 #elif defined(__x86_64__)
738 (frame ? (void *)frame->if_rip : NULL));
739 #else
740 NULL);
741 #endif
742 }
743 #endif
744 copy_func(copy_arg1, copy_arg2, frame);
745 cpu_sfence();
746 ip->ip_xindex = ip->ip_rindex;
747
748 #ifdef PANIC_DEBUG
749 /*
750 * Simulate panics during the processing of an IPI
751 */
752 if (mycpu->gd_cpuid == panic_ipiq_cpu && panic_ipiq_count) {
753 if (--panic_ipiq_count == 0) {
754 #ifdef DDB
755 Debugger("PANIC_DEBUG");
756 #else
757 panic("PANIC_DEBUG");
758 #endif
759 }
760 }
761 #endif
762 }
763 --mygd->gd_intr_nesting_level;
764
765 /*
766 * Return non-zero if there is still more in the queue.
767 */
768 cpu_lfence();
769 return (ip->ip_rindex != ip->ip_windex);
770 }
771
772 static void
773 lwkt_sync_ipiq(void *arg)
774 {
775 volatile cpumask_t *cpumask = arg;
776
777 atomic_clear_cpumask(cpumask, mycpu->gd_cpumask);
778 if (*cpumask == 0)
779 wakeup(cpumask);
780 }
781
782 void
783 lwkt_synchronize_ipiqs(const char *wmesg)
784 {
785 volatile cpumask_t other_cpumask;
786
787 other_cpumask = mycpu->gd_other_cpus & smp_active_mask;
788 lwkt_send_ipiq_mask(other_cpumask, lwkt_sync_ipiq,
789 __DEVOLATILE(void *, &other_cpumask));
790
791 while (other_cpumask != 0) {
792 tsleep_interlock(&other_cpumask, 0);
793 if (other_cpumask != 0)
794 tsleep(&other_cpumask, PINTERLOCKED, wmesg, 0);
795 }
796 }
797
798 /*
799 * CPU Synchronization Support
800 *
801 * lwkt_cpusync_interlock() - Place specified cpus in a quiescent state.
802 * The current cpu is placed in a hard critical
803 * section.
804 *
805 * lwkt_cpusync_deinterlock() - Execute cs_func on specified cpus, including
806 * current cpu if specified, then return.
807 */
808 void
809 lwkt_cpusync_simple(cpumask_t mask, cpusync_func_t func, void *arg)
810 {
811 struct lwkt_cpusync cs;
812
813 lwkt_cpusync_init(&cs, mask, func, arg);
814 lwkt_cpusync_interlock(&cs);
815 lwkt_cpusync_deinterlock(&cs);
816 }
817
818
819 void
820 lwkt_cpusync_interlock(lwkt_cpusync_t cs)
821 {
822 #if 0
823 const char *smsg = "SMPSYNL";
824 #endif
825 globaldata_t gd = mycpu;
826 cpumask_t mask;
827
828 /*
829 * mask acknowledge (cs_mack): 0->mask for stage 1
830 *
831 * mack does not include the current cpu.
832 */
833 mask = cs->cs_mask & gd->gd_other_cpus & smp_active_mask;
834 cs->cs_mack = 0;
835 crit_enter_id("cpusync");
836 if (mask) {
837 DEBUG_PUSH_INFO("cpusync_interlock");
838 ++ipiq_stat(gd).ipiq_cscount;
839 ++gd->gd_curthread->td_cscount;
840 lwkt_send_ipiq_mask(mask, (ipifunc1_t)lwkt_cpusync_remote1, cs);
841 logipiq2(sync_start, (long)mask);
842 #if 0
843 if (gd->gd_curthread->td_wmesg == NULL)
844 gd->gd_curthread->td_wmesg = smsg;
845 #endif
846 while (cs->cs_mack != mask) {
847 lwkt_process_ipiq();
848 cpu_pause();
849 #ifdef _KERNEL_VIRTUAL
850 pthread_yield();
851 #endif
852 }
853 #if 0
854 if (gd->gd_curthread->td_wmesg == smsg)
855 gd->gd_curthread->td_wmesg = NULL;
856 #endif
857 DEBUG_POP_INFO();
858 }
859 }
860
861 /*
862 * Interlocked cpus have executed remote1 and are polling in remote2.
863 * To deinterlock we clear cs_mack and wait for the cpus to execute
864 * the func and set their bit in cs_mack again.
865 *
866 */
867 void
868 lwkt_cpusync_deinterlock(lwkt_cpusync_t cs)
869 {
870 globaldata_t gd = mycpu;
871 #if 0
872 const char *smsg = "SMPSYNU";
873 #endif
874 cpumask_t mask;
875
876 /*
877 * mask acknowledge (cs_mack): mack->0->mack for stage 2
878 *
879 * Clearing cpu bits for polling cpus in cs_mack will cause them to
880 * execute stage 2, which executes the cs_func(cs_data) and then sets
881 * their bit in cs_mack again.
882 *
883 * mack does not include the current cpu.
884 */
885 mask = cs->cs_mack;
886 cpu_ccfence();
887 cs->cs_mack = 0;
888 cpu_ccfence();
889 if (cs->cs_func && (cs->cs_mask & gd->gd_cpumask))
890 cs->cs_func(cs->cs_data);
891 if (mask) {
892 DEBUG_PUSH_INFO("cpusync_deinterlock");
893 #if 0
894 if (gd->gd_curthread->td_wmesg == NULL)
895 gd->gd_curthread->td_wmesg = smsg;
896 #endif
897 while (cs->cs_mack != mask) {
898 lwkt_process_ipiq();
899 cpu_pause();
900 #ifdef _KERNEL_VIRTUAL
901 pthread_yield();
902 #endif
903 }
904 #if 0
905 if (gd->gd_curthread->td_wmesg == smsg)
906 gd->gd_curthread->td_wmesg = NULL;
907 #endif
908 DEBUG_POP_INFO();
909 /*
910 * cpusyncq ipis may be left queued without the RQF flag set due to
911 * a non-zero td_cscount, so be sure to process any laggards after
912 * decrementing td_cscount.
913 */
914 --gd->gd_curthread->td_cscount;
915 lwkt_process_ipiq();
916 logipiq2(sync_end, (long)mask);
917 }
918 crit_exit_id("cpusync");
919 }
920
921 /*
922 * helper IPI remote messaging function.
923 *
924 * Called on remote cpu when a new cpu synchronization request has been
925 * sent to us. Execute the run function and adjust cs_count, then requeue
926 * the request so we spin on it.
927 */
928 static void
929 lwkt_cpusync_remote1(lwkt_cpusync_t cs)
930 {
931 globaldata_t gd = mycpu;
932
933 atomic_set_cpumask(&cs->cs_mack, gd->gd_cpumask);
934 lwkt_cpusync_remote2(cs);
935 }
936
937 /*
938 * helper IPI remote messaging function.
939 *
940 * Poll for the originator telling us to finish. If it hasn't, requeue
941 * our request so we spin on it.
942 */
943 static void
944 lwkt_cpusync_remote2(lwkt_cpusync_t cs)
945 {
946 globaldata_t gd = mycpu;
947
948 if ((cs->cs_mack & gd->gd_cpumask) == 0) {
949 if (cs->cs_func)
950 cs->cs_func(cs->cs_data);
951 atomic_set_cpumask(&cs->cs_mack, gd->gd_cpumask);
952 /* cs can be ripped out at this point */
953 } else {
954 lwkt_ipiq_t ip;
955 int wi;
956
957 #ifdef _KERNEL_VIRTUAL
958 pthread_yield();
959 #endif
960 ip = &gd->gd_cpusyncq;
961 wi = ip->ip_windex & MAXCPUFIFO_MASK;
962 ip->ip_info[wi].func = (ipifunc3_t)(ipifunc1_t)lwkt_cpusync_remote2;
963 ip->ip_info[wi].arg1 = cs;
964 ip->ip_info[wi].arg2 = 0;
965 cpu_sfence();
966 KKASSERT(ip->ip_windex - ip->ip_rindex < MAXCPUFIFO);
967 ++ip->ip_windex;
968 if (ipiq_debug && (ip->ip_windex & 0xFFFFFF) == 0) {
969 kprintf("cpu %d cm=%016jx %016jx f=%p\n",
970 gd->gd_cpuid,
971 (intmax_t)cs->cs_mask, (intmax_t)cs->cs_mack,
972 cs->cs_func);
973 }
974 }
975 }
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