xref: /netbsd-src/sys/dev/lockstat.c (revision 53d1339bf7f9c7367b35a9e1ebe693f9b047a47b) 
1 /*	$NetBSD: lockstat.c,v 1.27 2020/05/23 23:42:42 ad Exp $	*/
2 
3 /*-
4  * Copyright (c) 2006, 2007, 2019 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Andrew Doran.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29  * POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 /*
33  * Lock statistics driver, providing kernel support for the lockstat(8)
34  * command.
35  *
36  * We use a global lock word (lockstat_lock) to track device opens.
37  * Only one thread can hold the device at a time, providing a global lock.
38  *
39  * XXX Timings for contention on sleep locks are currently incorrect.
40  * XXX Convert this to use timecounters!
41  */
42 
43 #include <sys/cdefs.h>
44 __KERNEL_RCSID(0, "$NetBSD: lockstat.c,v 1.27 2020/05/23 23:42:42 ad Exp $");
45 
46 #include <sys/types.h>
47 #include <sys/param.h>
48 #include <sys/proc.h>
49 #include <sys/resourcevar.h>
50 #include <sys/systm.h>
51 #include <sys/kernel.h>
52 #include <sys/kmem.h>
53 #include <sys/conf.h>
54 #include <sys/cpu.h>
55 #include <sys/syslog.h>
56 #include <sys/atomic.h>
57 
58 #include <dev/lockstat.h>
59 
60 #include <machine/lock.h>
61 
62 #include "ioconf.h"
63 
64 #ifndef __HAVE_CPU_COUNTER
65 #error CPU counters not available
66 #endif
67 
68 #if LONG_BIT == 64
69 #define	LOCKSTAT_HASH_SHIFT	3
70 #elif LONG_BIT == 32
71 #define	LOCKSTAT_HASH_SHIFT	2
72 #endif
73 
74 #define	LOCKSTAT_MINBUFS	1000
75 #define	LOCKSTAT_DEFBUFS	20000
76 #define	LOCKSTAT_MAXBUFS	1000000
77 
78 #define	LOCKSTAT_HASH_SIZE	128
79 #define	LOCKSTAT_HASH_MASK	(LOCKSTAT_HASH_SIZE - 1)
80 #define	LOCKSTAT_HASH(key)	\
81 	((key >> LOCKSTAT_HASH_SHIFT) & LOCKSTAT_HASH_MASK)
82 
83 typedef struct lscpu {
84 	SLIST_HEAD(, lsbuf)	lc_free;
85 	u_int			lc_overflow;
86 	LIST_HEAD(lslist, lsbuf) lc_hash[LOCKSTAT_HASH_SIZE];
87 } lscpu_t;
88 
89 typedef struct lslist lslist_t;
90 
91 void	lockstat_start(lsenable_t *);
92 int	lockstat_alloc(lsenable_t *);
93 void	lockstat_init_tables(lsenable_t *);
94 int	lockstat_stop(lsdisable_t *);
95 void	lockstat_free(void);
96 
97 dev_type_open(lockstat_open);
98 dev_type_close(lockstat_close);
99 dev_type_read(lockstat_read);
100 dev_type_ioctl(lockstat_ioctl);
101 
102 volatile u_int	lockstat_enabled;
103 volatile u_int	lockstat_dev_enabled;
104 uintptr_t	lockstat_csstart;
105 uintptr_t	lockstat_csend;
106 uintptr_t	lockstat_csmask;
107 uintptr_t	lockstat_lamask;
108 uintptr_t	lockstat_lockstart;
109 uintptr_t	lockstat_lockend;
110 __cpu_simple_lock_t lockstat_lock;
111 lwp_t		*lockstat_lwp;
112 lsbuf_t		*lockstat_baseb;
113 size_t		lockstat_sizeb;
114 int		lockstat_busy;
115 struct timespec	lockstat_stime;
116 
117 #ifdef KDTRACE_HOOKS
118 volatile u_int lockstat_dtrace_enabled;
119 CTASSERT(LB_NEVENT <= 3);
120 CTASSERT(LB_NLOCK <= (7 << LB_LOCK_SHIFT));
121 void
122 lockstat_probe_stub(uint32_t id, uintptr_t lock, uintptr_t callsite,
123     uintptr_t flags, uintptr_t count, uintptr_t cycles)
124 {
125 }
126 
127 uint32_t	lockstat_probemap[LS_NPROBES];
128 void		(*lockstat_probe_func)(uint32_t, uintptr_t, uintptr_t,
129 		    uintptr_t, uintptr_t, uintptr_t) = &lockstat_probe_stub;
130 #endif
131 
132 const struct cdevsw lockstat_cdevsw = {
133 	.d_open = lockstat_open,
134 	.d_close = lockstat_close,
135 	.d_read = lockstat_read,
136 	.d_write = nowrite,
137 	.d_ioctl = lockstat_ioctl,
138 	.d_stop = nostop,
139 	.d_tty = notty,
140 	.d_poll = nopoll,
141 	.d_mmap = nommap,
142 	.d_kqfilter = nokqfilter,
143 	.d_discard = nodiscard,
144 	.d_flag = D_OTHER | D_MPSAFE
145 };
146 
147 /*
148  * Called when the pseudo-driver is attached.
149  */
150 void
151 lockstatattach(int nunits)
152 {
153 
154 	(void)nunits;
155 
156 	__cpu_simple_lock_init(&lockstat_lock);
157 }
158 
159 /*
160  * Prepare the per-CPU tables for use, or clear down tables when tracing is
161  * stopped.
162  */
163 void
164 lockstat_init_tables(lsenable_t *le)
165 {
166 	int i, per, slop, cpuno;
167 	CPU_INFO_ITERATOR cii;
168 	struct cpu_info *ci;
169 	lscpu_t *lc;
170 	lsbuf_t *lb;
171 
172 	/* coverity[assert_side_effect] */
173 	KASSERT(!lockstat_dev_enabled);
174 
175 	for (CPU_INFO_FOREACH(cii, ci)) {
176 		if (ci->ci_lockstat != NULL) {
177 			kmem_free(ci->ci_lockstat, sizeof(lscpu_t));
178 			ci->ci_lockstat = NULL;
179 		}
180 	}
181 
182 	if (le == NULL)
183 		return;
184 
185 	lb = lockstat_baseb;
186 	per = le->le_nbufs / ncpu;
187 	slop = le->le_nbufs - (per * ncpu);
188 	cpuno = 0;
189 	for (CPU_INFO_FOREACH(cii, ci)) {
190 		lc = kmem_alloc(sizeof(*lc), KM_SLEEP);
191 		lc->lc_overflow = 0;
192 		ci->ci_lockstat = lc;
193 
194 		SLIST_INIT(&lc->lc_free);
195 		for (i = 0; i < LOCKSTAT_HASH_SIZE; i++)
196 			LIST_INIT(&lc->lc_hash[i]);
197 
198 		for (i = per; i != 0; i--, lb++) {
199 			lb->lb_cpu = (uint16_t)cpuno;
200 			SLIST_INSERT_HEAD(&lc->lc_free, lb, lb_chain.slist);
201 		}
202 		if (--slop > 0) {
203 			lb->lb_cpu = (uint16_t)cpuno;
204 			SLIST_INSERT_HEAD(&lc->lc_free, lb, lb_chain.slist);
205 			lb++;
206 		}
207 		cpuno++;
208 	}
209 }
210 
211 /*
212  * Start collecting lock statistics.
213  */
214 void
215 lockstat_start(lsenable_t *le)
216 {
217 
218 	/* coverity[assert_side_effect] */
219 	KASSERT(!lockstat_dev_enabled);
220 
221 	lockstat_init_tables(le);
222 
223 	if ((le->le_flags & LE_CALLSITE) != 0)
224 		lockstat_csmask = (uintptr_t)-1LL;
225 	else
226 		lockstat_csmask = 0;
227 
228 	if ((le->le_flags & LE_LOCK) != 0)
229 		lockstat_lamask = (uintptr_t)-1LL;
230 	else
231 		lockstat_lamask = 0;
232 
233 	lockstat_csstart = le->le_csstart;
234 	lockstat_csend = le->le_csend;
235 	lockstat_lockstart = le->le_lockstart;
236 	lockstat_lockstart = le->le_lockstart;
237 	lockstat_lockend = le->le_lockend;
238 	membar_sync();
239 	getnanotime(&lockstat_stime);
240 	lockstat_dev_enabled = le->le_mask;
241 	LOCKSTAT_ENABLED_UPDATE();
242 }
243 
244 /*
245  * Stop collecting lock statistics.
246  */
247 int
248 lockstat_stop(lsdisable_t *ld)
249 {
250 	CPU_INFO_ITERATOR cii;
251 	struct cpu_info *ci;
252 	u_int cpuno, overflow;
253 	struct timespec ts;
254 	int error;
255 	lwp_t *l;
256 
257 	/* coverity[assert_side_effect] */
258 	KASSERT(lockstat_dev_enabled);
259 
260 	/*
261 	 * Set enabled false, force a write barrier, and wait for other CPUs
262 	 * to exit lockstat_event().
263 	 */
264 	lockstat_dev_enabled = 0;
265 	LOCKSTAT_ENABLED_UPDATE();
266 	getnanotime(&ts);
267 	tsleep(&lockstat_stop, PPAUSE, "lockstat", mstohz(10));
268 
269 	/*
270 	 * Did we run out of buffers while tracing?
271 	 */
272 	overflow = 0;
273 	for (CPU_INFO_FOREACH(cii, ci))
274 		overflow += ((lscpu_t *)ci->ci_lockstat)->lc_overflow;
275 
276 	if (overflow != 0) {
277 		error = EOVERFLOW;
278 		log(LOG_NOTICE, "lockstat: %d buffer allocations failed\n",
279 		    overflow);
280 	} else
281 		error = 0;
282 
283 	lockstat_init_tables(NULL);
284 
285 	/* Run through all LWPs and clear the slate for the next run. */
286 	mutex_enter(&proc_lock);
287 	LIST_FOREACH(l, &alllwp, l_list) {
288 		l->l_pfailaddr = 0;
289 		l->l_pfailtime = 0;
290 		l->l_pfaillock = 0;
291 	}
292 	mutex_exit(&proc_lock);
293 
294 	if (ld == NULL)
295 		return error;
296 
297 	/*
298 	 * Fill out the disable struct for the caller.
299 	 */
300 	timespecsub(&ts, &lockstat_stime, &ld->ld_time);
301 	ld->ld_size = lockstat_sizeb;
302 
303 	cpuno = 0;
304 	for (CPU_INFO_FOREACH(cii, ci)) {
305 		if (cpuno >= sizeof(ld->ld_freq) / sizeof(ld->ld_freq[0])) {
306 			log(LOG_WARNING, "lockstat: too many CPUs\n");
307 			break;
308 		}
309 		ld->ld_freq[cpuno++] = cpu_frequency(ci);
310 	}
311 
312 	return error;
313 }
314 
315 /*
316  * Allocate buffers for lockstat_start().
317  */
318 int
319 lockstat_alloc(lsenable_t *le)
320 {
321 	lsbuf_t *lb;
322 	size_t sz;
323 
324 	/* coverity[assert_side_effect] */
325 	KASSERT(!lockstat_dev_enabled);
326 	lockstat_free();
327 
328 	sz = sizeof(*lb) * le->le_nbufs;
329 
330 	lb = kmem_zalloc(sz, KM_SLEEP);
331 
332 	/* coverity[assert_side_effect] */
333 	KASSERT(!lockstat_dev_enabled);
334 	KASSERT(lockstat_baseb == NULL);
335 	lockstat_sizeb = sz;
336 	lockstat_baseb = lb;
337 
338 	return (0);
339 }
340 
341 /*
342  * Free allocated buffers after tracing has stopped.
343  */
344 void
345 lockstat_free(void)
346 {
347 
348 	/* coverity[assert_side_effect] */
349 	KASSERT(!lockstat_dev_enabled);
350 
351 	if (lockstat_baseb != NULL) {
352 		kmem_free(lockstat_baseb, lockstat_sizeb);
353 		lockstat_baseb = NULL;
354 	}
355 }
356 
357 /*
358  * Main entry point from lock primatives.
359  */
360 void
361 lockstat_event(uintptr_t lock, uintptr_t callsite, u_int flags, u_int count,
362 	       uint64_t cycles)
363 {
364 	lslist_t *ll;
365 	lscpu_t *lc;
366 	lsbuf_t *lb;
367 	u_int event;
368 	int s;
369 
370 #ifdef KDTRACE_HOOKS
371 	uint32_t id;
372 	CTASSERT((LS_NPROBES & (LS_NPROBES - 1)) == 0);
373 	if ((id = lockstat_probemap[LS_COMPRESS(flags)]) != 0)
374 		(*lockstat_probe_func)(id, lock, callsite, flags, count,
375 		    cycles);
376 #endif
377 
378 	if ((flags & lockstat_dev_enabled) != flags || count == 0)
379 		return;
380 	if (lock < lockstat_lockstart || lock > lockstat_lockend)
381 		return;
382 	if (callsite < lockstat_csstart || callsite > lockstat_csend)
383 		return;
384 
385 	callsite &= lockstat_csmask;
386 	lock &= lockstat_lamask;
387 
388 	/*
389 	 * Find the table for this lock+callsite pair, and try to locate a
390 	 * buffer with the same key.
391 	 */
392 	s = splhigh();
393 	lc = curcpu()->ci_lockstat;
394 	ll = &lc->lc_hash[LOCKSTAT_HASH(lock ^ callsite)];
395 	event = (flags & LB_EVENT_MASK) - 1;
396 
397 	LIST_FOREACH(lb, ll, lb_chain.list) {
398 		if (lb->lb_lock == lock && lb->lb_callsite == callsite)
399 			break;
400 	}
401 
402 	if (lb != NULL) {
403 		/*
404 		 * We found a record.  Move it to the front of the list, as
405 		 * we're likely to hit it again soon.
406 		 */
407 		if (lb != LIST_FIRST(ll)) {
408 			LIST_REMOVE(lb, lb_chain.list);
409 			LIST_INSERT_HEAD(ll, lb, lb_chain.list);
410 		}
411 		lb->lb_counts[event] += count;
412 		lb->lb_times[event] += cycles;
413 	} else if ((lb = SLIST_FIRST(&lc->lc_free)) != NULL) {
414 		/*
415 		 * Pinch a new buffer and fill it out.
416 		 */
417 		SLIST_REMOVE_HEAD(&lc->lc_free, lb_chain.slist);
418 		LIST_INSERT_HEAD(ll, lb, lb_chain.list);
419 		lb->lb_flags = (uint16_t)flags;
420 		lb->lb_lock = lock;
421 		lb->lb_callsite = callsite;
422 		lb->lb_counts[event] = count;
423 		lb->lb_times[event] = cycles;
424 	} else {
425 		/*
426 		 * We didn't find a buffer and there were none free.
427 		 * lockstat_stop() will notice later on and report the
428 		 * error.
429 		 */
430 		 lc->lc_overflow++;
431 	}
432 
433 	splx(s);
434 }
435 
436 /*
437  * Accept an open() on /dev/lockstat.
438  */
439 int
440 lockstat_open(dev_t dev, int flag, int mode, lwp_t *l)
441 {
442 
443 	if (!__cpu_simple_lock_try(&lockstat_lock))
444 		return EBUSY;
445 	lockstat_lwp = curlwp;
446 	return 0;
447 }
448 
449 /*
450  * Accept the last close() on /dev/lockstat.
451  */
452 int
453 lockstat_close(dev_t dev, int flag, int mode, lwp_t *l)
454 {
455 
456 	lockstat_lwp = NULL;
457 	if (lockstat_dev_enabled) {
458 		lockstat_stop(NULL);
459 		lockstat_free();
460 	}
461 	__cpu_simple_unlock(&lockstat_lock);
462 	return 0;
463 }
464 
465 /*
466  * Handle control operations.
467  */
468 int
469 lockstat_ioctl(dev_t dev, u_long cmd, void *data, int flag, lwp_t *l)
470 {
471 	lsenable_t *le;
472 	int error;
473 
474 	if (lockstat_lwp != curlwp)
475 		return EBUSY;
476 
477 	switch (cmd) {
478 	case IOC_LOCKSTAT_GVERSION:
479 		*(int *)data = LS_VERSION;
480 		error = 0;
481 		break;
482 
483 	case IOC_LOCKSTAT_ENABLE:
484 		le = (lsenable_t *)data;
485 
486 		if (!cpu_hascounter()) {
487 			error = ENODEV;
488 			break;
489 		}
490 		if (lockstat_dev_enabled) {
491 			error = EBUSY;
492 			break;
493 		}
494 
495 		/*
496 		 * Sanitize the arguments passed in and set up filtering.
497 		 */
498 		if (le->le_nbufs == 0) {
499 			le->le_nbufs = MIN(LOCKSTAT_DEFBUFS * ncpu,
500 			    LOCKSTAT_MAXBUFS);
501 		} else if (le->le_nbufs > LOCKSTAT_MAXBUFS ||
502 		    le->le_nbufs < LOCKSTAT_MINBUFS) {
503 			error = EINVAL;
504 			break;
505 		}
506 		if ((le->le_flags & LE_ONE_CALLSITE) == 0) {
507 			le->le_csstart = 0;
508 			le->le_csend = le->le_csstart - 1;
509 		}
510 		if ((le->le_flags & LE_ONE_LOCK) == 0) {
511 			le->le_lockstart = 0;
512 			le->le_lockend = le->le_lockstart - 1;
513 		}
514 		if ((le->le_mask & LB_EVENT_MASK) == 0)
515 			return EINVAL;
516 		if ((le->le_mask & LB_LOCK_MASK) == 0)
517 			return EINVAL;
518 
519 		/*
520 		 * Start tracing.
521 		 */
522 		if ((error = lockstat_alloc(le)) == 0)
523 			lockstat_start(le);
524 		break;
525 
526 	case IOC_LOCKSTAT_DISABLE:
527 		if (!lockstat_dev_enabled)
528 			error = EINVAL;
529 		else
530 			error = lockstat_stop((lsdisable_t *)data);
531 		break;
532 
533 	default:
534 		error = ENOTTY;
535 		break;
536 	}
537 
538 	return error;
539 }
540 
541 /*
542  * Copy buffers out to user-space.
543  */
544 int
545 lockstat_read(dev_t dev, struct uio *uio, int flag)
546 {
547 
548 	if (curlwp != lockstat_lwp || lockstat_dev_enabled)
549 		return EBUSY;
550 	return uiomove(lockstat_baseb, lockstat_sizeb, uio);
551 }
552