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freebsd-dev/sys/kern/subr_lock.c
Kip Macy aa077979f6 Bug fix for obscenely large wait times on uncontested locks 
if waittime was zero (the lock was uncontested) l->lpo_waittime
in the hash table would not get initialized.

Inspection prompted by questions from: Attilio Rao
2006-12-04 22:15:50 +00:00

411 lines
14 KiB
C
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/*-
* Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* This module holds the global variables and functions used to maintain
* lock_object structures.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_mprof.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ktr.h>
#include <sys/linker_set.h>
#include <sys/lock.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include <sys/lock_profile.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
CTASSERT(LOCK_CLASS_MAX == 15);
struct lock_class *lock_classes[LOCK_CLASS_MAX + 1] = {
&lock_class_mtx_spin,
&lock_class_mtx_sleep,
&lock_class_sx,
&lock_class_rw,
&lock_class_lockmgr,
};
#ifdef LOCK_PROFILING
#include <machine/cpufunc.h>
SYSCTL_NODE(_debug, OID_AUTO, lock, CTLFLAG_RD, NULL, "lock debugging");
SYSCTL_NODE(_debug_lock, OID_AUTO, prof, CTLFLAG_RD, NULL, "lock profiling");
int lock_prof_enable = 0;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, enable, CTLFLAG_RW,
&lock_prof_enable, 0, "Enable lock profiling");
/*
* lprof_buf is a static pool of profiling records to avoid possible
* reentrance of the memory allocation functions.
*
* Note: NUM_LPROF_BUFFERS must be smaller than LPROF_HASH_SIZE.
*/
struct lock_prof lprof_buf[LPROF_HASH_SIZE];
static int allocated_lprof_buf;
struct mtx lprof_locks[LPROF_LOCK_SIZE];
/* SWAG: sbuf size = avg stat. line size * number of locks */
#define LPROF_SBUF_SIZE 256 * 400
static int lock_prof_acquisitions;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, acquisitions, CTLFLAG_RD,
&lock_prof_acquisitions, 0, "Number of lock acquistions recorded");
static int lock_prof_records;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, records, CTLFLAG_RD,
&lock_prof_records, 0, "Number of profiling records");
static int lock_prof_maxrecords = LPROF_HASH_SIZE;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, maxrecords, CTLFLAG_RD,
&lock_prof_maxrecords, 0, "Maximum number of profiling records");
static int lock_prof_rejected;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, rejected, CTLFLAG_RD,
&lock_prof_rejected, 0, "Number of rejected profiling records");
static int lock_prof_hashsize = LPROF_HASH_SIZE;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, hashsize, CTLFLAG_RD,
&lock_prof_hashsize, 0, "Hash size");
static int lock_prof_collisions = 0;
SYSCTL_INT(_debug_lock_prof, OID_AUTO, collisions, CTLFLAG_RD,
&lock_prof_collisions, 0, "Number of hash collisions");
#ifndef USE_CPU_NANOSECONDS
u_int64_t
nanoseconds(void)
{
struct timespec tv;
nanotime(&tv);
return (tv.tv_sec * (u_int64_t)1000000000 + tv.tv_nsec);
}
#endif
static int
dump_lock_prof_stats(SYSCTL_HANDLER_ARGS)
{
struct sbuf *sb;
int error, i;
static int multiplier = 1;
const char *p;
if (allocated_lprof_buf == 0)
return (SYSCTL_OUT(req, "No locking recorded",
sizeof("No locking recorded")));
retry_sbufops:
sb = sbuf_new(NULL, NULL, LPROF_SBUF_SIZE * multiplier, SBUF_FIXEDLEN);
sbuf_printf(sb, "\n%6s %12s %12s %11s %5s %5s %12s %12s %s\n",
"max", "total", "wait_total", "count", "avg", "wait_avg", "cnt_hold", "cnt_lock", "name");
for (i = 0; i < LPROF_HASH_SIZE; ++i) {
if (lprof_buf[i].name == NULL)
continue;
for (p = lprof_buf[i].file;
p != NULL && strncmp(p, "../", 3) == 0; p += 3)
/* nothing */ ;
sbuf_printf(sb, "%6ju %12ju %12ju %11ju %5ju %5ju %12ju %12ju %s:%d (%s:%s)\n",
lprof_buf[i].cnt_max / 1000,
lprof_buf[i].cnt_tot / 1000,
lprof_buf[i].cnt_wait / 1000,
lprof_buf[i].cnt_cur,
lprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 :
lprof_buf[i].cnt_tot / (lprof_buf[i].cnt_cur * 1000),
lprof_buf[i].cnt_cur == 0 ? (uintmax_t)0 :
lprof_buf[i].cnt_wait / (lprof_buf[i].cnt_cur * 1000),
lprof_buf[i].cnt_contest_holding,
lprof_buf[i].cnt_contest_locking,
p, lprof_buf[i].line,
lprof_buf[i].type,
lprof_buf[i].name);
if (sbuf_overflowed(sb)) {
sbuf_delete(sb);
multiplier++;
goto retry_sbufops;
}
}
sbuf_finish(sb);
error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
sbuf_delete(sb);
return (error);
}
static int
reset_lock_prof_stats(SYSCTL_HANDLER_ARGS)
{
int error, v;
if (allocated_lprof_buf == 0)
return (0);
v = 0;
error = sysctl_handle_int(oidp, &v, 0, req);
if (error)
return (error);
if (req->newptr == NULL)
return (error);
if (v == 0)
return (0);
bzero(lprof_buf, LPROF_HASH_SIZE*sizeof(*lprof_buf));
allocated_lprof_buf = 0;
return (0);
}
SYSCTL_PROC(_debug_lock_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, dump_lock_prof_stats, "A", "Lock profiling statistics");
SYSCTL_PROC(_debug_lock_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
NULL, 0, reset_lock_prof_stats, "I", "Reset lock profiling statistics");
#endif
void
lock_init(struct lock_object *lock, struct lock_class *class, const char *name,
const char *type, int flags)
{
int i;
/* Check for double-init and zero object. */
KASSERT(!lock_initalized(lock), ("lock \"%s\" %p already initialized",
name, lock));
/* Look up lock class to find its index. */
for (i = 0; i < LOCK_CLASS_MAX; i++)
if (lock_classes[i] == class) {
lock->lo_flags = i << LO_CLASSSHIFT;
break;
}
KASSERT(i < LOCK_CLASS_MAX, ("unknown lock class %p", class));
/* Initialize the lock object. */
lock->lo_name = name;
lock->lo_type = type != NULL ? type : name;
lock->lo_flags |= flags | LO_INITIALIZED;
LOCK_LOG_INIT(lock, 0);
WITNESS_INIT(lock);
}
void
lock_destroy(struct lock_object *lock)
{
KASSERT(lock_initalized(lock), ("lock %p is not initialized", lock));
WITNESS_DESTROY(lock);
LOCK_LOG_DESTROY(lock, 0);
lock->lo_flags &= ~LO_INITIALIZED;
}
#ifdef DDB
DB_SHOW_COMMAND(lock, db_show_lock)
{
struct lock_object *lock;
struct lock_class *class;
if (!have_addr)
return;
lock = (struct lock_object *)addr;
if (LO_CLASSINDEX(lock) > LOCK_CLASS_MAX) {
db_printf("Unknown lock class: %d\n", LO_CLASSINDEX(lock));
return;
}
class = LOCK_CLASS(lock);
db_printf(" class: %s\n", class->lc_name);
db_printf(" name: %s\n", lock->lo_name);
if (lock->lo_type && lock->lo_type != lock->lo_name)
db_printf(" type: %s\n", lock->lo_type);
class->lc_ddb_show(lock);
}
#endif
#ifdef LOCK_PROFILING
void _lock_profile_obtain_lock_success(struct lock_object *lo, uint64_t waittime, con\
st char *file, int line)
{
struct lock_profile_object *l = &lo->lo_profile_obj;
/* don't reset the timer when/if recursing */
if (l->lpo_acqtime == 0) {
l->lpo_filename = file;
l->lpo_lineno = line;
l->lpo_acqtime = nanoseconds();
if (waittime && (l->lpo_acqtime > waittime))
l->lpo_waittime = l->lpo_acqtime - waittime;
else
l->lpo_waittime = 0;
}
}
void _lock_profile_update_wait(struct lock_object *lo, uint64_t waitstart)
{
struct lock_profile_object *l = &lo->lo_profile_obj;
if (lock_prof_enable && waitstart) {
uint64_t now, waittime;
struct lock_prof *mpp;
u_int hash;
const char *p = l->lpo_filename;
int collision = 0;
now = nanoseconds();
if (now < waitstart)
return;
waittime = now - waitstart;
hash = (l->lpo_namehash * 31 * 31 + (uintptr_t)p * 31 + l->lpo_lineno) & LPROF_HASH_MASK;
mpp = &lprof_buf[hash];
while (mpp->name != NULL) {
if (mpp->line == l->lpo_lineno &&
mpp->file == p &&
mpp->namehash == l->lpo_namehash)
break;
/* If the lprof_hash entry is allocated to someone else, try the next one */
collision = 1;
CTR4(KTR_SPARE1, "Hash collision, %s:%d %s(%x)", mpp->file, mpp->line, mpp->name, mpp->namehash);
hash = (hash + 1) & LPROF_HASH_MASK;
mpp = &lprof_buf[hash];
}
if (mpp->name == NULL) {
int buf;
buf = atomic_fetchadd_int(&allocated_lprof_buf, 1);
/* Just exit if we cannot get a trace buffer */
if (buf >= LPROF_HASH_SIZE) {
++lock_prof_rejected;
return;
}
mpp->file = p;
mpp->line = l->lpo_lineno;
mpp->namehash = l->lpo_namehash;
mpp->type = l->lpo_type;
mpp->name = lo->lo_name;
if (collision)
++lock_prof_collisions;
/* We might have raced someone else but who cares, they'll try again next time */
++lock_prof_records;
}
LPROF_LOCK(hash);
mpp->cnt_wait += waittime;
LPROF_UNLOCK(hash);
}
}
void _lock_profile_release_lock(struct lock_object *lo)
{
struct lock_profile_object *l = &lo->lo_profile_obj;
if (l->lpo_acqtime && !(lo->lo_flags & LO_NOPROFILE)) {
const char *unknown = "(unknown)";
u_int64_t acqtime, now, waittime;
struct lock_prof *mpp;
u_int hash;
const char *p = l->lpo_filename;
int collision = 0;
now = nanoseconds();
acqtime = l->lpo_acqtime;
waittime = l->lpo_waittime;
if (now <= acqtime)
return;
if (p == NULL || *p == '\0')
p = unknown;
hash = (l->lpo_namehash * 31 * 31 + (uintptr_t)p * 31 + l->lpo_lineno) & LPROF_HASH_MASK;
CTR5(KTR_SPARE1, "Hashing %s(%x) %s:%d to %d", l->lpo_filename,
l->lpo_namehash, p, l->lpo_lineno, hash);
mpp = &lprof_buf[hash];
while (mpp->name != NULL) {
if (mpp->line == l->lpo_lineno &&
mpp->file == p &&
mpp->namehash == l->lpo_namehash)
break;
/* If the lprof_hash entry is allocated to someone
* else, try the next one
*/
collision = 1;
CTR4(KTR_SPARE1, "Hash collision, %s:%d %s(%x)", mpp->file,
mpp->line, mpp->name, mpp->namehash);
hash = (hash + 1) & LPROF_HASH_MASK;
mpp = &lprof_buf[hash];
}
if (mpp->name == NULL) {
int buf;
buf = atomic_fetchadd_int(&allocated_lprof_buf, 1);
/* Just exit if we cannot get a trace buffer */
if (buf >= LPROF_HASH_SIZE) {
++lock_prof_rejected;
return;
}
mpp->file = p;
mpp->line = l->lpo_lineno;
mpp->namehash = l->lpo_namehash;
mpp->type = l->lpo_type;
mpp->name = lo->lo_name;
if (collision)
++lock_prof_collisions;
/*
* We might have raced someone else but who cares,
* they'll try again next time
*/
++lock_prof_records;
}
LPROF_LOCK(hash);
/*
* Record if the lock has been held longer now than ever
* before.
*/
if (now - acqtime > mpp->cnt_max)
mpp->cnt_max = now - acqtime;
mpp->cnt_tot += now - acqtime;
mpp->cnt_wait += waittime;
mpp->cnt_cur++;
/*
* There's a small race, really we should cmpxchg
* 0 with the current value, but that would bill
* the contention to the wrong lock instance if
* it followed this also.
*/
mpp->cnt_contest_holding += l->lpo_contest_holding;
mpp->cnt_contest_locking += l->lpo_contest_locking;
LPROF_UNLOCK(hash);
}
l->lpo_acqtime = 0;
l->lpo_waittime = 0;
l->lpo_contest_locking = 0;
l->lpo_contest_holding = 0;
}
#endif
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