/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
*
* 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.
*
* 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/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/lock_profile.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#include <machine/cpufunc.h>
SDT_PROVIDER_DEFINE(lock);
SDT_PROBE_DEFINE1(lock, , , starvation, "u_int");
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_rm,
&lock_class_rm_sleepable,
&lock_class_rw,
&lock_class_lockmgr,
};
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(flags & LO_NEW || !lock_initialized(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_flags |= flags | LO_INITIALIZED;
LOCK_LOG_INIT(lock, 0);
WITNESS_INIT(lock, (type != NULL) ? type : name);
}
void
lock_destroy(struct lock_object *lock)
{
KASSERT(lock_initialized(lock), ("lock %p is not initialized", lock));
WITNESS_DESTROY(lock);
LOCK_LOG_DESTROY(lock, 0);
lock->lo_flags &= ~LO_INITIALIZED;
}
static SYSCTL_NODE(_debug, OID_AUTO, lock, CTLFLAG_RD, NULL, "lock debugging");
static SYSCTL_NODE(_debug_lock, OID_AUTO, delay, CTLFLAG_RD, NULL,
"lock delay");
static u_int __read_mostly starvation_limit = 131072;
SYSCTL_INT(_debug_lock_delay, OID_AUTO, starvation_limit, CTLFLAG_RW,
&starvation_limit, 0, "");
static u_int __read_mostly restrict_starvation = 0;
SYSCTL_INT(_debug_lock_delay, OID_AUTO, restrict_starvation, CTLFLAG_RW,
&restrict_starvation, 0, "");
void
lock_delay(struct lock_delay_arg *la)
{
struct lock_delay_config *lc = la->config;
u_int i;
la->delay <<= 1;
if (__predict_false(la->delay > lc->max))
la->delay = lc->max;
for (i = la->delay; i > 0; i--)
cpu_spinwait();
la->spin_cnt += la->delay;
if (__predict_false(la->spin_cnt > starvation_limit)) {
SDT_PROBE1(lock, , , starvation, la->delay);
if (restrict_starvation)
la->delay = lc->base;
}
}
static u_int
lock_roundup_2(u_int val)
{
u_int res;
for (res = 1; res <= val; res <<= 1)
continue;
return (res);
}
void
lock_delay_default_init(struct lock_delay_config *lc)
{
lc->base = 1;
lc->max = lock_roundup_2(mp_ncpus) * 256;
if (lc->max > 32678)
lc->max = 32678;
}
#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);
class->lc_ddb_show(lock);
}
#endif
#ifdef LOCK_PROFILING
/*
* One object per-thread for each lock the thread owns. Tracks individual
* lock instances.
*/
struct lock_profile_object {
LIST_ENTRY(lock_profile_object) lpo_link;
struct lock_object *lpo_obj;
const char *lpo_file;
int lpo_line;
uint16_t lpo_ref;
uint16_t lpo_cnt;
uint64_t lpo_acqtime;
uint64_t lpo_waittime;
u_int lpo_contest_locking;
};
/*
* One lock_prof for each (file, line, lock object) triple.
*/
struct lock_prof {
SLIST_ENTRY(lock_prof) link;
struct lock_class *class;
const char *file;
const char *name;
int line;
int ticks;
uintmax_t cnt_wait_max;
uintmax_t cnt_max;
uintmax_t cnt_tot;
uintmax_t cnt_wait;
uintmax_t cnt_cur;
uintmax_t cnt_contest_locking;
};
SLIST_HEAD(lphead, lock_prof);
#define LPROF_HASH_SIZE 4096
#define LPROF_HASH_MASK (LPROF_HASH_SIZE - 1)
#define LPROF_CACHE_SIZE 4096
/*
* Array of objects and profs for each type of object for each cpu. Spinlocks
* are handled separately because a thread may be preempted and acquire a
* spinlock while in the lock profiling code of a non-spinlock. In this way
* we only need a critical section to protect the per-cpu lists.
*/
struct lock_prof_type {
struct lphead lpt_lpalloc;
struct lpohead lpt_lpoalloc;
struct lphead lpt_hash[LPROF_HASH_SIZE];
struct lock_prof lpt_prof[LPROF_CACHE_SIZE];
struct lock_profile_object lpt_objs[LPROF_CACHE_SIZE];
};
struct lock_prof_cpu {
struct lock_prof_type lpc_types[2]; /* One for spin one for other. */
};
struct lock_prof_cpu *lp_cpu[MAXCPU];
volatile int __read_mostly lock_prof_enable;
static volatile int lock_prof_resetting;
#define LPROF_SBUF_SIZE 256
static int lock_prof_rejected;
static int lock_prof_skipspin;
static int lock_prof_skipcount;
#ifndef USE_CPU_NANOSECONDS
uint64_t
nanoseconds(void)
{
struct bintime bt;
uint64_t ns;
binuptime(&bt);
/* From bintime2timespec */
ns = bt.sec * (uint64_t)1000000000;
ns += ((uint64_t)1000000000 * (uint32_t)(bt.frac >> 32)) >> 32;
return (ns);
}
#endif
static void
lock_prof_init_type(struct lock_prof_type *type)
{
int i;
SLIST_INIT(&type->lpt_lpalloc);
LIST_INIT(&type->lpt_lpoalloc);
for (i = 0; i < LPROF_CACHE_SIZE; i++) {
SLIST_INSERT_HEAD(&type->lpt_lpalloc, &type->lpt_prof[i],
link);
LIST_INSERT_HEAD(&type->lpt_lpoalloc, &type->lpt_objs[i],
lpo_link);
}
}
static void
lock_prof_init(void *arg)
{
int cpu;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
lp_cpu[cpu] = malloc(sizeof(*lp_cpu[cpu]), M_DEVBUF,
M_WAITOK | M_ZERO);
lock_prof_init_type(&lp_cpu[cpu]->lpc_types[0]);
lock_prof_init_type(&lp_cpu[cpu]->lpc_types[1]);
}
}
SYSINIT(lockprof, SI_SUB_SMP, SI_ORDER_ANY, lock_prof_init, NULL);
static void
lock_prof_reset_wait(void)
{
/*
* Spin relinquishing our cpu so that quiesce_all_cpus may
* complete.
*/
while (lock_prof_resetting)
sched_relinquish(curthread);
}
static void
lock_prof_reset(void)
{
struct lock_prof_cpu *lpc;
int enabled, i, cpu;
/*
* We not only race with acquiring and releasing locks but also
* thread exit. To be certain that threads exit without valid head
* pointers they must see resetting set before enabled is cleared.
* Otherwise a lock may not be removed from a per-thread list due
* to disabled being set but not wait for reset() to remove it below.
*/
atomic_store_rel_int(&lock_prof_resetting, 1);
enabled = lock_prof_enable;
lock_prof_enable = 0;
quiesce_all_cpus("profreset", 0);
/*
* Some objects may have migrated between CPUs. Clear all links
* before we zero the structures. Some items may still be linked
* into per-thread lists as well.
*/
for (cpu = 0; cpu <= mp_maxid; cpu++) {
lpc = lp_cpu[cpu];
for (i = 0; i < LPROF_CACHE_SIZE; i++) {
LIST_REMOVE(&lpc->lpc_types[0].lpt_objs[i], lpo_link);
LIST_REMOVE(&lpc->lpc_types[1].lpt_objs[i], lpo_link);
}
}
for (cpu = 0; cpu <= mp_maxid; cpu++) {
lpc = lp_cpu[cpu];
bzero(lpc, sizeof(*lpc));
lock_prof_init_type(&lpc->lpc_types[0]);
lock_prof_init_type(&lpc->lpc_types[1]);
}
atomic_store_rel_int(&lock_prof_resetting, 0);
lock_prof_enable = enabled;
}
static void
lock_prof_output(struct lock_prof *lp, struct sbuf *sb)
{
const char *p;
for (p = lp->file; p != NULL && strncmp(p, "../", 3) == 0; p += 3);
sbuf_printf(sb,
"%8ju %9ju %11ju %11ju %11ju %6ju %6ju %2ju %6ju %s:%d (%s:%s)\n",
lp->cnt_max / 1000, lp->cnt_wait_max / 1000, lp->cnt_tot / 1000,
lp->cnt_wait / 1000, lp->cnt_cur,
lp->cnt_cur == 0 ? (uintmax_t)0 :
lp->cnt_tot / (lp->cnt_cur * 1000),
lp->cnt_cur == 0 ? (uintmax_t)0 :
lp->cnt_wait / (lp->cnt_cur * 1000),
(uintmax_t)0, lp->cnt_contest_locking,
p, lp->line, lp->class->lc_name, lp->name);
}
static void
lock_prof_sum(struct lock_prof *match, struct lock_prof *dst, int hash,
int spin, int t)
{
struct lock_prof_type *type;
struct lock_prof *l;
int cpu;
dst->file = match->file;
dst->line = match->line;
dst->class = match->class;
dst->name = match->name;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (lp_cpu[cpu] == NULL)
continue;
type = &lp_cpu[cpu]->lpc_types[spin];
SLIST_FOREACH(l, &type->lpt_hash[hash], link) {
if (l->ticks == t)
continue;
if (l->file != match->file || l->line != match->line ||
l->name != match->name)
continue;
l->ticks = t;
if (l->cnt_max > dst->cnt_max)
dst->cnt_max = l->cnt_max;
if (l->cnt_wait_max > dst->cnt_wait_max)
dst->cnt_wait_max = l->cnt_wait_max;
dst->cnt_tot += l->cnt_tot;
dst->cnt_wait += l->cnt_wait;
dst->cnt_cur += l->cnt_cur;
dst->cnt_contest_locking += l->cnt_contest_locking;
}
}
}
static void
lock_prof_type_stats(struct lock_prof_type *type, struct sbuf *sb, int spin,
int t)
{
struct lock_prof *l;
int i;
for (i = 0; i < LPROF_HASH_SIZE; ++i) {
SLIST_FOREACH(l, &type->lpt_hash[i], link) {
struct lock_prof lp = {};
if (l->ticks == t)
continue;
lock_prof_sum(l, &lp, i, spin, t);
lock_prof_output(&lp, sb);
}
}
}
static int
dump_lock_prof_stats(SYSCTL_HANDLER_ARGS)
{
struct sbuf *sb;
int error, cpu, t;
int enabled;
error = sysctl_wire_old_buffer(req, 0);
if (error != 0)
return (error);
sb = sbuf_new_for_sysctl(NULL, NULL, LPROF_SBUF_SIZE, req);
sbuf_printf(sb, "\n%8s %9s %11s %11s %11s %6s %6s %2s %6s %s\n",
"max", "wait_max", "total", "wait_total", "count", "avg", "wait_avg", "cnt_hold", "cnt_lock", "name");
enabled = lock_prof_enable;
lock_prof_enable = 0;
quiesce_all_cpus("profstat", 0);
t = ticks;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (lp_cpu[cpu] == NULL)
continue;
lock_prof_type_stats(&lp_cpu[cpu]->lpc_types[0], sb, 0, t);
lock_prof_type_stats(&lp_cpu[cpu]->lpc_types[1], sb, 1, t);
}
lock_prof_enable = enabled;
error = sbuf_finish(sb);
/* Output a trailing NUL. */
if (error == 0)
error = SYSCTL_OUT(req, "", 1);
sbuf_delete(sb);
return (error);
}
static int
enable_lock_prof(SYSCTL_HANDLER_ARGS)
{
int error, v;
v = lock_prof_enable;
error = sysctl_handle_int(oidp, &v, v, req);
if (error)
return (error);
if (req->newptr == NULL)
return (error);
if (v == lock_prof_enable)
return (0);
if (v == 1)
lock_prof_reset();
lock_prof_enable = !!v;
return (0);
}
static int
reset_lock_prof_stats(SYSCTL_HANDLER_ARGS)
{
int error, v;
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);
lock_prof_reset();
return (0);
}
static struct lock_prof *
lock_profile_lookup(struct lock_object *lo, int spin, const char *file,
int line)
{
const char *unknown = "(unknown)";
struct lock_prof_type *type;
struct lock_prof *lp;
struct lphead *head;
const char *p;
u_int hash;
p = file;
if (p == NULL || *p == '\0')
p = unknown;
hash = (uintptr_t)lo->lo_name * 31 + (uintptr_t)p * 31 + line;
hash &= LPROF_HASH_MASK;
type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
head = &type->lpt_hash[hash];
SLIST_FOREACH(lp, head, link) {
if (lp->line == line && lp->file == p &&
lp->name == lo->lo_name)
return (lp);
}
lp = SLIST_FIRST(&type->lpt_lpalloc);
if (lp == NULL) {
lock_prof_rejected++;
return (lp);
}
SLIST_REMOVE_HEAD(&type->lpt_lpalloc, link);
lp->file = p;
lp->line = line;
lp->class = LOCK_CLASS(lo);
lp->name = lo->lo_name;
SLIST_INSERT_HEAD(&type->lpt_hash[hash], lp, link);
return (lp);
}
static struct lock_profile_object *
lock_profile_object_lookup(struct lock_object *lo, int spin, const char *file,
int line)
{
struct lock_profile_object *l;
struct lock_prof_type *type;
struct lpohead *head;
head = &curthread->td_lprof[spin];
LIST_FOREACH(l, head, lpo_link)
if (l->lpo_obj == lo && l->lpo_file == file &&
l->lpo_line == line)
return (l);
type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
l = LIST_FIRST(&type->lpt_lpoalloc);
if (l == NULL) {
lock_prof_rejected++;
return (NULL);
}
LIST_REMOVE(l, lpo_link);
l->lpo_obj = lo;
l->lpo_file = file;
l->lpo_line = line;
l->lpo_cnt = 0;
LIST_INSERT_HEAD(head, l, lpo_link);
return (l);
}
void
lock_profile_obtain_lock_success(struct lock_object *lo, int contested,
uint64_t waittime, const char *file, int line)
{
static int lock_prof_count;
struct lock_profile_object *l;
int spin;
if (SCHEDULER_STOPPED())
return;
/* don't reset the timer when/if recursing */
if (!lock_prof_enable || (lo->lo_flags & LO_NOPROFILE))
return;
if (lock_prof_skipcount &&
(++lock_prof_count % lock_prof_skipcount) != 0)
return;
spin = (LOCK_CLASS(lo)->lc_flags & LC_SPINLOCK) ? 1 : 0;
if (spin && lock_prof_skipspin == 1)
return;
critical_enter();
/* Recheck enabled now that we're in a critical section. */
if (lock_prof_enable == 0)
goto out;
l = lock_profile_object_lookup(lo, spin, file, line);
if (l == NULL)
goto out;
l->lpo_cnt++;
if (++l->lpo_ref > 1)
goto out;
l->lpo_contest_locking = contested;
l->lpo_acqtime = nanoseconds();
if (waittime && (l->lpo_acqtime > waittime))
l->lpo_waittime = l->lpo_acqtime - waittime;
else
l->lpo_waittime = 0;
out:
critical_exit();
}
void
lock_profile_thread_exit(struct thread *td)
{
#ifdef INVARIANTS
struct lock_profile_object *l;
MPASS(curthread->td_critnest == 0);
#endif
/*
* If lock profiling was disabled we have to wait for reset to
* clear our pointers before we can exit safely.
*/
lock_prof_reset_wait();
#ifdef INVARIANTS
LIST_FOREACH(l, &td->td_lprof[0], lpo_link)
printf("thread still holds lock acquired at %s:%d\n",
l->lpo_file, l->lpo_line);
LIST_FOREACH(l, &td->td_lprof[1], lpo_link)
printf("thread still holds lock acquired at %s:%d\n",
l->lpo_file, l->lpo_line);
#endif
MPASS(LIST_FIRST(&td->td_lprof[0]) == NULL);
MPASS(LIST_FIRST(&td->td_lprof[1]) == NULL);
}
void
lock_profile_release_lock(struct lock_object *lo)
{
struct lock_profile_object *l;
struct lock_prof_type *type;
struct lock_prof *lp;
uint64_t curtime, holdtime;
struct lpohead *head;
int spin;
if (SCHEDULER_STOPPED())
return;
if (lo->lo_flags & LO_NOPROFILE)
return;
spin = (LOCK_CLASS(lo)->lc_flags & LC_SPINLOCK) ? 1 : 0;
head = &curthread->td_lprof[spin];
if (LIST_FIRST(head) == NULL)
return;
critical_enter();
/* Recheck enabled now that we're in a critical section. */
if (lock_prof_enable == 0 && lock_prof_resetting == 1)
goto out;
/*
* If lock profiling is not enabled we still want to remove the
* lpo from our queue.
*/
LIST_FOREACH(l, head, lpo_link)
if (l->lpo_obj == lo)
break;
if (l == NULL)
goto out;
if (--l->lpo_ref > 0)
goto out;
lp = lock_profile_lookup(lo, spin, l->lpo_file, l->lpo_line);
if (lp == NULL)
goto release;
curtime = nanoseconds();
if (curtime < l->lpo_acqtime)
goto release;
holdtime = curtime - l->lpo_acqtime;
/*
* Record if the lock has been held longer now than ever
* before.
*/
if (holdtime > lp->cnt_max)
lp->cnt_max = holdtime;
if (l->lpo_waittime > lp->cnt_wait_max)
lp->cnt_wait_max = l->lpo_waittime;
lp->cnt_tot += holdtime;
lp->cnt_wait += l->lpo_waittime;
lp->cnt_contest_locking += l->lpo_contest_locking;
lp->cnt_cur += l->lpo_cnt;
release:
LIST_REMOVE(l, lpo_link);
type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
LIST_INSERT_HEAD(&type->lpt_lpoalloc, l, lpo_link);
out:
critical_exit();
}
static SYSCTL_NODE(_debug_lock, OID_AUTO, prof, CTLFLAG_RD, NULL,
"lock profiling");
SYSCTL_INT(_debug_lock_prof, OID_AUTO, skipspin, CTLFLAG_RW,
&lock_prof_skipspin, 0, "Skip profiling on spinlocks.");
SYSCTL_INT(_debug_lock_prof, OID_AUTO, skipcount, CTLFLAG_RW,
&lock_prof_skipcount, 0, "Sample approximately every N lock acquisitions.");
SYSCTL_INT(_debug_lock_prof, OID_AUTO, rejected, CTLFLAG_RD,
&lock_prof_rejected, 0, "Number of rejected profiling records");
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");
SYSCTL_PROC(_debug_lock_prof, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
NULL, 0, enable_lock_prof, "I", "Enable lock profiling");
#endif
