/*-
* Copyright (c) 2007 Stephan Uphoff <ups@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.
*/
/*
* Machine independent bits of reader/writer lock implementation.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_kdtrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/rmlock.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/turnstile.h>
#include <sys/lock_profile.h>
#include <machine/cpu.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#define RMPF_ONQUEUE 1
#define RMPF_SIGNAL 2
/*
* To support usage of rmlock in CVs and msleep yet another list for the
* priority tracker would be needed. Using this lock for cv and msleep also
* does not seem very useful
*/
static __inline void compiler_memory_barrier(void) {
__asm __volatile("":::"memory");
}
static void assert_rm(const struct lock_object *lock, int what);
static void lock_rm(struct lock_object *lock, int how);
#ifdef KDTRACE_HOOKS
static int owner_rm(const struct lock_object *lock, struct thread **owner);
#endif
static int unlock_rm(struct lock_object *lock);
struct lock_class lock_class_rm = {
.lc_name = "rm",
.lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
.lc_assert = assert_rm,
#if 0
#ifdef DDB
.lc_ddb_show = db_show_rwlock,
#endif
#endif
.lc_lock = lock_rm,
.lc_unlock = unlock_rm,
#ifdef KDTRACE_HOOKS
.lc_owner = owner_rm,
#endif
};
static void
assert_rm(const struct lock_object *lock, int what)
{
panic("assert_rm called");
}
static void
lock_rm(struct lock_object *lock, int how)
{
panic("lock_rm called");
}
static int
unlock_rm(struct lock_object *lock)
{
panic("unlock_rm called");
}
#ifdef KDTRACE_HOOKS
static int
owner_rm(const struct lock_object *lock, struct thread **owner)
{
panic("owner_rm called");
}
#endif
static struct mtx rm_spinlock;
MTX_SYSINIT(rm_spinlock, &rm_spinlock, "rm_spinlock", MTX_SPIN);
/*
* Add or remove tracker from per-cpu list.
*
* The per-cpu list can be traversed at any time in forward direction from an
* interrupt on the *local* cpu.
*/
static void inline
rm_tracker_add(struct pcpu *pc, struct rm_priotracker *tracker)
{
struct rm_queue *next;
/* Initialize all tracker pointers */
tracker->rmp_cpuQueue.rmq_prev = &pc->pc_rm_queue;
next = pc->pc_rm_queue.rmq_next;
tracker->rmp_cpuQueue.rmq_next = next;
/* rmq_prev is not used during froward traversal. */
next->rmq_prev = &tracker->rmp_cpuQueue;
/* Update pointer to first element. */
pc->pc_rm_queue.rmq_next = &tracker->rmp_cpuQueue;
}
static void inline
rm_tracker_remove(struct pcpu *pc, struct rm_priotracker *tracker)
{
struct rm_queue *next, *prev;
next = tracker->rmp_cpuQueue.rmq_next;
prev = tracker->rmp_cpuQueue.rmq_prev;
/* Not used during forward traversal. */
next->rmq_prev = prev;
/* Remove from list. */
prev->rmq_next = next;
}
static void
rm_cleanIPI(void *arg)
{
struct pcpu *pc;
struct rmlock *rm = arg;
struct rm_priotracker *tracker;
struct rm_queue *queue;
pc = pcpu_find(curcpu);
for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue;
queue = queue->rmq_next) {
tracker = (struct rm_priotracker *)queue;
if (tracker->rmp_rmlock == rm && tracker->rmp_flags == 0) {
tracker->rmp_flags = RMPF_ONQUEUE;
mtx_lock_spin(&rm_spinlock);
LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker,
rmp_qentry);
mtx_unlock_spin(&rm_spinlock);
}
}
}
CTASSERT((RM_SLEEPABLE & LO_CLASSFLAGS) == RM_SLEEPABLE);
void
rm_init_flags(struct rmlock *rm, const char *name, int opts)
{
int liflags;
liflags = 0;
if (!(opts & RM_NOWITNESS))
liflags |= LO_WITNESS;
if (opts & RM_RECURSE)
liflags |= LO_RECURSABLE;
rm->rm_writecpus = all_cpus;
LIST_INIT(&rm->rm_activeReaders);
if (opts & RM_SLEEPABLE) {
liflags |= RM_SLEEPABLE;
sx_init_flags(&rm->rm_lock_sx, "rmlock_sx", SX_RECURSE);
} else
mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx", MTX_NOWITNESS);
lock_init(&rm->lock_object, &lock_class_rm, name, NULL, liflags);
}
void
rm_init(struct rmlock *rm, const char *name)
{
rm_init_flags(rm, name, 0);
}
void
rm_destroy(struct rmlock *rm)
{
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
sx_destroy(&rm->rm_lock_sx);
else
mtx_destroy(&rm->rm_lock_mtx);
lock_destroy(&rm->lock_object);
}
int
rm_wowned(const struct rmlock *rm)
{
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
return (sx_xlocked(&rm->rm_lock_sx));
else
return (mtx_owned(&rm->rm_lock_mtx));
}
void
rm_sysinit(void *arg)
{
struct rm_args *args = arg;
rm_init(args->ra_rm, args->ra_desc);
}
void
rm_sysinit_flags(void *arg)
{
struct rm_args_flags *args = arg;
rm_init_flags(args->ra_rm, args->ra_desc, args->ra_opts);
}
static int
_rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
{
struct pcpu *pc;
struct rm_queue *queue;
struct rm_priotracker *atracker;
critical_enter();
pc = pcpu_find(curcpu);
/* Check if we just need to do a proper critical_exit. */
if (!CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)) {
critical_exit();
return (1);
}
/* Remove our tracker from the per-cpu list. */
rm_tracker_remove(pc, tracker);
/* Check to see if the IPI granted us the lock after all. */
if (tracker->rmp_flags) {
/* Just add back tracker - we hold the lock. */
rm_tracker_add(pc, tracker);
critical_exit();
return (1);
}
/*
* We allow readers to aquire a lock even if a writer is blocked if
* the lock is recursive and the reader already holds the lock.
*/
if ((rm->lock_object.lo_flags & LO_RECURSABLE) != 0) {
/*
* Just grant the lock if this thread already has a tracker
* for this lock on the per-cpu queue.
*/
for (queue = pc->pc_rm_queue.rmq_next;
queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
atracker = (struct rm_priotracker *)queue;
if ((atracker->rmp_rmlock == rm) &&
(atracker->rmp_thread == tracker->rmp_thread)) {
mtx_lock_spin(&rm_spinlock);
LIST_INSERT_HEAD(&rm->rm_activeReaders,
tracker, rmp_qentry);
tracker->rmp_flags = RMPF_ONQUEUE;
mtx_unlock_spin(&rm_spinlock);
rm_tracker_add(pc, tracker);
critical_exit();
return (1);
}
}
}
sched_unpin();
critical_exit();
if (trylock) {
if (rm->lock_object.lo_flags & RM_SLEEPABLE) {
if (!sx_try_xlock(&rm->rm_lock_sx))
return (0);
} else {
if (!mtx_trylock(&rm->rm_lock_mtx))
return (0);
}
} else {
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
sx_xlock(&rm->rm_lock_sx);
else
mtx_lock(&rm->rm_lock_mtx);
}
critical_enter();
pc = pcpu_find(curcpu);
CPU_CLR(pc->pc_cpuid, &rm->rm_writecpus);
rm_tracker_add(pc, tracker);
sched_pin();
critical_exit();
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
sx_xunlock(&rm->rm_lock_sx);
else
mtx_unlock(&rm->rm_lock_mtx);
return (1);
}
int
_rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
{
struct thread *td = curthread;
struct pcpu *pc;
if (SCHEDULER_STOPPED())
return (1);
tracker->rmp_flags = 0;
tracker->rmp_thread = td;
tracker->rmp_rmlock = rm;
td->td_critnest++; /* critical_enter(); */
compiler_memory_barrier();
pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
rm_tracker_add(pc, tracker);
sched_pin();
compiler_memory_barrier();
td->td_critnest--;
/*
* Fast path to combine two common conditions into a single
* conditional jump.
*/
if (0 == (td->td_owepreempt |
CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)))
return (1);
/* We do not have a read token and need to acquire one. */
return _rm_rlock_hard(rm, tracker, trylock);
}
static void
_rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker)
{
if (td->td_owepreempt) {
td->td_critnest++;
critical_exit();
}
if (!tracker->rmp_flags)
return;
mtx_lock_spin(&rm_spinlock);
LIST_REMOVE(tracker, rmp_qentry);
if (tracker->rmp_flags & RMPF_SIGNAL) {
struct rmlock *rm;
struct turnstile *ts;
rm = tracker->rmp_rmlock;
turnstile_chain_lock(&rm->lock_object);
mtx_unlock_spin(&rm_spinlock);
ts = turnstile_lookup(&rm->lock_object);
turnstile_signal(ts, TS_EXCLUSIVE_QUEUE);
turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
turnstile_chain_unlock(&rm->lock_object);
} else
mtx_unlock_spin(&rm_spinlock);
}
void
_rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker)
{
struct pcpu *pc;
struct thread *td = tracker->rmp_thread;
if (SCHEDULER_STOPPED())
return;
td->td_critnest++; /* critical_enter(); */
pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
rm_tracker_remove(pc, tracker);
td->td_critnest--;
sched_unpin();
if (0 == (td->td_owepreempt | tracker->rmp_flags))
return;
_rm_unlock_hard(td, tracker);
}
void
_rm_wlock(struct rmlock *rm)
{
struct rm_priotracker *prio;
struct turnstile *ts;
cpuset_t readcpus;
if (SCHEDULER_STOPPED())
return;
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
sx_xlock(&rm->rm_lock_sx);
else
mtx_lock(&rm->rm_lock_mtx);
if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) {
/* Get all read tokens back */
readcpus = all_cpus;
CPU_NAND(&readcpus, &rm->rm_writecpus);
rm->rm_writecpus = all_cpus;
/*
* Assumes rm->rm_writecpus update is visible on other CPUs
* before rm_cleanIPI is called.
*/
#ifdef SMP
smp_rendezvous_cpus(readcpus,
smp_no_rendevous_barrier,
rm_cleanIPI,
smp_no_rendevous_barrier,
rm);
#else
rm_cleanIPI(rm);
#endif
mtx_lock_spin(&rm_spinlock);
while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) {
ts = turnstile_trywait(&rm->lock_object);
prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL;
mtx_unlock_spin(&rm_spinlock);
turnstile_wait(ts, prio->rmp_thread,
TS_EXCLUSIVE_QUEUE);
mtx_lock_spin(&rm_spinlock);
}
mtx_unlock_spin(&rm_spinlock);
}
}
void
_rm_wunlock(struct rmlock *rm)
{
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
sx_xunlock(&rm->rm_lock_sx);
else
mtx_unlock(&rm->rm_lock_mtx);
}
#ifdef LOCK_DEBUG
void _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
{
if (SCHEDULER_STOPPED())
return;
WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE,
file, line, NULL);
_rm_wlock(rm);
LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line);
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
WITNESS_LOCK(&rm->rm_lock_sx.lock_object, LOP_EXCLUSIVE,
file, line);
else
WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
curthread->td_locks++;
}
void
_rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
{
if (SCHEDULER_STOPPED())
return;
curthread->td_locks--;
if (rm->lock_object.lo_flags & RM_SLEEPABLE)
WITNESS_UNLOCK(&rm->rm_lock_sx.lock_object, LOP_EXCLUSIVE,
file, line);
else
WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line);
_rm_wunlock(rm);
}
int
_rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
int trylock, const char *file, int line)
{
if (SCHEDULER_STOPPED())
return (1);
if (!trylock && (rm->lock_object.lo_flags & RM_SLEEPABLE))
WITNESS_CHECKORDER(&rm->rm_lock_sx.lock_object, LOP_NEWORDER,
file, line, NULL);
WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line, NULL);
if (_rm_rlock(rm, tracker, trylock)) {
LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file, line);
WITNESS_LOCK(&rm->lock_object, 0, file, line);
curthread->td_locks++;
return (1);
}
return (0);
}
void
_rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
const char *file, int line)
{
if (SCHEDULER_STOPPED())
return;
curthread->td_locks--;
WITNESS_UNLOCK(&rm->lock_object, 0, file, line);
LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line);
_rm_runlock(rm, tracker);
}
#else
/*
* Just strip out file and line arguments if no lock debugging is enabled in
* the kernel - we are called from a kernel module.
*/
void
_rm_wlock_debug(struct rmlock *rm, const char *file, int line)
{
_rm_wlock(rm);
}
void
_rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
{
_rm_wunlock(rm);
}
int
_rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
int trylock, const char *file, int line)
{
return _rm_rlock(rm, tracker, trylock);
}
void
_rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
const char *file, int line)
{
_rm_runlock(rm, tracker);
}
#endif
