diff options
Diffstat (limited to 'sys/kern/kern_rmlock.c')
| -rw-r--r-- | sys/kern/kern_rmlock.c | 613 |
1 files changed, 613 insertions, 0 deletions
diff --git a/sys/kern/kern_rmlock.c b/sys/kern/kern_rmlock.c new file mode 100644 index 0000000..30400b1 --- /dev/null +++ b/sys/kern/kern_rmlock.c @@ -0,0 +1,613 @@ +/*- + * 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 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_membar(); + + pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */ + + rm_tracker_add(pc, tracker); + + sched_pin(); + + __compiler_membar(); + + 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; + + KASSERT(!TD_IS_IDLETHREAD(curthread), + ("rm_wlock() by idle thread %p on rmlock %s @ %s:%d", + curthread, rm->lock_object.lo_name, file, line)); + 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); + + KASSERT(!TD_IS_IDLETHREAD(curthread), + ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d", + curthread, rm->lock_object.lo_name, file, line)); + 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 |
