Add a basic reader/writer lock implementation to the kernel. This
implementation is by no means perfect as far as some of the algorithms that it uses and the fact that it is missing some functionality (try locks and upgrades/downgrades are not there yet), however it does seem to work in my local testing. There is more detail in the comments in the code, but the short version follows. A reader/writer lock is very much like a regular mutex: it cannot be held across a voluntary sleep; it can be acquired in an interrupt thread; if the lock is held by a writer then the priority of any threads that block on the lock will be lent to the owner; the simple case lock operations all are done in a single atomic op. It also shares some similiarities with sx locks: it supports reader/writer semantics (multiple readers, but single writers); readers are allowed to recurse, but writers are not. We can extend this implementation further by either improving algorithms or adding new functionality, but this should at least give us a base to work with now. Reviewed by: arch (in theory) Tested on: i386 (4 cpu box with a kernel module that used 4 threads that randomly chose between read locks and write locks that ran w/o panicing for over a day solid. It usually panic'd within a few seconds when there were bugs during testing. :) The kernel module source is available on request.)
This commit is contained in:
parent
135161049e
commit
3f08bd8bce
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=154941
@ -1268,6 +1268,7 @@ kern/kern_poll.c optional device_polling
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kern/kern_proc.c standard
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kern/kern_prot.c standard
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kern/kern_resource.c standard
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kern/kern_rwlock.c standard
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kern/kern_sema.c standard
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kern/kern_shutdown.c standard
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kern/kern_sig.c standard
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@ -513,6 +513,7 @@ MUTEX_PROFILING opt_global.h
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MSIZE opt_global.h
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REGRESSION opt_global.h
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RESTARTABLE_PANICS opt_global.h
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RWLOCK_NOINLINE opt_global.h
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VFS_BIO_DEBUG opt_global.h
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# These are VM related options
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587
sys/kern/kern_rwlock.c
Normal file
587
sys/kern/kern_rwlock.c
Normal file
@ -0,0 +1,587 @@
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/*-
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* Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Machine independent bits of reader/writer lock implementation.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_ddb.h"
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#include <sys/param.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/rwlock.h>
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#include <sys/systm.h>
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#include <sys/turnstile.h>
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#include <machine/cpu.h>
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#ifdef DDB
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#include <ddb/ddb.h>
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static void db_show_rwlock(struct lock_object *lock);
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#endif
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struct lock_class lock_class_rw = {
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"rw",
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LC_SLEEPLOCK | LC_RECURSABLE /* | LC_UPGRADABLE */,
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#ifdef DDB
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db_show_rwlock
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#endif
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};
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#define rw_owner(rw) \
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((rw)->rw_lock & RW_LOCK_READ ? NULL : \
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(struct thread *)RW_OWNER((rw)->rw_lock))
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#ifndef INVARIANTS
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#define _rw_assert(rw, what, file, line)
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#endif
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void
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rw_init(struct rwlock *rw, const char *name)
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{
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rw->rw_lock = RW_UNLOCKED;
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lock_init(&rw->rw_object, &lock_class_rw, name, NULL, LO_WITNESS |
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LO_RECURSABLE /* | LO_UPGRADABLE */);
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}
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void
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rw_destroy(struct rwlock *rw)
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{
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KASSERT(rw->rw_lock == RW_UNLOCKED, ("rw lock not unlocked"));
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lock_destroy(&rw->rw_object);
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}
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void
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rw_sysinit(void *arg)
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{
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struct rw_args *args = arg;
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rw_init(args->ra_rw, args->ra_desc);
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}
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void
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_rw_wlock(struct rwlock *rw, const char *file, int line)
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{
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MPASS(curthread != NULL);
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KASSERT(rw_owner(rw) != curthread,
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("%s (%s): wlock already held @ %s:%d", __func__,
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rw->rw_object.lo_name, file, line));
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WITNESS_CHECKORDER(&rw->rw_object, LOP_NEWORDER | LOP_EXCLUSIVE, file,
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line);
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__rw_wlock(rw, curthread, file, line);
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LOCK_LOG_LOCK("WLOCK", &rw->rw_object, 0, 0, file, line);
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WITNESS_LOCK(&rw->rw_object, LOP_EXCLUSIVE, file, line);
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}
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void
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_rw_wunlock(struct rwlock *rw, const char *file, int line)
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{
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MPASS(curthread != NULL);
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_rw_assert(rw, RA_WLOCKED, file, line);
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WITNESS_UNLOCK(&rw->rw_object, LOP_EXCLUSIVE, file, line);
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LOCK_LOG_LOCK("WUNLOCK", &rw->rw_object, 0, 0, file, line);
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__rw_wunlock(rw, curthread, file, line);
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}
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void
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_rw_rlock(struct rwlock *rw, const char *file, int line)
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{
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uintptr_t x;
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KASSERT(rw_owner(rw) != curthread,
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("%s (%s): wlock already held @ %s:%d", __func__,
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rw->rw_object.lo_name, file, line));
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WITNESS_CHECKORDER(&rw->rw_object, LOP_NEWORDER, file, line);
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/*
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* Note that we don't make any attempt to try to block read
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* locks once a writer has blocked on the lock. The reason is
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* that we currently allow for read locks to recurse and we
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* don't keep track of all the holders of read locks. Thus, if
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* we were to block readers once a writer blocked and a reader
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* tried to recurse on their reader lock after a writer had
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* blocked we would end up in a deadlock since the reader would
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* be blocked on the writer, and the writer would be blocked
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* waiting for the reader to release its original read lock.
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*/
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for (;;) {
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/*
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* Handle the easy case. If no other thread has a write
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* lock, then try to bump up the count of read locks. Note
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* that we have to preserve the current state of the
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* RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a
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* read lock, then rw_lock must have changed, so restart
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* the loop. Note that this handles the case of a
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* completely unlocked rwlock since such a lock is encoded
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* as a read lock with no waiters.
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*/
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x = rw->rw_lock;
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if (x & RW_LOCK_READ) {
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/*
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* The RW_LOCK_READ_WAITERS flag should only be set
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* if another thread currently holds a write lock,
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* and in that case RW_LOCK_READ should be clear.
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*/
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MPASS((x & RW_LOCK_READ_WAITERS) == 0);
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if (atomic_cmpset_acq_ptr(&rw->rw_lock, x,
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x + RW_ONE_READER)) {
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR4(KTR_LOCK,
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"%s: %p succeed %p -> %p", __func__,
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rw, (void *)x,
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(void *)(x + RW_ONE_READER));
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break;
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}
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continue;
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}
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/*
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* Okay, now it's the hard case. Some other thread already
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* has a write lock, so acquire the turnstile lock so we can
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* begin the process of blocking.
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*/
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turnstile_lock(&rw->rw_object);
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/*
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* The lock might have been released while we spun, so
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* recheck its state and restart the loop if there is no
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* longer a write lock.
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*/
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x = rw->rw_lock;
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if (x & RW_LOCK_READ) {
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turnstile_release(&rw->rw_object);
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continue;
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}
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/*
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* Ok, it's still a write lock. If the RW_LOCK_READ_WAITERS
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* flag is already set, then we can go ahead and block. If
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* it is not set then try to set it. If we fail to set it
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* drop the turnstile lock and restart the loop.
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*/
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if (!(x & RW_LOCK_READ_WAITERS) &&
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!atomic_cmpset_ptr(&rw->rw_lock, x,
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x | RW_LOCK_READ_WAITERS)) {
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turnstile_release(&rw->rw_object);
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continue;
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}
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if (!(x & RW_LOCK_READ_WAITERS) &&
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LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR2(KTR_LOCK, "%s: %p set read waiters flag", __func__,
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rw);
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/*
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* We were unable to acquire the lock and the read waiters
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* flag is set, so we must block on the turnstile.
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*/
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
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rw);
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turnstile_wait(&rw->rw_object, rw_owner(rw), TS_SHARED_QUEUE);
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
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__func__, rw);
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}
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/*
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* TODO: acquire "owner of record" here. Here be turnstile dragons
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* however. turnstiles don't like owners changing between calls to
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* turnstile_wait() currently.
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*/
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LOCK_LOG_LOCK("RLOCK", &rw->rw_object, 0, 0, file, line);
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WITNESS_LOCK(&rw->rw_object, 0, file, line);
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}
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void
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_rw_runlock(struct rwlock *rw, const char *file, int line)
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{
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struct turnstile *ts;
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uintptr_t x;
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_rw_assert(rw, RA_RLOCKED, file, line);
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WITNESS_UNLOCK(&rw->rw_object, 0, file, line);
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LOCK_LOG_LOCK("RUNLOCK", &rw->rw_object, 0, 0, file, line);
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/* TODO: drop "owner of record" here. */
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for (;;) {
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/*
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* See if there is more than one read lock held. If so,
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* just drop one and return.
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*/
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x = rw->rw_lock;
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if (RW_READERS(x) > 1) {
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if (atomic_cmpset_ptr(&rw->rw_lock, x,
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x - RW_ONE_READER)) {
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR4(KTR_LOCK,
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"%s: %p succeeded %p -> %p",
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__func__, rw, (void *)x,
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(void *)(x - RW_ONE_READER));
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break;
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}
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continue;
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}
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/*
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* We should never have read waiters while at least one
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* thread holds a read lock. (See note above)
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*/
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KASSERT(!(x & RW_LOCK_READ_WAITERS),
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("%s: waiting readers", __func__));
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/*
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* If there aren't any waiters for a write lock, then try
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* to drop it quickly.
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*/
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if (!(x & RW_LOCK_WRITE_WAITERS)) {
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/*
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* There shouldn't be any flags set and we should
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* be the only read lock. If we fail to release
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* the single read lock, then another thread might
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* have just acquired a read lock, so go back up
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* to the multiple read locks case.
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*/
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MPASS(x == RW_READERS_LOCK(1));
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if (atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1),
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RW_UNLOCKED)) {
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR2(KTR_LOCK, "%s: %p last succeeded",
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__func__, rw);
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break;
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}
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continue;
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}
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/*
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* There should just be one reader with one or more
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* writers waiting.
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*/
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MPASS(x == (RW_READERS_LOCK(1) | RW_LOCK_WRITE_WAITERS));
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/*
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* Ok, we know we have a waiting writer and we think we
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* are the last reader, so grab the turnstile lock.
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*/
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turnstile_lock(&rw->rw_object);
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/*
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* Try to drop our lock leaving the lock in a unlocked
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* state.
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*
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* If you wanted to do explicit lock handoff you'd have to
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* do it here. You'd also want to use turnstile_signal()
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* and you'd have to handle the race where a higher
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* priority thread blocks on the write lock before the
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* thread you wakeup actually runs and have the new thread
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* "steal" the lock. For now it's a lot simpler to just
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* wakeup all of the waiters.
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*
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* As above, if we fail, then another thread might have
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* acquired a read lock, so drop the turnstile lock and
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* restart.
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*/
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if (!atomic_cmpset_ptr(&rw->rw_lock,
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RW_READERS_LOCK(1) | RW_LOCK_WRITE_WAITERS, RW_UNLOCKED)) {
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turnstile_release(&rw->rw_object);
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continue;
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}
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
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CTR2(KTR_LOCK, "%s: %p last succeeded with waiters",
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__func__, rw);
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/*
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* Ok. The lock is released and all that's left is to
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* wake up the waiters. Note that the lock might not be
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* free anymore, but in that case the writers will just
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* block again if they run before the new lock holder(s)
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* release the lock.
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*/
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ts = turnstile_lookup(&rw->rw_object);
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turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
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turnstile_unpend(ts, TS_SHARED_LOCK);
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break;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* This function is called when we are unable to obtain a write lock on the
|
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* first try. This means that at least one other thread holds either a
|
||||
* read or write lock.
|
||||
*/
|
||||
void
|
||||
_rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
|
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{
|
||||
uintptr_t v;
|
||||
|
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if (LOCK_LOG_TEST(&rw->rw_object, 0))
|
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CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
|
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rw->rw_object.lo_name, (void *)rw->rw_lock, file, line);
|
||||
|
||||
while (!_rw_write_lock(rw, tid)) {
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turnstile_lock(&rw->rw_object);
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||||
v = rw->rw_lock;
|
||||
|
||||
/*
|
||||
* If the lock was released while spinning on the
|
||||
* turnstile chain lock, try again.
|
||||
*/
|
||||
if (v == RW_UNLOCKED) {
|
||||
turnstile_release(&rw->rw_object);
|
||||
cpu_spinwait();
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||||
continue;
|
||||
}
|
||||
|
||||
/*
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||||
* If the lock was released by a writer with both readers
|
||||
* and writers waiting and a reader hasn't woken up and
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||||
* acquired the lock yet, rw_lock will be set to the
|
||||
* value RW_UNLOCKED | RW_LOCK_WRITE_WAITERS. If we see
|
||||
* that value, try to acquire it once. Note that we have
|
||||
* to preserve the RW_LOCK_WRITE_WAITERS flag as there are
|
||||
* other writers waiting still. If we fail, restart the
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||||
* loop.
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||||
*/
|
||||
if (v == (RW_UNLOCKED | RW_LOCK_WRITE_WAITERS)) {
|
||||
if (atomic_cmpset_acq_ptr(&rw->rw_lock,
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||||
RW_UNLOCKED | RW_LOCK_WRITE_WAITERS,
|
||||
tid | RW_LOCK_WRITE_WAITERS)) {
|
||||
turnstile_claim(&rw->rw_object);
|
||||
CTR2(KTR_LOCK, "%s: %p claimed by new writer",
|
||||
__func__, rw);
|
||||
break;
|
||||
}
|
||||
turnstile_release(&rw->rw_object);
|
||||
cpu_spinwait();
|
||||
continue;
|
||||
}
|
||||
|
||||
/*
|
||||
* If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to
|
||||
* set it. If we fail to set it, then loop back and try
|
||||
* again.
|
||||
*/
|
||||
if (!(v & RW_LOCK_WRITE_WAITERS) &&
|
||||
!atomic_cmpset_ptr(&rw->rw_lock, v,
|
||||
v | RW_LOCK_WRITE_WAITERS)) {
|
||||
turnstile_release(&rw->rw_object);
|
||||
cpu_spinwait();
|
||||
continue;
|
||||
}
|
||||
if (!(v & RW_LOCK_WRITE_WAITERS) &&
|
||||
LOCK_LOG_TEST(&rw->rw_object, 0))
|
||||
CTR2(KTR_LOCK, "%s: %p set write waiters flag",
|
||||
__func__, rw);
|
||||
|
||||
/* XXX: Adaptively spin if current wlock owner on another CPU? */
|
||||
|
||||
/*
|
||||
* We were unable to acquire the lock and the write waiters
|
||||
* flag is set, so we must block on the turnstile.
|
||||
*/
|
||||
if (LOCK_LOG_TEST(&rw->rw_object, 0))
|
||||
CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
|
||||
rw);
|
||||
turnstile_wait(&rw->rw_object, rw_owner(rw),
|
||||
TS_EXCLUSIVE_QUEUE);
|
||||
if (LOCK_LOG_TEST(&rw->rw_object, 0))
|
||||
CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
|
||||
__func__, rw);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* This function is called if the first try at releasing a write lock failed.
|
||||
* This means that one of the 2 waiter bits must be set indicating that at
|
||||
* least one thread is waiting on this lock.
|
||||
*/
|
||||
void
|
||||
_rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
|
||||
{
|
||||
struct turnstile *ts;
|
||||
uintptr_t v;
|
||||
int queue;
|
||||
|
||||
KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS),
|
||||
("%s: neither of the waiter flags are set", __func__));
|
||||
|
||||
if (LOCK_LOG_TEST(&rw->rw_object, 0))
|
||||
CTR2(KTR_LOCK, "%s: %p contested", __func__, rw);
|
||||
|
||||
turnstile_lock(&rw->rw_object);
|
||||
ts = turnstile_lookup(&rw->rw_object);
|
||||
|
||||
/* XXX: Adaptive fixup would be required here. */
|
||||
MPASS(ts != NULL);
|
||||
|
||||
/*
|
||||
* Use the same algo as sx locks for now. Prefer waking up shared
|
||||
* waiters if we have any over writers. This is probably not ideal.
|
||||
*
|
||||
* 'v' is the value we are going to write back to rw_lock. If we
|
||||
* have waiters on both queues, we need to preserve the state of
|
||||
* the waiter flag for the queue we don't wake up. For now this is
|
||||
* hardcoded for the algorithm mentioned above.
|
||||
*
|
||||
* In the case of both readers and writers waiting we wakeup the
|
||||
* readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a
|
||||
* new writer comes in before a reader it will claim the lock up
|
||||
* above. There is probably a potential priority inversion in
|
||||
* there that could be worked around either by waking both queues
|
||||
* of waiters or doing some complicated lock handoff gymnastics.
|
||||
*/
|
||||
if (rw->rw_lock & RW_LOCK_READ_WAITERS) {
|
||||
queue = TS_SHARED_QUEUE;
|
||||
v = RW_UNLOCKED | (rw->rw_lock & RW_LOCK_WRITE_WAITERS);
|
||||
} else {
|
||||
queue = TS_EXCLUSIVE_QUEUE;
|
||||
v = RW_UNLOCKED;
|
||||
}
|
||||
if (LOCK_LOG_TEST(&rw->rw_object, 0))
|
||||
CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw,
|
||||
queue == TS_SHARED_QUEUE ? "read" : "write");
|
||||
|
||||
/* Wake up all waiters for the specific queue. */
|
||||
turnstile_broadcast(ts, queue);
|
||||
atomic_store_rel_ptr(&rw->rw_lock, v);
|
||||
turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
|
||||
}
|
||||
|
||||
#ifdef INVARIANT_SUPPORT
|
||||
#ifndef INVARIANT_SUPPORT
|
||||
#undef _rw_assert
|
||||
#endif
|
||||
|
||||
/*
|
||||
* In the non-WITNESS case, rw_assert() can only detect that at least
|
||||
* *some* thread owns an rlock, but it cannot guarantee that *this*
|
||||
* thread owns an rlock.
|
||||
*/
|
||||
void
|
||||
_rw_assert(struct rwlock *rw, int what, const char *file, int line)
|
||||
{
|
||||
|
||||
if (panicstr != NULL)
|
||||
return;
|
||||
switch (what) {
|
||||
case RA_LOCKED:
|
||||
case RA_RLOCKED:
|
||||
#ifdef WITNESS
|
||||
witness_assert(&rw->rw_object, what, file, line);
|
||||
#else
|
||||
/*
|
||||
* If some other thread has a write lock or we have one
|
||||
* and are asserting a read lock, fail. Also, if no one
|
||||
* has a lock at all, fail.
|
||||
*/
|
||||
if (rw->rw_lock == RW_UNLOCKED ||
|
||||
!(rw->rw_lock & RW_LOCK_READ) && (what == RW_RLOCKED ||
|
||||
RW_OWNER(rw) != (uintptr_t)curthread))
|
||||
panic("Lock %s not %slocked @ %s:%d\n",
|
||||
rw->rw_object.lo_name, (what == RW_RLOCKED) ?
|
||||
"read " : "", file, line);
|
||||
#endif
|
||||
break;
|
||||
case RA_WLOCKED:
|
||||
if (rw_owner(rw) != curthread)
|
||||
panic("Lock %s not exclusively locked @ %s:%d\n",
|
||||
rw->rw_object.lo_name, file, line);
|
||||
break;
|
||||
case RA_UNLOCKED:
|
||||
#ifdef WITNESS
|
||||
witness_assert(&rw->rw_object, what, file, line);
|
||||
#else
|
||||
/*
|
||||
* If we hold a write lock fail. We can't reliably check
|
||||
* to see if we hold a read lock or not.
|
||||
*/
|
||||
if (rw_owner(rw) == curthread)
|
||||
panic("Lock %s exclusively locked @ %s:%d\n",
|
||||
rw->rw_object.lo_name, file, line);
|
||||
#endif
|
||||
break;
|
||||
default:
|
||||
panic("Unknown rw lock assertion: %d @ %s:%d", what, file,
|
||||
line);
|
||||
}
|
||||
}
|
||||
#endif /* INVARIANT_SUPPORT */
|
||||
|
||||
#ifdef DDB
|
||||
void
|
||||
db_show_rwlock(struct lock_object *lock)
|
||||
{
|
||||
struct rwlock *rw;
|
||||
struct thread *td;
|
||||
|
||||
rw = (struct rwlock *)lock;
|
||||
|
||||
db_printf(" state: ");
|
||||
if (rw->rw_lock == RW_UNLOCKED)
|
||||
db_printf("UNLOCKED\n");
|
||||
else if (rw->rw_lock & RW_LOCK_READ)
|
||||
db_printf("RLOCK: %d locks\n", RW_READERS(rw->rw_lock));
|
||||
else {
|
||||
td = rw_owner(rw);
|
||||
db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
|
||||
td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm);
|
||||
}
|
||||
db_printf(" waiters: ");
|
||||
switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) {
|
||||
case RW_LOCK_READ_WAITERS:
|
||||
db_printf("readers\n");
|
||||
break;
|
||||
case RW_LOCK_WRITE_WAITERS:
|
||||
db_printf("writers\n");
|
||||
break;
|
||||
case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS:
|
||||
db_printf("readers and waiters\n");
|
||||
break;
|
||||
default:
|
||||
db_printf("none\n");
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
#endif
|
@ -53,6 +53,7 @@ struct lock_class *lock_classes[LOCK_CLASS_MAX + 1] = {
|
||||
&lock_class_mtx_spin,
|
||||
&lock_class_mtx_sleep,
|
||||
&lock_class_sx,
|
||||
&lock_class_rw,
|
||||
};
|
||||
|
||||
void
|
||||
|
@ -211,6 +211,7 @@ struct lock_list_entry {
|
||||
extern struct lock_class lock_class_mtx_sleep;
|
||||
extern struct lock_class lock_class_mtx_spin;
|
||||
extern struct lock_class lock_class_sx;
|
||||
extern struct lock_class lock_class_rw;
|
||||
|
||||
extern struct lock_class *lock_classes[];
|
||||
|
||||
|
192
sys/sys/rwlock.h
Normal file
192
sys/sys/rwlock.h
Normal file
@ -0,0 +1,192 @@
|
||||
/*-
|
||||
* 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.
|
||||
*
|
||||
* $FreeBSD$
|
||||
*/
|
||||
|
||||
#ifndef _SYS_RWLOCK_H_
|
||||
#define _SYS_RWLOCK_H_
|
||||
|
||||
#include <sys/_lock.h>
|
||||
#include <sys/_rwlock.h>
|
||||
|
||||
#ifdef _KERNEL
|
||||
#include <machine/atomic.h>
|
||||
#endif
|
||||
|
||||
/*
|
||||
* The rw_lock field consists of several fields. The low bit indicates
|
||||
* if the lock is locked with a read (shared) or write (exclusive) lock.
|
||||
* A value of 0 indicates a write lock, and a value of 1 indicates a read
|
||||
* lock. Bit 1 is a boolean indicating if there are any threads waiting
|
||||
* for a read lock. Bit 2 is a boolean indicating if there are any threads
|
||||
* waiting for a write lock. The rest of the variable's definition is
|
||||
* dependent on the value of the first bit. For a write lock, it is a
|
||||
* pointer to the thread holding the lock, similar to the mtx_lock field of
|
||||
* mutexes. For read locks, it is a count of read locks that are held.
|
||||
*
|
||||
* When the lock is not locked by any thread, it is encoded as a read lock
|
||||
* with zero waiters.
|
||||
*
|
||||
* A note about memory barriers. Write locks need to use the same memory
|
||||
* barriers as mutexes: _acq when acquiring a write lock and _rel when
|
||||
* releasing a write lock. Read locks also need to use an _acq barrier when
|
||||
* acquiring a read lock. However, since read locks do not update any
|
||||
* locked data (modulo bugs of course), no memory barrier is needed to when
|
||||
* releasing a read lock.
|
||||
*/
|
||||
|
||||
#define RW_LOCK_READ 0x01
|
||||
#define RW_LOCK_READ_WAITERS 0x02
|
||||
#define RW_LOCK_WRITE_WAITERS 0x04
|
||||
#define RW_LOCK_FLAGMASK \
|
||||
(RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
|
||||
|
||||
#define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
|
||||
#define RW_READERS_SHIFT 3
|
||||
#define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
|
||||
#define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
|
||||
#define RW_ONE_READER (1 << RW_READERS_SHIFT)
|
||||
|
||||
#define RW_UNLOCKED RW_READERS_LOCK(0)
|
||||
|
||||
#ifdef _KERNEL
|
||||
|
||||
/* Very simple operations on rw_lock. */
|
||||
|
||||
/* Try to obtain a write lock once. */
|
||||
#define _rw_write_lock(rw, tid) \
|
||||
atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
|
||||
|
||||
/* Release a write lock quickly if there are no waiters. */
|
||||
#define _rw_write_unlock(rw, tid) \
|
||||
atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
|
||||
|
||||
/*
|
||||
* Full lock operations that are suitable to be inlined in non-debug
|
||||
* kernels. If the lock cannot be acquired or released trivially then
|
||||
* the work is deferred to another function.
|
||||
*/
|
||||
|
||||
/* Acquire a write lock. */
|
||||
#define __rw_wlock(rw, tid, file, line) do { \
|
||||
uintptr_t _tid = (uintptr_t)(tid); \
|
||||
\
|
||||
if (!_rw_write_lock((rw), _tid)) \
|
||||
_rw_wlock_hard((rw), _tid, (file), (line)); \
|
||||
} while (0)
|
||||
|
||||
/* Release a write lock. */
|
||||
#define __rw_wunlock(rw, tid, file, line) do { \
|
||||
uintptr_t _tid = (uintptr_t)(tid); \
|
||||
\
|
||||
if (!_rw_write_unlock((rw), _tid)) \
|
||||
_rw_wunlock_hard((rw), _tid, (file), (line)); \
|
||||
} while (0)
|
||||
|
||||
/*
|
||||
* Function prototypes. Routines that start with _ are not part of the
|
||||
* external API and should not be called directly. Wrapper macros should
|
||||
* be used instead.
|
||||
*/
|
||||
|
||||
void rw_init(struct rwlock *rw, const char *name);
|
||||
void rw_destroy(struct rwlock *rw);
|
||||
void rw_sysinit(void *arg);
|
||||
void _rw_wlock(struct rwlock *rw, const char *file, int line);
|
||||
void _rw_wunlock(struct rwlock *rw, const char *file, int line);
|
||||
void _rw_rlock(struct rwlock *rw, const char *file, int line);
|
||||
void _rw_runlock(struct rwlock *rw, const char *file, int line);
|
||||
void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
|
||||
int line);
|
||||
void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
|
||||
int line);
|
||||
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
|
||||
void _rw_assert(struct rwlock *rw, int what, const char *file, int line);
|
||||
#endif
|
||||
|
||||
/*
|
||||
* Public interface for lock operations.
|
||||
*
|
||||
* XXX: Missing try and upgrade/downgrade.
|
||||
*/
|
||||
|
||||
#ifndef LOCK_DEBUG
|
||||
#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
|
||||
#endif
|
||||
#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
|
||||
#define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
|
||||
#define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
|
||||
#else
|
||||
#define rw_wlock(rw) \
|
||||
__rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
|
||||
#define rw_wunlock(rw) \
|
||||
__rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
|
||||
#endif
|
||||
#define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
|
||||
#define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
|
||||
|
||||
#define rw_initialized(rw) lock_initalized(&(rw)->rw_object)
|
||||
|
||||
struct rw_args {
|
||||
struct rwlock *ra_rw;
|
||||
const char *ra_desc;
|
||||
};
|
||||
|
||||
#define RW_SYSINIT(name, rw, desc) \
|
||||
static struct rw_args name##_args = { \
|
||||
(rw), \
|
||||
(desc), \
|
||||
}; \
|
||||
SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
|
||||
rw_sysinit, &name##_args); \
|
||||
SYSUNINIT(name##_mtx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
|
||||
rw_destroy, (rw))
|
||||
|
||||
/*
|
||||
* The INVARIANTS-enabled rw_assert() functionality.
|
||||
*
|
||||
* The constants need to be defined for INVARIANT_SUPPORT infrastructure
|
||||
* support as _rw_assert() itself uses them and the latter implies that
|
||||
* _rw_assert() must build.
|
||||
*/
|
||||
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
|
||||
#define RA_LOCKED LA_LOCKED
|
||||
#define RA_RLOCKED LA_SLOCKED
|
||||
#define RA_WLOCKED LA_XLOCKED
|
||||
#define RA_UNLOCKED LA_UNLOCKED
|
||||
#endif
|
||||
|
||||
#ifdef INVARIANTS
|
||||
#define rw_assert(rw, what) _rw_assert((sx), (what), LOCK_FILE, LOCK_LINE)
|
||||
#else
|
||||
#define rw_assert(rw, what)
|
||||
#endif
|
||||
|
||||
#endif /* _KERNEL */
|
||||
#endif /* !_SYS_RWLOCK_H_ */
|
Loading…
Reference in New Issue
Block a user