2006-01-27 23:13:26 +00:00
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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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2009-05-26 20:28:22 +00:00
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#include "opt_kdtrace.h"
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2007-03-22 16:09:23 +00:00
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#include "opt_no_adaptive_rwlocks.h"
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2006-01-27 23:13:26 +00:00
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#include <sys/param.h>
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#include <sys/ktr.h>
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2008-04-04 10:00:46 +00:00
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#include <sys/kernel.h>
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2006-01-27 23:13:26 +00:00
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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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2008-04-04 10:00:46 +00:00
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#include <sys/sysctl.h>
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2006-01-27 23:13:26 +00:00
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#include <sys/systm.h>
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#include <sys/turnstile.h>
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2007-07-20 08:43:42 +00:00
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2006-01-27 23:13:26 +00:00
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#include <machine/cpu.h>
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2007-03-22 16:09:23 +00:00
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#if defined(SMP) && !defined(NO_ADAPTIVE_RWLOCKS)
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#define ADAPTIVE_RWLOCKS
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#endif
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2008-04-04 10:00:46 +00:00
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#ifdef ADAPTIVE_RWLOCKS
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static int rowner_retries = 10;
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static int rowner_loops = 10000;
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SYSCTL_NODE(_debug, OID_AUTO, rwlock, CTLFLAG_RD, NULL, "rwlock debugging");
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SYSCTL_INT(_debug_rwlock, OID_AUTO, retry, CTLFLAG_RW, &rowner_retries, 0, "");
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SYSCTL_INT(_debug_rwlock, OID_AUTO, loops, CTLFLAG_RW, &rowner_loops, 0, "");
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#endif
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2006-01-27 23:13:26 +00:00
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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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2007-11-18 14:43:53 +00:00
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static void assert_rw(struct lock_object *lock, int what);
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2007-03-09 16:27:11 +00:00
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static void lock_rw(struct lock_object *lock, int how);
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2009-05-26 20:28:22 +00:00
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#ifdef KDTRACE_HOOKS
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static int owner_rw(struct lock_object *lock, struct thread **owner);
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#endif
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2007-03-09 16:27:11 +00:00
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static int unlock_rw(struct lock_object *lock);
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2006-01-27 23:13:26 +00:00
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struct lock_class lock_class_rw = {
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2007-03-09 16:04:44 +00:00
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.lc_name = "rw",
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.lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_UPGRADABLE,
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2007-11-18 14:43:53 +00:00
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.lc_assert = assert_rw,
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2006-01-27 23:13:26 +00:00
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#ifdef DDB
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2007-03-09 16:04:44 +00:00
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.lc_ddb_show = db_show_rwlock,
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2006-01-27 23:13:26 +00:00
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#endif
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2007-03-09 16:27:11 +00:00
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.lc_lock = lock_rw,
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.lc_unlock = unlock_rw,
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2009-05-26 20:28:22 +00:00
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#ifdef KDTRACE_HOOKS
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.lc_owner = owner_rw,
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#endif
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2006-01-27 23:13:26 +00:00
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};
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2006-04-17 21:11:01 +00:00
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/*
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* Return a pointer to the owning thread if the lock is write-locked or
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* NULL if the lock is unlocked or read-locked.
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*/
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#define rw_wowner(rw) \
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2006-01-27 23:13:26 +00:00
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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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2007-06-26 21:31:56 +00:00
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/*
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* Returns if a write owner is recursed. Write ownership is not assured
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* here and should be previously checked.
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*/
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#define rw_recursed(rw) ((rw)->rw_recurse != 0)
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/*
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* Return true if curthread helds the lock.
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*/
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#define rw_wlocked(rw) (rw_wowner((rw)) == curthread)
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2006-04-17 21:11:01 +00:00
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/*
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* Return a pointer to the owning thread for this lock who should receive
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* any priority lent by threads that block on this lock. Currently this
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* is identical to rw_wowner().
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*/
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#define rw_owner(rw) rw_wowner(rw)
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2006-01-27 23:13:26 +00:00
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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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2007-11-18 14:43:53 +00:00
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void
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assert_rw(struct lock_object *lock, int what)
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{
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rw_assert((struct rwlock *)lock, what);
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}
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2007-03-09 16:27:11 +00:00
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void
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lock_rw(struct lock_object *lock, int how)
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{
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struct rwlock *rw;
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rw = (struct rwlock *)lock;
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if (how)
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rw_wlock(rw);
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else
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rw_rlock(rw);
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}
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int
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unlock_rw(struct lock_object *lock)
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{
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struct rwlock *rw;
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rw = (struct rwlock *)lock;
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rw_assert(rw, RA_LOCKED | LA_NOTRECURSED);
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if (rw->rw_lock & RW_LOCK_READ) {
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rw_runlock(rw);
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return (0);
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} else {
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rw_wunlock(rw);
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return (1);
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}
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}
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2009-05-26 20:28:22 +00:00
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#ifdef KDTRACE_HOOKS
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int
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owner_rw(struct lock_object *lock, struct thread **owner)
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{
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struct rwlock *rw = (struct rwlock *)lock;
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uintptr_t x = rw->rw_lock;
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*owner = rw_wowner(rw);
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return ((x & RW_LOCK_READ) != 0 ? (RW_READERS(x) != 0) :
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(*owner != NULL));
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}
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#endif
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2006-01-27 23:13:26 +00:00
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void
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2007-06-26 21:31:56 +00:00
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rw_init_flags(struct rwlock *rw, const char *name, int opts)
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2006-01-27 23:13:26 +00:00
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{
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2007-06-26 21:31:56 +00:00
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int flags;
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MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET |
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RW_RECURSE)) == 0);
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2009-08-17 16:17:21 +00:00
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ASSERT_ATOMIC_LOAD_PTR(rw->rw_lock,
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("%s: rw_lock not aligned for %s: %p", __func__, name,
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&rw->rw_lock));
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2007-06-26 21:31:56 +00:00
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2009-06-02 13:03:35 +00:00
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flags = LO_UPGRADABLE;
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2007-06-26 21:31:56 +00:00
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if (opts & RW_DUPOK)
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flags |= LO_DUPOK;
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if (opts & RW_NOPROFILE)
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flags |= LO_NOPROFILE;
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if (!(opts & RW_NOWITNESS))
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flags |= LO_WITNESS;
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2009-06-02 13:03:35 +00:00
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if (opts & RW_RECURSE)
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flags |= LO_RECURSABLE;
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2007-06-26 21:31:56 +00:00
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if (opts & RW_QUIET)
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flags |= LO_QUIET;
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2006-01-27 23:13:26 +00:00
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rw->rw_lock = RW_UNLOCKED;
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2007-06-26 21:31:56 +00:00
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rw->rw_recurse = 0;
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lock_init(&rw->lock_object, &lock_class_rw, name, NULL, flags);
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2006-01-27 23:13:26 +00:00
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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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2010-03-24 19:21:26 +00:00
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KASSERT(rw->rw_lock == RW_UNLOCKED, ("rw lock %p not unlocked", rw));
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KASSERT(rw->rw_recurse == 0, ("rw lock %p still recursed", rw));
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2007-05-08 21:51:37 +00:00
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rw->rw_lock = RW_DESTROYED;
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2007-03-21 21:20:51 +00:00
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lock_destroy(&rw->lock_object);
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2006-01-27 23:13:26 +00:00
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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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2008-12-08 21:46:55 +00:00
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void
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rw_sysinit_flags(void *arg)
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{
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struct rw_args_flags *args = arg;
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rw_init_flags(args->ra_rw, args->ra_desc, args->ra_flags);
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}
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2007-02-26 19:05:13 +00:00
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int
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rw_wowned(struct rwlock *rw)
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{
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return (rw_wowner(rw) == curthread);
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}
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2006-01-27 23:13:26 +00:00
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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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2007-05-08 21:51:37 +00:00
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KASSERT(rw->rw_lock != RW_DESTROYED,
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("rw_wlock() of destroyed rwlock @ %s:%d", file, line));
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2007-03-21 21:20:51 +00:00
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WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file,
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2008-09-10 19:13:30 +00:00
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line, NULL);
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2006-01-27 23:13:26 +00:00
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__rw_wlock(rw, curthread, file, line);
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2007-06-26 21:31:56 +00:00
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LOCK_LOG_LOCK("WLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line);
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2007-03-21 21:20:51 +00:00
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WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line);
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2006-07-27 21:45:55 +00:00
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curthread->td_locks++;
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2006-01-27 23:13:26 +00:00
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}
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2008-04-01 20:31:55 +00:00
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int
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_rw_try_wlock(struct rwlock *rw, const char *file, int line)
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{
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int rval;
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KASSERT(rw->rw_lock != RW_DESTROYED,
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("rw_try_wlock() of destroyed rwlock @ %s:%d", file, line));
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2009-06-02 13:03:35 +00:00
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if (rw_wlocked(rw) &&
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(rw->lock_object.lo_flags & LO_RECURSABLE) != 0) {
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2008-04-01 20:31:55 +00:00
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rw->rw_recurse++;
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rval = 1;
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} else
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rval = atomic_cmpset_acq_ptr(&rw->rw_lock, RW_UNLOCKED,
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(uintptr_t)curthread);
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LOCK_LOG_TRY("WLOCK", &rw->lock_object, 0, rval, file, line);
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if (rval) {
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WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
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file, line);
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curthread->td_locks++;
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}
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return (rval);
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}
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2006-01-27 23:13:26 +00:00
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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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2007-05-08 21:51:37 +00:00
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KASSERT(rw->rw_lock != RW_DESTROYED,
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("rw_wunlock() of destroyed rwlock @ %s:%d", file, line));
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2006-01-27 23:13:26 +00:00
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_rw_assert(rw, RA_WLOCKED, file, line);
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2006-07-27 21:45:55 +00:00
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curthread->td_locks--;
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2007-03-21 21:20:51 +00:00
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WITNESS_UNLOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line);
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2007-06-26 21:31:56 +00:00
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LOCK_LOG_LOCK("WUNLOCK", &rw->lock_object, 0, rw->rw_recurse, file,
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line);
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if (!rw_recursed(rw))
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2009-05-26 20:28:22 +00:00
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LOCKSTAT_PROFILE_RELEASE_LOCK(LS_RW_WUNLOCK_RELEASE, rw);
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2006-01-27 23:13:26 +00:00
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__rw_wunlock(rw, curthread, file, line);
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}
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2008-02-06 01:02:13 +00:00
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/*
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* Determines whether a new reader can acquire a lock. Succeeds if the
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* reader already owns a read lock and the lock is locked for read to
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* prevent deadlock from reader recursion. Also succeeds if the lock
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* is unlocked and has no writer waiters or spinners. Failing otherwise
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* prioritizes writers before readers.
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*/
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#define RW_CAN_READ(_rw) \
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((curthread->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \
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(RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \
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RW_LOCK_READ)
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2006-01-27 23:13:26 +00:00
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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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Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
struct turnstile *ts;
|
2007-03-22 16:09:23 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
2006-04-18 18:27:54 +00:00
|
|
|
volatile struct thread *owner;
|
2008-04-04 10:00:46 +00:00
|
|
|
int spintries = 0;
|
|
|
|
int i;
|
2006-04-18 20:32:42 +00:00
|
|
|
#endif
|
2009-03-15 08:03:54 +00:00
|
|
|
#ifdef LOCK_PROFILING
|
2007-03-07 20:48:48 +00:00
|
|
|
uint64_t waittime = 0;
|
2007-02-27 06:42:05 +00:00
|
|
|
int contested = 0;
|
2009-03-15 08:03:54 +00:00
|
|
|
#endif
|
2008-02-06 01:02:13 +00:00
|
|
|
uintptr_t v;
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
uint64_t spin_cnt = 0;
|
|
|
|
uint64_t sleep_cnt = 0;
|
|
|
|
int64_t sleep_time = 0;
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
|
2007-05-08 21:51:37 +00:00
|
|
|
KASSERT(rw->rw_lock != RW_DESTROYED,
|
|
|
|
("rw_rlock() of destroyed rwlock @ %s:%d", file, line));
|
2006-04-17 21:11:01 +00:00
|
|
|
KASSERT(rw_wowner(rw) != curthread,
|
2006-01-27 23:13:26 +00:00
|
|
|
("%s (%s): wlock already held @ %s:%d", __func__,
|
2007-03-21 21:20:51 +00:00
|
|
|
rw->lock_object.lo_name, file, line));
|
2008-09-10 19:13:30 +00:00
|
|
|
WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL);
|
2006-01-27 23:13:26 +00:00
|
|
|
|
|
|
|
for (;;) {
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
spin_cnt++;
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
/*
|
|
|
|
* Handle the easy case. If no other thread has a write
|
|
|
|
* lock, then try to bump up the count of read locks. Note
|
|
|
|
* that we have to preserve the current state of the
|
|
|
|
* RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a
|
|
|
|
* read lock, then rw_lock must have changed, so restart
|
|
|
|
* the loop. Note that this handles the case of a
|
|
|
|
* completely unlocked rwlock since such a lock is encoded
|
|
|
|
* as a read lock with no waiters.
|
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
v = rw->rw_lock;
|
|
|
|
if (RW_CAN_READ(v)) {
|
2006-01-27 23:13:26 +00:00
|
|
|
/*
|
|
|
|
* The RW_LOCK_READ_WAITERS flag should only be set
|
2008-02-06 01:02:13 +00:00
|
|
|
* if the lock has been unlocked and write waiters
|
|
|
|
* were present.
|
2006-01-27 23:13:26 +00:00
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
if (atomic_cmpset_acq_ptr(&rw->rw_lock, v,
|
|
|
|
v + RW_ONE_READER)) {
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR4(KTR_LOCK,
|
|
|
|
"%s: %p succeed %p -> %p", __func__,
|
2008-02-06 01:02:13 +00:00
|
|
|
rw, (void *)v,
|
|
|
|
(void *)(v + RW_ONE_READER));
|
2006-01-27 23:13:26 +00:00
|
|
|
break;
|
|
|
|
}
|
|
|
|
continue;
|
|
|
|
}
|
2007-12-15 23:13:31 +00:00
|
|
|
lock_profile_obtain_lock_failed(&rw->lock_object,
|
|
|
|
&contested, &waittime);
|
2006-01-27 23:13:26 +00:00
|
|
|
|
2007-11-26 22:37:35 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
|
|
|
/*
|
|
|
|
* If the owner is running on another CPU, spin until
|
|
|
|
* the owner stops running or the state of the lock
|
|
|
|
* changes.
|
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
if ((v & RW_LOCK_READ) == 0) {
|
|
|
|
owner = (struct thread *)RW_OWNER(v);
|
|
|
|
if (TD_IS_RUNNING(owner)) {
|
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
|
|
|
CTR3(KTR_LOCK,
|
|
|
|
"%s: spinning on %p held by %p",
|
|
|
|
__func__, rw, owner);
|
|
|
|
while ((struct thread*)RW_OWNER(rw->rw_lock) ==
|
2009-05-26 20:28:22 +00:00
|
|
|
owner && TD_IS_RUNNING(owner)) {
|
2008-02-06 01:02:13 +00:00
|
|
|
cpu_spinwait();
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
spin_cnt++;
|
|
|
|
#endif
|
|
|
|
}
|
2008-02-06 01:02:13 +00:00
|
|
|
continue;
|
|
|
|
}
|
2008-04-04 10:00:46 +00:00
|
|
|
} else if (spintries < rowner_retries) {
|
|
|
|
spintries++;
|
|
|
|
for (i = 0; i < rowner_loops; i++) {
|
|
|
|
v = rw->rw_lock;
|
|
|
|
if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v))
|
|
|
|
break;
|
|
|
|
cpu_spinwait();
|
|
|
|
}
|
|
|
|
if (i != rowner_loops)
|
|
|
|
continue;
|
2007-11-26 22:37:35 +00:00
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
2006-01-27 23:13:26 +00:00
|
|
|
/*
|
|
|
|
* Okay, now it's the hard case. Some other thread already
|
2008-02-06 01:02:13 +00:00
|
|
|
* has a write lock or there are write waiters present,
|
|
|
|
* acquire the turnstile lock so we can begin the process
|
|
|
|
* of blocking.
|
2006-01-27 23:13:26 +00:00
|
|
|
*/
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
ts = turnstile_trywait(&rw->lock_object);
|
2006-01-27 23:13:26 +00:00
|
|
|
|
|
|
|
/*
|
|
|
|
* The lock might have been released while we spun, so
|
2008-02-06 01:02:13 +00:00
|
|
|
* recheck its state and restart the loop if needed.
|
2006-01-27 23:13:26 +00:00
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
v = rw->rw_lock;
|
|
|
|
if (RW_CAN_READ(v)) {
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_cancel(ts);
|
2006-01-27 23:13:26 +00:00
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
2007-11-26 22:37:35 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
|
|
|
/*
|
2009-05-29 13:56:34 +00:00
|
|
|
* The current lock owner might have started executing
|
|
|
|
* on another CPU (or the lock could have changed
|
|
|
|
* owners) while we were waiting on the turnstile
|
|
|
|
* chain lock. If so, drop the turnstile lock and try
|
|
|
|
* again.
|
2007-11-26 22:37:35 +00:00
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
if ((v & RW_LOCK_READ) == 0) {
|
|
|
|
owner = (struct thread *)RW_OWNER(v);
|
|
|
|
if (TD_IS_RUNNING(owner)) {
|
|
|
|
turnstile_cancel(ts);
|
|
|
|
continue;
|
|
|
|
}
|
2007-11-26 22:37:35 +00:00
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
2006-01-27 23:13:26 +00:00
|
|
|
/*
|
2008-02-06 01:02:13 +00:00
|
|
|
* The lock is held in write mode or it already has waiters.
|
2006-01-27 23:13:26 +00:00
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
MPASS(!RW_CAN_READ(v));
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If the RW_LOCK_READ_WAITERS flag is already set, then
|
|
|
|
* we can go ahead and block. If it is not set then try
|
|
|
|
* to set it. If we fail to set it drop the turnstile
|
|
|
|
* lock and restart the loop.
|
|
|
|
*/
|
|
|
|
if (!(v & RW_LOCK_READ_WAITERS)) {
|
|
|
|
if (!atomic_cmpset_ptr(&rw->rw_lock, v,
|
|
|
|
v | RW_LOCK_READ_WAITERS)) {
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_cancel(ts);
|
2006-04-17 21:11:01 +00:00
|
|
|
continue;
|
|
|
|
}
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-04-17 21:11:01 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p set read waiters flag",
|
|
|
|
__func__, rw);
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We were unable to acquire the lock and the read waiters
|
|
|
|
* flag is set, so we must block on the turnstile.
|
|
|
|
*/
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
|
|
|
|
rw);
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
sleep_time -= lockstat_nsecs();
|
|
|
|
#endif
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE);
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
sleep_time += lockstat_nsecs();
|
|
|
|
sleep_cnt++;
|
|
|
|
#endif
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
|
|
|
|
__func__, rw);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* TODO: acquire "owner of record" here. Here be turnstile dragons
|
|
|
|
* however. turnstiles don't like owners changing between calls to
|
|
|
|
* turnstile_wait() currently.
|
|
|
|
*/
|
2009-05-26 20:28:22 +00:00
|
|
|
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_RLOCK_ACQUIRE, rw, contested,
|
2007-12-15 23:13:31 +00:00
|
|
|
waittime, file, line);
|
2007-03-21 21:20:51 +00:00
|
|
|
LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line);
|
|
|
|
WITNESS_LOCK(&rw->lock_object, 0, file, line);
|
2006-07-27 21:45:55 +00:00
|
|
|
curthread->td_locks++;
|
2008-02-06 01:02:13 +00:00
|
|
|
curthread->td_rw_rlocks++;
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
if (sleep_time)
|
|
|
|
LOCKSTAT_RECORD1(LS_RW_RLOCK_BLOCK, rw, sleep_time);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Record only the loops spinning and not sleeping.
|
|
|
|
*/
|
|
|
|
if (spin_cnt > sleep_cnt)
|
|
|
|
LOCKSTAT_RECORD1(LS_RW_RLOCK_SPIN, rw, (spin_cnt - sleep_cnt));
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
|
2008-04-01 20:31:55 +00:00
|
|
|
int
|
|
|
|
_rw_try_rlock(struct rwlock *rw, const char *file, int line)
|
|
|
|
{
|
|
|
|
uintptr_t x;
|
|
|
|
|
|
|
|
for (;;) {
|
|
|
|
x = rw->rw_lock;
|
|
|
|
KASSERT(rw->rw_lock != RW_DESTROYED,
|
|
|
|
("rw_try_rlock() of destroyed rwlock @ %s:%d", file, line));
|
|
|
|
if (!(x & RW_LOCK_READ))
|
|
|
|
break;
|
|
|
|
if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, x + RW_ONE_READER)) {
|
|
|
|
LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 1, file,
|
|
|
|
line);
|
|
|
|
WITNESS_LOCK(&rw->lock_object, LOP_TRYLOCK, file, line);
|
|
|
|
curthread->td_locks++;
|
|
|
|
curthread->td_rw_rlocks++;
|
|
|
|
return (1);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 0, file, line);
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
|
2006-01-27 23:13:26 +00:00
|
|
|
void
|
|
|
|
_rw_runlock(struct rwlock *rw, const char *file, int line)
|
|
|
|
{
|
|
|
|
struct turnstile *ts;
|
2008-02-06 01:02:13 +00:00
|
|
|
uintptr_t x, v, queue;
|
2006-01-27 23:13:26 +00:00
|
|
|
|
2007-05-08 21:51:37 +00:00
|
|
|
KASSERT(rw->rw_lock != RW_DESTROYED,
|
|
|
|
("rw_runlock() of destroyed rwlock @ %s:%d", file, line));
|
2006-01-27 23:13:26 +00:00
|
|
|
_rw_assert(rw, RA_RLOCKED, file, line);
|
2006-07-27 21:45:55 +00:00
|
|
|
curthread->td_locks--;
|
2008-02-06 01:02:13 +00:00
|
|
|
curthread->td_rw_rlocks--;
|
2007-03-21 21:20:51 +00:00
|
|
|
WITNESS_UNLOCK(&rw->lock_object, 0, file, line);
|
|
|
|
LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line);
|
2006-01-27 23:13:26 +00:00
|
|
|
|
|
|
|
/* TODO: drop "owner of record" here. */
|
|
|
|
|
|
|
|
for (;;) {
|
|
|
|
/*
|
|
|
|
* See if there is more than one read lock held. If so,
|
|
|
|
* just drop one and return.
|
|
|
|
*/
|
|
|
|
x = rw->rw_lock;
|
|
|
|
if (RW_READERS(x) > 1) {
|
2009-09-30 13:26:31 +00:00
|
|
|
if (atomic_cmpset_rel_ptr(&rw->rw_lock, x,
|
2006-01-27 23:13:26 +00:00
|
|
|
x - RW_ONE_READER)) {
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR4(KTR_LOCK,
|
|
|
|
"%s: %p succeeded %p -> %p",
|
|
|
|
__func__, rw, (void *)x,
|
|
|
|
(void *)(x - RW_ONE_READER));
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
continue;
|
2007-03-07 20:48:48 +00:00
|
|
|
}
|
2006-01-27 23:13:26 +00:00
|
|
|
/*
|
|
|
|
* If there aren't any waiters for a write lock, then try
|
|
|
|
* to drop it quickly.
|
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
if (!(x & RW_LOCK_WAITERS)) {
|
|
|
|
MPASS((x & ~RW_LOCK_WRITE_SPINNER) ==
|
|
|
|
RW_READERS_LOCK(1));
|
2009-09-30 13:26:31 +00:00
|
|
|
if (atomic_cmpset_rel_ptr(&rw->rw_lock, x,
|
|
|
|
RW_UNLOCKED)) {
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p last succeeded",
|
|
|
|
__func__, rw);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
/*
|
2008-02-06 01:02:13 +00:00
|
|
|
* Ok, we know we have waiters and we think we are the
|
|
|
|
* last reader, so grab the turnstile lock.
|
2006-01-27 23:13:26 +00:00
|
|
|
*/
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_lock(&rw->lock_object);
|
2008-02-06 01:02:13 +00:00
|
|
|
v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
|
|
|
|
MPASS(v & RW_LOCK_WAITERS);
|
2006-01-27 23:13:26 +00:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Try to drop our lock leaving the lock in a unlocked
|
|
|
|
* state.
|
|
|
|
*
|
|
|
|
* If you wanted to do explicit lock handoff you'd have to
|
|
|
|
* do it here. You'd also want to use turnstile_signal()
|
|
|
|
* and you'd have to handle the race where a higher
|
|
|
|
* priority thread blocks on the write lock before the
|
|
|
|
* thread you wakeup actually runs and have the new thread
|
|
|
|
* "steal" the lock. For now it's a lot simpler to just
|
|
|
|
* wakeup all of the waiters.
|
|
|
|
*
|
|
|
|
* As above, if we fail, then another thread might have
|
|
|
|
* acquired a read lock, so drop the turnstile lock and
|
|
|
|
* restart.
|
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
x = RW_UNLOCKED;
|
|
|
|
if (v & RW_LOCK_WRITE_WAITERS) {
|
|
|
|
queue = TS_EXCLUSIVE_QUEUE;
|
|
|
|
x |= (v & RW_LOCK_READ_WAITERS);
|
|
|
|
} else
|
|
|
|
queue = TS_SHARED_QUEUE;
|
2009-09-30 13:26:31 +00:00
|
|
|
if (!atomic_cmpset_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v,
|
2008-02-06 01:02:13 +00:00
|
|
|
x)) {
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_unlock(&rw->lock_object);
|
2006-01-27 23:13:26 +00:00
|
|
|
continue;
|
|
|
|
}
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p last succeeded with waiters",
|
|
|
|
__func__, rw);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Ok. The lock is released and all that's left is to
|
|
|
|
* wake up the waiters. Note that the lock might not be
|
|
|
|
* free anymore, but in that case the writers will just
|
|
|
|
* block again if they run before the new lock holder(s)
|
|
|
|
* release the lock.
|
|
|
|
*/
|
2007-03-21 21:20:51 +00:00
|
|
|
ts = turnstile_lookup(&rw->lock_object);
|
2006-04-18 18:27:54 +00:00
|
|
|
MPASS(ts != NULL);
|
2008-02-06 01:02:13 +00:00
|
|
|
turnstile_broadcast(ts, queue);
|
2006-01-27 23:13:26 +00:00
|
|
|
turnstile_unpend(ts, TS_SHARED_LOCK);
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_unlock(&rw->lock_object);
|
2006-01-27 23:13:26 +00:00
|
|
|
break;
|
|
|
|
}
|
2009-05-26 20:28:22 +00:00
|
|
|
LOCKSTAT_PROFILE_RELEASE_LOCK(LS_RW_RUNLOCK_RELEASE, rw);
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* This function is called when we are unable to obtain a write lock on the
|
|
|
|
* 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)
|
|
|
|
{
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
struct turnstile *ts;
|
2007-03-22 16:09:23 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
2006-04-18 18:27:54 +00:00
|
|
|
volatile struct thread *owner;
|
2008-02-06 01:02:13 +00:00
|
|
|
int spintries = 0;
|
|
|
|
int i;
|
2006-04-18 20:32:42 +00:00
|
|
|
#endif
|
2008-02-06 01:02:13 +00:00
|
|
|
uintptr_t v, x;
|
2009-03-15 08:03:54 +00:00
|
|
|
#ifdef LOCK_PROFILING
|
|
|
|
uint64_t waittime = 0;
|
2007-07-20 08:43:42 +00:00
|
|
|
int contested = 0;
|
2009-03-15 08:03:54 +00:00
|
|
|
#endif
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
uint64_t spin_cnt = 0;
|
|
|
|
uint64_t sleep_cnt = 0;
|
|
|
|
int64_t sleep_time = 0;
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
|
2007-06-26 21:31:56 +00:00
|
|
|
if (rw_wlocked(rw)) {
|
2009-06-02 13:03:35 +00:00
|
|
|
KASSERT(rw->lock_object.lo_flags & LO_RECURSABLE,
|
2007-06-26 21:31:56 +00:00
|
|
|
("%s: recursing but non-recursive rw %s @ %s:%d\n",
|
|
|
|
__func__, rw->lock_object.lo_name, file, line));
|
|
|
|
rw->rw_recurse++;
|
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
|
|
|
CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
|
2007-03-21 21:20:51 +00:00
|
|
|
rw->lock_object.lo_name, (void *)rw->rw_lock, file, line);
|
2006-01-27 23:13:26 +00:00
|
|
|
|
|
|
|
while (!_rw_write_lock(rw, tid)) {
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
spin_cnt++;
|
|
|
|
#endif
|
2007-12-15 23:13:31 +00:00
|
|
|
lock_profile_obtain_lock_failed(&rw->lock_object,
|
|
|
|
&contested, &waittime);
|
2007-11-26 22:37:35 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
|
|
|
/*
|
|
|
|
* If the lock is write locked and the owner is
|
|
|
|
* running on another CPU, spin until the owner stops
|
|
|
|
* running or the state of the lock changes.
|
|
|
|
*/
|
|
|
|
v = rw->rw_lock;
|
|
|
|
owner = (struct thread *)RW_OWNER(v);
|
|
|
|
if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) {
|
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
|
|
|
CTR3(KTR_LOCK, "%s: spinning on %p held by %p",
|
|
|
|
__func__, rw, owner);
|
|
|
|
while ((struct thread*)RW_OWNER(rw->rw_lock) == owner &&
|
2009-05-26 20:28:22 +00:00
|
|
|
TD_IS_RUNNING(owner)) {
|
2007-11-26 22:37:35 +00:00
|
|
|
cpu_spinwait();
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
spin_cnt++;
|
|
|
|
#endif
|
|
|
|
}
|
2007-11-26 22:37:35 +00:00
|
|
|
continue;
|
|
|
|
}
|
2008-04-04 10:00:46 +00:00
|
|
|
if ((v & RW_LOCK_READ) && RW_READERS(v) &&
|
|
|
|
spintries < rowner_retries) {
|
2008-02-06 01:02:13 +00:00
|
|
|
if (!(v & RW_LOCK_WRITE_SPINNER)) {
|
|
|
|
if (!atomic_cmpset_ptr(&rw->rw_lock, v,
|
|
|
|
v | RW_LOCK_WRITE_SPINNER)) {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
spintries++;
|
2008-04-04 10:00:46 +00:00
|
|
|
for (i = 0; i < rowner_loops; i++) {
|
2008-02-06 01:02:13 +00:00
|
|
|
if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0)
|
|
|
|
break;
|
|
|
|
cpu_spinwait();
|
|
|
|
}
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
spin_cnt += rowner_loops - i;
|
|
|
|
#endif
|
2008-04-04 10:00:46 +00:00
|
|
|
if (i != rowner_loops)
|
2008-02-06 01:02:13 +00:00
|
|
|
continue;
|
|
|
|
}
|
2007-11-26 22:37:35 +00:00
|
|
|
#endif
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
ts = turnstile_trywait(&rw->lock_object);
|
2006-01-27 23:13:26 +00:00
|
|
|
v = rw->rw_lock;
|
|
|
|
|
2007-11-26 22:37:35 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
|
|
|
/*
|
2009-05-29 13:56:34 +00:00
|
|
|
* The current lock owner might have started executing
|
|
|
|
* on another CPU (or the lock could have changed
|
|
|
|
* owners) while we were waiting on the turnstile
|
|
|
|
* chain lock. If so, drop the turnstile lock and try
|
|
|
|
* again.
|
2007-11-26 22:37:35 +00:00
|
|
|
*/
|
|
|
|
if (!(v & RW_LOCK_READ)) {
|
|
|
|
owner = (struct thread *)RW_OWNER(v);
|
|
|
|
if (TD_IS_RUNNING(owner)) {
|
|
|
|
turnstile_cancel(ts);
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
/*
|
2008-05-27 00:27:50 +00:00
|
|
|
* Check for the waiters flags about this rwlock.
|
|
|
|
* If the lock was released, without maintain any pending
|
|
|
|
* waiters queue, simply try to acquire it.
|
|
|
|
* If a pending waiters queue is present, claim the lock
|
|
|
|
* ownership and maintain the pending queue.
|
2006-01-27 23:13:26 +00:00
|
|
|
*/
|
2008-02-06 01:02:13 +00:00
|
|
|
x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
|
|
|
|
if ((v & ~x) == RW_UNLOCKED) {
|
|
|
|
x &= ~RW_LOCK_WRITE_SPINNER;
|
|
|
|
if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) {
|
|
|
|
if (x)
|
|
|
|
turnstile_claim(ts);
|
|
|
|
else
|
|
|
|
turnstile_cancel(ts);
|
2006-01-27 23:13:26 +00:00
|
|
|
break;
|
|
|
|
}
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_cancel(ts);
|
2006-01-27 23:13:26 +00:00
|
|
|
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.
|
|
|
|
*/
|
2006-04-17 21:11:01 +00:00
|
|
|
if (!(v & RW_LOCK_WRITE_WAITERS)) {
|
|
|
|
if (!atomic_cmpset_ptr(&rw->rw_lock, v,
|
|
|
|
v | RW_LOCK_WRITE_WAITERS)) {
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_cancel(ts);
|
2006-04-17 21:11:01 +00:00
|
|
|
continue;
|
|
|
|
}
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-04-17 21:11:01 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p set write waiters flag",
|
|
|
|
__func__, rw);
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
/*
|
|
|
|
* We were unable to acquire the lock and the write waiters
|
|
|
|
* flag is set, so we must block on the turnstile.
|
|
|
|
*/
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
|
|
|
|
rw);
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
sleep_time -= lockstat_nsecs();
|
|
|
|
#endif
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE);
|
2009-05-26 20:28:22 +00:00
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
sleep_time += lockstat_nsecs();
|
|
|
|
sleep_cnt++;
|
|
|
|
#endif
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
|
|
|
|
__func__, rw);
|
2008-02-06 01:02:13 +00:00
|
|
|
#ifdef ADAPTIVE_RWLOCKS
|
|
|
|
spintries = 0;
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
2009-05-26 20:28:22 +00:00
|
|
|
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, rw, contested,
|
|
|
|
waittime, file, line);
|
|
|
|
#ifdef KDTRACE_HOOKS
|
|
|
|
if (sleep_time)
|
|
|
|
LOCKSTAT_RECORD1(LS_RW_WLOCK_BLOCK, rw, sleep_time);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Record only the loops spinning and not sleeping.
|
|
|
|
*/
|
|
|
|
if (spin_cnt > sleep_cnt)
|
|
|
|
LOCKSTAT_RECORD1(LS_RW_WLOCK_SPIN, rw, (spin_cnt - sleep_cnt));
|
|
|
|
#endif
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* 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;
|
|
|
|
|
2007-06-26 21:31:56 +00:00
|
|
|
if (rw_wlocked(rw) && rw_recursed(rw)) {
|
2008-02-06 01:02:13 +00:00
|
|
|
rw->rw_recurse--;
|
2007-06-26 21:31:56 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
|
|
|
CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2006-01-27 23:13:26 +00:00
|
|
|
KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS),
|
|
|
|
("%s: neither of the waiter flags are set", __func__));
|
|
|
|
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR2(KTR_LOCK, "%s: %p contested", __func__, rw);
|
|
|
|
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_lock(&rw->lock_object);
|
2007-03-21 21:20:51 +00:00
|
|
|
ts = turnstile_lookup(&rw->lock_object);
|
2006-01-27 23:13:26 +00:00
|
|
|
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.
|
|
|
|
*/
|
2006-04-18 18:27:54 +00:00
|
|
|
v = RW_UNLOCKED;
|
2008-02-07 06:16:54 +00:00
|
|
|
if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) {
|
2006-01-27 23:13:26 +00:00
|
|
|
queue = TS_EXCLUSIVE_QUEUE;
|
2008-02-07 06:16:54 +00:00
|
|
|
v |= (rw->rw_lock & RW_LOCK_READ_WAITERS);
|
|
|
|
} else
|
|
|
|
queue = TS_SHARED_QUEUE;
|
2006-04-18 18:27:54 +00:00
|
|
|
|
|
|
|
/* Wake up all waiters for the specific queue. */
|
2007-03-21 21:20:51 +00:00
|
|
|
if (LOCK_LOG_TEST(&rw->lock_object, 0))
|
2006-01-27 23:13:26 +00:00
|
|
|
CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw,
|
|
|
|
queue == TS_SHARED_QUEUE ? "read" : "write");
|
|
|
|
turnstile_broadcast(ts, queue);
|
|
|
|
atomic_store_rel_ptr(&rw->rw_lock, v);
|
|
|
|
turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_unlock(&rw->lock_object);
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
|
2006-04-19 21:06:52 +00:00
|
|
|
/*
|
|
|
|
* Attempt to do a non-blocking upgrade from a read lock to a write
|
|
|
|
* lock. This will only succeed if this thread holds a single read
|
|
|
|
* lock. Returns true if the upgrade succeeded and false otherwise.
|
|
|
|
*/
|
|
|
|
int
|
|
|
|
_rw_try_upgrade(struct rwlock *rw, const char *file, int line)
|
|
|
|
{
|
2008-02-06 01:02:13 +00:00
|
|
|
uintptr_t v, x, tid;
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
struct turnstile *ts;
|
2006-04-19 21:06:52 +00:00
|
|
|
int success;
|
|
|
|
|
2007-05-08 21:51:37 +00:00
|
|
|
KASSERT(rw->rw_lock != RW_DESTROYED,
|
|
|
|
("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line));
|
2006-04-19 21:06:52 +00:00
|
|
|
_rw_assert(rw, RA_RLOCKED, file, line);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Attempt to switch from one reader to a writer. If there
|
|
|
|
* are any write waiters, then we will have to lock the
|
|
|
|
* turnstile first to prevent races with another writer
|
|
|
|
* calling turnstile_wait() before we have claimed this
|
|
|
|
* turnstile. So, do the simple case of no waiters first.
|
|
|
|
*/
|
|
|
|
tid = (uintptr_t)curthread;
|
2008-02-06 01:02:13 +00:00
|
|
|
success = 0;
|
|
|
|
for (;;) {
|
|
|
|
v = rw->rw_lock;
|
|
|
|
if (RW_READERS(v) > 1)
|
|
|
|
break;
|
|
|
|
if (!(v & RW_LOCK_WAITERS)) {
|
|
|
|
success = atomic_cmpset_ptr(&rw->rw_lock, v, tid);
|
|
|
|
if (!success)
|
|
|
|
continue;
|
|
|
|
break;
|
|
|
|
}
|
2006-04-19 21:06:52 +00:00
|
|
|
|
2008-02-06 01:02:13 +00:00
|
|
|
/*
|
|
|
|
* Ok, we think we have waiters, so lock the turnstile.
|
|
|
|
*/
|
|
|
|
ts = turnstile_trywait(&rw->lock_object);
|
|
|
|
v = rw->rw_lock;
|
|
|
|
if (RW_READERS(v) > 1) {
|
|
|
|
turnstile_cancel(ts);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
/*
|
|
|
|
* Try to switch from one reader to a writer again. This time
|
|
|
|
* we honor the current state of the waiters flags.
|
|
|
|
* If we obtain the lock with the flags set, then claim
|
|
|
|
* ownership of the turnstile.
|
|
|
|
*/
|
|
|
|
x = rw->rw_lock & RW_LOCK_WAITERS;
|
|
|
|
success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x);
|
|
|
|
if (success) {
|
|
|
|
if (x)
|
|
|
|
turnstile_claim(ts);
|
|
|
|
else
|
|
|
|
turnstile_cancel(ts);
|
|
|
|
break;
|
|
|
|
}
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_cancel(ts);
|
2008-02-06 01:02:13 +00:00
|
|
|
}
|
2007-03-21 21:20:51 +00:00
|
|
|
LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line);
|
2008-02-06 01:02:13 +00:00
|
|
|
if (success) {
|
|
|
|
curthread->td_rw_rlocks--;
|
2007-03-21 21:20:51 +00:00
|
|
|
WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
|
2006-04-19 21:06:52 +00:00
|
|
|
file, line);
|
2009-05-26 20:28:22 +00:00
|
|
|
LOCKSTAT_RECORD0(LS_RW_TRYUPGRADE_UPGRADE, rw);
|
2008-02-06 01:02:13 +00:00
|
|
|
}
|
2006-04-19 21:06:52 +00:00
|
|
|
return (success);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Downgrade a write lock into a single read lock.
|
|
|
|
*/
|
|
|
|
void
|
|
|
|
_rw_downgrade(struct rwlock *rw, const char *file, int line)
|
|
|
|
{
|
|
|
|
struct turnstile *ts;
|
|
|
|
uintptr_t tid, v;
|
2008-02-06 01:02:13 +00:00
|
|
|
int rwait, wwait;
|
2006-04-19 21:06:52 +00:00
|
|
|
|
2007-05-08 21:51:37 +00:00
|
|
|
KASSERT(rw->rw_lock != RW_DESTROYED,
|
|
|
|
("rw_downgrade() of destroyed rwlock @ %s:%d", file, line));
|
2007-06-26 21:31:56 +00:00
|
|
|
_rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line);
|
|
|
|
#ifndef INVARIANTS
|
|
|
|
if (rw_recursed(rw))
|
|
|
|
panic("downgrade of a recursed lock");
|
|
|
|
#endif
|
2006-04-19 21:06:52 +00:00
|
|
|
|
2007-03-21 21:20:51 +00:00
|
|
|
WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line);
|
2006-04-19 21:06:52 +00:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Convert from a writer to a single reader. First we handle
|
|
|
|
* the easy case with no waiters. If there are any waiters, we
|
2008-02-06 01:02:13 +00:00
|
|
|
* lock the turnstile and "disown" the lock.
|
2006-04-19 21:06:52 +00:00
|
|
|
*/
|
|
|
|
tid = (uintptr_t)curthread;
|
|
|
|
if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1)))
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Ok, we think we have waiters, so lock the turnstile so we can
|
|
|
|
* read the waiter flags without any races.
|
|
|
|
*/
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_lock(&rw->lock_object);
|
2008-02-06 01:02:13 +00:00
|
|
|
v = rw->rw_lock & RW_LOCK_WAITERS;
|
|
|
|
rwait = v & RW_LOCK_READ_WAITERS;
|
|
|
|
wwait = v & RW_LOCK_WRITE_WAITERS;
|
|
|
|
MPASS(rwait | wwait);
|
2006-04-19 21:06:52 +00:00
|
|
|
|
|
|
|
/*
|
2008-02-06 01:02:13 +00:00
|
|
|
* Downgrade from a write lock while preserving waiters flag
|
|
|
|
* and give up ownership of the turnstile.
|
2006-04-19 21:06:52 +00:00
|
|
|
*/
|
2007-03-21 21:20:51 +00:00
|
|
|
ts = turnstile_lookup(&rw->lock_object);
|
2006-04-19 21:06:52 +00:00
|
|
|
MPASS(ts != NULL);
|
2008-02-06 01:02:13 +00:00
|
|
|
if (!wwait)
|
|
|
|
v &= ~RW_LOCK_READ_WAITERS;
|
|
|
|
atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v);
|
|
|
|
/*
|
|
|
|
* Wake other readers if there are no writers pending. Otherwise they
|
|
|
|
* won't be able to acquire the lock anyway.
|
|
|
|
*/
|
|
|
|
if (rwait && !wwait) {
|
2006-04-19 21:06:52 +00:00
|
|
|
turnstile_broadcast(ts, TS_SHARED_QUEUE);
|
|
|
|
turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
|
2008-02-06 01:02:13 +00:00
|
|
|
} else
|
2006-04-19 21:06:52 +00:00
|
|
|
turnstile_disown(ts);
|
Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
deadlocks that are possible with thread_lock().
- The turnstile lock order is defined as the exact opposite of the
lock order used with the sleep locks they represent. This allows us
to walk in reverse order in priority_propagate and this is the only
place we wish to multiply acquire turnstile locks.
- Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
- Change the turnstile interface to pass back turnstile pointers to the
consumers. This allows us to reduce some locking and makes it easier
to cancel turnstile assignment while the turnstile chain lock is held.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:51:44 +00:00
|
|
|
turnstile_chain_unlock(&rw->lock_object);
|
2006-04-19 21:06:52 +00:00
|
|
|
out:
|
2008-02-06 01:02:13 +00:00
|
|
|
curthread->td_rw_rlocks++;
|
2007-03-21 21:20:51 +00:00
|
|
|
LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line);
|
2009-05-26 20:28:22 +00:00
|
|
|
LOCKSTAT_RECORD0(LS_RW_DOWNGRADE_DOWNGRADE, rw);
|
2006-04-19 21:06:52 +00:00
|
|
|
}
|
|
|
|
|
2006-01-27 23:13:26 +00:00
|
|
|
#ifdef INVARIANT_SUPPORT
|
2006-02-01 04:18:07 +00:00
|
|
|
#ifndef INVARIANTS
|
2006-01-27 23:13:26 +00:00
|
|
|
#undef _rw_assert
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#endif
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/*
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* In the non-WITNESS case, rw_assert() can only detect that at least
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* *some* thread owns an rlock, but it cannot guarantee that *this*
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* thread owns an rlock.
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*/
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void
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_rw_assert(struct rwlock *rw, int what, const char *file, int line)
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{
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if (panicstr != NULL)
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return;
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switch (what) {
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case RA_LOCKED:
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2007-06-26 21:31:56 +00:00
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case RA_LOCKED | RA_RECURSED:
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case RA_LOCKED | RA_NOTRECURSED:
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2006-01-27 23:13:26 +00:00
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case RA_RLOCKED:
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#ifdef WITNESS
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2007-03-21 21:20:51 +00:00
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witness_assert(&rw->lock_object, what, file, line);
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2006-01-27 23:13:26 +00:00
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#else
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/*
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* If some other thread has a write lock or we have one
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* and are asserting a read lock, fail. Also, if no one
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* has a lock at all, fail.
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*/
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2006-01-30 19:25:52 +00:00
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if (rw->rw_lock == RW_UNLOCKED ||
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(!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED ||
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2006-04-17 21:11:01 +00:00
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rw_wowner(rw) != curthread)))
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2006-01-27 23:13:26 +00:00
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panic("Lock %s not %slocked @ %s:%d\n",
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2007-03-21 21:20:51 +00:00
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rw->lock_object.lo_name, (what == RA_RLOCKED) ?
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2006-01-27 23:13:26 +00:00
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"read " : "", file, line);
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2007-06-26 21:31:56 +00:00
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if (!(rw->rw_lock & RW_LOCK_READ)) {
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if (rw_recursed(rw)) {
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if (what & RA_NOTRECURSED)
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panic("Lock %s recursed @ %s:%d\n",
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rw->lock_object.lo_name, file,
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line);
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} else if (what & RA_RECURSED)
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panic("Lock %s not recursed @ %s:%d\n",
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rw->lock_object.lo_name, file, line);
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}
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2006-01-27 23:13:26 +00:00
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#endif
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break;
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case RA_WLOCKED:
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2007-06-26 21:31:56 +00:00
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case RA_WLOCKED | RA_RECURSED:
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case RA_WLOCKED | RA_NOTRECURSED:
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2006-04-17 21:11:01 +00:00
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if (rw_wowner(rw) != curthread)
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2006-01-27 23:13:26 +00:00
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panic("Lock %s not exclusively locked @ %s:%d\n",
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2007-03-21 21:20:51 +00:00
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rw->lock_object.lo_name, file, line);
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2007-06-26 21:31:56 +00:00
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if (rw_recursed(rw)) {
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if (what & RA_NOTRECURSED)
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panic("Lock %s recursed @ %s:%d\n",
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rw->lock_object.lo_name, file, line);
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} else if (what & RA_RECURSED)
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panic("Lock %s not recursed @ %s:%d\n",
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rw->lock_object.lo_name, file, line);
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2006-01-27 23:13:26 +00:00
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break;
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case RA_UNLOCKED:
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#ifdef WITNESS
|
2007-03-21 21:20:51 +00:00
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witness_assert(&rw->lock_object, what, file, line);
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2006-01-27 23:13:26 +00:00
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#else
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/*
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* If we hold a write lock fail. We can't reliably check
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* to see if we hold a read lock or not.
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*/
|
2006-04-17 21:11:01 +00:00
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if (rw_wowner(rw) == curthread)
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2006-01-27 23:13:26 +00:00
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panic("Lock %s exclusively locked @ %s:%d\n",
|
2007-03-21 21:20:51 +00:00
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rw->lock_object.lo_name, file, line);
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2006-01-27 23:13:26 +00:00
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#endif
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break;
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default:
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panic("Unknown rw lock assertion: %d @ %s:%d", what, file,
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|
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line);
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}
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}
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|
#endif /* INVARIANT_SUPPORT */
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|
#ifdef DDB
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void
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|
|
db_show_rwlock(struct lock_object *lock)
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|
|
{
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|
|
|
struct rwlock *rw;
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struct thread *td;
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|
rw = (struct rwlock *)lock;
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|
db_printf(" state: ");
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|
|
if (rw->rw_lock == RW_UNLOCKED)
|
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|
|
db_printf("UNLOCKED\n");
|
2007-05-08 21:51:37 +00:00
|
|
|
else if (rw->rw_lock == RW_DESTROYED) {
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|
|
db_printf("DESTROYED\n");
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|
return;
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|
|
} else if (rw->rw_lock & RW_LOCK_READ)
|
2007-03-13 16:51:27 +00:00
|
|
|
db_printf("RLOCK: %ju locks\n",
|
|
|
|
(uintmax_t)(RW_READERS(rw->rw_lock)));
|
2006-01-27 23:13:26 +00:00
|
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|
else {
|
2006-04-17 21:11:01 +00:00
|
|
|
td = rw_wowner(rw);
|
2006-01-27 23:13:26 +00:00
|
|
|
db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
|
2007-11-14 06:21:24 +00:00
|
|
|
td->td_tid, td->td_proc->p_pid, td->td_name);
|
2007-06-26 21:31:56 +00:00
|
|
|
if (rw_recursed(rw))
|
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|
|
db_printf(" recursed: %u\n", rw->rw_recurse);
|
2006-01-27 23:13:26 +00:00
|
|
|
}
|
|
|
|
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:
|
2007-03-12 20:10:29 +00:00
|
|
|
db_printf("readers and writers\n");
|
2006-01-27 23:13:26 +00:00
|
|
|
break;
|
|
|
|
default:
|
|
|
|
db_printf("none\n");
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
#endif
|