freebsd-nq/module/zfs/zrlock.c

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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2014, 2015 by Delphix. All rights reserved.
* Copyright 2016 The MathWorks, Inc. All rights reserved.
*/
/*
* A Zero Reference Lock (ZRL) is a reference count that can lock out new
* references only when the count is zero and only without waiting if the count
* is not already zero. It is similar to a read-write lock in that it allows
* multiple readers and only a single writer, but it does not allow a writer to
* block while waiting for readers to exit, and therefore the question of
* reader/writer priority is moot (no WRWANT bit). Since the equivalent of
* rw_enter(&lock, RW_WRITER) is disallowed and only tryenter() is allowed, it
* is perfectly safe for the same reader to acquire the same lock multiple
* times. The fact that a ZRL is reentrant for readers (through multiple calls
* to zrl_add()) makes it convenient for determining whether something is
* actively referenced without the fuss of flagging lock ownership across
* function calls.
*/
#include <sys/zrlock.h>
#include <sys/trace_zfs.h>
/*
* A ZRL can be locked only while there are zero references, so ZRL_LOCKED is
* treated as zero references.
*/
#define ZRL_LOCKED -1
#define ZRL_DESTROYED -2
void
zrl_init(zrlock_t *zrl)
{
mutex_init(&zrl->zr_mtx, NULL, MUTEX_DEFAULT, NULL);
zrl->zr_refcount = 0;
cv_init(&zrl->zr_cv, NULL, CV_DEFAULT, NULL);
#ifdef ZFS_DEBUG
zrl->zr_owner = NULL;
zrl->zr_caller = NULL;
#endif
}
void
zrl_destroy(zrlock_t *zrl)
{
ASSERT0(zrl->zr_refcount);
mutex_destroy(&zrl->zr_mtx);
zrl->zr_refcount = ZRL_DESTROYED;
cv_destroy(&zrl->zr_cv);
}
void
zrl_add_impl(zrlock_t *zrl, const char *zc)
{
for (;;) {
uint32_t n = (uint32_t)zrl->zr_refcount;
while (n != ZRL_LOCKED) {
uint32_t cas = atomic_cas_32(
(uint32_t *)&zrl->zr_refcount, n, n + 1);
if (cas == n) {
ASSERT3S((int32_t)n, >=, 0);
#ifdef ZFS_DEBUG
if (zrl->zr_owner == curthread) {
DTRACE_PROBE3(zrlock__reentry,
zrlock_t *, zrl,
kthread_t *, curthread,
uint32_t, n);
}
zrl->zr_owner = curthread;
zrl->zr_caller = zc;
#endif
return;
}
n = cas;
}
mutex_enter(&zrl->zr_mtx);
while (zrl->zr_refcount == ZRL_LOCKED) {
cv_wait(&zrl->zr_cv, &zrl->zr_mtx);
}
mutex_exit(&zrl->zr_mtx);
}
}
void
zrl_remove(zrlock_t *zrl)
{
uint32_t n;
#ifdef ZFS_DEBUG
if (zrl->zr_owner == curthread) {
zrl->zr_owner = NULL;
zrl->zr_caller = NULL;
}
#endif
n = atomic_dec_32_nv((uint32_t *)&zrl->zr_refcount);
ASSERT3S((int32_t)n, >=, 0);
}
int
zrl_tryenter(zrlock_t *zrl)
{
uint32_t n = (uint32_t)zrl->zr_refcount;
if (n == 0) {
uint32_t cas = atomic_cas_32(
(uint32_t *)&zrl->zr_refcount, 0, ZRL_LOCKED);
if (cas == 0) {
#ifdef ZFS_DEBUG
ASSERT3P(zrl->zr_owner, ==, NULL);
zrl->zr_owner = curthread;
#endif
return (1);
}
}
ASSERT3S((int32_t)n, >, ZRL_DESTROYED);
return (0);
}
void
zrl_exit(zrlock_t *zrl)
{
ASSERT3S(zrl->zr_refcount, ==, ZRL_LOCKED);
mutex_enter(&zrl->zr_mtx);
#ifdef ZFS_DEBUG
ASSERT3P(zrl->zr_owner, ==, curthread);
zrl->zr_owner = NULL;
membar_producer(); /* make sure the owner store happens first */
#endif
zrl->zr_refcount = 0;
cv_broadcast(&zrl->zr_cv);
mutex_exit(&zrl->zr_mtx);
}
int
zrl_is_zero(zrlock_t *zrl)
{
ASSERT3S(zrl->zr_refcount, >, ZRL_DESTROYED);
return (zrl->zr_refcount <= 0);
}
int
zrl_is_locked(zrlock_t *zrl)
{
ASSERT3S(zrl->zr_refcount, >, ZRL_DESTROYED);
return (zrl->zr_refcount == ZRL_LOCKED);
}
#ifdef ZFS_DEBUG
kthread_t *
zrl_owner(zrlock_t *zrl)
{
return (zrl->zr_owner);
}
#endif
Update build system and packaging Minimal changes required to integrate the SPL sources in to the ZFS repository build infrastructure and packaging. Build system and packaging: * Renamed SPL_* autoconf m4 macros to ZFS_*. * Removed redundant SPL_* autoconf m4 macros. * Updated the RPM spec files to remove SPL package dependency. * The zfs package obsoletes the spl package, and the zfs-kmod package obsoletes the spl-kmod package. * The zfs-kmod-devel* packages were updated to add compatibility symlinks under /usr/src/spl-x.y.z until all dependent packages can be updated. They will be removed in a future release. * Updated copy-builtin script for in-kernel builds. * Updated DKMS package to include the spl.ko. * Updated stale AUTHORS file to include all contributors. * Updated stale COPYRIGHT and included the SPL as an exception. * Renamed README.markdown to README.md * Renamed OPENSOLARIS.LICENSE to LICENSE. * Renamed DISCLAIMER to NOTICE. Required code changes: * Removed redundant HAVE_SPL macro. * Removed _BOOT from nvpairs since it doesn't apply for Linux. * Initial header cleanup (removal of empty headers, refactoring). * Remove SPL repository clone/build from zimport.sh. * Use of DEFINE_RATELIMIT_STATE and DEFINE_SPINLOCK removed due to build issues when forcing C99 compilation. * Replaced legacy ACCESS_ONCE with READ_ONCE. * Include needed headers for `current` and `EXPORT_SYMBOL`. Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Olaf Faaland <faaland1@llnl.gov> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> TEST_ZIMPORT_SKIP="yes" Closes #7556
2018-02-16 01:53:18 +00:00
#if defined(_KERNEL)
EXPORT_SYMBOL(zrl_add_impl);
EXPORT_SYMBOL(zrl_remove);
#endif