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692ae8d398
When running a kernel with CONFIG_LOCKDEP=y, lockdep reports possible recursive locking in some cases and possible circular locking dependency in others, within the SPL and ZFS modules. When lockdep detects these conditions, it disables further lock analysis for all locks. This causes /proc/lock_stats not to reflect full information about lock contention, even in locks without dependency issues. This commit creates a new type of mutex, MUTEX_NOLOCKDEP. This mutex type causes subsequent attempts to take or release those locks to be wrapped in lockdep_off() and lockdep_on(). This commit also creates an RW_NOLOCKDEP type analagous to MUTEX_NOLOCKDEP. MUTEX_NOLOCKDEP and RW_NOLOCKDEP are also defined in zfs, in a commit to that repo, for userspace builds. Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #480
259 lines
6.7 KiB
C
259 lines
6.7 KiB
C
/*****************************************************************************\
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://zfsonlinux.org/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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\*****************************************************************************/
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#ifndef _SPL_RWLOCK_H
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#define _SPL_RWLOCK_H
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#include <sys/types.h>
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#include <linux/rwsem.h>
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#include <linux/rwsem_compat.h>
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typedef enum {
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RW_DRIVER = 2,
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RW_DEFAULT = 4,
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RW_NOLOCKDEP = 5
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} krw_type_t;
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typedef enum {
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RW_NONE = 0,
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RW_WRITER = 1,
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RW_READER = 2
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} krw_t;
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/*
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* If CONFIG_RWSEM_SPIN_ON_OWNER is defined, rw_semaphore will have an owner
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* field, so we don't need our own.
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*/
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typedef struct {
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struct rw_semaphore rw_rwlock;
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#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
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kthread_t *rw_owner;
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#endif
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#ifdef CONFIG_LOCKDEP
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krw_type_t rw_type;
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#endif /* CONFIG_LOCKDEP */
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} krwlock_t;
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#define SEM(rwp) (&(rwp)->rw_rwlock)
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static inline void
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spl_rw_set_owner(krwlock_t *rwp)
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{
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/*
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* If CONFIG_RWSEM_SPIN_ON_OWNER is defined, down_write, up_write,
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* downgrade_write and __init_rwsem will set/clear owner for us.
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*/
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#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
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rwp->rw_owner = current;
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#endif
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}
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static inline void
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spl_rw_clear_owner(krwlock_t *rwp)
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{
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#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
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rwp->rw_owner = NULL;
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#endif
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}
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static inline kthread_t *
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rw_owner(krwlock_t *rwp)
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{
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#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
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return SEM(rwp)->owner;
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#else
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return rwp->rw_owner;
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#endif
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}
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#ifdef CONFIG_LOCKDEP
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static inline void
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spl_rw_set_type(krwlock_t *rwp, krw_type_t type)
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{
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rwp->rw_type = type;
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}
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static inline void
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spl_rw_lockdep_off_maybe(krwlock_t *rwp) \
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{ \
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if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
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lockdep_off(); \
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}
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static inline void
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spl_rw_lockdep_on_maybe(krwlock_t *rwp) \
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{ \
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if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
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lockdep_on(); \
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}
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#else /* CONFIG_LOCKDEP */
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#define spl_rw_set_type(rwp, type)
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#define spl_rw_lockdep_off_maybe(rwp)
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#define spl_rw_lockdep_on_maybe(rwp)
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#endif /* CONFIG_LOCKDEP */
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static inline int
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RW_READ_HELD(krwlock_t *rwp)
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{
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return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL);
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}
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static inline int
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RW_WRITE_HELD(krwlock_t *rwp)
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{
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return (rw_owner(rwp) == current);
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}
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static inline int
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RW_LOCK_HELD(krwlock_t *rwp)
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{
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return spl_rwsem_is_locked(SEM(rwp));
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}
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/*
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* The following functions must be a #define and not static inline.
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* This ensures that the native linux semaphore functions (down/up)
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* will be correctly located in the users code which is important
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* for the built in kernel lock analysis tools
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*/
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#define rw_init(rwp, name, type, arg) \
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({ \
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static struct lock_class_key __key; \
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ASSERT(type == RW_DEFAULT || type == RW_NOLOCKDEP); \
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\
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__init_rwsem(SEM(rwp), #rwp, &__key); \
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spl_rw_clear_owner(rwp); \
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spl_rw_set_type(rwp, type); \
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})
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#define rw_destroy(rwp) \
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({ \
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VERIFY(!RW_LOCK_HELD(rwp)); \
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})
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#define rw_tryenter(rwp, rw) \
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({ \
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int _rc_ = 0; \
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\
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spl_rw_lockdep_off_maybe(rwp); \
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switch (rw) { \
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case RW_READER: \
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_rc_ = down_read_trylock(SEM(rwp)); \
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break; \
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case RW_WRITER: \
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if ((_rc_ = down_write_trylock(SEM(rwp)))) \
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spl_rw_set_owner(rwp); \
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break; \
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default: \
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VERIFY(0); \
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} \
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spl_rw_lockdep_on_maybe(rwp); \
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_rc_; \
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})
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#define rw_enter(rwp, rw) \
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({ \
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spl_rw_lockdep_off_maybe(rwp); \
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switch (rw) { \
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case RW_READER: \
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down_read(SEM(rwp)); \
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break; \
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case RW_WRITER: \
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down_write(SEM(rwp)); \
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spl_rw_set_owner(rwp); \
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break; \
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default: \
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VERIFY(0); \
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} \
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spl_rw_lockdep_on_maybe(rwp); \
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})
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#define rw_exit(rwp) \
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({ \
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spl_rw_lockdep_off_maybe(rwp); \
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if (RW_WRITE_HELD(rwp)) { \
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spl_rw_clear_owner(rwp); \
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up_write(SEM(rwp)); \
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} else { \
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ASSERT(RW_READ_HELD(rwp)); \
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up_read(SEM(rwp)); \
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} \
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spl_rw_lockdep_on_maybe(rwp); \
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})
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#define rw_downgrade(rwp) \
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({ \
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spl_rw_lockdep_off_maybe(rwp); \
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spl_rw_clear_owner(rwp); \
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downgrade_write(SEM(rwp)); \
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spl_rw_lockdep_on_maybe(rwp); \
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})
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#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
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#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
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#error spinlock rwsem should not have spin on owner
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#endif
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/*
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* For the generic implementations of rw-semaphores the following is
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* true. If your semaphore implementation internally represents the
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* semaphore state differently then special case handling is required.
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* - if activity/count is 0 then there are no active readers or writers
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* - if activity/count is +ve then that is the number of active readers
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* - if activity/count is -1 then there is one active writer
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*/
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extern void __up_read_locked(struct rw_semaphore *);
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extern int __down_write_trylock_locked(struct rw_semaphore *);
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#define rw_tryupgrade(rwp) \
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({ \
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unsigned long _flags_; \
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int _rc_ = 0; \
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\
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spl_rw_lockdep_off_maybe(rwp); \
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spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \
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if ((list_empty(&SEM(rwp)->wait_list)) && \
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(SEM(rwp)->activity == 1)) { \
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__up_read_locked(SEM(rwp)); \
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VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp))); \
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(rwp)->rw_owner = current; \
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} \
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spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \
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spl_rw_lockdep_on_maybe(rwp); \
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_rc_; \
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})
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#else
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/*
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* rw_tryupgrade() can be implemented correctly but for each supported
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* arch we will need a custom implementation. For the x86 implementation
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* it looks like a custom cmpxchg() to atomically check and promote the
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* rwsem would be safe. For now that's not worth the trouble so in this
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* case rw_tryupgrade() has just been disabled.
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*/
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#define rw_tryupgrade(rwp) ({ 0; })
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#endif
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int spl_rw_init(void);
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void spl_rw_fini(void);
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#endif /* _SPL_RWLOCK_H */
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