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2f76797ad9
A spurious mutex_exit() in a development branch caused weird issues until I identified it. An assertion prior to mutex_exit() would have caught it. Rather than adding assertions before invocations of mutex_exit() in the code, let us simply add an assertion to mutex_exit(). It is cheap and will likely improve developer productivity. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Brian Atkinson <batkinson@lanl.gov> Signed-off-by: Richard Yao <richard.yao@klarasystems.com> Sponsored-By: Wasabi Technology, Inc. Closes #14541
185 lines
5.2 KiB
C
185 lines
5.2 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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*
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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_MUTEX_H
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#define _SPL_MUTEX_H
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#include <sys/types.h>
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#include <linux/sched.h>
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#include <linux/mutex.h>
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#include <linux/lockdep.h>
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#include <linux/compiler_compat.h>
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typedef enum {
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MUTEX_DEFAULT = 0,
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MUTEX_SPIN = 1,
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MUTEX_ADAPTIVE = 2,
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MUTEX_NOLOCKDEP = 3
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} kmutex_type_t;
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typedef struct {
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struct mutex m_mutex;
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spinlock_t m_lock; /* used for serializing mutex_exit */
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kthread_t *m_owner;
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#ifdef CONFIG_LOCKDEP
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kmutex_type_t m_type;
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#endif /* CONFIG_LOCKDEP */
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} kmutex_t;
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#define MUTEX(mp) (&((mp)->m_mutex))
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static inline void
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spl_mutex_set_owner(kmutex_t *mp)
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{
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mp->m_owner = current;
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}
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static inline void
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spl_mutex_clear_owner(kmutex_t *mp)
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{
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mp->m_owner = NULL;
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}
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#define mutex_owner(mp) (READ_ONCE((mp)->m_owner))
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#define mutex_owned(mp) (mutex_owner(mp) == current)
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#define MUTEX_HELD(mp) mutex_owned(mp)
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#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
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#ifdef CONFIG_LOCKDEP
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static inline void
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spl_mutex_set_type(kmutex_t *mp, kmutex_type_t type)
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{
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mp->m_type = type;
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}
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static inline void
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spl_mutex_lockdep_off_maybe(kmutex_t *mp) \
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{ \
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if (mp && mp->m_type == MUTEX_NOLOCKDEP) \
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lockdep_off(); \
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}
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static inline void
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spl_mutex_lockdep_on_maybe(kmutex_t *mp) \
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{ \
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if (mp && mp->m_type == MUTEX_NOLOCKDEP) \
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lockdep_on(); \
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}
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#else /* CONFIG_LOCKDEP */
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#define spl_mutex_set_type(mp, type)
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#define spl_mutex_lockdep_off_maybe(mp)
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#define spl_mutex_lockdep_on_maybe(mp)
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#endif /* CONFIG_LOCKDEP */
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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 mutex functions (lock/unlock)
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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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#undef mutex_init
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#define mutex_init(mp, name, type, ibc) \
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{ \
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static struct lock_class_key __key; \
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ASSERT(type == MUTEX_DEFAULT || type == MUTEX_NOLOCKDEP); \
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\
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__mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
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spin_lock_init(&(mp)->m_lock); \
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spl_mutex_clear_owner(mp); \
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spl_mutex_set_type(mp, type); \
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}
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#undef mutex_destroy
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#define mutex_destroy(mp) \
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{ \
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VERIFY3P(mutex_owner(mp), ==, NULL); \
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}
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#define mutex_tryenter(mp) \
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/* CSTYLED */ \
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({ \
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int _rc_; \
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\
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spl_mutex_lockdep_off_maybe(mp); \
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if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
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spl_mutex_set_owner(mp); \
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spl_mutex_lockdep_on_maybe(mp); \
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\
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_rc_; \
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})
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#define NESTED_SINGLE 1
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define mutex_enter_nested(mp, subclass) \
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{ \
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ASSERT3P(mutex_owner(mp), !=, current); \
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spl_mutex_lockdep_off_maybe(mp); \
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mutex_lock_nested(MUTEX(mp), (subclass)); \
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spl_mutex_lockdep_on_maybe(mp); \
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spl_mutex_set_owner(mp); \
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}
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#else /* CONFIG_DEBUG_LOCK_ALLOC */
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#define mutex_enter_nested(mp, subclass) \
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{ \
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ASSERT3P(mutex_owner(mp), !=, current); \
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spl_mutex_lockdep_off_maybe(mp); \
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mutex_lock(MUTEX(mp)); \
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spl_mutex_lockdep_on_maybe(mp); \
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spl_mutex_set_owner(mp); \
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}
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#endif /* CONFIG_DEBUG_LOCK_ALLOC */
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#define mutex_enter(mp) mutex_enter_nested((mp), 0)
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/*
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* The reason for the spinlock:
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*
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* The Linux mutex is designed with a fast-path/slow-path design such that it
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* does not guarantee serialization upon itself, allowing a race where latter
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* acquirers finish mutex_unlock before former ones.
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*
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* The race renders it unsafe to be used for serializing the freeing of an
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* object in which the mutex is embedded, where the latter acquirer could go
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* on to free the object while the former one is still doing mutex_unlock and
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* causing memory corruption.
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*
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* However, there are many places in ZFS where the mutex is used for
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* serializing object freeing, and the code is shared among other OSes without
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* this issue. Thus, we need the spinlock to force the serialization on
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* mutex_exit().
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*
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* See http://lwn.net/Articles/575477/ for the information about the race.
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*/
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#define mutex_exit(mp) \
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{ \
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ASSERT3P(mutex_owner(mp), ==, current); \
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spl_mutex_clear_owner(mp); \
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spin_lock(&(mp)->m_lock); \
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spl_mutex_lockdep_off_maybe(mp); \
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mutex_unlock(MUTEX(mp)); \
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spl_mutex_lockdep_on_maybe(mp); \
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spin_unlock(&(mp)->m_lock); \
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/* NOTE: do not dereference mp after this point */ \
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}
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#endif /* _SPL_MUTEX_H */
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