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/*
* Copyright (C) 2005-2015 Junjiro R. Okajima
*
* This program, aufs is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* simple read-write semaphore wrappers
*/
#ifndef __AUFS_RWSEM_H__
#define __AUFS_RWSEM_H__
#ifdef __KERNEL__
#include "debug.h"
struct au_rwsem {
struct rw_semaphore rwsem;
#ifdef CONFIG_AUFS_DEBUG
/* just for debugging, not almighty counter */
atomic_t rcnt, wcnt;
#endif
};
#ifdef CONFIG_AUFS_DEBUG
#define AuDbgCntInit(rw) do { \
atomic_set(&(rw)->rcnt, 0); \
atomic_set(&(rw)->wcnt, 0); \
smp_mb(); /* atomic set */ \
} while (0)
#define AuDbgRcntInc(rw) atomic_inc(&(rw)->rcnt)
#define AuDbgRcntDec(rw) WARN_ON(atomic_dec_return(&(rw)->rcnt) < 0)
#define AuDbgWcntInc(rw) atomic_inc(&(rw)->wcnt)
#define AuDbgWcntDec(rw) WARN_ON(atomic_dec_return(&(rw)->wcnt) < 0)
#else
#define AuDbgCntInit(rw) do {} while (0)
#define AuDbgRcntInc(rw) do {} while (0)
#define AuDbgRcntDec(rw) do {} while (0)
#define AuDbgWcntInc(rw) do {} while (0)
#define AuDbgWcntDec(rw) do {} while (0)
#endif /* CONFIG_AUFS_DEBUG */
/* to debug easier, do not make them inlined functions */
#define AuRwMustNoWaiters(rw) AuDebugOn(!list_empty(&(rw)->rwsem.wait_list))
/* rwsem_is_locked() is unusable */
#define AuRwMustReadLock(rw) AuDebugOn(atomic_read(&(rw)->rcnt) <= 0)
#define AuRwMustWriteLock(rw) AuDebugOn(atomic_read(&(rw)->wcnt) <= 0)
#define AuRwMustAnyLock(rw) AuDebugOn(atomic_read(&(rw)->rcnt) <= 0 \
&& atomic_read(&(rw)->wcnt) <= 0)
#define AuRwDestroy(rw) AuDebugOn(atomic_read(&(rw)->rcnt) \
|| atomic_read(&(rw)->wcnt))
#define au_rw_class(rw, key) lockdep_set_class(&(rw)->rwsem, key)
static inline void au_rw_init(struct au_rwsem *rw)
{
AuDbgCntInit(rw);
init_rwsem(&rw->rwsem);
}
static inline void au_rw_init_wlock(struct au_rwsem *rw)
{
au_rw_init(rw);
down_write(&rw->rwsem);
AuDbgWcntInc(rw);
}
static inline void au_rw_init_wlock_nested(struct au_rwsem *rw,
unsigned int lsc)
{
au_rw_init(rw);
down_write_nested(&rw->rwsem, lsc);
AuDbgWcntInc(rw);
}
static inline void au_rw_read_lock(struct au_rwsem *rw)
{
down_read(&rw->rwsem);
AuDbgRcntInc(rw);
}
static inline void au_rw_read_lock_nested(struct au_rwsem *rw, unsigned int lsc)
{
down_read_nested(&rw->rwsem, lsc);
AuDbgRcntInc(rw);
}
static inline void au_rw_read_unlock(struct au_rwsem *rw)
{
AuRwMustReadLock(rw);
AuDbgRcntDec(rw);
up_read(&rw->rwsem);
}
static inline void au_rw_dgrade_lock(struct au_rwsem *rw)
{
AuRwMustWriteLock(rw);
AuDbgRcntInc(rw);
AuDbgWcntDec(rw);
downgrade_write(&rw->rwsem);
}
static inline void au_rw_write_lock(struct au_rwsem *rw)
{
down_write(&rw->rwsem);
AuDbgWcntInc(rw);
}
static inline void au_rw_write_lock_nested(struct au_rwsem *rw,
unsigned int lsc)
{
down_write_nested(&rw->rwsem, lsc);
AuDbgWcntInc(rw);
}
static inline void au_rw_write_unlock(struct au_rwsem *rw)
{
AuRwMustWriteLock(rw);
AuDbgWcntDec(rw);
up_write(&rw->rwsem);
}
/* why is not _nested version defined */
static inline int au_rw_read_trylock(struct au_rwsem *rw)
{
int ret;
ret = down_read_trylock(&rw->rwsem);
if (ret)
AuDbgRcntInc(rw);
return ret;
}
static inline int au_rw_write_trylock(struct au_rwsem *rw)
{
int ret;
ret = down_write_trylock(&rw->rwsem);
if (ret)
AuDbgWcntInc(rw);
return ret;
}
#undef AuDbgCntInit
#undef AuDbgRcntInc
#undef AuDbgRcntDec
#undef AuDbgWcntInc
#undef AuDbgWcntDec
#define AuSimpleLockRwsemFuncs(prefix, param, rwsem) \
static inline void prefix##_read_lock(param) \
{ au_rw_read_lock(rwsem); } \
static inline void prefix##_write_lock(param) \
{ au_rw_write_lock(rwsem); } \
static inline int prefix##_read_trylock(param) \
{ return au_rw_read_trylock(rwsem); } \
static inline int prefix##_write_trylock(param) \
{ return au_rw_write_trylock(rwsem); }
/* why is not _nested version defined */
/* static inline void prefix##_read_trylock_nested(param, lsc)
{ au_rw_read_trylock_nested(rwsem, lsc)); }
static inline void prefix##_write_trylock_nestd(param, lsc)
{ au_rw_write_trylock_nested(rwsem, lsc); } */
#define AuSimpleUnlockRwsemFuncs(prefix, param, rwsem) \
static inline void prefix##_read_unlock(param) \
{ au_rw_read_unlock(rwsem); } \
static inline void prefix##_write_unlock(param) \
{ au_rw_write_unlock(rwsem); } \
static inline void prefix##_downgrade_lock(param) \
{ au_rw_dgrade_lock(rwsem); }
#define AuSimpleRwsemFuncs(prefix, param, rwsem) \
AuSimpleLockRwsemFuncs(prefix, param, rwsem) \
AuSimpleUnlockRwsemFuncs(prefix, param, rwsem)
#endif /* __KERNEL__ */
#endif /* __AUFS_RWSEM_H__ */
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