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Diffstat (limited to 'include/linux/rcuref.h')
| -rw-r--r-- | include/linux/rcuref.h | 220 |
1 files changed, 0 insertions, 220 deletions
diff --git a/include/linux/rcuref.h b/include/linux/rcuref.h deleted file mode 100644 index e1adbba14b67..000000000000 --- a/include/linux/rcuref.h +++ /dev/null @@ -1,220 +0,0 @@ -/* - * rcuref.h - * - * Reference counting for elements of lists/arrays protected by - * RCU. - * - * This program 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright (C) IBM Corporation, 2005 - * - * Author: Dipankar Sarma <dipankar@in.ibm.com> - * Ravikiran Thirumalai <kiran_th@gmail.com> - * - * See Documentation/RCU/rcuref.txt for detailed user guide. - * - */ - -#ifndef _RCUREF_H_ -#define _RCUREF_H_ - -#ifdef __KERNEL__ - -#include <linux/types.h> -#include <linux/interrupt.h> -#include <linux/spinlock.h> -#include <asm/atomic.h> - -/* - * These APIs work on traditional atomic_t counters used in the - * kernel for reference counting. Under special circumstances - * where a lock-free get() operation races with a put() operation - * these APIs can be used. See Documentation/RCU/rcuref.txt. - */ - -#ifdef __HAVE_ARCH_CMPXCHG - -/** - * rcuref_inc - increment refcount for object. - * @rcuref: reference counter in the object in question. - * - * This should be used only for objects where we use RCU and - * use the rcuref_inc_lf() api to acquire a reference - * in a lock-free reader-side critical section. - */ -static inline void rcuref_inc(atomic_t *rcuref) -{ - atomic_inc(rcuref); -} - -/** - * rcuref_dec - decrement refcount for object. - * @rcuref: reference counter in the object in question. - * - * This should be used only for objects where we use RCU and - * use the rcuref_inc_lf() api to acquire a reference - * in a lock-free reader-side critical section. - */ -static inline void rcuref_dec(atomic_t *rcuref) -{ - atomic_dec(rcuref); -} - -/** - * rcuref_dec_and_test - decrement refcount for object and test - * @rcuref: reference counter in the object. - * @release: pointer to the function that will clean up the object - * when the last reference to the object is released. - * This pointer is required. - * - * Decrement the refcount, and if 0, return 1. Else return 0. - * - * This should be used only for objects where we use RCU and - * use the rcuref_inc_lf() api to acquire a reference - * in a lock-free reader-side critical section. - */ -static inline int rcuref_dec_and_test(atomic_t *rcuref) -{ - return atomic_dec_and_test(rcuref); -} - -/* - * cmpxchg is needed on UP too, if deletions to the list/array can happen - * in interrupt context. - */ - -/** - * rcuref_inc_lf - Take reference to an object in a read-side - * critical section protected by RCU. - * @rcuref: reference counter in the object in question. - * - * Try and increment the refcount by 1. The increment might fail if - * the reference counter has been through a 1 to 0 transition and - * is no longer part of the lock-free list. - * Returns non-zero on successful increment and zero otherwise. - */ -static inline int rcuref_inc_lf(atomic_t *rcuref) -{ - int c, old; - c = atomic_read(rcuref); - while (c && (old = cmpxchg(&rcuref->counter, c, c + 1)) != c) - c = old; - return c; -} - -#else /* !__HAVE_ARCH_CMPXCHG */ - -extern spinlock_t __rcuref_hash[]; - -/* - * Use a hash table of locks to protect the reference count - * since cmpxchg is not available in this arch. - */ -#ifdef CONFIG_SMP -#define RCUREF_HASH_SIZE 4 -#define RCUREF_HASH(k) \ - (&__rcuref_hash[(((unsigned long)k)>>8) & (RCUREF_HASH_SIZE-1)]) -#else -#define RCUREF_HASH_SIZE 1 -#define RCUREF_HASH(k) &__rcuref_hash[0] -#endif /* CONFIG_SMP */ - -/** - * rcuref_inc - increment refcount for object. - * @rcuref: reference counter in the object in question. - * - * This should be used only for objects where we use RCU and - * use the rcuref_inc_lf() api to acquire a reference in a lock-free - * reader-side critical section. - */ -static inline void rcuref_inc(atomic_t *rcuref) -{ - unsigned long flags; - spin_lock_irqsave(RCUREF_HASH(rcuref), flags); - rcuref->counter += 1; - spin_unlock_irqrestore(RCUREF_HASH(rcuref), flags); -} - -/** - * rcuref_dec - decrement refcount for object. - * @rcuref: reference counter in the object in question. - * - * This should be used only for objects where we use RCU and - * use the rcuref_inc_lf() api to acquire a reference in a lock-free - * reader-side critical section. - */ -static inline void rcuref_dec(atomic_t *rcuref) -{ - unsigned long flags; - spin_lock_irqsave(RCUREF_HASH(rcuref), flags); - rcuref->counter -= 1; - spin_unlock_irqrestore(RCUREF_HASH(rcuref), flags); -} - -/** - * rcuref_dec_and_test - decrement refcount for object and test - * @rcuref: reference counter in the object. - * @release: pointer to the function that will clean up the object - * when the last reference to the object is released. - * This pointer is required. - * - * Decrement the refcount, and if 0, return 1. Else return 0. - * - * This should be used only for objects where we use RCU and - * use the rcuref_inc_lf() api to acquire a reference in a lock-free - * reader-side critical section. - */ -static inline int rcuref_dec_and_test(atomic_t *rcuref) -{ - unsigned long flags; - spin_lock_irqsave(RCUREF_HASH(rcuref), flags); - rcuref->counter--; - if (!rcuref->counter) { - spin_unlock_irqrestore(RCUREF_HASH(rcuref), flags); - return 1; - } else { - spin_unlock_irqrestore(RCUREF_HASH(rcuref), flags); - return 0; - } -} - -/** - * rcuref_inc_lf - Take reference to an object of a lock-free collection - * by traversing a lock-free list/array. - * @rcuref: reference counter in the object in question. - * - * Try and increment the refcount by 1. The increment might fail if - * the reference counter has been through a 1 to 0 transition and - * object is no longer part of the lock-free list. - * Returns non-zero on successful increment and zero otherwise. - */ -static inline int rcuref_inc_lf(atomic_t *rcuref) -{ - int ret; - unsigned long flags; - spin_lock_irqsave(RCUREF_HASH(rcuref), flags); - if (rcuref->counter) - ret = rcuref->counter++; - else - ret = 0; - spin_unlock_irqrestore(RCUREF_HASH(rcuref), flags); - return ret; -} - - -#endif /* !__HAVE_ARCH_CMPXCHG */ - -#endif /* __KERNEL__ */ -#endif /* _RCUREF_H_ */ |