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https://github.com/linux-msm/laptops-kernel.git
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Mateusz GuzikandChristian Brauner
91e27ed8a3
1. put the dead val into a macro so that it can be used in other places 2. __lockref_is_dead(): - drop the __ suffix, this is not an internal routine - drop the spurious cast, the value is already a signed int - use READ_ONCE to prevent any compile shenanigans 3. provide lockref_is_dead_or_zero() Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Link: https://patch.msgid.link/20260724171422.429284-2-mjguzik@gmail.com Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_LOCKREF_H
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#define __LINUX_LOCKREF_H
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/*
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* Locked reference counts.
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*
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* These are different from just plain atomic refcounts in that they
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* are atomic with respect to the spinlock that goes with them. In
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* particular, there can be implementations that don't actually get
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* the spinlock for the common decrement/increment operations, but they
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* still have to check that the operation is done semantically as if
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* the spinlock had been taken (using a cmpxchg operation that covers
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* both the lock and the count word, or using memory transactions, for
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* example).
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*/
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#include <linux/spinlock.h>
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#include <generated/bounds.h>
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#define USE_CMPXCHG_LOCKREF \
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(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
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IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
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struct lockref {
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union {
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#if USE_CMPXCHG_LOCKREF
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aligned_u64 lock_count;
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#endif
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struct {
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spinlock_t lock;
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int count;
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};
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};
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};
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#define __LOCKREF_DEAD_VAL -128
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/**
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* lockref_init - Initialize a lockref
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* @lockref: pointer to lockref structure
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*
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* Initializes @lockref->count to 1.
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*/
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static inline void lockref_init(struct lockref *lockref)
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{
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spin_lock_init(&lockref->lock);
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lockref->count = 1;
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}
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void lockref_get(struct lockref *lockref);
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int lockref_put_return(struct lockref *lockref);
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bool lockref_get_not_zero(struct lockref *lockref);
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bool lockref_put_or_lock(struct lockref *lockref) __cond_acquires(false, &lockref->lock);
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void lockref_mark_dead(struct lockref *lockref);
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bool lockref_get_not_dead(struct lockref *lockref);
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/* Must be called under spinlock for reliable results */
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static inline bool lockref_is_dead(const struct lockref *l)
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{
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return (READ_ONCE(l->count) == __LOCKREF_DEAD_VAL);
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}
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static inline bool lockref_is_dead_or_zero(const struct lockref *l)
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{
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int count = READ_ONCE(l->count);
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return (count == __LOCKREF_DEAD_VAL || count == 0);
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}
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#endif /* __LINUX_LOCKREF_H */
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