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Similar to rw_semaphores, on RT the rwlock substitution is not writer fair, because it's not feasible to have a writer inherit its priority to multiple readers. Readers blocked on a writer follow the normal rules of priority inheritance. Like RT spinlocks, RT rwlocks are state preserving across the slow lock operations (contended case). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210815211303.882793524@linutronix.de
78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
#ifndef __LINUX_RWLOCK_TYPES_H
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#define __LINUX_RWLOCK_TYPES_H
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#if !defined(__LINUX_SPINLOCK_TYPES_H)
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# error "Do not include directly, include spinlock_types.h"
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# define RW_DEP_MAP_INIT(lockname) \
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.dep_map = { \
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.name = #lockname, \
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.wait_type_inner = LD_WAIT_CONFIG, \
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}
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#else
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# define RW_DEP_MAP_INIT(lockname)
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#endif
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#ifndef CONFIG_PREEMPT_RT
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/*
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* generic rwlock type definitions and initializers
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*
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* portions Copyright 2005, Red Hat, Inc., Ingo Molnar
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* Released under the General Public License (GPL).
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*/
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typedef struct {
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arch_rwlock_t raw_lock;
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#ifdef CONFIG_DEBUG_SPINLOCK
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unsigned int magic, owner_cpu;
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void *owner;
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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} rwlock_t;
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#define RWLOCK_MAGIC 0xdeaf1eed
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#ifdef CONFIG_DEBUG_SPINLOCK
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#define __RW_LOCK_UNLOCKED(lockname) \
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(rwlock_t) { .raw_lock = __ARCH_RW_LOCK_UNLOCKED, \
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.magic = RWLOCK_MAGIC, \
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.owner = SPINLOCK_OWNER_INIT, \
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.owner_cpu = -1, \
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RW_DEP_MAP_INIT(lockname) }
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#else
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#define __RW_LOCK_UNLOCKED(lockname) \
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(rwlock_t) { .raw_lock = __ARCH_RW_LOCK_UNLOCKED, \
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RW_DEP_MAP_INIT(lockname) }
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#endif
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#define DEFINE_RWLOCK(x) rwlock_t x = __RW_LOCK_UNLOCKED(x)
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#else /* !CONFIG_PREEMPT_RT */
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#include <linux/rwbase_rt.h>
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typedef struct {
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struct rwbase_rt rwbase;
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atomic_t readers;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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} rwlock_t;
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#define __RWLOCK_RT_INITIALIZER(name) \
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{ \
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.rwbase = __RWBASE_INITIALIZER(name), \
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RW_DEP_MAP_INIT(name) \
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}
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#define __RW_LOCK_UNLOCKED(name) __RWLOCK_RT_INITIALIZER(name)
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#define DEFINE_RWLOCK(name) \
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rwlock_t name = __RW_LOCK_UNLOCKED(name)
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#endif /* CONFIG_PREEMPT_RT */
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#endif /* __LINUX_RWLOCK_TYPES_H */
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