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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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95c354fe9f
The break_lock data structure and code for spinlocks is quite nasty. Not only does it double the size of a spinlock but it changes locking to a potentially less optimal trylock. Put all of that under CONFIG_GENERIC_LOCKBREAK, and introduce a __raw_spin_is_contended that uses the lock data itself to determine whether there are waiters on the lock, to be used if CONFIG_GENERIC_LOCKBREAK is not set. Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to decouple it from the spinlock implementation, and make it typesafe (rwlocks do not have any need_lockbreak sites -- why do they even get bloated up with that break_lock then?). Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
76 lines
2.0 KiB
C
76 lines
2.0 KiB
C
#ifndef __LINUX_SPINLOCK_UP_H
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#define __LINUX_SPINLOCK_UP_H
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#ifndef __LINUX_SPINLOCK_H
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# error "please don't include this file directly"
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#endif
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/*
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* include/linux/spinlock_up.h - UP-debug version of spinlocks.
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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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* In the debug case, 1 means unlocked, 0 means locked. (the values
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* are inverted, to catch initialization bugs)
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*
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* No atomicity anywhere, we are on UP.
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*/
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#ifdef CONFIG_DEBUG_SPINLOCK
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#define __raw_spin_is_locked(x) ((x)->slock == 0)
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static inline void __raw_spin_lock(raw_spinlock_t *lock)
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{
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lock->slock = 0;
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}
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static inline void
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__raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
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{
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local_irq_save(flags);
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lock->slock = 0;
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}
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static inline int __raw_spin_trylock(raw_spinlock_t *lock)
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{
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char oldval = lock->slock;
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lock->slock = 0;
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return oldval > 0;
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}
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static inline void __raw_spin_unlock(raw_spinlock_t *lock)
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{
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lock->slock = 1;
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}
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/*
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* Read-write spinlocks. No debug version.
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*/
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#define __raw_read_lock(lock) do { (void)(lock); } while (0)
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#define __raw_write_lock(lock) do { (void)(lock); } while (0)
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#define __raw_read_trylock(lock) ({ (void)(lock); 1; })
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#define __raw_write_trylock(lock) ({ (void)(lock); 1; })
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#define __raw_read_unlock(lock) do { (void)(lock); } while (0)
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#define __raw_write_unlock(lock) do { (void)(lock); } while (0)
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#else /* DEBUG_SPINLOCK */
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#define __raw_spin_is_locked(lock) ((void)(lock), 0)
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/* for sched.c and kernel_lock.c: */
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# define __raw_spin_lock(lock) do { (void)(lock); } while (0)
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# define __raw_spin_unlock(lock) do { (void)(lock); } while (0)
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# define __raw_spin_trylock(lock) ({ (void)(lock); 1; })
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#endif /* DEBUG_SPINLOCK */
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#define __raw_spin_is_contended(lock) (((void)(lock), 0))
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#define __raw_read_can_lock(lock) (((void)(lock), 1))
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#define __raw_write_can_lock(lock) (((void)(lock), 1))
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#define __raw_spin_unlock_wait(lock) \
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do { cpu_relax(); } while (__raw_spin_is_locked(lock))
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#endif /* __LINUX_SPINLOCK_UP_H */
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