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spinlock: lockbreak cleanup

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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>
This commit is contained in:
Nick Piggin 2008-01-30 13:31:20 +01:00 • committed by Ingo Molnar
parent a95d67f87e
commit 95c354fe9f
19 changed files with 72 additions and 37 deletions
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2
include/linux/spinlock_up.h
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@ -64,6 +64,8 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock)
# define __raw_spin_trylock(lock) ({ (void)(lock); 1; })
#endif /* DEBUG_SPINLOCK */
#define __raw_spin_is_contended(lock) (((void)(lock), 0))
#define __raw_read_can_lock(lock) (((void)(lock), 1))
#define __raw_write_can_lock(lock) (((void)(lock), 1))