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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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6
include/linux/spinlock.h
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@@ -120,6 +120,12 @@ do { \
#define spin_is_locked(lock) __raw_spin_is_locked(&(lock)->raw_lock)
#ifdef CONFIG_GENERIC_LOCKBREAK
#define spin_is_contended(lock) ((lock)->break_lock)
#else
#define spin_is_contended(lock) __raw_spin_is_contended(&(lock)->raw_lock)
#endif
/**
* spin_unlock_wait - wait until the spinlock gets unlocked
* @lock: the spinlock in question.