kernel-ark/include/linux/spinlock_up.h
Nick Piggin 95c354fe9f spinlock: lockbreak cleanup
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>
2008-01-30 13:31:20 +01:00

76 lines
2.0 KiB
C

#ifndef __LINUX_SPINLOCK_UP_H
#define __LINUX_SPINLOCK_UP_H
#ifndef __LINUX_SPINLOCK_H
# error "please don't include this file directly"
#endif
/*
* include/linux/spinlock_up.h - UP-debug version of spinlocks.
*
* portions Copyright 2005, Red Hat, Inc., Ingo Molnar
* Released under the General Public License (GPL).
*
* In the debug case, 1 means unlocked, 0 means locked. (the values
* are inverted, to catch initialization bugs)
*
* No atomicity anywhere, we are on UP.
*/
#ifdef CONFIG_DEBUG_SPINLOCK
#define __raw_spin_is_locked(x) ((x)->slock == 0)
static inline void __raw_spin_lock(raw_spinlock_t *lock)
{
lock->slock = 0;
}
static inline void
__raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
{
local_irq_save(flags);
lock->slock = 0;
}
static inline int __raw_spin_trylock(raw_spinlock_t *lock)
{
char oldval = lock->slock;
lock->slock = 0;
return oldval > 0;
}
static inline void __raw_spin_unlock(raw_spinlock_t *lock)
{
lock->slock = 1;
}
/*
* Read-write spinlocks. No debug version.
*/
#define __raw_read_lock(lock) do { (void)(lock); } while (0)
#define __raw_write_lock(lock) do { (void)(lock); } while (0)
#define __raw_read_trylock(lock) ({ (void)(lock); 1; })
#define __raw_write_trylock(lock) ({ (void)(lock); 1; })
#define __raw_read_unlock(lock) do { (void)(lock); } while (0)
#define __raw_write_unlock(lock) do { (void)(lock); } while (0)
#else /* DEBUG_SPINLOCK */
#define __raw_spin_is_locked(lock) ((void)(lock), 0)
/* for sched.c and kernel_lock.c: */
# define __raw_spin_lock(lock) do { (void)(lock); } while (0)
# define __raw_spin_unlock(lock) do { (void)(lock); } while (0)
# 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))
#define __raw_spin_unlock_wait(lock) \
do { cpu_relax(); } while (__raw_spin_is_locked(lock))
#endif /* __LINUX_SPINLOCK_UP_H */