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Commit e8c158bb authored by Robin Holt's avatar Robin Holt Committed by Linus Torvalds
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Factor out #ifdefs from kernel/spinlock.c to LOCK_CONTENDED_FLAGS 



SGI has observed that on large systems, interrupts are not serviced for a
long period of time when waiting for a rwlock.  The following patch series
re-enables irqs while waiting for the lock, resembling the code which is
already there for spinlocks.

I only made the ia64 version, because the patch adds some overhead to the
fast path.  I assume there is currently no demand to have this for other
architectures, because the systems are not so large.  Of course, the
possibility to implement raw_{read|write}_lock_flags for any architecture
is still there.

This patch:

The new macro LOCK_CONTENDED_FLAGS expands to the correct implementation
depending on the config options, so that IRQ's are re-enabled when
possible, but they remain disabled if CONFIG_LOCKDEP is set.

Signed-off-by: default avatarPetr Tesarik <ptesarik@suse.cz>
Signed-off-by: default avatarRobin Holt <holt@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 41d577aa

include/linux/lockdep.h

+17 −0
Original line number Diff line number Diff line
@@ -364,6 +364,23 @@ do { \ 


#endif /* CONFIG_LOCK_STAT */



#ifdef CONFIG_LOCKDEP



/*

 * On lockdep we dont want the hand-coded irq-enable of

 * _raw_*_lock_flags() code, because lockdep assumes

 * that interrupts are not re-enabled during lock-acquire:

 */

#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \

	LOCK_CONTENDED((_lock), (try), (lock))



#else /* CONFIG_LOCKDEP */



#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \

	lockfl((_lock), (flags))



#endif /* CONFIG_LOCKDEP */



#ifdef CONFIG_GENERIC_HARDIRQS

extern void early_init_irq_lock_class(void);

#else

kernel/spinlock.c

+2 −10
Original line number Diff line number Diff line
@@ -299,16 +299,8 @@ unsigned long __lockfunc _spin_lock_irqsave_nested(spinlock_t *lock, int subclas 
	local_irq_save(flags);

	preempt_disable();

	spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);

	/*

	 * On lockdep we dont want the hand-coded irq-enable of

	 * _raw_spin_lock_flags() code, because lockdep assumes

	 * that interrupts are not re-enabled during lock-acquire:

	 */

#ifdef CONFIG_LOCKDEP

	LOCK_CONTENDED(lock, _raw_spin_trylock, _raw_spin_lock);

#else

	_raw_spin_lock_flags(lock, &flags);

#endif

	LOCK_CONTENDED_FLAGS(lock, _raw_spin_trylock, _raw_spin_lock,

				_raw_spin_lock_flags, &flags);

	return flags;

}

EXPORT_SYMBOL(_spin_lock_irqsave_nested);