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Commit 894cdde2 authored by Hisashi Hifumi's avatar Hisashi Hifumi Committed by Martin Schwidefsky
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[S390] do local_irq_restore while spinning in spin_lock_irqsave. 



In s390's spin_lock_irqsave, interrupts remain disabled while
spinning. In other architectures like x86 and powerpc, interrupts are
re-enabled while spinning if IRQ is not masked before spin_lock_irqsave
is called.

The following patch re-enables interrupts through local_irq_restore
while spinning for a lock acquisition.
This can improve system response.

[heiko.carstens@de.ibm.com: removed saving of pc]

Signed-off-by: default avatarHisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent dab5209c

arch/s390/lib/spinlock.c

+23 −0
Original line number Diff line number Diff line
@@ -59,6 +59,29 @@ void _raw_spin_lock_wait(raw_spinlock_t *lp) 
}

EXPORT_SYMBOL(_raw_spin_lock_wait);



void _raw_spin_lock_wait_flags(raw_spinlock_t *lp, unsigned long flags)

{

	int count = spin_retry;

	unsigned int cpu = ~smp_processor_id();



	local_irq_restore(flags);

	while (1) {

		if (count-- <= 0) {

			unsigned int owner = lp->owner_cpu;

			if (owner != 0)

				_raw_yield_cpu(~owner);

			count = spin_retry;

		}

		if (__raw_spin_is_locked(lp))

			continue;

		local_irq_disable();

		if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)

			return;

		local_irq_restore(flags);

	}

}

EXPORT_SYMBOL(_raw_spin_lock_wait_flags);



int _raw_spin_trylock_retry(raw_spinlock_t *lp)

{

	unsigned int cpu = ~smp_processor_id();

include/asm-s390/spinlock.h

+12 −1
Original line number Diff line number Diff line
@@ -53,12 +53,12 @@ _raw_compare_and_swap(volatile unsigned int *lock, 
 */



#define __raw_spin_is_locked(x) ((x)->owner_cpu != 0)

#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)

#define __raw_spin_unlock_wait(lock) \

	do { while (__raw_spin_is_locked(lock)) \

		 _raw_spin_relax(lock); } while (0)



extern void _raw_spin_lock_wait(raw_spinlock_t *);

extern void _raw_spin_lock_wait_flags(raw_spinlock_t *, unsigned long flags);

extern int _raw_spin_trylock_retry(raw_spinlock_t *);

extern void _raw_spin_relax(raw_spinlock_t *lock);
@@ -72,6 +72,17 @@ static inline void __raw_spin_lock(raw_spinlock_t *lp) 
	_raw_spin_lock_wait(lp);

}



static inline void __raw_spin_lock_flags(raw_spinlock_t *lp,

					 unsigned long flags)

{

	int old;



	old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());

	if (likely(old == 0))

		return;

	_raw_spin_lock_wait_flags(lp, flags);

}



static inline int __raw_spin_trylock(raw_spinlock_t *lp)

{

	int old;