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Commit 5b3f683e authored by Philipp Hachtmann's avatar Philipp Hachtmann Committed by Martin Schwidefsky
Browse files

s390/spinlock: cleanup spinlock code 



Improve the spinlock code in several aspects:
 - Have _raw_compare_and_swap return true if the operation has been
   successful instead of returning the old value.
 - Remove the "volatile" from arch_spinlock_t and arch_rwlock_t
 - Rename 'owner_cpu' to 'lock'
 - Add helper functions arch_spin_trylock_once / arch_spin_tryrelease_once

[ Martin Schwidefsky: patch breakdown and code beautification ]

Signed-off-by: default avatarPhilipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 50be6345

arch/s390/include/asm/spinlock.h

+53 −45
Original line number Diff line number Diff line
@@ -14,15 +14,16 @@ 
extern int spin_retry;



static inline int

_raw_compare_and_swap(volatile unsigned int *lock,

		      unsigned int old, unsigned int new)

_raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)

{

	unsigned int old_expected = old;



	asm volatile(

		"	cs	%0,%3,%1"

		: "=d" (old), "=Q" (*lock)

		: "0" (old), "d" (new), "Q" (*lock)

		: "cc", "memory" );

	return old;

	return old == old_expected;

}



/*
@@ -34,55 +35,64 @@ _raw_compare_and_swap(volatile unsigned int *lock, 
 * (the type definitions are in asm/spinlock_types.h)

 */



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

#define arch_spin_unlock_wait(lock) \

	do { while (arch_spin_is_locked(lock)) \

		 arch_spin_relax(lock); } while (0)



extern void arch_spin_lock_wait(arch_spinlock_t *);

extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);

extern int arch_spin_trylock_retry(arch_spinlock_t *);

extern void arch_spin_relax(arch_spinlock_t *lock);

void arch_spin_lock_wait(arch_spinlock_t *);

int arch_spin_trylock_retry(arch_spinlock_t *);

void arch_spin_relax(arch_spinlock_t *);

void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);



static inline int arch_spin_value_unlocked(arch_spinlock_t lock)

{

	return lock.owner_cpu == 0;

	return lock.lock == 0;

}



static inline void arch_spin_lock(arch_spinlock_t *lp)

static inline int arch_spin_is_locked(arch_spinlock_t *lp)

{

	return ACCESS_ONCE(lp->lock) != 0;

}



static inline int arch_spin_trylock_once(arch_spinlock_t *lp)

{

	int old;

	unsigned int new = ~smp_processor_id();



	return _raw_compare_and_swap(&lp->lock, 0, new);

}



static inline int arch_spin_tryrelease_once(arch_spinlock_t *lp)

{

	unsigned int old = ~smp_processor_id();



	return _raw_compare_and_swap(&lp->lock, old, 0);

}



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

	if (likely(old == 0))

		return;

static inline void arch_spin_lock(arch_spinlock_t *lp)

{

	if (unlikely(!arch_spin_trylock_once(lp)))

		arch_spin_lock_wait(lp);

}



static inline void arch_spin_lock_flags(arch_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;

	if (unlikely(!arch_spin_trylock_once(lp)))

		arch_spin_lock_wait_flags(lp, flags);

}



static inline int arch_spin_trylock(arch_spinlock_t *lp)

{

	int old;



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

	if (likely(old == 0))

		return 1;

	if (unlikely(!arch_spin_trylock_once(lp)))

		return arch_spin_trylock_retry(lp);

	return 1;

}



static inline void arch_spin_unlock(arch_spinlock_t *lp)

{

	_raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0);

	arch_spin_tryrelease_once(lp);

}



static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)

{

	while (arch_spin_is_locked(lock))

		arch_spin_relax(lock);

}



/*
@@ -119,7 +129,7 @@ static inline void arch_read_lock(arch_rwlock_t *rw) 
{

	unsigned int old;

	old = rw->lock & 0x7fffffffU;

	if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)

	if (!_raw_compare_and_swap(&rw->lock, old, old + 1))

		_raw_read_lock_wait(rw);

}
@@ -127,30 +137,28 @@ static inline void arch_read_lock_flags(arch_rwlock_t *rw, unsigned long flags) 
{

	unsigned int old;

	old = rw->lock & 0x7fffffffU;

	if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)

	if (!_raw_compare_and_swap(&rw->lock, old, old + 1))

		_raw_read_lock_wait_flags(rw, flags);

}



static inline void arch_read_unlock(arch_rwlock_t *rw)

{

	unsigned int old, cmp;

	unsigned int old;



	old = rw->lock;

	do {

		cmp = old;

		old = _raw_compare_and_swap(&rw->lock, old, old - 1);

	} while (cmp != old);

		old = ACCESS_ONCE(rw->lock);

	} while (!_raw_compare_and_swap(&rw->lock, old, old - 1));

}



static inline void arch_write_lock(arch_rwlock_t *rw)

{

	if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))

	if (unlikely(!_raw_compare_and_swap(&rw->lock, 0, 0x80000000)))

		_raw_write_lock_wait(rw);

}



static inline void arch_write_lock_flags(arch_rwlock_t *rw, unsigned long flags)

{

	if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))

	if (unlikely(!_raw_compare_and_swap(&rw->lock, 0, 0x80000000)))

		_raw_write_lock_wait_flags(rw, flags);

}
@@ -163,14 +171,14 @@ static inline int arch_read_trylock(arch_rwlock_t *rw) 
{

	unsigned int old;

	old = rw->lock & 0x7fffffffU;

	if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))

	if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1)))

		return 1;

	return _raw_read_trylock_retry(rw);

}



static inline int arch_write_trylock(arch_rwlock_t *rw)

{

	if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))

	if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000)))

		return 1;

	return _raw_write_trylock_retry(rw);

}

arch/s390/include/asm/spinlock_types.h

+3 −3
Original line number Diff line number Diff line
@@ -6,13 +6,13 @@ 
#endif



typedef struct {

	volatile unsigned int owner_cpu;

	unsigned int lock;

} __attribute__ ((aligned (4))) arch_spinlock_t;



#define __ARCH_SPIN_LOCK_UNLOCKED	{ 0 }

#define __ARCH_SPIN_LOCK_UNLOCKED { .lock = 0, }



typedef struct {

	volatile unsigned int lock;

	unsigned int lock;

} arch_rwlock_t;



#define __ARCH_RW_LOCK_UNLOCKED		{ 0 }

arch/s390/lib/spinlock.c

+26 −29
Original line number Diff line number Diff line
@@ -31,22 +31,21 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) 
	unsigned int owner;



	while (1) {

		owner = lp->owner_cpu;

		owner = lp->lock;

		if (!owner || smp_vcpu_scheduled(~owner)) {

			for (count = spin_retry; count > 0; count--) {

				if (arch_spin_is_locked(lp))

					continue;

				if (_raw_compare_and_swap(&lp->owner_cpu, 0,

							  cpu) == 0)

				if (_raw_compare_and_swap(&lp->lock, 0, cpu))

					return;

			}

			if (MACHINE_IS_LPAR)

				continue;

		}

		owner = lp->owner_cpu;

		owner = lp->lock;

		if (owner)

			smp_yield_cpu(~owner);

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

		if (_raw_compare_and_swap(&lp->lock, 0, cpu))

			return;

	}

}
@@ -60,57 +59,55 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) 


	local_irq_restore(flags);

	while (1) {

		owner = lp->owner_cpu;

		owner = lp->lock;

		if (!owner || smp_vcpu_scheduled(~owner)) {

			for (count = spin_retry; count > 0; count--) {

				if (arch_spin_is_locked(lp))

					continue;

				local_irq_disable();

				if (_raw_compare_and_swap(&lp->owner_cpu, 0,

							  cpu) == 0)

				if (_raw_compare_and_swap(&lp->lock, 0, cpu))

					return;

				local_irq_restore(flags);

			}

			if (MACHINE_IS_LPAR)

				continue;

		}

		owner = lp->owner_cpu;

		owner = lp->lock;

		if (owner)

			smp_yield_cpu(~owner);

		local_irq_disable();

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

		if (_raw_compare_and_swap(&lp->lock, 0, cpu))

			return;

		local_irq_restore(flags);

	}

}

EXPORT_SYMBOL(arch_spin_lock_wait_flags);



void arch_spin_relax(arch_spinlock_t *lp)

{

	unsigned int cpu = lp->lock;

	if (cpu != 0) {

		if (MACHINE_IS_VM || MACHINE_IS_KVM ||

		    !smp_vcpu_scheduled(~cpu))

			smp_yield_cpu(~cpu);

	}

}

EXPORT_SYMBOL(arch_spin_relax);



int arch_spin_trylock_retry(arch_spinlock_t *lp)

{

	unsigned int cpu = ~smp_processor_id();

	int count;



	for (count = spin_retry; count > 0; count--) {

		if (arch_spin_is_locked(lp))

			continue;

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

		if (arch_spin_trylock_once(lp))

			return 1;

	}

	return 0;

}

EXPORT_SYMBOL(arch_spin_trylock_retry);



void arch_spin_relax(arch_spinlock_t *lock)

{

	unsigned int cpu = lock->owner_cpu;

	if (cpu != 0) {

		if (MACHINE_IS_VM || MACHINE_IS_KVM ||

		    !smp_vcpu_scheduled(~cpu))

			smp_yield_cpu(~cpu);

	}

}

EXPORT_SYMBOL(arch_spin_relax);



void _raw_read_lock_wait(arch_rwlock_t *rw)

{

	unsigned int old;
@@ -124,7 +121,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw) 
		if (!arch_read_can_lock(rw))

			continue;

		old = rw->lock & 0x7fffffffU;

		if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)

		if (_raw_compare_and_swap(&rw->lock, old, old + 1))

			return;

	}

}
@@ -145,7 +142,7 @@ void _raw_read_lock_wait_flags(arch_rwlock_t *rw, unsigned long flags) 
			continue;

		old = rw->lock & 0x7fffffffU;

		local_irq_disable();

		if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)

		if (_raw_compare_and_swap(&rw->lock, old, old + 1))

			return;

	}

}
@@ -160,7 +157,7 @@ int _raw_read_trylock_retry(arch_rwlock_t *rw) 
		if (!arch_read_can_lock(rw))

			continue;

		old = rw->lock & 0x7fffffffU;

		if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)

		if (_raw_compare_and_swap(&rw->lock, old, old + 1))

			return 1;

	}

	return 0;
@@ -178,7 +175,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw) 
		}

		if (!arch_write_can_lock(rw))

			continue;

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))

			return;

	}

}
@@ -197,7 +194,7 @@ void _raw_write_lock_wait_flags(arch_rwlock_t *rw, unsigned long flags) 
		if (!arch_write_can_lock(rw))

			continue;

		local_irq_disable();

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))

			return;

	}

}
@@ -210,7 +207,7 @@ int _raw_write_trylock_retry(arch_rwlock_t *rw) 
	while (count-- > 0) {

		if (!arch_write_can_lock(rw))

			continue;

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))

			return 1;

	}

	return 0;