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Commit d59b93da authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/rwlock: use directed yield for write-locked rwlocks 



Add an owner field to the arch_rwlock_t to be able to pass the timeslice
of a virtual CPU with diagnose 0x9c to the lock owner in case the rwlock
is write-locked. The undirected yield in case the rwlock is acquired
writable but the lock is read-locked is removed.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 46b05c7b

arch/s390/include/asm/smp.h

+0 −2
Original line number Diff line number Diff line
@@ -29,7 +29,6 @@ extern int smp_find_processor_id(u16 address); 
extern int smp_store_status(int cpu);

extern int smp_vcpu_scheduled(int cpu);

extern void smp_yield_cpu(int cpu);

extern void smp_yield(void);

extern void smp_cpu_set_polarization(int cpu, int val);

extern int smp_cpu_get_polarization(int cpu);

extern void smp_fill_possible_mask(void);
@@ -50,7 +49,6 @@ static inline int smp_find_processor_id(u16 address) { return 0; } 
static inline int smp_store_status(int cpu) { return 0; }

static inline int smp_vcpu_scheduled(int cpu) { return 1; }

static inline void smp_yield_cpu(int cpu) { }

static inline void smp_yield(void) { }

static inline void smp_fill_possible_mask(void) { }



#endif /* CONFIG_SMP */

arch/s390/include/asm/spinlock.h

+23 −5
Original line number Diff line number Diff line
@@ -37,11 +37,17 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new) 
 * (the type definitions are in asm/spinlock_types.h)

 */



void arch_lock_relax(unsigned int cpu);



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 void arch_spin_relax(arch_spinlock_t *lock)

{

	arch_lock_relax(lock->lock);

}



static inline u32 arch_spin_lockval(int cpu)

{

	return ~cpu;
@@ -170,17 +176,21 @@ static inline void arch_write_lock(arch_rwlock_t *rw) 
{

	if (!arch_write_trylock_once(rw))

		_raw_write_lock_wait(rw);

	rw->owner = SPINLOCK_LOCKVAL;

}



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

{

	if (!arch_write_trylock_once(rw))

		_raw_write_lock_wait_flags(rw, flags);

	rw->owner = SPINLOCK_LOCKVAL;

}



static inline void arch_write_unlock(arch_rwlock_t *rw)

{

	typecheck(unsigned int, rw->lock);



	rw->owner = 0;

	asm volatile(

		__ASM_BARRIER

		"st	%1,%0\n"
@@ -198,12 +208,20 @@ static inline int arch_read_trylock(arch_rwlock_t *rw) 


static inline int arch_write_trylock(arch_rwlock_t *rw)

{

	if (!arch_write_trylock_once(rw))

		return _raw_write_trylock_retry(rw);

	if (!arch_write_trylock_once(rw) && !_raw_write_trylock_retry(rw))

		return 0;

	rw->owner = SPINLOCK_LOCKVAL;

	return 1;

}



#define arch_read_relax(lock)	cpu_relax()

#define arch_write_relax(lock)	cpu_relax()

static inline void arch_read_relax(arch_rwlock_t *rw)

{

	arch_lock_relax(rw->owner);

}



static inline void arch_write_relax(arch_rwlock_t *rw)

{

	arch_lock_relax(rw->owner);

}



#endif /* __ASM_SPINLOCK_H */

arch/s390/include/asm/spinlock_types.h

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ typedef struct { 


typedef struct {

	unsigned int lock;

	unsigned int owner;

} arch_rwlock_t;



#define __ARCH_RW_LOCK_UNLOCKED		{ 0 }

arch/s390/kernel/smp.c

+0 −6
Original line number Diff line number Diff line
@@ -333,12 +333,6 @@ int smp_vcpu_scheduled(int cpu) 
	return pcpu_running(pcpu_devices + cpu);

}



void smp_yield(void)

{

	if (MACHINE_HAS_DIAG44)

		asm volatile("diag 0,0,0x44");

}



void smp_yield_cpu(int cpu)

{

	if (MACHINE_HAS_DIAG9C)

arch/s390/lib/spinlock.c

+30 −19
Original line number Diff line number Diff line
@@ -98,17 +98,6 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long 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)

{

	int count;
@@ -122,15 +111,18 @@ EXPORT_SYMBOL(arch_spin_trylock_retry); 


void _raw_read_lock_wait(arch_rwlock_t *rw)

{

	unsigned int old;

	unsigned int owner, old;

	int count = spin_retry;



	owner = 0;

	while (1) {

		if (count-- <= 0) {

			smp_yield();

			if (owner && !smp_vcpu_scheduled(~owner))

				smp_yield_cpu(~owner);

			count = spin_retry;

		}

		old = ACCESS_ONCE(rw->lock);

		owner = ACCESS_ONCE(rw->owner);

		if ((int) old < 0)

			continue;

		if (_raw_compare_and_swap(&rw->lock, old, old + 1))
@@ -141,16 +133,19 @@ EXPORT_SYMBOL(_raw_read_lock_wait); 


void _raw_read_lock_wait_flags(arch_rwlock_t *rw, unsigned long flags)

{

	unsigned int old;

	unsigned int owner, old;

	int count = spin_retry;



	local_irq_restore(flags);

	owner = 0;

	while (1) {

		if (count-- <= 0) {

			smp_yield();

			if (owner && !smp_vcpu_scheduled(~owner))

				smp_yield_cpu(~owner);

			count = spin_retry;

		}

		old = ACCESS_ONCE(rw->lock);

		owner = ACCESS_ONCE(rw->owner);

		if ((int) old < 0)

			continue;

		local_irq_disable();
@@ -179,15 +174,18 @@ EXPORT_SYMBOL(_raw_read_trylock_retry); 


void _raw_write_lock_wait(arch_rwlock_t *rw)

{

	unsigned int old;

	unsigned int owner, old;

	int count = spin_retry;



	owner = 0;

	while (1) {

		if (count-- <= 0) {

			smp_yield();

			if (owner && !smp_vcpu_scheduled(~owner))

				smp_yield_cpu(~owner);

			count = spin_retry;

		}

		old = ACCESS_ONCE(rw->lock);

		owner = ACCESS_ONCE(rw->owner);

		if (old)

			continue;

		if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))
@@ -198,16 +196,19 @@ EXPORT_SYMBOL(_raw_write_lock_wait); 


void _raw_write_lock_wait_flags(arch_rwlock_t *rw, unsigned long flags)

{

	unsigned int old;

	unsigned int owner, old;

	int count = spin_retry;



	local_irq_restore(flags);

	owner = 0;

	while (1) {

		if (count-- <= 0) {

			smp_yield();

			if (owner && !smp_vcpu_scheduled(~owner))

				smp_yield_cpu(~owner);

			count = spin_retry;

		}

		old = ACCESS_ONCE(rw->lock);

		owner = ACCESS_ONCE(rw->owner);

		if (old)

			continue;

		local_irq_disable();
@@ -233,3 +234,13 @@ int _raw_write_trylock_retry(arch_rwlock_t *rw) 
	return 0;

}

EXPORT_SYMBOL(_raw_write_trylock_retry);



void arch_lock_relax(unsigned int cpu)

{

	if (!cpu)

		return;

	if (MACHINE_IS_LPAR && smp_vcpu_scheduled(~cpu))

		return;

	smp_yield_cpu(~cpu);

}

EXPORT_SYMBOL(arch_lock_relax);