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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: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2014-09-19 14:29:31 +02:00
parent 46b05c7bd5
commit d59b93da5e
5 changed files with 54 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/s390/include/asm/smp.h
View File

@ -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 */

28
arch/s390/include/asm/spinlock.h
View File

@ -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 */

1
arch/s390/include/asm/spinlock_types.h
View File

@ -13,6 +13,7 @@ typedef struct {
typedef struct {
unsigned int lock;
unsigned int owner;
} arch_rwlock_t;
#define __ARCH_RW_LOCK_UNLOCKED { 0 }

6
arch/s390/kernel/smp.c
View File

@ -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)

49
arch/s390/lib/spinlock.c
View File

@ -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);