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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: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Philipp Hachtmann 2014-04-07 18:25:23 +02:00 committed by Martin Schwidefsky
parent 50be634507
commit 5b3f683e69
3 changed files with 86 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

88
arch/s390/include/asm/spinlock.h
View File

@ -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 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)
{
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);
}
static inline void arch_spin_lock(arch_spinlock_t *lp)
{
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(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);
}

6
arch/s390/include/asm/spinlock_types.h
View File

@ -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 }

63
arch/s390/lib/spinlock.c
View File

@ -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;
}
}
@ -60,49 +59,33 @@ 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);
int arch_spin_trylock_retry(arch_spinlock_t *lp)
void arch_spin_relax(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)
return 1;
}
return 0;
}
EXPORT_SYMBOL(arch_spin_trylock_retry);
void arch_spin_relax(arch_spinlock_t *lock)
{
unsigned int cpu = lock->owner_cpu;
unsigned int cpu = lp->lock;
if (cpu != 0) {
if (MACHINE_IS_VM || MACHINE_IS_KVM ||
!smp_vcpu_scheduled(~cpu))
@ -111,6 +94,20 @@ void arch_spin_relax(arch_spinlock_t *lock)
}
EXPORT_SYMBOL(arch_spin_relax);
int arch_spin_trylock_retry(arch_spinlock_t *lp)
{
int count;
for (count = spin_retry; count > 0; count--) {
if (arch_spin_is_locked(lp))
continue;
if (arch_spin_trylock_once(lp))
return 1;
}
return 0;
}
EXPORT_SYMBOL(arch_spin_trylock_retry);
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;