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>
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 83e5d216..b60212a 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -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;
}
/*
@@ -34,57 +35,66 @@
* (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;
- arch_spin_lock_wait(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)
+ unsigned long flags)
{
- int old;
-
- old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
- if (likely(old == 0))
- return;
- arch_spin_lock_wait_flags(lp, flags);
+ 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;
- return arch_spin_trylock_retry(lp);
+ 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);
+}
+
/*
* Read-write spinlocks, allowing multiple readers
* but only one writer.
@@ -119,7 +129,7 @@
{
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 @@
{
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 @@
{
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);
}