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>

1 files changed, 26 insertions, 29 deletions

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index f709983f41f8..4a3b33b2dbb9 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -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;