s390/rwlock: use the interlocked-access facility 1 instructions

Make use of the load-and-add, load-and-or and load-and-and instructions
to atomically update the read-write lock without a compare-and-swap loop.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 01f29bb9c71b..034a35a3e9c1 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -114,6 +114,9 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
         unsigned int owner, old;
         int count = spin_retry;
 
+#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
+        __RAW_LOCK(&rw->lock, -1, __RAW_OP_ADD);
+#endif
         owner = 0;
         while (1) {
                 if (count-- <= 0) {
@@ -147,6 +150,35 @@ int _raw_read_trylock_retry(arch_rwlock_t *rw)
 }
 EXPORT_SYMBOL(_raw_read_trylock_retry);
 
+#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
+
+void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
+{
+        unsigned int owner, old;
+        int count = spin_retry;
+
+        owner = 0;
+        while (1) {
+                if (count-- <= 0) {
+                        if (owner && !smp_vcpu_scheduled(~owner))
+                                smp_yield_cpu(~owner);
+                        count = spin_retry;
+                }
+                old = ACCESS_ONCE(rw->lock);
+                owner = ACCESS_ONCE(rw->owner);
+                smp_rmb();
+                if ((int) old >= 0) {
+                        prev = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR);
+                        old = prev;
+                }
+                if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
+                        break;
+        }
+}
+EXPORT_SYMBOL(_raw_write_lock_wait);
+
+#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
+
 void _raw_write_lock_wait(arch_rwlock_t *rw)
 {
         unsigned int owner, old, prev;
@@ -173,6 +205,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
 }
 EXPORT_SYMBOL(_raw_write_lock_wait);
 
+#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
+
 int _raw_write_trylock_retry(arch_rwlock_t *rw)
 {
         unsigned int old;