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>

2 files changed, 108 insertions, 2 deletions

diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index f9537b91ff21..d6bdf906caa5 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -130,8 +130,6 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
  */
 #define arch_write_can_lock(x) ((x)->lock == 0)
 
-extern void _raw_read_lock_wait(arch_rwlock_t *lp);
-extern void _raw_write_lock_wait(arch_rwlock_t *lp);
 extern int _raw_read_trylock_retry(arch_rwlock_t *lp);
 extern int _raw_write_trylock_retry(arch_rwlock_t *lp);
 
@@ -152,6 +150,78 @@ static inline int arch_write_trylock_once(arch_rwlock_t *rw)
                       _raw_compare_and_swap(&rw->lock, 0, 0x80000000));
 }
 
+#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
+
+#define __RAW_OP_OR     "lao"
+#define __RAW_OP_AND    "lan"
+#define __RAW_OP_ADD    "laa"
+
+#define __RAW_LOCK(ptr, op_val, op_string)              \
+({                                                      \
+        unsigned int old_val;                           \
+                                                        \
+        typecheck(unsigned int *, ptr);                 \
+        asm volatile(                                   \
+                op_string "     %0,%2,%1\n"             \
+                "bcr    14,0\n"                         \
+                : "=d" (old_val), "+Q" (*ptr)           \
+                : "d" (op_val)                          \
+                : "cc", "memory");                      \
+        old_val;                                        \
+})
+
+#define __RAW_UNLOCK(ptr, op_val, op_string)            \
+({                                                      \
+        unsigned int old_val;                           \
+                                                        \
+        typecheck(unsigned int *, ptr);                 \
+        asm volatile(                                   \
+                "bcr    14,0\n"                         \
+                op_string "     %0,%2,%1\n"             \
+                : "=d" (old_val), "+Q" (*ptr)           \
+                : "d" (op_val)                          \
+                : "cc", "memory");                      \
+        old_val;                                        \
+})
+
+extern void _raw_read_lock_wait(arch_rwlock_t *lp);
+extern void _raw_write_lock_wait(arch_rwlock_t *lp, unsigned int prev);
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+        unsigned int old;
+
+        old = __RAW_LOCK(&rw->lock, 1, __RAW_OP_ADD);
+        if ((int) old < 0)
+                _raw_read_lock_wait(rw);
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+        __RAW_UNLOCK(&rw->lock, -1, __RAW_OP_ADD);
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+        unsigned int old;
+
+        old = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR);
+        if (old != 0)
+                _raw_write_lock_wait(rw, old);
+        rw->owner = SPINLOCK_LOCKVAL;
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+        rw->owner = 0;
+        __RAW_UNLOCK(&rw->lock, 0x7fffffff, __RAW_OP_AND);
+}
+
+#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
+
+extern void _raw_read_lock_wait(arch_rwlock_t *lp);
+extern void _raw_write_lock_wait(arch_rwlock_t *lp);
+
 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
         if (!arch_read_trylock_once(rw))
@@ -187,6 +257,8 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
                 : "cc", "memory");
 }
 
+#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
+
 static inline int arch_read_trylock(arch_rwlock_t *rw)
 {
         if (!arch_read_trylock_once(rw))
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;