[PATCH] ARM SMP: Add ARMv6 memory barriers

Convert explicit gcc asm-based memory barriers into smp_mb() calls.
These change between barrier() and the ARMv6 data memory barrier
instruction depending on whether ARMv6 SMP is enabled.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 69 insertions, 29 deletions

diff --git a/include/asm-arm/bitops.h b/include/asm-arm/bitops.h
index 4edd4dc40c5..c1adc6b3e86 100644
--- a/include/asm-arm/bitops.h
+++ b/include/asm-arm/bitops.h
@@ -21,8 +21,8 @@
 
 #include <asm/system.h>
 
-#define smp_mb__before_clear_bit()      do { } while (0)
-#define smp_mb__after_clear_bit()       do { } while (0)
+#define smp_mb__before_clear_bit()      mb()
+#define smp_mb__after_clear_bit()       mb()
 
 /*
  * These functions are the basis of our bit ops.
diff --git a/include/asm-arm/locks.h b/include/asm-arm/locks.h
index 9cb33fcc06c..f08dc844791 100644
--- a/include/asm-arm/locks.h
+++ b/include/asm-arm/locks.h
@@ -28,7 +28,8 @@
 "       blmi    " #fail                         \
         :                                       \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         })
 
 #define __down_op_ret(ptr,fail)                 \
@@ -48,12 +49,14 @@
 "       mov     %0, ip"                         \
         : "=&r" (ret)                           \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         ret;                                    \
         })
 
 #define __up_op(ptr,wake)                       \
         ({                                      \
+        smp_mb();                               \
         __asm__ __volatile__(                   \
         "@ up_op\n"                             \
 "1:     ldrex   lr, [%0]\n"                     \
@@ -66,7 +69,7 @@
 "       blle    " #wake                         \
         :                                       \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
         })
 
 /*
@@ -92,11 +95,13 @@
 "       blne    " #fail                         \
         :                                       \
         : "r" (ptr), "I" (RW_LOCK_BIAS)         \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         })
 
 #define __up_op_write(ptr,wake)                 \
         ({                                      \
+        smp_mb();                               \
         __asm__ __volatile__(                   \
         "@ up_op_read\n"                        \
 "1:     ldrex   lr, [%0]\n"                     \
@@ -108,7 +113,7 @@
 "       blcs    " #wake                         \
         :                                       \
         : "r" (ptr), "I" (RW_LOCK_BIAS)         \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
         })
 
 #define __down_op_read(ptr,fail)                \
@@ -116,6 +121,7 @@
 
 #define __up_op_read(ptr,wake)                  \
         ({                                      \
+        smp_mb();                               \
         __asm__ __volatile__(                   \
         "@ up_op_read\n"                        \
 "1:     ldrex   lr, [%0]\n"                     \
@@ -128,7 +134,7 @@
 "       bleq    " #wake                         \
         :                                       \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
         })
 
 #else
@@ -148,7 +154,8 @@
 "       blmi    " #fail                         \
         :                                       \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         })
 
 #define __down_op_ret(ptr,fail)                 \
@@ -169,12 +176,14 @@
 "       mov     %0, ip"                         \
         : "=&r" (ret)                           \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         ret;                                    \
         })
 
 #define __up_op(ptr,wake)                       \
         ({                                      \
+        smp_mb();                               \
         __asm__ __volatile__(                   \
         "@ up_op\n"                             \
 "       mrs     ip, cpsr\n"                     \
@@ -188,7 +197,7 @@
 "       blle    " #wake                         \
         :                                       \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
         })
 
 /*
@@ -215,7 +224,8 @@
 "       blne    " #fail                         \
         :                                       \
         : "r" (ptr), "I" (RW_LOCK_BIAS)         \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         })
 
 #define __up_op_write(ptr,wake)                 \
@@ -233,7 +243,8 @@
 "       blcs    " #wake                         \
         :                                       \
         : "r" (ptr), "I" (RW_LOCK_BIAS)         \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
+        smp_mb();                               \
         })
 
 #define __down_op_read(ptr,fail)                \
@@ -241,6 +252,7 @@
 
 #define __up_op_read(ptr,wake)                  \
         ({                                      \
+        smp_mb();                               \
         __asm__ __volatile__(                   \
         "@ up_op_read\n"                        \
 "       mrs     ip, cpsr\n"                     \
@@ -254,7 +266,7 @@
 "       bleq    " #wake                         \
         :                                       \
         : "r" (ptr), "I" (1)                    \
-        : "ip", "lr", "cc", "memory");          \
+        : "ip", "lr", "cc");                    \
         })
 
 #endif
diff --git a/include/asm-arm/spinlock.h b/include/asm-arm/spinlock.h
index 9705d5eec94..1f906d09b68 100644
--- a/include/asm-arm/spinlock.h
+++ b/include/asm-arm/spinlock.h
@@ -8,9 +8,10 @@
 /*
  * ARMv6 Spin-locking.
  *
- * We (exclusively) read the old value, and decrement it.  If it
- * hits zero, we may have won the lock, so we try (exclusively)
- * storing it.
+ * We exclusively read the old value.  If it is zero, we may have
+ * won the lock, so we try exclusively storing it.  A memory barrier
+ * is required after we get a lock, and before we release it, because
+ * V6 CPUs are assumed to have weakly ordered memory.
  *
  * Unlocked value: 0
  * Locked value: 1
@@ -41,7 +42,9 @@ static inline void _raw_spin_lock(spinlock_t *lock)
 "       bne     1b"
         : "=&r" (tmp)
         : "r" (&lock->lock), "r" (1)
-        : "cc", "memory");
+        : "cc");
+
+        smp_mb();
 }
 
 static inline int _raw_spin_trylock(spinlock_t *lock)
@@ -54,18 +57,25 @@ static inline int _raw_spin_trylock(spinlock_t *lock)
 "       strexeq %0, %2, [%1]"
         : "=&r" (tmp)
         : "r" (&lock->lock), "r" (1)
-        : "cc", "memory");
-
-        return tmp == 0;
+        : "cc");
+
+        if (tmp == 0) {
+                smp_mb();
+                return 1;
+        } else {
+                return 0;
+        }
 }
 
 static inline void _raw_spin_unlock(spinlock_t *lock)
 {
+        smp_mb();
+
         __asm__ __volatile__(
 "       str     %1, [%0]"
         :
         : "r" (&lock->lock), "r" (0)
-        : "cc", "memory");
+        : "cc");
 }
 
 /*
@@ -98,7 +108,9 @@ static inline void _raw_write_lock(rwlock_t *rw)
 "       bne     1b"
         : "=&r" (tmp)
         : "r" (&rw->lock), "r" (0x80000000)
-        : "cc", "memory");
+        : "cc");
+
+        smp_mb();
 }
 
 static inline int _raw_write_trylock(rwlock_t *rw)
@@ -111,18 +123,25 @@ static inline int _raw_write_trylock(rwlock_t *rw)
 "       strexeq %0, %2, [%1]"
         : "=&r" (tmp)
         : "r" (&rw->lock), "r" (0x80000000)
-        : "cc", "memory");
-
-        return tmp == 0;
+        : "cc");
+
+        if (tmp == 0) {
+                smp_mb();
+                return 1;
+        } else {
+                return 0;
+        }
 }
 
 static inline void _raw_write_unlock(rwlock_t *rw)
 {
+        smp_mb();
+
         __asm__ __volatile__(
         "str    %1, [%0]"
         :
         : "r" (&rw->lock), "r" (0)
-        : "cc", "memory");
+        : "cc");
 }
 
 /*
@@ -149,13 +168,17 @@ static inline void _raw_read_lock(rwlock_t *rw)
 "       bmi     1b"
         : "=&r" (tmp), "=&r" (tmp2)
         : "r" (&rw->lock)
-        : "cc", "memory");
+        : "cc");
+
+        smp_mb();
 }
 
 static inline void _raw_read_unlock(rwlock_t *rw)
 {
         unsigned long tmp, tmp2;
 
+        smp_mb();
+
         __asm__ __volatile__(
 "1:     ldrex   %0, [%2]\n"
 "       sub     %0, %0, #1\n"
@@ -164,7 +187,7 @@ static inline void _raw_read_unlock(rwlock_t *rw)
 "       bne     1b"
         : "=&r" (tmp), "=&r" (tmp2)
         : "r" (&rw->lock)
-        : "cc", "memory");
+        : "cc");
 }
 
 #define _raw_read_trylock(lock) generic_raw_read_trylock(lock)
diff --git a/include/asm-arm/system.h b/include/asm-arm/system.h
index 3f9c3626a73..8efa4ebdcac 100644
--- a/include/asm-arm/system.h
+++ b/include/asm-arm/system.h
@@ -139,7 +139,12 @@ extern unsigned int user_debug;
 #define vectors_high()  (0)
 #endif
 
+#if __LINUX_ARM_ARCH__ >= 6
+#define mb() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" \
+                                   : : "r" (0) : "memory")
+#else
 #define mb() __asm__ __volatile__ ("" : : : "memory")
+#endif
 #define rmb() mb()
 #define wmb() mb()
 #define read_barrier_depends() do { } while(0)