arm64: atomics: fix grossly inconsistent asm constraints for exclusives

Our uses of inline asm constraints for atomic operations are fairly
wild and varied. We basically need to guarantee the following:

  1. Any instructions with barrier implications
     (load-acquire/store-release) have a "memory" clobber

  2. When performing exclusive accesses, the addresing mode is generated
     using the "Q" constraint

  3. Atomic blocks which use the condition flags, have a "cc" clobber

This patch addresses these concerns which, as well as fixing the
semantics of the code, stops GCC complaining about impossible asm
constraints.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/atomic.h b/arch/arm64/include/asm/atomic.h
index 407717ba060e6b5525deb1b33158d936a4d7202a..8363644685711895cbb049c735b6ebb15cf81ff1 100644 (file)
--- a/arch/arm64/include/asm/atomic.h
+++ b/arch/arm64/include/asm/atomic.h
@@ -49,12 +49,12 @@ static inline void atomic_add(int i, atomic_t *v)
        int result;
 
        asm volatile("// atomic_add\n"
-"1:    ldxr    %w0, [%3]\n"
-"      add     %w0, %w0, %w4\n"
-"      stxr    %w1, %w0, [%3]\n"
+"1:    ldxr    %w0, %2\n"
+"      add     %w0, %w0, %w3\n"
+"      stxr    %w1, %w0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
        : "cc");
 }
 
@@ -64,13 +64,13 @@ static inline int atomic_add_return(int i, atomic_t *v)
        int result;
 
        asm volatile("// atomic_add_return\n"
-"1:    ldaxr   %w0, [%3]\n"
-"      add     %w0, %w0, %w4\n"
-"      stlxr   %w1, %w0, [%3]\n"
+"1:    ldaxr   %w0, %2\n"
+"      add     %w0, %w0, %w3\n"
+"      stlxr   %w1, %w0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
-       : "cc");
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
+       : "cc", "memory");
 
        return result;
 }
@@ -81,12 +81,12 @@ static inline void atomic_sub(int i, atomic_t *v)
        int result;
 
        asm volatile("// atomic_sub\n"
-"1:    ldxr    %w0, [%3]\n"
-"      sub     %w0, %w0, %w4\n"
-"      stxr    %w1, %w0, [%3]\n"
+"1:    ldxr    %w0, %2\n"
+"      sub     %w0, %w0, %w3\n"
+"      stxr    %w1, %w0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
        : "cc");
 }
 
@@ -96,13 +96,13 @@ static inline int atomic_sub_return(int i, atomic_t *v)
        int result;
 
        asm volatile("// atomic_sub_return\n"
-"1:    ldaxr   %w0, [%3]\n"
-"      sub     %w0, %w0, %w4\n"
-"      stlxr   %w1, %w0, [%3]\n"
+"1:    ldaxr   %w0, %2\n"
+"      sub     %w0, %w0, %w3\n"
+"      stlxr   %w1, %w0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
-       : "cc");
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
+       : "cc", "memory");
 
        return result;
 }
@@ -113,15 +113,15 @@ static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new)
        int oldval;
 
        asm volatile("// atomic_cmpxchg\n"
-"1:    ldaxr   %w1, [%3]\n"
-"      cmp     %w1, %w4\n"
+"1:    ldaxr   %w1, %2\n"
+"      cmp     %w1, %w3\n"
 "      b.ne    2f\n"
-"      stlxr   %w0, %w5, [%3]\n"
+"      stlxr   %w0, %w4, %2\n"
 "      cbnz    %w0, 1b\n"
 "2:"
-       : "=&r" (tmp), "=&r" (oldval), "+o" (ptr->counter)
-       : "r" (&ptr->counter), "Ir" (old), "r" (new)
-       : "cc");
+       : "=&r" (tmp), "=&r" (oldval), "+Q" (ptr->counter)
+       : "Ir" (old), "r" (new)
+       : "cc", "memory");
 
        return oldval;
 }
@@ -131,12 +131,12 @@ static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
        unsigned long tmp, tmp2;
 
        asm volatile("// atomic_clear_mask\n"
-"1:    ldxr    %0, [%3]\n"
-"      bic     %0, %0, %4\n"
-"      stxr    %w1, %0, [%3]\n"
+"1:    ldxr    %0, %2\n"
+"      bic     %0, %0, %3\n"
+"      stxr    %w1, %0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (tmp), "=&r" (tmp2), "+o" (*addr)
-       : "r" (addr), "Ir" (mask)
+       : "=&r" (tmp), "=&r" (tmp2), "+Q" (*addr)
+       : "Ir" (mask)
        : "cc");
 }
 
@@ -182,12 +182,12 @@ static inline void atomic64_add(u64 i, atomic64_t *v)
        unsigned long tmp;
 
        asm volatile("// atomic64_add\n"
-"1:    ldxr    %0, [%3]\n"
-"      add     %0, %0, %4\n"
-"      stxr    %w1, %0, [%3]\n"
+"1:    ldxr    %0, %2\n"
+"      add     %0, %0, %3\n"
+"      stxr    %w1, %0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
        : "cc");
 }
 
@@ -197,13 +197,13 @@ static inline long atomic64_add_return(long i, atomic64_t *v)
        unsigned long tmp;
 
        asm volatile("// atomic64_add_return\n"
-"1:    ldaxr   %0, [%3]\n"
-"      add     %0, %0, %4\n"
-"      stlxr   %w1, %0, [%3]\n"
+"1:    ldaxr   %0, %2\n"
+"      add     %0, %0, %3\n"
+"      stlxr   %w1, %0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
-       : "cc");
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
+       : "cc", "memory");
 
        return result;
 }
@@ -214,12 +214,12 @@ static inline void atomic64_sub(u64 i, atomic64_t *v)
        unsigned long tmp;
 
        asm volatile("// atomic64_sub\n"
-"1:    ldxr    %0, [%3]\n"
-"      sub     %0, %0, %4\n"
-"      stxr    %w1, %0, [%3]\n"
+"1:    ldxr    %0, %2\n"
+"      sub     %0, %0, %3\n"
+"      stxr    %w1, %0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
        : "cc");
 }
 
@@ -229,13 +229,13 @@ static inline long atomic64_sub_return(long i, atomic64_t *v)
        unsigned long tmp;
 
        asm volatile("// atomic64_sub_return\n"
-"1:    ldaxr   %0, [%3]\n"
-"      sub     %0, %0, %4\n"
-"      stlxr   %w1, %0, [%3]\n"
+"1:    ldaxr   %0, %2\n"
+"      sub     %0, %0, %3\n"
+"      stlxr   %w1, %0, %2\n"
 "      cbnz    %w1, 1b"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter), "Ir" (i)
-       : "cc");
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       : "Ir" (i)
+       : "cc", "memory");
 
        return result;
 }
@@ -246,15 +246,15 @@ static inline long atomic64_cmpxchg(atomic64_t *ptr, long old, long new)
        unsigned long res;
 
        asm volatile("// atomic64_cmpxchg\n"
-"1:    ldaxr   %1, [%3]\n"
-"      cmp     %1, %4\n"
+"1:    ldaxr   %1, %2\n"
+"      cmp     %1, %3\n"
 "      b.ne    2f\n"
-"      stlxr   %w0, %5, [%3]\n"
+"      stlxr   %w0, %4, %2\n"
 "      cbnz    %w0, 1b\n"
 "2:"
-       : "=&r" (res), "=&r" (oldval), "+o" (ptr->counter)
-       : "r" (&ptr->counter), "Ir" (old), "r" (new)
-       : "cc");
+       : "=&r" (res), "=&r" (oldval), "+Q" (ptr->counter)
+       : "Ir" (old), "r" (new)
+       : "cc", "memory");
 
        return oldval;
 }
@@ -267,15 +267,15 @@ static inline long atomic64_dec_if_positive(atomic64_t *v)
        unsigned long tmp;
 
        asm volatile("// atomic64_dec_if_positive\n"
-"1:    ldaxr   %0, [%3]\n"
+"1:    ldaxr   %0, %2\n"
 "      subs    %0, %0, #1\n"
 "      b.mi    2f\n"
-"      stlxr   %w1, %0, [%3]\n"
+"      stlxr   %w1, %0, %2\n"
 "      cbnz    %w1, 1b\n"
 "2:"
-       : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
-       : "r" (&v->counter)
-       : "cc");
+       : "=&r" (result), "=&r" (tmp), "+Q" (v->counter)
+       :
+       : "cc", "memory");
 
        return result;
 }

diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
index e0e65b069d9e82c21a71a041346145a8bb700915..968b5cbfc260590b8729088027072ce9db7cd0d9 100644 (file)
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -29,39 +29,39 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
        switch (size) {
        case 1:
                asm volatile("//        __xchg1\n"
-               "1:     ldaxrb  %w0, [%3]\n"
-               "       stlxrb  %w1, %w2, [%3]\n"
+               "1:     ldaxrb  %w0, %2\n"
+               "       stlxrb  %w1, %w3, %2\n"
                "       cbnz    %w1, 1b\n"
-                       : "=&r" (ret), "=&r" (tmp)
-                       : "r" (x), "r" (ptr)
-                       : "memory", "cc");
+                       : "=&r" (ret), "=&r" (tmp), "+Q" (*(u8 *)ptr)
+                       : "r" (x)
+                       : "cc", "memory");
                break;
        case 2:
                asm volatile("//        __xchg2\n"
-               "1:     ldaxrh  %w0, [%3]\n"
-               "       stlxrh  %w1, %w2, [%3]\n"
+               "1:     ldaxrh  %w0, %2\n"
+               "       stlxrh  %w1, %w3, %2\n"
                "       cbnz    %w1, 1b\n"
-                       : "=&r" (ret), "=&r" (tmp)
-                       : "r" (x), "r" (ptr)
-                       : "memory", "cc");
+                       : "=&r" (ret), "=&r" (tmp), "+Q" (*(u16 *)ptr)
+                       : "r" (x)
+                       : "cc", "memory");
                break;
        case 4:
                asm volatile("//        __xchg4\n"
-               "1:     ldaxr   %w0, [%3]\n"
-               "       stlxr   %w1, %w2, [%3]\n"
+               "1:     ldaxr   %w0, %2\n"
+               "       stlxr   %w1, %w3, %2\n"
                "       cbnz    %w1, 1b\n"
-                       : "=&r" (ret), "=&r" (tmp)
-                       : "r" (x), "r" (ptr)
-                       : "memory", "cc");
+                       : "=&r" (ret), "=&r" (tmp), "+Q" (*(u32 *)ptr)
+                       : "r" (x)
+                       : "cc", "memory");
                break;
        case 8:
                asm volatile("//        __xchg8\n"
-               "1:     ldaxr   %0, [%3]\n"
-               "       stlxr   %w1, %2, [%3]\n"
+               "1:     ldaxr   %0, %2\n"
+               "       stlxr   %w1, %3, %2\n"
                "       cbnz    %w1, 1b\n"
-                       : "=&r" (ret), "=&r" (tmp)
-                       : "r" (x), "r" (ptr)
-                       : "memory", "cc");
+                       : "=&r" (ret), "=&r" (tmp), "+Q" (*(u64 *)ptr)
+                       : "r" (x)
+                       : "cc", "memory");
                break;
        default:
                BUILD_BUG();
@@ -82,14 +82,14 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
        case 1:
                do {
                        asm volatile("// __cmpxchg1\n"
-                       "       ldxrb   %w1, [%2]\n"
+                       "       ldxrb   %w1, %2\n"
                        "       mov     %w0, #0\n"
                        "       cmp     %w1, %w3\n"
                        "       b.ne    1f\n"
-                       "       stxrb   %w0, %w4, [%2]\n"
+                       "       stxrb   %w0, %w4, %2\n"
                        "1:\n"
-                               : "=&r" (res), "=&r" (oldval)
-                               : "r" (ptr), "Ir" (old), "r" (new)
+                               : "=&r" (res), "=&r" (oldval), "+Q" (*(u8 *)ptr)
+                               : "Ir" (old), "r" (new)
                                : "cc");
                } while (res);
                break;
@@ -97,29 +97,29 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
        case 2:
                do {
                        asm volatile("// __cmpxchg2\n"
-                       "       ldxrh   %w1, [%2]\n"
+                       "       ldxrh   %w1, %2\n"
                        "       mov     %w0, #0\n"
                        "       cmp     %w1, %w3\n"
                        "       b.ne    1f\n"
-                       "       stxrh   %w0, %w4, [%2]\n"
+                       "       stxrh   %w0, %w4, %2\n"
                        "1:\n"
-                               : "=&r" (res), "=&r" (oldval)
-                               : "r" (ptr), "Ir" (old), "r" (new)
-                               : "memory", "cc");
+                               : "=&r" (res), "=&r" (oldval), "+Q" (*(u16 *)ptr)
+                               : "Ir" (old), "r" (new)
+                               : "cc");
                } while (res);
                break;
 
        case 4:
                do {
                        asm volatile("// __cmpxchg4\n"
-                       "       ldxr    %w1, [%2]\n"
+                       "       ldxr    %w1, %2\n"
                        "       mov     %w0, #0\n"
                        "       cmp     %w1, %w3\n"
                        "       b.ne    1f\n"
-                       "       stxr    %w0, %w4, [%2]\n"
+                       "       stxr    %w0, %w4, %2\n"
                        "1:\n"
-                               : "=&r" (res), "=&r" (oldval)
-                               : "r" (ptr), "Ir" (old), "r" (new)
+                               : "=&r" (res), "=&r" (oldval), "+Q" (*(u32 *)ptr)
+                               : "Ir" (old), "r" (new)
                                : "cc");
                } while (res);
                break;
@@ -127,14 +127,14 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
        case 8:
                do {
                        asm volatile("// __cmpxchg8\n"
-                       "       ldxr    %1, [%2]\n"
+                       "       ldxr    %1, %2\n"
                        "       mov     %w0, #0\n"
                        "       cmp     %1, %3\n"
                        "       b.ne    1f\n"
-                       "       stxr    %w0, %4, [%2]\n"
+                       "       stxr    %w0, %4, %2\n"
                        "1:\n"
-                               : "=&r" (res), "=&r" (oldval)
-                               : "r" (ptr), "Ir" (old), "r" (new)
+                               : "=&r" (res), "=&r" (oldval), "+Q" (*(u64 *)ptr)
+                               : "Ir" (old), "r" (new)
                                : "cc");
                } while (res);
                break;

diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index 3468ae8439fa4e219546590209ecd77c123d0824..c582fa316366805fc2b3921f27a67fd18a2aa43c 100644 (file)
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -39,7 +39,7 @@
 "      .popsection\n"                                                  \
        : "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp)       \
        : "r" (oparg), "Ir" (-EFAULT)                                   \
-       : "cc")
+       : "cc", "memory")
 
 static inline int
 futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)

diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index 41112fe2f8b18fb26cb9d729dd0f9b3cf9e20563..7065e920149d3d0ec6e9ed549e71a5040aa0a5d2 100644 (file)
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -45,13 +45,13 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
        asm volatile(
        "       sevl\n"
        "1:     wfe\n"
-       "2:     ldaxr   %w0, [%1]\n"
+       "2:     ldaxr   %w0, %1\n"
        "       cbnz    %w0, 1b\n"
-       "       stxr    %w0, %w2, [%1]\n"
+       "       stxr    %w0, %w2, %1\n"
        "       cbnz    %w0, 2b\n"
-       : "=&r" (tmp)
-       : "r" (&lock->lock), "r" (1)
-       : "memory");
+       : "=&r" (tmp), "+Q" (lock->lock)
+       : "r" (1)
+       : "cc", "memory");
 }
 
 static inline int arch_spin_trylock(arch_spinlock_t *lock)
@@ -59,13 +59,13 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
        unsigned int tmp;
 
        asm volatile(
-       "       ldaxr   %w0, [%1]\n"
+       "       ldaxr   %w0, %1\n"
        "       cbnz    %w0, 1f\n"
-       "       stxr    %w0, %w2, [%1]\n"
+       "       stxr    %w0, %w2, %1\n"
        "1:\n"
-       : "=&r" (tmp)
-       : "r" (&lock->lock), "r" (1)
-       : "memory");
+       : "=&r" (tmp), "+Q" (lock->lock)
+       : "r" (1)
+       : "cc", "memory");
 
        return !tmp;
 }
@@ -73,8 +73,8 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 {
        asm volatile(
-       "       stlr    %w1, [%0]\n"
-       : : "r" (&lock->lock), "r" (0) : "memory");
+       "       stlr    %w1, %0\n"
+       : "=Q" (lock->lock) : "r" (0) : "memory");
 }
 
 /*
@@ -94,13 +94,13 @@ static inline void arch_write_lock(arch_rwlock_t *rw)
        asm volatile(
        "       sevl\n"
        "1:     wfe\n"
-       "2:     ldaxr   %w0, [%1]\n"
+       "2:     ldaxr   %w0, %1\n"
        "       cbnz    %w0, 1b\n"
-       "       stxr    %w0, %w2, [%1]\n"
+       "       stxr    %w0, %w2, %1\n"
        "       cbnz    %w0, 2b\n"
-       : "=&r" (tmp)
-       : "r" (&rw->lock), "r" (0x80000000)
-       : "memory");
+       : "=&r" (tmp), "+Q" (rw->lock)
+       : "r" (0x80000000)
+       : "cc", "memory");
 }
 
 static inline int arch_write_trylock(arch_rwlock_t *rw)
@@ -108,13 +108,13 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
        unsigned int tmp;
 
        asm volatile(
-       "       ldaxr   %w0, [%1]\n"
+       "       ldaxr   %w0, %1\n"
        "       cbnz    %w0, 1f\n"
-       "       stxr    %w0, %w2, [%1]\n"
+       "       stxr    %w0, %w2, %1\n"
        "1:\n"
-       : "=&r" (tmp)
-       : "r" (&rw->lock), "r" (0x80000000)
-       : "memory");
+       : "=&r" (tmp), "+Q" (rw->lock)
+       : "r" (0x80000000)
+       : "cc", "memory");
 
        return !tmp;
 }
@@ -122,8 +122,8 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
 static inline void arch_write_unlock(arch_rwlock_t *rw)
 {
        asm volatile(
-       "       stlr    %w1, [%0]\n"
-       : : "r" (&rw->lock), "r" (0) : "memory");
+       "       stlr    %w1, %0\n"
+       : "=Q" (rw->lock) : "r" (0) : "memory");
 }
 
 /* write_can_lock - would write_trylock() succeed? */
@@ -148,14 +148,14 @@ static inline void arch_read_lock(arch_rwlock_t *rw)
        asm volatile(
        "       sevl\n"
        "1:     wfe\n"
-       "2:     ldaxr   %w0, [%2]\n"
+       "2:     ldaxr   %w0, %2\n"
        "       add     %w0, %w0, #1\n"
        "       tbnz    %w0, #31, 1b\n"
-       "       stxr    %w1, %w0, [%2]\n"
+       "       stxr    %w1, %w0, %2\n"
        "       cbnz    %w1, 2b\n"
-       : "=&r" (tmp), "=&r" (tmp2)
-       : "r" (&rw->lock)
-       : "memory");
+       : "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
+       :
+       : "cc", "memory");
 }
 
 static inline void arch_read_unlock(arch_rwlock_t *rw)
@@ -163,13 +163,13 @@ static inline void arch_read_unlock(arch_rwlock_t *rw)
        unsigned int tmp, tmp2;
 
        asm volatile(
-       "1:     ldxr    %w0, [%2]\n"
+       "1:     ldxr    %w0, %2\n"
        "       sub     %w0, %w0, #1\n"
-       "       stlxr   %w1, %w0, [%2]\n"
+       "       stlxr   %w1, %w0, %2\n"
        "       cbnz    %w1, 1b\n"
-       : "=&r" (tmp), "=&r" (tmp2)
-       : "r" (&rw->lock)
-       : "memory");
+       : "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
+       :
+       : "cc", "memory");
 }
 
 static inline int arch_read_trylock(arch_rwlock_t *rw)
@@ -177,14 +177,14 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
        unsigned int tmp, tmp2 = 1;
 
        asm volatile(
-       "       ldaxr   %w0, [%2]\n"
+       "       ldaxr   %w0, %2\n"
        "       add     %w0, %w0, #1\n"
        "       tbnz    %w0, #31, 1f\n"
-       "       stxr    %w1, %w0, [%2]\n"
+       "       stxr    %w1, %w0, %2\n"
        "1:\n"
-       : "=&r" (tmp), "+r" (tmp2)
-       : "r" (&rw->lock)
-       : "memory");
+       : "=&r" (tmp), "+r" (tmp2), "+Q" (rw->lock)
+       :
+       : "cc", "memory");
 
        return !tmp2;
 }