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| author | Mikael Pettersson <mikpe@it.uu.se> | 2011-08-15 12:11:50 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-08-15 23:35:19 +0200 |
| commit | 3f6aa0b113846a8628baa649af422cfc6fb1d786 (patch) | |
| tree | 5b3d1f9b112a779dab37db5f685c24e5e857df96 /arch/sparc | |
| parent | sparc64: remove unnecessary macros from spinlock_64.h (diff) | |
| download | linux-3f6aa0b113846a8628baa649af422cfc6fb1d786.tar.xz linux-3f6aa0b113846a8628baa649af422cfc6fb1d786.zip | |
sparc32: unbreak arch_write_unlock()
The sparc32 version of arch_write_unlock() is just a plain assignment.
Unfortunately this allows the compiler to schedule side-effects in a
protected region to occur after the HW-level unlock, which is broken.
E.g., the following trivial test case gets miscompiled:
#include <linux/spinlock.h>
rwlock_t lock;
int counter;
void foo(void) { write_lock(&lock); ++counter; write_unlock(&lock); }
Fixed by adding a compiler memory barrier to arch_write_unlock(). The
sparc64 version combines the barrier and assignment into a single asm(),
and implements the operation as a static inline, so that's what I did too.
Compile-tested with sparc32_defconfig + CONFIG_SMP=y.
Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc')
| -rw-r--r-- | arch/sparc/include/asm/spinlock_32.h | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/sparc/include/asm/spinlock_32.h b/arch/sparc/include/asm/spinlock_32.h index 5f5b8bf3f50d..bcc98fc35281 100644 --- a/arch/sparc/include/asm/spinlock_32.h +++ b/arch/sparc/include/asm/spinlock_32.h @@ -131,6 +131,15 @@ static inline void arch_write_lock(arch_rwlock_t *rw) *(volatile __u32 *)&lp->lock = ~0U; } +static void inline arch_write_unlock(arch_rwlock_t *lock) +{ + __asm__ __volatile__( +" st %%g0, [%0]" + : /* no outputs */ + : "r" (lock) + : "memory"); +} + static inline int arch_write_trylock(arch_rwlock_t *rw) { unsigned int val; @@ -175,8 +184,6 @@ static inline int __arch_read_trylock(arch_rwlock_t *rw) res; \ }) -#define arch_write_unlock(rw) do { (rw)->lock = 0; } while(0) - #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) #define arch_read_lock_flags(rw, flags) arch_read_lock(rw) #define arch_write_lock_flags(rw, flags) arch_write_lock(rw) |