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Diffstat (limited to 'include/linux/spinlock_up.h')
-rw-r--r--include/linux/spinlock_up.h29
1 files changed, 18 insertions, 11 deletions
diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
index a26e2fb604e6..e2369c167dbd 100644
--- a/include/linux/spinlock_up.h
+++ b/include/linux/spinlock_up.h
@@ -16,7 +16,10 @@
* In the debug case, 1 means unlocked, 0 means locked. (the values
* are inverted, to catch initialization bugs)
*
- * No atomicity anywhere, we are on UP.
+ * No atomicity anywhere, we are on UP. However, we still need
+ * the compiler barriers, because we do not want the compiler to
+ * move potentially faulting instructions (notably user accesses)
+ * into the locked sequence, resulting in non-atomic execution.
*/
#ifdef CONFIG_DEBUG_SPINLOCK
@@ -25,6 +28,7 @@
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
lock->slock = 0;
+ barrier();
}
static inline void
@@ -32,6 +36,7 @@ arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
{
local_irq_save(flags);
lock->slock = 0;
+ barrier();
}
static inline int arch_spin_trylock(arch_spinlock_t *lock)
@@ -39,32 +44,34 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
char oldval = lock->slock;
lock->slock = 0;
+ barrier();
return oldval > 0;
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
+ barrier();
lock->slock = 1;
}
/*
* Read-write spinlocks. No debug version.
*/
-#define arch_read_lock(lock) do { (void)(lock); } while (0)
-#define arch_write_lock(lock) do { (void)(lock); } while (0)
-#define arch_read_trylock(lock) ({ (void)(lock); 1; })
-#define arch_write_trylock(lock) ({ (void)(lock); 1; })
-#define arch_read_unlock(lock) do { (void)(lock); } while (0)
-#define arch_write_unlock(lock) do { (void)(lock); } while (0)
+#define arch_read_lock(lock) do { barrier(); (void)(lock); } while (0)
+#define arch_write_lock(lock) do { barrier(); (void)(lock); } while (0)
+#define arch_read_trylock(lock) ({ barrier(); (void)(lock); 1; })
+#define arch_write_trylock(lock) ({ barrier(); (void)(lock); 1; })
+#define arch_read_unlock(lock) do { barrier(); (void)(lock); } while (0)
+#define arch_write_unlock(lock) do { barrier(); (void)(lock); } while (0)
#else /* DEBUG_SPINLOCK */
#define arch_spin_is_locked(lock) ((void)(lock), 0)
/* for sched.c and kernel_lock.c: */
-# define arch_spin_lock(lock) do { (void)(lock); } while (0)
-# define arch_spin_lock_flags(lock, flags) do { (void)(lock); } while (0)
-# define arch_spin_unlock(lock) do { (void)(lock); } while (0)
-# define arch_spin_trylock(lock) ({ (void)(lock); 1; })
+# define arch_spin_lock(lock) do { barrier(); (void)(lock); } while (0)
+# define arch_spin_lock_flags(lock, flags) do { barrier(); (void)(lock); } while (0)
+# define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
+# define arch_spin_trylock(lock) ({ barrier(); (void)(lock); 1; })
#endif /* DEBUG_SPINLOCK */
#define arch_spin_is_contended(lock) (((void)(lock), 0))