i386: improve and correct inline asm memory constraints
Use "+m" rather than a combination of "=m" and "m" for improved clarity
and consistency.
This also fixes some inlines that incorrectly didn't tell the compiler
that they read the old value at all, potentially causing the compiler to
generate bogus code. It appear that all of those potential bugs were
hidden by the use of extra "volatile" specifiers on the data structures
in question, though.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-i386/spinlock.h b/include/asm-i386/spinlock.h
index 87c40f8..d816c62 100644
--- a/include/asm-i386/spinlock.h
+++ b/include/asm-i386/spinlock.h
@@ -65,7 +65,7 @@
alternative_smp(
__raw_spin_lock_string,
__raw_spin_lock_string_up,
- "=m" (lock->slock) : : "memory");
+ "+m" (lock->slock) : : "memory");
}
/*
@@ -79,7 +79,7 @@
alternative_smp(
__raw_spin_lock_string_flags,
__raw_spin_lock_string_up,
- "=m" (lock->slock) : "r" (flags) : "memory");
+ "+m" (lock->slock) : "r" (flags) : "memory");
}
#endif
@@ -88,7 +88,7 @@
char oldval;
__asm__ __volatile__(
"xchgb %b0,%1"
- :"=q" (oldval), "=m" (lock->slock)
+ :"=q" (oldval), "+m" (lock->slock)
:"0" (0) : "memory");
return oldval > 0;
}
@@ -104,7 +104,7 @@
#define __raw_spin_unlock_string \
"movb $1,%0" \
- :"=m" (lock->slock) : : "memory"
+ :"+m" (lock->slock) : : "memory"
static inline void __raw_spin_unlock(raw_spinlock_t *lock)
@@ -118,7 +118,7 @@
#define __raw_spin_unlock_string \
"xchgb %b0, %1" \
- :"=q" (oldval), "=m" (lock->slock) \
+ :"=q" (oldval), "+m" (lock->slock) \
:"0" (oldval) : "memory"
static inline void __raw_spin_unlock(raw_spinlock_t *lock)
@@ -199,13 +199,13 @@
static inline void __raw_read_unlock(raw_rwlock_t *rw)
{
- asm volatile(LOCK_PREFIX "incl %0" :"=m" (rw->lock) : : "memory");
+ asm volatile(LOCK_PREFIX "incl %0" :"+m" (rw->lock) : : "memory");
}
static inline void __raw_write_unlock(raw_rwlock_t *rw)
{
asm volatile(LOCK_PREFIX "addl $" RW_LOCK_BIAS_STR ", %0"
- : "=m" (rw->lock) : : "memory");
+ : "+m" (rw->lock) : : "memory");
}
#endif /* __ASM_SPINLOCK_H */