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>

1 files changed, 17 insertions, 18 deletions

diff --git a/include/asm-i386/rwsem.h b/include/asm-i386/rwsem.h
index 2f07601562e..43113f5608e 100644
--- a/include/asm-i386/rwsem.h
+++ b/include/asm-i386/rwsem.h
@@ -111,8 +111,8 @@ LOCK_PREFIX	"  incl      (%%eax)\n\t" /* adds 0x00000001, returns the old value
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending down_read\n\t"
-		: "=m"(sem->count)
-		: "a"(sem), "m"(sem->count)
+		: "+m" (sem->count)
+		: "a" (sem)
 		: "memory", "cc");
 }
 
@@ -133,8 +133,8 @@ LOCK_PREFIX	"  cmpxchgl  %2,%0\n\t"
 		"  jnz	     1b\n\t"
 		"2:\n\t"
 		"# ending __down_read_trylock\n\t"
-		: "+m"(sem->count), "=&a"(result), "=&r"(tmp)
-		: "i"(RWSEM_ACTIVE_READ_BIAS)
+		: "+m" (sem->count), "=&a" (result), "=&r" (tmp)
+		: "i" (RWSEM_ACTIVE_READ_BIAS)
 		: "memory", "cc");
 	return result>=0 ? 1 : 0;
 }
@@ -161,8 +161,8 @@ LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending down_write"
-		: "=m"(sem->count), "=d"(tmp)
-		: "a"(sem), "1"(tmp), "m"(sem->count)
+		: "+m" (sem->count), "=d" (tmp)
+		: "a" (sem), "1" (tmp)
 		: "memory", "cc");
 }
 
@@ -205,8 +205,8 @@ LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtracts 1, returns the old valu
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending __up_read\n"
-		: "=m"(sem->count), "=d"(tmp)
-		: "a"(sem), "1"(tmp), "m"(sem->count)
+		: "+m" (sem->count), "=d" (tmp)
+		: "a" (sem), "1" (tmp)
 		: "memory", "cc");
 }
 
@@ -231,8 +231,8 @@ LOCK_PREFIX	"  xaddl     %%edx,(%%eax)\n\t" /* tries to transition 0xffff0001 ->
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending __up_write\n"
-		: "=m"(sem->count)
-		: "a"(sem), "i"(-RWSEM_ACTIVE_WRITE_BIAS), "m"(sem->count)
+		: "+m" (sem->count)
+		: "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS)
 		: "memory", "cc", "edx");
 }
 
@@ -256,8 +256,8 @@ LOCK_PREFIX	"  addl      %2,(%%eax)\n\t" /* transitions 0xZZZZ0001 -> 0xYYYY0001
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending __downgrade_write\n"
-		: "=m"(sem->count)
-		: "a"(sem), "i"(-RWSEM_WAITING_BIAS), "m"(sem->count)
+		: "+m" (sem->count)
+		: "a" (sem), "i" (-RWSEM_WAITING_BIAS)
 		: "memory", "cc");
 }
 
@@ -268,8 +268,8 @@ static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
 {
 	__asm__ __volatile__(
 LOCK_PREFIX	"addl %1,%0"
-		: "=m"(sem->count)
-		: "ir"(delta), "m"(sem->count));
+		: "+m" (sem->count)
+		: "ir" (delta));
 }
 
 /*
@@ -280,10 +280,9 @@ static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
 	int tmp = delta;
 
 	__asm__ __volatile__(
-LOCK_PREFIX	"xadd %0,(%2)"
-		: "+r"(tmp), "=m"(sem->count)
-		: "r"(sem), "m"(sem->count)
-		: "memory");
+LOCK_PREFIX	"xadd %0,%1"
+		: "+r" (tmp), "+m" (sem->count)
+		: : "memory");
 
 	return tmp+delta;
 }