Re: i386 and x86-64 bitops function prototypes differ
From: Stephane Eranian
Date: Thu Feb 01 2007 - 04:16:45 EST
Hello,
On Fri, Jan 26, 2007 at 09:49:54AM -0800, H. Peter Anvin wrote:
> >
> >I ran into compiler warnings with the perfmon code when I tried
> >using test() and __set_bit() on i386.
> >
> >For some reason, the i386 bitops functions use unsigned long * for
> >the address whereas x86-64/ia64 use void *.
> >
> >I do not quite understand why such difference?
> >Is this just for historical reasons?
> >
> >Thanks.
> >
>
> Arguably void * is the right thing for a littleendian architecture. For
> bigendian architectures it unfortunately matters what the chunk size is,
> regardless of if the chunks are numbered in bigendian (reverse) or
> littleendian (forward) order.
>
I agree with you, but i386 is definitively little endian, so here is a patch
against 2.6.20-rc6-mm3 to make x86-64 and i386 have the same prototypes for
bit manipulation routines.
changelog:
- change all bit manipulation inline routine to use void * as their
address argument instead of unsigned long *. Match x86-64
signed-off-by: stephane eranian <eranian@xxxxxxxxxx>
--- linux-2.6.20-rc6-mm3.orig/include/asm-i386/bitops.h 2007-01-31 09:24:21.000000000 -0800
+++ linux-2.6.20-rc6-mm3.base/include/asm-i386/bitops.h 2007-01-31 09:31:46.000000000 -0800
@@ -33,7 +33,7 @@
* Note that @nr may be almost arbitrarily large; this function is not
* restricted to acting on a single-word quantity.
*/
-static inline void set_bit(int nr, volatile unsigned long * addr)
+static inline void set_bit(int nr, volatile void * addr)
{
__asm__ __volatile__( LOCK_PREFIX
"btsl %1,%0"
@@ -50,7 +50,7 @@ static inline void set_bit(int nr, volat
* If it's called on the same region of memory simultaneously, the effect
* may be that only one operation succeeds.
*/
-static inline void __set_bit(int nr, volatile unsigned long * addr)
+static inline void __set_bit(int nr, volatile void * addr)
{
__asm__(
"btsl %1,%0"
@@ -68,7 +68,7 @@ static inline void __set_bit(int nr, vol
* you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
* in order to ensure changes are visible on other processors.
*/
-static inline void clear_bit(int nr, volatile unsigned long * addr)
+static inline void clear_bit(int nr, volatile void * addr)
{
__asm__ __volatile__( LOCK_PREFIX
"btrl %1,%0"
@@ -76,7 +76,7 @@ static inline void clear_bit(int nr, vol
:"Ir" (nr));
}
-static inline void __clear_bit(int nr, volatile unsigned long * addr)
+static inline void __clear_bit(int nr, volatile void * addr)
{
__asm__ __volatile__(
"btrl %1,%0"
@@ -95,7 +95,7 @@ static inline void __clear_bit(int nr, v
* If it's called on the same region of memory simultaneously, the effect
* may be that only one operation succeeds.
*/
-static inline void __change_bit(int nr, volatile unsigned long * addr)
+static inline void __change_bit(int nr, volatile void * addr)
{
__asm__ __volatile__(
"btcl %1,%0"
@@ -113,7 +113,7 @@ static inline void __change_bit(int nr,
* Note that @nr may be almost arbitrarily large; this function is not
* restricted to acting on a single-word quantity.
*/
-static inline void change_bit(int nr, volatile unsigned long * addr)
+static inline void change_bit(int nr, volatile void * addr)
{
__asm__ __volatile__( LOCK_PREFIX
"btcl %1,%0"
@@ -130,7 +130,7 @@ static inline void change_bit(int nr, vo
* It may be reordered on other architectures than x86.
* It also implies a memory barrier.
*/
-static inline int test_and_set_bit(int nr, volatile unsigned long * addr)
+static inline int test_and_set_bit(int nr, volatile void * addr)
{
int oldbit;
@@ -150,7 +150,7 @@ static inline int test_and_set_bit(int n
* If two examples of this operation race, one can appear to succeed
* but actually fail. You must protect multiple accesses with a lock.
*/
-static inline int __test_and_set_bit(int nr, volatile unsigned long * addr)
+static inline int __test_and_set_bit(int nr, volatile void * addr)
{
int oldbit;
@@ -170,7 +170,7 @@ static inline int __test_and_set_bit(int
* It can be reorderdered on other architectures other than x86.
* It also implies a memory barrier.
*/
-static inline int test_and_clear_bit(int nr, volatile unsigned long * addr)
+static inline int test_and_clear_bit(int nr, volatile void * addr)
{
int oldbit;
@@ -190,7 +190,7 @@ static inline int test_and_clear_bit(int
* If two examples of this operation race, one can appear to succeed
* but actually fail. You must protect multiple accesses with a lock.
*/
-static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr)
+static inline int __test_and_clear_bit(int nr, volatile void *addr)
{
int oldbit;
@@ -202,7 +202,7 @@ static inline int __test_and_clear_bit(i
}
/* WARNING: non atomic and it can be reordered! */
-static inline int __test_and_change_bit(int nr, volatile unsigned long *addr)
+static inline int __test_and_change_bit(int nr, volatile void *addr)
{
int oldbit;
@@ -221,7 +221,7 @@ static inline int __test_and_change_bit(
* This operation is atomic and cannot be reordered.
* It also implies a memory barrier.
*/
-static inline int test_and_change_bit(int nr, volatile unsigned long* addr)
+static inline int test_and_change_bit(int nr, volatile void * addr)
{
int oldbit;
@@ -241,12 +241,12 @@ static inline int test_and_change_bit(in
static int test_bit(int nr, const volatile void * addr);
#endif
-static __always_inline int constant_test_bit(int nr, const volatile unsigned long *addr)
+static __always_inline int constant_test_bit(int nr, const volatile void * addr)
{
- return ((1UL << (nr & 31)) & (addr[nr >> 5])) != 0;
+ return ((1UL << (nr & 31)) & (((const volatile unsigned int *) addr)[nr >> 5])) != 0;
}
-static inline int variable_test_bit(int nr, const volatile unsigned long * addr)
+static inline int variable_test_bit(int nr, const volatile void * addr)
{
int oldbit;
-
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