* i386 and x86-64 bitops function prototypes differ @ 2007-01-26 14:35 Stephane Eranian 2007-01-26 17:49 ` H. Peter Anvin 0 siblings, 1 reply; 6+ messages in thread From: Stephane Eranian @ 2007-01-26 14:35 UTC (permalink / raw) To: linux-kernel; +Cc: Stephane Eranian Hello, 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. -- -Stephane ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: i386 and x86-64 bitops function prototypes differ 2007-01-26 14:35 i386 and x86-64 bitops function prototypes differ Stephane Eranian @ 2007-01-26 17:49 ` H. Peter Anvin 2007-02-01 9:15 ` Stephane Eranian 0 siblings, 1 reply; 6+ messages in thread From: H. Peter Anvin @ 2007-01-26 17:49 UTC (permalink / raw) To: eranian; +Cc: linux-kernel Stephane Eranian wrote: > Hello, > > 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. -hpa ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: i386 and x86-64 bitops function prototypes differ 2007-01-26 17:49 ` H. Peter Anvin @ 2007-02-01 9:15 ` Stephane Eranian 2007-02-01 22:55 ` Andrew Morton 0 siblings, 1 reply; 6+ messages in thread From: Stephane Eranian @ 2007-02-01 9:15 UTC (permalink / raw) To: H. Peter Anvin; +Cc: linux-kernel, akpm, Stephane Eranian 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@hpl.hp.com> --- 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; ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: i386 and x86-64 bitops function prototypes differ 2007-02-01 9:15 ` Stephane Eranian @ 2007-02-01 22:55 ` Andrew Morton 2007-02-01 23:27 ` Stephane Eranian 2007-02-02 7:12 ` Andi Kleen 0 siblings, 2 replies; 6+ messages in thread From: Andrew Morton @ 2007-02-01 22:55 UTC (permalink / raw) To: eranian; +Cc: H. Peter Anvin, linux-kernel, Andi Kleen On Thu, 1 Feb 2007 01:15:55 -0800 Stephane Eranian <eranian@hpl.hp.com> wrote: > 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@hpl.hp.com> > > --- 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) These bitops are only valid on long*'s. Or a least, they require a long-aligned address, and using long* is how we communicate and enforce that. Numerous architectures implement these functions using ulong*. If we make this change, we risk someone doing set_bit() on, say, a char *. That change would compile and run happily on x86 and would then fail on, say, arm or h8/300. So I'd say that x86_64 is wrong, and should be changed to take ulong*. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: i386 and x86-64 bitops function prototypes differ 2007-02-01 22:55 ` Andrew Morton @ 2007-02-01 23:27 ` Stephane Eranian 2007-02-02 7:12 ` Andi Kleen 1 sibling, 0 replies; 6+ messages in thread From: Stephane Eranian @ 2007-02-01 23:27 UTC (permalink / raw) To: Andrew Morton; +Cc: H. Peter Anvin, linux-kernel, Andi Kleen Andrew, On Thu, Feb 01, 2007 at 02:55:25PM -0800, Andrew Morton wrote: > On Thu, 1 Feb 2007 01:15:55 -0800 > Stephane Eranian <eranian@hpl.hp.com> wrote: > > > 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@hpl.hp.com> > > > > --- 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) > > These bitops are only valid on long*'s. Or a least, they require a > long-aligned address, and using long* is how we communicate and enforce > that. > Yes, I realize this now. > Numerous architectures implement these functions using ulong*. If we make > this change, we risk someone doing set_bit() on, say, a char *. That > change would compile and run happily on x86 and would then fail on, say, > arm or h8/300. > > So I'd say that x86_64 is wrong, and should be changed to take ulong*. We need to fix x86-64 and also ia64 it seems. I'll see if I can do that. Thanks. -- -Stephane ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: i386 and x86-64 bitops function prototypes differ 2007-02-01 22:55 ` Andrew Morton 2007-02-01 23:27 ` Stephane Eranian @ 2007-02-02 7:12 ` Andi Kleen 1 sibling, 0 replies; 6+ messages in thread From: Andi Kleen @ 2007-02-02 7:12 UTC (permalink / raw) To: Andrew Morton; +Cc: eranian, H. Peter Anvin, linux-kernel > > So I'd say that x86_64 is wrong, and should be changed to take ulong*. I'm trying to remember why I used void * -- I think there was a reason, but it's lost in the myst of time. Anyways, I suspect changing it now would have quite some fallout on other code, but hopefully limited to arch/x86_64/*. But fixing these up will hopefully not be too hard. -Andi ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2007-02-02 7:21 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2007-01-26 14:35 i386 and x86-64 bitops function prototypes differ Stephane Eranian 2007-01-26 17:49 ` H. Peter Anvin 2007-02-01 9:15 ` Stephane Eranian 2007-02-01 22:55 ` Andrew Morton 2007-02-01 23:27 ` Stephane Eranian 2007-02-02 7:12 ` Andi Kleen
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