[PATCH] locking/atomic: atomic64: remove unusable atomics

[PATCH] locking/atomic: atomic64: remove unusable atomics

[Mark Rutland]

The generic atomic64 implementation provides:

* atomic64_and_return()
* atomic64_or_return()
* atomic64_xor_return()

... but none of these exist in the standard atomic64 API as described by
scripts/atomic/atomics.tbl, and none of these have prototypes exposed by
<asm-generic/atomic64.h>.

The lkp kernel test robot noted this results in warnings when building with
W=1:

  lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_and_return' [-Wmissing-prototypes]

  lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_or_return' [-Wmissing-prototypes]

  lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_xor_return' [-Wmissing-prototypes]

This appears to have been a thinko in commit:

  28aa2bda2211f432 ("locking/atomic: Implement atomic{,64,_long}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()")

... where we grouped add/sub separately from and/ox/xor, so that we could avoid
implementing _return forms for the latter group, but forgot to remove
ATOMIC64_OP_RETURN() for that group.

This doesn't cause any functional problem, but it's pointless to build code
which cannot be used. Remove the unusable code. This does not affect add/sub,
for which _return forms will still be built.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/202111120712.RtQHZohY-lkp@intel.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
---
 lib/atomic64.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/lib/atomic64.c b/lib/atomic64.c
index 3df653994177..caf895789a1e 100644
--- a/lib/atomic64.c
+++ b/lib/atomic64.c
@@ -118,7 +118,6 @@ ATOMIC64_OPS(sub, -=)
 #undef ATOMIC64_OPS
 #define ATOMIC64_OPS(op, c_op)						\
 	ATOMIC64_OP(op, c_op)						\
-	ATOMIC64_OP_RETURN(op, c_op)					\
 	ATOMIC64_FETCH_OP(op, c_op)
 
 ATOMIC64_OPS(and, &=)
@@ -127,7 +126,6 @@ ATOMIC64_OPS(xor, ^=)
 
 #undef ATOMIC64_OPS
 #undef ATOMIC64_FETCH_OP
-#undef ATOMIC64_OP_RETURN
 #undef ATOMIC64_OP
 
 s64 generic_atomic64_dec_if_positive(atomic64_t *v)
-- 
2.30.2

Re: [PATCH] locking/atomic: atomic64: remove unusable atomics

[Boqun Feng]

On Fri, Nov 26, 2021 at 11:59:23AM +0000, Mark Rutland wrote:
> The generic atomic64 implementation provides:
> 
> * atomic64_and_return()
> * atomic64_or_return()
> * atomic64_xor_return()
> 
> ... but none of these exist in the standard atomic64 API as described by
> scripts/atomic/atomics.tbl, and none of these have prototypes exposed by
> <asm-generic/atomic64.h>.
> 
> The lkp kernel test robot noted this results in warnings when building with
> W=1:
> 
>   lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_and_return' [-Wmissing-prototypes]
> 
>   lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_or_return' [-Wmissing-prototypes]
> 
>   lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_xor_return' [-Wmissing-prototypes]
> 
> This appears to have been a thinko in commit:
> 
>   28aa2bda2211f432 ("locking/atomic: Implement atomic{,64,_long}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()")
> 
> ... where we grouped add/sub separately from and/ox/xor, so that we could avoid
> implementing _return forms for the latter group, but forgot to remove
> ATOMIC64_OP_RETURN() for that group.
> 
> This doesn't cause any functional problem, but it's pointless to build code
> which cannot be used. Remove the unusable code. This does not affect add/sub,
> for which _return forms will still be built.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/r/202111120712.RtQHZohY-lkp@intel.com
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

FWIW

Acked-by: Boqun Feng <boqun.feng@gmail.com>

Regards,
Boqun

> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>  lib/atomic64.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/lib/atomic64.c b/lib/atomic64.c
> index 3df653994177..caf895789a1e 100644
> --- a/lib/atomic64.c
> +++ b/lib/atomic64.c
> @@ -118,7 +118,6 @@ ATOMIC64_OPS(sub, -=)
>  #undef ATOMIC64_OPS
>  #define ATOMIC64_OPS(op, c_op)						\
>  	ATOMIC64_OP(op, c_op)						\
> -	ATOMIC64_OP_RETURN(op, c_op)					\
>  	ATOMIC64_FETCH_OP(op, c_op)
>  
>  ATOMIC64_OPS(and, &=)
> @@ -127,7 +126,6 @@ ATOMIC64_OPS(xor, ^=)
>  
>  #undef ATOMIC64_OPS
>  #undef ATOMIC64_FETCH_OP
> -#undef ATOMIC64_OP_RETURN
>  #undef ATOMIC64_OP
>  
>  s64 generic_atomic64_dec_if_positive(atomic64_t *v)
> -- 
> 2.30.2
> 

Re: [PATCH] locking/atomic: atomic64: remove unusable atomics

[Mark Rutland]

Peter, did you have any thoughts on this, or would you be happy to pick it as a
cleanup?

If there's anything on your queue that I can help to get out of the way, please
let me know!

Thanks,
Mark.

On Fri, Nov 26, 2021 at 11:59:23AM +0000, Mark Rutland wrote:
> The generic atomic64 implementation provides:
> 
> * atomic64_and_return()
> * atomic64_or_return()
> * atomic64_xor_return()
> 
> ... but none of these exist in the standard atomic64 API as described by
> scripts/atomic/atomics.tbl, and none of these have prototypes exposed by
> <asm-generic/atomic64.h>.
> 
> The lkp kernel test robot noted this results in warnings when building with
> W=1:
> 
>   lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_and_return' [-Wmissing-prototypes]
> 
>   lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_or_return' [-Wmissing-prototypes]
> 
>   lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_xor_return' [-Wmissing-prototypes]
> 
> This appears to have been a thinko in commit:
> 
>   28aa2bda2211f432 ("locking/atomic: Implement atomic{,64,_long}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()")
> 
> ... where we grouped add/sub separately from and/ox/xor, so that we could avoid
> implementing _return forms for the latter group, but forgot to remove
> ATOMIC64_OP_RETURN() for that group.
> 
> This doesn't cause any functional problem, but it's pointless to build code
> which cannot be used. Remove the unusable code. This does not affect add/sub,
> for which _return forms will still be built.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/r/202111120712.RtQHZohY-lkp@intel.com
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>  lib/atomic64.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/lib/atomic64.c b/lib/atomic64.c
> index 3df653994177..caf895789a1e 100644
> --- a/lib/atomic64.c
> +++ b/lib/atomic64.c
> @@ -118,7 +118,6 @@ ATOMIC64_OPS(sub, -=)
>  #undef ATOMIC64_OPS
>  #define ATOMIC64_OPS(op, c_op)						\
>  	ATOMIC64_OP(op, c_op)						\
> -	ATOMIC64_OP_RETURN(op, c_op)					\
>  	ATOMIC64_FETCH_OP(op, c_op)
>  
>  ATOMIC64_OPS(and, &=)
> @@ -127,7 +126,6 @@ ATOMIC64_OPS(xor, ^=)
>  
>  #undef ATOMIC64_OPS
>  #undef ATOMIC64_FETCH_OP
> -#undef ATOMIC64_OP_RETURN
>  #undef ATOMIC64_OP
>  
>  s64 generic_atomic64_dec_if_positive(atomic64_t *v)
> -- 
> 2.30.2
> 

Re: [PATCH] locking/atomic: atomic64: remove unusable atomics

[Peter Zijlstra]

On Wed, Dec 08, 2021 at 06:20:47PM +0000, Mark Rutland wrote:
> Peter, did you have any thoughts on this, or would you be happy to pick it as a
> cleanup?
> 
> If there's anything on your queue that I can help to get out of the way, please
> let me know!
> 

I think it's good, it just got lost in this trainwreck of an inbox. I'll
try not to loose it again :-)

[tip: locking/core] locking/atomic: atomic64: Remove unusable atomic ops

[tip-bot2 for Mark Rutland]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     5fb6e8cf53b005d287d4c2d137a415ff7d025a81
Gitweb:        https://git.kernel.org/tip/5fb6e8cf53b005d287d4c2d137a415ff7d025a81
Author:        Mark Rutland <mark.rutland@arm.com>
AuthorDate:    Fri, 26 Nov 2021 11:59:23 
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 13 Dec 2021 10:56:09 +01:00

locking/atomic: atomic64: Remove unusable atomic ops

The generic atomic64 implementation provides:

* atomic64_and_return()
* atomic64_or_return()
* atomic64_xor_return()

... but none of these exist in the standard atomic64 API as described by
scripts/atomic/atomics.tbl, and none of these have prototypes exposed by
<asm-generic/atomic64.h>.

The lkp kernel test robot noted this results in warnings when building with
W=1:

  lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_and_return' [-Wmissing-prototypes]

  lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_or_return' [-Wmissing-prototypes]

  lib/atomic64.c:82:5: warning: no previous prototype for 'generic_atomic64_xor_return' [-Wmissing-prototypes]

This appears to have been a thinko in commit:

  28aa2bda2211f432 ("locking/atomic: Implement atomic{,64,_long}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()")

... where we grouped add/sub separately from and/ox/xor, so that we could avoid
implementing _return forms for the latter group, but forgot to remove
ATOMIC64_OP_RETURN() for that group.

This doesn't cause any functional problem, but it's pointless to build code
which cannot be used. Remove the unusable code. This does not affect add/sub,
for which _return forms will still be built.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20211126115923.41489-1-mark.rutland@arm.com
---
 lib/atomic64.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/lib/atomic64.c b/lib/atomic64.c
index 3df6539..caf8957 100644
--- a/lib/atomic64.c
+++ b/lib/atomic64.c
@@ -118,7 +118,6 @@ ATOMIC64_OPS(sub, -=)
 #undef ATOMIC64_OPS
 #define ATOMIC64_OPS(op, c_op)						\
 	ATOMIC64_OP(op, c_op)						\
-	ATOMIC64_OP_RETURN(op, c_op)					\
 	ATOMIC64_FETCH_OP(op, c_op)
 
 ATOMIC64_OPS(and, &=)
@@ -127,7 +126,6 @@ ATOMIC64_OPS(xor, ^=)
 
 #undef ATOMIC64_OPS
 #undef ATOMIC64_FETCH_OP
-#undef ATOMIC64_OP_RETURN
 #undef ATOMIC64_OP
 
 s64 generic_atomic64_dec_if_positive(atomic64_t *v)