linux-kernel - Re: [PATCH] x86: remove unused atomic_inc

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Date:   Wed, 22 Mar 2017 18:46:30 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] x86: remove unused atomic_inc_short()

On Wed, Mar 22, 2017 at 5:13 PM, Andrey Ryabinin
<aryabinin@...tuozzo.com> wrote:
>
>
> On 03/22/2017 05:10 PM, Dmitry Vyukov wrote:
>> It is completely unused and implemented only on x86.
>> Remove it.
>>
>> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
>> Suggested-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
>
> Not me, it was Mark Rutland <mark.rutland@....com>

Mailed v2 with proper attribution.


>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: linux-kernel@...r.kernel.org
>> Cc: x86@...nel.org
>>
>> ---
>>
>> Andrew, I think it needs to go into mm as
>> the atomic-instrumented.h patch is in mm.
>> ---
>>  arch/tile/lib/atomic_asm_32.S             |  3 +--
>>  arch/x86/include/asm/atomic.h             | 13 -------------
>>  include/asm-generic/atomic-instrumented.h |  6 ------
>>  3 files changed, 1 insertion(+), 21 deletions(-)
>>
>> diff --git a/arch/tile/lib/atomic_asm_32.S b/arch/tile/lib/atomic_asm_32.S
>> index 1a70e6c0f259..94709ab41ed8 100644
>> --- a/arch/tile/lib/atomic_asm_32.S
>> +++ b/arch/tile/lib/atomic_asm_32.S
>> @@ -24,8 +24,7 @@
>>   * has an opportunity to return -EFAULT to the user if needed.
>>   * The 64-bit routines just return a "long long" with the value,
>>   * since they are only used from kernel space and don't expect to fault.
>> - * Support for 16-bit ops is included in the framework but we don't provide
>> - * any (x86_64 has an atomic_inc_short(), so we might want to some day).
>> + * Support for 16-bit ops is included in the framework but we don't provide any.
>>   *
>>   * Note that the caller is advised to issue a suitable L1 or L2
>>   * prefetch on the address being manipulated to avoid extra stalls.
>> diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
>> index 0cde164f058a..9ff8738103eb 100644
>> --- a/arch/x86/include/asm/atomic.h
>> +++ b/arch/x86/include/asm/atomic.h
>> @@ -237,19 +237,6 @@ ATOMIC_OPS(xor, ^)
>>
>>  int __arch_atomic_add_unless(atomic_t *v, int a, int u);
>>
>> -/**
>> - * arch_atomic_inc_short - increment of a short integer
>> - * @v: pointer to type int
>> - *
>> - * Atomically adds 1 to @v
>> - * Returns the new value of @u
>> - */
>> -static __always_inline short int arch_atomic_inc_short(short int *v)
>> -{
>> -     asm(LOCK_PREFIX "addw $1, %0" : "+m" (*v));
>> -     return *v;
>> -}
>> -
>>  #ifdef CONFIG_X86_32
>>  # include <asm/atomic64_32.h>
>>  #else
>> diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h
>> index 951bcd083925..70742da13087 100644
>> --- a/include/asm-generic/atomic-instrumented.h
>> +++ b/include/asm-generic/atomic-instrumented.h
>> @@ -78,12 +78,6 @@ static __always_inline bool atomic64_add_unless(atomic64_t *v, long long a,
>>       return arch_atomic64_add_unless(v, a, u);
>>  }
>>
>> -static __always_inline short int atomic_inc_short(short int *v)
>> -{
>> -     kasan_check_write(v, sizeof(*v));
>> -     return arch_atomic_inc_short(v);
>> -}
>> -
>>  #define __INSTR_VOID1(op, sz)                                                \
>>  static __always_inline void atomic##sz##_##op(atomic##sz##_t *v)     \
>>  {                                                                    \
>>