Subject: Re: linux-next: build warning after merge of the tip tree

From: Thomas Gleixner <[email-masked]>
Date: Tue, 14 Apr 2020 10:42:36 +0200

Stephen,

Stephen Rothwell <[email-masked]> writes:
> On Thu, 02 Apr 2020 00:39:55 +0200 Thomas Gleixner <[email-masked]> wrote:
>> and the below proves it:
>> 
>> diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
>> index e133da303a98..a9151884bc85 100644
>> --- a/arch/arm/include/asm/futex.h
>> +++ b/arch/arm/include/asm/futex.h
>> @@ -165,8 +165,13 @@ arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
>>  	preempt_enable();
>>  #endif
>>  
>> -	if (!ret)
>> -		*oval = oldval;
>> +	/*
>> +	 * Store unconditionally. If ret != 0 the extra store is the least
>> +	 * of the worries but GCC cannot figure out that __futex_atomic_op()
>> +	 * is either setting ret to -EFAULT or storing the old value in
>> +	 * oldval which results in a uninitialized warning at the call site.
>> +	 */
>> +	*oval = oldval;
>>  
>>  	return ret;
>>  }
>> 
>> I think that's the right thing to do anyway. The conditional is pointless.
>
> Thanks for the analysis.
>
> I am still getting this warning, now from Linus' tree builds.

Yeah. Just noticed that both of us failed to CC the arm folks. :(

Let me send out a proper patch.

Thanks,

        tglx