linux-kernel - Re: [PATCH] selftests: arm64: Fix redundancy of a testcase

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Message-ID: <9710a691-1c94-4f0b-b320-9fc78ee15ae8@arm.com>
Date: Wed, 5 Jun 2024 17:56:25 +0530
From: Dev Jain <dev.jain@....com>
To: Mark Brown <broonie@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
 will@...nel.org, shuah@...nel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, suzuki.poulose@....com,
 Anshuman.Khandual@....com
Subject: Re: [PATCH] selftests: arm64: Fix redundancy of a testcase


On 6/5/24 17:30, Mark Brown wrote:
> On Wed, Jun 05, 2024 at 05:24:48PM +0530, Dev Jain wrote:
>> Currently, we are writing the same value as we read, into the TLS
>> register; hence, we cannot confirm updation of the register, making the
>> testcase "verify_tpidr_one" redundant. Fix this; while at it, do a style
>> change.
> Please don't combine unrelated changes into a single patch.


I shall take care of that in the future.

>
>>   	/* ...write a new value.. */
>>   	write_iov.iov_len = sizeof(uint64_t);
>> -	write_val[0] = read_val[0]++;
>> +	write_val[0] = read_val[0] + 1;
>>   	ret = ptrace(PTRACE_SETREGSET, child, NT_ARM_TLS, &write_iov);
>>   	ksft_test_result(ret == 0, "write_tpidr_one\n");
> This is a good fix:
>
> Reviewed-by: Mark Brown <broonie@...nel.org>


Thanks!

>
>> @@ -108,7 +108,7 @@ static void test_tpidr(pid_t child)
>>   		/* Writing only TPIDR... */
>>   		write_iov.iov_len = sizeof(uint64_t);
>>   		memcpy(write_val, read_val, sizeof(read_val));
>> -		write_val[0] += 1;
>> +		++write_val[0];
> I'm less convinced that this is a good style change.


Well, what I have seen usually is, when we add 1, we

use prefix/postfix increment, and do a "+=" when it

is not 1. But, I get your point: such style may confuse

people into thinking that we are doing an index/pointer

increment, since that is the usual usecase for this.