Re: [dpdk-dev] [PATCH] lib/power: fix governor storage to trim newlines

["Hunt, David" <david.hunt@intel.com>]

Hi Anatoly,

On 29/3/2019 4:25 PM, Burakov, Anatoly wrote:
> On 29-Mar-19 4:11 PM, David Hunt wrote:
>> Currently the Power Libray stores the governor name with an embedded
>> newline read from the scaling_governor sysfs file. This patch strips
>> it out.
>>
>> Fixes: 445c6528b55f ("power: common interface for guest and host")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: David Hunt <david.hunt@intel.com>
>> ---
>>   lib/librte_power/power_acpi_cpufreq.c   | 4 ++++
>>   lib/librte_power/power_pstate_cpufreq.c | 4 ++++
>>   2 files changed, 8 insertions(+)
>>
>> diff --git a/lib/librte_power/power_acpi_cpufreq.c 
>> b/lib/librte_power/power_acpi_cpufreq.c
>> index 45412f0b9..c2febdf06 100644
>> --- a/lib/librte_power/power_acpi_cpufreq.c
>> +++ b/lib/librte_power/power_acpi_cpufreq.c
>> @@ -147,6 +147,10 @@ power_set_governor_userspace(struct 
>> rte_power_info *pi)
>>         s = fgets(buf, sizeof(buf), f);
>>       FOPS_OR_NULL_GOTO(s, out);
>> +    buf[BUFSIZ-1] = '\0';
>> +    if (strlen(buf))
>> +        /* Strip off terminating '\n' */
>> +        strtok(buf, "\n");
>
> I have a feeling that either strlen or strtok here is unnecessary.
>
> If it's always terminating - you can just use strlen return value and 
> overwrite the '\n' without going over the string the second time - you 
> know where the string ends!
>
> You have already written null-terminator to the end of the buffer, so 
> it can't overflow on strtok, so you don't really need strlen either, 
> because the string will either:
>
> 1) be empty (in which case strtok does nothing)
> 2) contain text + newline (in which case you cut off the newline and 
> leave the text - no need for strlen), or
> 3) contain just a newline (which would make it empty after strtok)
>
> Did you mean to only cut off the newline off the strings that have 
> stuff other than newline? That would be the only case where using 
> strlen would make sense - in which case, not only the check is wrong, 
> but you could also replace it with a simple 'if (buf[0] != '\n')' 
> check instead of strlen.
>

So just the strtok() then, without anything else (apart from the 
comment) . Sure! :)

Thanks,
Dave.