linux-kernel - Re: [PATCH V3 02/10] ras: acpi/apei: cper: generic error data entry v3 per ACPI 6.1

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Message-ID: <dfdf5c92-52a7-a641-42aa-c230f5ebc0b2@codeaurora.org>
Date:   Wed, 12 Oct 2016 16:18:58 -0600
From:   "Baicar, Tyler" <tbaicar@...eaurora.org>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     christoffer.dall@...aro.org, marc.zyngier@....com,
        pbonzini@...hat.com, rkrcmar@...hat.com, catalin.marinas@....com,
        will.deacon@....com, rjw@...ysocki.net, lenb@...nel.org,
        matt@...eblueprint.co.uk, robert.moore@...el.com,
        lv.zheng@...el.com, mark.rutland@....com, james.morse@....com,
        akpm@...ux-foundation.org, sandeepa.s.prabhu@...il.com,
        shijie.huang@....com, paul.gortmaker@...driver.com,
        tomasz.nowicki@...aro.org, fu.wei@...aro.org, rostedt@...dmis.org,
        bristot@...hat.com, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, Dkvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-efi@...r.kernel.org, devel@...ica.org,
        "Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>,
        Richard Ruigrok <rruigrok@...eaurora.org>,
        Naveen Kaje <nkaje@...eaurora.org>
Subject: Re: [PATCH V3 02/10] ras: acpi/apei: cper: generic error data entry
 v3 per ACPI 6.1

Hello Russell,

Thank you for the feedback! Responses below


On 10/11/2016 12:52 PM, Russell King - ARM Linux wrote:
> On Fri, Oct 07, 2016 at 03:31:14PM -0600, Tyler Baicar wrote:
>> +static void cper_estatus_print_section_v300(const char *pfx,
>> +	const struct acpi_hest_generic_data_v300 *gdata)
>> +{
>> +	__u8 hour, min, sec, day, mon, year, century, *timestamp;
>> +
>> +	if (gdata->validation_bits & ACPI_HEST_GEN_VALID_TIMESTAMP) {
>> +		timestamp = (__u8 *)&(gdata->time_stamp);
>> +		memcpy(&sec, timestamp, 1);
>> +		memcpy(&min, timestamp + 1, 1);
>> +		memcpy(&hour, timestamp + 2, 1);
>> +		memcpy(&day, timestamp + 4, 1);
>> +		memcpy(&mon, timestamp + 5, 1);
>> +		memcpy(&year, timestamp + 6, 1);
>> +		memcpy(&century, timestamp + 7, 1);
> This is utterly silly.  Why are you using memcpy() to access individual
> bytes of a u8 pointer?  What's wrong with:
>
> 		sec = timestamp[0];
> 		min = timestamp[1];
> 		hour = timestamp[2];
> 		day = timestamp[4];
> 		mon = timestamp[5];
> 		year = timestamp[6];
> 		century = timestamp[7];
>
> or even do the conversion here:
>
> 		sec = bcd2bin(timestamp[0]);
> ... etc ...
Yes, that will be a lot cleaner especially with moving the conversion here.
>
>> +		printk("%stime: ", pfx);
>> +		printk("%7s", 0x01 & *(timestamp + 3) ? "precise" : "");
>> +		printk(" %02d:%02d:%02d %02d%02d-%02d-%02d\n",
>> +			bcd2bin(hour), bcd2bin(min), bcd2bin(sec),
>> +			bcd2bin(century), bcd2bin(year), bcd2bin(mon),
>> +			bcd2bin(day));
>> +	}
> It's also a good idea to (as much as possible) keep to single printk()
> statements - which makes the emission of the string more atomic wrt
> other CPUs and contexts.  So, this should probably become (with the
> conversion being done at the assignment of sec etc):
>
> 		printk("%stime: %7s %02d:%02d:%02d %02d%02d-%02d-%02d\n",
> 			pfx, 0x01 & timestamp[3] ? "precise" : "",
> 			hour, min, sec, century, year, mon, day);
>
> which, IMHO, looks a lot nicer and doesn't risk some other printk()
> getting between each individual part of the line.
I will make this change in the next version. This printk does look a lot 
nicer and avoids other prints from getting in the middle (I actually 
just saw that happen in testing a couple days ago)
>> +}
>> +
>>   static void cper_estatus_print_section(
>> -	const char *pfx, const struct acpi_hest_generic_data *gdata, int sec_no)
>> +	const char *pfx, struct acpi_hest_generic_data *gdata, int sec_no)
>>   {
>>   	uuid_le *sec_type = (uuid_le *)gdata->section_type;
>>   	__u16 severity;
>>   	char newpfx[64];
>>   
>> +	if ((gdata->revision >> 8) >= 0x03)
>> +		cper_estatus_print_section_v300(pfx,
>> +			(const struct acpi_hest_generic_data_v300 *)gdata);
>> +
>>   	severity = gdata->error_severity;
>>   	printk("%s""Error %d, type: %s\n", pfx, sec_no,
>>   	       cper_severity_str(severity));
> Not sure why you have the "" here - %sError works just as well and the
> "" is just obfuscation - the compiler will eliminate the double-double
> quote and merge the strings anyway.
>
I will remove the "" in the next version.

Thanks,
Tyler

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