linux-kernel - Re: [PATCH] PCI/AER: add pcie TLP header information in the tracepoint

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Date:   Tue, 8 May 2018 09:25:01 -0400
From:   Thomas Tai <thomas.tai@...cle.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alexandru Gagniuc <mr.nuke.me@...il.com>
Subject: Re: [PATCH] PCI/AER: add pcie TLP header information in the
 tracepoint

[ ... ]
>>> --- a/include/ras/ras_event.h
>>> +++ b/include/ras/ras_event.h
>>> @@ -298,30 +298,42 @@ TRACE_EVENT(non_standard_event,
>>>   TRACE_EVENT(aer_event,
>>>   	TP_PROTO(const char *dev_name,
>>>   		 const u32 status,
>>> -		 const u8 severity),
>>> +		 const u8 severity,
>>> +		 const u32 tlp_header_valid,
>>> +		 struct aer_header_log_regs *tlp),
>>>   
>>> -	TP_ARGS(dev_name, status, severity),
>>> +	TP_ARGS(dev_name, status, severity, tlp_header_valid, tlp),
>>>   
>>>   	TP_STRUCT__entry(
>>>   		__string(	dev_name,	dev_name	)
>>>   		__field(	u32,		status		)
>>>   		__field(	u8,		severity	)
>>> +		__field(	u32, 		tlp_header_valid)
> 
> I'm guessing tlp_header_valid is just a boolean. It's after severity
> which is just one byte long. Why not make this one byte as well,
> otherwise you are wasting 3 bytes.

Thanks Steven. Yes boolean is fine.

> 
> 
>>> +		__array(	u32, 		buf, 4		)
>>>   	),
>>>   
>>>   	TP_fast_assign(
>>>   		__assign_str(dev_name, dev_name);
>>>   		__entry->status		= status;
>>>   		__entry->severity	= severity;
>>> +		__entry->tlp_header_valid = tlp_header_valid;
> 
>>> +		__entry->buf[0] = tlp->dw0;
>>> +		__entry->buf[1] = tlp->dw1;
>>> +		__entry->buf[2] = tlp->dw2;
>>> +		__entry->buf[3] = tlp->dw3;
> 
> Should this assignment be dependent on whether or not tlp_header_valid
> is true? Could tlp be pointing to some random memory if it isn't? What
> about:

Good catch! will do so.

> 
> 	if ((__entry->tlp_header_valid = tlp_header_valid)) {
> 		__entry->buf[0] = tlp->dw0;
> 		__entry->buf[1] = tlp->dw1;
> 		__entry->buf[2] = tlp->dw2;
> 		__entry->buf[3] = tlp->dw3;
> 	}
> 
> 
>>>   	),
>>>   
>>> -	TP_printk("%s PCIe Bus Error: severity=%s, %s\n",
>>> +	TP_printk("%s PCIe Bus Error: severity=%s, %s, TLP Header=%s\n",
>>>   		__get_str(dev_name),
>>>   		__entry->severity == AER_CORRECTABLE ? "Corrected" :
>>>   			__entry->severity == AER_FATAL ?
>>>   			"Fatal" : "Uncorrected, non-fatal",
>>>   		__entry->severity == AER_CORRECTABLE ?
>>>   		__print_flags(__entry->status, "|", aer_correctable_errors) :
>>> -		__print_flags(__entry->status, "|", aer_uncorrectable_errors))
>>> +		__print_flags(__entry->status, "|", aer_uncorrectable_errors),
>>> +		__entry->tlp_header_valid ?
>>> +			__print_array(__entry->buf, 4, sizeof(unsigned int)) :
> 
> Note, "sizeof" will be shown in the format file that perf and trace-cmd
> read to parse this event. They currently do not know how to parse that
> (although I could add that in the future).
> 
> Since sizeof(unsigned int) is always 4 in Linux, just use 4.

Yes, I will make the aboves changes and send out V2 patch. Thank you for 
your time and comments.

Thomas

> 
> 			__print_array(__entry->buf, 4, 4)
> 
> -- Steve
> 
> 
>>> +			"Not available")
>>>   );
>>>   
>>>   /*
>>> -- 
>>> 2.14.1
>>>    
>