linux-kernel - Re: [for-next][PATCH 08/12] tracing: Add binary & filter for events

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Message-ID: <51C349BD.4030403@broadcom.com>
Date:	Thu, 20 Jun 2013 20:28:13 +0200
From:	"Arend van Spriel" <arend@...adcom.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
cc:	linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...nel.org>,
	"Frederic Weisbecker" <fweisbec@...il.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [for-next][PATCH 08/12] tracing: Add binary & filter for
 events

On 06/20/13 14:14, Steven Rostedt wrote:
> On Thu, 2013-06-20 at 10:09 +0200, Arend van Spriel wrote:
>> On 06/20/2013 05:35 AM, Steven Rostedt wrote:
>>> By allowing a binary '&' operation, this gives the user the ability to
>>> test a bit.
>>>
>>> Note, a binary '|' is not added, as it doesn't make sense as fields must
>>> be compared to constants (for now), and ORing a constant will always return
>>> true.
>>>
>>> Link:http://lkml.kernel.org/r/1371057385.9844.261.camel@gandalf.local.home
>>>
>>> Suggested-by: Arend van Spriel<arend@...adcom.com>
>>
>> Actually, my attempt was triggered by the trace-cmd manual page:
>>
>> "-f filter
>> Specify a filter for the previous event. This must come after a -e. This
>> will filter what events get recorded based on the content of the event.
>> Filtering is passed to the kernel directly so what filtering is allowed
>> may depend on what version of the kernel you have. Basically, it will
>> let you use C notation to check if an event should be processed or not.
>>
>> ==,>=,<=,>,<,&, |,&&  and ||
>>
>> The above are usually safe to use to compare fields."
>
> Ah thanks. That needs to be updated. Not sure why I wrote all of them.
> Perhaps because the report side handles them and I just assumed the
> kernel did too.

Reading the whole text with your remark in mind, I guess it does 
indicate there are no guarantees depending on the kernel and the list of 
operators are what trace-cmd supports. I overlooked/ignored the text 
seeing the operators.

Regards,
Arend

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