Date: Thu, 20 Aug 2015 16:05:18 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Dean Nelson <dnelson@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, a.p.zijlstra@chello.org,
        mingo@redhat.com, namhyung@kernel.org, linux-kernel@vger.kernel.org,
        jolsa@kernel.org
Subject: Re: [PATCH v3] tools lib traceevent: add checks for returned
 EVENT_ERROR type
Message-ID: <20150820190518.GA3154@kernel.org>
References: <20150820151632.13927.13791.email-sent-by-dnelson@teal>
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 <55D614C9.8080503@redhat.com>
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Em Thu, Aug 20, 2015 at 12:56:25PM -0500, Dean Nelson escreveu:
> On 08/20/2015 12:05 PM, Steven Rostedt wrote:
> >On Thu, 20 Aug 2015 11:16:32 -0400
> >Dean Nelson <dnelson@redhat.com> wrote:
> >
> >>Running the following perf-stat command on an arm64 system produces the
> >>following result...
> >>
> >>   [root@aarch64 ~]# perf stat -e kmem:mm_page_alloc -a sleep 1
> >>     Warning: [kmem:mm_page_alloc] function sizeof not defined
> >>     Warning: Error: expected type 4 but read 0
> >>   Segmentation fault
> >>   [root@aarch64 ~]#
> >>
> >>The second warning message and SIGSEGV stem from the issue expressed in the
> >>first warning message, and are the result of ignoring the EVENT_ERROR type
> >>returned back through the call chain.
> >>
> >>Dealing with the first warning message is beyond the scope of this patch. But
> >>the second warning is addressed by this patch's first hunk. And the SIGSEGV is
> >>eliminated by its second hunk.
> >
> >Patch looks fine, but this change log is lacking. I don't think you
> >need to resend though. But Arnaldo, can you add more to this change log
> >to describe the following, and that's only if I got it right ;-) If I
> >didn't get it right, then the change log definitely needs to be
> >explained better.
> 
> No you definitely got it right.
> 
> I thought that was what I was saying by the paragraph beginning with
> "The second warning...", with the notion that the 2nd warning and
> SIGSEGV "stem from" the 1st warning. And that the latter two issues "are
> the result of ignoring the EVENT_ERROR" encountered by the 1st
> warning's issue.
> 
> At least that is what that paragraph was intended to be all about.
> Obviously I failed to communicate.
> 
> Yours is clear to me. So why not just replace my poorly done paragraph
> with your good  paragraph...
> 
> 
> >====
> >The second warning was a result of the first warning not stopping
> >processing after it detected the issue. That is, code that found the
> >issue reported the first problem, but because it did not exit out of
> >the functions smoothly, it caused the other warning to appear and not
> >only that, it later caused the SIGSEGV.
> >====
> 
> Thanks for the review.

Ok, so I'll use Steven's text and will stick a Reviewed-by: Steven, ack?

- Arnaldo
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