linux-kernel - Re: [PATCH] trace-cmd: fix length calculation for padding events

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Message-ID: <CAJL_eksfxza82jy62NUPmZGtQ77LVuHk+RnN3F95s-hSaSpK2w@mail.gmail.com>
Date:	Fri, 27 Jan 2012 11:21:18 -0800
From:	David Sharp <dhsharp@...gle.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, mrubin@...gle.com, chavey@...gle.com,
	Gregory Haskins <gregory.haskins@...il.com>
Subject: Re: [PATCH] trace-cmd: fix length calculation for padding events

On Thu, Jan 26, 2012 at 7:44 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Thu, 2012-01-26 at 19:00 -0800, David Sharp wrote:
>> Padding events store size in bytes, not words. Usually this ends up pushing
>> the parser off the current page, but occasionally not, and when not,
>> it ends up desynchronizing the parser from the event stream. This would
>> manifest as a lot of "ug!" messages from trace-cmd, and kernelshark
>> crashing before displaying the UI.
>>
>
> Nice! Funny, Gregory (Cc'd) sent me a trace.dat file that exhibited this
> behavior. I was going to look into it tomorrow. I tried it with this
> patch and it makes the bug go away.
>
> Nice catch!  I wonder how long this has been around without notice?
> Probably from day one.

Yeah, I think so. It's an easy mistake to make, because it's
incongruent with the rest of the event types.

>
> -- Steve
>
>> Signed-off-by: David Sharp <dhsharp@...gle.com>
>> ---
>>  trace-input.c |    1 -
>>  1 files changed, 0 insertions(+), 1 deletions(-)
>>
>> diff --git a/trace-input.c b/trace-input.c
>> index e3157a7..b6af1e6 100644
>> --- a/trace-input.c
>> +++ b/trace-input.c
>> @@ -1458,7 +1458,6 @@ translate_data(struct pevent *pevent,
>>       switch (type_len) {
>>       case RINGBUF_TYPE_PADDING:
>>               *length = data2host4(pevent, *ptr);
>> -             *length *= 4;
>>               *ptr += *length;
>>               break;
>>
>
>
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