linux-kernel - Re: [PATCH 1/1] ftrace: fix wrong pos computing when read buffer has been fulfilled.

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Date:	Sun, 16 Nov 2008 10:01:46 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	walimis <walimisdev@...il.com>, linux-kernel@...r.kernel.org,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 1/1] ftrace: fix wrong pos computing when read buffer
 has been fulfilled.


On Sun, 16 Nov 2008, Ingo Molnar wrote:
> * walimis <walimisdev@...il.com> wrote:
> 
> > hi Steven,
> > 
> > Could you help me to review this patch?
> > 
> > Thanks.
> > 
> > Impact: make output of available_filter_functions complete
> > 
> > phenomenon:
> > 
> > The first value of dyn_ftrace_total_info is not equal with
> > `cat available_filter_functions | wc -l`, but they should be equal.
> > 
> > root cause:
> > 
> > When printing functions with seq_printf in t_show, if the read 
> > buffer is just overflowed by current function record, then this 
> > function won't be printed to user space through read buffer, it will 
> > just be dropped. So we can't see this function printing. So, every 
> > time the last function to fill the read buffer, if overflowed, will 
> > be dropped. This also applies to set_ftrace_filter if 
> > set_ftrace_filter has more bytes than read buffer.
> > 
> > fix:
> > 
> > Through checking return value of seq_printf, if less than 0, we know 
> > this function doesn't be printed. Then we decrease position to force 
> > this function to be printed next time, in next read buffer.
> > 
> > another little fix is to show correct allocating pages count.
> > 
> > Signed-off-by: walimis <walimisdev@...il.com>
> > ---
> >  kernel/trace/ftrace.c |   26 +++++++++++++++-----------
> >  1 files changed, 15 insertions(+), 11 deletions(-)
> 
> looks sane - applied to tip/tracing/urgent. Steve, any objections?

I'm actually still reviewing it. I was busy with the PPC work, so I did 
not finish my review. Weekends are family time, so my activity now is 
minimal. Pull it in, and if I find any problems with it, I'll just submit 
a patch on top, or have walimis fix it ;-)

-- Steve

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