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

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Message-ID: <20081116073354.GF19646@elte.hu>
Date:	Sun, 16 Nov 2008 08:33:54 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	walimis <walimisdev@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, 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.


* 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?

	Ingo
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