Re: [PATCH 1/1] function tracing: fix wrong position computing ofstack_trace

[Steven Rostedt]

On Fri, 21 Nov 2008, Liming Wang wrote:

> Impact: make output of stack_trace complete if buffer overflow
> 
> When read buffer overflows, the output of stack_trace isn't complete.
> 
> When printing records with seq_printf in t_show, if the read buffer
> has overflowed by the current record, then this record won't be printed
> to user space through read buffer, it will just be dropped in this printing.
> 
> When next printing, t_start should return the "*pos"th record, which is the one
> dropped by previous printing, but it just returns (m->private + *pos)th record.
> 
> Here we use a more sane method to implement seq_operations which can be found
> in kernel code. Thus we needn't initialize m->private.
> 
> About testing, it's not easy to overflow read buffer, but we can use
> seq_printf to print more padding bytes in t_show, then it's easy to check
> whether or not records are lost.
> 
> This commit has been tested on both condition of overflow and non overflow.
> 
> Signed-off-by: Liming Wang <liming.wang@xxxxxxxxxxxxx>

Acked-by: Steven Rostedt <srostedt@xxxxxxxxxx>

-- Steve

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