Re: [PATCH v2 1/1] ftrace: do not update max buffer with no users

[Ingo Molnar]

* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> 
> On Thu, 13 Nov 2008, Ingo Molnar wrote:
> > 
> > the obvious solution is to add this to ring_buffer_resize():
> > 
> > 	if (!buffer)
> > 		return size;
> 
> Having a NULL buffer return a successful resize is a bit worrisome to me.
> 
> And looking at the code I was trying to make sure could never be called
> if there are no max_tr users:
> 
> in update_max_tr
> 
> 	buf = tr->buffer;
> 	tr->buffer = max_tr.buffer;
> 	max_tr.buffer = buf;
> 
> Should all the ring buffer API return success on NULL pointers?

well, update_max_tr() is only used from tracers which also actually 
allocate a max trace buffer: irqs/preemptoff, sched-wakeup.

So, can you tell me any way how the patch below could be broken?

	Ingo

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