linux-kernel - Re: [PATCH] ring-buffer: Race when writing and swapping cpu buffer in parallel

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Date:	Thu, 26 Jun 2014 20:55:00 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ring-buffer: Race when writing and swapping cpu buffer
 in parallel

On Thu, 26 Jun 2014 09:58:31 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> What we can do is force ring_buffer_swap_cpu() to only work for the CPU
> that it is on. As we have snapshot in per_cpu buffers, to make that
> work, we will need to change the per_cpu version of snapshot to do a
> smp_call_function_single() to the CPU that it wants to take a snapshot
> of, and run the swap there.
> 
> To force this, we can remove the cpu parameter from the
> ring_buffer_swap_cpu(). By doing this, we may be able to remove some of
> the CONFIG_RING_BUFFER_ALLOW_SWAP hacks too!
> 
> I'm not going to sacrifice the general performance of the ring buffer
> for a feature that is seldom (if ever) used.

Did you want to do the above, or do you want me to write something up?

-- Steve
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