linux-kernel - Re: [PATCH] perf: fix ring_buffer perf_output

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Message-ID: <1363611569.22553.10.camel@laptop>
Date:	Mon, 18 Mar 2013 13:59:29 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, jolsa@...hat.com,
	fweisbec@...il.com
Subject: Re: [PATCH] perf: fix ring_buffer perf_output_space() boundary
 calculation

On Mon, 2013-03-18 at 13:48 +0100, Stephane Eranian wrote:
>         if (!rb->writable)
> -               return true;
> +               return false;


writable means user writable (VM_WRITE); the difference is that a
!VM_WRITE buffer will simply over-write its own tail whereas a VM_WRITE
buffer will drop events.

So returning true for !VM_WRITE makes sense, there's always space.

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