From: Steven Rostedt <srostedt@redhat.com>
Date: Wed, 6 May 2009 01:16:11 +0000 (-0400)
Subject: ring-buffer: move big if statement down
X-Git-Tag: v2.6.31-rc1~401^2~84
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aa20ae8444fc6c318272c643f856d8d8ad3e198d;p=pandora-kernel.git

ring-buffer: move big if statement down

In the hot path of the ring buffer "__rb_reserve_next" there's a big
if statement that does not even return back to the work flow.

	code;

	if (cross to next page) {

		[ lots of code ]

		return;
	}

	more code;

The condition is even the unlikely path, although we do not denote it
with an unlikely because gcc is fine with it. The condition is true when
the write crosses a page boundary, and we need to start at a new page.

Having this if statement makes it hard to read, but calling another
function to do the work is also not appropriate, because we are using a lot
of variables that were set before the if statement, and we do not want to
send them as parameters.

This patch changes it to a goto:

	code;

	if (cross to next page)
		goto next_page;

	more code;

	return;

next_page:

	[ lots of code]

This makes the code easier to understand, and a bit more obvious.

The output from gcc is practically identical. For some reason, gcc decided
to use different registers when I switched it to a goto. But other than that,
the logic is the same.

[ Impact: easier to read code ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

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