linux-kernel - Re: [PATCH 02/10] rwsem: fully separate code pathes to wake writers vs readers

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Message-ID: <2767.1274270682@redhat.com>
Date:	Wed, 19 May 2010 13:04:42 +0100
From:	David Howells <dhowells@...hat.com>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Waychison <mikew@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH 02/10] rwsem: fully separate code pathes to wake writers vs readers

Michel Lespinasse <walken@...gle.com> wrote:

> + readers_only:
> +	if (!downgrading) {
> +

There's an unnecessary blank line here.

> +		/* if we came through an up_xxxx() call, we only only wake
> +		 * someone up if we can transition the active part of the
> +		 * count from 0 -> 1
> +		 */
> + try_again_read:

I hate code that jumps into braced blocks with goto.  Would it be possible for
you to do:

	readers_only:
		if (downgrading)
			goto wake_readers;
	...
	wake_readers:
		/* Grant an infinite number of read locks to the readers at the front
	...

instead, please?

Also, since the labels 'undo' and 'try_again' are now specific to the writer
path, can you label them 'undo_write' and 'try_again_write' just to make it
obvious?

Other than that, no particular objections to this patch.

David
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