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From: David Howells <dhowells@redhat.com>
In-Reply-To: <1274135154-24082-3-git-send-email-walken@google.com>
References: <1274135154-24082-3-git-send-email-walken@google.com> <1274135154-24082-1-git-send-email-walken@google.com>
To: Michel Lespinasse <walken@google.com>
Cc: dhowells@redhat.com, Linus Torvalds <torvalds@linux-foundation.org>,
       Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Mike Waychison <mikew@google.com>,
       Suleiman Souhlal <suleiman@google.com>, Ying Han <yinghan@google.com>
Subject: Re: [PATCH 02/10] rwsem: fully separate code pathes to wake writers vs readers
Date: Wed, 19 May 2010 13:04:42 +0100
Message-ID: <2767.1274270682@redhat.com>
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Michel Lespinasse <walken@google.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