From: Jens Axboe <jens.axboe@oracle.com>
To: Nick Piggin <npiggin@suse.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [patch] shared tag queue barrier comment
Date: Fri, 14 Sep 2007 09:00:20 +0200 [thread overview]
Message-ID: <20070914070020.GU25592@kernel.dk> (raw)
In-Reply-To: <20070914064112.GA25277@wotan.suse.de>
On Fri, Sep 14 2007, Nick Piggin wrote:
>
> Should add some comments for the tag barriers (they won't be so important
> if we can switch over to the explicit _lock bitops, but for now we should
> make it clear).
Thanks!
> Jens' original patch said a barrier after the test_and_clear_bit was also
> required. I can't see why (and it would prevent the use of the _lock bitop).
Yeah, I don't think it's needed either. The important bit was ordering
the ->tag_index[tag] = NULL setting before clearing the bit, and as long
as those two operations are ordered, we are good to go. So the last
memory barrier was not needed.
--
Jens Axboe
prev parent reply other threads:[~2007-09-14 7:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-14 6:41 [patch] shared tag queue barrier comment Nick Piggin
2007-09-14 7:00 ` Jens Axboe [this message]
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