linux-kernel - Re: [PATCH 17/17] mm: filemap: Avoid unnecessary barries and waitqueue lookup in unlock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 6 May 2014 22:30:06 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Vlastimil Babka <vbabka@...e.cz>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 17/17] mm: filemap: Avoid unnecessary barries and
 waitqueue lookup in unlock_page fastpath

On Thu, May 01, 2014 at 09:44:48AM +0100, Mel Gorman wrote:
> +/*
> + * If PageWaiters was found to be set at unlock time, __wake_page_waiters
> + * should be called to actually perform the wakeup of waiters.
> + */
> +static inline void __wake_page_waiters(struct page *page)
> +{
> +	ClearPageWaiters(page);

-ENOCOMMENT

barriers should always come with a comment that explain the memory
ordering and reference the pairing barrier.

Also, FWIW, there's a mass rename queued for .16 that'll make this:

  smp_mb__after_atomic();

but for now it will also still provide the old names with a __deprecated
tag on, so no real harm.

> +	smp_mb__after_clear_bit();
> +	wake_up_page(page, PG_locked);
> +}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/