From: Al Viro <viro@ZenIV.linux.org.uk>
To: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Simon Kirby <sim@hostway.ca>, Ian Applegate <ia@cloudflare.com>,
Christoph Lameter <cl@gentwo.org>,
Pekka Enberg <penberg@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Chris Mason <chris.mason@fusionio.com>
Subject: Re: Found it! (was Re: [3.10] Oopses in kmem_cache_allocate() via prepare_creds())
Date: Mon, 2 Dec 2013 16:46:01 +0000 [thread overview]
Message-ID: <20131202164601.GF10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20131202162755.GB27781@gmail.com>
On Mon, Dec 02, 2013 at 05:27:55PM +0100, Ingo Molnar wrote:
> It's not like there should be many (any?) VFS operations where a pipe
> is used via i_mutex and pipe->mutex in parallel, which would improve
> scalability - so I don't see the scalability advantage. (But I might
> be missing something)
>
> Barring such kind of workload the extra mutex just adds extra
> micro-costs because now two locks have to be taken on
> creation/destruction, plus it adds extra complexity and races.
>
> So unless I'm missing something obvious, another good fix would be to
> just revert pipe->mutex and rely on i_mutex as before?
You are missing the extra shitloads of complexity in ->i_mutex ordering,
and ->i_mutex is already used for too many things...
next prev parent reply other threads:[~2013-12-02 16:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-02 16:00 Found it! (was Re: [3.10] Oopses in kmem_cache_allocate() via prepare_creds()) Linus Torvalds
2013-12-02 16:27 ` Ingo Molnar
2013-12-02 16:46 ` Al Viro [this message]
2013-12-02 17:05 ` Ingo Molnar
2013-12-02 17:06 ` Al Viro
2013-12-03 2:58 ` Linus Torvalds
2013-12-03 4:28 ` Al Viro
2013-12-05 8:12 ` gfs2 deadlock (was Re: Found it) Al Viro
2013-12-05 10:19 ` Steven Whitehouse
2013-12-03 8:52 ` [PATCH] mutexes: Add CONFIG_DEBUG_MUTEX_FASTPATH=y debug variant to debug SMP races Ingo Molnar
2013-12-03 18:10 ` Linus Torvalds
2013-12-04 9:19 ` Simon Kirby
2013-12-04 21:14 ` Linus Torvalds
2013-12-05 8:06 ` Simon Kirby
2013-12-05 6:57 ` Simon Kirby
2013-12-11 15:03 ` Waiman Long
-- strict thread matches above, loose matches on Subject: below --
2025-10-07 4:03 Found it! (was Re: [3.10] Oopses in kmem_cache_allocate() via prepare_creds()) Steven Paul Jobs
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