From: Matt Mackall <mpm@selenic.com>
To: "Theodore Ts'o" <tytso@mit.edu>,
Bernard Normier <bernard@zeroc.com>,
linux-kernel@vger.kernel.org
Subject: Re: Concurrent access to /dev/urandom
Date: Thu, 9 Dec 2004 13:29:36 -0800 [thread overview]
Message-ID: <20041209212936.GO8876@waste.org> (raw)
In-Reply-To: <20041209015705.GB6978@thunk.org>
On Wed, Dec 08, 2004 at 08:57:05PM -0500, Theodore Ts'o wrote:
> On Wed, Dec 08, 2004 at 01:56:14PM -0800, Matt Mackall wrote:
> >
> > Ted, I think this is a bit more straightforward than your patch, and
> > safer as it protects get_random_bytes() and internal extract_entropy()
> > users. And I'd be leery of your get_cpu() trick due to preempt
> > issues.
> >
>
> I'm concerned that turning off interrupts during even a single SHA-1
> transform will put us above the radar with respect to the preempt
> latency statistics again. We could use a separate spinlock that only
> pretects the mix_ptr and mixing access to the pool, so we're at least
> not disabling interrupts, but we still are holding a spinlock across a
> cryptographic operation.
It's been suggested to me that a sequence lock might be the right
approach to this, which I'll try to take a look at this evening. Also,
I'm going to time the lock hold time in my previous more conventional
patch and see what kind of neighborhood we're in.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2004-12-09 21:29 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-27 20:45 Concurrent access to /dev/urandom Bernard Normier
2004-11-27 20:56 ` Jan Engelhardt
2004-11-27 21:15 ` Bernard Normier
2004-11-27 21:22 ` Jan Engelhardt
2004-11-28 20:58 ` Bernard Normier
2004-12-07 23:41 ` Bernard Normier
2004-12-08 1:28 ` Theodore Ts'o
2004-12-08 1:56 ` Bernard Normier
2004-12-08 19:21 ` Theodore Ts'o
2004-12-08 20:15 ` Bernard Normier
2004-12-08 21:56 ` Matt Mackall
2004-12-09 1:57 ` Theodore Ts'o
2004-12-09 2:46 ` andyliu
2004-12-09 4:55 ` Matt Mackall
2004-12-09 2:58 ` Matt Mackall
2004-12-09 21:29 ` Matt Mackall [this message]
2004-12-10 4:47 ` Matt Mackall
2004-12-10 16:35 ` Theodore Ts'o
2004-12-10 18:28 ` Matt Mackall
2004-12-10 21:28 ` Theodore Ts'o
2004-12-10 22:23 ` Matt Mackall
2004-12-11 0:22 ` Adam Heath
2004-12-11 1:10 ` Matt Mackall
2004-12-11 17:33 ` Theodore Ts'o
2004-12-11 19:58 ` Adam Heath
2004-12-11 20:40 ` Matt Mackall
2004-12-12 16:19 ` Pavel Machek
2004-12-11 0:19 ` Adam Heath
2004-12-09 3:10 ` David Lang
2004-12-09 4:52 ` Matt Mackall
2004-12-09 6:36 ` Theodore Ts'o
2004-11-29 22:47 ` Jon Masters
2004-11-29 23:14 ` Bernard Normier
2004-11-29 23:43 ` Sven-Haegar Koch
2004-11-30 2:31 ` David Schwartz
2004-11-30 4:14 ` Kyle Moffett
2004-11-30 8:23 ` Jan Engelhardt
2004-11-30 18:50 ` David Schwartz
2004-11-29 23:42 ` David Wagner
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