From: Greg KH <gregkh@suse.de>
To: Andy Whitcroft <apw@canonical.com>
Cc: linux-usb@vger.kernel.org,
Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] khubd -- switch USB product/manufacturer/serial handling to RCU
Date: Mon, 14 Jun 2010 09:29:19 -0700 [thread overview]
Message-ID: <20100614162919.GA13932@suse.de> (raw)
In-Reply-To: <1276514141-23725-1-git-send-email-apw@canonical.com>
On Mon, Jun 14, 2010 at 12:15:41PM +0100, Andy Whitcroft wrote:
> With the introduction of wireless USB hubs the product, manufacturer,
> and serial number are now mutable.
Changable by whom? The device itself? This has always been the case,
although it is usually very rare for a device to do this.
> This necessitates new locking in the gconsumers of these values
> including the sysfs read routines in order to prevent use-after-free
> acces to these values.
Who would access them after they go away?
> These extra locks create significant lock contention leading to
> increased boot times (0.3s for an example Atom based system).
Who is doing all of the deauthorization at boot time that this would
ever matter at all?
> Move update of these values to RCU based locking.
Ick. What has changed that necessitates this? You discuss a variety of
different things in this bug report:
> BugLink: http://bugs.launchpad.net/bugs/510937
Which would have been nice to dicuss with the people on these lists. I
really don't think this is the correct fix, as a normal boot path
shouldn't be having non-authorized usb devices, right? And from that
bug, once the machine is up and running, there is no contention here,
right?
not convinced,
greg k-h
next prev parent reply other threads:[~2010-06-14 16:29 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-14 11:15 [PATCH 1/1] khubd -- switch USB product/manufacturer/serial handling to RCU Andy Whitcroft
2010-06-14 16:29 ` Greg KH [this message]
2010-06-15 9:33 ` Andy Whitcroft
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