linux-kernel - Re: Bug with USB proc

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Message-ID: <20060803062903.GA19176@1wt.eu>
Date:	Thu, 3 Aug 2006 08:29:03 +0200
From:	Willy Tarreau <w@....eu>
To:	Pete Zaitcev <zaitcev@...hat.com>
Cc:	benjamin.cherian.kernel@...il.com, linux-kernel@...r.kernel.org,
	linux-usb-devel@...ts.sourceforge.net
Subject: Re: Bug with USB proc_bulk in 2.4 kernel

On Wed, Aug 02, 2006 at 11:00:58PM -0700, Pete Zaitcev wrote:
> Replace the semaphore exclusive_access with an open-coded lock for
> the special use. The lock can be taken for: read, write, and both.
> This way, two bulk URBs can be submitted simultaneously with ioctl
> USBDEVFS_BULK: one read and one write. Such access was possible
> before 2.4.28.
> 
> Signed-off-By: Pete Zaitcev <zaitcev@...hat.com>
> 
> ---
> 
> The semaphore was introduced in 2.4.28 for the purpose of exclusion
> between access from device.c (cat /proc/bus/usb/devices), devio.c
> through libusb, and in-kernel driver. Currently, only usb-storage
> observes the locking protocol. The most popular device which locks
> in case of simultaneous access is TEAC CD-210PU.

Perfect. Patch queued, thanks Pete.

Willy

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