linux-kernel - Re: [linux-usb-devel] [PATCH] msleep() with hrtimers

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Date:	Thu, 9 Aug 2007 11:08:03 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Jonathan Corbet <corbet@....net>,
	<Ingo@...-sf-spam2.sourceforge.net>,
	<linux-usb-devel@...ts.sourceforge.net>,
	Roman Zippel <zippel@...ux-m68k.org>,
	<linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>, Molnar <mingo@...e.hu>
Subject: Re: [linux-usb-devel] [PATCH] msleep() with hrtimers

On Thu, 9 Aug 2007, Andrew Morton wrote:

> This failed the Vaio test.  I guess it triggered a USB bug.
> 
> With this patch applied, when I hotplug my wireless mouse, the little LED
> on the mouse comes on for a second or so then goes out and no pointy clicky
> for me.
> 
> It says:
> 
> [  152.481522] usb 1-1: new low speed USB device using uhci_hcd and address 2
> 
> 
> Without this patch applied, I get
> 
> [  195.935445] usb 2-1: new low speed USB device using uhci_hcd and address 2
> [  196.116183] usb 2-1: configuration #1 chosen from 1 choice
> [  196.198362] input: Microsoft Microsoft Wireless Optical Mouse 1.00 as /class/input/input7
> [  196.223724] input: USB HID v1.11 Mouse [Microsoft Microsoft Wireless Optical Mouse 1.00] on usb-0000:00:1d.1-1
> [  196.224570] usb 2-1: new device found, idVendor=045e, idProduct=00e1
> [  196.224579] usb 2-1: new device strings: Mfr=1, Product=2, SerialNumber=0
> [  196.224585] usb 2-1: Product: Microsoft Wireless Optical Mouse 1.00
> [  196.224590] usb 2-1: Manufacturer: Microsoft
> 
> and lots of pointy clickiness.
> 
> I would assume that there is some msleep() in USB which is too short, and
> the present wild rounding-up which msleep() does covered up the
> incorrectly-chosen sleep duration.
> 
> I'm using HZ=250 (http://userweb.kernel.org/~akpm/config-sony.txt) and it
> could well be that the mouse would fail just by going to HZ=1000, but I
> didn't bother testing that.
> 
> Could one of the USB developers please suggest which msleep()(s) I should
> start looking at?

It could be one of the calls in drivers/usb/core/hub.c, however almost 
all of them are at least 10 ms already.  There's a 0-ms msleep near the 
start of hub_port_wait_reset() which might cause problems.

It will be easier to pin down the culprit if you turn on 
CONFIG_USB_DEBUG.

Alan Stern

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