linux-kernel - Re: [PATCH] usb: add Freescale QE/CPM USB peripheral controller driver

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Date:	Mon, 1 Sep 2008 20:34:53 +0400
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Li Yang <leoli@...escale.com>
Cc:	greg@...ah.com, linux-usb@...r.kernel.org,
	dbrownell@...rs.sourceforge.net, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org, Robert Jarzmik <rjarzmik@...e.fr>
Subject: Re: [PATCH] usb: add Freescale QE/CPM USB peripheral controller
	driver

On Thu, Aug 28, 2008 at 05:43:33PM +0800, Li Yang wrote:
> Some of Freescale SoC chips have a QE or CPM co-processor which
> supports full speed USB.  The driver adds device mode support
> of both QE and CPM USB controller to Linux USB gadget.  The
> driver is tested with MPC8360 and MPC8272, and should work with
> other models having QE/CPM given minor tweaks.
> 
> Signed-off-by: Xie Xiaobo <X.Xie@...escale.com>
> Signed-off-by: Li Yang <leoli@...escale.com>
> ---

Just found a recursive locking bug:

[...]
> +static int reset_queues(struct qe_udc *udc)
> +{

Note: this function is called from the IRQ, the IRQ handler
grabs udc->lock spinlock..

> +	u8 pipe;
> +
> +	for (pipe = 0; pipe < USB_MAX_ENDPOINTS; pipe++)
> +		udc_reset_ep_queue(udc, pipe);
> +
> +	/* report disconnect; the driver is already quiesced */
> +	udc->driver->disconnect(&udc->gadget);

In the disconnect(), g_ether driver will immediately call
qe_ep_disable() function which will try to grab &udc->lock
spinlock once again..

Not sure how to fix this properly... :-/

p.s. the same bug exists in omap_udc.c, pxa27x_udc.c and probably
other drivers as well... The only reason why it does not exploit
in most cases is that the spin_lock_irqsave for !SMP case turns
into simple local_irq_save().

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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