Re: [PATCH] USB: fix deadlock in HCD code

From: Alan Stern
Date: Wed May 21 2008 - 10:42:18 EST

On Wed, 21 May 2008, David Vrabel wrote:

> Alan Stern wrote:
> >
> > The functions you are worried about (usb_hcd_link_urb_to_ep and
> > usb_hcd_unlink_urb_from_ep) are documented as requiring that interrupts
> > be disabled by their callers. This patch isn't needed.
> This requirement is the only reason the whci-hcd driver disables
> interrupts. Removing this requirement would reduce the time that
> interrupts are disabled in the whci-hcd driver.

That doesn't sound like a valid approach. If you don't disable
interrupts then you aren't protected against an interrupt handler
submitting an URB and accessing your data structures while whci-hcd is
in the middle of updating them.

Alan Stern

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