On Tue, 2013-03-19 at 11:27 -0400, Alan Stern wrote: > On Tue, 19 Mar 2013, Ben Hutchings wrote: > > > On Mon, 2013-03-18 at 04:22 +0000, Ben Hutchings wrote: > > > 3.2-stable review patch. If anyone has any objections, please let me know. > > > > > > ------------------ > > > > > > From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > > > > > > commit feca7746d5d9e84b105a613b7f3b6ad00d327372 upstream. > > > > > > This patch (as1661) fixes a rather obscure bug in ehci-hcd. In a > > > couple of places, the driver compares the DMA address stored in a QH's > > > overlay region with the address of a particular qTD, in order to see > > > whether that qTD is the one currently being processed by the hardware. > > > (If it is then the status in the QH's overlay region is more > > > up-to-date than the status in the qTD, and if it isn't then the > > > overlay's value needs to be adjusted when the QH is added back to the > > > active schedule.) > > > > > > However, DMA address in the overlay region isn't always valid. It > > > sometimes will contain a stale value, which may happen by coincidence > > > to be equal to a qTD's DMA address. Instead of checking the DMA > > > address, we should check whether the overlay region is active and > > > valid. The patch tests the ACTIVE bit in the overlay, and clears this > > > bit when the overlay becomes invalid (which happens when the > > > currently-executing URB is unlinked). > > > > > > This is the second part of a fix for the regression reported at: > > > > > > https://bugs.launchpad.net/bugs/1088733 > > > > Alan, the first part (commit 6402c796d3b4 aka as1660) didn't apply and I > > couldn't see how to adapt it for 3.2. Does this second part have any > > value without the first? Or, if you could provide a backport of the > > first part, that would be very much appreciated. > > Without the first part, the second part can actually be dangerous. > Under the circumstances, I think it is best to apply neither. Thanks, I've dropped this. Ben. -- Ben Hutchings When you say `I wrote a program that crashed Windows', people just stare ... and say `Hey, I got those with the system, *for free*'. - Linus Torvalds
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