Messages in this thread Patch in this message | | | From | David Brownell <> | Subject | Re: USB OOPS 2.6.25-rc2-git1 | Date | Wed, 20 Feb 2008 13:56:28 -0800 |
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On Wednesday 20 February 2008, Alan Stern wrote: > > ehci_hcd 0000:00:1d.7: IAA watchdog, lost IAA: status 8029 cmd 10021 > > lines in the log brings up some ideas that have been percolating in my > mind for a while. They have to do with the possibility of a race > between the watchdog routine and assertion of IAA.
The curious bit IMO being STS_INT (0001), which should also have triggered an IRQ. Suggesting to me that the race might be lower level than that ... at the level of a conflict between the various mechanisms to ack irqs.
See the appended patch (Andre, this is the additional one I meant) for a tweak at that level.
> In fact, if the timing comes out just wrong then it's possible (on SMP > systems) for an IAA interrupt to arrive when the watchdog > routine has already started running. Then end_unlink_async() might get > called right at the start of a new IAA cycle, or when the reclaim list > is empty.
The driver's spinlock should prevent that particular problem from appearing.
- Dave
========= CUT HERE Modify EHCI irq handling on the theory that at least some of the "lost" IRQs are caused by goofage between multiple lowlevel IRQ acking mechanisms: try rescanning before we exit the handler, in case the EHCI-internal ack (by clearing the irq status) doesn't always suffice for IRQs triggered nearly back-to-back.
--- drivers/usb/host/ehci-hcd.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- g26.orig/drivers/usb/host/ehci-hcd.c 2008-02-20 13:26:00.000000000 -0800 +++ g26/drivers/usb/host/ehci-hcd.c 2008-02-20 13:54:37.000000000 -0800 @@ -638,6 +638,8 @@ static irqreturn_t ehci_irq (struct usb_ return IRQ_NONE; } +retrigger: + /* clear (just) interrupts */ ehci_writel(ehci, status, &ehci->regs->status); cmd = ehci_readl(ehci, &ehci->regs->command); @@ -725,6 +727,12 @@ dead: if (bh) ehci_work (ehci); + + status = ehci_readl(ehci, &ehci->regs->status); + status &= INTR_MASK; + if (status) + goto retrigger; + spin_unlock (&ehci->lock); if (pcd_status & STS_PCD) usb_hcd_poll_rh_status(hcd); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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