RE: [RFC] xHCI: synchronize interrupts in xhci_suspend()

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> -----Original Message-----
> From: Sarah Sharp [mailto:sarah.a.sharp@xxxxxxxxxxxxxxx]
> Sent: Wednesday, December 15, 2010 8:24 AM
> To: Xu, Andiry
> Cc: linux-usb@xxxxxxxxxxxxxxx; Matthew Garrett; Alan Stern
> Subject: Re: [RFC] xHCI: synchronize interrupts in xhci_suspend()
> 
> On Mon, Dec 06, 2010 at 06:22:19PM +0800, Andiry Xu wrote:
> > Matthew,
> >
> > Can you help to test if this patch fix your xhci suspend and remove
> issue? Thanks.
> 
> Andiry,
> 
> This code doesn't change the code in the USB core that synchronizes
the
> legacy PCI interrupts.  So if you have to fall back to MSI, then
> pci_dev->irq is equal to your MSI irq, and suspend_common() will
> synchronize the irq a second time after xhci_suspend() is called.
Maybe
> suspend_common() should only call synchronize_irq() if pci_dev->irq is
> the same as hcd->irq?
> 

Well, I think synchronize_irq()is fine to be called twice. But perhaps
you are right, it's pointless to call it for a second time.

Does the hcd->irq equal check in suspend_common() affect other HCDs? I
think it's OK but I'm not sure. Is there any reason other HCDs do not
use MSI-X and MSI?

> Also, what happens if you free the legacy IRQ, set up MSI-X, and then
> the USB core tries to synchronize pci_dev->irq?  Is pci_dev->irq still
> set to the legacy IRQ that the driver freed?  If so, we're possibly
> synchronizing someone else's IRQ.
> 

Yes, that's possible. Here are the modifications:

1. Set hcd->irq = pdev->irq in xhci driver when using MSI;
2. Synchronize irq in xhci_suspend() only when using MSI-X;
3. Synchronize irq only if pci_dev->irq is equal to hcd->irq in
suspend_common().

And then MSI-X synchronization will be handled by xhci_suspend(), and
MSI and INTx will be synchronized in suspend_common(). Is this solution
feasible?

Thanks,
Andiry


 
> > From: Andiry Xu <andiry.xu@xxxxxxx>
> > Date: Mon, 6 Dec 2010 16:58:16 +0800
> > Subject: [PATCH] xHCI: synchronize interrupts in xhci_suspend()
> >
> > Matthew Garrett reports a interrupt double free in xHCI code when
the
> > host is suspended and then the card removed.
> >
> > Synchronize the interrupts instead of free them in xhci_suspned().
> >
> > Reported-by: Matthew Garrett <mjg@xxxxxxxxxx>
> > Signed-off-by: Andiry Xu <andiry.xu@xxxxxxx>
> > ---
> >  drivers/usb/host/xhci.c |   37
+++++++++----------------------------
> >  1 files changed, 9 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index 45e4a31..41a9225 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -646,7 +646,9 @@ int xhci_suspend(struct xhci_hcd *xhci)
> >  {
> >  	int			rc = 0;
> >  	struct usb_hcd		*hcd = xhci_to_hcd(xhci);
> > +	struct pci_dev		*pdev =
to_pci_dev(hcd->self.controller);
> >  	u32			command;
> > +	int			i;
> >
> >  	spin_lock_irq(&xhci->lock);
> >  	clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
> > @@ -678,9 +680,14 @@ int xhci_suspend(struct xhci_hcd *xhci)
> >  		return -ETIMEDOUT;
> >  	}
> >  	/* step 5: remove core well power */
> > -	xhci_cleanup_msix(xhci);
> >  	spin_unlock_irq(&xhci->lock);
> >
> > +	if (xhci->msix_entries) {
> > +		for (i = 0; i < xhci->msix_count; i++)
> > +			synchronize_irq(xhci->msix_entries[i].vector);
> > +	} else if (pdev->irq >= 0)
> > +		synchronize_irq(pdev->irq);
> > +
> >  	return rc;
> >  }
> >
> > @@ -694,7 +701,6 @@ int xhci_resume(struct xhci_hcd *xhci, bool
> hibernated)
> >  {
> >  	u32			command, temp = 0;
> >  	struct usb_hcd		*hcd = xhci_to_hcd(xhci);
> > -	struct pci_dev		*pdev =
to_pci_dev(hcd->self.controller);
> >  	int	old_state, retval;
> >
> >  	old_state = hcd->state;
> > @@ -729,8 +735,7 @@ int xhci_resume(struct xhci_hcd *xhci, bool
> hibernated)
> >  		xhci_dbg(xhci, "Stop HCD\n");
> >  		xhci_halt(xhci);
> >  		xhci_reset(xhci);
> > -		if (hibernated)
> > -			xhci_cleanup_msix(xhci);
> > +		xhci_cleanup_msix(xhci);
> >  		spin_unlock_irq(&xhci->lock);
> >
> >  #ifdef CONFIG_USB_XHCI_HCD_DEBUGGING
> > @@ -765,30 +770,6 @@ int xhci_resume(struct xhci_hcd *xhci, bool
> hibernated)
> >  		return retval;
> >  	}
> >
> > -	spin_unlock_irq(&xhci->lock);
> > -	/* Re-setup MSI-X */
> > -	if (hcd->irq)
> > -		free_irq(hcd->irq, hcd);
> > -	hcd->irq = -1;
> > -
> > -	retval = xhci_setup_msix(xhci);
> > -	if (retval)
> > -		/* fall back to msi*/
> > -		retval = xhci_setup_msi(xhci);
> > -
> > -	if (retval) {
> > -		/* fall back to legacy interrupt*/
> > -		retval = request_irq(pdev->irq, &usb_hcd_irq,
IRQF_SHARED,
> > -					hcd->irq_descr, hcd);
> > -		if (retval) {
> > -			xhci_err(xhci, "request interrupt %d failed\n",
> > -					pdev->irq);
> > -			return retval;
> > -		}
> > -		hcd->irq = pdev->irq;
> > -	}
> > -
> > -	spin_lock_irq(&xhci->lock);
> >  	/* step 4: set Run/Stop bit */
> >  	command = xhci_readl(xhci, &xhci->op_regs->command);
> >  	command |= CMD_RUN;
> > --
> > 1.7.0.4
> >
> >
> >


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