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Commit 23d10a9e authored by Takamasa Ohtake's avatar Takamasa Ohtake Committed by Greg Kroah-Hartman
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USB: ohci handles hardware faults during root port resets 



I have found a problem where the root_port_reset() goes into an infinite
loop and stalls the kernel.

This happens when a hardware fault inside the machine occurs during a small
timing window.  In case of USB device connection, if a USB device responds to
hcd_submit_urb(), and later the controller fails before root_port_reset(),
root_port_reset() will loop infinitely because ohci_readl() will always
return "-1".  Such a failure can include ejecting a CardBus OHCI controller.

The probability of this problem is low, but it will increase if PnP type
usage is frequent.  The attached patch can solve this problem and I believe
that it is better to fix this problem.

Signed-off-by: default avatarTakamasa Ohtake <ohtake-txa@necst.nec.co.jp>
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent ee269d98

drivers/usb/host/ohci-hub.c

+7 −2
Original line number Diff line number Diff line
@@ -555,7 +555,7 @@ static void start_hnp(struct ohci_hcd *ohci); 
#define tick_before(t1,t2) ((s16)(((s16)(t1))-((s16)(t2))) < 0)



/* called from some task, normally khubd */

static inline void root_port_reset (struct ohci_hcd *ohci, unsigned port)

static inline int root_port_reset (struct ohci_hcd *ohci, unsigned port)

{

	__hc32 __iomem *portstat = &ohci->regs->roothub.portstatus [port];

	u32	temp;
@@ -570,6 +570,9 @@ static inline void root_port_reset (struct ohci_hcd *ohci, unsigned port) 
		/* spin until any current reset finishes */

		for (;;) {

			temp = ohci_readl (ohci, portstat);

			/* handle e.g. CardBus eject */

			if (temp == ~(u32)0)

				return -ESHUTDOWN;

			if (!(temp & RH_PS_PRS))

				break;

			udelay (500);
@@ -586,6 +589,8 @@ static inline void root_port_reset (struct ohci_hcd *ohci, unsigned port) 
		now = ohci_readl(ohci, &ohci->regs->fmnumber);

	} while (tick_before(now, reset_done));

	/* caller synchronizes using PRSC */



	return 0;

}



static int ohci_hub_control (
@@ -702,7 +707,7 @@ static int ohci_hub_control ( 
				&ohci->regs->roothub.portstatus [wIndex]);

			break;

		case USB_PORT_FEAT_RESET:

			root_port_reset (ohci, wIndex);

			retval = root_port_reset (ohci, wIndex);

			break;

		default:

			goto error;